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Volume 67,
Issue 8,
2018
Volume 67, Issue 8, 2018
- Editorial
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- Antimicrobial Resistance
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Antimicrobial resistance profiles of Shigella dysenteriae isolated from travellers returning to the UK, 2004–2017
Purpose. Antimicrobial resistance (AMR) profiles of 754 strains of Shigella dysenteriae isolated between 2004 and 2017 from UK travellers reporting symptoms of gastrointestinal (GI) disease were reviewed to look for evidence of emerging AMR associated with travellers’ diarrhoea.
Methodology. A travel history was provided for 72.7 % (548/754) of cases, of which 90.9 % (498/548) reported travel outside the UK within 7 days of onset of symptoms, and 9.1 % (50/498) reported no travel in that time frame. During the course of this study, whole genome sequencing (WGS) was implemented for GI disease surveillance, and we compared phenotypic AMR profiles with those derived from WGS data (n=133).
Results/Key findings. The phenotypic and genotypic AMR results correlated well, with 90.1 % (121/133) isolates having concordant results to 10 classes of antimicrobials. Resistance to the first-line drugs commonly used in the treatment of shigellosis was observed throughout the study (ampicillin, 54.1%; chloramphenicol, 33.7 %; sulphonamides, 76.0 %; trimethoprim, 80.0%). Between 2004 and 2017, resistance to all classes of antimicrobials (except the phenicols) increased. The proportion of isolates exhibiting reduced susceptibility to ciprofloxacin increased from 3.8 % in 2004 to 75.7 % in 2017, and this was significantly associated with cases reporting travel to Asia compared to Africa (P<0.001). Of the 201 sequenced isolates, 3.0 % (20/201) had either bla CTX-M-15 or bla CMY-4.
Conclusions. Increasing MDR, along with resistance to the fluroquinolones and the third generation cephalosporins, in Shigella dysenteriae causing travellers’ diarrhoea provides further evidence for the need to regulatethe use of antimicrobial agents and continuous monitoring of emerging AMR.
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Epidemic spread of OXA-48 beta-lactamase in Croatia
Branka Bedenić, Mia Slade, Lidija Žele Starčević, Sanda Sardelić, Mirna Vranić-Ladavac, Ana Benčić, Vlasta Zujić Atalić, Maja Bogdan, Marina Bubonja-Šonje, Maja Tomić-Paradžik, Tatjana Tot, Amarela Lukić-Grlić, Domagoj Drenjančević, Dijana Varda-Brkić, Daniela Bandić-Pavlović, Slobodan Mihaljević, Gernot Zarfel, Marija Gužvinec, Rick Conzemius, Ivan Barišić and Arjana Tambić-AndraševicPurpose. A dramatic increase in OXA-48 β-lactamase was observed recently not only in large hospital centres, but also in smaller suburban hospital centres in geographic areas bordering Croatia. The aim of the study was to analyse the epidemiology, the mechanisms of antibiotic resistance and the routes of spread of OXA-48 carbapenemase in Croatia.
Methods. Carbapenemase and other β-lactamase and fluoroquinolone resistance genes were detected by PCR and sequencing. Whole-genome sequencing (WGS) was performed on five representative isolates. The isolates were genotyped by PFGE.
Results. Forty-eight isolates positive for OXA-48, collected from seven hospital centres in Croatia from May 2016 to May 2017, were analysed (40 Klebsiella pneumoniae, 5 Enterobacter cloacae, 2 Escherichia coli and one Citrobacter freundii). Thirty-three isolates were ESBL positive and harboured group 1 CTX-M 1 β-lactamases. In addition to the β-lactam resistance genes detected by PCR (bla SHV-1, bla OXA-48 and bla OXA-1), WGS of five representative isolates revealed the presence of genes encoding aminoglycoside resistance, aadA2 and aph3-Ia, fluoroquinolone resistance determinants aac(6)Ib-c, oqxA and oqxB, the sulfonamide resistance gene sul1, and fosA (fosfomycin resistance). IncL plasmid was found in all isolates. Two K. pneumoniae isolates belonged to ST16, two E. cloacae to ST66 and E. coli to ST354. K. pneumoniae isolates were allocated to five clusters by PFGE which occured in different hospitals, indicating epidemic spread.
