Streptococcus agalactiae: sensibilidad antimicrobiana y genotipos de resistencia a macrólidos en muestras genitales de gestantes en Cantabria

[Serotypes and antibiotic resistance patterns in beta-hemolytic Streptococcus agalactiae isolates in colonized mothers and newborns with invasive disease]

INTRODUCTION

Current preventive measures against neonatal disease caused by Streptococcus agalactiae (GBS) are prenatal screening and intrapartum antibiotic prophylaxis with appropriate antimicrobials. An alternative to this strategy would be the administration of a polysaccharide vaccine as the distribution of capsular serotypes of circulating strains needs to be known.

METHODS

A study was made of 188 strains from pregnant women carrying GBS and 24 newborns with neonatal disease. Susceptibility testing was performed with penicillin, erythromycin and clindamycin following CLSI standards, and capsular serotype was determined by two methods: latex agglutination and PCR.

RESULTS

Of the 188 strains of S.agalactiae from the pregnant women, there was 80.8% agreement in the results between the two techniques. Resistant to erythromycin and clindamycin was found in 16.5% and 10.1%, respectively. For neonatal strains, 95.8% of the results obtained by the two techniques were identical. The rates of resistance to erythromycin and clindamycin were 8.3% and 4.1%, respectively. In both groups, most frequently isolated serotype was iii, and the most related to antimicrobial resistance serotype was v.

CONCLUSION

Epidemiological studies are necessary to continue surveillance of serotypes causing invasive disease and its antibiotic sensitivity patterns using sensitive and specific methods.

Prevalence and mechanisms of erythromycin and clindamycin resistance in clinical isolates of beta-haemolytic streptococci of Lancefield groups A, B, C and G in Seville, Spain

Susceptibility to erythromycin and clindamycin was determined in 860 consecutive clinical isolates of beta-haemolytic streptococci belonging to groups A (GAS, n = 134), B (GBS, n = 689), C (GCS, n = 19) and G (GGS, n = 18). Erythromycin resistance was 26.1% in GAS, 15.7% in GBS, 5.3% in GCS and 33.3% in GGS. The highest rate of clindamycin resistance (33.3%) was in GGS, followed by GBS (15.8%), GCS (15.8%) and GAS (5.2%). The M phenotype was predominant in GAS (80%), the constitutive MLS(B) phenotype was predominant in GBS (75%), and all GGS isolates showed the inducible MLS(B) phenotype. The uncommon erythromycin-susceptible and clindamycin-resistant phenotype was found in four GBS and two GCS isolates.