Outer membrane porin M35 of Moraxella catarrhalis mediates susceptibility to aminopenicillins

BACKGROUND: The outer membrane protein M35 is a conserved porin of type 1 strains of the respiratory pathogen Moraxella catarrhalis. It was previously shown that M35 is involved in the uptake of essential nutrients required for bacterial growth and for nasal colonization in mice. The aim of this study was (i) to characterize the potential roles of M35 in the host-pathogen interactions considering the known multifunctionality of porins and (ii) to characterize the degree of conservation in the phylogenetic older subpopulation (type 2) of M. catarrhalis. RESULTS: Isogenic m35 mutants of the type 1 strains O35E, 300 and 415 were tested for their antimicrobial susceptibility against 15 different agents. Differences in the MIC (Minimum Inhibitory Concentration) between wild-type and mutant strains were found for eight antibiotics. For ampicillin and amoxicillin, we observed a statistically significant 2.5 to 2.9-fold MIC increase (p < 0.03) in the m35 mutants. Immunoblot analysis demonstrated that human saliva contains anti-M35 IgA. Wild-type strains and their respective m35 mutants were indistinguishable with respect to the phenotypes of autoagglutination, serum resistance, iron acquisition from human lactoferrin, adherence to and invasion of respiratory tract epithelial cells, and proinflammatory stimulation of human monocytes. DNA sequencing of m35 from the phylogenetic subpopulation type 2 strain 287 revealed 94.2% and 92.8% identity on the DNA and amino acid levels, respectively, in comparison with type 1 strains. CONCLUSION: The increase in MIC for ampicillin and amoxicillin, respectively, in the M35-deficient mutants indicates that this porin affects the outer membrane permeability for aminopenicillins in a clinically relevant manner. The presence of IgA antibodies in healthy human donors indicates that M35 is expressed in vivo and recognized as a mucosal antigen by the human host. However, immunoblot analysis of human saliva suggests the possibility of antigenic variation of immunoreactive epitopes, which warrants further analysis before M35 can be considered a potential vaccine candidate.

H-ficolin serum concentration and susceptibility to fever and neutropenia in paediatric cancer patients

H-ficolin (Hakata antigen, ficolin-3) activates the lectin pathway of complement similar to mannose-binding lectin. However, its impact on susceptibility to infection is currently unknown. This study investigated whether the serum concentration of H-ficolin at diagnosis is associated with fever and neutropenia (FN) in paediatric cancer patients. H-ficolin was measured by time-resolved immunofluorometric assay in serum taken at cancer diagnosis from 94 children treated with chemotherapy. The association of FN episodes with H-ficolin serum concentration was analysed by multivariate Poisson regression. Median concentration of H-ficolin in serum was 26 mg/l (range 6-83). Seven (7%) children had low H-ficolin (< 14 mg/l). During a cumulative chemotherapy exposure time of 82 years, 177 FN episodes were recorded, 35 (20%) of them with bacteraemia. Children with low H-ficolin had a significantly increased risk to develop FN [relative risk (RR) 2.24; 95% confidence interval (CI) 1.38-3.65; P = 0.004], resulting in prolonged duration of hospitalization and of intravenous anti-microbial therapy. Bacteraemia occurred more frequently in children with low H-ficolin (RR 2.82; CI 1.02-7.76; P = 0.045). In conclusion, low concentration of H-ficolin was associated with an increased risk of FN, particularly FN with bacteraemia, in children treated with chemotherapy for cancer. Low H-ficolin thus represents a novel risk factor for chemotherapy-related infections.

Stable expression of Escherichia coli beta-glucuronidase A (GusA) in Giardia lamblia: application to high-throughput drug susceptibility testing

OBJECTIVES: In order to create a suitable model for high-throughput drug screening, a Giardia lamblia WB C6 strain expressing Escherichia coli glucuronidase A (GusA) was created and tested with respect to susceptibility to the anti-giardial drugs nitazoxanide and metronidazole. METHODS: GusA, a well-established reporter gene in other systems, was cloned into the vector pPacVInteg allowing stable expression in G. lamblia under control of the promoter from the glutamate dehydrogenase (gdh) gene. The resulting transgenic strain was compared with the wild-type strain in a vitality assay, characterized with respect to susceptibility to nitazoxanide, metronidazole and -- as assessed in a 96-well plate format -- to a panel of 15 other compounds to be tested for anti-giardial activity. RESULTS: GusA was stably expressed in G. lamblia. Using a simple glucuronidase assay protocol, drug efficacy tests yielded results similar to those from cell counting. CONCLUSIONS: G. lamblia WB C6 GusA is a suitable tool for high-throughput anti-giardial drug screening.

