Bacteriological study of pyodermas in a tertiary care dermatological center.

BACKGROUND: Bacterial skin infection especially Pyoderma, commonly caused by Staphylococcus aureus and group A Streptococci, is quite common in Indian dermatology clinics. Despite a number of new antibiotics, the incidence of bacterial resistance is rising. AIM: To find out causative organisms and their latest antibiotic susceptibility patterns in pyodermas.
MATERIALS AND METHODS: All in-patients admitted in the Dermatology wards in Government Medical College, Amritsar were screened over 18 months and those with erosive skin lesions and/or purulent discharge were included in the study and swabs were sent for culture and sensitivity.
RESULTS: Majority 49/61 cases (80.33%) comprised of secondary pyodermas while primary pyodermas constituted only 12/61 cases (19.67%). Single organism was isolated in 49 cases (80.33%). More than one type of organism was isolated in 3 cases (4.92%) while none could be isolated from 9 (14.75%) cases. Staphylococcus aureus spp. was the commonest organism isolated in 36 (59.01%) cases and out of these, coagulase positive strains were found to be highly susceptible to amikacin (21cases-100%). Coagulase negative strains were sensitive to amikacin (7 cases-77.7%) and gentamycin (6 cases-66.6%) respectively.
CONCLUSION: This study gives an indication of the present pattern of bacteriological profile of pyodermas in a tertiary care hospital in north-west India. In-vitro testing is essential as knowledge of the causative organisms and resistance patterns can help us select appropriate antibiotics without wasting time in using resistant drugs.

Introduction

Pyodermas are quite common in India and constitute a major portion of the cases in dermatology clinics. Many cases these days do not respond to the antibiotics that were previously very effective in such cases. Perhaps, indiscriminate use of topical and systemic antibiotics has contributed to this situation.[1-4] The emergence of antibiotic resistance has significantly eroded the utility of established antibiotics and poses a serious threat to public health worldwide. In order to successfully treat cases of pyodermas, detailed knowledge is necessary regarding the various causative organisms and their sensitivity patterns. Considering these aspects, the present study was an attempt to find out the causative organisms and their antibiotic susceptibility patterns in different cases of primary and secondary pyodermas admitted in the dermatology wards in a tertiary care hospital.

Materials and Methods

All patients admitted in dermatology wards of a tertiary hospital in north-west India from January 2009 to August 2010 were screened for pyogenic skin infections of both primary and secondary types. Only those who had erosive skin lesions with exudative or purulent discharge were included in the study. Sixty-one patients of various ages and both sexes were identified for inclusion in the study; these included patients from urban as well as rural backgrounds. Sterile swabs were used to aseptically collect exudate or pus from the lesions. Care was taken that these samples were collected before the start of antibiotic therapy. The swabs were transported immediately to the microbiology laboratory for culture and sensitivity examination.

Results and Observation

The demographic characteristics of the patients enrolled in the study are shown in Table 1.

Table 1

Demographic characteristics of the study cases (n=61)

Primary bacterial skin infections (primary pyoderma) accounted for 12 (19.67%) cases while 49 (80.33%) cases were of secondary pyoderma. Among the primary pyodermas, impetigo was the commonest entity seen (nine cases-14.75%); among the secondary pyodermas, secondarily infected pemphigus vulgaris was the commonest, being seen in 24 cases (39.34%) [Table 2].

Table 2

Distribution of cases of primary and secondary pyoderma

A single infecting organism was isolated from 49 (80.33%) cases, more than one type of organism from three cases (4.92%) and no organism from nine cases (14.75%). Coagulase positive methicillin-sensitive (MS) Staphylococcus was isolated from 21 (34.4%) cases, coagulase positive methicillin resistant (MR) Staphylococcus in five (8.2%) cases, coagulase negative MS Staphylococcus in nine (14.75%) cases, coagulase negative MR Staphylococcus in one (1.64%) case. Thus, overall there were 36 (59%) cases of Staphylococcus spp., which included six (9.84%) cases of methicillin resistant Staphylococcus (MRSA). Out of these 36 cases, coagulase positive Staphylococcus accounted for 26 (42.62%) cases and coagulase negative Staphylococcus accounted for 10 cases (16.39%). The second most common organism isolated was Klebsiella Spp. (three-4.91%), Streptococcus, Enterococcus and E.coli+Enterococcus were isolated in two patients (3.28%) each [Table 3].

Table 3

Pattern of microorganisms isolated from cases of pyodermas

Among the S. aureus strains, susceptibility to antibiotics was as follows: amikacin- (21 strains-100%), gentamycin-(14 strains-66%), ciprofloxacin-(11 strains-52.4%) and gatifloxacin (9 strains-42.8%) [Table 4].

