Abstract
The aim of the present retrospective single centre study was to define the changes in the microbiological flora of the recurring sacrococcygeal pilonidal sinus (PS). Microbiological findings of swab samples of abscess‐forming PS from 2000 to 2010 were evaluated. Within this time span, 73 swab samples were taken from primary sacrococcygeal pilonidal sinus (pPS) and 23 swab samples of patients with recurring sacrococcygeal pilonidal sinus (rPS). Our results show a statistically significant shift of the bacterial flora towards the gram‐positive range (P = 0·029) and a shift with tendency towards the aerobic range (P = 0·090). Pathogens of pPS are not always solely anaerobic or gram‐negative, and those of rPS not always aerobic or gram‐positive. Therefore, antibiosis preceding microbiological examination should cover both the aerobic and anaerobic bacteria as well as the gram‐positive and the gram‐negative spectrum.
Keywords: Abscess‐forming, Microbiology, Pilonidal sinus, Sacrococcygeal, Surgical site infection
Introduction
Sacrococcygeal pilonidal sinuses (PSs), which may present as asymptomatic, acute abscess‐forming or chronic subcutaneous inflammation in the sacrococcygeal region 1, predominantly affect young adults 2. It is generally assumed that Mayo first described this condition in 1833 3. Hodges suggested the term pilonidal sinus (PS) in 1880 4.
A PS has been postulated to be caused by barbed hair being pushed deep into the skin of the natal cleft, which results in forked fistula tracks 1, 5. Subsequently, a foreign‐body reaction (including partial epithelialisation of skin) results in chronic fistulae or inflammation 6. A genetic predisposition has also been proffered as a cause of a PS 7
In addition to incision, excision, the Karydakis 8, Limburg flap 9 and Bascom procedures 10 and marsupialisation 11, a variety of other surgical techniques have been described. Non‐surgical treatments, such as application of phenol 12 and minimally invasive procedures involving pit‐picking 13 or endoscopic interventions have also been reported 14. However, no standard therapy has yet been established 15, 16. Depending on the surgical procedure, the recurrence rates are high: up to 42% 17.
Surgical site infections (SSI), the commonest complications of PS surgery, lead to longer hospital stays, chronic pain and recurrence rate 18, 19. Apart from SSI, complications such as sacrococcygeal or lumbar osteomyelitis with epidural abscess 20 and a life‐threatening myonecrosis after excision of an infected PS with primary midline closure 21 have been reported. However, only a few studies are available regarding the microbiology of sacrococcygeal PS and their antibiotic treatment. Thus, there is no standard antibiotic therapy or prophylaxis 22. A recently published review found no evidence for any significant advantages of single‐dose antibiotic treatment versus no prophylaxis 22. The use of gentamicin sponges in patients with PS also reportedly confers no advantage 22.
The largest study evaluating the microbiology of sacrococcygeal PS disease was reported by Brook in 1989 23. Recurrences of PS were not assessed in that study.
Therefore, the aim of this study was to evaluate the microbiological flora of primary sacrococcygeal pilonidal sinuses (pPSs) and to compare it with that of recurring sacrococcygeal pilonidal sinuses (rPSs) in adult patients.
Materials and methods
Reports of microbiological findings from swab samples of abscess‐forming PS between 2000 and 2010 were evaluated retrospectively. The microbiological examinations had been performed by the Department of Microbiology of the University Hospital, Jena.
A total of 73 swab samples had been taken from patients with pPS and 23 from patients with rPS as follows.
After the surgical sites had been disinfected with an alcohol solution of 1% povidone‐iodine, intraoperative swab samples of the opened abscesses were obtained with cotton‐tipped swabs. These were then Gram stained and evaluated microscopically, applied to adequate culture mediums and cultivated according to DIN EN ISO/IEC 17025 guidelines 24 in the Department of Microbiology of the University Hospital, Jena.
