Utility of anaerobic bottles for the diagnosis of bloodstream infections.

BACKGROUND: Obligate anaerobes usually account for less than 10% of bacteria recovered from blood cultures (BC). The relevance of routine use of the anaerobic bottle is under debate. The aim of this study was to evaluate the utility of anaerobic bottles for the diagnosis of bloodstream infections (BSI). METHODS: We conducted a 6-month, retrospective, monocentric study in a tertiary hospital. All positive BC were grouped into a single episode of bacteremia when drawn within 7 consecutive days. Bacteremia were classified into contaminants and BSI. Charts of patients with BSI due to obligate anaerobes were studied. RESULTS: A total of 19,739 blood cultures were collected, 2341 of which (11.9%) were positive. Anaerobic bottles were positive in 1528 (65.3%) of all positive BC but were positive alone (aerobic bottles negative) in 369 (15.8%). Overall 1081 episodes of bacteremia were identified, of which 209 (19.3%) had positive anaerobic bottles alone. The majority 126/209 (60.3%) were contaminants and 83 (39.7%) were BSI. BSI due to facultative anaerobes, obligate aerobes and obligate anaerobes were identified in 67 (80.7%), 3 (3.6%) and 13 (15.7%) of these 83 episodes, respectively. BSI due to obligate anaerobic bacteria were reported in 9 patients with gastro-intestinal disease, in 3 with febrile neutropenia and in 1 burned patient. CONCLUSIONS: Anaerobic bottles contributed to the diagnosis of a significant number of episodes of bacteremia. Isolated bacteria were mostly contaminants and non-obligate anaerobic pathogens. Rare BSI due to obligate anaerobes were reported mainly in patients with gastro-intestinal disorders and during febrile neutropenia.

Incidence, risk factors, and outcome of multidrug-resistant Acinetobacter baumannii acquisition during an outbreak in a burns unit.

BACKGROUND: Multidrug-resistant Acinetobacter baumannii (MR-AB) can cause outbreaks in a burns unit. AIM: To study the incidence, risk factors and outcome of MR-AB colonization during an outbreak. METHODS: A prospective study was conducted from April to November 2014 in a burns unit in Paris. Weekly surveillance cultures of patients and their environment were performed. MR-AB acquisition, discharge, or death without MR-AB colonization were considered as competing events. To identify risk factors for colonization, baseline characteristics and time-dependent variables were investigated in univariate and multivariate analyses using Cox models. MR-AB strains were genotypically compared using multi-locus sequence typing. FINDINGS: Eighty-six patients were admitted in the burns unit during the study period. Among 77 patients without MR-AB colonization at admission, 25 (32%) acquired MR-AB with a cumulative incidence of 30% at 28 days (95% CI: 20-40). Median time to MR-AB acquisition was 13 days (range: 5-34). In multivariate analysis, risk factors for MR-AB acquisition were ≥2 skin graft procedures performed [hazard ratio (HR): 2.97; 95% confidence interval (CI): 1.10-8.00; P = 0.032] and antibiotic therapy during hospitalization (HR: 4.42; 95% CI: 1.19-16.4; P = 0.026). A major sequence type of MR-AB (ST2) was found in 94% and 92% of patients and environmental strains, respectively, with all strains harbouring the blaOXA-23 gene. MR-AB colonization increased length of hospitalization (HR: 0.32; 95% CI: 0.17-0.58; P = 0.0002) by a median of 12 days. CONCLUSION: A high incidence of MR-AB acquisition was seen during this outbreak with most strains from patients and their environment belonging to single sequence type. MR-AB colonization was associated with more skin graft procedures, antibiotic use, and prolonged hospitalization.

Usefulness of daily surveillance blood cultures in allogeneic hematopoietic stem cell transplant recipients on steroids: a 1-year prospective study.

BACKGROUND: Bloodstream infections (BSI) are frequent and potentially severe complications in allogeneic hematopoietic stem cell transplant (AHSCT) recipients. In patients on steroids, surveillance blood cultures (SBCs) are routinely performed to detect asymptomatic BSI but their usefulness remains controversial. METHODS: We performed a 1-year, observational, prospective, single-center study to assess the utility of daily SBCs in AHSCT recipients on steroids and a case-control study to identify risk factors associated with positive SBCs. All blood cultures (BCs) obtained from adults hospitalized in the HSCT unit were prospectively studied throughout 1 year. Characteristics, treatments, and outcome of patients were retrieved from medical charts. RESULTS: A total of 3594 BCs were obtained in 177 patients, including 1450 SBCs in 82 AHSCT recipients on steroids. In 33 patients, 103 SBCs (7%) were positive. Low-virulence bacteria were identified in 74% of episodes. When analyzing first episode of positive SBCs (28 patients), 6 (21%) true BSI were identified. CONCLUSIONS: Patients with positive SBCs were receiving antibiotic treatment less frequently at the time of SBCs (P < 0.001) and had more frequently BCs obtained through central venous access (P < 0.04) when compared to patients with negative SBCs. Daily SBCs in AHSCT recipients on steroids only rarely identify BSI and clear benefit for patients could not be demonstrated.

