Short report: antimicrobial susceptibility and genetic characteristics of Haemophilus influenzae isolated from patients with respiratory tract infections between 1987 and 2000, including beta-lactamase-negative ampicillin-resistant strains.
The minimum inhibitory concentration (MIC) of five antibiotics and the presence of resistance genes was determined in 163 Haemophilus influenzae isolates collected over 13 years (1987-2000) in four two-yearly sampling periods from patients with respiratory tract infections. The prevalence of beta-lactamase-negative ampicillin-susceptible strains was approximately 80% over the sampling period although fewer strains (65.9%) were recovered in the period 1995-1997. TEM-1 type beta-lactamase-producing strains were less frequent starting at 15.6% and declining to 2.2% in the final sampling period. Low-beta-lactamase-negative ampicillin-resistant (BLNAR) strains were uncommon in 1987-1989 (2.2%), peaked to 19.5% in 1995-1997, but fell back to 11.1% by 2000. Fully BLNAR strains were not detected until the last sampling period (6.7%). The MICs of ampicillin, levofloxacin, cefditoren and ceftriaxone remained stable but there was an eight-fold increase in the MIC of cefdinir over the sampling period. Pulsed-field gel electrophoresis of DNA digests showed that three representative BLNAR strains were genetically distinct and 11 DNA profiles were identified among 17 low-BLNAR strains. These data suggest that the number of genetically altered BLNAR and low-BLNAR strains are increasing in Japan.
Qin
L
L
Department of Social Environment Medicine, Nagasaki University, Japan.
Watanabe
H
H
Asoh
N
N
Watanabe
K
K
Oishi
K
K
Mizota
T
T
Nagatake
T
T
D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002443:Ceftriaxone / Q000494:pharmacology; D005260:Female; D006192:Haemophilus Infections / Q000188:drug therapy*; D006193:Haemophilus influenzae / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D007564:Japan; D064704:Levofloxacin; D008297:Male; D008826:Microbial Sensitivity Tests; D015242:Ofloxacin / Q000494:pharmacology; D012141:Respiratory Tract Infections / Q000382:microbiology*; D018440:beta-Lactam Resistance / Q000235:genetics*
D000900:Anti-Bacterial Agents; D064704:Levofloxacin; D002443:Ceftriaxone; D000667:Ampicillin; D015242:Ofloxacin