Variations in proteins related to bacterial diversity may affect species identification performed using matrix-assisted laser desorption ionization (MALDI)-time of flight mass spectrometry. Using this method, we identified 110 Streptococcus agalactiae isolates characterized by serotyping and multilocus sequence typing. Serotype III and sequence type 23 strains expressed the widest variation in molecular weight of putative "species-identifying" biomarker ions. Recognition of the diversity of MALDI patterns observed in strains that represent all major intraspecies lineages assists in the constitution of an optimal reference database.

No abstract

Streptococcus agalactiae carriage was evaluated by sampling four body sites in a group of 249 healthy individuals including both sexes and a wide range of ages; the aims were to study the population structure of colonizing strains by multilocus sequence typing (MLST) and to evaluate their diversity by serotyping, SmaI macrorestriction analysis, and PCR screening for genetic markers of highly virulent clones for neonates. The prevalences of carriage were 27% in women and 32% in men. The major positive body site was the genital tract (23% in women and 21% in men); skin, throats, and anal margins were also positive in 2%, 4%, and 14%, respectively. These human-colonizing strains belonged mostly to serotypes III (24%), Ia (21%), V (18%), and Ib (17%). Twenty-three sequence types ( Streptococcus agalactiae is the pathogen most commonly responsible for maternofetal and neonatal infections, and serogroup III sequence type (ST) 17 strains of this species have been identified as more likely to cause these infections (3,17,(24)(25)(26)28).S. agalactiae infections in nonpregnant adults have been reported increasingly since the 1970s (5,7,10,14,20,21,23,26,27). The major clinical forms consist of skin, soft tissue, and bone infections; bacteremia; urinary tract infections; pneumonia; and peritonitis. More rarely, S. agalactiae is responsible for septic arthritis, meningitis, and endocarditis. Risk factors have been identified (16) and include an age of over 60 years and diagnoses of diabetes, cancer, decubitus acutus, AIDS, longcourse corticotherapy, chronic renal disease, cirrhosis, and neurological vessel disorders. However, cases of invasive S. agalactiae infections in immunocompetent nonpregnant adults have recently been reported (7,20,21,23). The physiopathology of these infections is not well understood and may be linked in part to S. agalactiae strains with particular properties.Reports on the genetic characteristics of the strains associated with infections in adults showed that they are diverse and belong mostly to serotypes Ia, III, and V (5, 14) and clonal complexes 1, 9, 17, 19, and 23 (17).The portal of entry of these infections in adults is not often well documented. A better knowledge of the genetic characteristics of the S. agalactiae strains colonizing various body sites would contribute to a better understanding of the origin of infections in adults. Although the molecular features of S. agalactiae strains isolated during infectious diseases have been described in many cases, little is known about the molecular characteristics of human-colonizing strains. Therefore, we screened for S. agalactiae carriage in 249 healthy individuals of both sexes; the individuals were living at home and covered a range of ages, from the start of the teenage period until old age. Genital, skin, throat, and anal margin carriage was sampled by self-swabbing. The strains isolated were serotyped. The population structure of the strains was investigated by multilocus sequence typing (MLST). The genetic diversity of isolates was ev...