In order to assess aerobic and facultative anaerobic bacteria, Columbia blood agar and Winkle agar plates were inoculated. Samples with low plate counts on these media were cultivated in Brain–Heart infusion broth for 24 hours before inoculation. Evaluations were performed after 18, 24 and 48 hours.
Schaedler agar plates with and without vancomycin/kanamycin were inoculated to evaluate anaerobic bacteria and to grow Bacteroides and Prevotella species selectively. These were assessed after 96 hours unless plump, large Gram‐positive rods suggestive of Clostridia had been detected on Gram staining of the original sample, in which case they were assessed only after 24 hours.
A Vitek2 (BioMérieux, Lyon, France) automatised system was used to identify the individual species in pure cultures.
Staphylococcus aureus was identified by a plasma coagulase test and beta‐haemolytic Streptococci into Groups A and B by antibody‐agglutination according to the Lancefield method.
The isolates were categorised as anaerobic or aerobic/facultative anaerobic bacteria, as well as based on negative or positive Gram staining.
Statistical procedures
The data were collected with FileMaker Pro 10 and data analyses performed using SPSS® software, version 21 (SPSS®, Chicago, IL). Kolmogorov–Smirnov and Shapiro–Wilk tests were performed to verify Gaussian distribution. The significance of differences between pPS and rPS and between Gram‐positive and Gram‐negative isolates and among the summarised genera was then determined either by the Mann–Whitney U‐test or Fisher's exact test. A P‐value of less than 0·05 was considered statistically significant. In addition, Pearson correlations of genera with each other and with selected patient characteristics were performed.
Results
A total of 96 swab samples were obtained from infected PS, 23 from rPS and 73 from pPS. None of the patients had been treated with antibiotics prior to surgery.
pPS group
In the pPS group, the median patient age was 23 years (range: 16–67 years), ratio of male to female 55:18, and median body mass index (BMI) 25·5 (range: 19·0–41·8). There were 40 smokers (exceeding 1 pack year), 23 non‐smokers and 10 patients for whom smoking data were not available. The median duration of hospital stay was 2 days (range: 1–21 day; Table 1). A total of 65 excisions with open granulation, five midline excisions with primary suturing, one excision with secondary suturing 9 days later, one excision with the use of a vacuum‐assisted system and one rhomboid excision and Limberg flap had been performed.
Table 1.
Patient's characteristics
| All cases, N = 96 | Patients with pPS, N = 73 | Patients with rPS, N = 23 | P value comparing patients with pPS and rPS | |
|---|---|---|---|---|
| Age | 24·0 (20·0, 27·0) | 23·0 (20·0, 26·0) | 27·0 (20·0, 35·0) | 0·191 |
| Sex: female | 22 (22·9) | 18 (24·7) | 4 (17·4) | 0·472 |
| Smoker | 59 (68·6) | 40 (63·5) | 19 (82·6) | 0·093 |
| BMI | 26·0 (23·2, 29·0) | 25·5 (22·7, 28·9) | 26·7 (24·4, 29·4) | 0·274 |
| Duration of hospital stay in days | 2·0 (2·0, 3·0) | 2·0 (2·0, 3·0) | 3·0 (1·0, 5·0) | 0·201 |
Descriptive statistics as N (%), or median (interquartile range). P values obtained by Mann–Whitney U‐test or Fisher's exact test as appropriate. pPS, primary sacrococcygeal pilonidal sinus; rPS, recurrent sacrococcygeal pilonidal sinus; BMI, body mass index.
Of the pPS swab samples, 62/73 (84·93%) showed bacterial growth, the total number of identified bacterial isolates being 168. Among anaerobic bacteria, Veillonella spp. was predominant (21·92%), followed by Peptostreptococcus spp. (16·44%). Coagulase‐negative Staphylococci (15·07%) were predominant among the aerobic bacteria. The ratio of anaerobic to aerobic bacteria was 107:61 (Table 2).
Table 2.
