Michel Cormier

Molecular and Epidemiological Evidence for Spread of Multiresistant Methicillin-Susceptible Staphylococcus aureus Strains in Hospitals

ABSTRACT The excision of the staphylococcal chromosomal cassette mec (SCCmec) from methicillin-resistant Staphylococcus aureus (MRSA) strains results in methicillin-susceptible S. aureus (MSSA) strains. In order to determine the proportion and diversity of multidrug-resistant MSSA (MR-MSSA) strains derived from MRSA strains, 247 mecA-negative isolates recovered in 60 French hospitals between 2002 and 2004 were characterized. The spa types of all strains were determined, and a subset of the strains (n = 30) was further genotyped by multilocus sequence typing. The IDI-MRSA assay was used to test the isolates for the presence of the SCCmec element, which was detected in 68% of all isolates analyzed. Molecular analysis of the samples suggested that 92% of the MR-MSSA isolates were derived from MRSA clones of diverse genetic backgrounds, of which the clone of sequence type 8 and SCCmec type IVA accounted for most of the samples. High variations in incidence data and differences in the molecular characteristics of the isolates from one hospital to another indicate that the emergence of MR-MSSA resulted from independent SCCmec excisions from epidemic MRSA isolates, as well as the diffusion of methicillin-susceptible strains after the loss of SCCmec. MR-MSSA could constitute a useful model for the study of the respective genetic and environmental factors involved in the dissemination of S. aureus in hospitals.

Effect of higher minimum inhibitory concentrations of quaternary ammonium compounds in clinical E. coli isolates on antibiotic susceptibilities and clinical outcomes

Quaternary ammonium compounds (QACs) are cationic surfactants used as preservatives and environmental disinfectants. Limited data are available regarding the effect of QACs in the clinical setting. We performed a prospective cohort study in 153 patients with Escherichia coli bacteraemia from February to September 2008 at University Hospital in Rennes. The minimum inhibitory concentrations (MICs) of antibiotics and QACs alkyldimethylbenzylammonium chloride (ADBAC) and didecyldimethylammonium chloride (DDAC) were determined by the agar dilution method. The capacity of biofilm production was assayed using the Crystal Violet method, and mutation frequencies by measuring the capacity of strains to generate resistance to rifampicin. Logistic regression analysis showed that one of the significant factors related to low MICs for ADBAC (≤16 mg/L) and DDAC (≤8 mg/L), was cotrimoxazole susceptibility (odds ratio: 3.72; 95% confidence interval: 1.22-11.24; P=0.02 and OR: 3.61; 95% CI: 1.56-7.56; P<0.01, respectively). Antibiotic susceptibility to cotrimoxazole was strongly associated with susceptibility to amoxicillin and nalidixic acid (P<0.01). Community-acquired or healthcare-associated bacteraemia, severity of bacteraemia, and patient outcome were independent of the MICs of ADBAC and DDAC. Our findings demonstrate an epidemiological relationship between higher MIC values of QACs in clinical E. coli isolates and antibiotic resistance.

Evaluation of the Mandibular Third Molar Pericoronitis Flora and Its Susceptibility to Different Antibiotics Prescribed in France

ABSTRACT This work assessed the polymicrobial flora of mandibular third molar pericoronitis. Obligate anaerobes were found in almost all cases (32 of 35). Amoxicillin and pristinamycin were the most effective against the flora, particularly aerobic organisms. Metronidazole alone or combined with spiramycin was the most effective drug against obligate anaerobes.

Influence of job seniority, hand hygiene education, and patient-to-nurse ratio on hand disinfection compliance.

Hand hygiene compliance was evaluated by direct observation in 2006 and 2007. In 2007, data on characteristics such as job seniority, hand hygiene education, and patient-to-nurse ratio during direct observations were collected. A hand hygiene promotional programme was performed between the two evaluations. Univariate and multivariate analysis identified factors associated with improved hand hygiene compliance. Between 2006 and 2007, from 761 hand hygiene opportunities, overall and partial compliance improved from 44.9% to 58% (P<0.001) and from 73.5% to 88.4% (P<0.001), respectively. In 2007, improvements in hand hygiene overall or partial compliance were seen when senior healthcare workers (HCWs) were present in the clinical area under investigation (P=0.04 or P=0.08, respectively). Partial hand hygiene compliance was significantly better in 2007 after a hand hygiene educational programme had been presented (P<0.015). Similar rates of compliance were observed whatever the patient-to-nurse ratio during the observation. Multivariate analysis identified job seniority as an independent predictor of hand hygiene compliance. Our results suggest that hand hygiene compliance is influenced by education on hand hygiene and that a senior HCW could act as a role model for other HCWs. These data should be considered when developing future hygiene interventions.

