A MULTICENTER STUDY OF THE PREVALENCE AND SUSCEPTIBILITY PATTERNS OF ISOLATES OF STREPTOCOCCUS-PNEUMONIAE WITH REDUCED SUSCEPTIBILITY TO PENICILLIN-G IN LOUISIANA

Because of increasing reports of multiple-antibiotic-resistant strains of Streptococcus pneumoniae and associated clinical failures, this st udy was performed to determine the prevalence of multiresistance among strains from nine Louisiana medical centers. Using a National Committ ee for Laboratory Standards broth microdilution method, 481 strains we re tested. Of these, 70% were penicillin-susceptible (PS), 23% had int ermediate minimum inhibitory concentration values to penicillin (I), a nd 7% were fully resistant to penicillin (PR). The isolation rates (15 % to 40% for I strains and 0% to 33% for PR strains) at the various me dical centers varied appreciably. The prevalence of penicillin resista nce was highest among upper respiratory isolates, while cross-resistan ce to other antimicrobials varied. The least cross-resistance was note d among PS strains. However, strains with reduced penicillin susceptib ility had high levels of cross-resistance. Among I strains, the preval ence of cross-resistance (%) was noted for amoxicillin/clavulanate (6% ), cefuroxime (71%), cefaclor (91%), ceftriaxone (13%), cefotaxime (34 %), erythromycin (67%), azithromycin (32%), and clarithromycin (32%). For PR strains, the prevalence of cross-resistance was 97% for amoxici llin/clavulanate, cefuroxime, and cefaclor; 67% for ceftriaxone and er ythromycin; 89% for cefotaxime; and 69% for azithromycin and clarithro mycin. These data emphasize the high prevalence of multiple-antimicrob ial-resistance among strains of S pneumoniae with reduced penicillin s usceptibility in this geographic area.