SerpinB1 deficiency is not associated with increased susceptibility to pulmonary emphysema in mice

Chronic obstructive pulmonary disease (COPD) is characterized by emphysema and chronic bronchitis and is a leading cause of morbidity and mortality worldwide. Tobacco smoke and deficiency in α1-antitrypsin (AAT) are the most prominent environmental and genetic risk factors, respectively. Yet the pathogenesis of COPD is not completely elucidated. Disease progression appears to include a vicious circle driven by self-perpetuating lung inflammation, endothelial and epithelial cell death, and proteolytic degradation of extracellular matrix proteins. Like AAT, serpinB1 is a potent inhibitor of serine proteases including neutrophil elastase and cathepsin G. Because serpinB1 is expressed in myeloid and lung epithelial cells and is protective during lung infections, we investigated the role of serpinB1 in preventing age-related and cigarette smoke-induced emphysema in mice. Fifteen-month-old mice showed increased lung volume and decreased pulmonary function compared with young adult mice (3 mo old), but no differences were observed between serpinB1-deficient (KO) and wild-type (WT) mice. Chronic exposure to secondhand cigarette smoke resulted in structural emphysematous changes compared with respective control mice, but no difference in lung morphometry was observed between genotypes. Of note, the different pattern of stereological changes induced by age and cigarette smoke suggest distinct mechanisms leading to increased airway volume. Finally, expression of intracellular and extracellular protease inhibitors were differently regulated in lungs of WT and KO mice following smoke exposure; however, activity of proteases was not significantly altered. In conclusion, we showed that, although AAT and serpinB1 are similarly potent inhibitors of neutrophil proteases, serpinB1 deficiency is not associated with more severe emphysema.

A Preliminary Report on the Frequency of Scrapie Susceptibility Alleles in Hampshire Sheep

Blood samples were collected from a total of 201 animals in five purebred Hampshire sheep flocks. DNA was isolated from the samples, and the protein-coding region of the prion protein gene was amplified using the polymerase chain reaction. The allelic frequencies of the prion protein codons 171 and 136 were determined. Results revealed that the codon 171 alleles Q, R, and H were present at frequencies of 72%, 27% and 1%, respectively. A subset of samples (n=48) was randomly selected for codon 136 genotyping. The codon 136 V allele, an allele not frequently observed in Suffolk sheep, was present in animals from three of five flocks at a frequency ranging from 7 to 33% of the animals tested within each flock. These data comprise the first report on the prevalence of scrapie susceptibility alleles in Hampshire sheep.

Antibiotic Susceptibility of Mycoplasma bovis Strains Recovered From Mycoplasmal Pneumonia and Arthritis in Feedlot Cattle

Mycoplasmal pneumonia and arthritis is a problem of increasing significance in Midwestern feedlots. The disease presentation cannot be prevented by vaccination or successfully treated with antimicrobials. Due to the reported difficulty in treating these outbreaks, in-vitro antimicrobial susceptibility was tested on isolates of Mycoplasma bovis recovered from cases of pneumonia or pneumonia and arthritis where the mycoplasma was involved as a causative agent. Using a broth microdilution method, 36 M. bovis isolates from cases of pneumonia and 9 from cases of pneumonia and arthritis were tested for susceptibility to antimicrobials currently used in cattle with respiratory disease (ampicillin, tilmycosin, spectinomycin, tylosin, lincomycin, tetracycline, ceftiofur, and erythromycin). Among the isolates from cases with pneumonia, resistance to more antimicrobials was shown in recent isolates than in isolates from earlier years. Tetracycline and lincomycin were the drugs of choice for these isolates, although 3 of 36 isolates were resistant to all drugs tested. Isolates from cases of pneumonia and arthritis were from recent accessions. A majority of these isolates (5/9) were resistant to all antimicrobials tested. Lincomycin, spectinomycin, and tetracycline were antibiotics usable with 4/9 of the isolates. Overall, the results indicate that antimicrobial therapy in cases of mycoplasmal feedlot pneumonia and arthritis may be unrewarding.