Conclusions. The OXA-48-positive organisms found in this study showed wide variability in antibiotic susceptibility, β-lactamase content and PFGE banding patterns. This study revealed a switch from the predominance of VIM-1 in 2012–2013 to that of OXA-48 in the 2015 to 2017.
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Bactericidal efficacy of molybdenum oxide nanoparticles against antimicrobial-resistant pathogens
More LessMultidrug-resistant bacteria pose a major threat to effective antibiotics and alternatives to fight multidrug-resistant pathogens are needed. We synthetized molybdenum oxide (MoO3) nanoparticles (NP) and determined their antibacterial activity against 39 isolates: (i) eight Staphylococcus aureus, including representatives of methicillin-resistant S. aureus epidemic clones; (ii) six enterococci, including vancomycin-resistant isolates; and (iii) 25 Gram-negative isolates (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, Enterobacter cloacae), including extended spectrum beta-lactamases and carbapenemases producers. All isolates showed a MoO3 NP MIC of 700–800 mg l−1. MoO3 NP produced a clear inhibition zone for S. aureus and all Gram-negative isolates at concentrations ≥25 mg ml−1 and ≥50 mg ml−1 for enterococci. When the NP solutions were adjusted to pH ~7, the biocidal activity was completely abolished. MoO3 NP create an acidic pH and show a universal antimicrobial activity against susceptible and resistant isolates belonging to the most relevant bacterial species responsible for hospital-acquired infections.
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A clinical isolate of Escherichia coli co-harbouring mcr-1 and bla NDM-5 in Japan
More LessThe mcr-1 gene encodes a phosphoethanolamine transferase, which confers resistance to colistin by transferring phosphoethanolamine to lipid A. This study describes the emergence of a colistin- and carbapenem-resistant clinical isolate of Escherichia coli harbouring mcr-1 and bla NDM-5 genes, located on 90 and 150 Kb plasmids, respectively. The isolate belonged to ST132. This is the first report of a clinical isolate in Japan co-harbouring mcr-1 and bla NDM-5.
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- Clinical Microbiology
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Sexually transmitted rectal infections in a cohort of ‘men having sex with men’
Purpose. We assessed the prevalence and predictors of Chlamydia trachomatis, Neisseriagonorrhoeae and Mycoplasmagenitalium rectal infections in a population of ‘men having sex with men’ (MSM).
Methodology. From January to November 2017, 165 MSM attending a STI outpatients clinic in Bologna (Italy) and reporting unsafe anal intercourses were enrolled. An ano-rectal swab was collected from each patient: chlamydial and gonococcal infections were diagnosed by a commercial NAAT, whereas an in-house quantitative PCR was used for M. genitalium detection. In addition, 131 urine samples and 84 pharyngeal swabs underwent testing for C. trachomatis and N. gonorrhoeae. A molecular C. trachomatis typing, a serological screening for anti-Chlamydia IgG and IgA, as well as the assessment of HIV, HCV and syphilis infections, were performed.
Results/Key findings. The prevalence of C. trachomatis, N. gonorrhoeae and M. genitalium rectal infections was 27.2, 25.4 and 4.8 %, respectively. Globally, 63.1 % of cases were asymptomatic and up to 80 % of chlamydial and gonococcal infections would have been missed if the rectal site had not been tested. All the patients with rectal M. genitalium carriage were asymptomatic and characterized by low bacterial loads (<2500 DNA copies/reaction). Lymphogranuloma venereum (LGV) prevalence was 12.1 % with a considerable proportion of asymptomatic infections (35 %). The presence of symptoms, age >30, HIV-positivity and elevated levels of anti-Chlamydia antibodies were the most significant predictors of LGV.
Conclusions. Sexually transmitted rectal infections are frequent and often asymptomatic among MSM. LGV prevalence is high in our country and there is increasing evidence of symptomless cases.
