Levofloxacin and Ciprofloxacin In Vitro Activities against 4,003 Clinical Bacterial Isolates Collected in 24 Italian Laboratories

Abstract

Levofloxacin showed comparable in vitro susceptibility to ciprofloxacin among Enterobacteriaceae, Pseudomonas aeruginosa, enterococci, and Staphylococcus aureus, while greater susceptibility was observed in Stenotrophomonas maltophilia and Staphylococcus epidermidis, mainly when oxacillin resistant. The susceptibility of Streptococcus pneumoniae to levofloxacin reached 99%.The recent introduction of levofloxacin, a new fluoroquinolone (FQ), into the Italian clinical scenario led to the need to locally confirm its in vitro activity. Nowadays, only qualitative studies on selected bacterial species have been reported with levofloxacin in Italy (1,3,4,5,6,10,13) but larger studies on clinical isolates are missing. We report here the major findings of a survey carried out on the bacterial species most frequently encountered in the routine work of 24 Italian laboratories distributed Italywide (see Acknowledgments).Each center was requested to collect 194 consecutive, no-copy clinical isolates belonging to a predefined list of bacterial species without any limitation on the ward and/or sample of isolation. All the isolates had to be identified according to the laboratory method used to obtain them. Participants were asked to limit the number of collected Escherichia coli, Staphylococcus aureus, and Staphylococcus epidermidis strains to 30 each per center. The MICs of levofloxacin and ciprofloxacin were determined locally by the Etest (AbBiodisk) method according to the manufacturer's instructions. All the assays were performed on MuellerHinton agar except for Streptococcus pneumoniae and Moraxella catarrhalis, which were tested by using MuellerHinton agar plus 5% sheep blood, and Haemophilus influenzae, which was tested by using Haemophilus test medium (all media were from the same batch). Susceptibility breakpoints were Յ2 g/ml for levofloxacin and Յ1 g/ml for ciprofloxacin according to NCCLS (11). To contain intralaboratory variability, quality controls with E. coli strain ATCC 25922, S. pneumoniae strain ATCC 49619, and H. influenzae strain ATCC 49247 were requested of each center before, during, and after the study's conclusion. The Etest method was selected because of its reliability in testing FQs (9), its ease of use, and its definition of the MIC. Between January and November 2000, case report forms for a total of 4,003 clinical isolates were collected. The quality control results confirmed that the Etest assays were carried out properly during the study, and any center results had to be discharged. As reported by others (9), a slight overestimation (1.6%) of the ciprofloxacin MIC for E. coli ATCC 25922 occurred, but the increase never determined a change in the category. Detailed figures on the isolation wards, samples, and the samples' FQ susceptibilities will be published elsewhere. The isolates and their susceptibilities to levofloxacin and ciprofloxacin are illustrated in Table 1. The Enterobacteriaceae were unhomogeneously susceptible to the study drugs, with a percentage of susceptible strains ranging fr...

In vitro Activity of Levofloxacin against Recent Gram-Negative Nosocomial Pathogens

“…Third-generation cephalosporins and aztreonam showed higher susceptibility rates with respect to coamoxiclav, but still lower susceptibility compared to meropenem and fluoroquinolones. Our results confirm the data on levofloxacin reported in the literature, indicating that its activity against Gramnegative rods, including the multiresistant nosocomial strains, is maintained and at least equivalent or superior to that of ciprofloxacin [8][9][10]. In particular, the levofloxacin activity against P. aeruginosa was comparable to that of ciprofloxacin, whereas the activity of levofloxacin against S. maltophilia, an emerging multiresistant pathogen, was better compared to the other drugs tested.…”

Can Levofloxacin Be a Useful Alternative to Trimethoprim-Sulfamethoxazole for Treating Stenotrophomonas maltophilia Bacteremia?

“…In our study, adverse events occurred more frequently in patients receiving TMP-SMX than in those receiving levofloxacin. The new fluoroquinolones, such as moxifloxacin and levofloxacin, show superior in vitro activity against S. maltophilia than earlier quinolones, either alone or in combination (10)(11)(12). However, in the use of levofloxacin for treating S. maltophilia infection, induction of resistance is a matter of concern.…”

Differential Effects of Levofloxacin and Ciprofloxacin on the Risk for Isolation of Quinolone-Resistant Pseudomonas aeruginosa

“…Levofloxacin, a newer member of the quinolone class, also has activity against P. aeruginosa, albeit usually to a lesser degree, as evidenced by higher MICs than those of ciprofloxacin (5,16,22,24,27). With the widespread use of quinolones both in the hospital and in the community setting, resistance to ciprofloxacin and levofloxacin among P. aeruginosa isolates has emerged and continues to rapidly escalate (3, 4).…”