Spectrum and prevalence of mutations involving BrS1- through BrS12-susceptibility genes in a cohort of unrelated patients referred for Brugada syndrome genetic testing: implications for genetic testing

OBJECTIVES The aim of this study was to provide the spectrum and prevalence of mutations in the 12 Brugada syndrome (BrS)-susceptibility genes discovered to date in a single large cohort of unrelated BrS patients. BACKGROUND BrS is a potentially lethal heritable arrhythmia syndrome diagnosed electrocardiographically by coved-type ST-segment elevation in the right precordial leads (V1 to V3; type 1 Brugada electrocardiographic [ECG] pattern) and the presence of a personal/family history of cardiac events. METHODS Using polymerase chain reaction, denaturing high-performance liquid chromatography, and DNA sequencing, comprehensive mutational analysis of BrS1- through BrS12-susceptibility genes was performed in 129 unrelated patients with possible/probable BrS (46 with clinically diagnosed BrS [ECG pattern plus personal/family history of a cardiac event] and 83 with a type 1 BrS ECG pattern only). RESULTS Overall, 27 patients (21%) had a putative pathogenic mutation, absent in 1,400 Caucasian reference alleles, including 21 patients with an SCN5A mutation, 2 with a CACNB2B mutation, and 1 each with a KCNJ8 mutation, a KCND3 mutation, an SCN1Bb mutation, and an HCN4 mutation. The overall mutation yield was 23% in the type 1 BrS ECG pattern-only patients versus 17% in the clinically diagnosed BrS patients and was significantly greater among young men<20 years of age with clinically diagnosed BrS and among patients who had a prolonged PQ interval. CONCLUSIONS We identified putative pathogenic mutations in ∼20% of our BrS cohort, with BrS genes 2 through 12 accounting for <5%. Importantly, the yield was similar between patients with only a type 1 BrS ECG pattern and those with clinically established BrS. The yield approaches 40% for SCN5A-mediated BrS (BrS1) when the PQ interval exceeds 200 ms. Calcium channel-mediated BrS is extremely unlikely in the absence of a short QT interval.

Flow-R, a model for susceptibility mapping of debris flows and other gravitational hazards at a regional scale

The development of susceptibility maps for debris flows is of primary importance due to population pressure in hazardous zones. However, hazard assessment by process-based modelling at a regional scale is difficult due to the complex nature of the phenomenon, the variability of local controlling factors, and the uncertainty in modelling parameters. A regional assessment must consider a simplified approach that is not highly parameter dependant and that can provide zonation with minimum data requirements. A distributed empirical model has thus been developed for regional susceptibility assessments using essentially a digital elevation model (DEM). The model is called Flow-R for Flow path assessment of gravitational hazards at a Regional scale (available free of charge under http://www.flow-r.org) and has been successfully applied to different case studies in various countries with variable data quality. It provides a substantial basis for a preliminary susceptibility assessment at a regional scale. The model was also found relevant to assess other natural hazards such as rockfall, snow avalanches and floods. The model allows for automatic source area delineation, given user criteria, and for the assessment of the propagation extent based on various spreading algorithms and simple frictional laws. We developed a new spreading algorithm, an improved version of Holmgren's direction algorithm, that is less sensitive to small variations of the DEM and that is avoiding over-channelization, and so produces more realistic extents. The choices of the datasets and the algorithms are open to the user, which makes it compliant for various applications and dataset availability. Amongst the possible datasets, the DEM is the only one that is really needed for both the source area delineation and the propagation assessment; its quality is of major importance for the results accuracy. We consider a 10 m DEM resolution as a good compromise between processing time and quality of results. However, valuable results have still been obtained on the basis of lower quality DEMs with 25 m resolution.

Candida species distribution and antifungal susceptibility testing according to European Committee on Antimicrobial Susceptibility Testing and new vs. old Clinical and Laboratory Standards Institute clinical breakpoints: a 6-year prospective candidaemia survey from the fungal infection network of Switzerland

