LETTER
The prevalence of carbapenem-resistant Acinetobacter baumannii (CRAB) is increasing worldwide. There is not a regional study or national surveillance program in Mexico, but some recent reports include information from outbreaks at particular hospitals (1–4). This multicenter study described the sequence types (STs), clonal complexes (CCs), and carbapenem resistance mechanisms of A. baumannii clinical isolates with the carbapenem resistance phenotype from Mexican hospitals.
A total of 192 carbapenem-resistant Acinetobacter baumannii (CRAB) clinical isolates were collected from 16 hospitals between 2006 and 2013. Only one isolate per patient was included in the study. Identification of the isolates was performed by using the API20 NF (bioMérieux). The susceptibility of CRAB isolates to imipenem, meropenem, tigecycline, and colistin was determined by the microdilution method according to the CLSI recommendations (5) and EUCAST (www.eucast.org). All 192 CRAB isolates were resistant to imipenem and meropenem and susceptible to tigecycline and colistin. The genomic DNA macrorestriction profiles were determined by pulsed-field gel electrophoresis (PFGE) (6) and compared using the software package Gel Compare II (Applied Maths BVBA, Austin, TX, USA). In general, one different pulsotype was identified in each hospital. The genes for carbapenem hydrolysis class B metallo-β-lactamases (VIM, IMP, and NDM) and class D β-lactamases (CHDL) (blaOXA-51-like, blaOXA-23-like, blaOXA-24-like, and blaOXA-58-like) were screened by PCR. All of the isolates were negative for the metallo-β-lactamase carbapenemases and contained the blaOXA-51-like gene. The blaOXA-24-like gene was identified in 70/192 (36.4%) CRAB isolates, the blaOXA-23-like gene was identified in 57/192 (29.6%) isolates, and the blaOXA-58-like gene was identified in 23/192 (12%) isolates. None of the acquired CHDL genes were detected in 42/192 (21.8%) isolates. The CarbAcineto NP test (7) was performed on all 192 clinical isolates, and the results were positive in 80% and 75% of those CRAB isolates possessing blaOXA-23-like and blaOXA-24-like genes, respectively. Based on the PFGE results, blaOXA-type profile, and hospital origin, 22 representative CRAB isolates were selected for further analysis.
The partial rpoB gene sequence analysis (8) indicated that all 22 isolates corresponded to Acinetobacter baumannii. The genomic DNA macrorestriction profiles (PFGE) of the 22 CRAB isolates identified three major pulsotypes, each with 2 or 3 clinical isolates from different hospitals, 14 nonrelated pulsotypes, and one nontypeable isolate (see Fig. S1 in the supplemental material). Multilocus sequencing typing (MLST) was performed according to the Oxford system. Thirteen different STs were detected, 11 of which were previously reported and two of which were new STs (ST1046 and ST1091). These corresponded to two major clonal complexes: CC636 (previously CC113) in 13/22 (59%) isolates (ST758 was predominant) and CC92 (WWII) in 6/22 (27%) isolates (see Fig. S2). A regional distribution of the acquired CHDL was identified. In northern Mexico, blaOXA-72 (7/22 isolates, 31.8%) and blaOXA-58 (4/22 isolates, 18.1%) genes were associated with upstream ISAba3; meanwhile, in southern Mexico, the blaOXA-239 (blaOXA-23) (6/22 isolates, 27.3%) gene was associated with upstream ISAba1 and ISAba2 and the blaOXA-469 (1/22 isolates, 4.5%) gene, a novel variant of blaOXA-239 (T750G and M250I) (GenBank accession number KT006770), was associated with upstream ISAba2.
These results suggest a dissemination of blaOXA-type genes with different STs (Table 1). The STs in this study did not have a specific acquired CHDL, and the predominant clonal complexes corresponded to the Ibero-American CC636 and the global CC92 (see Fig. S2 in the supplemental material).
TABLE 1.
Characteristics of carbapenem-resistant A. baumannii clinical isolates
| Strain | Hospitala | Regiona | Isolation date (mo-yr) | Specimen typeb | PFGE type | ST (MLST) | Clonal complexc | blaOXA-type gene(s) | MIC (μg/ml)g |
|||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| IMP | MER | TIG | CL | |||||||||
| 8400 | 4 | MC | 08-2010 | BS | A | 758 | 636 | 51 | 4 | 8 | 0.03 | 0.06 |
| 9001 | 2 | MC | 05-2011 | BSF | C | 758 | 636 | 51, 239d | 32 | 32 | 0.06 | <0.015 |
| 7024 | 10 | MC | 05-2013 | CT | A | 758 | 636 | 51, 239d | 32 | 32 | 0.5 | 0.03 |
| 9736 | 11 | MC | 12-2013 | BS | J | 758 | 636 | 51, 239e | 16 | 32 | 0.125 | <0.015 |
| 8519 | 14 | MC | 02-2012 | RS | C | 758 | 636 | 51, 239d | 32 | 32 | 1 | <0.015 |