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Streptococcus and Prevotella are associated with the prognosis of oesophageal squamous cell carcinoma
Purpose. Oesophageal squamous cell carcinoma (ESCC) is the dominant type of oesophageal cancer among the East Asian population. The role of ESCC tissue bacteria in neoplastic progression has not been fully elucidated. Our goal was to uncover different bacterial communities in pathological staging grouping of ESCC and to identify microorganisms that could predict the likelihood of prognosis.
Methodology. Tissue samples were obtained from 45 patients and assessed using 16S ribosomal RNA gene sequencing. Significant bacteria were selected to perform survival analysis and evaluate prognostic biomarker.
Results/Key findings. We observed variations in the abundance of oesophageal flora among different pathological characteristics of ESCC. Phylum Bacteroidetes, Firmicutes and Spirochaetes showed significantly higher relative abundances among N+ (positive lymph node) patients when compared to N– (negative lymph node) controls, whereas Proteobacteria showed lower abundances in N+ patients. Both genera Prevotella and Treponema were more abundant in the N+ group. In regard to T stage, the abundance of only Streptococcus in T3–4 was significantly higher than that in T1–2, while the other genera showed no significance. On multivariable analysis adjusted for the effects of standard clinicopathological features, combined Streptococcus and Prevotella abundance retained its association with unfavourable survival (hazard ratio, 6.094; 95 % confidence interval, 1.072–34.646; P=0.042), suggesting that this may be an independent prognostic indicator for ESCC.
Conclusion. Combined Streptococcus and Prevotella abundance is regarded as an independent species prognostic biomarker in ESCC patients.
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The emergence of multi-resistant Enterococcus faecalis clonal complex, CC4, causing nosocomial infections
Purpose. Enterococcus faecalis is commonly found as a commensal gut bacteria, but some linages have caused increasing extra-gastrointestinal infections. In particular, strains with high-level virulence or antimicrobial resistance are prevalent in healthcare settings as nosocomial pathogens. This study was performed to elucidate the epidemiological characteristics and antimicrobial susceptibility profiles of E. faecalis causing nosocomial infections in a Chinese general hospital over a 4-year period.
Methodology. We collected 77 isolates causing extra-gastrointestinal infections from patients at 14 different wards in a tertiary hospital from 2011 to 2014. The population relationship was assessed by multilocus sequence typing and multilocus variable-number tandem repeat analysis. The Kirby–Bauer disk diffusion method was used to evaluate susceptibility against 11 antimicrobial agents.
Results. The isolates showed high-level resistance to tetracycline (86.5 %), erythromycin (78.4 %), rifampin (62.2 %), etc. The major clonal complexes (CCs) included CC4, CC16 and CC21. As the most dominant subtype, CC16 was identified in almost all of the wards and all types of samples, but the isolation rate decreased continually. In contrast, the isolation rates of CC4 and CC21 increased and the proportion of these two CCs in 2014 was more than three times that in 2011. In addition, CC4 showed higher resistance than CC16.
Conclusions. This study demonstrated the prevalent subtypes and resistance profiles of E. faecalis causing nosocomial infection, and indicated that CC4 may be a newly emerging high-risk, multi-resistant cluster. More surveillance is urgently needed, which will increase our understanding of the prevention and treatment of such infections.
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Liver involvement is associated with blood culture positivity and high agglutination titre in patients with brucellosis in Turkey
More LessWe investigated the incidence of and risk factors for liver involvement (LI) in patients with brucellosis in Turkey. Diagnosis was established by blood cultures (BCs) or compatible clinical presentation accompanied by serological evidence. Patients received either a combination of doxycycline plus rifampin for 6 weeks or doxycycline for 6 weeks plus streptomycin intramuscularly for the first 2 weeks. Liver function tests, including those for alanine (ALT) and aspartate aminotransferase (AST) levels, were monitored before and at the end of treatment. One hundred and ninety-five patients were included in the study. Seventy patients had elevated transaminases before treatment. Twenty-six patients had a positive BC for brucellosis. In multivariate analysis, BC positivity (OR=2.44, 95 % CI: 1.03–5.78, P=0.043) and serum agglutination titre (SAT) (OR=1.001, 95 % CI: 1.00–1.002, P=0.018) were found to be associated with LI. Serum aminotransferase levels were normalized in all patients with brucellosis. BC positivity and high SAT are independent factors that are associated with LI in patients with brucellosis.
