CLSI M45 PDF

Address correspondence to Romney M. Humphries, ude. Antimicrobial susceptibilities of Abiotrophia defectiva, Granulicatella adiacens, and Granulicatella elegans. Antimicrob Agents Chemother — All Rights Reserved.

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Address correspondence to Romney M. Humphries, ude. Antimicrobial susceptibilities of Abiotrophia defectiva, Granulicatella adiacens, and Granulicatella elegans. Antimicrob Agents Chemother — All Rights Reserved. This article has been cited by other articles in PMC. Abstract Nutritionally variant streptococci NVS are fastidious Gram-positive cocci comprised of the species Abiotrophia defectiva, Granulicatella adiacens, and Granulicatella elegans.

NVS are an important cause of bacteremia and infective endocarditis IE associated with significant morbidity and mortality. A total of clinical NVS blood isolates collected from to were tested. Ninety isolates were identified as G. This study provides antimicrobial susceptibility data for a recent collection of NVS and demonstrates important NVS species-related differences with respect to susceptibility to penicillin, cephalosporins, carbapenems, and daptomycin.

Species-level identification of NVS organisms when susceptibility testing is not readily available may aid in treatment decisions. Chromosomal DNA-DNA hybridization in 3 and 16S rRNA gene sequencing data in and 4 , 5 resulted in the reclassification of NVS isolates into two genera, Abiotrophia and Granulicatella, which comprise four recognized species: Abiotrophia defectiva, Granulicatella adiacens, Granulicatella elegans, and Granulicatella balaenopterae. A fifth species, Granulicatella para-adiacens, has been proposed but not formally recognized 6.

These bacteria, with the exception of G. The NVS have also been associated with other invasive infections, including abscess, wound infections, and meningitis 1 , The incidence of IE caused by NVS may be underreported due to the fastidious nature of these organisms and the challenge of recovering isolates from clinical specimens i.

Nevertheless, retrospective case review has demonstrated that cases of NVS IE are associated with higher rates of complications, including relapse, bacteriologic failure, embolization, and death, than IE caused by other streptococci Given the fastidious nature of the organisms, antimicrobial susceptibility testing AST is challenging for clinical laboratories. This fact, combined with the limited clinical data and high rate of complications, has led the American Heart Association AHA and British Society for Antimicrobial Chemotherapy BSAC to suggest NVS IE be treated following the guidelines put forth for enterococcal IE, that is to say, with a combination of benzylpenicillin or ampicillin plus gentamicin for a duration of 4 to 6 weeks 18 , In contrast to enterococcal IE, vancomycin can be used alone without gentamicin for 6 weeks for patients with penicillin allergy 18 , A recent retrospective case review of eight patients in Taiwan documented successful outcomes for all the patients, although for 2 patients, antimicrobial regimens were adjusted to include vancomycin, teicoplanin, or cefotaxime due to poor initial responses i.

In addition, several case reports describe outcomes varying from clinical cure to death following treatment of NVS IE with benzylpenicillin plus gentamicin 20 , — Few data exist regarding the in vitro susceptibility of NVS to antimicrobials typically used for treatment.

Data are also lacking for newer antimicrobials e. We confirm and expand upon important species-related differences among the NVS with respect to susceptibility to several antimicrobials, including penicillin, cephalosporins, carbapenems, and daptomycin. Isolates not confirmed as belonging to one of the NVS species were excluded from further study data not shown. Cefotaxime, ceftaroline, ceftriaxone, clindamycin, daptomycin, erythromycin, gentamicin, levofloxacin, linezolid, imipenem, meropenem, penicillin, streptomycin, and vancomycin were tested by broth microdilution BMD according to CLSI standards 23 , Louis, MO 23 , To evaluate the potential effect of pyridoxal and the reproducibility of daptomycin MICs, daptomycin testing was repeated at an outside reference laboratory Laboratory Specialists, Inc.

Statistical analysis. ECVs are intended to distinguish between organisms without and with phenotypically expressed resistance mechanisms for a species and a drug in a defined test system i. ECVs were not determined for antimicrobials if the modal MIC for a given species was less than or equal to the lowest concentration of the antimicrobial tested.

Similar to results obtained by Ratcliffe et al. The 11 isolates that were not identified as one of the three NVS species were excluded from further study. Incidentally, 5 of them all S. Three isolates one of each species were eliminated due to poor or no growth during AST. A greater percentage of isolates of G. Compared to penicillin, NVS were more susceptible to the third-generation cephalosporins cefotaxime Interestingly, A. Overall,

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CLSI M45 3rd Edition

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