Multidrug-resistant, extensively drug-resistant and pandrug-resistant bacteria: an international expert proposal for interim standard definitions for acquired resistance

AbstractMany different definitions for multidrug-resistant (MDR), extensively drug-resistant (XDR) and pandrug-resistant (PDR) bacteria are being used in the medical literature to characterize the different patterns of resistance found in healthcare-associated, antimicrobial-resistant bacteria. A group of international experts came together through a joint initiative by the European Centre for Disease Prevention and Control (ECDC) and the Centers for Disease Control and Prevention (CDC), to create a standardized international terminology with which to describe acquired resistance profiles in Staphylococcus aureus, Enterococcus spp., Enterobacteriaceae (other than Salmonella and Shigella), Pseudomonas aeruginosa and Acinetobacter spp., all bacteria often responsible for healthcare-associated infections and prone to multidrug resistance. Epidemiologically significant antimicrobial categories were constructed for each bacterium. Lists of antimicrobial categories proposed for antimicrobial susceptibility testing were created using documents and breakpoints from the Clinical Laboratory Standards Institute (CLSI), the European Committee on Antimicrobial Susceptibility Testing (EUCAST) and the United States Food and Drug Administration (FDA). MDR was defined as acquired non-susceptibility to at least one agent in three or more antimicrobial categories, XDR was defined as non-susceptibility to at least one agent in all but two or fewer antimicrobial categories (i.e. bacterial isolates remain susceptible to only one or two categories) and PDR was defined as non-susceptibility to all agents in all antimicrobial categories. To ensure correct application of these definitions, bacterial isolates should be tested against all or nearly all of the antimicrobial agents within the antimicrobial categories and selective reporting and suppression of results should be avoided

Risk Factors for Acquisition of Fluoroquinolone or Aminoglycoside Resistance in Addition to Carbapenem Resistance in Pseudomonas aeruginosa

Background: Carbapenems, fluoroquinolones (FQs), and aminoglycosides (AGs) are key drugs for treating Pseudomonas aeruginosa infections, and accumulation of drug resistances make antibiotic therapy difficult.Methods: We evaluated 169 patients with imipenem (IPM)-resistant P. aeruginosa and compared patient background and microbiological characteristics between groups with or without FQ resistance. Similar analyses were performed for AG. Results: Of the 169 IPM-resistant strains, 39.1% showed resistance to FQs and 7.1% to AGs. The frequency of exposure to FQs within 90 days previously was higher in the group with FQ resistance (45.5%) than in the group without FQ resistance (13.6%). Similarly, 33.3% of patients in the group with AG resistance had been previously administered AGs, higher than the 7.6% of patients without AG resistance. Frequencies of metallo-β-lactamase (MBL) production were higher in the group with FQ or AG resistance (16.7% or 33.3%) than in the group without FQ or AG resistance (2.9% or 6.4%). Multivariate analyses showed exposures to FQs or AGs were related to the respective resistances. MBL production was a common factor for resistance to FQs or AGs, in addition to IPM-resistant P. aeruginosa. Conclusion: As well as promoting appropriate use of antibiotics, MBL production should be detected as a target of intervention for infection control

Rifampicin-impregnated central venous catheters: A meta-analysis of randomized controlled trials

Background: The use of antimicrobial-impregnated central venous catheters (CVCs) for the prevention of CVC microbial colonization and catheter-related bloodstream infection (CRBSI) remains controversial. Methods: We performed a meta-analysis of randomized controlled trials (RCTs) evaluating CRBSI and colonization of CVCs impregnated with rifampicin-based antimicrobial combinations. Our main analysis compared the occurrence of CRBSI with rifampicin/minocycline-impregnated CVCs with that of non-rifampicin-impregnated CVCs. The PubMed and Cochrane Central Register of Controlled Trials databases were searched (until October 2006). Results: Eight RCTs were included in the analysis. The main analysis (seven RCTs) demonstrated that rifampicin/minocycline-impregnated CVCs were associated with fewer CRBSIs compared with catheters not impregnated with rifampicin/minocycline (OR 0.23, 95% CI 0.14-0.40). The same was true regarding colonization (OR 0.46, 95% CI.31-0.69). Further analysis, comparing rifampicin-based CVCs with non-rifampicin-impregnated CVCs, demonstrated superiority of rifampicin-based CVCs in reducing colonization (OR 0.38, 95% CI 0.24-0.62) and CRBSI (OR 0.24, 95% CI 0.14-0.40). Similar results, suggesting superiority of rifampicin/minocycline-impregnated CVCs, were noted in a subgroup analysis of colonization and CRBSIs in which rifampicin/minocycline-impregnated CVCs were compared with simple, non-tunnelled, non-antimicrobially impregnated CVCs, a subgroup analysis that was performed by excluding low quality RCTs, and a subgroup analysis for colonization comprising studies in which the sonication technique was used. No serious adverse events and no difference in mortality between the two treatment groups were reported. No clear conclusions can be made regarding the impact of the use of rifampicin/ minocycline-impregnated CVCs on the development of antimicrobial resistance based on the available data. Conclusions: The available evidence suggests that rifampicin/ minocycline-impregnated CVCs are safe and effective in reducing the rate of catheter colonization and CRBSI. Further research should focus on the possible development of resistance and on pharmacoeconomic issues related to the use of rifampicin/minocycline-impregnated CVCs. © The Author 2007. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved

Community-acquired Stenotrophomonas maltophilia infections: A systematic review

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. © 2009 Springer-Verlag