| 8404 | 4 | MC | 08-2011 | Blood | A1 | 758 | 636 | 51f, 239d | 8 | 16 | 0.03 | 0.03 |
| 10613 | 8 | S | 06-2013 | BS | I | 1091 | 636 | 51, 239d | 32 | 64 | 2 | <0.015 |
| 5840 | 6 | N | 12-2009 | Secretion | F | 758 | 636 | 51, 72 | 64 | >64 | 2 | 0.06 |
| 8200 | 7 | S | 08-2010 | Blood | K | 758 | 636 | 51, 72 | >64 | >64 | 0.062 | 0.015 |
| 10513 | 16 | N | 03-2012 | BSF | E | 758 | 636 | 51, 72 | >64 | >64 | 1 | 0.25 |
| 9201 | 12 | S | 08-2013 | Blood | R | 934 | 636 | 51, 72 | 64 | 64 | 0.125 | 0.125 |
| 7811 | 1 | N | 09-2006 | BALF | M | 762 | 636 | 51, 58f | 32 | 16 | 0.03 | <0.015 |
| 7835 | 1 | N | 07-2007 | Tissue | N | 1046 | 636 | 51, 58f | 32 | 8 | 0.03 | <0.015 |
| 9501 | 5 | S | 08-2011 | Blood | B | 417 | 92 | 51 | 16 | 16 | 0.5 | 1 |
| 6976 | 9 | N | 05-2013 | BS | H | 472 | 92 | 51 | 32 | 2 | 0.06 | <0.015 |
| 6972 | 9 | N | 05-2013 | BS | G | 369 | 92 | 51, 72 | >64 | >64 | 2 | 0.06 |
| 5831 | 6 | N | 12-2009 | Blood | Q | 417 | 92 | 51, 72 | 64 | 64 | 0.125 | 0.125 |
| 10045 | 15 | N | 11-2011 | Wound | O | 473 | 92 | 51, 72 | >64 | >64 | 125 | 0.25 |
| 7846 | 1 | N | 04-2007 | BSF | B | 208 | 92 | 51,f 58f | 16 | 8 | 0.125 | <0.015 |
| 9104 | 3 | N | 10-2010 | BS | P | 231 | 109 | 51 | 4 | 16 | 0.062 | <0.015 |
| 7804 | 1 | N | 07-2006 | BALF | L | 490 | 110 | 51, 58f | 8 | 16 | 0.062 | 0.03 |
| 10324 | 13 | S | 08-2012 | BS | D | 771 | Sg | 51, 469e | 4 | 8 | 1 | 0.5 |
Hospitals: 1, Hospital Universitario de Nuevo León; 2, Centro Médico Nacional 20 de noviembre/ISSSTE; 3, Hospital General de Tijuana; 4, CARD/IMSS/CMN/SXXI; 5, HI/IMSS/CMN Occidente; 6, Hospital General San Luis Potosí; 7, Hospital General de Uruapan; 8, Hospital General de Oaxaca; 9, Hospital Central Monterrey; 10, Hospital La Raza/IMSS; 11, Instituto Nacional de Cancerología; 12, Hospital Central Guadalajara; 13, Hospital General de Acapulco; 14, Oncología UMAE ONCO/IMSS/CMN/SXXI; 15, Unidad Médica de Alta Especialidad de Torreón; 16, Unidad Médica de Alta Especialidad de Ciudad Obregón, Sonora. Regions: MC, Mexico City; S, southern Mexico; N, northern Mexico.
BS, bronchial secretion; CT, catheter tip; BSF, brain spinal fluid; RS, rectal secretion; BALF, bronchoalveolar lavage fluid.
Sg, singleton.
ISAba1-OXA associated.
ISAba2-OXA associated.
ISAba3-OXA associated.
IMP, imipenem; MER, meropenem; TIG, tigecycline; CL, colistin.
The present study shows new data for carbapenemases and the clonal complex distribution of carbapenem-resistant A. baumannii clinical isolates from different hospitals, thereby providing a broader context in Mexico.
Supplementary Material
ACKNOWLEDGMENTS
We thank Rio Arronte for the equipment acquired.
All authors declare they have no financial or personal relationships with other people or organizations that could have inappropriately influenced their work.
The participants in the CRAB Study Group in Mexico include the following: E. Garza-González and G. M González, Hospital Universitario de Nuevo León; Juana Salazar, Centro Médico Nacional 20 de noviembre; J. A. Hurtado-Montalvo, Hospital General de Tijuana; A. Meza-Chávez and R. D. Diaz-Ramos, Cardiología/Centro Médico Nacional, Siglo XXI; A. Galicia and M. L. Perez-Carranco, Oncología/Centro Médico Nacional, Siglo XXI; R. Díaz Peña, Unidad Médica de Alta Especialidad, Pediatría/Centro Médico Nacional de Oriente; P. del C. Niño-Moreno, E. A. Turrubiates-Martínez, J. Tovar-Oviedo, and M. Magaña-Aquino, Hospital Central/San Luis Potosí; L. E. Loperena Contreras, Hospital General de Uruapan; N. E. Rivera Martínez and Q. S. Cruz Martínez, Hospital Regional de Alta Especialidad de Oaxaca; J. Ayala-Gaytan and C. E. Guajardo-Lara, Hospital San Juan Tecnológico de Monterrey; C. E. Santacruz Tinoco, Hospital La Raza/Centro Médico Nacional; Patricia Cornejo and Patricia Volkow, Instituto Nacional de Cancerología; R. Morfin-Otero and E. Rodriguez-Noriega, Hospital Civil de Guadalajara; A. Calderón, F. Jaimes-Domínguez, and B. González-Cervantes, Hospital General de Acapulco; J. A. Hurtado-Montalvo, Hospital General de Tijuana; M. R. González-Martínez and M. Vazquez-Farias, Unidad Médica de Alta Especialidad de Torreón; and R. Serrano-Osuna and A. L. Miranda-Romero, Unidad Médica de Alta Especialidad de Ciudad Obregón, Sonora.
Funding Statement
This work was funded by Consejo Nacional de Ciencia y Tecnología (CONACYT) through SEPCONACYT grant numbers 169867, 136339, 130224, and 205707. A.M.G.-V. was a Ph.D. fellow from CONACYT.
Footnotes
Supplemental material for this article may be found at http://dx.doi.org/10.1128/AAC.02042-15.
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