Skip to main content
NCBI home page
Frontiers in Microbiology logoLink to Frontiers in Microbiology
. 2015 Oct 20;6:1160. doi: 10.3389/fmicb.2015.01160

An assessment on DNA microarray and sequence-based methods for the characterization of methicillin-susceptible Staphylococcus aureus from Nigeria

Adebayo O Shittu 1,2,*, Omotayo Oyedara 3, Kenneth Okon 4, Adeola Raji 5, Georg Peters 6, Lutz von Müller 2,†, Frieder Schaumburg 6, Mathias Herrmann 2, Ulla Ruffing 2
PMCID: PMC4612102  PMID: 26539185

Abstract

Staphylococcus aureus is an important human pathogen causing nosocomial and community-acquired infections worldwide. In the characterization of this opportunistic pathogen, DNA microarray hybridization technique is used as an alternative to sequence based genotyping to obtain a comprehensive assessment on the virulence, resistance determinants, and population structure. The objective of this study was to characterize a defined collection of S. aureus isolates from Nigeria using the microarray technique, and to assess the extent that it correlates with sequence-based genotyping methods. The clonal diversity and genomic content of 52 methicillin-susceptible Staphylococcus aureus (MSSA) were investigated by spa typing, MLST and DNA microarray hybridization. More than half (55.8%) of these isolates were associated with clonal complexes (CCs) typically associated with methicillin-resistant S. aureus (MRSA) clones i.e., CC1, CC5, CC8, CC30, and CC45. Certain genes linked with virulence (hlgA and clfA) and adherence (ebpS, fnbA, sspA, sspB, and sspP) were detected in all isolates. A number of genes or gene clusters were associated with distinct clonal types. The enterotoxin gene cluster (egc) was linked with CC5, CC25, CC30, CC45, and CC121, enterotoxin H gene (seh) with CC1, exfoliative toxin D gene (etd) with CC25 and CC80, and the epidermal cell differentiation inhibitor B gene (edinB) with CC25, CC80, and CC152. The excellent agreement between data from DNA microarray and MLST in the delineation of Nigerian MSSA isolates indicates that the microarray technique is a useful tool to provide information on antibiotic resistance, clonal diversity and virulence factors associated with infection and disease.

Keywords: Staphylococcus aureus, microarray, MLST, genotyping, Nigeria

Introduction

Staphylococcus aureus is implicated in a variety of human infections with high rates of morbidity and mortality (Lowy, 1998; Corey, 2009). In infection, S. aureus exhibits a coordinated and regulated expression for a wide variety of cell and surface-associated virulence factors (Foster and Höök, 1998; Novick, 2006). These factors mediate adherence to host cells and damaged tissue, facilitate tissue destruction and spreading, promote iron uptake and evasion of host immune system, as well as tissue damage (Skaar and Schneewind, 2004; Grumann et al., 2014). Recent studies in Cameroon (Kihla et al., 2014), Egypt (Ahmed et al., 2014), Gabon (Alabi et al., 2013), Nigeria (Jido and Garba, 2012; Oladeinde et al., 2013), South Africa (Groome et al., 2012; Naidoo et al., 2013), and Tanzania (Kayange et al., 2010; Mhada et al., 2012) have identified S. aureus as the main etiological agent for various infections in Africa. Moreover, this species has been recognized as one main cause of community-acquired neonatal sepsis in Africa (Waters et al., 2011). These studies clearly establish the important role of this major human pathogen in tropical Africa.

In many health care institutions in sub-Saharan Africa, the lack of skilled laboratory manpower and resources is a major constraint in the identification of bacterial pathogens from clinical samples. If such analysis can be provided at all, identification of S. aureus typically relies on phenotypic methods precluding in-depth strain characterization. Molecular analysis of clonal attribution and presence of single genes contained in S. aureus isolates have emerged in pilot studies from select African centers, areas and populations (Ateba Ngoa et al., 2012; Shittu et al., 2012; Seni et al., 2013; Aiken et al., 2014; Egyir et al., 2014; Oosthuysen et al., 2014; Conceição et al., 2015; De Boeck et al., 2015; Kraef et al., 2015; Schaumburg et al., 2015). Nevertheless, in view of the impact of S. aureus disease in sub-Saharan Africa, the clonal characterization in concert with a comprehensive analysis of the hitherto ill-described virulence factor armamentarium of S. aureus isolates from this region is urgently warranted. Such analyses should target a broad spectrum of variable staphylococcal factors such as genes or gene clusters conferring antibiotic resistance, toxins, virulence, adhesion or immune evasion factors. These analyses have not been performed on a collection of S. aureus isolates in Nigeria, and reports from African countries are limited and only addressed a limited and select analytical spectrum (Raji et al., 2013; Aiken et al., 2014; Rovira et al., 2015).

The DNA microarray used for this analysis is a unique and comprehensive genotyping technique based on the analysis of 334 target sequences corresponding to approximately 170 distinct genes and their allelic variants. It enables the simultaneous identification of various gene classes including species markers, genes encoding resistance and virulence properties, exotoxin and adhesion factors, accessory gene regulator (agr), capsule, and SCCmec types (Monecke et al., 2011). Based on the observation of a high level of genetic diversity from previous investigations on methicillin-susceptible S. aureus (MSSA) in Nigeria (Shittu et al., 2011, 2012; Kolawole et al., 2013), we studied MSSA isolates obtained from various clinical sources in Nigeria using this comprehensive, array-based approach to provide an insight on the major factors associated with infection and disease.

Materials and methods

Identification and antibiotic susceptibility testing of S. aureus isolates

The isolates (n = 52) were obtained from samples processed as part of surveillance activities in the microbiology laboratories of six health care institutions located in Ado-Ekiti, Ile-Ife, Osogbo, Lagos, and Ibadan in South-West Nigeria, and Maiduguri in North-East Nigeria. The duration of collection of isolates was from March 2009 to April, 2010. Only the isolates were analyzed in this study. Preliminary verification as S. aureus was based on colony characteristics on blood agar, positive results for catalase, coagulase and DNase tests. Twelve isolates from a previous study (Shittu et al., 2011) were also included in this investigation. Identification was confirmed by Matrix-Assisted Laser Desorption/Ionization-Time Of Flight analysis (MALDI-TOF). Susceptibility testing to penicillin (10 units), cefoxitin (30 μg), doxycycline (30 μg), erythromycin (15 μg), clindamycin (2 μg), gentamicin (10 μg), chloramphenicol (30 μg), and trimethoprim-sulfamethoxazole (1.25/23.75 μg) were determined using the disk diffusion method according to the Clinical Laboratory Standards Institute guidelines (Clinical and Laboratory Standards Institute (CLSI), 2009).

