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ABSTRACTGroup B Streptococcus(GBS) is the leading cause of neonatal invasive infections and an emerging pathogen in the elderly. Our objectives were to describe the evolution of GBS resistance to antibiotics in France and to investigate the emergence of fluoroquinolone (FQ)-resistant isolates. A total of 8,757 unrelated GBS isolates were collected and tested for antibiotic susceptibility from 2007 to 2014 according to EUCAST recommendations. All isolates were susceptible to penicillin G, amoxicillin, and vancomycin. Resistance to macrolides decreased from 47.0% to 30.0%, whereas high-level resistance to aminoglycosides, especially amikacin, increased from 6.4% to 8.8% and 24 isolates (0.3%) were highly resistant to gentamicin. FQ resistance gradually increased from 0.2% in 2007 (n= 1) to 1.5% in 2014 (n= 18, P< 0.01). Capsular polysaccharide (CPS) genotyping, multilocus sequence typing, and sequencing of the quinolone resistance-determining region (QRDR) showed that GBS isolates of sequence type 19 (ST-19) CPS type V were largely overrepresented in FQ-resistant isolates (n= 30, 45.5%). All 30 strains displayed the same QRDR mutations and were often associated with cross-resistance to macrolides (93.3%) and gentamicin (30%). In conclusion, we report the rise of FQ- and aminoglycoside-resistant GBS in France over an 8-year study period, an evolution likely linked to the clonal expansion of ST-19 CPS V-resistant isolates. This study emphasizes the need for a continuous surveillance of GBS epidemiology and antibiotic susceptibility.

ABSTRACTSeventy-four unrelated clinical isolates of Streptococcus pneumoniaeharboring the tet(M) gene were studied. Seven strains with low tetracycline (Tc) MICs (0.25 to 0.5 μg/ml) were found to harbor truncated tet(M) alleles that were inactivated by different frameshift mutations. In contrast, five strains bore deletions in the tet(M) promoter region, among which four displayed increased Tc MICs (16 to 64 μg/ml). The same promoter mutations were detected in Tc-resistant mutants selected in vitrofrom various susceptible strains. Sequence analysis revealed that these deletions might impede the formation of the transcriptional attenuator located immediately upstream of tet(M). Expression in Enterococcus faecalisof a tet(M) reporter gene transcribed from these promoter mutants conferred a level of Tc resistance similar to that observed in the parental S. pneumoniaestrains. These results show that different levels of Tc susceptibility found in clinical isolates of S. pneumoniaecan be explained by frameshift mutations within tet(M) and by alterations of the upstream transcriptional attenuator.

ABSTRACTThe genetic basis of antibiotic resistance in 113 unrelated group B streptococci was studied by PCR. Ninety-four strains were resistant to tetracycline-minocycline, and tet(M) was detected in 85% of these isolates. Seventeen erythromycin-resistant strains contained the erm(B), erm(TR), or mef(A) gene. Eleven strains exhibited high-level resistance to kanamycin due to the presence of the aphA3gene; eight of these strains were also highly resistant to streptomycin; aad-6-related sequences were detected in seven strains.

ABSTRACTClinical blood isolates from three sequential episodes of endocarditis occurring over a 6-month period in a child with a malformative cardiopathy were investigated. All isolates identified asAbiotrophia defectivawere resistant to erythromycin-clindamycin and to tetracycline-minocycline, due to the presence of sequences homologous to the erythromycin resistance geneermBand to the tetracycline resistance genetet(M), respectively. These resistance genes were located on a chromosomally borne composite Tn916-related transposon. These results demonstrate the involvement of conjugative transposons in the dissemination of antibiotic resistance in the genusAbiotrophia.

ABSTRACTKlebsiella pneumoniaeNEM865 was isolated from the culture of a stool sample from a patient previously treated with ceftazidime (CAZ). Analysis of this strain by the disk diffusion test revealed synergies between amoxicillin-clavulanate (AMX-CA) and CAZ, AMX-CA and cefotaxime (CTX), AMX-CA and aztreonam (ATM), and more surprisingly, AMX-CA and moxalactam (MOX). Clavulanic acid (CA) decreased the MICs of CAZ, CTX, and MOX, which suggested that NEM865 produced a novel extended-spectrum β-lactamase. Genetic, restriction endonuclease, and Southern blot analyses revealed that the resistance phenotype was due to the presence in NEM865 of a 13.5-kb mobilizable plasmid, designated pNEC865, harboring a Tn3-like element. Sequence analysis revealed that the blaTgene of pNEC865 differed from blaTEM-1by three mutations leading to the following amino acid substitutions: Glu104→Lys, Met182→Thr, and Gly238→Ser (Ambler numbering). The association of these three mutations has thus far never been described, and theblaTgene carried by pNEC865 was therefore designatedblaTEM-52. The enzymatic parameters of TEM-52 and TEM-3 were found to be very similar except for those for MOX, for which the affinity of TEM-52 (Ki, 0.16 μM) was 10-fold higher than that of TEM-3 (Ki, 1.9 μM). Allelic replacement analysis revealed that the combination of Lys104, Thr182, and Ser238was responsible for the increase in the MICs of MOX for the TEM-52 producers.

ABSTRACTAmong 1,827 group B Streptococcus(GBS) strains collected between 2006 and 2013 by the French National Reference Center for Streptococci, 490 (26.8%) strains were erythromycin resistant. The erm(T) resistance gene was found in six strains belonging to capsular polysaccharides Ia, III, and V and was carried by the same mobilizable plasmid, which could be efficiently transferred by mobilization to GBS and Enterococcus faecalisrecipients, thus promoting a broad dissemination of erm(T).

ABSTRACTAmong 128 Streptococcus gallolyticus(Streptococcus bovis) isolates, 77.7% were resistant to tetracyclines and contained tet(M) and/or tet(L) and/or tet(O). A total of 59.4% had macrolide resistance and contained erm(B) and, rarely, mef(A). Among the one-third of isolates highly resistant to kanamycin and streptomycin, most harbored aphA3and aad-6genes.