Prevalence, risk factors, and impact on clinical outcome of extended-spectrum beta-lactamase-producing Escherichia coli bacteraemia: a five-year study.

BACKGROUND: The impact of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (ESBL-EC) bacteraemia on outcome remains controversial. METHODS: A retrospective analysis of the prevalence, risk factors, clinical features, and outcomes of all ESBL-EC bacteraemia in one French hospital over a 5-year period was performed. A case-control study was undertaken: cases had at least one ESBL-EC bacteraemia and controls a positive non-ESBL-EC bacteraemia. RESULTS: The prevalence of ESBL-EC bacteraemia increased from 5.2% of all positive E. coli blood cultures in 2005 to 13.5% in 2009 (p<0.003). CTX-M represented 70% of ESBL-EC bacteraemia strains, and strains were not clonally related. On adjusted analysis, the only significant risk factor for ESBL-EC bacteraemia was a previous ESBL-EC colonization (odds ratio 11.3, 95% confidence interval 1.2-107; p=0.003). Initial antimicrobial therapy was less frequently adequate in the ESBL-EC group (48% vs. 85%; p=0.003). The presence of ESBL-EC bacteraemia was not associated with a longer hospital stay (p=0.088). Day 30 mortality was high, but not significantly different in the two groups (30% vs. 27%; p=0. 82). CONCLUSION: The prevalence of ESBL-EC bacteraemia has been increasing dramatically. Previous colonization with ESBL-EC was a strong risk factor for ESBL-EC bacteraemia. More inadequate initial antimicrobial therapy was noted in the ESBL-EC group, but mortality and length of hospital stay were not significantly different from those of patients with non-ESBL-EC bacteraemia.

Outbreak in a haematology unit involving an unusual strain of glycopeptide-resistant Enterococcus faecium carrying both vanA and vanB genes.

OBJECTIVES: To report an outbreak due to an unusual strain of Enterococcus faecium containing both the vanA and vanB genes, in France, where the rate of glycopeptide-resistant enterococci (GRE) is below 1%. METHODS: Cases were patients infected or colonized with GRE on the haematology ward. Contact patients were screened by real-time PCR performed on rectal swabs. Clinical features were compared for GRE-positive and GRE-negative patients. GRE isolates were characterized by phenotypic and molecular methods including PFGE. Conjugation experiments were performed to identify van genetic support. RESULTS: After the index patient presented a bacteraemia with vanA/vanB E. faecium, 56 contact patients were screened, 7 of whom were found to be GRE positive: 6 additional cases with vanA/vanB E. faecium and 1 with GRE carrying vanA only. PFGE confirmed the clonal relationship of the seven vanA/vanB E. faecium strains, whereas the vanA isolate was distinct. Only the vanA gene could be transferred to enterococcal recipients by conjugation, and it was probably localized on a mobile genetic element. All isolates were resistant to vancomycin (MIC > 256 mg/L) and teicoplanin (MIC = 24-32 mg/L), but were susceptible to tigecycline (MIC = 0.09 mg/L), linezolid (MIC = 0.75 mg/L) and daptomycin (MIC = 1-2 mg/L). Significant differences (P < 0.001) between carriers and non-carriers of GRE were observed for the median duration of hospitalization (57 days versus 16.5 days) and of neutropenia (40 days versus 6 days), the median number of antibiotics used (5 versus 1.5) and the duration of glycopeptide treatment (14.5 days versus 0 days). CONCLUSIONS: vanA/vanB E. faecium strains, although rare, can emerge in the absence of previous outbreaks of vanA-GRE or vanB-GRE.

In vivo selection of a complex mutant TEM (CMT) from an inhibitor-resistant TEM (IRT) during ceftazidime therapy.

OBJECTIVES: A relapse from Escherichia coli bloodstream infection was observed in a patient with acute leukaemia treated with ceftazidime for 7 days for febrile neutropenia. Whereas the original E. coli isolate was resistant to ß-lactam/ß-lactamase inhibitor combinations (EC1), the relapse E. coli isolate showed a similar phenotype but with resistance extended to ceftazidime (EC2). We investigated the molecular mechanisms of ß-lactam resistance and sought if EC2 could have been selected in vivo from EC1. METHODS: EC1 and EC2 isolates were compared for antibiotic MICs, plasmid content, genotyping, ß-lactamase genes and their environment. Both isolates were conjugated with E. coli JW4111ΔampC and MICs determined for transconjugants. In addition, ceftazidime-resistant mutants were selected in vitro from EC1. RESULTS: EC1 and EC2 showed identical patterns for genotyping and resistance plasmids. PCR sequencing of blaTEM in EC1 showed the mutations M69L and N276D corresponding to TEM-35, also called inhibitor-resistant TEM (IRT)-4. In EC2, the TEM allele showed an additional mutation, R164S, known to confer resistance to ceftazidime. The combination of these three mutations was previously reported in TEM-158, described as the complex mutant TEM (CMT)-9, associated with resistance to ß-lactamase inhibitors and third-generation cephalosporins. In vitro selection of ceftazidime-resistant mutants from EC1 yielded six different CMT alleles, including TEM-158 containing the R164S mutation. CONCLUSIONS: This first known report of in vivo selection of CMT from IRT, reproduced in vitro, shows how the evolution of ß-lactamase enzymes is easily driven by antibiotic pressure, even during a short antibiotic therapy.

