Resistance profile to antimicrobials agents in methicillin-resistant Staphylococcus aureus isolated from hospitals in South Brazil between 2014-2019

Abstract

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) is a common pathogen causing healthcare-associated infections. Owing to the restricted use of beta-lactams in MRSA infections, non-beta-lactam antimicrobials are required for treatment. However, MRSA can develop resistance mechanisms to non-beta-lactam antimicrobials, which reduces viable treatment options. Here, we evaluated the antimicrobial susceptibility and resistance genes of MRSA isolated from hospitalized patients in South Brazil. Methods: The antimicrobial susceptibilities of hospital MRSA (217) isolates were determined by disk diffusion or microdilution methods. Additionally, the presence of 14 resistance genes and SCCmec typing was performed by PCR. Results: Among the antimicrobials tested, we observed high erythromycin (74.2%), ciprofloxacin (64.5%), and clindamycin (46.1%) resistance rates and complete susceptibility to linezolid and vancomycin. Seventeen different patterns of MRSA antimicrobial resistance were observed, of which 42.9% represented multidrug resistance. Among erythromycin-resistant MRSA, 53.4%, 45.3%, 37.9%, 13.0%, and 6.8% carried ermA, msrA, msrB, ermC, and ermB genes, respectively. Among clindamycin-resistant MRSA, 83%, 17%, 10%, 4%, and 2% carried ermA, ermC, ermB, linA, and linB genes, respectively. Among gentamicin-resistant MRSA, 96.8%, 83.9%, and 9.7% carried aac(6')/aph(2''), aph(3')-IIIa, and ant(4')-Ia genes, respectively. Among tetracycline-resistant MRSA, 6.5% and 93.5% carried tetK and tetM genes, respectively. Lastly, among trimethoprim/sulfamethoxazole-resistant MRSA, 13.3% and 100% carried dfrA and dfrG genes, respectively. The SCCmec type IV isolates were detected more frequently, whereas the SCCmec type III isolates exhibited higher multidrug resistance. Conclusions: The study data provides information regarding the MRSA resistance profile in South Brazil that is associated with the clinical conditions of patients and can contribute to clinical decision-making.

Mechanisms of Resistance to Macrolide Antibiotics among Staphylococcus aureus

“…The MRSA strains show resistance to MLS B antibiotics mostly determined by the presence of the ermA or ermC genes. On the other hand, among MSSA strains, the ermC followed by ermB gene is usually observed [16,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. The research on the occurrence of msr genes among MRSA and MSSA is much less frequent.…”

Prevalence and Characterization of Methicillin-Resistant Staphylococcus aureus from Community- and Hospital-Associated Infections: A Tertiary Care Center Study

“…Studies showed that CA-MRSA contain SCC mec types IV and V, mostly with the PVL gene, while HA-MRSA carry SCC mec types I, II and III [ 13 ]. HA-MRSA are commonly associated with nosocomial infections and are resistant to non-β-lactam antibiotics such as fluoroquinolones, macrolides and aminoglycosides [ 14 ]. HA-MRSA generally do not possess the PVL gene and belong to the SCC mec types I, II and III [ 15 ].…”

Bacterial Targets of Antibiotics in Methicillin-Resistant Staphylococcus aureus

“…Beyond resistance to β-lactams, MRSA is often resistant to other classes of antibiotics currently in clinical use. The majority of HA-MRSA are resistant to non-β-lactams, such as aminoglycosides, lincosamides, fluoroquinolones, and macrolides [ 59 ], but resistance to standard-of-care drug vancomycin and linezolid is uncommon [ 60 ]. The emergence of vancomycin-resistant S. aureus (VRSA) is the most worrying S. aureus genetic adaptation due to the reliance on this antibiotic in the treatment of MRSA infections [ 15 ].…”