Methicillin-susceptible Staphylococcus aureus CC398: first description in prosthetic joint infection and genetic background comparison with nasal carriage isolates.

Few reports described infections with CC398 methicillin-susceptible Staphylococcus aureus (MSSA). We compared the genetic background of CC398 MSSA strains from nasal carriage and knee arthroplasty infection. DNA microarray analysis shows acquisition of particular adhesin, iron capture system and immune defense evasion mechanisms. These characteristics could explain pathogenesis in this type of infection.

TEM-187, a new extended-spectrum ß-lactamase with weak activity in a Proteus mirabilis clinical strain.

A Proteus mirabilis clinical strain (7001324) was isolated from urine sample of a patient hospitalized in a long-term-care facility. PCR and cloning experiments performed with this strain identified a novel TEM-type ß-lactamase (TEM-187) differing by four amino acid substitutions (Leu21Phe, Arg164His, Ala184Val, and Thr265Met) from TEM-1. This characterization provides further evidence for the diversity of extended-spectrum ß-lactamases (ESBL) produced by P. mirabilis and for their potential spread to other Enterobacteriaceae due to a lack of sensitive detection methods used in daily practice.

Gallibacterium anatis bacteremia in a human.

We describe the first case of bacteremia due to Gallibacterium anatis. The patient, a 26-year-old woman, developed bacteremia and diarrhea. The origin of infection was possibly due to a diet contaminated by G. anatis in this highly immunocompromised patient.

Detection of clonally related Escherichia coli isolates producing different CMY ß-lactamases from a cystic fibrosis patient.

OBJECTIVES: This study reports details on Escherichia coli isolates recovered from a cystic fibrosis (CF) patient in order to understand how this pathogen adapts to and resists broad-spectrum antipseudomonal therapy in this context. METHODS: Five E. coli isolates were obtained from various clinical samples (airways, urine or dialysis catheter) over a 7 month period covering a double-lung transplantation. All isolates were analysed in terms of clonality [enterobacterial repetitive intergenic consensus (ERIC)-PCR and multilocus sequence typing], virulence profiles (phylogroup and search for 15 virulence genes), growth patterns (morphotype, biofilm-forming ability and growth rate), hypermutability and antimicrobial susceptibility, with molecular characterization of ß-lactamases and porins. RESULTS: The five isolates shared similar ERIC-PCR profiles and sequence types (ST1193) and exhibited the same virulence profile. The respiratory isolates were strong mutators, exhibited mucoid or small-colony morphotypes, exhibited strong biofilm-forming ability and grew slowly compared with the others. All isolates were highly resistant to ceftazidime. The respiratory isolates showed reduced susceptibility to cefepime and high resistance to aztreonam. The patient had received a 31 day course of ceftazidime/aztreonam until transplantation. All isolates harboured the same wild-type chromosomal AmpC. A CMY-2 enzyme was detected in the non-respiratory isolates. The respiratory isolates harboured L293S and V211A/L293S new CMY-2 variants, which were designated CMY-94 and CMY-95, respectively. OmpF porin loss was observed in the non-respiratory isolates. CONCLUSIONS: Our study shows that, similarly to Pseudomonas aeruginosa, E. coli can undergo phenotypic and genomic changes in the CF context. For the first time, we identified an in vivo expanded-spectrum evolution of the CMY-2 ß-lactamase, during bacterial persistence in the CF lung.

Relapse of Serratia marcescens sternal osteitis 15 years after the first episode.

Sternal osteitis, a potential consequence of cardiac surgery, remains rare. The bacteria involved belong mostly to the genus Staphylococcus. Sternal infections caused by Serratia marcescens are exceptional. We report an unusual recurrence of sternal infection with S. marcescens, 15 years after the initial episode. The identities of the isolates were determined by genomic analysis.

Genotypic and phenotypic characterization of Staphylococcus epidermidis causing chronic relapsing prosthetic joint infections.

Twenty-one isolates of Staphylococcus epidermidis from 9 patients with persistent prosthetic joint infections were analysed by pulsed-field gel electrophoresis and antibiotic susceptibility assays. In 7 of these cases, the S. epidermidis isolate was different from that of the initial episode. In 1 further case, the superinfection was polyclonal. Recurrence, i.e., renewed isolation of a clone identical to that of an initial episode, occurred in 3 cases, 1 of which was in the absence of superinfection. A high degree of antibiotic resistance was demonstrated, including methicillin in 17 of 21 strains. In conclusion, a frequent occurrence of superinfection and a high degree of resistance make management of these infections complex.

Escherichia coli-induced productions of pro-inflammatory cytokines are regulated by MAP kinases and G-protein but not by Akt: Relationship with phylogenetic groups and resistance patterns.