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- Disease, Diagnosis and Diagnostics
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Hypervirulent Klebsiella pneumoniae, a 5-year study in a French ICU
Purpose. Hypervirulent Klebsiella pneumoniae (hvKp) has emerged as a leading cause of severe community-acquired pneumonia, liver abscess and disseminated infection in the Far East. Data regarding the incidence, clinical features and microbiological characteristics related to hvKp infections in the Western world are scarce.
Methodology. The incidence, clinical features and microbiological characteristics of hvKp infections were investigated through a 5-year survey conducted in a single French intensive care unit. K. pneumoniae strains were screened for hypermucoviscosity based on a string test. Multilocus sequence typing and multiplex PCR analysis targeting virulence genes were performed on string test-positive strains.
Results. Over a 53-month period, a total of 59 infections due to K. pneumoniae were identified including 26 community-onset infections. Twelve hvKp infections were documented, accounting for 46.1 % of community-acquired K. pneumoniae. Community-acquired pneumonia (n=6), aspiration pneumonia (n=4) and liver abscess (n=2) represented initial sites and mode of infection. Compared to non-hvKp infections, patients with hvKp infections displayed higher rates of multi-organ failure (83.3 % vs 35.7 %; P=0.04), but mortality rates were not different (50 % vs 35 %; P=0.71). Strains K1/ST23 (n=5) and K2/ST86 (n=5) predominated. All hvKp strains displayed wild-type susceptibility.
Conclusion. hvKp represent a potentially underestimated cause of fatal infections in the Western world.
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Bactibilia in women affected with diseases of the biliary tract and pancreas. A STROBE guidelines-adherent cross-sectional study in Southern Italy
Purpose. Bile is a hepatobiliary lipid-rich sterile solution, and its colonization by microorganisms defines the condition of bactibilia. In this study, we aimed to assess the bile microbiological flora and its potential link with comorbidity in women.
Methodology. We performed a microbiologic investigation on 53 female patients with biliopancreatic diseases who granted consent, and we analysed the data using a MATLAB platform.
Results. We found that the most frequent disease associated with bactibilia was pancreas head carcinoma (PHC) (P=0.0015), while the least frequent disease was gall bladder carcinoma (GBC) (P=0.0002). The most common microorganisms were Pseudomonas spp. (P<0.0001) and Escherichia coli (P<0.0001). In particular Pseudomonas spp. and E. coli were negatively correlated to PHC presence and positively correlated to CCA by both univariate and multivariate analysis.
Conclusions. Gram-negative bacteria have been linked to a tumour-associated inflammatory status. In the last 30 years, the analysis of mortality rate in Italy for PHC and GBC shows an increasing and a decreasing trend, respectively. Although this study targeted only 53 patients and does not reflect the frequency of diagnosis in a Southern Italian population, the decrease in GBC may raise the suggestion ofnon-adherence to a Mediterranean diet that may have become more prevalent in Southern Italy since the 1990s.
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- Microbial Ecology and Health
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Ecology and diversity in upper respiratory tract microbial population structures from a cross-sectional community swabbing study
Purpose. Respiratory tract infections (RTIs) are responsible for over 2.8 million deaths per year worldwide with pathobiont carriage a required precursor to infection. We sought to determine carriage epidemiology for both bacterial and viral respiratory pathogens as part of a large population-based cross-sectional carriage study.
Methodology. Nose self-swab samples were collected in two separate time-points, May to August 2012 (late spring/summer) and February to April 2013 (winter/early spring). The presence of six bacterial species: S. pneumoniae, H. influenzae, M. catarrhalis, S. aureus, P. aeruginosa and N. meningitidis in addition to respiratory syncytial virus, influenza viruses A and B, rhinovirus/enterovirus, coronavirus, parainfluenza viruses 1–3 and adenovirus was determined using culture and PCR methods.
