Examining Phenotypic Traits Contributing to the Spread in Northern European Potato Crops of EU_41_A2, a New Clonal Lineage of Phytophthora infestans.

Until recently, genotypes of Phytophthora infestans were regionally distributed in Europe, with populations in western Europe being dominated by clonal lineages and those in northern Europe being genetically diverse because of frequent sexual reproduction. However, since 2013 a new clonal lineage (EU_41_A2) has successfully established itself and expanded in the sexually recombining P. infestans populations of northern Europe. The objective of this study was to study phenotypic traits of the new clonal lineage of P. infestans, which may explain its successful establishment and expansion within sexually recombining populations. Fungicide sensitivity, aggressiveness, and virulence profiles of isolates of EU_41_A2 were analyzed and compared with those of the local sexual populations from Denmark, Norway, and Estonia. None of the phenotypic data obtained from the isolates collected from Denmark, Estonia, and Norway independently explained the invasive success of EU_41_A2 within sexual Nordic populations. Therefore, we hypothesize that the expansion of this new genotype could result from a combination of fitness traits and more favorable environmental conditions that have emerged in response to climate change.

A single, plastic population of Mycosphaerella pinodes causes ascochyta blight on winter and spring peas (Pisum sativum) in France.

Plant diseases are caused by pathogen populations continuously subjected to evolutionary forces (genetic flow, selection, and recombination). Ascochyta blight, caused by Mycosphaerella pinodes, is one of the most damaging necrotrophic pathogens of field peas worldwide. In France, both winter and spring peas are cultivated. Although these crops overlap by about 4 months (March to June), primary Ascochyta blight infections are not synchronous on the two crops. This suggests that the disease could be due to two different M. pinodes populations, specialized on either winter or spring pea. To test this hypothesis, 144 pathogen isolates were collected in the field during the winter and spring growing seasons in Rennes (western France), and all the isolates were genotyped using amplified fragment length polymorphism (AFLP) markers. Furthermore, the pathogenicities of 33 isolates randomly chosen within the collection were tested on four pea genotypes (2 winter and 2 spring types) grown under three climatic regimes, simulating winter, late winter, and spring conditions. M. pinodes isolates from winter and spring peas were genetically polymorphic but not differentiated according to the type of cultivars. Isolates from winter pea were more pathogenic than isolates from spring pea on hosts raised under winter conditions, while isolates from spring pea were more pathogenic than those from winter pea on plants raised under spring conditions. These results show that disease developed on winter and spring peas was initiated by a single population of M. pinodes whose pathogenicity is a plastic trait modulated by the physiological status of the host plant.

In vivo selection of imipenem-resistant Klebsiella pneumoniae producing extended-spectrum beta-lactamase CTX-M-15 and plasmid-encoded DHA-1 cephalosporinase.

Four Klebsiella pneumoniae isolates (KP1-4) were recovered sequentially from an infected patient. Whilst KP1-3 were resistant to all beta-lactams except carbapenems, KP4 recovered after 24 days of imipenem-containing treatment showed additional resistance to carbapenems. No carbapenem hydrolysis could be identified in KP4. Molecular characterisation revealed that KP1-4 were indistinguishable by pulsed-field gel electrophoresis, contained a 95-kb self-transferable plasmid harbouring bla(CTXM-15) and bla(TEM-1) genes and a 65-kb plasmid that was not transferred by conjugation into Escherichia coli, and harboured the plasmid-mediated bla(DHA-1) AmpC beta-lactamase gene. In addition, KP4 failed to express OmpK36 owing to a point mutation leading to a premature stop of the protein. This study demonstrates development of carbapenem resistance related to loss of OmpK36 expression in a K. pneumoniae isolate harbouring extended-spectrum beta-lactamase and plasmid-mediated cephalosporinase genes following prolonged imipenem exposure.

Multidrug-resistant bacteria in hospitalized children: a 5-year multicenter study.