Bacterial isolates for 73 infected primary pilonidal sinus
| Anaerobic | N a | %a | Aerobic and facultative bacteria | N a | %a | |
|---|---|---|---|---|---|---|
| Gram‐negative | Bacteroides spp. | 4 | 5·48% | Escherichia coli | 4 | 5·48% |
| Bacteriodes merdae | 2 | 2·74% | Pantoea agglomerans | 1 | 1·37% | |
| Bacteriodes thetaiotaomicron | 1 | 1·37% | Campylobacter rectus | 1 | 1·37% | |
| Bacteriodes vulgatus | 2 | 2·74% | Proteus mirabilis | 2 | 2·74% | |
| Bacteroides eggerthii | 1 | 1·37% | Proteus vulgaris | 1 | 1·37% | |
| Bacteroides fragilis | 7 | 9·59% | ||||
| Bacteroides miformis | 1 | 1·37% | ||||
| Fusobacterium spp. | 9 | 12·33% | ||||
| Fusobacterium nucleatum | 6 | 8·22% | ||||
| Porphyromonas asaccharolytica | 2 | 2·74% | ||||
| Porphyromonas gingivalis | 4 | 5·48% | ||||
| Prevotella bivia | 4 | 5·48% | ||||
| Prevotella buccae | 3 | 4·11% | ||||
| Prevotella dentalis | 2 | 2·74% | ||||
| Prevotella disiens | 3 | 4·11% | ||||
| Prevotella intermedia | 8 | 10·96% | ||||
| Prevotella oralis | 8 | 10·96% | ||||
| Veillonella spp. | 16 | 21·92% | ||||
| Gram‐positive | Actinomyces meyeri | 1 | 1·37% | Capnocytophaga spp. | 3 | 4·11% |
| Bifidobacterium spp. | 3 | 4·11% | Corynebacterium spp. | 5 | 6·85% | |
| Clostridium spp. | 1 | 1·37% | Enterococcus spp. | 2 | 2·74% | |
| Peptococcus spp. | 3 | 4·11% | Gemella hämolysans | 1 | 1·37% | |
| Peptostreptococcus spp. | 12 | 16·44% | Micrococcus spp. | 1 | 1·37% | |
| Peptostreptococcus anaerobius | 3 | 4·11% | coagulase‐negative Staphylococci | 11 | 15·07% | |
| Peptostreptococcus prevoti | 1 | 1·37% | Staphylococcus epidermidis | 7 | 9·59% | |
| Staphylococcus saprophyticus | 3 | 4·11% | ||||
| Staphylococcus aureus | 2 | 2·74% | ||||
| alpha‐haemolytic Streptococci | 3 | 4·11% | ||||
| beta‐haemolytic Streptococci | 6 | 8·22% | ||||
| Streptococcus agalagticae | 1 | 1·37% | ||||
| Streptococcus Group C | 4 | 5·48% | ||||
| Streptococcus anginosus | 2 | 2·74% | ||||
| Streptococcus constellatus | 1 | 1·37% | ||||
| Total | 107 | 61 | ||||
| Ratio | 1·75 | : | 1 |
Per 73 swab samples.
Of the positive swab samples in the pPS group, 17 yielded only aerobic bacteria, 20 only anaerobic bacteria and 25 both groups of bacteria. Swab samples yielding only aerobic bacteria had a mean of 1·35 ± 0·61 bacterial isolates per swab sample, those yielding only anaerobic bacteria 2·53 ± 1·22 and those with mixed bacterial growth 3·73 ± 1·64.
rPS group
In the group of 23 patients with rPS, 20 swab samples (86·96%) showed bacterial growth, 16 of these cases were first recurrences, 3 second recurrences, 1 a third recurrence and 2 fourth recurrences. A 39‐year‐old woman was unable to recall precisely how many recurrences she had experienced, but estimated this to be 10.
