A 1994-95 SURVEY OF HAEMOPHILUS-INFLUENZAE SUSCEPTIBILITY TO 10 ORALLY-ADMINISTERED AGENTS - A 187 CLINICAL LABORATORY CENTER SAMPLE IN THEUNITED-STATES

During August, 1994 to April, 1995, a total of 2278 clinical isolates of Haemophilus influenzae were obtained from 187 clinical laboratories in the United States (U.S.). The mast majority of these isolates (75% ) were from respiratory sites, and the remaining organisms were from b lood, ear; eye, and spinal fluid sources. The overall rate of beta-lac tamase production and ampicillin resistance was 36%. The antimicrobial susceptibility of isolates was determined by reference broth microdil ution testing against ten orally administered agents. MIC values were compared according to 12 geographical regions, inpatient or outpatient status, gender, and eight age groupings. Modest and occasionally sign ificant differences were observed: I) greater- numbers of beta-lactama se-producing strains among out-patients, in males, in the mid-Atlantic region, and in children less than or equal to 12 years of age; 21 low er prevalence of beta-lactamase-producing isolates in the Southeast an d Pacific regions; 3) cefaclor, cefprozil, and loracarbef activity was lowest among the younger children (less than or equal to six years); and 4) macrolide in vitro efficacy was lowest in patients > 50 years o f age and in three eastern regions. Overall, move than 99% of the stra ins were susceptible to amoxicillin/clavulanic acid, cefixime, and cef podoxime (e.g., widest potential clinical use). Susceptibilities using National Committee for Clinical Laboratory Standards (NCCLS) breakpoi nt criteria for the other agents were: 96.6% to cefuroxime, 86.5% to l oracarbef, 84.0% to clarithromycin, 81.8% to cefaclor, and 80.7% to ce fprozil. Non-beta-lactamase mechanisms of resistance to ampicillin wer e rare (0.2%) or episodic and were attributed to altered penicillin-bi nding proteins. Although there is art increased prevalence of p-lactam ase production among H. influenzae isolates compared to prior years, f our p-lactams remain highly active (> 95% susceptibility) against cont emporary strains of H. influenzae. Other monitored compounds seem to h ave declined in spectrum and surveillance trials for resistance among H. influenzae isolates should continue in an effort to identify trends in the U.S. (C) 1997 Elsevier Science Inc.