Abstract
A study of invasive strains of Streptococcus agalactiae (GBS) from Cordoba and Misiones, Argentina; was conducted to determine serotypes, the susceptibility to macrolides and molecular profiles of virulence and resistance. We studied 17 strains, recovered from cerebrospinal fluid, blood and cellulite and, a strain of trophoblastic remnants from Misiones. The serotypes were determined by agglutination with sera and phenotypes of resistance to macrolide-lincosamide-streptogramin B (MLSB), were determined with the double-disk test (D-test). The confirmation was performed by E-test by ERI and CLI respectively that determined the minimum inhibitory concentration (MIC). Results were interpreted as recommended by the Clinical and Laboratory Standards Institute (CLSI) 2013. Resistance genes: ermB, ermTR and mefA and the virulence genes: bac, bca, rib, lmb, hylB, scpB, fbsA, fbsB and cylB were investigated by conventional PCR. Serotype III (50%) and Ia (50%) were detected in Cordoba. One strain showed cMLSB phenotype, confirmed by MIC. The same strains showed a resistance gene ermB. All studied virulence genes were detected in 100% of these strains. In Misiones, serotypes were III (72.7%), Ia (18.2%) and Ib (9.1%). All strains were susceptible to CLI and ERI by D-test, confirmed by MIC. None of the strains showed resistance genes. Virulence genes bca, rib, hylB, lmb, fbsA, fbsB and cylB were detected in 100% of the strains, bac in 81.8% and scpB in 90.9%. Our results are in accordance with international data, associating higher frequency of serotype III of invasive neonatal disease followed by Ia. The presence of serotype Ib could indicate a regional difference for Misiones. We highlight the macrolides susceptibility in strains of Misiones and consistency in the results for D-test, MIC and PCR for the single strain resistant phenotype cMLSB from Cordoba. The virulence genes studied were presented with high frequency as expected for invasive strains.
Highlights
Streptococcus agalactiae (Lancefield group B streptococcal, GBS), initially described by Nocarrd and Mollereau in 1887 [1] was isolated from vaginal cultures in 1935, was listed as a human pathogen for the first time in 1938 as cause of fatal puerperal fever [2]
GBS strains of Misiones: The 11 strains were susceptible to ERI and CLI by disk test (D-test) and confirmation by CIM gave similar results with ranges from 0.003 to 0.12 μg/ml for ERI and from 0.032 to 0.094 μg/ml for CLI
GBS strains of Cordoba: Two strains belonging to the same patient and isolated from different clinical specimens, showed resistance phenotype cMLSB (ERI and CLI = 6 mm) confirmed by CIM (ERI and CLI = 8 μg/ml) for both strains, indicating that it is insulated with antibiotype identical
Summary
Streptococcus agalactiae (Lancefield group B streptococcal, GBS), initially described by Nocarrd and Mollereau in 1887 [1] was isolated from vaginal cultures in 1935, was listed as a human pathogen for the first time in 1938 as cause of fatal puerperal fever [2]. Vaginal colonization rate in pregnant women is not equal between different geographical areas, the data world ranging from 5% to 30% [4], communicating data in the range of 1.4% to 18.15% for Argentina [5]. Published data for Misiones, a province of Argentina, show a colonization rate of 8.6% [6]. About 50% of babies born from these women are colonized with GBS during labor and 1% develop a severe infection [5]
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