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Updated: Jul 15, 2025
Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Antimicrobial resistance and its detection in Staphylococcus saprophyticus urinary isolates
Kyra Y L Chua1, May Yang2, Lillian Wong2
1Department of Microbiology, Dorevitch Pathology, Vic, Australia; Department of Infectious Diseases, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Vic, Australia; Department of Infectious Diseases, Austin Health, Vic, Australia.
Antibiotic resistance in Staphylococcus saprophyticus urinary isolates is uncommon, with high susceptibility to trimethoprim, nitrofurantoin, and ciprofloxacin. Methicillin resistance, detected by mecA PCR, was the most frequent resistance observed.
Area of Science:
- Clinical microbiology
- Antimicrobial resistance
- Urology
Background:
- Staphylococcus saprophyticus is a common cause of urinary tract infections, particularly in young women.
- Understanding its antibiotic susceptibility patterns is crucial for effective empirical treatment.
- Previous studies have shown varying resistance rates, necessitating ongoing surveillance.
Purpose of the Study:
- To determine the antibiotic susceptibility profile of clinical Staphylococcus saprophyticus isolates from urine specimens.
- To evaluate the prevalence of methicillin resistance in these isolates.
- To assess the appropriateness of current empiric antibiotic recommendations.
Main Methods:
- Prospective collection of urine specimens from September to October 2022 in Melbourne, Australia.
- Species identification using Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS).
- Phenotypic antibiotic susceptibility testing (AST) via disc diffusion and VITEK2, alongside mecA gene detection by polymerase chain reaction (PCR).
Main Results:
- A total of 302 S. saprophyticus isolates were analyzed, predominantly from non-hospitalized patients.
- High susceptibility rates were observed for trimethoprim (97%), trimethoprim/sulfamethoxazole (98%), nitrofurantoin (100%), and ciprofloxacin (100%).
- Methicillin resistance, confirmed by mecA PCR, was present in 5.6% of isolates; VITEK2 showed poor specificity for detecting this.
Conclusions:
- Empiric antibiotic treatment with trimethoprim, trimethoprim/sulfamethoxazole, and nitrofurantoin remains appropriate for urinary S. saprophyticus infections.
- Methicillin resistance is the most common resistance mechanism, highlighting the importance of mecA detection.
- Routine phenotypic testing for methicillin resistance may be unreliable, emphasizing the need for genotypic confirmation.
