Susceptibility profile of aerobic bacterial isolates in cellulitis and necrotizing fasciitis in a tertiary care hospital -A syndromic antibiogram

Background: Cellulitis and Necrotizing fasciitis (NF) are fulminant soft tissue infections that require timely diagnosis, surgical debridement and appropriate antimicrobial therapy.Objectives: This study aims to determine the bacteriological profile, susceptibility pattern of cellulitis and NF and to provide a Syndromic Antibiogram, guiding empirical therapy based on the likely bacterial isolate.Materials and Methods: A cross-sectional study was carried out at Tertiary care Hospital, Chennai, from February 2024 to January 2025. A total of 250 pus samples from patients diagnosed to have cellulitis and NF sent to the microbiology laboratory were processed using standard protocols. A syndromic antibiogram was prepared for specific bacterial isolates from patients with cellulitis and NF. Data were analysed using Chi square test and SPSS version 28.0.Results: A total of 250 patients were included in the study, comprising 174 (70%) males, and 75(30%) females. Among them, 61.8% were diagnosed with cellulitis, predominantly caused by gram positive cocci (47.3%) followed by Enterobacteriaceae (38.8 %) and non-fermenters (13.8%). The remaining 39.2% had NF primarily caused by Enterobacteriaceae (46.9 %) with non-fermenters (27.5%) and gram-positive cocci (25.5%) as other major pathogens. Gram negative isolates showed more than 80% sensitivity to antibiotics Piperacillin tazobactam, Imipenem and Meropenem Gram positive isolates showed more than 80% sensitivity to antibiotics Vancomycin and Linezolid. 9.6% of Staphylococcus Spp. were methicillin resistant.Conclusion: Cellulitis was commonly caused by Gram positive cocci, while NF was often associated with gram negative bacilli. The gram-negative bacilli and gram-positive cocci were susceptible only to higher antibiotics.