Psychrobacter arenosus bacteremia after blood transfusion, France.

We report a case of transfusion-associated bacteremia caused by Psychrobacter arenosus. This psychrotolerant bacterium was previously isolated in 2004 from coastal sea ice and sediments in the Sea of Japan, but not from humans. P. arenosus should be considered a psychrotolerant bacterial species that can cause transfusion-transmitted bacterial infections.

PatA and PatB form a functional heterodimeric ABC multidrug efflux transporter responsible for the resistance of Streptococcus pneumoniae to fluoroquinolones.

All bacterial multidrug ABC transporters have been shown to work as either homodimers or heterodimers. Two possibly linked genes, patA and patB from Streptococcus pneumococcus, that encode half-ABC transporters have been shown previously to be involved in fluoroquinolone resistance. We showed that the ΔpatA, ΔpatB, or ΔpatA/ΔpatB mutant strains were more sensitive to unstructurally related compounds, i.e., ethidium bromide or fluoroquinolones, than the wild-type R6 strain. Inside-out vesicles prepared from Escherichia coli expressing PatA and/or PatB transported Hoechst 33342, a classical substrate of multidrug transporters, only when both PatA and PatB were coexpressed. This transport was inhibited either by orthovanadate or by reserpine, and mutation of the conserved Walker A lysine residue of either PatA or PatB fully abrogated Hoechst 33342 transport. PatA, PatB, and the PatA/PatB heterodimer were purified from detergent-solubilized E. coli membrane preparations. Protein dimers were identified in all cases, albeit in different proportions. In contrast to the PatA/PatB heterodimers, homodimers of PatA or PatB failed to show a vanadate-sensitive ATPase activity. Thus, PatA and PatB need to interact together to make a functional drug efflux transporter, and they work only as heterodimers.

Gardnerella vaginalis as a rare cause of prosthetic joint infection.

We describe a septic loosening of a hip prosthesis in a 71-year-old woman caused by Gardnerella vaginalis. Infection was confirmed by culture and molecular identification of this bacterium. The patient was treated by a one-step exchange of prosthesis and antibiotic therapy combining trimethoprim-sulfamethoxazole and rifampin, with favorable evolution.

Three cases of post-cataract surgery endophthalmitis due to Rhizobium (Agrobacterium) radiobacter.

We present three unrelated post-cataract surgery endophthalmitis cases caused by Rhizobium radiobacter, hospitalized in three different hospitals. Early diagnosis was obtained in two cases by bacterial DNA detection in vitreous samples. All patients recovered from infection, but pars plana vitrectomy was needed in two patients due to rapid clinical deterioration.

Two cases of type A infant botulism in Grenoble, France: no honey for infants.

We report two severe cases of infant botulism diagnosed at Grenoble University Hospital, France, respectively in 2006 and 2009. Both cases were characterized by a delay in diagnosis, severe neurological manifestations and extended period of hospitalization in intensive care unit, but a complete recovery. Infant botulism is a rare but life-threatening disease. It primarily affects infants, and the main risk factor is honey ingestion. Diagnosis should be systematically evoked by pediatricians in infants suffering from constipation, fatigue, muscle weakness, difficult feeding and altered cry, but before the onset of generalized flaccid paralysis, so as to administer specific treatment (BabyBIG®, a human derived botulinum antitoxin) at an early stage of the disease when it is most effective. In conclusion, parents should be aware of the role of honey as a source of spores of Clostridium botulinum and therefore infant botulism in the first year of life.

Epidemiology and antimicrobial resistance of Streptococcus pneumoniae in France in 2007: data from the pneumococcus surveillance network.

Antimicrobial resistance of Streptococcus pneumoniae in France is closely monitored by the pneumococcus surveillance network, founded in 1995, which collects data from regional observatories (Observatoire Régionaux du Pneumocoque [ORP]). In 2007, 23 ORPs analyzed the antibiotic susceptibility of 5,302 isolates of S. pneumoniae recovered in France from cerebrospinal fluid, blood, middle ear fluid, and pleural fluid, as well as from adult respiratory samples. The study showed that 38.2% of the strains were nonsusceptible to penicillin, 19.3% nonsusceptible to amoxicillin, and 10.5% nonsusceptible to cefotaxime. The percentage of pneumococcus nonsusceptible to penicillin varied according to both the sample and the age of the patient (child/adult): blood (27.8%/32.5%), cerebrospinal fluid (33.7%/34.6%), middle ear fluid (60.2%/27.5%), and pleural fluid (50.0%/31.0%). Between 2003 and 2007, the frequency of penicillin resistance in invasive pneumococcal disease gradually decreased from 46.4% to 29.0% in children and from 43.8% to 32.7% in adults. This decrease coincided with the introduction of a seven-valent pneumococcal conjugate vaccine into immunization programs and with a general reduction in levels of antibiotic consumption in France.

