Introduction: Fluoroquinolones are broad spectrum antibiotics commonly used in the treatment of infections.
Objective: Resistance profiles of coccus bacteria to fluoroquinolones were evaluated in isolates of Streptococcus pneumoniae, Staphylococcus aureus, coagulase negative staphylococci and Enterococcus spp. The samples were recovered from Colombian hospitals between 1994 and 2004.
Materials and methods: The minimal inhibitory concentration of ciprofloxacin, moxifloxacin and gatifloxacin was determined in 270 clinical isolates of S. pneumoniae, 348 of S. aureus, 176 of coagulase negative staphylococci and 123 of coagulase-negative enterococci. The minimal inhibitory concentration of levofloxacin was also determined in all isolates of methicillin-resistant S. aureus. An agar diffusion susceptibility test with disks of levofloxacin and ofloxacin was also applied to all isolates of S. pneumoniae.
Results: A total of 269 (99.6%) isolates of S. pneumoniae were susceptible to moxifloxacin and gatifloxacin. For levofloxacin and ofloxacin, resistance in S. pneumoniae was found in 1.5% and 8.9% of isolates, respectively. The ciprofloxacin minimal inhibitory concentration was >4 microg/ml in 15.9% of pneumococcal isolates. The rates of resistance to ciprofloxacin, gatifloxacin and moxifloxacin in the 348 S. aureus isolates were 55.4%, 54.9% and 52.6%, respectively; increasing to 92.3%, 91.3% and 87.5%, respectively in methicillin resistant isolates. Resistance to levofloxacin was found in 91.8% of MRSA isolates. The rates of resistance to ciprofloxacin, gatifloxacin and moxifloxacin in coagulase negative staphylococci and vancomycin-susceptible enterococci were between 25.6% and 31.8%. All vancomycin-resistant enterococci were resistant to all fluroquinolones tested.
Conclusion: The newer fluoroquinolones have maintained effective activity against clinical isolates of S. pneumoniae. The rates of fluoroquinolone resistance in S. aureus were very high, particularly in methicillin resistant isolates (approaching 100%).