We analyzed the species distribution of Candida blood isolates (CBIs), prospectively collected between 2004 and 2009 within FUNGINOS, and compared their antifungal susceptibility according to clinical breakpoints defined by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) in 2013, and the Clinical and Laboratory Standards Institute (CLSI) in 2008 (old CLSI breakpoints) and 2012 (new CLSI breakpoints). CBIs were tested for susceptiblity to fluconazole, voriconazole and caspofungin by microtitre broth dilution (Sensititre® YeastOne™ test panel). Of 1090 CBIs, 675 (61.9%) were C. albicans, 191 (17.5%) C. glabrata, 64 (5.9%) C. tropicalis, 59 (5.4%) C. parapsilosis, 33 (3%) C. dubliniensis, 22 (2%) C. krusei and 46 (4.2%) rare Candida species. Independently of the breakpoints applied, C. albicans was almost uniformly (>98%) susceptible to all three antifungal agents. In contrast, the proportions of fluconazole- and voriconazole-susceptible C. tropicalis and F-susceptible C. parapsilosis were lower according to EUCAST/new CLSI breakpoints than to the old CLSI breakpoints. For caspofungin, non-susceptibility occurred mainly in C. krusei (63.3%) and C. glabrata (9.4%). Nine isolates (five C. tropicalis, three C. albicans and one C. parapsilosis) were cross-resistant to azoles according to EUCAST breakpoints, compared with three isolates (two C. albicans and one C. tropicalis) according to new and two (2 C. albicans) according to old CLSI breakpoints. Four species (C. albicans, C. glabrata, C. tropicalis and C. parapsilosis) represented >90% of all CBIs. In vitro resistance to fluconazole, voriconazole and caspofungin was rare among C. albicans, but an increase of non-susceptibile isolates was observed among C. tropicalis/C. parapsilosis for the azoles and C. glabrata/C. krusei for caspofungin according to EUCAST and new CLSI breakpoints compared with old CLSI breakpoints.

Molecular epidemiology and antibiotic susceptibility of livestock Brucella melitensis isolates from Naryn Oblast, Kyrgyzstan.

The incidence of human brucellosis in Kyrgyzstan has been increasing in the last years and was identified as a priority disease needing most urgent control measures in the livestock population. The latest species identification of Brucella isolates in Kyrgyzstan was carried out in the 1960s and investigated the circulation of Brucella abortus, B. melitensis, B. ovis, and B. suis. However, supporting data and documentation of that experience are lacking. Therefore, typing of Brucella spp. and identification of the most important host species are necessary for the understanding of the main transmission routes and to adopt an effective brucellosis control policy in Kyrgyzstan. Overall, 17 B. melitensis strains from aborted fetuses of sheep and cattle isolated in the province of Naryn were studied. All strains were susceptible to trimethoprim-sulfamethoxazole, gentamicin, rifampin, ofloxacin, streptomycin, doxycycline, and ciprofloxacin. Multilocus variable number tandem repeat analysis showed low genetic diversity. Kyrgyz strains seem to be genetically associated with the Eastern Mediterranean group of the Brucella global phylogeny. We identified and confirmed transmission of B. melitensis to cattle and a close genetic relationship between B. melitensis strains isolated from sheep sharing the same pasture.

Antimicrobial susceptibility of gram-positive udder pathogens from bovine mastitis milk in Switzerland

We evaluated the susceptibility of the gram-positive mastitis pathogens S. aureus, Str. uberis, Str. dysgalactiae, E. faecalis and L. garviae to antibiotics that are of epidemiological interest or are critically important for mastitis therapy and human medicine. Penicillin resistance was found to be most frequent in S. aureus, and nearly 5 % of the Str. uberis strains displayed a decreased susceptibility to this antibiotic. Resistance to aminoglycosides and macrolides was also detected in the strains tested. The detection of methicillin-resistant S. aureus (MRSA) and of a ciprofloxacin-resistant Str. dysgalactiae isolate corroborated the emergence of mastitis pathogens resistant to critically important antibiotics and underscores the importance of susceptibility testing prior to antibiotic therapy. The monitoring of antibiotic susceptibility patterns and antibiogram analyses are strongly recommended for targeted antimicrobial treatment and to avoid the unnecessary use of the latest generation of antibiotics.

Genetic testing for TMEM154 mutations associated with lentivirus susceptibility in sheep.

In sheep, small ruminant lentiviruses cause an incurable, progressive, lymphoproliferative disease that affects millions of animals worldwide. Known as ovine progressive pneumonia virus (OPPV) in the U.S., and Visna/Maedi virus (VMV) elsewhere, these viruses reduce an animal's health, productivity, and lifespan. Genetic variation in the ovine transmembrane protein 154 gene (TMEM154) has been previously associated with OPPV infection in U.S. sheep. Sheep with the ancestral TMEM154 haplotype encoding glutamate (E) at position 35, and either form of an N70I variant, were highly-susceptible compared to sheep homozygous for the K35 missense mutation. Our current overall aim was to characterize TMEM154 in sheep from around the world to develop an efficient genetic test for reduced susceptibility. The average frequency of TMEM154 E35 among 74 breeds was 0.51 and indicated that highly-susceptible alleles were present in most breeds around the world. Analysis of whole genome sequences from an international panel of 75 sheep revealed more than 1,300 previously unreported polymorphisms in a 62 kb region containing TMEM154 and confirmed that the most susceptible haplotypes were distributed worldwide. Novel missense mutations were discovered in the signal peptide (A13V) and the extracellular domains (E31Q, I74F, and I102T) of TMEM154. A matrix-assisted laser desorption/ionization-time-of flight mass spectrometry (MALDI-TOF MS) assay was developed to detect these and six previously reported missense and two deletion mutations in TMEM154. In blinded trials, the call rate for the eight most common coding polymorphisms was 99.4% for 499 sheep tested and 96.0% of the animals were assigned paired TMEM154 haplotypes (i.e., diplotypes). The widespread distribution of highly-susceptible TMEM154 alleles suggests that genetic testing and selection may improve the health and productivity of infected flocks.

