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The treatment of multidrug-resistant (MDR), extensively drug-resistant or pandrugresistant non-fermenting Gram-negative bacterial infections constitutes a challenge in an era of few new antibiotic choices. This mandates the re-evaluation of already existing antibiotics such as fosfomycin.

The advancing antimicrobial drug resistance among Enterobacteriaceae renders the evaluation of potential novel therapeutic options necessary. We sought to evaluate the in vitro antimicrobial activity of fosfomycin against multidrug-resistant (MDR) Enterobacteriaceae isolates. Antimicrobial susceptibility to fosfomycin and 12 additional antibiotics of MDR Enterobacteriaceae isolates collected between November 2007 and April 2009 at the University Hospital of Heraklion, Crete, Greece, was examined using the Etest method. A total of 152 MDR Enterobacteriaceae isolates were studied, including Klebsiella pneumoniae (76.3%), Escherichia coli (17.1%), Proteus mirabilis (4.6%) and other species (2.0%).Antimicrobial susceptibility rates were highest for fosfomycin (92.8%), tigecycline (92.1%) and colistin (73.0%) followed by imipenem (35.5%), tetracycline (20.4%), gentamicin (19.7%), trimethoprim/sulfamethoxazole (12.5%) and ciprofloxacin (10.5%). Of the 152 isolates, 85 (55.9%) were extensively drug-resistant (XDR), of which 78 (91.8%) remained susceptible to fosfomycin. Susceptibility to fosfomycin of the 79 carbapenemase-producing, 34 extended-spectrum -lactamase-producing and 24 metallo--lactamase-producing isolates was 94.9%, 94.1% and 83.3%, respectively. In conclusion, in this study fosfomycin exhibited good in vitro antimicrobial activity against MDR and XDR Enterobacteriaceae. We suggest further evaluation of the potential clinical utility of fosfomycin against infections caused by these pathogens.

A considerable mortality rate (up to 37.5%) can be attributed to S. maltophilia infection. Thus, clinicians should not underestimate the clinical significance of S. maltophilia infections.

Stenotrophomonas maltophilia is a pathogen that causes infections mainly in immunocompromised patients. However, community-acquired S. maltophilia infections have been occasionally reported. The objective of this paper was to collect and evaluate the available published data referring to community-acquired S. maltophilia infections. We searched PubMed, the Cochrane Library, and Scopus for articles providing data for patients with community-acquired S. maltophilia infections. Eight case series and 23 case reports (involving 77 and 26 patients with community-acquired S. maltophilia infections, respectively) were regarded as eligible for inclusion in our review. Regarding the 77 patients with community-acquired S. maltophilia infections included in the identified case series, 45 had bacteremia, six ocular infections, five respiratory tract infections, four wound/soft tissue infections, two urinary tract infections, one conjunctivitis, one otitis, and one cellulitis; data were not reported for the remaining 12 patients. Comorbidity (such as malignancy, HIV infection, prior hospitalization) was common. Data included in the eight case series regarding the outcome of infection were limited. From the 26 patients with community-acquired S. maltophilia infections reported in the case reports, 22 were cured from the infection, whereas 4 of 26 patients died; one death was attributed to septic shock due to S. maltophilia. Several publications report patients with community-acquired S. maltophilia infections; the majority of them refer to patients with some kind of comorbidity. Physicians should be aware that S. maltophilia infections are not restricted to hospitalized patients.

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In a region with relatively high levels of antimicrobial resistance, fosfomycin seems to exhibit good levels of in vitro activity against Gram-negative nonurinary isolates. These data justify further evaluation of its potential clinical effectiveness.