Antimicrobial and biocide resistance of bacteria in a Lebanese tertiary care hospital

Abstract The environment in a Lebanese tertiary-level care hospital was examined for bacterial contamination. In total, 8 open-air and 62 surface samples were taken and CFU were enumerated. Morphologically different isolates ( n  = 104) were obtained and tested for resistance to a wide range of antibiotics by the Kirby–Bauer disc diffusion method. Minimum bactericidal concentrations of isolates to seven different biocides used within this facility were also determined using both qualitative and quantitative methods. Gram-positive bacteria (82.7% of isolates) were encountered more often than Gram-negative bacteria (17.3%), and the genus Staphylococcus was most prevalent among isolates (59.6% of the isolates). Gram-positive isolates showed the highest resistance to penicillin (60.6%), clindamycin (54.5%) and ceftazidime (39.4%); the lowest frequencies of resistance were seen with vancomycin (0% of isolates), nitrofurantoin (3.5%), tetracycline (12.1%) and ciprofloxacin (12.1%). The prevalence of meticillin-resistant Staphylococcus aureus (MRSA) and meticillin-resistant coagulase negative staphylococci among all environmental samples was 3.8% and 11.5% of isolates, respectively. All Gram-negative isolates were multidrug-resistant (MDR). With respect to biocides, the highest frequency of resistance was to quaternary ammonium compounds (QACs) (13.5% of isolates) and the lowest frequency of resistance was to QAC/biguanide complex (