INCIDENCE OF BETA-LACTAMASE PRODUCTION AND ANTIBIOTIC SUSCEPTIBILITIES AMONG CLINICAL ISOLATES IN SAUDI-ARABIAN HOSPITALS

In a multicenter survey, 2100 strains of bacteria isolated from clinic al specimens from hospitalized patients were examined for production o f beta-lactamase and susceptibility to commonly prescribed antibiotics . Bacteria tested consisted of 1050 strains of Enterobacteriaceae, 150 strains of Haemophilus influenzae, and 900 strains of staphylococci. Among the Enterobacteriaceae tested, 83% of Klebsiella species, 64% of Escherichia coli, and 43% of Proteus species produced betalactamase. Only 15% of H influenzae were beta-lactamase producers. Of the staphyl ococci, 89% of Staphylococcus aureus and 85% of Staphylococcus epiderm idis were beta-lactamase positive. The susceptibility of the isolates to various antibiotics was determined using the agar dilution method. Cefuroxime and amoxicillin-clavulanate had greater in vitro activity a gainst beta-lactamase-producing strains of staphylococci than did ceph alexin, trimethoprim-sulfamethoxazole, or amoxicillin. Cefixime showed little activity against staphylococci. Ninety-nine percent of H influ enzae were sensitive to amoxicillin-clavulanate and cefuroxime, 83% we re sensitive to amoxicillin, 84% to trimethoprim-sulfamethoxazole, and 62% to cephalexin. Resistance of E coil isolates was 44% to tetracycl ine, 29% to trimethoprimsulfamethoxazole, and 18% to gentamicin. Nearl y 92% of E coli isolates were inhibited by cefuroxime and 94% by amoxi cillin-clavulanate. The types of beta-lactamase produced by 333 random isolates were determined. Plasmid-mediated beta-lactamases were encou ntered in 93% of E colt and 67% of Klebsiella species. Almost all H in fluenzae isolates (96.6%) produced the TEM1 enzyme. Changing patterns of susceptibility and the availability of new and expensive agents req uire continual updating of knowledge concerning treatment of these pat hogens.