Antimicrobial susceptibility patterns of bacterial isolates at the American University Medical Center in Lebanon

In Lebanon, knowledge of the prevailing pattern of bacterial resistance to antimicrobial agents has been limited, particularly because of 15 years of civil strife. Thus, the current study was conducted to determine the antimicrobial susceptibility patterns of nonselected bacterial isolates recovered from recent clinical specimens, using the standardized disk agar diffusion technique. A total of 5216 isolates (1443 Gram positive and 3773 Gram negative) were examined. Over 92% of Staphylococcus aureus and coagulase-negative staphylococci (CNS) were resistant to penicillins. Methicillin resistance was more frequently noted among CNS (28%) compared with S. aureus (18%). For the pneumococci, 27% of the isolates were resistant to penicillin G. High but variable rates of multidrug resistance were encountered among Acinetobacter spp., Pseudomonas spp., Serratia spp., Citrobacter spp., and Enterobacter spp. Ampicillin resistance was detected in 65% of Escherichia coli and in 20% of Haemophilus influenzae isolates. Although one resistant Salmonella typhi strain was observed, 17% of other Salmonella spp. and 60% of Shigella spp. proved to be resistant to ampicillin, chloramphenicol, and cotrimoxazole. Among Vibrio cholerae isolates, high resistance to tetracycline (71%) and trimethoprim-sulfamethoxazole (94%) was observed. The overall antimicrobial resistance rates in Lebanon seem to fall between figures reported from the Arabian Gulf countries (higher) and those from medical centers in the United States (lower).