Microbiology at first visit of moderate-to-severe diabetic foot infection with antimicrobial activity and a survey of quinolone monotherapy

Samples from 1295 patients with diabetic foot infection were evaluated; 4332 samples were collected with an average of 3.3 samples per patient. Fifty-seven percent of patients had a 2B ulcer and 23% had a 3B ulcer according to Texas University Classification. In 64.2% of samples collected at first visit an etiologic agent was identified. About 40% of the positive samples were polymicrobial. Gram positive bacteria were more frequently isolated (52.6%), Staphylococcus aureus was the most frequently isolated single agent (29.9%) and MRSA was 22% of S. aureus. Enterococcus spp., mainly Enterococcus faecalis, were 9.9%, all vancomycin susceptible except 2 isolates. Streptococci were 4.6%, more than 60% Streptococcus agalactiae. Gram negative rods were 40.6%, with enterobacteria 23.5% and Pseudomonas aeruginosa 10.3%. Anaerobes were only 0.3%, probably due to culture methods applied in our laboratory. Cotrimoxazole, rifampin and doxycycline were still active against S. aureus. ESBL producers, among enterobacteria, were 10%, mainly Escherichia coli and Proteus spp. Only colistin had a rate of susceptibility against P. aeruginosa above 90%. Levofloxacin had the best clinical activity with respect to the other quinolones, but when it failed, selected more resistant strains with respect to moxifloxacin among S. aureus and with respect to ciprofloxacin among P. aeruginosa.