In vitro investigation of the indirect pathogenicity of beta-lactamase-producing microorganisms in the nasopharyngeal microflora

Satoru Kaieda, Hisakazu Yano, Naohiro Okitsu, Yoshio Hosaka, Ryoichi Okamoto, Matsuhisa Inoue, Haruo Takahashi

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    9 Citations (Scopus)


    Objective: Nasopharyngeal microflora contains some beta-lactamase-producing microorganisms. In this study, we investigated in vitro on the indirect pathogenicities of Haemophilus parainfluenzae (H. parainfluenzae) and Moraxella catarrhalis (M. catarrhalis) against the antipneumococcul activities of some beta-lactams. Methods: We compared the antimicrobial and bactericidal activities of beta-lactams against penicillin-susceptible Streptococcus pneumoniae (PSSP) with or without presence of the enzymes of two species of beta-lactamase- producing microorganisms, H. parainfluenzae and M. catarrhalis. Results: When adding the enzymes extracted from these two beta-lactamase-producing microorganisms in equivalent amounts of 107 CFU/spot, the minimum inhibitory concentrations of amoxicillin (AMPC) and cefaclor (CCL) increased to >64 μg/mL. Even third-generation cephalosporins, such as cefditren (CDTR) and ceftriaxone (CTRX) showed marked increases with the enzyme of M. catarrhalis. In time-kill kinetics, same phenomenon was observed in mixed culture indicating the indirect pathogenicities of distinct bacteria, not extracted enzymes, on the cidal activities of beta-lactams against PSSP. Clavulanic acid (CVA)/AMPC, faropenem (FRPM), and imipenem (IPM) were not affected by these beta-lactamase-producing strains with respect to their activities against PSSP. However, these two beta-lactamase-producing strains and their enzymes did not show any significant influence on the antipneumococcul activities of beta-lactams, until the number of bacterial cells reached >108 CFU/mL. Conclusion: Our results suggest that these two species of beta-lactamase-producing microorganisms in the nasopharyngeal microflora may act as indirect pathogens on the antipneumococcul activities of beta-lactams with reflecting their substrate profiles, but this is dependent on sufficient amounts of enzyme for their influence as indirect pathogens.

    Original languageEnglish
    Pages (from-to)479-485
    Number of pages7
    JournalInternational Journal of Pediatric Otorhinolaryngology
    Issue number4
    Publication statusPublished - 2005 Apr


    • Beta-lactamase
    • Indirect pathogenicity
    • Nasopharyngeal microflora

    ASJC Scopus subject areas

    • Pediatrics, Perinatology, and Child Health
    • Otorhinolaryngology


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