Characterization of Virulent Bacterial Isolates Associated with Multi-Drug Resistance among Patients with Surgical Site Infections in Selected Specialist Hospitals in Calabar, Nigeria

Aims: Increasing research findings have documented the continuous emergence and threats posed by drug resistant clinical isolates from post-operative wound infections to commonly used antibiotics globally. This hospital-based study investigated virulent bacterial pathogens implicated with post-operative wound infections among surgical site infection (SSI) patients in Calabar, Nigeria and determined their antibiotic resistance pattern.

Methodology: A total of 127 bacterial isolates of different genus from 110 SSI patients, were isolated from pus and surgical wound exudates and fully characterized using standard bacteriological procedures. Antimicrobial susceptibility patterns of isolates were determined using Kirby- Bauer disk diffusion method, following the guidelines by Clinical Laboratory Standard Institute (CLSI).

Results: Multi-drug resistant bacteria isolated and their percentage frequency were coagulase Negative Staphylococci (21.3%), Staphylococcus aureus (19.7%), Pseudomonas aeruginosa (14.2%), Escherichia coli (11.8%), Klebsiella pneumoniae (9.4%), Enterococcus faecium (6.3), Enterobacter cloacae (4.7%), Proteus mirabilis (4.7%), Acinetobacter baumannii (3.1%), Pseudomonas putida (3.1%) and Aerococcus viridans (1.6%). Among gram-positive bacteria isolated, S. aureus showed highest resistance to several antimicrobials (100% to oxacillin, 96% to ciprofloxacin, 92% to levofloxacin, and 76% resistance to vancomycin). All recovered S. aureus isolates were cefoxitin screen positive indicating possible MRSA isolates. Additionally, among Gram-negative isolates K. pneumoniae was found to possess higher resistance to several antibiotics (66.7% resistance to each of ciprofloxacin, levofloxacin, ceftazidime, trimethoprim /sulfamethoxazole, cefazolin, ampicillin, tobramycin and 58.3% resistance to each of ceftriaxone, gentamicin, and ampicillin/sulbactam). Statistical analysis of categorical variables of study subjects revealed that length of hospital stay, type of surgery, previous admission history, antibiotic use, and age were significant (p<0.05) in SSI outcome of patients, while patients’ gender was not significant (p>0.05) in SSI outcome.

Conclusion: Adherence to measures of strict infection control, optimal preoperative, intraoperative, and postoperative patient care, including multifaceted approaches involving surveillance, and antimicrobial stewardship, are vital to SSI treatment outcomes.