DNA extraction

S. aureus genomic DNA was extracted from an 18–24 h old culture on sheep blood agar using lysis buffer and lysis enhancer (StaphyType Kit, Alere Technologies GmbH, Jena, Germany) and processed using a DNeasy tissue kit (Qiagen, Hilden, Germany).

Molecular typing of the isolates

Typing of S. aureus was based on sequencing of the hypervariable region of the protein A gene (spa). The spa types were determined using the Ridom StaphType software (Ridom GmbH, Würzburg, Germany, version 2.1.1) (Harmsen et al., 2003). Multilocus sequence typing (MLST) was performed for one isolate of each spa type (Enright et al., 2000), as a spa type usually belongs to one sequence type (ST) with few exceptions due to homoplasies (Basset et al., 2009, 2012). The allelic profiles and STs were assigned using the MLST S. aureus database (www.mlst.net), and the sequence types of the remaining isolates were inferred from the derived MLST data.

DNA microarray hybridization

The DNA microarray of the StaphyType™ kit (Alere Technologies GmbH, Jena, Germany) was used in this study according to previously established protocols (Monecke et al., 2008). The isolates were grouped with various clonal complexes (CCs) by the imaging software Iconoclust based on comparison of hybridization profiles to a collection of reference strains previously characterized by MLST.

Splits graph construction

The SplitsTree algorithm (Huson and Bryant, 2006) and software was used to analyze the similarities between hybridization patterns, and network tree construction was performed using SplitsTree 4.10 on default settings (characters transformation, uncorrected P; distance transformation, Neighbor-Net; and variance, ordinary least squares).

Results

Identification of S. aureus isolates

A total of 52 MSSA (3 and 49 isolates from nasal and clinical sources, respectively) were analyzed (Table 1). The clinical isolates were obtained from wounds and associated infections (n = 29; 59.2%), urinary tract infections (n = 6; 12.2%), semen/infertility diagnosis (n = 4; 8.2%), ocular infections (n = 3; 6.1%), and pneumonia (n = 2; 4.1%). One isolate each was from otitis media, and blood related infections, while information on three isolates was not available. The clinical isolates were obtained from health care institutions located in Ile-Ife (n = 26; 53.1%), Osogbo (n = 11; 22.4%), Maiduguri (n = 5; 10.2%), Lagos (n = 4; 8.2%), Ibadan, and Ado-Ekiti (n = 2 isolates each: 4.1%).

Table 1.

Characterization of the methicillin-susceptible S. aureus (MSSA) from Nigeria based on antibiotyping, microarray analysis, spa typing, and MLST.

Isolate Number Location Sample/Clinical diagnosis Antibiogram Score (%) (Alere) agr/Clonal complex (Alere) spa type MLST
11486_24 Ile-Ife Wound Infection PEN 93.8 agr_III/CC1 t127 ST1
AB5_28 Osogbo UTI PEN, ERY(i) 92.8 agr_III/CC1 t127 ST1
Aro_29 Osogbo Semen PEN 94.3 agr_III/CC1 t127 ST1
MD16_4 Not available Not available PEN 94.3 agr_III/CC1 t127 ST1
MD20_8* Maiduguri Wound infection PEN, ERY(i), CC(i) 93.5 agr_III/CC1 t321 ST1
6056_34 Osogbo Urine PEN 93.9 agr_III/CC1 t10433 ST1
5675_6 Ile-Ife Abscess PEN 91.8 agr_II/CC5 t311 ST5
5221_7 Ile-Ife Urine PEN, ERY(i), SXT(i) 93.8 agr_II/CC5 t311 ST5
D23_15 Ile-Ife Pneumonia PEN 92.8 agr_II/CC5 t311 ST5
D42_17 Ile-Ife Adenocarcinoma PEN, ERY(i) 92.4 agr_II/CC5 t311 ST5
D46_18 Ile-Ife Wound Infection PEN, ERY(i) 92.2 agr_II/CC5 t311 ST5
1423_36 Osogbo Urine PEN, ERY(i) 93.8 agr_II/CC5 t442 ST5
D19_14 Ile-Ife Not available PEN 93.5 agr_II/CC5 t688 ST5
Asu29_27 Osogbo Otitis media PEN, DO, ERY(i) 91.9 agr_II/CC5 t1277 ST5
3211_30 Osogbo Wound Infection PEN 92.9 agr_II/CC5 t3235 ST5
6773_11 Ile-Ife Wound Infection PEN 93.6 agr_I/CC7 t091 ST789
N37_19 Ile-Ife Erythematous lesion PEN, SXT 90 agr_I/CC8 t064 ST2427
UC45_37 Ibadan Eye swab PEN, GM, CHL, SXT 91.3 agr_I/CC8 t2658 ST2427
55_40 Ado-Ekiti Wound Infection PEN, DO(i), GM, CHL, SXT 90.3 agr_I/CC8 t2658 ST2427
OS39_13* Lagos Semen/Infertility PEN, DO(i), SXT 91.7 agr_I/CC8 t951 ST8
11450_23 Ile-Ife Sputum PEN 92.9 agr_II/CC15 t084 ST15
5189_1 Ile-Ife Advanced Cancer PEN 94 agr_II/CC15 t084 ST15
189_2 Ile-Ife Blood PEN, DO(i), ERY(i) 93.9 agr_II/CC15 t084 ST15
4013_14* Ile-Ife Wound infection PEN 94.9 agr_II/CC15 t084 ST15
5828_5 Ile-Ife Abscess susceptible to all antibiotics tested 94.4 agr_II/CC15 t2216 ST15
MD7_3* Maiduguri Semen/Infertility PEN, ERY(i) 94.6 agr_II/CC15 t2216 ST15
MD19_11* Maiduguri Wound infection PEN 94.4 agr_II/CC15 t2216 ST15
S13_6* Lagos Urinary Tract Infection PEN, ERY(i), SXT 93.1 agr_I/CC25 t3772 ST25
3925_32 Osogbo Wound Infection PEN, ERY(i), SXT 91.4 agr_I/CC25 t10183 ST25
6073_3 Not available Not available PEN, DO 91.7 agr_III/CC30 t017 ST30
D30_16 Ile-Ife Cholecystitis PEN 94.7 agr_III/CC30 t318 ST30
6506_2 Osogbo Wound Infection PEN, ERY(i), CC(i) 91.4 agr_III/CC30 t318 ST30
NS7708_22 Ile-Ife Nasal swab/screening PEN, ERY(i) 94.7 agr_III/CC30 t318 ST30
54_39 Ado-Ekiti Wound Infection PEN 94.4 agr_III/CC30 t318 ST30
S12_7* Lagos Wound infection PEN, ERY(i) 93.8 agr_III/CC30 t318 ST30
OS41_10* Lagos Wound infection PEN 93.1 agr_III/CC30 t318 ST30
6330_4 Ile-Ife Osteomyelitis PEN 94.3 agr_III/CC30 t318 ST30
NS2907_21 Ile-Ife Nasal swab/screening PEN, ERY(i), CC(i) 91.8 agr_I/CC45 t095 ST508
3950_33 Osogbo Urine PEN 91.5 agr_I/CC45 t10434 ST508
GDC_35 Osogbo Semen PEN 94.9 agr_III/CC80 t934 ST80
MD14_2* Maiduguri Wound infection PEN, DO(i) 92.9 agr_I/CC97 t458 ST97
ZU_26 Ile-Ife Unavailable PEN, ERY(i) 89.3 agr_IV/CC121 t159 ST121
UC47_38 Ibadan Eye swab PEN, DO, ERY(i), CC(i) 92.1 agr_IV/CC121 t159 ST121
W10_5* Ile-Ife Wound infection PEN, ERY(i) 91.8 agr_IV/CC121 t314 ST121
MD_9* Maiduguri Wound infection PEN, ERY(i), CC(i) 92.1 agr_IV/CC121 t314 ST121
6376_3 Ile-Ife Abscess PEN, DO(i) 93.1 agr_IV/CC121 t2304 ST121
6540_10 Ile-Ife Bone Marrow Infection PEN 93.5 agr_IV/CC121 t2304 ST121
NS2986_20 Ile-Ife Nasal swab/screening PEN, DO, ERY(i), CC(i), SXT(i) 92.8 agr_IV/CC121 t2304 ST121
3920_31 Osogbo Aspirate PEN 92.8 agr_IV/CC121 t2304 ST121
D3_12 Ile-Ife Cervical cancer PEN, ERY(i) 94.6 agr_I/ST152 t355 ST152
D12_13 Ile-Ife Ocular infection PEN 94.6 agr_I/ST152 t355 ST152
W7.2_4* Ile-Ife Wound infection PEN 96.3 agr_I/ST152 t355 ST152
Open in a new tab
*

