Evaluation of the Andromas matrix-assisted laser desorption ionization-time of flight mass spectrometry system for identification of aerobically growing Gram-positive bacilli.

Matrix-associated laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is a rapid and simple microbial identification method. Previous reports using the Biotyper system suggested that this technique requires a preliminary extraction step to identify Gram-positive rods (GPRs), a technical issue that may limit the routine use of this technique to identify pathogenic GPRs in the clinical setting. We tested the accuracy of the MALDI-TOF MS Andromas strategy to identify a set of 659 GPR isolates representing 16 bacterial genera and 72 species by the direct colony method. This bacterial collection included 40 C. diphtheriae, 13 C. pseudotuberculosis, 19 C. ulcerans, and 270 other Corynebacterium isolates, 32 L. monocytogenes and 24 other Listeria isolates, 46 Nocardia, 75 Actinomyces, 18 Actinobaculum, 11 Propionibacterium acnes, 18 Propionibacterium avidum, 30 Lactobacillus, 21 Bacillus, 2 Rhodococcus equi, 2 Erysipelothrix rhusiopathiae, and 38 other GPR isolates, all identified by reference techniques. Totals of 98.5% and 1.2% of non-Listeria GPR isolates were identified to the species or genus level, respectively. Except for L. grayi isolates that were identified to the species level, all other Listeria isolates were identified to the genus level because of highly similar spectra. These data demonstrate that rapid identification of pathogenic GPRs can be obtained without an extraction step by MALDI-TOF mass spectrometry.

Extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE) infections: are carbapenem alternatives achievable in daily practice?

OBJECTIVES: To avoid the use of carbapenems, alternatives such as cephamycin, piperacillin-tazobactam, and others are suggested for the treatment of extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE) infections. The aim of this study was to evaluate the frequency and the feasibility of antimicrobial de-escalation for ESBL-PE-related infections. METHODS: A prospective observational, bi centric cohort study was conducted. All patients with ESBL-PE infections were included. De-escalation was systematically suggested if patients were clinically stable and the isolate was susceptible to possible alternatives. RESULTS: Seventy-nine patients were included: 36 (45.6%) were children, 27 (34.1%) were hospitalized in intensive care units, and 37 (47%) were immunocompromised. Urinary tract infections, pneumonia, and catheter-related bloodstream infections accounted for 45.6%, 19%, and 10%, respectively, of the cohort. Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae were the three most frequent causative organisms isolated. On day 5, 47 (59.2%) of the patients were still receiving carbapenems. Antimicrobial resistance (44.7%), infection relapse (26.9%), and clinical instability (19.2%) were the most important reasons for not prescribing alternatives. E. coli-related infections appeared to be a protective factor against maintaining the carbapenem prescription (odds ratio 0.11, 95% confidence interval 0.041-0.324; p=0.0013). CONCLUSIONS: In clinical practice, less than 50% of patients with ESBL-PE-related infections were de-escalated after empirical treatment with carbapenems.

Risk factors for developing ESBL E. coli: can clinicians predict infection in patients with prior colonization?

BACKGROUND: Extended-spectrum ß-lactamase-producing Escherichia coli (ESBLEC) is an increasing cause of hospital-acquired infection. Risk factors for ESBLEC colonization and infection have been reported, but information is lacking about the risk factors for acquiring ESBLEC infection in patients with prior colonization. AIM: To identify risk factors for development of infection in patients colonized with ESBLEC. METHODS: A retrospective study was performed at Hôpital Necker-Enfants Malades, Paris from 2007 to 2010. A multi-variable model was created to compare a group of patients with nosocomial ESBLEC infection following documented ESBLEC colonization with a control group of patients colonized with ESBLEC (case-control design). FINDINGS: In total, 118 patients were included: 40 (26 adults, 14 children) with colonization and infection and 78 (51 adults, 27 children) with colonization alone. The median time from colonization to infection was 12.5 days [25-75% confidence interval (CI) 5-40]. ESBLEC infections included urinary tract infection (85%), bacteraemia (7.5%) and lower respiratory tract infection (7.5%). On multi-variate analysis, use of ß-lactam/ß-lactamase inhibitor prior to infection [odds ratio (OR) 3.2, 95% CI 1.073-9.864); P = 0.037] and urinary catheterization were reported as risk factors for ESBLEC infection in colonized patients (OR 5.2, 95% CI 1.984-13.569; P = 0.0008). CONCLUSION: Identification of these risk factors will be helpful to identify patients colonized with ESBLEC who will require antibiotics for ESBLEC in the case of nosocomial infection. Limiting the use of specific antibiotics and controlling the duration of urinary catheterization will be helpful for prevention of ESBLEC infection.

