RESUMEN
OBJECTIVE: Determining nasal carriers of methicillin-resistant Staphylococcus aureus (MRSA) and associated risk factors for nasal colonisation in a school-aged population in the seaside city of Cartagena, Colombia. METHODS: A cross-sectional, analytical study was carried out on 100 healthy schoolchildren to determine MRSA nasal carriage and its association with risk factors. Bacteria were identified using conventional methods. Antibiotic sensitivity was determined by the Kirby Bauer method. RESULTS: A total of 36 isolates of S. aureus were identified in the school children. 25 % of the strains were oxacillin-resistant, 66.7 % oxacillin-sensitive and 8.3 % had intermediate susceptibility. 67 % of the MRSA strains isolated were sensitive to all antibiotics tested. One strain (MRSA-Ant4) showed resistance to antibiotics having different mechanisms of action. CONCLUSIONS: This is the first study in Cartagena which determined the frequency of S. aureus and MRSA strains nasal carriers in a school population (33 % and 9 %, respectively). All S. aureus oxacillin-resistant strains were cephoxitin-resistant, thereby leading to the presence of the mecA gene being suspected. Having used beta-lactam antibiotics during the last three months increased the likelihood of being an MRSA nasal carrier by around five times (OR=4.72; 0.96-23.98 95 %CL; p<0.05). The antibiotypes (Ant) found suggested the presence of community-acquired (multisensitive CA-MRSA,) and hospital-acquired-MRSA (multidrug resistant HA-MRSA,).