OBJECTIVE: The objective of this study was to determine the incidence of multidrug-resistant bacteria in hospitalized children. METHODS: This multicenter study was conducted in 5 hospitals in the Paris area from 1999 to 2003. We recorded all isolations of multidrug-resistant bacteria from clinical samples that were obtained from hospitalized children. Strains that were isolated during systematic screening for carriers were excluded. RESULTS: The mean incidences were 0.9 per 1000 hospitalization-days for methicillin-resistant Staphylococcus aureus, 0.45 for extended-spectrum beta-lactamase-producing Klebsiella pneumoniae, 0.32 for extended-spectrum beta-lactamase-producing Enterobacteriaceae other than Klebsiella pneumoniae, 0.40 for Enterobacter species with derepressed cephalosporinase, and 0.01 for vancomycin-resistant Enterococcus. The incidences per 1000 hospitalization-days of methicillin-resistant Staphylococcus aureus, extended-spectrum beta-lactamase-producing Klebsiella pneumoniae, extended-spectrum beta-lactamase-producing Enterobacteriaceae other than Klebsiella pneumoniae, and Enterobacter species with derepressed cephalosporinase decreased significantly from 1999 to 2003, whereas the incidence of vancomycin-resistant Enterococcus remained very low. The proportion of resistant strains within the species did not vary significantly for methicillin-resistant Staphylococcus aureus (11% to 9.6%), extended-spectrum beta-lactamase-producing Enterobacteriaceae other than Klebsiella pneumoniae (1.1%), and vancomycin-resistant Enterococcus (0.03% to 0.023%). In contrast, the frequency of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae decreased from 31.6% to 7.4%, and that of Enterobacter species with derepressed cephalosporinase decreased from 38.8% to 18.5%. CONCLUSIONS: We report significant decreases in the incidence of methicillin-resistant Staphylococcus aureus, extended-spectrum beta-lactamase-producing Klebsiella pneumoniae, extended-spectrum beta-lactamase-producing Enterobacteriaceae other than Klebsiella pneumoniae, and Enterobacter species with derepressed cephalosporinase in hospitalized children during a 5-year period.

Detection and treatment of antibiotic-resistant bacterial carriage in a surgical intensive care unit: a 6-year prospective survey.

OBJECTIVE: To describe, during a 6-year period, multidrug-resistant bacterial carriage in an intensive care unit (ICU). DESIGN: Prospective survey of 2235 ICU patients with methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E). SETTING: A surgical ICU in a tertiary-care teaching hospital. PATIENTS: All admitted patients. INTERVENTIONS: Nasal and rectal swabs were performed at admission and weekly thereafter. There was nasal application of mupirocin for MRSA carriers and selective digestive decontamination with local antibiotics for ESBL-E carriers. RESULTS: The swab compliance rate was 82% at admission and 51% during ICU stay. The rates of MRSA carriage or infection were 4.2 new cases per 100 admissions and 7.9 cases per 1000 patient-days during ICU stay. The rates of ESBL-E carriage or infection were 0.4 new case per 100 admissions and 3.9 cases per 1000 patient-days during ICU stay. Importation of MRSA increased significantly over time from 3.2 new cases per 100 admissions during the first 3 years to 5.5 during the last 3 years. The rate of ICU-acquired ESBLE decreased from 5.5 cases per 1000 patient-days during the first 3 years to 1.9 cases during the last 3 years. Nasal and digestive decontamination had low efficacy in eradicating carriage. CONCLUSIONS: MRSA remained poorly controlled throughout the hospital and was not just a problem in the ICU. MRSA thus requires more effective measures throughout the hospital. ESBL-E was mainly an ICU pathogen and our approach resulted in a clear decrease in the rate of acquisition in the ICU over time.

Use of INNO-LIPA assay for rapid identification of mycobacteria.

Using 106 clinical isolates of mycobacteria, we showed that INNO-LIPA Mycobacteria assay is an excellent tool to rapidly identify the most frequently isolated nontuberculous mycobacteria, in one procedure. It may be used as an additional technique to AccuProbe assay, which remains the fastest and the cheapest tool for a rapid and accurate identification of the M. tuberculosis complex.

Ralstonia pickettii traced in blood culture bottles.

Over a 9-month period, 14 strains of Ralstonia pickettii were isolated from various biological samples inoculated in a blood culture medium. Molecular epidemiological investigation confirmed the relatedness of the strains. The source of the contamination proved to be the blood culture bottle caps.