Direct enumeration of injured Escherichia coli cells harvested onto membrane filters

Abstract Four methods testing either biosynthesis capacity (Direct Viable Counts), respiratory activity (CTC and XTT reduction assays), or membrane integrity (LIVE/DEAD® BacLight™ VIABILITY kit) were performed to enumerate E. coli injured cells previously harvested onto 0.2-μm black membranes. Some of them remained viable but were no longer culturable when exposed to hyperosmotic or oxidative stresses. The damaged cellular functions were dependent on the stress applied, and the results provided by these methods (except the XTT reduction method which is not sensitive enough), gave information on cell behaviour to one stress, and on the different cellular targets of this stress. The osmotic shock in artificial seawater led to moderate plasma membrane damage (0.8 log reduction in counts determined with the LIVE/DEAD® BacLight™ VIABILITY kit after 5 days in seawater), and to similar reductions of respiration and elongation capacities (2.7 log reduction of CTC counts, and 2.6 log reduction of DVC counts, respectively). After a 30-min oxidative stress induced by peracetic acid (8 mg l−1), the plasma membranes remained intact (no reduction of LIVE/DEAD® BacLight™ VIABILITY counts), and respiration was less impaired than elongation capacity (2.1 log reduction of CTC counts and 3.1 log reduction of DVC counts, respectively).

In Vitro Susceptibilities of Capnocytophaga Isolates to β-Lactam Antibiotics and β-Lactamase Inhibitors

ABSTRACT The susceptibilities of 43 pharyngeal isolates ofCapnocytophaga to beta-lactam antibiotics, alone or in combination with beta-lactamase inhibitors, were tested by an agar dilution method. The 34 beta-lactamase-positive strains were highly resistant to beta-lactams, but the intrinsic activities of clavulanate, tazobactam, and sulbactam against Capnocytophaga, even beta-lactamase producers, indicates that these beta-lactamase inhibitors could be used for empirical treatment of neutropenic patients with oral sources of infection.

Genetic Analysis of an Ambler Class A Extended-Spectrum Beta-Lactamase from Capnocytophaga ochracea

ABSTRACT A beta-lactamase gene (cfxA3, 966 bp) was isolated from a beta-lactam-resistant Capnocytophaga ochracea clinical isolate and amplified using primers from the cfxA gene of Bacteroides vulgatus. The MICs of third-generation cephalosporins were much higher than those of the transconjugant Escherichia coli strain. The deduced protein sequence, by comparison with CfxA2 of Prevotella intermedia, had a Y239D substitution and possessed the characteristics of a class A, group 2e beta-lactamase.

Proteins variations in Listeria monocytogenes exposed to high salinities.

Listeria monocytogenes Scott A grown in the minimal chemically defined medium M6LT was challenged to a concentration of either 35 or 65 g l(-1) of NaCl for 1 h in the presence of a [35S]cysteine-[35S]methionine labelling mix. The protein patterns were analysed by 2D-electrophoresis in the two conditions and isoosmotic condition (5 g l(-1) of NaCl in M6LT). A great number of proteins which were synthesized under isoosmotic conditions were either completely repressed or expressed at a reduced level, at 65 g l(-1) and to a lesser extent at 35 g l(-1) of NaCl. At 35 g l(-1) of NaCl, six proteins were up-regulated, five proteins showed no change in expression level and five were repressed. Among the proteins up-regulated at 35 g l(-1) of NaCl, a single one (18.7 kDa, pI 5.05) was up-regulated at 65 g l(-1) too. We observed 21 proteins which were repressed at 65 g l(-1) of NaCl, among which 11 completely disappeared. Some of the up-regulated proteins have characteristics of molecular weight and isoelectric point close to those of stress proteins reported elsewhere: the protein induced both at 35 and 65 g l(-1) might correspond to a previously proposed universal stress protein of Listeria. Some proteins which were repressed at 65 g l(-1) have molecular weights close to those of virulence proteins.

Tenosynovitis of the Wrist Due to Resistant Mycobacterium tuberculosis in a Heart Transplant Patient

ABSTRACT Tubercular tenosynovitis is now rare, which can delay diagnosis of this disease. We report a case of tenosynovitis of the wrist in a heart transplant patient caused by an isoniazid- and streptomycin-resistant Mycobacterium tuberculosis strain. Despite immunosuppression therapy, which can lead to a smoldering evolution, molecular biology analysis of biopsies allowed a rapid diagnosis.

An improved filter method for direct viable count of Salmonella in seawater

The method of Kogure et al. (1984), which employed measurement of enlarged cells in water samples enriched with low concentrations of nutrient, combined with detection by fluorescent antibodies was used to obtain direct viable counts of Salmonella typhimurium. Technical conditions of the method have been optimized for S. typhimurium, i.e., incubation time of 6 h at 37°C and addition of nalidixic acid at a concentration of 12 mg/l. Natural seawater samples with a salinity of 35% wwere inoculated with S. typhimurium at concentrations of 104−105 cells/ml and kept at 4°C up to 60 h. When yeast extract and nalidixic acid were added to the seeded samples, elongated cells could not be detected. Minimal inhibitory concentrations of nalidixic acid were higher for S. typhimurium at full strength seawater salinity (250 mg/l) compared with fresh water (15.6 mg/l). This effect on the direct viable count was eliminated by filtering samples, using 0.2-μm pore size Nuclepore black filters and modifying the procedure. The method developed in this study permitted observation of elongated (viable) cells of S. typhimurium in the full strength seawater samples (17.3–28.3% elongated cells). The method is suitable for conditions in which the salinity of the samples poses a problem in obtaining direct viable counts.