Antimicrobial Susceptibilities of Peptostreptococcus anaerobius and the Newly Described Peptostreptococcus stomatis Isolated from Various Human Sources

Abstract

Peptostreptococcus anaerobius sensu lato, currently including two closely related species, P. anaerobius and P. stomatis, is known to be more resistant than other gram-positive anaerobic cocci. We reidentified potential Peptostreptococcus isolates and tested their susceptibilities to eight antimicrobials. Notably, P. anaerobius had constantly higher values for the MIC at which 50% of the isolates are inhibited (MIC 50 ) and the MIC 90 than P. stomatis.Gram-positive anaerobic cocci (GPAC) are clinically significant organisms recovered from mixed infections involving anaerobic bacteria (16,19). This heterogeneous group has undergone considerable taxonomic changes, with new genera being formed from species previously belonging to the genus Peptostreptococcus (10, 11). Peptostreptococcus anaerobius was the only representative of the genus until Peptostreptococcus stomatis was recently described (9). P. anaerobius sensu lato has been frequently cultured from clinical specimens from the mouth, upper respiratory tract, skin and soft tissues, bone and joints, and gastrointestinal and genitourinary tracts (5,6,8,16,19,20,27,28). Interestingly, Downes and Wade (9) suggested that the novel species, P. stomatis, originates from the oral cavity, whereas P. anaerobius sensu stricto has its habitat and is involved in infections under the waistline.GPAC have been considered susceptible to most antimicrobials used against anaerobic infections (19). However, P. anaerobius sensu lato seems to exhibit more resistance than other GPAC (2,13,17,18,21,23). No susceptibility data on P. anaerobius sensu stricto or P. stomatis exist thus far. The aim of the present study was to obtain information on their isolation sites and in vitro susceptibilities to eight antimicrobials potentially used to treat anaerobic infections.Sixty-four isolates that had been previously identified as P. anaerobius based on their anaerobic growth, coccoid cell morphology, sensitivity to sodium polyanethol sulfonate (SPS), and major production of isocaproic acid in gas-liquid chromatography (16) were available from various clinical specimens of 64 subjects. The isolation sites were traced from referrals that were sent together with the isolate to be characterized. The isolates, collected between 1985 and 2005, were revived from frozen (Ϫ70°C) stocks and subcultured on brucella blood agar to assure their purity before further testing. Key phenotypic tests discriminative in the separation of P. anaerobius and P. stomatis were the size of the growth inhibition zone around an SPS disk and the production of proline arylamidase (9). The zone around an SPS disk (Oxoid, Basingstoke, United Kingdom) was measured in millimeters (the minimum size should be 12 mm) on a brucella agar plate after 3 days of anaerobic incubation. Enzyme activity patterns were determined by the Rapid ID 32A test kit (API system; bioMérieux, Marcy l'Étoile, France) according to the manufacturer's instructions. For isolates with discrepant phenotypic characteristics, partial sequencing of the 16S r...

Evaluation of Antibiotic Susceptibility of Gram-Positive Anaerobic Cocci Isolated from Cancer Patients of the N. N. Blokhin Russian Cancer Research Center

“…Similar results have been obtained for Pe. anaerobius by other authors [ 11 ]. Pa. micra was mainly obtained from fluids (62,5%), while Pe.…”

European surveillance study on antimicrobial susceptibility of Gram-positive anaerobic cocci

“…In more recent studies, no resistance to metronidazole has been detected in GPAC [11,17]. It is also worth noting that differences in resistance rates between different species of GPAC, such as P. anaerobius and P. stomatis, have been reported [18].…”

Gram-positive anaerobic cocci – commensals and opportunistic pathogens

“…Also, resistance to tetracycline and erythromycin has been reported (Brazier et al, 2003;Boyanova et al, 2004). Data describing differences in antimicrobial susceptibility between various species of GPAC are increasing (Bowker et al, 1996;Brazier et al, 2003Brazier et al, , 2008Koeth et al, 2004;Roberts et al, 2006;Könönen et al, 2007) and are described in more detail for the major groups below.…”

“…However, a recent study looked at the antibiotic susceptibilities of 61 isolates of P. anaerobius and P. stomatis against amoxicillin, amoxicillin-clavulanic acid, cefoxitin, ertapenem, azithromycin, clindamycin, metronidazole and moxifloxacin (Könönen et al, 2007). However, a recent study looked at the antibiotic susceptibilities of 61 isolates of P. anaerobius and P. stomatis against amoxicillin, amoxicillin-clavulanic acid, cefoxitin, ertapenem, azithromycin, clindamycin, metronidazole and moxifloxacin (Könönen et al, 2007).…”