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. 2022 Sep 14;11(1):114.
doi: 10.1186/s13756-022-01154-3.

Pandemic clone USA300 in a Brazilian hospital: detection of an emergent lineage among methicillin-resistant Staphylococcus aureus isolates from bloodstream infections

Mariana Fernandes Augusto #  1 , Débora Cristina da Silva Fernandes #  2 , Tamara Lopes Rocha de Oliveira #  1 , Fernanda Sampaio Cavalcante  3 , Raiane Cardoso Chamon  4 , Adriana Lúcia Pires Ferreira  5 , Simone Aranha Nouér  6 ; Infection Control Group HUCFF/UFRJ; Kátia Regina Netto Dos Santos  7
Collaborators, Affiliations

Pandemic clone USA300 in a Brazilian hospital: detection of an emergent lineage among methicillin-resistant Staphylococcus aureus isolates from bloodstream infections

Mariana Fernandes Augusto et al. Antimicrob Resist Infect Control. .

Abstract

Background: Staphylococcus aureus is one of the leading causes of bloodstream infections (BSI) worldwide. In Brazil, the hospital-acquired methicillin-resistant S. aureus USA100/SCCmecII lineage replaced the previously well-established clones. However, the emergence of community-associated (CA) MRSA lineages among hospitalized patients is an increasing issue.

Methods: Consecutive S. aureus isolates recovered from BSI episodes of patients admitted between January 2016 and December 2018 in a Brazilian teaching hospital were tested for antimicrobial resistance, their genotypic features were characterized, and the clinical characteristics of the patients were evaluated.

Results: A total of 123 S. aureus isolates were recovered from 113 patients. All isolates were susceptible to linezolid, teicoplanin and vancomycin and 13.8% were not susceptible to daptomycin. Vancomycin MIC50 and MIC90 of 2 mg/L were found for both MRSA and MSSA isolates. The MRSA isolation rate was 30.1% (37/123), and 51.4% of them carried the SCCmec type II, followed by SCCmecIV (40.5%). Among the 37 MRSA isolates, the main lineages found were USA100/SCCmecII/ST5 and ST105 (53.7%) and USA800/ST5/SCCmecIV (18.9%). Surprisingly, six (16%) CA-MRSA isolates, belonging to USA300/ST8/SCCmecIVa that carried PVL genes and the ACME cassette type I, were detected. These six patients with USA300 BSI had severe comorbidities, including cancer, and most had a Charlson score ≥ 5; furthermore, they were in wards attended by the same health professionals. MRSA isolates were associated with hospital acquired infections (p = 0.02) in more elderly patients (p = 0.03) and those diagnosed with hematologic cancer (p = 0.04). Among patients diagnosed with MRSA BSI, 19 (54.3%) died.

Conclusions: The pandemic MRSA USA300 was detected for the first time in the Brazilian teaching hospital under study, and its cross-transmission most probably occurred between patients with BSI. This lineage may already be circulating among other Brazilian hospitals, which highlights the importance of carrying out surveillance programs to fight multidrug resistant and hypervirulent isolates.

Keywords: Bloodstream infections; MRSA; PVL genes; S. aureus; USA100; USA300.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Dendrogram of the PFGE patterns and characteristics related to the genetic background of 37 MRSA isolates recovered from bloodstream infections. Isolates showing a similarity coefficient ≥ 80% were considered genetically related. *PVL genes positive isolates; ST, Sequence type; SCCmec, Staphylococcal cassette chromosome mec; MIC, Minimum inhibitory concentration; OXA, oxacillin; VAN, vancomycin; DAP, daptomycin; MM, Month; DD, Day; YY, Year; Hem, Hematology; Neph, Nephrology; Vas Surg, Vascular Surgery; Emer, Emergence; Gen Surg, General Surgery; Int Med, Internal Medicine; Hep, Hepatology; Psyc, Psychiatry; Derm, Dermatology; ICU, Intensive Care Unit; Card, Cardiology; Ger, Geriatrics; Inf Dis, Infectious Disease; CCU, Coronary Care Unit; HA, Hospital-associated; HCA, Healthcare-associated; CA, Community-associated; BEC, Brazilian endemic clone; ND, not determined
Fig. 2
Fig. 2
Timeline distribution of the six patients who presented bloodstream infections caused by USA300/ST8/SCCmecIVa isolates according to hospital ward. BC—Blood culture positive for MRSA USA300; †Death as outcome
See this image and copyright information in PMC

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