A Study on Secondary Bacterial Infections Associated with Dermatological Lesions and their Antimicrobial Susceptibility Pattern in a Tertiary Care Hospital

INTRODUCTION: Skin and soft-tissue infection is defined as an inflammatory microbial invasion of the epidermis, dermis and subcutaneous tissues. One common etiology of skin and soft tissue infection is the secondary bacterial infection that complicates the skin lesions. The dose, route and duration of the antimicrobial treatment in these patients are predicated with the knowledge of the potential pathogens with their antimicrobial sensitivity. This study was conducted at the Institute of Microbiology, Madras Medical college, Chennai , to isolate the pathogens from patients with secondarily infected skin lesions (Psoriasis, Atopic dermatitis, Pemphigus lesions and Leprosy with infected ulcer) from various sites and to determine their antimicrobial susceptibility pattern . MATERIALS AND METHODS: 200 patients (≥18 yrs) with signs and symptoms of secondary infection of skin lesions attending the department of Dermatology, Rajiv Gandhi Government General Hospital, Chennai were included in the study. Pus and blood samples were collected from these patients and processed by standard microbiological techniques. RESULT: Out of 200 samples 63, 62, 52 and 23 samples were taken respectively from Atopic Dermatitis/Eczema, Pemphigus, Psoriasis and Leprosy with infected ulcer, including 114 inpatiens and 86 outpatients. 88% of samples were positive for culture. Aerobic gram positive organisms accounts for 59.9% followed by aerobic gram negative 37.27% and anaerobic organisms 2.83%. In Atopic Dermatitis/Eczema 57.7% of isolates were Staphylococcus aureus followed by Streptococcus pyogenes, Enterobacteriacea and anaerobic organisms. Most common isolate in Psoriasis was Staphylococcus aureus (64%) followed by Enteric gram negative bacilli and Staphylococcus epidermidis. Pseudomonas aeroginosa (48%) was the most common organism in leprosy with infected ulcer followed by Proteus vulgaris (22%). Blood culture from17 in patients, [11 from Pemphigus (1.77%) and 6 from Psoriasis (1.15%)] resulted in MRSA isolation from two cases of Pemphigus. ESBL producers were 62.5%. All the ESBL producers were sensitive to Imipenem. 64% Staphylococcus aureus were MSSA and 36% were MRSA. All MRSA were positive for mec A gene .MRSA from OP patients (CA MRSA) showed higher positivity for Pvl gene 90% and 22% of MRSA from IP patients (HA MRSA) were positive for Pvl gene. All the Methicillin resistant Staphylococcus aureus were sensitive to vancomycin. CONCLUSION: MRSA with higher rate of resistance to many routinely used antibiotics and Enterobacteriaceae with higher levels of ESBL production were isolated. Hence bacterial culture and sensitivity of specimens from the secondarily infected skin lesions should be performed to confirm the bacterial etiology and to initiate effective antibiotic treatment so as to decrease the morbidity and mortality of these patients, that also limits the misuse of antimicrobials which would prevent the emergence of resistant bacterial strains in the hospital and the community