INTRODUCTION: We investigated the role of PI3-K, MAP kinases, and heterotrimeric G proteins in inducing cytokines production in human whole blood cultures stimulated by viable Escherichia coli (E. coli) clinical strains. MATERIALS AND METHODS: We used eight E. coli strains that belong to different phylogenetic groups and presented by different antibiotic resistance patterns. Whole blood from healthy volunteers was incubated at 37°C for 150min, with lipopolysaccharide (LPS) from E. coli O111:B4 or selected viable E. coli clinical strains, with or without SB202190 (p38 inhibitor), PD98059 (ERK inhibitor), PTX (pertussis toxin; heterotrimeric G proteins inhibitor), wortmaninn (PI3-K inhibitor). The TNF-α, IL-1ß, IL-10 and IFN-γ concentrations were measured in culture supernatants (ELISA). RESULTS: IL-10 and IFN-γ were not detectable. Susceptible strains induced higher TNF-α and IL-1ß productions than ß-lactam resistant strains (p<0.05), with no difference between phylogenetic groups. A transformed strain carrying a plasmid-mediated AmpC-ß-lactamase gene (CMY-2) induced lower TNF-α and IL-1ß production than the parent wild type strain (p<0.05). SB202190 (p38 inhibitor) and PD98059 (ERK inhibitor) reduced TNF-α concentrations by, respectively, 80% (p<0.05) and 50% (p<0.05). Wortmaninn (PI3-K inhibitor) had no significant effect. PTX (heterotrimeric G proteins inhibitor) altered TNF-α production after viable bacteria stimulation (1.7-fold increase; p<0.05) but not after LPS (TLR-4) stimulation. Regarding IL-1ß, wortmaninn, SB202190 and PTX had no significant effect whereas PD98059 significantly decreased production in whole cell cultures (p<0.05). CONCLUSION: Susceptible strains induce greater TNF-α and IL-1ß productions than resistant strains. ERK kinase plays a major role in viable E. coli strains inducing TNF-α and IL-1ß production. E. coli exerts an effect on the pertussis toxin-sensitive G-protein through a TLR-4-independent mechanism.

Occurrence of ST23 complex phylogroup A Escherichia coli isolates producing extended-spectrum AmpC beta-lactamase in a French hospital.

Extended-spectrum AmpC beta-lactamase (ESAC) Escherichia coli producers were investigated over a 5-year period. Eleven isolates presenting a strong ampC promoter and different strategic AmpC mutations, including two newly described modifications (A292V and an L-A-A insertion at 295), were characterized. All the isolates belonged to phylogenetic group A and to the ST23 complex.

Fatal coinfection with Legionella pneumophila serogroup 8 and Aspergillus fumigatus.

Legionella pneumophila is an important cause of community-acquired and nosocomial pneumonia. We report on a patient who simultaneously developed L. pneumophila serogroup 8 pneumonia and Aspergillus fumigatus lung abscesses. Despite appropriate treatments, Aspergillus disease progressed with metastasis. Coinfections caused by L. pneumophila and A. fumigatus remain exceptional. In apparently immunocompetent patients, corticosteroid therapy is a key risk factor for aspergillosis.

Real-time PCR assay for the detection and quantification of Legionella pneumophila in environmental water samples: utility for daily practice.

We developed a quantitative real-time PCR assay targeting the mip gene of Legionella pneumophila for a prospective study from September 2004 to April 2005. It was compared with a standard culture method (French guideline AFNOR T90-431), analysing 120 water samples collected to monitor the risk related to Legionellae at Nantes hospital and to investigate a case of legionellosis acquired from hospital environment. Samples from six distinct water distribution systems were analysed by DNA extraction, amplification and detection with specific primers and FRET probes. The detection limit was 100 genomic units of L. pneumophila per liter (GU/l), the positivity threshold about 600 GU/l and the quantification limit 800 GU/l. PCR results were divided into three groups: negative (n=63), positive but non-quantifiable (n=22) or positive (n=35). PCR showed higher sensitivity than culture, whereas four culture-positive samples appeared negative by PCR (PCR inhibitor detected for two of them). Although no correlation was observed between both methods and real-time PCR cannot substitute for the reference method, it represents an interesting complement. Its sensitivity, reproducibility and rapidity appear particularly interesting in epidemic contexts in order to identify the source of contamination or to evaluate critical points of contamination in water distribution systems.

Increased resistance to beta-lactams in a Klebsiella pneumoniae strain: role of a deletion downstream of the Pribnow box in the blaSHV-1 promoter.

Two hundred and five isolates of Klebsiella pneumoniae were collected from Nantes University Hospital in 2002. A new 30bp deletion was detected downstream of the -10 box of the SHV-1 promoter in a clinical K. pneumoniae isolate with a high amoxicillin/clavulanic acid minimum inhibitory concentration. Reverse transcription polymerase chain reaction revealed increased transcription of bla(SHV-1) mRNA. All conjugation mating assays failed. This new promoter was cloned upstream of the cat gene of the reporter plasmid pKK232-8 and compared with previously described bla(SHV-1) promoters. The deletion induced a 15-fold increase in promoter strength compared with the usual weak promoter. This study reports a new genetic event that increases bla(SHV-1) chromosomal gene expression, which may be of clinical relevance when associated with porin deficiency.

Effect of zinc gluconate on propionibacterium acnes resistance to erythromycin in patients with inflammatory acne: in vitro and in vivo study.

