Antimicrobial susceptibility survey of pathogens isolated from selected patients in Northern Italy

The Clinical Microbiology Laboratory of the University of Genoa participated, during the year 2003, in an international antimicrobial surveillance program.The collection of isolates was done according to the site of infection and/or type of patient. Four hundred twenty (420) clinical isolates were analyzed during this year and the frequencies of the different pathogens were investigated. A reference centre carried out susceptibility tests. Oxacillin-resistant Staphylococcus aureus represented 47.6% of all S. aureus isolates from blood stream infections and 33.3% of all S. aureus isolated from skin and soft tissue infections in hospitalised patients.These strains showed resistance to most of the antimicrobial agents evaluated, except vancomycin, teicoplanin, quinupristin/dalfopristin and linezolid which registered 100% of susceptibility. Some isolates from blood stream infections such as E. coli demonstrated resistance to ciprofloxacin (23.3%), levofloxacin (20%), and gatifloxacin (16.6%), and Klebsiella pneumoniae was resistant (18%) to all fluoroquinolones tested. Pseudomonas aeruginosa manifested resistance to ciprofloxacin (16.6%), while 27.7% of these strains were resistant both to levofloxacin and gatifloxacin. All the Enterobacter cloacae isolated from blood were susceptible to ciprofloxacin, levofloxacin and gatifloxacin. Haemophilus influenzae and Moraxella catarrhalis collected from community-acquired respiratory tract infections were all inhibited by ciprofloxacin, levofloxacin and gatifloxacin. E. coli isolated from urinary tract infections in hospitalised patients were resistant to ciprofloxacin, levofloxacin and gatifloxacin (2.7%). All Salmonella spp. collected from samples of patients affected by infections of the gastro-intestinal tract were susceptible to all fluoroquinolones. Penicillin resistance in Streptococcus pneumoniae was found in 21.4% of isolates from patients with respiratory tract infections. Fluoroquinolone resistance was very rare among pneumococci except for ciprofloxacin. High rates of resistance to this drug (100%); resistance to levofloxacin and gatifloxacin was detected only in 3.6% of cases while resistance to moxifloxacina was detected in 1.8% of cases. Macrolide resistance rates were around 35% to 41%, tetracycline and trimethoprim/sulfamethoxazole resistance rates were relatively elevated (37.5% and 32.1% resistance respectively).