Staphylococcus aureus is one of the main causes of bloodstream infection (BSI), and prior colonization is an important risk factor for acquisition of these infections. It represents a public health challenge due to its virulence and ability to develop antimicrobial resistance, especially MRSA (methicillin-resistant S. aureus) strains. During the COVID-19 pandemic, increased antimicrobial use contributed to rising bacterial resistance rates. The objective of this study was to characterize paired colonization and infection S. aureus samples obtained from ICU patients in a university hospital in Rio de Janeiro during the COVID-19 pandemic. Species confirmation was performed by MALDI-TOF-MS and susceptibility profiles were determined for 11 antimicrobials using disk diffusion. Clonal diversity was assessed by PFGE and MLST techniques. Among 96 hospitalized patients, from September/2020 to March/2021, five (5.21%) had paired S. aureus samples obtained from nasal swab and BSI, with three diagnosed with COVID-19. Thirteen clinical specimens were obtained: seven nasal swabs and six BSI isolates. Two patients had two positive swabs and another patient had two BSI episodes. Among S. aureus isolates, 46.2% (6/13) were MRSA, isolated from four patients with and without COVID-19. In addition, 15.4% (2/13), 53.8% (7/13), 61.5% (8/13), and 100% (13/13) of isolates were resistant to ciprofloxacin, clindamycin, erythromycin, and penicillin, respectively. Inducible MLSb phenotype was detected in 71.4% (5/7) of clindamycin-resistant isolates. All isolates were susceptible to tetracycline, linezolid, trimethoprim-sulfamethoxazole, rifampicin, gentamicin, and mupirocin. The five patients each presented nasal and BSI isolates of the same genotype and with similar susceptibility profiles, and hospital clones (USA800/ST5/IV and USA100/ST105/II) and a community clone (CC398) were identified. The presence of the same S. aureus genotype causing BSI and colonizing hospitalized individuals reinforces the importance of prior colonization by this pathogen, confirming the relevance of constant microbiological surveillance, especially during periods of greater selective pressure such as COVID-19, when higher antimicrobial resistance was detected among pathogens.
Igari et al. (Sun,) studied this question.