Abstract
Background: The genera Abiotrophia and Granulicatella, previously known as nutritionally variant streptococci (NVS), are fastidious bacteria requiring vitamin B6 analogs for growth. They are members of human normal oral microbiota, and are supposed to be one of the important pathogens for so-called “culture-negative” endocarditis. Methods: The type strains and oral isolates identified, by using both phenotypic profiles and the DNA–DNA hybridization method, were examined for susceptibilities to 15 antimicrobial agents including penicillin (benzylpenicillin, ampicillin, amoxicillin, and piperacillin), cephem (cefazolin, ceftazidime, ceftriaxone, and cefaclor), carbapenem (imipenem), aminoglycoside (gentamicin), macrolide (erythromycin), quinolone (ciprofloxacin), tetracycline (minocycline), glycopeptide (vancomycin), and trimethoprim-sulfamethoxazole complex. The minimum inhibitory concentration and susceptibility criterion were determined, according to the consensus guideline from the Clinical and Laboratory Standards Institute. Results: Isolates of Abiotrophia defectiva were susceptible to ampicillin, amoxicillin ceftriaxone, cefaclor, imipenem, ciprofloxacin, and vancomycin. Isolates of Granulicatella adiacens were mostly susceptible to benzylpenicillin, ampicillin, amoxicillin, cefazolin, ceftriaxone, imipenem, minocycline, and vancomycin. The susceptibility profile of Granulicatella elegans was similar to that of G. adiacens, and the susceptibility rate was higher than that of G. adiacens. Conclusions: Although Abiotrophia and Granulicatella strains are hardly distinguishable by their phenotypic characteristics, their susceptibility profiles to the antimicrobial agents were different among the species. Species-related differences in susceptibility of antibiotics should be considered in the clinical treatment for NVS related infections.
Highlights
The bacteria formerly known as nutritionally variant streptococci (NVS) are characterized by their growth as small satellite colonies supported by helper bacteria such as Staphylococcus aureus [1].The NVS strains require vitamin B6 analogs for growth and produce bacteriolytic enzymes, pyrrolidonyl arylamidase and chromophore in common and were supposed to be auxotrophic variants of viridans group streptococci [2]
The phenotypic characteristics of the NVS isolates were similar, the profiles of susceptibility were unique among the species
The NVS isolates were susceptible to ampicillin (96.7%), amoxicillin (100%), imipenem (100%), and vancomycin (96.7%)
Summary
The bacteria formerly known as nutritionally variant streptococci (NVS) are characterized by their growth as small satellite colonies supported by helper bacteria such as Staphylococcus aureus [1].The NVS strains require vitamin B6 analogs for growth and produce bacteriolytic enzymes, pyrrolidonyl arylamidase and chromophore in common and were supposed to be auxotrophic variants of viridans group streptococci [2]. They were transferred into two new genera, Abiotrophia and Granulicatella, on the basis of 16S rRNA gene sequence homology analysis [3,4] They have been estimated as one of the important pathogens of so-called ‘culture-negative endocarditis’ [2,5,6]; because of their fastidiousness in growth, difficulty in identification, and complication in taxonomic position, the clinical importance of these bacteria has been underestimated by clinicians [7]. The genera Abiotrophia and Granulicatella, previously known as nutritionally variant streptococci (NVS), are fastidious bacteria requiring vitamin B6 analogs for growth. They are members of human normal oral microbiota, and are supposed to be one of the important pathogens for so-called “culture-negative” endocarditis. Species-related differences in susceptibility of antibiotics should be considered in the clinical treatment for NVS related infections
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