The median age of patients with recurrences was 27 years (range: 16–62 years), ratio of male to female 19:4, and median BMI 26·7 (range: 20·0–37·5). There were 18 smokers (exceeding 1 pack year), 4 non‐smokers and one patient for whom smoking data was not available. The median duration of these patients' hospital stay was 5·04 days (range: 1–28 days; Table 1). In these patients, 22 excisions with open granulation and one with midline closure had been performed.
The surgical procedures that had been followed by recurrences consisted of 16 excisions, 5 incisions, 1 rhomboid excision with Limberg flap and 1 incision with insertion of a drain.
Nine recurrences occurred within 6 months, three after 1 year, another seven within 2–6 years and four after more than 10 years (10–14 years). Notably, all three swab samples that failed to yield bacterial growth were from early rPS.
In all, 58 bacterial isolates were identified from the 20 swab samples yielding bacterial growth. Among the anaerobic bacteria, Fusobacterium spp. and Veillonella spp. dominated with 21·74% each, followed by Prevotella oralis and Peptostreptococcus with 17·39% each. Among the aerobic/facultative anaerobic bacteria, coagulase‐negative Staphylococci predominated, accounting for 15·07% (Table 3).
Table 3.
Bacterial isolates for 23 infected recurrent pilonidal sinus
| Anaerobic | N a | %a | Aerobic and facultative bacteria | N a | %a | |
|---|---|---|---|---|---|---|
| Gram‐negative | Bacteroides fragilis | 1 | 4·35% | Escherichia coli | 1 | 4·35% |
| Fusobacterium spp. | 5 | 21·74% | ||||
| Fusobacterium nucleatum | 2 | 8·70% | ||||
| Porphyromonas asaccharolytica | 1 | 4·35% | ||||
| Porphyromonas gingivalis | 1 | 4·35% | ||||
| Prevotella spp. | 1 | 4·35% | ||||
| Prevotella buccae | 1 | 4·35% | ||||
| Prevotella intermedia | 1 | 4·35% | ||||
| Prevotella oralis | 4 | 17·39% | ||||
| Veillonella spp. | 5 | 21·74% | ||||
| Gram‐positive | Peptococcus spp. | 1 | 4·35% | Capnocytophaga spp. | 1 | 4·35% |
| Peptostreptococcus spp. | 4 | 17·39% | Corynebacterium spp. | 3 | 13·04% | |
| Peptostreptococcus anaerobius | 1 | 4·35% | Enterococcus spp. | 1 | 4·35% | |
| Probionibacterium spp. | 1 | 4·35% | Enterococcus faecalis | 1 | 4·35% | |
| Propionibacterium propionicus | 1 | 4·35% | coagulase‐negative Staphylococci | 6 | 26·09% | |
| Staphylococcus epidermidis | 2 | 8·70% | ||||
| Staphylococcus saprophyticus | 1 | 4·35% | ||||
| Staphylococcus aureus | 2 | 8·70% | ||||
| alpha‐haemolytic Streptococci | 1 | 4·35% | ||||
| beta‐haemolytic Streptcocci | 2 | 8·70% | ||||
| non‐haemolytic Streptococci | 3 | 13·04% | ||||
| Streptococcus anginosus | 1 | 4·35% | ||||
| Streptococcus constellatus | 3 | 13·04% | ||||
| Total | 30 | 28 | ||||
| Ratio | 1·07 | : | 1 |
Per 23 swab samples.
The ratio of anaerobic to aerobic bacteria was 30:28 (Table 3). In 6 swab samples, only aerobic/facultative anaerobic bacteria were found, another 3 yielded anaerobic bacteria only and 11 yielded both. The swab samples yielding only aerobic bacteria had a mean of 1·33 ± 0·52 bacterial isolates per swab sample, those yielding only anaerobic bacteria 2·33 ± 1·15 and those with mixed bacterial growth 3·91 ± 1·14 bacterial isolates.
Because there were swab samples from both pPS and rPS in only three patients, no statistical analysis of these data were possible.