Tetracyclines and macrolide antibiotics have been in use for acne treatment for more than 20 years. Since 1992 increasing resistance to these antibiotics, and especially to erythromycin, is reported with Propionibacterium acnes. Zinc salts have demonstrated their efficacy in inflammatory acne treatment as well as their bacteriostatic activity against Propionibacterium acnes. The objective of our work was firstly to determine whether the clinical anti-inflammatory efficacy of zinc salts was altered in the presence of erythromycin resistant strains in vivo, and secondly to study the in vitro and in vivo effect of zinc on the sensitivity of Propionibacterium acnes strains to erythromycin. Thirty patients with inflammatory acne were treated by zinc gluconate with a daily dose of 30 mg for two months and bacteriologic samples were taken at D0, D30 and D60. In vivo, this study displayed a reduction in the number of inflammatory lesions after a 2-month treatment whether or not Propionibacterium acnes carriage was present. Concurrently, in vitro addition of zinc salts in the culture media of Propionibacterium acnes reduced resistance of Propionibacterium acnes strains to erythromycin. Thus, association of zinc salts via a systemic route and topical erythromycin treatment seems an interesting option in the light of an increasing number of patients carrying erythromycin resistant Propionibacterium acnes strains.

Detection of an IS21 insertion sequence in the mexR gene of Pseudomonas aeruginosa increasing beta-lactam resistance.

To understand the regulation of the MexAB OprM efflux system in a clinical strain of Pseudomonas aeruginosa presenting a decreased susceptibility to ticarcillin and aztreonam, the mexR repressor gene was amplified by polymerase chain reaction (PCR) and was shown to be disrupted by an insertion sequence of more than 2 kb, with characteristic direct and inverted repeat sequences. Sequencing revealed a 2131-bp IS21 insertion sequence. A reverse transcription PCR method was used to quantify mexA transcripts and showed an increased transcription rate of mexA in this strain, compared with a PAO1 control strain. The nalB phenotype in P. aeruginosa may be due to point mutations, but also to the presence of an insertion sequence in the mexR regulator gene.

Comparison of two RT-PCR methods for quantifying ampC specific transcripts in Escherichia coli strains.

In Escherichia coli, beta-lactam resistance usually depends on beta-lactamase production. AmpC chromosomal cephalosporinase hyperproduction is generally due to mutations in the ampC gene promoter. In order to study ampC expression in E. coli clinical strains, we have compared two methods: conventional and real-time reverse transcription-polymerase chain reaction (RT-PCR). With both methods, ampC mRNA was found to be greatly increased in strains presenting -42 or -32 mutations in the ampC promoter, and moderately increased when a -11 mutation was present in the Pribnow box. Real-time RT-PCR represents a powerful tool combining amplification, fluorescent detection and analysis.

Investigation and management of multidrug-resistant Acinetobacter baumannii spread in a French medical intensive care unit: one outbreak may hide another.

An outbreak in a medical intensive care unit was due to an OXA-23-producing Acinetobacter baumannii strain imported from a repatriate hospitalized in Singapore. This outbreak revealed another multidrug resistant epidemic strain that had been present in the hospital for 2 years. Both outbreaks were controlled after 9 months of an extensive infection control program.

Orthopaedic-implant infections by Escherichia coli: molecular and phenotypic analysis of the causative strains.

OBJECTIVES: Little is known about Escherichia coli Orthopaedic Implant Infections (OII) pathogenesis. Thus, we compared 30 clinical strains isolated in this context with 30 clinical strains of faecal origin, in order to identify phenotypic and genetic features related to E. coli OII. METHODS: Phylogenetic analysis and detection of 19 virulence genes were performed by PCR. Ability to form biofilm was studied using the crystal violet reference method and the innovative BioFilm Ring Test(®). RESULTS: Most of the OII isolates (56.7%) belonged to the virulence-associated phylogenetic group B2, but did not present a specific set of virulence factors. S fimbriae was the only adhesin significantly associated with OII isolates. Isolates varied greatly in their ability to form biofilm but OII isolates did not produce significantly more biofilm in vitro than isolates of faecal origin, whatever the method used. CONCLUSIONS: Neither a specific pathogenic signature nor an increased ability to form biofilm in vitro was detected in E. coli strains isolated from OII. Nevertheless, genetic properties of these isolates could provide a clue to their origin. Hence, we found that virulence factors of uropathogenic strains and urological disorders were frequently detected among our OII cohort.

Occurrence and molecular characterization of Klebsiella pneumoniae ST37 clinical isolates producing plasmid-mediated AmpC recovered over a 3-year period.

We investigated the clinical and microbiological epidemiology of AmpC plasmidic cephalosporinases (pAmpC) in Klebsiella pneumoniae strains resistant to ceftazidime, during a 3-year period (2007-2009). Among 1505 K. pneumoniae, 7 were pAmpC producers. Molecular characterization revealed the spread of a ST37 strain producing DHA-1 within intensive care units and the diffusion of the same plasmid among unrelated strains.