Antibiogram of Gram-Negative Bacteria Isolated from Surgical Site Infections at Lagos University Teaching Hospital

Surgical site infections caused by gram-negative bacteria constitute a major source of postoperative morbidity in Nigerian tertiary hospitals, with multidrug resistance increasingly complicating treatment. This study determines the antibiogram of gram-negative bacteria isolated from surgical site infections (SSIs) at Lagos University Teaching Hospital (LUTH), Idi-Araba, Lagos State, South West Nigeria. Wound swab samples were collected from 90 patients diagnosed with surgical site infections across three surgical wards over five months. Gram-negative bacteria were isolated on MacConkey agar and identified through standard biochemical reactions. Antibiotic susceptibility testing was performed using the Kirby-Bauer disk diffusion method against 13 antibiotics representing six antimicrobial classes. Klebsiella pneumoniae (28 percent), Escherichia coli (24 percent), Pseudomonas aeruginosa (18 percent), and Proteus mirabilis (14 percent) were the most prevalent gram-negative organisms. Overall resistance rates were highest for ampicillin (91 percent), cefuroxime (72 percent), and cotrimoxazole (68 percent). Meropenem and imipenem retained the highest efficacy, with 89 percent and 86 percent susceptibility respectively. ESBL phenotypes were confirmed in 37 percent of isolates. The study demonstrates a concerning pattern of carbapenem-sparing resistance among Pseudomonas isolates. Recommendations advocate for antibiogram-guided empirical therapy, infection prevention protocols, and routine SSI surveillance at LUTH. Keywords: surgical site infection, gram-negative bacteria, antibiogram, LUTH, ESBL