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INTRODUCTION: Among beta-hemolytic streptococci, Streptococcus pyogenes causes a wide variety of human disease including pharyngitis, necrotizing fasciitis and streptococcal toxic syndrome. Group A Streptococcus (GAS) uses a variety of virulence traits to colonize and then cause damage to the host; others species of beta-hemolytic streptococci are considered as emerging pathogens for humans. Despite its recognized virulence, only few studies have investigated virulence factors of GAS strains isolated in Mexico. METHODOLOGY: We conducted an epidemiological study to investigate the prevalence of GAS strains in child illnesses in Chiapas Mexico. Virulence genes encoding proteases, DNases, superantigens, as well as susceptibility to antibiotics were investigated. RESULTS: During 2010, 2013 and 2014, beta-hemolytic streptococci (N=12) were isolated from cases of bacterial infections including pharyngitis and bacteremia, with a prevalence of 0.42, 0.04 and 0.20%, respectively. S. pyogenes was the most frequent species (33%) followed by S. agalactiae and S. dysgalactiae subsp. equisimilis (25%, each). Most GAS strains encoded genes for proteases: scpA, speB, spyCEP and mac (75%), followed by sdaD and sdaB (DNases) (50%), speA and speG (superantigens; 50 and 25%, respectively). The scpA gene was amplified in all S. agalactiae strains and in ~35% of SDSE strains. Strains were all susceptible to beta-lactams, cephalosporins and quinolones. CONCLUSIONS: The present study provides evidence on the epidemiology of beta-hemolytic streptococci infecting children at the southeast Mexico, their virulence traits and sensitivity to first-line antibiotics.
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BACKGROUND AND AIMS: Streptococcus pneumoniae constitutes one of the main causes of sepsis, bacteremia and meningitis (pneumococcal invasive disease - PID), and pneumonia in infants and small children. Antipneumococcal vaccination in Mexico is expected to be a useful strategy to reduce morbimortality due to this cause. We undertook this study to determine the prevalence of PID and pneumonia and the PCV vaccination status of affected children as well as serotype distribution and antimicrobial susceptibility of pneumococcal strains responsible for PID in infants and small children in Mexico. METHODS: From March 2010-June 2011, a prospective multicenter study was carried out in four states in Mexico to determine the prevalence of bacteremia, meningitis, septic arthritis and pneumonia due to S. pneumoniae and other microorganisms in children from 28 days-59 months of age. Isolated pneumococcal strains were serotyped and their antimicrobial resistance determined. RESULTS: During the study period, 545 children were diagnosed with bacteremia, meningitis, septic arthritis or pneumonia; 46.7% of these clinical entities occurred among children <12 months of age. Community-acquired pneumonia was the most prevalent disease. It was possible to identify a causal microorganism in 55 cases, from which 80% were S. pneumoniae. Fifteen percent of patients with PID died. The most prevalent pneumococcal serotypes were 19A, 35B, 19F and 6A. 10.2% of nonmeningeal strains were resistant to meropenem and 82% were resistant to TMP/SMX. CONCLUSIONS: This study shows that pneumococcus was the most common bacteria isolated in the studied population, although epidemiological and laboratory-based surveillance still needs improvement.