Serotype distribution and antibiotic resistance of Streptococcus pneumoniae strains isolated from adults in France: evolution between 2001 and 2003.

Antibiotic-resistant Streptococcus pneumoniae (Sp) are described around the world. The present national surveillance study report analyzes more than 6000 Sp strains, isolated from adults across France in 2001 and 2003, from blood cultures (3086 in 2001 and 3164 in 2003), cerebrospinal fluid (respectively, 238 and 240), or middle ear fluid (respectively, 110 and 100). The proportion of isolates with reduced susceptibility to penicillin fell significantly between 2001 and 2003 from 46.5% to 43.9%. The proportion of high-level resistant strains to penicillin minimal inhibitory concentrations (MIC > 1 mg/L), amoxicillin, and cefotaxime (MIC > 2 mg/L) slightly decreased but remained low: 10.6%, 1.2%, and 0.2% in 2003. Resistance to other antibiotics (erythromycin, cotrimoxazole, tetracycline, and chloramphenicol) also decreased. Decrease in prevalence of penicillin-resistant Sp varied according to specimen source. The proportion of penicillin nonsusceptible pneumococci decreased in blood cultures and middle ear fluids between 2001 and 2003 but increased in cerebrospinal fluid (43.4% and 46.5%, respectively). Serotypes covered by the heptavalent vaccine accounted for 42.4% of all isolates recovered in 2001 and 46.1% in 2003. Prevalence of antibiotic-resistant Sp decreased in 2003 in France.

Genetic and biochemical characterization of the first extended-spectrum CARB-type beta-lactamase, RTG-4, from Acinetobacter baumannii.

Acinetobacter baumannii isolate KAR was uncommonly more resistant to cefepime and cefpirome than to ceftazidime and cefotaxime. Cloning and expression of the beta-lactamase gene content of this isolate into Escherichia coli TOP10 identified ss-lactamase RTG-4 (or CARB-10), which corresponds to the first reported extended-spectrum CARB-type enzyme. RTG-4 is a plasmid-encoded Ambler class A beta-lactamase whose sequence differs by 4 amino acid substitutions from the narrow-spectrum beta-lactamase RTG-3. RTG-4 hydrolyzes cefepime and cefpirome and weakly hydrolyzes ceftazidime due to the single Ser-to-Thr substitution at Ambler position 69. RTG-4 is less susceptible to inhibition by tazobactam and sulbactam than RTG-3. Expression of beta-lactamase RTG-4 in a wild-type A. baumannii reference strain showed that it conferred resistance to cefepime and cefpirome. The genetic environment of the bla(RTG-4) gene was made of a peculiar transposon located on a ca. 50-kb plasmid. ISAba9, located upstream of bla(RTG-4), may be responsible for its acquisition by recognizing a secondary right inverted repeat sequence, thus acting by a one-ended transposition process.

In vivo selection of reduced susceptibility to carbapenems in Acinetobacter baumannii related to ISAba1-mediated overexpression of the natural bla(OXA-66) oxacillinase gene.

Two clonally related Acinetobacter baumannii isolates, A1 and A2, were obtained from the same patient. Isolate A2, selected after an imipenem-containing treatment, showed reduced susceptibility to carbapenems. This resistance pattern was related to insertion of the ISAba1 element upstream of the naturally occurring bla(OXA-66) carbapenemase gene as demonstrated by sequencing, reverse transcription-PCR analysis, and inactivation of the bla(OXA-66) gene.

Chlorhexidine-impregnated sponges and less frequent dressing changes for prevention of catheter-related infections in critically ill adults: a randomized controlled trial.