Results/Key findings. Carriage was shown to vary with age, recent RTI and the presence of other species. Spatial structures of microbial communities were more disordered in the 0–4 age group and those with recent RTI. Species frequency distributions were flatter than random expectation in young individuals (X2=20.42, P=0.002), indicating spatial clumping of species consistent with facilitative relationships. Deviations from a neutral model of ecological niches were observed in summer samples and from older individuals but not in the winter or younger individuals (0–4 years), suggesting the presence of seasonal and age-dependent niche processes in respiratory community assembly.
Conclusion. The application of epidemiological methods and ecological theory to respiratory tract samples has yielded novel insights into the factors that drive microbial community composition.
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- Microbial Epidemiology
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In-depth molecular analysis of a small cohort of human and Aedes mosquito (adults and larvae) samples from Kolkata revealed absence of Zika but high prevalence of dengue virus
More LessPurpose. Zika virus infections have recently been reported in many dengue-endemic areas globally. Both dengue (DENV) and Zika (ZIKV) virus are transmitted by Aedes mosquitoes, raising the possibility of mixed infections in both vector and host. We evaluated DENV and ZIKV prevalence in human and vector samples in Kolkata, a DENV-endemic city.
Methodology. Blood samples were collected from 70 patients presenting dengue-like fever symptoms at a hospital in Kolkata during 2015–16. Serum was obtained and tested for DENV infection by DENV NS1-based ELISA. Adult (n=8) and larval stages (n=12) of Aedes were also collected. A RT-PCR-based screening of both viruses supplemented by amplicon sequencing was performed.
Results. Of the 70 samples, 20 DENV NS1-positive serum samples were used for detailed molecular study for DENV infection. Eighteen of these (90 %) were positive by hemi-nested serotype-specific RT-PCR for DENV1/2/3, with four samples showing evidence of DENV2-3 or DENV1-3 mixed infection. None were ZIKV-positive using NS5 or ENV-based PCR, though weak amplification of a DENV1 NS5 sequence was detected in three serum samples indicating cross-reactivity of the primers. All mosquito samples were ZIKV-negative, whereas 5/8 (63 %) of adult mosquitoes and 11/12 (92 %) of larvae were DENV3-positive.
Conclusion. Both host and vector samples showed absence of ZIKV but high prevalence of DENV. The high rate of infection of larvae with DENV is suggestive of trans-ovarial transmission that could contribute to the surge of human infections during each post-monsoon season. It would be important to guard against false positives using the available Zika-reporting primer sets.
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Identification of recombinant coxsackievirus A6 variants in hand, foot and mouth disease in Nanjing, China, 2013
Purpose. Enteroviruses (EV) 71 and coxsackievirus A (CVA) 16 are the most prevalent EV serotypes responsible for hand, foot and mouth disease (HFMD). Nevertheless, CVA6 was found to be the leading cause of HFMD in the Nanjing area, of China in 2013. This study aims to provide insights into the occurrence of the emergent recombinant CVA6 through examination of the evolutionary history and the involved recombination events.
Methodology. The viral protein1 (VP1) and non-structural (NS) 2C and 3D of 28 Nanjing CVA6 strains were aligned, among which the full-length sequences of eight strains were further characterized.
Results. We revealed the co-existence of two recombinant forms (RFs), RF-A and RF-J, in the local area. RF-J is a novel RF group, comprising a proportion of local and Shanghai CVA6 strains from 2013. The appearance of RF-J CVA6 strains was most likely the result of two recombination events, with the co-circulating CVA4 and CVA8 providing the regions beyond positions 4001~4045 and 4866~4873, respectively. Evolutionary history analysis showed that the VP1 sequences of RF-J derived from RF-A, which was also probably the ancestor of several other RF groups. The 3D region of RF-J was closely related to CVA8. The point in time of emergence of the most recent common ancestor (tMRCA) of RF-J in China was estimated to be around 2011 in both terms of VP1 and 3D region.
Conclusion. The emerging recombinant CVA6 variants belong to a novel RF-J group which was most likely formed by at least two recombination events. Continued monitoring on the geographical distribution of various CVA6 RFs is essential.