S. aureus analyzed in a previous study; (i): intermediate susceptibility; agr, accessory gene regulator; PEN, Penicillin; DO, Doxycycline; ERY, Erythromycin; CLI, Clindamycin; GEN, Gentamicin; CHL, Chloramphenicol; SXT, trimethoprim/sulfamethoxazole; CC, Clonal Complex; ST, Sequence type.

spa types selected for Multilocus sequence typing (MLST); Sequence types (STs) of the remaining isolates were inferred from the derived MLST data.

Antibiotic susceptibility testing

All the isolates were susceptible to cefoxitin and 98.1% (n = 51) were resistant to penicillin. Only two isolates each exhibited resistance to chloramphenicol and gentamicin, and four to doxycycline. Intermediate susceptibility to clindamycin and erythromycin were identified in six and 21 isolates, respectively. The predominant antibiotype was resistance only to penicillin (n = 23; 44.2%), and resistance to penicillin with intermediate susceptibility to erythromycin (n = 10; 19.2%) (Table 1).

Sequence based typing (spa and MLST)

A total of 26 spa types were identified among the 52 MSSA isolates and the most common were t318 (n = 7), t311 (n = 5), t084, t127, and t2304 (n = 4 each). Based on MLST, the MSSA were classified into 13 sequence types (STs) (Table 1).

DNA microarray analysis

The assay confirmed the identity of the isolates (S. aureus) by positive results for specific markers including rndD1 (domain 1 of 23S rRNA), protein A (spa), glyceraldehyde 3-phosphate dehydrogenase (gapA), catalase A (katA), thermostable nuclease (nuc), and staphylococcal accessory regulator A (sarA) (Supplementary Materials 1, 2). The hybridization profiles revealed that the 52 MSSA isolates clustered in 12 different CCs. More than half (55.8%) of the CCs were associated with the genetic background common to the major methicillin-resistant S. aureus (MRSA) clones i.e., CC1 (n = 6 isolates), CC5 (n = 9), CC8 (n = 4), CC30 (n = 8), and CC45 (n = 2). The rest were assigned with CC7 (n = 1), CC15 (n = 7), CC25 (n = 2), CC80 (n = 1), CC97 (n = 1), CC121 (n = 8), and CC152 (n = 3).

Antibiotic resistance genes

A total of 69.2% (n = 36) of the isolates yielded a hybridization signal for the beta-lactamase gene (blaZ) and only 10 and three isolates were positive for the tetracycline resistance genes (tetK and tetM), respectively. The two MSSA in CC8 which exhibited phenotypic resistance to chloramphenicol and gentamicin possessed the corresponding resistance genes (cat and aacA-aphD). In addition, the single CC80 isolate was positive for the lincosamide resistance gene (lnuA).

Accessory gene regulator and capsular typing

The distribution of agr/CCs/capsule types for the MSSA is indicated in Figure 1. Overall, 13 (25%) isolates assigned to different clonal lineages (CC7, CC8, CC25, CC45, CC97, and CC152) were associated with agr group I, 16 (30.2%; CC5 and CC15) with group II, and 15 (28.8%; CC1, CC30 and CC80) with group III. CC121 was the only representative for agr group IV (n = 8; 15.4%) (Table 1). The capsule type 8 was the most frequent and detected in 33 (63.5%) isolates affiliated with CC1, CC7, CC15, CC30, CC45, CC80, and CC121. The remaining isolates (20; 38.5%) belonged to capsule type 5 (assigned with CC5, CC8, CC25, CC97, and CC152).

Figure 1.

Figure 1

Open in a new tab

Distribution of agr/CCs/capsule type of MSSA in Nigeria.

Enterotoxin genes

PVL-positive isolates (n = 27) belonged to CC1, CC5, CC15, CC30, CC80, CC121, and CC152 (Supplementary Material 1). Moreover, the lukF gene (haemolysin gamma; component B) was universally detected in all the CCs and the lukE genes was a common feature except with MSSA isolates in CC30, CC45, and CC152 (Supplementary Material 3). With respect to the carriage of superantigen genes, only three MSSA (one isolate in CC1 and two in CC45) tested positive for the toxic shock syndrome toxin gene (tst-1) (Supplementary Material 1). All the isolates in this study lacked a hybridization signal for the enterotoxin E gene (see Supplementary Material 2) and the enterotoxin genes were not detected in MSSA assigned with CC80, CC97, and CC152. In the haemolysin gene family, almost all (98.1%) the isolates in the various CCs possessed the haemolysin alpha and delta genes (hla, hld), while the haemolysin beta gene (hlb) was identified in the various CCs except in CC15, CC45, and CC152.