Pearson correlation of isolates grouped according to genus (Bacteroides, Fusobacterium, Prevotella, Peptostreptococcus, Veillonella, Propionibacterium, Porphyromonas, Peptococcus, Streptococcus, Staphylococcus, Corynebacterium, Escherichia, Enterococcus and Proteus) showed no significant correlations with genus or selected patient characteristics.
The ratio of anaerobic to aerobic/facultative anaerobic bacteria was 1·75:1 in the pPS group and 1·07:1 in the rPS group (P = 0·090; Tables 2, 3, 4). After excluding Staphylococci as a possible source of contamination via bacterial skin flora, there was still a trend towards a greater proportion of anaerobes in the pPS group: 2·82:1 in the pPS group and 1·76:1 in the rPS patients (P = 0·092).
Table 4.
Bacterial characteristics
| All swab samples, N = 96 | Swab samples from pPS, N = 73 | Swab samples from rPS, N = 23 | P value comparing pPS and rPS | |
|---|---|---|---|---|
| Positive culturea | 82 (85·4) | 62 (84·9) | 20 (87·0) | 0·881 |
| Swab samples with anaerobic isolates onlya | 23 (24·0) | 20 (27·4) | 3 (13·0) | 0·960 |
| Swab samples with aerobic isolates onlya | 24 (25·0) | 18 (24·7) | 6 (26·1) | 0·161 |
| Swab samples with mixed culturesa | 35 (36·5) | 24 (32·9) | 11 (47·8) | 0·196 |
| Found isolatesa | 226 (100) | 168 (74·3) | 58 (25·7) | 0·158 |
| Anaerobic isolatesb | 0·809 | |||
| 0 anaerobic isolate per swab sample | 38 (39·6) | 29 (39·7) | 9 (39·1) | |
| 1 anaerobic isolate per swab sample | 16 (16·7) | 11 (15·1) | 5 (21·7) | |
| 2 anaerobic isolates per swab sample | 18 (18·8) | 15 (20·5) | 3 (13·0) | |
| 3 anaerobic isolates per swab sample | 15 (15·6) | 10 (13·7) | 5 (21·7) | |
| 4 anaerobic isolates per swab sample | 5 (5·2) | 4 (5·5) | 1 (4·3) | |
| 5 anaerobic isolates per swab sample | 4 (4·2) | 4 (5·5) | 0 (0) | |
| Aerobic isolatesb | 0·090 | |||
| 0 aerobic isolate per swab sample | 37 (38·5) | 31 (42·5) | 6 (26·1) | |
| 1 aerobic isolate per swab sample | 37 (38·5) | 28 (38·4) | 9 (39·1) | |
| 2 aerobic isolates per swab sample | 16 (16·7) | 10 (13·7) | 6 (26·1) | |
| 3 aerobic isolates per swab sample | 4 (4·2) | 3 (4·1) | 1 (4·3) | |
| 4 aerobic isolates per swab sample | 2 (2·1) | 1 (1·4) | 1 (4·3) | |
| Gram‐positive isolatesb | 0·029 | |||
| 0 gram‐positive isolate per swab sample | 32 (33·3) | 28 (38·4) | 4 (17·4) | |
| 1 gram‐positive isolate per swab sample | 32 (33·3) | 25 (34·2) | 7 (30·4) | |
| 2 gram‐positive isolates per swab sample | 20 (20·8) | 12 (16·4) | 8 (34·8) | |
| 3 gram‐positive isolates per swab sample | 10 (10·4) | 6 (8·2) | 4 (17·4) | |
| 4 gram‐positive isolates per swab sample | 1 (1·0) | 1 (1·4) | 0 (0) | |
| 5 gram‐positive isolates per swab sample | 1 (1·0) | 1 (1·4) | 0 (0) | |
| Gram‐negative isolatesb | 0·498 | |||
| 0 gram‐negative isolate per swab sample | 38 (39·6) | 28 (38·4) | 10 (43·5) | |
| 1 gram‐negative isolate per swab sample | 23 (24·0) | 18 (24·7) | 5 (21·7) | |
| 2 gram‐negative isolates per swab sample | 18 (18·8) | 12 (16·4) | 6 (26·1) | |
| 3 gram‐negative isolates per swab sample | 13 (13·5) | 11 (15·1) | 2 (8·7) | |
| 4 gram‐negative isolates per swab sample | 3 (3·1) | 3 (4·1) | 0 (0) | |
| 5 gram‐negative isolates per swab sample | 1 (1·0) | 1 (1·4) | 0 (0) | |
| Bacteroides isolatesb | 0·069 | |||
| 0 Bacteroides isolate per swab sample | 80 (83·3) | 58 (79·5) | 22 (95·7) | |
