[Serotypes and antimicrobial susceptibility of Streptococcus agalactiae].
BACKGROUND
Streptococcus agalactiae or group B streptococcus, GBS, is the leading cause of neonatal and maternal infections and an opportunistic pathogen in adults with underlying disease. In the last decade, a dramatic increase in the resistance of this microorganism to erythromycin and clindamycin has been observed.


OBJECTIVE
To determine the serotype distribution and antimicrobial susceptibility of isolates of S. agalactiae collected from infections and colonization and to assess the genetic mechanisms of macrolide and clindamycin resistance.


METHODS
A total of 100 GBS isolates were collected between 1998 and 2002, in Santiago, Chile. They were isolated from the amniotic fluid from patients with premature rupture of membranes (7 isolates), blood from neonatal sepsis (10 isolates), neonate colonizations (2 strains), skin and soft tissue infections (7 isolates), urinary tract infections (5 isolates), genital infections (3 isolates), articular fluid (one isolate), and 65 strains were recovered from vaginal colonization55.


RESULTS
Serotypes Ia, II and III were the predominant serotypes identified in our study, accounting for 90 (90%) of the strains. Five isolates belonged to serotypes Ib (5%) and two (2%) to serotype V respectively; no strains belonging to serotype IV were found. All strains were susceptible to penicillin G, ampicillin and cefotaxime, and four isolates (4%) were resistant to both erythromycin (MIC >64 microg/ml) and clindamycin (MIC >64 microg/ml). The strains had a constitutive macrolide-lincosamide-streptogramin (cMLSB) resistance phenotype and the erm(A) gene was present in the four isolates.


CONCLUSIONS
Serotypes Ia, II and III were the predominant serotypes in this study. All strains were susceptible to penicillin G, ampicillin and cefotaxime, and four (4%) strains were resistant to both erythromycin and clindamycin. The cMLSB resistance phenotype, and the erm(A) gene was detected in resistant strains.
Martínez
María Angélica
MA
Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile. mamartin@med.uchile.cl
Ovalle
Alfredo
A
Durán
Claudia
C
Reid
Iván
I
Urriola
Gabriela
G
Garay
Beatriz
B
Cifuentes
Marcela
M
D000328:Adult; D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002439:Cefotaxime / Q000494:pharmacology; D002981:Clindamycin / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D004917:Erythromycin / Q000494:pharmacology; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D011247:Pregnancy; D018805:Sepsis / Q000382:microbiology; D012703:Serotyping; D013290:Streptococcal Infections / Q000382:microbiology*; D013292:Streptococcus agalactiae / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D013752:Tetracycline / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D002981:Clindamycin; D004917:Erythromycin; D000667:Ampicillin; D013752:Tetracycline; D002439:Cefotaxime