In vitro assessment of the ability of probiotics, blueberry and food carbohydrates to prevent S. pyogenes adhesion on pharyngeal epithelium and modulate immune responses.

Group A streptococci (GAS) cause 20-30% of pediatric pharyngitis episodes, which are a major cause of ambulatory care visits. Therefore, a strategy to prevent GAS dissemination in children could significantly benefit public healthcare. Contextually, we assessed the possibility of employing alternative food-grade strategies to be used with the oral probiotic L. helveticus MIMLh5 for the prevention of pharyngeal infections. First, we demonstrated through an antagonism-by-exclusion assay that guaran may potentially prevent S. pyogenes adhesion on pharyngeal cells. Subsequently, we showed that an anthocyanin-rich fraction extracted from wild blueberry (BbE) exerts anti-inflammatory effects on the human macrophage cell line U937. Finally, we showed that BbE reduces interferon-ß expression in MIMLh5-stimulated murine dendritic cells, resulting in a reduction in the pro-inflammatory cytokines IL-12 and TNF-α. In conclusion, this proof-of-concept study indicates that different food-grade strategies may be concomitantly adopted to potentially prevent GAS colonization and modulate local immune defences.

L-proline increases survival of tilapias infected by Streptococcus agalactiae in higher water temperature.

Streptococcosis causes massive tilapia kills, which results in heavy economic losses of tilapia farming industry. Out of the Streptococcosis, Streptococcus agalactiae is the major pathogen. The bacterium causes higher mortality of tilapias in higher than lower temperatures. However, effect of temperature on metabolic regulation which is related to the mortality is largely unknown. The present study showed 50% and 70% mortality of tilapias cultured in 25 °C and 30 °C, respectively, in comparison with no death in 20 °C following infection caused by S. agalactiae. Then, GC/MS based metabolomics was used to investigate a global metabolic response of tilapia liver to the two higher water temperatures compared to 20 °C. Thirty-six and forty-five varied abundance of metabolites were identified in livers of tilapias cultured at 25 °C and 30 °C, respectively. More decreasing abundance of amino acids and increasing abundance of carbohydrates were detected in 30 °C than 25 °C groups. On the other hand, out of the pathways enriched, the first five biggest impact pathways belong to amino acid metabolism. Decreasing abundance of l-proline was identified as a crucial biomarker for indexing higher water temperature and a potential modulator to reduce the high death. This was validated by engineering injection or oral addition of l-proline. Exogenous l-proline led to elevated amino acid metabolism, which contributes to the elevated survivals. Our findings provide a potential metabolic modulator for controlling the disease, and shed some light on host metabolic prevention to infectious diseases.

Genotyping of erythromycin resistant group C & G streptococci isolated in Chennai, south India.

BACKGROUND & OBJECTIVES: Increasing resistance to erythromycin has been observed worldwide in group C and group G streptococci (GCS/GGS). The information available from India is scanty. The aim of the study was to identify erythromycin resistant GCS/GGS isolates in Chennai, south India, and to compare erythromycin resistant genotypes with emm types. METHODS: One hundred and thirty one GCS/GGS isolates were tested for erythromycin resistance by disc diffusion and agar dilution methods. Erythromycin resistance genotypes [erm(A), erm(B) and mef(A)] were determined by a multiplex PCR. emm types of erythromycin resistant GCS/GGS isolates was also assessed using emm gene sequencing method. RESULTS: Sixteen of the 131 isolates (12.21%) were resistant to erythromycin. Majority of the isolates were GGS (15/16). Eight of the 16 (50%) were S. dysgalactiae subsps. equisimilis. Twelve isolates (75%) were MLS B phenotype and four (25%) were M phenotype. Of the 12 isolates which exhibited MLS B resistance, seven showed cMLS B phenotype and were positive for erm(B) gene. The remaining five were iMLS B phenotype of which three were positive for erm(A) gene and two for erm(B) gene. erm(A) was common among carriers whereas erm(B) was common among clinical isolates. INTERPRETATION & CONCLUSIONS: MLS B was the predominant phenotype and erm(B) was the common genotype in the present study. The emm type stC1400.0 was frequently associated with erythromycin resistant GCS/GGS in our study.

TroA of Streptococcus suis is required for manganese acquisition and full virulence.

Streptococcus suis causes infections in pigs and occasionally in humans, resulting in manifestations as meningitis, sepsis, arthritis, and septic shock. For survival within the host, S. suis requires numerous nutrients including trace metals. Little is known about the specific proteins involved in metal scavenging in S. suis. In this study we evaluated the role of the putative high-affinity metal binding lipoprotein TroA in metal acquisition and virulence. A mutant strain deficient in the expression of TroA (ΔtroA mutant) was constructed. Growth of the ΔtroA mutant in Todd-Hewitt broth was similar to wild-type growth; however, growth of the ΔtroA mutant in cation-deprived Todd-Hewitt broth and in porcine serum was strongly reduced compared to growth of wild-type bacteria. Supplementing the medium with extra manganese but not with magnesium, zinc, copper, nickel, or iron restored growth to wild-type levels, indicating that TroA is specifically required for growth in environments low in manganese. The ΔtroA mutant also showed increased susceptibility to H2O2, suggesting that TroA is involved in counteracting oxidative stress. Furthermore, the expression of the troA gene was subject to environmental regulation at the transcript level. In a murine S. suis infection model, the ΔtroA mutant displayed a nonvirulent phenotype. These data indicate that S. suis TroA is involved in manganese acquisition and is required for full virulence in mice.