In vitro activity of orally administered antimicrobial agents against Haemophilus influenzae recovered from children monitored longitudinally in a group day-care center

Abstract

To determine whether the prevalence of resistance to commonly used oral antimicrobial agents varied over time, we compared the in vitro susceptibilities of 217 strains of Haemophilus influenzae recovered from nasopharyngeal secretions of children in a day-care Oenter studied longitudinally between 1979 and 1987. The overall rate of 13-lactamase production in these strains was 18%, with rates of 57% in type b isolates (n = 21) and 14% in non-type b isolates (n = 196). The percentages of isolates for which MICs were '1.0 ,ug/ml for amoxicillin alone, amoxicillin in combination with clavulanic acid, and cefuroxime alone were 82, 92, and 93%, respectively. The percentage of strains for which cefaclor MICs were s1.0 ,ug/ml was only 0.5%. Isolates for which chloramphenicol MICs were >2.0 ,ug/ml or for which trimethoprim-sulfamethoxazole MICs were >0.5/9.5 pg/ml were uncommon: 1 and <1%, respectively. High concentrations of erythromycin alone and in combination with sulfisoxazole were required to inhibit the majority of test strains; there was no evidence of erythromycin-sulfisoxazole synergy. In vitro susceptibility to commonlly used oral antimicrobial agents remained at a constant level when H. influenzae isolates collected from children in a day'catae center during 1979 through 1983 were compared with strains collected during 1984 through 1987.Haemophilus influenzae is an important bacterial pathogen of the upper respiratory tract during childhood (2). Nonencapsulated (nontypeable) strains are common causes of conjunctivitis, otitis media, and maxillary sinusitis (9,16,36). Although these localized mucosal infections are rarely life-threatening, they are associated with significant morbidity; otitis media alone accounts for up to 40% of all pediatric office visits (17,34).The prevalence of otitis media appears to be two to four times higher in children attending group day-care,centers than it is in children cared for at home or in smaller day-care environments in homes (22,27,32,35). The clinical diagnosis of middle ear infection in children in group day-care centers typically results in empiric therapy with orally administered antimicrobial agents. The frequent use of these antimicrobial agents could contribute to the emergence of antibiotic-resistant pathogens within pediatric populations (13, 31). We recently reported a high rate of nasopharyngeal carriage of antibiotic-resistant pneumococci by children in a day-care center environment (14). In that report, we documented an increasing rate of pneumococcal resistance to trimethoprim-sulfamethoxazole during the 5 years of its use in that setting. Because colonizing H. influenzae strains were exposed to the same antibiotic pressures as the previously studied pneumococci, we were concerned that similar resistance trends could be occurring in H. influenzae carried by children in this day-care center population. The present investigation was undertaken to determine, in a longitudinal fashion, the prevalence of resistance to commonly used antimicrobial agents in H. infl...

Trimethoprim and sulfonamide resistance

“…In a collaborative European study, TMP-SUL-resistant H. influenzae isolates were most common in Spain (41%) and Italy (12%), whereas in all other countries resistance occurred at a rate of less than 8% (82). In the United States, Canada, and Australia, TMP-SUL resistance rates have been low (less than 5%) (23,45,78). In H. influenzae type b, the rate of resistance to TMP or SUL has been lower than that in nontypeable strains (23).…”