Microbial surface components recognizing adhesive matrix molecule (MSCRAMM) genes

All the isolates were negative for the surface protein involved in biofilm production (bap), but possessed the genes for the inter-cellular adhesion protein (icaA/C/D) (CC152 isolates were icaC negative). The genes for clumping factor A (clfA), cell surface elastin binding protein (ebpS), fibronectin-binding protein A (fnbA) and proteases (sspA, sspB, and sspP) were detected in all the isolates (Supplementary Materials 1, 3).

Splits tree analysis

The analysis identified four main clusters (CC5/CC25; CC8/CC97; CC1/CC7/CC80, and CC30/CC45) indicating the phylogenetic relationship between the isolates (Figure 2).

Figure 2.

Figure 2

Open in a new tab

Splits tree graph based on hybridization profile of the MSSA isolates. The results of all array hybridization experiments were arranged in a matrix. Columns represent the target genes and the rows represent the number of experiments; 1, positive; 0, negative; −, ambiguous. Converted to “sequences”: 1, c; 0, g; −, c.

Discussion

We observed a complete agreement between DNA microarray analysis and MLST in the delineation of the isolates (Table 1), showing that the hybridization profile could be used to predict the lineages. Furthermore, the heterogeneous and divergent nature of the isolates observed in this study provided evidence on the overall higher diversity of MSSA compared with MRSA (Deurenberg and Stobberingh, 2008; Goering et al., 2008; Ghasemzadeh-Moghaddam et al., 2011; Ruffing et al., 2012; Blomfeldt et al., 2013; Rasmussen et al., 2013, 2014). In Nigeria, many diagnostic microbiology laboratories rely on the disc diffusion technique for antibiotic susceptibility testing, but this protocol does not provide information on the nature of resistance genes. The antibiotic susceptibility results observed in this study were in accordance with the corresponding resistance gene profiles by DNA microarray. MSSA isolates that exhibited full resistance to trimethoprim-sulfamethoxazole clustered with CC8 and CC25, but were dfrS1 negative indicating that a different mechanism could be attributed to resistance. A recent study (Nurjadi et al., 2014) has provided strong evidence that the dfrG gene is the predominant trimethoprim resistance determinant on S. aureus in Africa. Overall, resistant determinants for antibiotics, heavy metal and quaternary ammonium compounds were observed more often in CC8 than other CCs (Supplementary Materials 1, 3).

The accessory gene regulator (agr) and capsule typing methods are useful front-line tools for the characterization of S. aureus (Goerke et al., 2005). Hybridization signals for agr type I and IV were observed for one, three, and four isolates grouped with CC25, CC152, and CC121, respectively (Supplementary Materials 1, 2). This could be attributed to possible cross-hybridization as the alleles for the two agr types are closely related (Monecke et al., 2010). Our observations on CCs and agr groups were similar to previous reports on MSSA in five major African towns (Breurec et al., 2010), Gabon (Ateba Ngoa et al., 2012), and Nigeria (Ghebremedhin et al., 2009; Kolawole et al., 2013). In addition, our study also support the view (Wright et al., 2005; Holtfreter et al., 2007; Rasmussen et al., 2014) that an agr type may be detected in isolates which are assigned to genetically diverse CCs, whereas, it is also associated with specific CCs. The dominance of capsule type 8 in MSSA is consistent with data from Gabon (Schaumburg et al., 2011), Norway (Blomfeldt et al., 2013), and Sweden (Rasmussen et al., 2013, 2014).

Staphylococcal enterotoxins are typically encoded by genes located on mobile genetic elements (Baba et al., 2002). The egc cluster (seg+sei+sem+sen+seo+seu) is located on the genomic island vSAβ and reported to be associated with specific clonal types regardless of the geographical strain distribution (Lindsay and Holden, 2006). In this investigation, the egc-enterotoxin gene cluster was a unique feature for CC5, CC25, CC30, CC45, and CC121. Previous studies have indicated that the cluster is predominantly present in MSSA assigned with CC5, CC25, CC30, and CC45 (Van Trijp et al., 2010; Rasmussen et al., 2013). The seh gene is linked to the staphylococcal cassette chromosome mec (SCCmec elements) and reported to be restricted to the CC1 genomic background (Baba et al., 2002). Moreover, the seh gene has also been reported mainly in MSSA-CC30 (Blomfeldt et al., 2013). Nevertheless, our observation on seh-positive MSSA-CC1 is in agreement with previous reports (Chen et al., 2013; Rasmussen et al., 2013).

The genes associated with staphylococcal complement inhibitor (scn) and staphylokinase (sak) were also widely distributed across the CCs but CC15 isolates were sak gene negative. Virulence associated with the exfoliative toxins has been identified to cause epidermal cleavage in staphylococcal scalded skin syndrome (SSSS) and bullous impetigo (Ladhani et al., 1999). The exfoliative toxin D (ETD) is a 27-kDa protein which causes epidermal blisters in newborn mice (Yamasaki et al., 2006). The epidermal cell differentiation factors (EDIN) target and inhibit the small host protein RhoA, a master regulator of the host cell actin cytoskeleton (Inoue et al., 1991; Jaffe and Hall, 2005; Aktories, 2011). Furthermore, the edin-isoform (edinB) and etd genes are located in tandem in a S. aureus etd pathogenicity island in a chromosome of etd-positive S. aureus strains (Yamaguchi et al., 2002). A strong association of the etd gene with invasive CC25 S. aureus isolates has also been reported. In this study, all the isolates assigned with CC25 and CC80 were etd-positive, which is in agreement with a previous study in Nigeria (Shittu et al., 2011). Moreover, MSSA grouped with CC25, CC80, and CC152 were edinB positive but CC152 isolates were etd negative. Our observations were similar to a study on the distribution of the edin gene in S. aureus from diabetic foot ulcers (Messad et al., 2013). A study in MSSA bacteremia isolates in Sweden showed that the collagen binding protein (Cna) was detected in CC1, CC30, and CC45. Our report identified the gene in isolates assigned with CC1, CC30, CC45, CC121, and CC152.

