Antibiotic resistance of Staphylococcus aureus strains isolated from the pharynx and nose of young adults

Introduction: Staphylococcus aureus is a bacterium that lives in symbiosis with humans, it is an opportunistic and potentially lethal pathogen of clinical importance. Approximately 30% or more of the population is colonized with S. aureus on the skin, mucous membranes, or in the nose. The mechanisms of colonization and persistence of S. aureus in the human nose have been extensively studied, however, it must be admitted that the clinical relevance of S. aureus carriers in the pharynx has not been extensively investigated. The aim of this work was determinate the antibiotic resistance of S. aureus strains isolated from the pharynx and nose of young adults. Methods: Pharyngeal and nasal exudates were made to 134 University students of Health Science, once a month for three months. The exudate samples taken were incubated for 24 hours at 37 ºC for their subsequent sowing on the Salt-Mannitol agar. Identification of S. aureus strains is done by reseeding and isolating mannitol and coagulase positive fermenting bacteria. If a person registered three or more isolates of S. aureus in a row, he was considered a persistent carrier. The strains identified as S. aureus underwent the antibiogram test and MIC for oxacillin. Results: 62% of carriers presented S. aureus in pharynx and 36% in the nose. Only 17% of carriers presented S. epidermidis in the pharynx and 53% in the nose. Likewise, 35% were exclusive carriers of S. aureus in pharynx, 10% exclusive in the nose, 25% carriers in both sites, and 27% non-carriers. In addition, 49% are persistent carriers in the pharynx and 19% in the nose, 22% are intermittent carriers in the pharynx and 30% in the nose. Non-carriers of S. aureus in the pharynx and nose were 24% and 50%, respectively. 67% of S. aureus strains are resistant to penicillin, 23% resistant to clindamycin, 20% to erythromycin. Only 6% of the strains isolated from the pharynx and 5% from the nose are MRSA. Conclusion: The presence of S. aureus was greater in the pharynx than in the nose. The main antibiotic to which they are resistant is penicillin followed by clindamycin and erythromycin. A low percentage of MRSA strains was found.