RESUMO
Recent surveys in Vancouver showed most healthy children were colonized with beta-lactamase-producing Haemophilus parainfluenzae. Such organisms might alter the effects of penicillins on throat bacteria by local inactivation. To test this hypothesis in vitro, three isolates of beta-lactamase-producing Haemophilus parainfluenzae were each mixed on a membrane with ampicillin-sensitive strains of Haemophilus influenzae type b or group A Streptococcus pyogenes and exposed to ampicillin. When tested alone, susceptible strains were rapidly killed but when tested together with a beta-lactamase producer, they were protected, indicating efficient ampicillin degradation by Haemophilus parainfluenzae strains. If similar interactions occur in vivo, the effects of beta-lactams on throat bacteria could be significantly altered in the presence of beta-lactamase-producing Haemophilus parainfluenzae.
Assuntos
Haemophilus/crescimento & desenvolvimento , Penicilinase/genética , beta-Lactamases/genética , Ampicilina/farmacologia , Criança , Haemophilus/efeitos dos fármacos , Haemophilus/enzimologia , Humanos , Cinética , Streptococcus pyogenes/efeitos dos fármacos , Streptococcus pyogenes/crescimento & desenvolvimentoRESUMO
Carriage of ampicillin-resistant (Ampr) Haemophilus parainfluenzae has become frequent among children in our community, although carriage of Ampr Haemophilus influenzae remains uncommon. In this study we characterized the mechanism of ampicillin resistance in 27 representative isolates of H. parainfluenzae. As determined by isoelectric focusing, each isolate had a TEM-1 beta-lactamase; substrate profiles assessed for enzymes from 10 strains were also consistent with TEM-1 enzyme. Agarose gel electrophoresis revealed a plasmid of 23 to 34 megadaltons in each isolate and a small plasmid (less than or equal to 4 megadaltons) in 14 isolates. Transfer of ampicillin resistance to H. influenzae Rd was achieved during membrane mating with 14 of 15 donors. The transconjugants exhibited high-level ampicillin resistance (greater than or equal to 50 micrograms/ml), which was stable despite serial passage of isolates on antibiotic-free media. The transconjugants tested retained fertility. Cryptic plasmids were discovered in 7 of 25 antibiotic-susceptible H. parainfluenzae isolates. Our data suggest that H. parainfluenzae may play an important role in the exchange of Ampr genes among throat bacteria.
Assuntos
Ampicilina/farmacologia , Haemophilus/efeitos dos fármacos , Antibacterianos/farmacologia , Conjugação Genética , Haemophilus/enzimologia , Hemaglutininas/isolamento & purificação , Resistência às Penicilinas , Fatores R , beta-Lactamases/metabolismoRESUMO
The prevalence of ampicillin sodium-resistant Haemophilus influenzae was determined from throat cultures of 305 ambulatory children. Resistant strains were detected in 3% of children, amounting to 12% of Haemophilus isolates. Factors associated with carriage of ampicillin-resistant strains were sought: only ampicillin exposure was significant. Among children who had received ampicillin or amoxicillin trihydrate within six months, 9% harbored ampicillin-resistant strains compared with 1.4% among those not exposed. Colonization with H influenzae was more frequent following the use of ampicillin, and a higher proportion of isolates was resistant rates was observed with other antibiotics or with factors such as age, sex, otitis history, or day-care center exposure. The association between ampicillin/amoxicillin usage and carriage of ampicillin-resistant strains is increasingly clear. It remains to be determined whether the use of newer antibiotics for otitis also will encourage the development of resistance in H influenzae.
Assuntos
Ampicilina/farmacologia , Portador Sadio/microbiologia , Infecções por Haemophilus/microbiologia , Haemophilus influenzae/efeitos dos fármacos , Otite Média/tratamento farmacológico , Assistência Ambulatorial , Criança , Pré-Escolar , Feminino , Infecções por Haemophilus/tratamento farmacológico , Humanos , Lactente , Masculino , Nasofaringe/microbiologia , Resistência às PenicilinasRESUMO
Ampicillin resistance has been described in Haemophilus species other than Haemophilus influenzae, but its frequency and significance are uncertain. In a throat-culture survey, beta-lactamase-producing Haemophilus parainfluenzae was detected in 192 (72%) of 266 ambulatory children. Ampicillin-resistant H. parainfluenzae was more frequently found in children from three to four years of age (88%) or in those who attended day-care programs (97%) and less frequently in older children and parents (33%). Colonization was unrelated to previous exposure to antibiotics or to a history of otitis media. Colonization with ampicillin-resistant H. parainfluenzae occurred in 88% of subjects with H. influenzae, including all of seven subjects carrying ampicillin-resistant H. influenzae. Colonization with beta-lactamase-producing H. parainfluenzae was 26 times more frequent than with H. influenzae. If the mechanisms and genetics of resistance are the same, H. parainfluenzae may prove to be a vector for spread of resistance genes of H. influenzae.