Our study has a number of limitations. Although all isolates were of human origin, and the large majority was obtained from clinical samples, a clear distinction between commensal and clinical strains could not be made based on the available information. An association of isolates within the context of endemicity i.e., nosocomial vs. community associated infections, is also not clear. Furthermore, whereas the microarray analytical database is exhaustive, well-characterized, and validated with isolates from all continents, the attribution of CCs is based on the hybridization reactions and resulting microarray profile rather than gene sequencing, and a positive signal does not necessarily imply the presence of gene product (e.g., protein). In addition, the microarray method was unable to separate ST8 from ST2427. This might be due to the close phylogenetic relation of both STs as they are single locus variants (ST8: 3−3−1−1−4−4−3 and ST2427: 3−3−297−1−4−4−3). Finally, with a collection of 52 isolates studied, and a large number of genes and genetic profile ascertained by microarray, the potential for individual statistical comparisons is limited. Yet, with this comprehensive genetic-analytical approach performed on a clinical isolate collection obtained from patients of various medical institutions in a sub-Saharan African country, Nigeria, a number of important observations could be made which clearly characterize and demarcate the clonal distribution as well as the virulence gene equipment.

More than one half (55.8%; n = 29) of these MSSA isolates were associated with a genetic background which is attributable to classic methicillin-resistant S. aureus (MRSA) clones. PVL-positive isolates were identified in seven of the 12 CCs. Moreover, toxin genes were observed to be distributed mainly with certain clonal types, and in agreement with previous investigations (Holtfreter et al., 2007; Monecke et al., 2008). Antibiotic resistance gene profiles of the isolates by the DNA microarray demonstrated concordant results with data on antibiotic susceptibility testing. The array-based, comprehensive approach has been shown to yield such diverse CC and gene specific results on an isolate collection from sub-Saharan Africa. Overall, microarray analysis proved to be a useful tool to provide useful information on antibiotic resistance, population structure and various virulence factor profiles associated with infection and disease. It is assumed that these findings might be useful for a better understanding of clinical staphylococcal disease presentation, patient care and for assistance in outbreak investigation in health care institutions in a country such as Nigeria. Moreover, our study also underlines the need for further trials employing well-controlled, prospectively collected clinical isolates to delineate the genetic pathogen profile in conjunction with the clinical disease presentation in sub-Saharan Africa.

Author contributions

AS, UR, GP, FS, LM, and MH conceived the study, OO, KO, AR conducted the sample collection and preliminary identification of the isolates. AS performed the microarray technique, AS and UR analyzed the microarray data, and AS wrote the manuscript (with input from all authors). All authors read and approved the final version of the manuscript.

Funding

The stay of AS at the Institute of Medical Microbiology and Hygiene, Institute of Medical Microbiology, Saarland University Medical Centre, Homburg/Saar and the University Hospital Münster, Münster, Germany was supported by the Third World Academy of Science and Deutsche Forschungsgemeinschaft (TWAS-DFG award) and the Deutsche Forschungsgemeinschaft (PAK296, Ei 247/8, He 1850/9−1, and He 1850/11−1).

Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

We would like to thank the management and laboratory staff of the hospitals for their support in isolate collection, and Eniola Dolapo for her assistance in the preparation of this manuscript. We gratefully acknowledge the technical assistance of the staff at the Institute of Medical Microbiology, Saarland University Medical Centre, Homburg/Saar, the Institute of Medical Microbiology, University Hospital Münster and the staff at the Sequencing Unit at the Institute of Hygiene, University Hospital Münster, Germany. We thank Professor Iruka Okeke for the critical review of the manuscript.

Glossary

Abbreviations

Agr

accessory gene regulator

CC

Clonal complex

CLSI

Clinical Laboratory Standards Institute

MSSA

Methicillin susceptible Staphylococcus aureus

MLST

Multilocus sequence typing

PVL

Panton-Valentine Leukocidin

S.aureus

Staphylococcus aureus

SCCmec

Staphylococcal chromosome cassette mec

spa

Staphylococcus aureus protein A

ST

Sequence Type.

Supplementary material

The Supplementary Material for this article can be found online at: http://journal.frontiersin.org/article/10.3389/fmicb.2015.01160

Click here for additional data file. (84.6KB, XLSX)
Click here for additional data file. (73.8KB, XLSX)
Click here for additional data file. (184KB, DOC)

