title: Interpersonal relationships and group A streptococcus spread in a Mexican day-care center.
abstract: OBJECTIVE
  To study the effect of different degrees of centrality on the carrying of identical group A streptococcus (GAS) clones in the nasopharynx of children from a Mexican public day-care center.
  
  
  METHODS
  Nasopharyngeal cultures were performed in children from rooms B (RB) (n = 35) and C (RC) (n = 37). The Restriction Fragment Length Polymorphism (RFLP) patterns were compared among GAS isolates. A social networks questionnaire was filled out for each child and 10 classmates. Structure coefficients were compared among children with and without GAS.
  
  
  RESULTS
  Four GAS clones were identified; clone I in five children from RC; clone II in two from RC and one from RB; clone III in one from RB and one from RC; and clone IV in one from RC. Social network structure: Density of RB and RC = 0.40 (+/- 0.87) and 0.35 (+/- 0.80), respectively. In RB, the homophily pattern of interaction was different in carriers (0.00), non-carriers (0.47) and both (0.47) p = 0.35. In RC, the homophily pattern was also different in carriers (0.46), non-carriers (0.68) and mixed (0.19), p = .001. In 4/5 with clone I, the values of degree, closeness and betweenness were above the group mean. In 3/3 with clone II, the values of degree and betweenness were also above the mean. In contrast, in those with clone III and IV, the values of degree, closeness and betweenness were below the group mean.
  
  
  CONCLUSIONS
  The spread of specific GAS clones was associated with groups of children having a high proportion of ties and a high centrality level. This is evidence that spread of GAS strains among children attending day-care centers is not random but dependent on the degree of communication and physical contact between pairs.
authors.affiliation: Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social, Guadalajara, Jalisco, México. avillase@prodigy.net.mx
authors.forename: Alberto
authors.initials: A
authors.lastname: Villaseñor-Sierra
authors.forename: Mayra G
authors.initials: MG
authors.lastname: Quiñonez-Alvarado
authors.forename: José Ramiro
authors.initials: JR
authors.lastname: Caballero-Hoyos
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D002353:Carrier State / Q000453:epidemiology / Q000382:microbiology*; D002656:Child Day Care Centers / Q000706:statistics & numerical data; D002675:Child, Preschool; D002999:Clone Cells; D018562:Disease Transmission, Infectious / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D008800:Mexico / Q000453:epidemiology; D009305:Nasopharynx / Q000382:microbiology*; D012150:Polymorphism, Restriction Fragment Length; D012141:Respiratory Tract Infections / Q000188:drug therapy / Q000453:epidemiology; D012944:Social Support; D013290:Streptococcal Infections / Q000453:epidemiology / Q000382:microbiology / Q000635:transmission*; D013297:Streptococcus pyogenes / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D000900:Anti-Bacterial Agents