Molecular characterization of erythromycin-resistant Streptococcus agalactiae strains.
OBJECTIVE
The aim of this study is to identify the molecular characteristics of erythromycin-resistant (Erm(r)) Streptococcus agalactiae strains and to correlate with the clinical origin of strains.


METHODS
From 711 S. agalactiae strains, 119 Erm(r) strains (17%) were collected, serotyped and screened for macrolide resistance genes. The genetic relationship between strains was established by the PFGE analysis. Strains were tested for the group II intron GBSi1 downstream of the scpB gene, IS1548 in the hylB gene, four prophage DNA fragments and a lineage defined by multilocus sequence typing as ST-17.


RESULTS
Erythromycin resistance involved 8% of serotype Ia, 15% of serotype Ib, 9% of serotype II, 16% of serotype III, 31% of serotype IV and 35% of serotype V. The prevalence of Erm(r) strains was higher among strains isolated from the gastric fluid of neonates (33%) than in those isolated from bacteraemia and meningitis during early-onset disease (EOD) or late-onset disease (7% and 11%) (P = 0.001). In serotype III, Erm(r) strains were more frequent in vaginal carriage (22%) and colonized neonates (18%) than in EOD (0%) (P = 0.03). The mef(A) gene was the most common in serotype Ia (55%), the erm(A) gene in serotype Ib (75%) and the erm(B) gene in the other serotypes (56% to 75%). All resistant strains with IS1548 also had the erm(B) gene. Erm(r) strains were not randomly distributed in the different PFGE genogroups, and 11% had the GBSi1 intron, 37% had at least one prophage DNA fragment and 7% belonged to ST-17.


CONCLUSIONS
Erythromycin resistance varied according to the clinical origin, serotype and molecular characteristics of S. agalactiae strains.
Domelier
Anne-Sophie
AS
Université François-Rabelais de Tours, UFR de Médecine, EA 3854 'Bactéries et risque materno-foetal', Institut Fédératif de Recherche 136 'Agents Transmissibles et Infectiologie', 37032 Tours Cedex, France.
van der Mee-Marquet
Nathalie
N
Arnault
Laurence
L
Mereghetti
Laurent
L
Lanotte
Philippe
P
Rosenau
Agnès
A
Lartigue
Marie-Frédérique
MF
Quentin
Roland
R
D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016470:Bacteremia / Q000382:microbiology; D015373:Bacterial Typing Techniques; D016172:DNA Fingerprinting; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D004917:Erythromycin / Q000494:pharmacology*; D005260:Female; D005750:Gastric Juice / Q000382:microbiology; D005798:Genes, Bacterial; D005838:Genotype; D006801:Humans; D007231:Infant, Newborn; D007438:Introns; D055231:Lincosamides / Q000494:pharmacology; D008581:Meningitis / Q000382:microbiology; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000382:microbiology; D012703:Serotyping; D013290:Streptococcal Infections / Q000382:microbiology*; D013292:Streptococcus agalactiae / Q000145:classification / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D025381:Streptogramin B / Q000494:pharmacology; D014621:Vagina / Q000382:microbiology
D000900:Anti-Bacterial Agents; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D055231:Lincosamides; D025381:Streptogramin B; D004917:Erythromycin