References

  1. Ahmed E. F., Gad G. F., Abdalla A. M., Hasaneen A. M., Abdelwahab S. F. (2014). Prevalence of methicillin resistant Staphylococcus aureus among Egyptian patients after surgical interventions. Surg. Infect. (Larchmt). 15, 404–411. 10.1089/sur.2013.212 [DOI] [PubMed] [Google Scholar]
  2. Aiken A. M., Mutuku I. M., Sabat A. J., Akkerboom V., Mwangi J., Scott J. A., et al. (2014). Carriage of Staphylococcus aureus in Thika Level 5 Hospital, Kenya: a cross-sectional study. Antimicrob. Resist. Infect. Control 3:22. 10.1186/2047-2994-3-22 [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Aktories K. (2011). Bacterial protein toxins that modify host regulatory GTPases. Nat. Rev. Microbiol. 9, 487–498. 10.1038/nrmicro2592 [DOI] [PubMed] [Google Scholar]
  4. Alabi A. S., Frielinghaus L., Kaba H., Kösters K., Huson M. A., Kahl B. C., et al. (2013). Retrospective analysis of antimicrobial resistance and bacterial spectrum of infection in Gabon, Central Africa. BMC Infect. Dis. 13:455. 10.1186/1471-2334-13-455 [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Ateba Ngoa U., Schaumburg F., Adegnika A. A., Kosters K., Moller T., Fernandes J. F., et al. (2012). Epidemiology and population structure of Staphylococcus aureus in various population groups from a rural and semi urban area in Gabon, Central Africa. Acta Trop. 124, 42–47. 10.1016/j.actatropica.2012.06.005 [DOI] [PubMed] [Google Scholar]
  6. Baba T., Takeuchi F., Kuroda M., Yuzawa H., Aoki K., Oguchi A., et al. (2002). Genome and virulence determinants of high virulence community-acquired MRSA. Lancet 359, 1819–1827. 10.1016/S0140-6736(02)08713-5 [DOI] [PubMed] [Google Scholar]
  7. Basset P., Hammer N. B., Kuhn G., Vogel V., Sakwinska O., Blanc D. S. (2009). Staphylococcus aureus clfB and spa alleles of the repeat regions are segregated into major phylogenetic lineages. Infect. Genet. Evol. 9, 941–947. 10.1016/j.meegid.2009.06.015 [DOI] [PubMed] [Google Scholar]
  8. Basset P., Nübel U., Witte W., Blanc D. S. (2012). Evaluation of adding a second marker to overcome Staphylococcus aureus spa typing homoplasies. J. Clin. Microbiol. 50, 1475–1477. 10.1128/JCM.00664-11 [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Blomfeldt A., Aamot H. V., Eskesen A. N., Müller F., Monecke S. (2013). Molecular characterization of methicillin-sensitive Staphylococcus aureus isolates from bacteremic patients in a Norwegian University Hospital. J. Clin. Microbiol. 51, 345–347. 10.1128/JCM.02571-12 [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Breurec S., Fall C., Pouillot R., Boisier P., Brisse S., Diene-Sarr F., et al. (2010). Epidemiology of methicillin-susceptible Staphylococcus aureus lineages in five major African towns: high prevalence of Panton-Valentine leukocidin genes. Clin. Microbiol. Infect. 17, 633–639. 10.1111/j.1469-0691.2010.03320.x [DOI] [PubMed] [Google Scholar]
  11. Chen X., Wang W.-K., Han L.-Z., Liu Y., Zhang H., Tang J., et al. (2013). Epidemiological and genetic diversity of Staphylococcus aureus causing bloodstream infection in Shanghai, 2009-2011. PLoS ONE 8:e72811. 10.1371/journal.pone.0072811 [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Clinical Laboratory Standards Institute (CLSI) (2009). Performance Standards for Antimicrobial Disk Susceptibility Tests. Approved Standard, 10th Edn. Wayne, Penn.
  13. Conceição T., Coelho C., Santos Silva I., de Lencastre H., Aires-de-Sousa M. (2015). Staphylococcus aureus in former Portuguese colonies from Africa and the far east: missing data to help fill the world map. Clin. Microbiol. Infect. 21, 842.e1–842.e10. 10.1016/j.cmi.2015.05.010 [DOI] [PubMed] [Google Scholar]
  14. Corey G. R. (2009). Staphylococcus aureus bloodstream infections: definitions and treatment. Clin. Infect. Dis. 48, S254–S259. 10.1086/598186 [DOI] [PubMed] [Google Scholar]
  15. De Boeck H., Vandendriessche S., Hallin M., Batoko B., Alworonga J. P., Mapendo B., et al. (2015). Staphylococcus aureus nasal carriage among health care workers in Kisangani, the democratic republic of Congo. Eur. J. Clin. Microbiol. Infect. Dis. 34, 1567–1572. 10.1007/s10096-015-2387-9 [DOI] [PubMed] [Google Scholar]
  16. Deurenberg R. H., Stobberingh E. E. (2008). The evolution of Staphylococcus aureus. Infect. Genet. Evol. 8, 747–763. 10.1016/j.meegid.2008.07.007 [DOI] [PubMed] [Google Scholar]
  17. Egyir B., Guardabassi L., Sørum M., Nielsen S. S., Kolekang A., Frimpong E., et al. (2014). Molecular epidemiology and antimicrobial susceptibility of clinical Staphylococcus aureus from healthcare institutions in Ghana. PLoS ONE 9:e89716. 10.1371/journal.pone.0089716 [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Enright M. C., Day N. P., Davies C. E., Peacock S. J., Spratt B. G. (2000). Multilocus sequence typing for characterization of methicillin-resistant and methicillin-susceptible clones of Staphylococcus aureus. J. Clin. Microbiol. 38, 1008–1015. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Foster T. J., Höök M. (1998). Surface protein adhesins of Staphylococcus aureus. Trends Microbiol. 6, 484–488. 10.1016/S0966-842X(98)01400-0 [DOI] [PubMed] [Google Scholar]
  20. Ghasemzadeh-Moghaddam H., Ghaznavi-Rad E., Sekawi Z., Yun-Khoon L., Aziz M. N., Hamat R. A., et al. (2011). Methicillin susceptible Staphylococcus aureus from clinical and community sources are genetically diverse. Int. J. Med. Microbiol. 301, 347–353. 10.1016/j.ijmm.2010.10.004 [DOI] [PubMed] [Google Scholar]
  21. Ghebremedhin B., Olugbosi M. O., Raji A. M., Layer F., Bakare R. A., König B., et al. (2009). Emergence of a community-associated methicillin-resistant Staphylococcus aureus strain with a unique resistance profile in Southwest Nigeria. J. Clin. Microbiol. 47, 2975–2980. 10.1128/JCM.00648-09 [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Goering R. V., Shawar R. M., Scangarella N. E., O'Hara F. P., Amrine-Madsen H., West J. M., et al. (2008). Molecular epidemiology of methicillin-resistant and methicillin-susceptible Staphylococcus aureus isolates from global clinical trials. J. Clin. Microbiol. 46, 2842–2847. 10.1128/JCM.00521-08 [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Goerke C., Esser S., Kümmel M., Wolz C. (2005). Staphylococcus aureus strain designation by agr and cap polymorphism typing and delineation of agr diversification by sequence analysis. Int. J. Med. Microbiol. 295, 67–75. 10.1016/j.ijmm.2005.01.004 [DOI] [PubMed] [Google Scholar]