CONTEXT: Use of a chlorhexidine gluconate-impregnated sponge (CHGIS) in intravascular catheter dressings may reduce catheter-related infections (CRIs). Changing catheter dressings every 3 days may be more frequent than necessary. OBJECTIVE: To assess superiority of CHGIS dressings regarding the rate of major CRIs (clinical sepsis with or without bloodstream infection) and noninferiority (less than 3% colonization-rate increase) of 7-day vs 3-day dressing changes. DESIGN, SETTING, AND PATIENTS: Assessor-blind, 2 x 2 factorial, randomized controlled trial conducted from December 2006 through June 2008 and recruiting patients from 7 intensive care units in 3 university and 2 general hospitals in France. Patients were adults (>18 years) expected to require an arterial catheter, central-vein catheter, or both inserted for 48 hours or longer. INTERVENTIONS: Use of CHGIS vs standard dressings (controls). Scheduled change of unsoiled adherent dressings every 3 vs every 7 days, with immediate change of any soiled or leaking dressings. MAIN OUTCOME MEASURES: Major CRIs for comparison of CHGIS vs control dressings; colonization rate for comparison of 3- vs 7-day dressing changes. RESULTS: Of 2095 eligible patients, 1636 (3778 catheters, 28,931 catheter-days) could be evaluated. The median duration of catheter insertion was 6 (interquartile range [IQR], 4-10) days. There was no interaction between the interventions. Use of CHGIS dressings decreased the rates of major CRIs (10/1953 [0.5%], 0.6 per 1000 catheter-days vs 19/1825 [1.1%], 1.4 per 1000 catheter-days; hazard ratio [HR], 0.39 [95% confidence interval {CI}, 0.17-0.93]; P = .03) and catheter-related bloodstream infections (6/1953 catheters, 0.40 per 1000 catheter-days vs 17/1825 catheters, 1.3 per 1000 catheter-days; HR, 0.24 [95% CI, 0.09-0.65]). Use of CHGIS dressings was not associated with greater resistance of bacteria in skin samples at catheter removal. Severe CHGIS-associated contact dermatitis occurred in 8 patients (5.3 per 1000 catheters). Use of CHGIS dressings prevented 1 major CRI per 117 catheters. Catheter colonization rates were 142 of 1657 catheters (7.8%) in the 3-day group (10.4 per 1000 catheter-days) and 168 of 1828 catheters (8.6%) in the 7-day group (11.0 per 1000 catheter-days), a mean absolute difference of 0.8% (95% CI, -1.78% to 2.15%) (HR, 0.99; 95% CI, 0.77-1.28), indicating noninferiority of 7-day changes. The median number of dressing changes per catheter was 4 (IQR, 3-6) in the 3-day group and 3 (IQR, 2-5) in the 7-day group (P < .001). CONCLUSIONS: Use of CHGIS dressings with intravascular catheters in the intensive care unit reduced risk of infection even when background infection rates were low. Reducing the frequency of changing unsoiled adherent dressings from every 3 days to every 7 days modestly reduces the total number of dressing changes and appears safe. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00417235.

Identical penicillin-binding domains in penicillin-binding proteins of Streptococcus pneumoniae clinical isolates with different levels of beta-lactam resistance.

We have sequenced the penicillin-binding domains of the complete repertoire of penicillin-binding proteins and MurM from 22 clinical isolates of Streptococcus pneumoniae that span a wide range of beta-lactam resistance levels. Evidence of mosaicism was found in the genes encoding PBP 1a, PBP 2b, PBP 2x, MurM, and, possibly, PBP 2a. Five isolates were found to have identical PBP and MurM sequences, even though the MICs for penicillin G ranged from 0.25 to 2.0 mg/liter. When the sequences encoding PBP 1a, PBP 2b, and PBP 2x from one of these isolates were used to transform laboratory strain R6, the resulting strain had a resistance level higher than that of the less resistant isolates carrying that PBP set but lower than that of the most resistant isolates carrying that PBP set. This result demonstrates that if the R6 strain is arbitrarily defined as the standard genotype, some wild genetic backgrounds can either increase or decrease the PBP-based resistance phenotype.

Biochemical characterization of Streptococcus pneumoniae penicillin-binding protein 2b and its implication in beta-lactam resistance.