Serotype distribution and antimicrobial susceptibility of group B streptococci in pregnant women: results from a Swiss tertiary centre.

OBJECTIVE To evaluate the rates of penicillin, clindamycin and erythromycin resistance and the serotype distribution among isolates of group B streptococcus (GBS) obtained from pregnant women at the University Hospital of Bern in Switzerland. METHODS We prospectively collected screening samples for GBS colonisation at the University Women's Hospital Bern, Switzerland, between March 2009 and August 2010. We included 364 GBS isolates collected from vaginal, cervical or vaginal-perianal swabs at any gestation time. The minimal inhibitory concentrations for penicillin, clindamycin and erythromycin were established using Etest with 24 hours of incubation, and inducible clindamycin resistance was tested with double disk diffusion tests. Serotyping was done with a rapid latex agglutination test or, if not conclusive, with polymerase chain-reaction (PCR) testing. We looked for significant associations between resistance patterns, age groups, serotype and ethnicity. RESULTS All isolates were susceptible to penicillin. Resistance rates were 14.5% for erythromycin and 8.2% for clindamycin. Of 364 isolates, 5.8% were susceptible to clindamycin but not to erythromycin, although demonstrating inducible clindamycin resistance. Hence, the final reported clindamycin resistance rate was 14%. Serotype III was the most frequent serotype (29%), followed by V (25%) and Ia (19%). Serotype V was associated with erythromycin resistance (p = 0.0007). In comparison with all other ethnicities, patients from Asia showed a higher proportion of erythromycin and clindamycin resistance (p = 0.018). No significant association between resistance patterns and age groups was found. CONCLUSION In pregnant women with GBS colonisation, penicillin is the antibiotic of choice for intrapartum prophylaxis to prevent neonatal early-onset GBS sepsis. In women with penicillin allergy and at high risk for anaphylactic reaction, clindamycin may be an alternative. The resistance rate for clindamycin at our institution was 14%; therefore, susceptibility must be tested before administration.

Genetic variation in genes for the xenobiotic-metabolizing enzymes CYP1A1, EPHX1, GSTM1, GSTT1, and GSTP1 and susceptibility to colorectal cancer in Lynch syndrome.

Individuals with Lynch syndrome are predisposed to cancer due to an inherited DNA mismatch repair gene mutation. However, there is significant variability observed in disease expression likely due to the influence of other environmental, lifestyle, or genetic factors. Polymorphisms in genes encoding xenobiotic-metabolizing enzymes may modify cancer risk by influencing the metabolism and clearance of potential carcinogens from the body. In this retrospective analysis, we examined key candidate gene polymorphisms in CYP1A1, EPHX1, GSTT1, GSTM1, and GSTP1 as modifiers of age at onset of colorectal cancer among 257 individuals with Lynch syndrome. We found that subjects heterozygous for CYP1A1 I462V (c.1384A>G) developed colorectal cancer 4 years earlier than those with the homozygous wild-type genotype (median ages, 39 and 43 years, respectively; log-rank test P = 0.018). Furthermore, being heterozygous for the CYP1A1 polymorphisms, I462V and Msp1 (g.6235T>C), was associated with an increased risk for developing colorectal cancer [adjusted hazard ratio for AG relative to AA, 1.78; 95% confidence interval, 1.16-2.74; P = 0.008; hazard ratio for TC relative to TT, 1.53; 95% confidence interval, 1.06-2.22; P = 0.02]. Because homozygous variants for both CYP1A1 polymorphisms were rare, risk estimates were imprecise. None of the other gene polymorphisms examined were associated with an earlier onset age for colorectal cancer. Our results suggest that the I462V and Msp1 polymorphisms in CYP1A1 may be an additional susceptibility factor for disease expression in Lynch syndrome because they modify the age of colorectal cancer onset by up to 4 years.