Nasal Carriage by Staphylococcus aureus among Healthcare Workers and Students Attending a University Hospital in Southern Brazil: Prevalence, Phenotypic, and Molecular Characteristics

Abstract

Background. Staphylococcus aureus can asymptomatically colonize the human anterior nares and skin, and nasal colonization by this bacterium represents a potential risk for development of invasive infections. The aim of this study was to determine the prevalence of S. aureus nasal carriage among healthcare workers and students attending a university hospital and to characterize the isolates phenotypically and molecularly. Methods. A cross-sectional study was performed with 324 volunteers. Cultures from nasal samples were obtained and S. aureus isolates were characterized according to their antimicrobial susceptibility profile and four virulence factors-encoding genes. MRSA isolates were characterized regarding their oxacillin/cefoxitin susceptibility, SCCmec, and REP-PCR types. Potential risks for S. aureus and MRSA carriage were analyzed. Results. Of 324 nasal samples, 42.9% were identified as S. aureus, of which 28.8% were MRSA. S. aureus carriers were significantly higher in males and students (OR = 2.898, 95%CI 1.553–5.410); however, no variables were associated with MRSA carriage. All isolates were susceptible to vancomycin and the highest rate of resistance was observed for penicillin (90.6%). All isolates harbored the coa gene, and 97.8%, the icaA gene; 15.8% and 6.5% were positive for tst and lukS-PV/lukF-PV genes, respectively. Among MRSA isolates, 45% carried the mecA gene but were phenotypically susceptible to oxacillin/cefoxitin; two harbored the tst and none had lukS-PV/lukF-PV genes. All MRSAs were distributed into six SCCmec types and type I (62.5%) was the most frequent. REP-PCR typing identified four main clusters among MRSA isolates. Conclusion. High prevalence of healthcare workers and students were identified as nasal carriers of S. aureus exhibiting different antimicrobial resistance profiles, including mecA-positive oxacillin-susceptible S. aureus (OS-MRSA) and the presence of virulence-encoding genes. Both cohorts may represent potential sources for the emergence of a successful S. aureus strain highly adapted to the hospital environment.

High Levels of Methicillin-Resistant Staphylococcus aureus Carriage Among Healthcare Workers at a Teaching Hospital in Addis Ababa Ethiopia: First Evidence Using mecA Detection

“…One of the encouraging results in our study is that, all isolates were sensitive to rifampicin and vancomycin, which is in line with studies in Nepal 29 and Southern Brazil, 24 suggesting these two drugs are still useful and effective for managing S. aureus and MRSA-related infections. Although the source population was different, a recent study in North Ethiopia also indicated the absence of resistance to these drugs.…”

“…The 78.2% penicillin resistance in this study was comparable with the 71% resistance reported in the Netherlands 22 but lower than two former studies done in Dessie and Adigrat, Ethiopia (100% resistant) 19 , 23 and 90.6% to 100% in Southern Brazil and Gaza. 21 , 24 The rate of multidrug-resistance was similar to reports from Dessie and Jimma, Ethiopia. 23 , 25 …”

Occurrence of methicillin-resistant Staphylococcus aureus (MRSA) in ‘coalho’ cheese produced in Brazil

“…Resistance to mecA has been correlated with the presence of the mecA gene for a long time. On the other hand, where resistance to oxacillin is concerned, the presence of S. aureus isolates positive for mecA but phenotypically susceptible to oxacillin (OS-MRSA) has been reported, including in Brazil (Guimarães et al ., 2017; Danelli et al ., 2020). These latter authors found strains of OS-MRSA in the nasal cavity of about 2000 health professionals and students from a university hospital in southern Brazil, raising an alert about the fact that these strains can be mistakenly identified as S. aureus sensitive to methicillin (MSSA) by phenotypic methods routinely used in most clinical laboratories, which would pose a threat to the treatment of staphylococcal infections.…”

“…Although S. aureus has been a known pathogen for a long time, isolates of methicillin-resistant S. aureus (MRSA) have been found since the 1980s, being responsible for hospital-acquired infections and showing the capacity to resist various antimicrobials. Currently, it has become a worldwide pathogen related to the community and food transmission (Gonzalez et al, 2017). The antimicrobial resistance capacity of S. aureus is the result of several factors, which include the production of β-lactamases (encoded by the blaZ gene) and alteration of the binding site for β-lactam antibiotics due to the production of an additional penicillin-binding protein present in methicillin-resistant strains of S. aureus (Song et al, 2016;Chen et al, 2017).…”

Adaptation of Bacteria to Antineoplastic Agents Involves Persister Cells and Increases Resistance to Antibiotics

“…A previous study carried out in the USA estimated that around 32.4% of the population were colonized with S. aureus but the prevalence of methicillin-resistant strains in the isolates was estimated to be 0.84% for the same population [ 72 ]. However, a higher percentage of methicillin-resistant strains has been found to be nasally carried by healthcare workers [ 73 , 74 ].…”