Related Experiment Videos
Ciprofloxacin-resistant methicillin-resistant Staphylococcus aureus in an acute-care hospital
M C Raviglione1, J F Boyle, P Mariuz
1Cabrini Medical Center, New York, New York.
Abstract:
Use of ciprofloxacin as an alternative to vancomycin for treatment of methicillin-resistant Staphylococcus aureus infection has been paralleled by the emergence of resistant strains. This phenomenon has also been noticed in our hospital. To confirm our observation, methicillin and ciprofloxacin susceptibilities were tested by disk diffusion and broth microdilution techniques. We studied 83 methicillin-resistant Staphylococcus aureus isolates obtained from various sources over a 4-month period. Ciprofloxacin resistance (MIC, greater than 2 micrograms/ml) was detected in 69 isolates (83%). Prior use of ciprofloxacin was reported for 24 of 69 patients with ciprofloxacin-resistant strains and 0 of 14 patients with ciprofloxacin-susceptible strains. The day of detection during the hospital stay and the location of the source patient were not significantly different between resistant and susceptible strains. Bacteriophage typing showed a higher occurrence of nontypeable strains among ciprofloxacin-resistant strains (54%). Review of our microbiology register showed a progressive increase in the rate of resistance to ciprofloxacin during the first year of use, with initial rates being about 10% and recent rates being higher than 80%. On the other hand, methicillin-susceptible S. aureus remained uniformly susceptible to ciprofloxacin (98.4%). We conclude that prior use of ciprofloxacin is an important factor for the selection of ciprofloxacin-resistant strains and that ciprofloxacin has limited usefulness against methicillin-resistant S. aureus.
Insights
Ciprofloxacin resistance in methicillin-resistant Staphylococcus aureus (MRSA) has rapidly increased, with prior ciprofloxacin use being a key factor. This suggests ciprofloxacin has limited effectiveness against MRSA infections.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant treatment challenge.
- Ciprofloxacin is sometimes used as an alternative to vancomycin for MRSA infections.
- Emergence of ciprofloxacin-resistant MRSA strains has been observed.
Purpose of the Study:
- To investigate the prevalence of ciprofloxacin resistance in MRSA isolates.
- To identify factors associated with the development of ciprofloxacin resistance in MRSA.
- To evaluate the clinical utility of ciprofloxacin for MRSA treatment.
Main Methods:
- Disk diffusion and broth microdilution techniques were used to test susceptibility.
- Eighty-three MRSA isolates from various sources were analyzed.
- Patient data, including prior ciprofloxacin use, were reviewed.
Main Results:
- Ciprofloxacin resistance (MIC > 2 µg/mL) was detected in 83% (69/83) of MRSA isolates.
- Prior ciprofloxacin use was reported in 35% (24/69) of resistant cases versus 0% of susceptible cases.
- A significant increase in ciprofloxacin resistance rates was observed within the first year of its use.
Conclusions:
- Prior ciprofloxacin use is a critical factor in selecting for ciprofloxacin-resistant MRSA strains.
- Ciprofloxacin demonstrates limited clinical usefulness for treating MRSA infections due to high resistance rates.
- Continued monitoring of antimicrobial resistance patterns is essential.