  24. Groome M. J., Albrich W. C., Wadula J., Khoosal M., Madhi S. A. (2012). Community-onset Staphylococcus aureus bacteraemia in hospitalized African children: high incidence in HIV-infected children and high prevalence of multidrug resistance. Paediatr. Int. Child Health. 32, 140–146. 10.1179/1465328111Y.0000000044 [DOI] [PubMed] [Google Scholar]
  25. Grumann D., Nübel U., Bröker B. M. (2014). Staphylococcus aureus toxins – their functions and genetics. Infect. Genet. Evol. 21, 583–592. 10.1016/j.meegid.2013.03.013 [DOI] [PubMed] [Google Scholar]
  26. Harmsen D., Claus H., Witte W., Rothgänger J., Claus H., Turnwald D., et al. (2003). Typing of methicillin-resistant Staphylococcus aureus in a university setting by using novel software for spa repeat determination and database management. J. Clin. Microbiol. 41, 5442–5448. 10.1128/JCM.41.12.5442-5448.2003 [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Holtfreter S., Grumann D., Schmudde M., Nguyen H. T. T., Eichler P., Strommenger B., et al. (2007). Clonal distribution of superantigen genes in clinical Staphylococcus aureus isolates. J. Clin. Microbiol. 45, 2669–2680. 10.1128/JCM.00204-07 [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Huson D. H., Bryant D. (2006). Application of phylogenetic networks in evolutionary studies. Mol. Biol. Evol. 23, 254–267. 10.1093/molbev/msj030 [DOI] [PubMed] [Google Scholar]
  29. Inoue S., Sugai M., Murooka Y., Paik S. Y., Hong Y. M., Ohgai H., et al. (1991). Molecular cloning and sequencing of the epidermal cell differentiation inhibitor gene from Staphylococcus aureus. Biochem. Biophys. Res. Commun. 174, 459–464. 10.1016/0006-291X(91)91438-I [DOI] [PubMed] [Google Scholar]
  30. Jaffe A. B., Hall A. (2005). RHO GTPases: biochemistry and biology. Annu. Rev. Cell Dev. Biol. 21, 247–269. 10.1146/annurev.cellbio.21.020604.150721 [DOI] [PubMed] [Google Scholar]
  31. Jido T., Garba I. (2012). Surgical-site infection following cesarean section in Kano, Nigeria. Ann. Med. Health Sci. Res. 2, 33–36. 10.4103/2141-9248.96934 [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Kayange N., Kamugisha E., Mwizamholya D. L., Jeremiah S., Mshana S. E. (2010). Predictors of positive blood culture and deaths among neonates with suspected neonatal sepsis in a tertiary hospital, Mwanza-Tanzania. BMC Pediatr. 10:39. 10.1186/1471-2431-10-39 [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Kihla A. J., Ngunde P. J., Evelyn M. S., Gerard N., Ndip R. N. (2014). Risk factors for wound infection in health care facilities in Buea, Cameroon: aerobic bacterial pathogens and antibiogram of isolates. Pan. Afr. Med. J. 18, 6. 10.11604/pamj.2014.18.6.2304 [DOI] [PMC free article] [PubMed] [Google Scholar]
  34. Kolawole D. O., Adeyanju A., Schaumburg F., Akinyoola A. L., Lawal O. O., Amusa Y. B., et al. (2013). Characterization of colonizing Staphylococcus aureus isolated from surgical wards' patients in a Nigerian university hospital. PLoS ONE 8:e68721. 10.1371/journal.pone.0068721 [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Kraef C., Alabi A. S., Peters G., Becker K., Kremsner P. G., Rossatanga E. G., et al. (2015). Co-detection of Panton-Valentine leukocidin encoding genes and cotrimoxazole resistance in Staphylococcus aureus in Gabon: implications for HIV-patients' care. Front. Microbiol. 6:60. 10.3389/fmicb.2015.00060 [DOI] [PMC free article] [PubMed] [Google Scholar]
  36. Ladhani S., Joannou C. L., Lochrie D. P., Evans R. W., Poston S. M. (1999). Clinical, microbial and biochemical aspects of the exfoilative toxins causing staphylococcal scalded-skin syndrome. Clin. Microbiol. Rev. 12, 224–242. [DOI] [PMC free article] [PubMed] [Google Scholar]
  37. Lindsay J. A., Holden M. T. (2006). Understanding the rise of the superbug: investigation of the evolution and genomic variation of Staphylococcus aureus. Funct. Integr. Genomics 6, 186–201. 10.1007/s10142-005-0019-7 [DOI] [PubMed] [Google Scholar]
  38. Lowy F. D. (1998). Staphylococcus aureus infections. N. Engl. J. Med. 339, 520–532. 10.1056/NEJM199808203390806 [DOI] [PubMed] [Google Scholar]
  39. Messad N., Landraud L., Canivet B., Lina G., Richard J.-L., Sotto A. (2013). Distribution of edin in Staphylococcus aureus isolated from diabetic foot ulcers. Clin. Microbiol. Infect. 19, 875–880. 10.1111/1469-0691.12084 [DOI] [PubMed] [Google Scholar]
  40. Mhada T. V., Fredrick F., Matee M. I., Massawe A. (2012). Neonatal sepsis at Muhimbili National Hospital, Dar es Salaam, Tanzania; aetiology, antimicrobial sensitivity pattern and clinical outcome. BMC Public Health 12:904. 10.1186/1471-2458-12-904 [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. Monecke S., Coombs G., Shore A. C., Coleman D. C., Akpaka P., Borg M., et al. (2011). A field guide to pandemic, epidemic and sporadic clones of methicillin-resistant Staphylococcus aureus. PLoS ONE 6:e17936. 10.1371/journal.pone.0017936 [DOI] [PMC free article] [PubMed] [Google Scholar]
  42. Monecke S., Kanig H., Rudolph W., Müller E., Coombs G., Hotzel H., et al. (2010). Characterisation of Australian MRSA strains ST75- and ST883-MRSA-IV and analysis of their accessory gene regulator locus. PLoS ONE 5:e14025. 10.1371/journal.pone.0014025 [DOI] [PMC free article] [PubMed] [Google Scholar]
  43. Monecke S., Slickers P., Ehricht R. (2008). Assignment of Staphylococcus aureus isolates to clonal complexes based on microarray analysis and pattern recognition. FEMS Immunol. Med. Microbiol. 53, 237–251. 10.1111/j.1574-695X.2008.00426.x [DOI] [PubMed] [Google Scholar]
  44. Naidoo R., Nuttali J., Whitelaw A., Eley B. (2013). Epidemiology of Staphylococcus aureus Bacteraemia at a Tertiary Children's Hospital in Cape Town, South Africa. PLoS ONE 8:e78396. 10.1371/journal.pone.0078396 [DOI] [PMC free article] [PubMed] [Google Scholar]