Table 4

Antibiotics susceptibility and resistance pattern of organisms isolated

Discussion

In all, we had 61 cases of pyoderma in this study. There were 12 (19.67%) cases of primary pyoderma, of which 9 cases were of impetigo. Impetigo formed the largest group followed by carbuncle and folliculitis. Similar high incidence of impetigo has been reported by others.[15] In our study, primary pyoderma constituted only 19.67% cases. This low incidence of primary pyoderma was probably because our study included only those patients who were admitted as inpatients for treatment of some other problem, and also because a large number of patients of primary pyoderma reporting in the outpatient department were not included in the study. Males were affected more than females in this study, as has also been reported by others.[46-9] Among the secondary pyodermas, infected pemphigus vulgaris was the commonest diagnosis, followed by Stevens-Johnson syndrome (SJS). Infected pemphigus (vulgaris + foliaceus), with a total of 24 cases (39.34%) was the commonest diagnosis among all cases of pyoderma; second commonest diagnosis was impetigo- nine cases (14.75%) and this was followed by SJS (eight cases-13.11%).

In bacteriological analysis, we observed that Staphylococcus spp. (36 cases-59.01%) were the most common organisms to be isolated; this included MRSA- which was isolated in six cases (9.83%). A similar high incidence of MRSA has been reported in other studies.[236810] Among the Staphylococcal strains isolated 26 (42.62%) were coagulase positive and 10 (16.39%) were coagulase negative. A high incidence of coagulase positive Staphylococcus in pyoderma has been reported by several workers.[2-4] Coagulase negative strains have also been reported to be etiological agents.[311] S. aureus and Streptococci are considered to be the main etiological agents of cutaneous bacterial infections[12] and these have been isolated in different proportions of cases in studies in India and abroad.[2679101314] The other organisms isolated in this study were Klebsiella in three (4.92%) patients, Streptococcus, Enterococcus and Proteus in two patients each (3.27% each) and Citrobacter and E.coli in one patient each (1.64%). A combination of Staphylococcus + Streptococcus was found in one case (1.64%), and combinations of Staphylococcus + Enterococcus and E. coli + Enterococcus in two patients each (3.28% each). Culture results were negative in nine patients (14.75%), which is similar to the studies by Baslas et al (negative culture results in 14.9%) and Rahul et al (negative culture results in 16.3%).[815]

The antibiotic susceptibility patterns of the various isolates is shown in Table 4 and comparisons between different studies are shown in Table 5.

Table 5

Overview of different organisms isolated and their sensitivity patterns in various studies

In this study most of coagulase positive strains of Staphylococcus were susceptible to amikacin (21 cases-100%), gentamycin (14 cases-66%) and ciprofloxacin (11 cases-52.4%). Coagulase negative Staphylococci were largely susceptible to amikacin (seven cases-77.7%) and gentamycin (six cases-66.6%) but showed relatively low susceptibility to ampicillin (five cases-55.5%), erythromycin (four cases-44.4%) and gatifloxacin (three cases-33.3%). Klebsiella was sensitive to amikacin (three cases-75%), gentamycin (two case-50%), ciprofloxacin (two cases-50%), and cefotaxime (two cases-50%) but showed relatively low susceptibility to gatifloxacin (one case-25%) and cephlexin (one case-25%). Most of the strains were found to be resistant to one or more antibiotics.[236811] Most of the coagulase positive Staphylococcus strains were resitant to erythromycin and gatifloxacin (eight cases each-38.1%), ampicillin (seven cases-33%) and cephalexin (six cases-28%). Klebsiella spp. were resistant to ceftriaxone, ciprofloxacin, cefotaxime and cephalexin [two cases (50%) each]. Streptococci were sensitive to ampicillin, erythromycin, cephalexin, ciprofloxacin, gatifloxacin, linezolid in two cases (100%) each while sensitivity to gentamycin and amikacin was seen in one case (50%) each. Most of organisms were highly sensitive to the newer antibiotics while showing low susceptability or resistance to the conventional antibiotics.[28101416]

Conclusions

This study gives an indication of present pattern of bacterial infections in pyodermas. Multidrug resistance has become a clinical challenge. Most of the bacterial strains were found to be resistant to one or more antibiotics. With knowledge of the likely causative organisms and their resistance patterns, the most suitable antibiotic therapy can be started without waiting for anti biogram results, and thus help avoid unnecessary medication with ineffective drugs.