In Vitro Antimicrobial Susceptibility Profiles of Gram-Positive Anaerobic Cocci Responsible for Human Invasive Infections.

François Guérin,Loren Dejoies,Hélène Guet-Revillet,Vincent Cattoir,Olivier Barraud,Emmanuelle Gallois,Violaine Walewski,Frédéric Janvier,On Behalf Of The Gmc Study Group ,Stéphane Corvec,Thomas Guillard,Nicolas Degand

doi:10.3390/microorganisms9081665

Abstract

The aim of this multicentre study was to determine the in vitro susceptibility to anti-anaerobic antibiotics of Gram-positive anaerobic cocci (GPAC) isolates responsible for invasive infections in humans. A total of 133 GPAC isolates were collected in nine French hospitals from 2016 to 2020. All strains were identified to the species level (MALDI-TOF mass spectrometry, 16S rRNA sequencing). Minimum inhibitory concentrations (MICs) of amoxicillin, piperacillin, cefotaxime, imipenem, clindamycin, vancomycin, linezolid, moxifloxacin, rifampicin, and metronidazole were determined by the reference agar dilution method. Main erm-like genes were detected by PCR. The 133 GPAC isolates were identified as follows: 10 Anaerococcus spp., 49 Finegoldia magna, 33 Parvimonas micra, 30 Peptoniphilus spp., and 11 Peptostreptococcus anaerobius. All isolates were susceptible to imipenem, vancomycin (except 3 P. micra), linezolid and metronidazole. All isolates were susceptible to amoxicillin and piperacillin, except for P. anaerobius (54% and 45% susceptibility only, respectively). MICs of cefotaxime widely varied while activity of rifampicin, and moxifloxacin was also variable. Concerning clindamycin, 31 were categorized as resistant (22 erm(A) subclass erm(TR), 7 erm(B), 1 both genes and 1 negative for tested erm genes) with MICs from 8 to >32 mg/L. Although GPACs are usually susceptible to drugs commonly used for the treatment of anaerobic infections, antimicrobial susceptibility should be evaluated in vitro.

Highlights

Gram-positive anaerobic cocci (GPAC) has long been an heterogenous group of organisms and has undergone considerable taxonomic changes with the creation of new genera formed from species previously belonging to the genus Peptostreptococcus, such as Finegoldia, Parvimonas, Anaerococcus, and Peptoniphilus while the only remaining representative of this genus is P. anaerobius [5]
The most commonly species found in clinical material are Finegoldia magna, Parvimonas micra, Peptoniphilus harei, and Peptostreptococcus anaerobius [2,6,7]
Except 5/11 (45%) resistant strains of P. anaerobius (MIC = 8–16 mg/L), all other 128 strains were susceptible to amoxicillin with Minimum inhibitory concentrations (MICs) ranging from ≤0.03 to 2 mg/L (Table 1)

Summary

Introduction

Microorganisms 2021, 9, 1665 all anaerobic clinical isolates [1,2]. They are opportunistic pathogens responsible for many human infections (often polymicrobial) especially in the elderly population and immunocompromised patients, including pleuropulmonary, intraabdominal, pelvic, skin, and soft-tissue and bone and joint infections (BJIs) as well as brain abscess and bacteremia [1,2,3,4]. GPAC has long been an heterogenous group of organisms and has undergone considerable taxonomic changes with the creation of new genera formed from species previously belonging to the genus Peptostreptococcus, such as Finegoldia, Parvimonas, Anaerococcus, and Peptoniphilus while the only remaining representative of this genus is P. anaerobius [5]. The most commonly species found in clinical material are Finegoldia magna, Parvimonas micra, Peptoniphilus harei, and Peptostreptococcus anaerobius [2,6,7]

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