Invasive pneumococcal disease in HIV-infected adults in France from 2000 to 2011: antimicrobial susceptibility and implication of serotypes for vaccination.

PURPOSE: Invasive pneumococcal diseases (IPD) remain frequent and severe events in human immunodeficiency virus (HIV)-infected subjects despite the use of antiretroviral therapy and the availability of vaccines. Our aim was to assess the antibiotic susceptibilities and serotypes of strains responsible for IPD in HIV-infected patients. METHODS: We retrospectively analyzed all Streptococcus pneumoniae strains isolated from normally sterile sites between 2000 and 2011 in HIV-infected patients from a single reference center in Paris. The minimum inhibitory concentrations were determined by the E-test, and serotyping was performed by the antiserum agglutination method. RESULTS: Among our study group, 41 HIV-infected adults presented 43 IPD during the study period. Of these 41 patients, 78 % were men, and the median age was 43 (range 23-62) years. the median CD4 cell count was 184/mm(3) (6-1,090/mm(3)), 51 % were receiving antiretroviral therapy, and 24 % had plasma HIV-RNA levels of <400 copies/mL. Only two patients had received the pneumococcal polysaccharide 23-valent vaccine (PPV23). Isolates were susceptible to penicillin G, amoxicillin, and cotrimoxazole in 44, 70, and 59 % of cases, respectively, and were significantly less susceptible to these antibiotics than isolates in the French general population during the same period. Among the 27 strains serotyped, 18 different serotypes were observed, of which 19A, 14, 7F, and 6A were the most frequent. Serotype distribution was similar to that in the French general population. The PPV23 vaccine and the 13-valent conjugate vaccine (PCV13) would have theoretically covered 78 and 70 % of cases, respectively. CONCLUSIONS: In our HIV-infected patient cohort, S. pneumoniae isolates demonstrated higher levels of resistance to beta-lactamines and cotrimoxazole than in the French general population. HIV-infected patients should benefit from the herd protection effect expected from the large-scale vaccination of children by PCV13.

The epidemiology of invasive Streptococcus pneumoniae infections in onco-haematology and haematopoietic stem cell transplant patients in France. Are the serotypes covered by the available anti-pneumococcal vaccines?

The pneumococcal antigens contained in the polysaccharide (PPV23) and conjugate (7-valent, PCV7; 13-valent, PCV13) vaccines have been chosen since they represent the serotypes that more frequently cause invasive pneumococcal disease. Whether these vaccines cover the serotypes most frequently isolated in haematology patients is unclear. The serotype distribution among Streptococcus pneumoniae in 25 consecutive pneumococcal infections that occurred over the last 3 years in two French haematology departments was investigated. The pneumococcal vaccines PCV7, PCV13 and PPV23 were found to cover 76, 84 and 92%, respectively, of the serotypes found.

[Postoperative nocardiosis caused by Nocardia otitidiscaviarum: pitfalls and delayed diagnosis]. / Nocardiose postopératoire à Nocardia otitidiscaviarum: pièges et retard de diagnostic.

Nocardiosis is an uncommon infection, which is exceptionally present as a postoperative event. A case of postoperative pulmonary and cerebro-meningeal infection caused by Nocardia otitidiscaviarum after a leg amputation in a diabetic patient is reported. Diagnosis has been delayed and the clinical, radiological and microbiological causes of this delay are assessed from a quality of care management point of view. Recommendations are proposed regarding physicians' role and optimized microbiological procedures for recognition of slowly growing nocardial strains.

Evaluation of the automated phoenix system for potential routine use in the clinical microbiology laboratory.

A comparative study was designed to evaluate the identification (ID) and antimicrobial susceptibility testing (AST) performances of the BD Phoenix Automated Microbiology System (Becton Dickinson Diagnostic Systems [BD], Pont de Claix, France). A total of 305 single clinical isolates were collected, and comparisons were made with routine manual methods in use in our microbiology laboratories. The percentages of correct IDs were 93.3, 89.4, 91.8, and 85.7% for enterobacteria, nonfermenting gram-negative bacilli, staphylococci, and streptococci-enterococci, respectively. The median ID time was 3 h, and the median time for AST was 10 h 30 min. AST results showed variable percentages of errors for the different antibiotics. None of the enterobacteria and 0.3% of Pseudomonas aeruginosa isolates showed a very major error (VME). Only one strain of Staphylococcus aureus showed a VME with oxacillin. We demonstrate here the efficiency of the Phoenix system, which can be used for the majority of strains encountered in a university-based laboratory, for ID and AST.