[Epidemiology of patients harboring extended-spectrum beta-lactamase-producing enterobacteriaceae (ESBLE), on admission]. / Épidémiologie des patients porteurs d'entérobactéries sécrétrices de bêtalactamase à spectre élargi (EBLSE), à l'admission.

OBJECTIVE: The incidence of extended-spectrum beta-lactamase-producing enterobacteria (ESBLE) has regularly increased over the last few years. However, little is known about epidemiology of ESBLE carriers in France. The objective of this study was to determine the ESBLE carriers or infected patients profile, identified within 48 hours following hospital admission. DESIGN: This retrospective study included all patients admitted in 2006 and 2007 at the Necker-Enfants-Malades (NEM) teaching hospital, carrying or infected with ESBLE isolated within 48 hours following admission. The pediatric and adult populations were compared. RESULTS: There was no significant difference between pediatric and adult populations. Escherichia coli and Klebsiella pneumoniae were the two main species isolated, accounting respectively for 59.6 and 21.1 % of the 114 isolated strains. Among the 114 analyzed files, 24 patients (21 %) were known to be EBLSE carriers, 37 (32 %) were transferred from another hospital, including 16 from another country. Concerning the 54 (47 %) other patients, five (4 %) came from a country with high prevalence, and 44 (39 %) were treated for a chronic illness. Only five patients (4 %) carrying ESBLE did not have any usual risk factor for multidrug resistance (MDR) bacterial carriage. CONCLUSIONS: In our study, 4 % of patients carrying ESBLE admitted had no usual risk factor for MDR bacteria. Targeted screening of previous carriers, patients with chronic illness, transferred patients, or patients coming from country with high prevalence, would help to limit the spread of ESBLE.

Genetic background of Escherichia coli isolates from patients with spontaneous bacterial peritonitis: relationship with host factors and prognosis.

Spontaneous bacterial peritonitis (SBP) is a severe complication in patients with cirrhosis and ascites. It is predominantly caused by Escherichia coli. The phylogenetic group and virulence genotype of E. coli isolates causing SBP were investigated, and the association of these characteristics with host factors and prognosis was examined. Seventy-six episodes of E. coli SBP that occurred over a 9-year period were studied. The phylogenetic group of the isolates and the presence of 36 virulence factor genes were investigated. The influence of bacterial and host factors on in-hospital mortality was assessed by multiple logistic regression. Phylogenetic groups A, B1, B2 and D were found in 26%, 4%, 46% and 24% of the isolates, respectively. Virulence factor genes were more frequent in B2 isolates than in non-B2 isolates (mean virulence score 15.4 vs. 7.3, p <10(-4)). Ciprofloxacin resistance was significantly associated with non-B2 groups and a low virulence score. Host factors independently associated with a shift from B2 to non-B2 isolates were norfloxacin prophylaxis (OR 13.01, p 0.0213) and prothrombin ratio (OR 1.04 for a 10% decrease, p 0.0211). The model for end-stage liver disease (MELD) score (OR 1.83, p 0.0007) and hospital-acquired SBP (OR 4.13, p 0.0247) were independent predictors of in-hospital mortality. In contrast, outcome was not influenced by the phylogenetic group or the virulence profile. These findings indicate that the characteristics of E. coli isolates causing SBP vary with the severity of liver disease and with fluoroquinolone prophylaxis. Host factors are more important than bacterial factors in predicting in-hospital mortality.