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Antibiotic susceptibility profile and prevalence of mecA and lukS-PV/lukF-PV genes in Staphylococcus aureus isolated from nasal and pharyngeal sources of medical students in Ecuador

Authors Bastidas CA, Villacrés-Granda I, Navarrete D, Monsalve M, Coral-Almeida M, Cifuentes SG

Received 13 June 2019

Accepted for publication 22 July 2019

Published 16 August 2019 Volume 2019:12 Pages 2553—2560

DOI https://doi.org/10.2147/IDR.S219358

Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 2

Editor who approved publication: Dr Joachim Wink


Carlos A Bastidas,1,* Irina Villacrés-Granda,2,* Daniela Navarrete,1 Mishell Monsalve,1 Marco Coral-Almeida,3 Sara G Cifuentes4,*

1Facultad de Ingenierías y Ciencias Aplicadas, Biotecnología, Universidad de Las Américas, Quito, Ecuador; 2Laboratorios de Investigación, Universidad de Las Américas, Quito, Ecuador; 3One Health Research Group, Facultad de Ciencias de la Salud, Universidad de Las Américas, Quito, Ecuador; 4Escuela de Medicina, Facultad de Ciencias de la Salud, Universidad de Las Américas, Quito, Ecuador

Correspondence: Carlos A Bastidas
Facultad de Ingenierías y Ciencias Aplicadas, Biotecnología, Universidad de Las Américas, Jose Queri and Av. Granados, Quito, Ecuador
Tel +593 99 640 1999
Email carlos.bastidas@udla.edu.ec

Irina Villacrés-Granda
Laboratorios de Investigación, Universidad de Las Américas, Jose Queri and Av. Granados, Quito, Ecuador
Tel +593 99 640 1999
Email irina.villacres@udla.edu.ec

*These authors contributed equally to this work

Background: Staphylococcus aureus is a common nasal colonizer in 20–30% of the general population. When mucosal and cutaneous barriers are disrupted, S. aureus can cause severe infections. While MRSA nasal carriers have an increased risk of infections when compared to non-carriers, prolonged exposure to the hospital environment may cause an increase in carriage of MRSA.
Materials and methods: A survey questionnaire was filled for analyzing risk factors of colonization. Swab isolates were identified as S. aureus by traditional microbiological assays. Antibiotic susceptibility profiles were performed following the CLSI standard guidelines. Multiplex PCR was conducted to determine the presence of genes mecA and lukS-PV/lukF-PV. Chi-squared, univariate, and multivariate logistic regressions were applied to find statistically significant associations between risk factors and the presence of S. aureus and MRSA.
Results: One hundred and eighty-six isolates were identified as S. aureus. The strains showed high resistance to penicillin, oxacillin, azithromycin, erythromycin, clindamycin (inducible), and tetracycline. The overall prevalence of MRSA in medical students was 45.9% [40.4–51.6] 95% CI. PCR showed a prevalence of mecA gene in MRSA isolates of 6.1% while lukS-PV/lukF-PV gene was present in 3.2% [1.2–6.9] 95% CI of the S. aureus samples. The risk factors frequency of antibiotic intake and repeated visits to hospitals demonstrated statistical significance.
Conclusion: S. aureus and MRSA isolates have a high prevalence of colonization, and antibiotic resistance in the population studied. MRSA resistance was not related to the presence of the mecA gene. The prevalence of PVL genes was low, but it could represent a risk because they are circulating in the community.

Keywords: mecA, medical students, MRSA, Panton-Valentine leukocidin, Staphylococcus aureus

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