Object: To determine the prevalence and incidence of Staphylococcus aureus strains among preschool- and school-aged pupils and susceptibility of these strains to antimicrobial materials.
Material and methods: A study of 243 preschool- and 300 school-aged pupils was conducted during 2003-2004. Identification of Staphylococcus aureus was made with plasmacoagulase and DNase tests. The resistance of Staphylococcus aureus to antibiotics, beta-lactamase activity, phagotypes, and phage groups were determined. The isolated Staphylococcus aureus strains were tested for resistance to methicillin by performing disc diffusion method using commercial discs (Oxoid) (methicillin 5 microg per disk and oxacillin 1 microg per disk).
Results: A total of 292 (53.8%) Staphylococcus aureus strains were isolated and identified (113 (46.5%) from preschool- and 179 (59.7%) from school-aged pupils). The prevalence of Staphylococcus aureus strains among preschool-aged pupils varied from 46.5% to 47%. It increased to 59.0% (P>0.05) among schoolchildren aged from 11 to 15 years and to 73.0% (P<0.001) among schoolchildren aged from 16 to 19 years. Six methicillin-resistant Staphylococcus aureus strains were isolated: two (1.8%) of them were from preschool-aged and four (2.2%) from school-aged pupils. The prevalence of Staphylococcus aureus strains with beta-lactamase activity increased from 70.7 to 76.6% in preschool-aged pupils, and it varied from 72.0 to 79.0% in school-aged pupils (P>0.05). Staphylococcus aureus strains of phage group II (32.2-43.4%) were prevailing; nontypable Staphylococcus aureus strains made up 19.2-33.6%.
Conclusions: The prevalence of Staphylococcus aureus among preschool-aged children is 41.7 to 48.8%, and it increases among 9th-12th-grade pupils (73.0%, P<0.001). Some Staphylococcus aureus strains (2.1%) were resistant to methicillin. Staphylococcus aureus strains of phage group II (39.0%, P<0.05) are most prevalent among preschool- and school-aged pupils. Pupils were colonized with methicillin-resistant Staphylococcus aureus strains belonging to phage group III phagotype 83A and 77.