| 1 Bacteroides isolate per swab sample | 14 (14·6) | 13 (17·8) | 1 (4·3) | |
| 2 Bacteroides isolates per swab sample | 1 (1·0) | 1 (1·4) | 0 (0) | |
| 3 Bacteroides isolates per swab sample | 1 (1·0) | 1 (1·4) | 0 (0) |
Descriptive statistics as N (%). pPS, primary sacrococcygeal pilonidal sinus; rPS, recurrent sacrococcygeal pilonidal sinus.
P values obtained by Fisher's exact test.
Variables on isolates per swab were considered as having ordinal scaling, differences between groups tested by Mann–Whitney U‐test.
In the pPS group, there were 76 Gram‐positive bacterial isolates and in the rPS group 35 (P = 0·029).
Among the genus groups, only the proportions of Bacteroides (including Bacteroides spp., Bacteroides merdae, Bacteroides thetaiotaomicron, Bacteroides vulgatus, Bacteroides eggerthii, Bacteroides fragilis and Bacteroides uniformis) differed tendencially between the pPS and rPS groups (Table 4). In all, 18 Bacteroides isolates were found in the pPS group, consistent with findings of other studies. However, in the rPS group, only one Bacteroides isolate was detected.
No other findings regarding genus were statistically significant or showed interesting tendencies.
Discussion
In this study, we identified differences in bacterial flora between pPS and rPS. There was a statistically significant greater proportion of Gram‐positive bacteria and a trend towards a greater proportion of aerobic/facultative anaerobic bacteria in patients with rPS than in those in pPS. In addition, we identified tendencially fewer bacteria of Bacteroides genus in the rPS group.
In this study, the frequency of bacterial growth in swab samples was comparable in patients with pPS (84·93%) and rPS (86·96%), which is in accordance with the findings of Khan et al. (80·00%) 25. Many studies have reported a predominance of anaerobic bacteria in aspirates and swab samples from patients with pPS, reported genera including Bacteroides, Clostridium, Fusobacteria and Prevotella 23, 26, 27, 28, 29 Our findings confirm the predominance of anaerobic bacteria in pPS. The anatomical proximity of sacrococcygeal PSs to the anus likely explains the similarity between bacterial flora of pPS and gut flora 30. In contrast, the predominant bacterial flora of rPS have not so far been reported. However, in this study, we have shown differences in bacterial flora between pPS and rPS.
In our study, there was a tendency towards a predominance of aerobic/facultative anaerobic bacteria in patients with rPS. In a double‐blinded randomised study of 103 patients, Sondenaa et al. identified a similar predominance of aerobic bacteria in post‐surgical aspirates, regardless of prior antibiotic prophylaxis 29.
We also showed a statistically significant greater proportion of Gram‐positive bacteria in the microbiological flora of rPS than of pPS. This is remarkable, given that the most severe complications of surgery for PS are attributable to Gram‐positive and facultative anaerobic/aerobic bacteria and skin and soft tissue infections are particularly associated with Gram‐positive bacteria. An analysis of over 5000 skin abscesses showed that Gram‐positive bacteria are the commonest cause of complex skin and skin structure infections 31. According to another study, mixed Gram‐positive/Gram‐negative infections are responsible for greater treatment costs and longer hospital stays than other bacterial infections 31.
