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Fifteen percent of all methicillin-resistant Staphylococcus aureus (MRSA) clonal complex 398 (CC398) human carriers detected in The Netherlands had not been in direct contact with pigs or veal calves. To ensure low MRSA prevalence, it is important to investigate the likely origin of this MRSA of unknown origin (MUO). Recently, it was shown that CC398 strains originating from humans and animals differ in the presence of specific mobile genetic elements (MGEs). We hypothesized that determining these specific MGEs in MUO isolates and comparing them with a set of CC398 isolates of various known origin might provide clues to their origin. MUO CC398 isolates were compared to MRSA CC398 isolates obtained from humans with known risk factors, a MRSA CC398 outbreak isolate, livestock associated (LA) MRSA CC398 isolates from pigs, horses, chickens, and veal calves, and five methicillin-susceptible Staphylococcus aureus (MSSA) CC398 isolates of known human origin. All strains were spa typed, and the presence or absence of, scn, chp, φ3 int, φ6 int, φ7 int, rep7, rep27, and cadDX was determined by PCRs. The MRSA CC398 in humans, MUO, or MRSA of known origin (MKO) resembled MRSA CC398 as found in pigs and not MSSA CC398 as found in humans. The distinct human MSSA CC398 spa type, t571, was not present among our MRSA CC398 strains; MRSA CC398 was tetracycline resistant and carried no φ3 bacteriophage with scn and chp. We showed by simple PCR means that human MUO CC398 carriers carried MRSA from livestock origin, suggestive of indirect transmission. Although the exact transmission route remains unknown, direct human-to-human transmission remains a possibility as well., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

Determinants of bacterial colonization in children have been described. In the Generation R Study, a population-based cohort study, we determined whether the colonization statuses of mothers and children are correlated. Such a correlation was observed for Staphylococcus aureus and Haemophilus influenzae. Direct transmission, genetic susceptibility and/or unidentified environmental factors may play a role here.

Forty strains of methicillin-resistant Staphylococcus aureus (MRSA) were divided on the basis of their epidemiologic behavior into two subgroups, sporadic MRSA (SMRSA) and epidemic MRSA (EMRSA) strains. The strains were examined for binding of 125I-labelled fibronectin, vitronectin, collagen, Fc fragments of immunoglobulin G, and fibrinogen. A significant difference between EMRSA and SMRSA strains was found for binding of 125I-labelled fibrinogen and for Fc fragments of immunoglobulin G, (P < 0.05). No significant difference in the binding of 125I-labelled fibronectin and collagen was found between EMRSA and SMRSA strains. The binding of 125I-labelled vitronectin to MRSA strains was found to be aspecific. Capsular serotypes of the strains were determined with monoclonal antibodies against capsular types 5 and 8. Strains could be divided into the following four groups: types 5, 8, and 5/8 and nontypeable. More nontypeable strains were found in the EMRSA group (66.6%). Significantly more EMRSA strains (79%) than SMRSA strains (44%) produced alpha-toxin (P < 0.025). Logistic regression analysis using a combination of the parameters 125I-labelled immunoglobulin G binding, capsular type, and alpha-toxin production predicted the epidemic character with a sensitivity of 83% and a specificity of 75%.