Incidence of beta-lactamase production among out patient clinical isolates in Middle Eastern countries and their antibiotic susceptibilities. Middle Eastern Study Group.

In a multicenter survey in seven Middle Eastern countries, 1,827 clinical isolates from patients with community-acquired infections (outpatients) were examined for both production of beta-lactamase and their susceptibility to commonly prescribed antibiotics. Of these isolates, 63% were gram-negative and 37% were gram-positive organisms. beta-lactamase was produced by 65% of all isolates, representing 61 and 75% of gram-negative and gram-positive organisms, respectively. Using standardized disk susceptibility testing, high rates of resistance were observed among gram-negative and gram-positive organisms, respectively, for penicillin (86 and 75%), ampicillin (67 and 66%) and amoxicillin (58 and 52%). Resistance to tetracycline and co-trimoxazole were also seen, but to a lesser degree. Susceptibility of these organisms towards the cephalosporins cepharadine, cephalexin and cefadroxil ranged from 30 to 70%, which appears to correlate fairly closely with the prevalence of beta-lactamase production. Cefuroxime inhibited about 94 and 79% of gram-positive and gram-negative organisms, respectively, regardless of the production of beta-lactamase. These data are valuable since antibiotic therapy is usually instituted on a best-guess principle against the most likely potential pathogens.