Extensive use of beta-lactam antibiotics has led to the selection of pathogenic streptococci resistant to beta-lactams due to modifications of the penicillin-binding proteins (PBPs). PBP2b from Streptococcus pneumoniae is a monofunctional (class B) high-molecular-weight PBP catalyzing the transpeptidation between adjacent stem peptides of peptidoglycan. The transpeptidase domain of PBP2b isolated from seven clinical resistant (CR) strains contains 7 to 44 amino acid changes over the sequence of PBP2b from the R6 beta-lactam-sensitive strain. We show that the extracellular soluble domains of recombinant PBP2b proteins (PBP2b*) originating from these CR strains have an in vitro affinity for penicillin G that is reduced by up to 99% from that of the R6 strain. The Thr446Ala mutation is always observed in CR strains and is close to the key conserved motif (S(443)SN). The Thr446Ala mutation in R6 PBP2b* displays a 60% reduction in penicillin G affinity in vitro compared to that for the wild-type protein. A recombinant R6 strain expressing the R6 PBP2b Thr446Ala mutation is twofold less sensitive to piperacillin than the parental S. pneumoniae strain. Analysis of the Thr446Ala mutation in the context of the PBP2b CR sequences revealed that its influence depends upon the presence of other unidentified mutations.

A PBP2x from a clinical isolate of Streptococcus pneumoniae exhibits an alternative mechanism for reduction of susceptibility to beta-lactam antibiotics.

The human pathogen Streptococcus pneumoniae is one of the main causative agents of respiratory tract infections. At present, clinical isolates of S. pneumoniae often exhibit decreased susceptibility toward beta-lactams, a phenomenon linked to multiple mutations within the penicillin-binding proteins (PBPs). PBP2x, one of the six PBPs of S. pneumoniae, is the first target to be modified under antibiotic pressure. By comparing 89 S. pneumoniae PBP2x sequences from clinical and public data bases, we have identified one major group of sequences from drug-sensitive strains as well as two distinct groups from drug-resistant strains. The first group includes proteins that display high similarity to PBP2x from the well characterized resistant strain Sp328. The second group includes sequences in which a signature mutation, Q552E, is found adjacent to the third catalytic motif. In this work, a PBP2x from a representative strain from the latter group (S. pneumoniae 5259) was biochemically and structurally characterized. Phenotypical analyses of transformed pneumococci show that the Q552E substitution is responsible for most of the reduction of strain susceptibility toward beta-lactams. The crystal structure of 5259-PBP2x reveals a change in polarity and charge distribution around the active site cavity, as well as rearrangement of strand beta3, emulating structural changes observed for other PBPs that confer drug resistance to Gram-positive pathogens. Interestingly, the active site of 5259-PBP2x is in closed conformation, whereas that of Sp328-PBP2x is open. Consequently, S. pneumoniae has evolved to employ the same protein in two distinct mechanisms of antibiotic resistance.

The structural modifications induced by the M339F substitution in PBP2x from Streptococcus pneumoniae further decreases the susceptibility to beta-lactams of resistant strains.

PBP2x is a primary determinant of beta-lactams resistance in Streptococcus pneumoniae. Altered PBP2x with multiple mutations have a reduced "affinity" for the antibiotics. An important polymorphism is found in PBP2x sequences from clinical resistant strains. To understand the mechanism of resistance, it is necessary to identify and characterize the relevant substitutions. Many similar PBP2x sequences from resistant isolates have the previously studied T338A mutation, adjacent to the active site Ser337. We report here the structural and functional analysis of the M339F substitution that is found in a subset of these sequences, originating from highly resistant strains. The M339F mutation causes a 4-10-fold reduction of the reaction rate with beta-lactams, depending on the molecular context. In addition, release of the inactivated antibiotic from the active site is up to 3-fold faster as a result from the M339F mutation. These effects measured in vitro are correlated with the level of beta-lactam resistance in vivo conferred by several PBP2x variants. Thus, a single amino acid difference between similar PBP2x from clinical isolates can strongly modulate the degree of beta-lactam resistance. The crystal structure of the double mutant T338A/M339F solved to a resolution of 2.4 A shows a distortion of the active site and a reorientation of the hydroxyl group of the active site Ser337, which can explain the kinetic effects of the mutations.

Incidence and prevalence of methicillin-resistant Staphylococcus aureus nasal carriage among healthcare workers in geriatric departments: relevance to preventive measures.

Methicillin-resistant Staphylococcs aureus (MRSA) nasal carriage was assessed among healthcare workers caring for elderly patients in contact precautions in geriatric departments. Monthly incidence ranged from 0% to 3.3%. Carriage was observed only among nurses and nursing assistants. MRSA was thus infrequently acquired using precautions and carriage was usually transient.