  45. Novick R. P. (2006). Staphylococcal pathogenesis and pathogenicity factors: genetics and regulation, in Gram-Positive Pathogens, eds Fischetti V., Novick R., Ferretti J., Portnoy D., Rood J. (Washington, DC: ASM Press; ), 496–516. [Google Scholar]
  46. Nurjadi D., Olalekan A. O., Layer F., Shittu A. O., Alabi A., Ghebremedhin B., et al. (2014). Emergence of trimethoprim resistance gene dfrG in Staphylococcus aureus causing human infection and colonization in sub-Saharan Africa and its import to Europe. J. Antimicrob. Chemother. 69, 2361–2368. 10.1093/jac/dku174 [DOI] [PubMed] [Google Scholar]
  47. Oladeinde B. H., Omoregie R., Olley M., Anunibe J. A., Onifade A. A. (2013). A 5-year surveillance of wound infections at a rural tertiary hospital in Nigeria. Afr. Health Sci. 13, 351–356. 10.4314/ahs.v13i2.22 [DOI] [PMC free article] [PubMed] [Google Scholar]
  48. Oosthuysen W. F., Orth H., Lombard C. J., Sinha B., Wasserman E. (2014). Population structure analyses of Staphylococcus aureus at Tygerberg Hospital, South Africa, reveals a diverse population, high prevalence of Panton-Valentine leukocidin genes and unique local MRSA clones. Clin. Microbiol. Infect. 20, 652–659. 10.1111/1469-0691.12452 [DOI] [PubMed] [Google Scholar]
  49. Raji A., Ojemhen O., Umejiburu U., Ogunleye A., Blanc D. S., Basset P. (2013). High genetic diversity of Staphylococcus aureus in a tertiary care hospital in South west Nigeria. Diagn. Microbiol. Infect. Dis. 77, 367–369. 10.1016/j.diagmicrobio.2013.08.030 [DOI] [PubMed] [Google Scholar]
  50. Rasmussen G., Monecke S., Brus O., Ehricht R., Soderquist B. (2014). Long term molecular epidemiology of methicillin-susceptible Staphylococcus aureus bacteremia isolates in Sweden. PLoS ONE 9:e114276. 10.1371/journal.pone.0114276 [DOI] [PMC free article] [PubMed] [Google Scholar]
  51. Rasmussen G., Monecke S., Ehricht R., Soderquist B. (2013). Prevalence of clonal complexes and virulence genes among commensal and invasive Staphylococcus aureus isolates in Sweden. PLoS ONE 8:e77477. 10.1371/journal.pone.0077477 [DOI] [PMC free article] [PubMed] [Google Scholar]
  52. Rovira G., Cooke E. F., Mucavele H., Sitoe A., Madrid L., Nhampossa T., et al. (2015). The challenge of diagnosing and treating Staphylococcus aureus invasive infections in a resource-limited sub-Saharan Africa setting: a case report. J. Trop. Pediatr. 61, 397–402. 10.1093/tropej/fmv045 [DOI] [PubMed] [Google Scholar]
  53. Ruffing U., Akulenko R., Bischoff M., Helms V., Herrmann M., von Müller L. (2012). Matched-Cohort DNA microarray diversity analysis of methicillin sensitive and methicillin-resistant Staphylococcus aureus isolates from hospital admission patients. PLoS ONE 7:e52487. 10.1371/journal.pone.0052487 [DOI] [PMC free article] [PubMed] [Google Scholar]
  54. Schaumburg F., Ngoa U. A., Kösters K., Köck R., Adegnika A. A., Kremsner P. G., et al. (2011). Virulence factors and genotypes of Staphylococcus aureus from infection and carriage in Gabon. Clin. Microbiol. Infect. 17, 1507–1513. 10.1111/j.1469-0691.2011.03534.x [DOI] [PubMed] [Google Scholar]
  55. Schaumburg F., Pauly M., Anoh E., Mossoun A., Wiersma L., Schubert G., et al. (2015). Staphylococcus aureus complex from animals and humans in three remote African regions. Clin. Microbiol. Infect. 21, e1–e8. 10.1016/j.cmi.2014.12.001 [DOI] [PubMed] [Google Scholar]
  56. Seni J., Bwanga F., Najjuka C. F., Makobore P., Okee M., Mshana S. E. (2013). Molecular characterization of Staphylococcus aureus from patients with surgical site infections at Mulago Hospital in Kampala, Uganda. PLoS ONE 8:e66153. 10.1371/journal.pone.0066153 [DOI] [PMC free article] [PubMed] [Google Scholar]
  57. Shittu A. O., Okon K., Adesida S., Oyedara O., Witte W., Strommenger B., et al. (2011). Antibiotic resistance and molecular epidemiology of Staphylococcus aureus in Nigeria. BMC Microbiol. 11:92. 10.1186/1471-2180-11-92 [DOI] [PMC free article] [PubMed] [Google Scholar]
  58. Shittu A., Oyedara O., Abegunrin F., Okon K., Raji A., Taiwo S., et al. (2012). Characterization of methicillin-susceptible and -resistant staphylococci in the clinical setting: a multicentre study in Nigeria. BMC Infect. Dis. 12:286. 10.1186/1471-2334-12-286 [DOI] [PMC free article] [PubMed] [Google Scholar]
  59. Skaar E. P., Schneewind O. (2004). Iron-regulated surface determinants (lsd) of Staphylococcus aureus: stealing iron from heme. Microbes Infect. 6, 390–397. 10.1016/j.micinf.2003.12.008 [DOI] [PubMed] [Google Scholar]
  60. Van Trijp M. J. C. A., Melles D. C., Snijders S. V., Wertheim H. F. L., Verbrugh H. A., van Belkum A., et al. (2010). Genotypes, superantigen gene profiles, and presence of exfoliative toxin genes in clinical methicillin-susceptible Staphylococcus aureus isolates. Diagn. Microbiol. Infect. Dis. 66, 222–224. 10.1016/j.diagmicrobio.2009.08.021 [DOI] [PubMed] [Google Scholar]
  61. Waters D., Jawad I., Ahmad A., Luksic I., Nair H., Zgaga L., et al. (2011). Aetiology of community-acquired neonatal sepsis in low- and middle-income countries. J. Glob. Health 1, 154–170. [PMC free article] [PubMed] [Google Scholar]
  62. Wright J. S., Traber K. E., Corrigan R., Benson S. A., Musser J. M., Novick R. P. (2005). The agr radiation: an early event in the evolution of staphylococci. J. Bacteriol. 187, 5585–5594. 10.1128/JB.187.16.5585-5594.2005 [DOI] [PMC free article] [PubMed] [Google Scholar]
  63. Yamaguchi T., Nishifuji K., Sasaki M., Fudaba Y., Aepfelbacher M., Takata T. (2002). Identification of the Staphylococcus aureus etd pathogenicity island which encodes a novel exfoliative toxin, ETD, and EDIN-B. Infect. Immun. 70, 5835–5845. 10.1128/IAI.70.10.5835-5845.2002 [DOI] [PMC free article] [PubMed] [Google Scholar]
  64. Yamasaki O., Tristan A., Yamaguchi T., Sugai M., Lina G., Bes M., et al. (2006). Distribution of the exfoliative toxin D gene in clinical Staphylococcus aureus isolates in France. Clin. Microbiol. Infect. 12, 585–588. 10.1111/j.1469-0691.2006.01410.x [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Click here for additional data file. (84.6KB, XLSX)
Click here for additional data file. (73.8KB, XLSX)
Click here for additional data file. (184KB, DOC)

Articles from Frontiers in Microbiology are provided here courtesy of Frontiers Media SA

RESOURCES