The prevalence and molecular mechanisms of mupirocin resistance in Staphylococcus aureus isolates from a Hospital in Cape Town, South Africa
Date
2020-03-14
Journal Title
Journal ISSN
Volume Title
Publisher
BMC (part of Springer Nature)
Abstract
Abstract
Background: Antimicrobial resistance is an increasingly serious problem in public health globally. Monitoring
resistance levels within healthcare and community settings is critical to combat its ongoing increase. This study
aimed to describe the rates and molecular mechanisms of mupirocin resistance in clinical Staphylococcus aureus
isolates from Tygerberg Hospital, and to describe its association with strain types.
Methods: We retrospectively selected 212 S. aureus isolates which were identified from blood samples and pus
swabs during the years 2009–2011 and 2015–2017. The isolates were identified using conventional microbiological
methods and genotyping was done using spa typing. Cefoxitin (30 μg) disc diffusion and the two disc strategy
(5 μg and 200 μg) were used to determine susceptibility to methicillin and mupirocin, respectively. Isolates with
high-level resistance were screened for the plasmid mediated genes mupA and mupB by PCR, and sequencing of
the ileS gene was done for all isolates exhibiting low-level resistance to describe the mutations associated with this
phenotype. Chi-square test was used to assess the associations between mupirocin resistance and S. aureus
genotypes.
Results: Of 212 S. aureus isolates, 12% (n = 25) were resistant to mupirocin, and 44% (n = 93) were methicillin
resistant. Strain typing identified 73 spa types with spa t045 being the most predominant constituting 11% of the
isolates. High-level mupirocin resistance was observed in 2% (n = 5), and low-level resistance in 9% (n = 20) of the
isolates. The prevalence of high-level mupirocin resistance amongst MRSA and MSSA was 4 and 1% respectively,
while the prevalence of low-level mupirocin resistance was significantly higher in MRSA (18%) compared to MSSA
(3%), (p = 0.032). mupA was the only resistance determinant for high-level resistance, and the IleS mutation V588F
was identified in 95% of the isolates which showed low-level resistance. A significant association was observed
between spa type t032 and high-level mupirocin resistance, and types t037 and t012 and low-level resistance
(p < 0.0001). Conclusion: The study reported higher rates of low-level mupirocin resistance compared to high-level resistance,
and in our setting, mupirocin resistance was driven by certain genotypes. Our study advocates for the continuous
screening for mupirocin resistance in S. aureus in clinical settings to better guide treatment and prescribing
practices.
Background
Antimicrobial resistance is an increasingly serious problem in public health globally. Monitoring resistance levels within healthcare and community settings is critical to combat its ongoing increase. This study aimed to describe the rates and molecular mechanisms of mupirocin resistance in clinical Staphylococcus aureus isolates from Tygerberg Hospital, and to describe its association with strain types.
Methods
We retrospectively selected 212 S. aureus isolates which were identified from blood samples and pus swabs during the years 2009–2011 and 2015–2017. The isolates were identified using conventional microbiological methods and genotyping was done using spa typing. Cefoxitin (30 μg) disc diffusion and the two disc strategy (5 μg and 200 μg) were used to determine susceptibility to methicillin and mupirocin, respectively. Isolates with high-level resistance were screened for the plasmid mediated genes mupA and mupB by PCR, and sequencing of the ileS gene was done for all isolates exhibiting low-level resistance to describe the mutations associated with this phenotype. Chi-square test was used to assess the associations between mupirocin resistance and S. aureus genotypes.
Results
Of 212 S. aureus isolates, 12% (n = 25) were resistant to mupirocin, and 44% (n = 93) were methicillin resistant. Strain typing identified 73 spa types with spa t045 being the most predominant constituting 11% of the isolates. High-level mupirocin resistance was observed in 2% (n = 5), and low-level resistance in 9% (n = 20) of the isolates. The prevalence of high-level mupirocin resistance amongst MRSA and MSSA was 4 and 1% respectively, while the prevalence of low-level mupirocin resistance was significantly higher in MRSA (18%) compared to MSSA (3%), (p = 0.032). mupA was the only resistance determinant for high-level resistance, and the IleS mutation V588F was identified in 95% of the isolates which showed low-level resistance. A significant association was observed between spa type t032 and high-level mupirocin resistance, and types t037 and t012 and low-level resistance (p < 0.0001).
Conclusion
The study reported higher rates of low-level mupirocin resistance compared to high-level resistance, and in our setting, mupirocin resistance was driven by certain genotypes. Our study advocates for the continuous screening for mupirocin resistance in S. aureus in clinical settings to better guide treatment and prescribing practices.
Description
CITATION: Abdulgader, S. M., et al. 2020. The prevalence and molecular mechanisms of mupirocin resistance in Staphylococcus aureus isolates from a Hospital in Cape Town, South Africa. Antimicrobial Resistance and Infection Control, 9:47, doi:10.1186/s13756-020-00707-8.
The original publication is available at https://aricjournal.biomedcentral.com
Publication of this article was funded by the Stellenbosch University Open Access Fund
The original publication is available at https://aricjournal.biomedcentral.com
Publication of this article was funded by the Stellenbosch University Open Access Fund
Keywords
Molecular immunology, Anti-infective agents, Staphylococcus aureus infections, Mupirocin, Drug resistance
Citation
Abdulgader, S. M., et al. 2020. The prevalence and molecular mechanisms of mupirocin resistance in Staphylococcus aureus isolates from a Hospital in Cape Town, South Africa. Antimicrobial Resistance and Infection Control, 9:47, doi:10.1186/s13756-020-00707-8