S. aureus has been identified as a cause of epidural abscesses associated with rPS 20. Moreover, life‐threatening streptococcal myonecrosis after PS surgery has been reported 21. In the few case reports of complications of PS, aerobic/facultative anaerobic and Gram‐positive bacteria were responsible
Currently, there are no established guidelines for antibiotic treatment of sacrococcygeal PS 22. According to previously published studies, single‐dose antibiotic treatment with cefoxitin versus no antibiotic treatment did not differ significantly in their impact on recurrence rate and wound infection 19, 29. In addition, only minor advantages of single‐dose antibiotic treatment with clindamycin over no antibiotic treatment have been reported by others 26. Nevertheless, a relationship between wound infection and recurrence rate has been demonstrated 19. Bacteria that infect PS are reportedly sensitive to metronidazole because of the predominance of anaerobic bacteria 23, 28, 32. In a study with 50 patients who underwent excision of a PS and midline closure, Chaudhuri et al. compared single‐dose antibiotic treatment with solely metronidazole with cefuroxime plus metronidazole followed by amoxicillin/clavulanic acid for 5 days and found the latter treatment to be superior 31. In addition, in another study with 100 patients metronidazole in combination with erythromycin resulted in significantly more rapid healing of open wounds after excisions compared with no antibiotic therapy or metronidazole alone 27.
Several authors have investigated whether insertion of a gentamicin sponge reduces the incidence of SSI 33, 34, 35, 36, 37 and rPS. Mavros et al. performed a systemic review of these studies and found no evidence of benefit from such sponges 22. Based on our findings of a predominance of Gram‐positive bacteria in rPS and the predominant Gram‐negative range of gentamicin, there does not seem to be an indication for the use of gentamicin sponges alone. Nevertheless, systemic antibiotic therapy may be beneficial for treatment of wound infection and prevention of rPS.
One limitation of our study is that we cannot provide the number of cases of suspected Clostridia infection because only proven cases were recorded.
We found a significantly greater proportion of Gram‐positive bacteria and a trend towards a greater proportion of aerobic/facultative anaerobic bacteria in the rPS than in the pPS group.
We found that pPS are characteristically infected with a mixture of organisms, predominantly anaerobic, Gram‐negative bacteria, probably because these infections are caused by intestinal flora because of the anatomical proximity to the anus. However, in our study, infection of rPS was predominant with aerobic/facultative anaerobic bacteria, as is true of skin flora 38. Therefore, peri or postoperative antibiosis in patients with PS should also cover aerobic and Gram‐positive bacteria. A combination of metronidazole with a β‐lactam antibiotic, such as penicillin, ampicillin or cephalosporins, should be administered to cover this spectrum and prevent SSI. Published reports suggest that such antibiotic treatment should not be administered as a perioperative single dose but for several days. Further studies are required to investigate the impact of such a regime on SSI and recurrence rate.
Even optimal antibiosis will probably not reduce the rate of rPS disease; however, it may reduce the incidence of complications such as SSI, osteomyelitis or epidural abscess. Prospective studies are required to determine this.
Conclusion
Abscess‐forming PS should be subject to microbiological examination in order to facilitate early antibiotic responses to potential complications such as SSI, osteomyelitis and so on. Patients with pPS tend to have mixed infection with a predominance of anaerobic and Gram‐negative bacteria, whereas those with rPS have a predominance of aerobic/facultative anaerobic and Gram‐positive bacteria. Therefore, antibiosis initiated prior to microbiological examination should cover both aerobic and anaerobic bacteria as well as Gram‐positive and Gram‐negative bacteria.
Author contribution
AM developed the study conception and design, and performed data acquisition. Analysis and interpretation of data was performed by AM, KR., RJ, SB, SH and SU. AM and KR drafted the manuscript. Critical revision of manuscript was provided by SH and SU.
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