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Genetic diversity of pneumococcal surface protein A (PspA) in paediatric isolates of non-conjugate vaccine serotypes in Japan
Purpose. Among the pneumococcal proteins, pneumococcal surface protein A (PspA) is considered the most promising candidate for a serotype-independent vaccine. This study aimed to investigate the serotype, genetic diversity of PspA, lineage (genotype) and drug resistance traits of pneumococcal isolates from paediatric patients.
Methodology. A total of 678 non-invasive pneumococcal isolates obtained from June to November 2016 were analysed. All isolates were characterized for PspA families, serotypes and macrolide resistance genes. Seventy-one representative isolates of non-vaccine serotypes (NVTs) were genetically analysed for the clade-defining region (CDR) of PspA, as well as multi-locus sequence typing (MLST).
Results. The detection rate of NVTs was 87.9 % (n=596), including dominant NVTs 15A (14.5 %, n=98), 35B (11.8 %, n=80), 15C (9.3 %, n=63) and 23A (9.0 %, n=61). Most isolates (96.6 %) possessed macrolide resistance genes erm(B) and/or mef(A/E). PspA families 1, 2 and 3 were detected in 42.3, 56.6 and 0.6 % of isolates, respectively. Nucleotide sequences of CDR showed high identity (90–100 %) within the same PspA clade, although the CDR identity among different PspA families ranged from 53 to 69 %. All isolates of NVTs 23A, 10A, 34, 24, 22F/22A, 33F, 23B and 38 were from PspA family 1, while NVTs 35B, 15C, 15B and 11A/11D isolates were from family 2. In contrast, genetically distinct PspAs were found in NVTs 6C and 15A. PspA family 3/clade 6 was detected in only NVT serotype 37 isolates assigned to ST447 and ST7970, showing the mucoid phenotype.
Conclusion. The present study revealed the predominance of PspA families 1 and 2 in NVTs, and the presence of family 3 in serotype 37.
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- Pathogenicity and Virulence/Host Response
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Outer-membrane protein LptD (PA0595) plays a role in the regulation of alginate synthesis in Pseudomonas aeruginosa
More LessPurpose. The presence of alginate-overproducing (Alg+) strains of Pseudomonas aeruginosa in cystic fibrosis patients is indicative of chronic infection. The Alg+ phenotype is generally due to a mutation in the mucA gene, encoding an innermembrane protein that sequesters AlgT/U, the alginate-specific sigma factor. AlgT/U release from the anti-sigma factor MucA is orchestrated via a complex cascade called regulated intramembrane proteolysis. The goal of this study is to identify new players involved in the regulation of alginate production.
Methodology. Previously, a mutant with a second-site suppressor of alginate production (sap), sap27, was isolated from the constitutively Alg+ PDO300 that harbours the mucA22 allele. A cosmid from a P. aeruginosa minimum tiling path library was identified via en masse complementation of sap27. The cosmid was transposon mutagenized to map the contributing gene involved in the alginate production. The identified gene was sequenced in sap27 along with algT/U, mucA, algO and mucP. The role of the novel gene was explored using precise in-frame algO and algW deletion mutants of PAO1 and PDO300.
Results/Key findings. The gene responsible for restoring the mucoid phenotype was mapped to lptD encoding an outer-membrane protein. However, the sequencing of sap27 revealed a mutation in algO, but not in lptD. In addition, we demonstrate that lipopolysaccharide transport protein D (LptD)-dependent alginate production requires AlgW in PAO1 and AlgO in PDO300.
Conclusion. LptD plays a specific role in alginate production. Our findings suggest that there are two pathways for the production of alginate in P. aeruginosa, one involving AlgW in the wild-type, and one involving AlgO in the mucA22 mutant.
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Insights into the genome diversity and virulence of two clinical isolates of Burkholderia cenocepacia
More LessPurpose. Burkholderia cenocepacia is among the most common members of the Burkholderia cepacia complex (Bcc) isolated from patients with cystic fibrosis (CF). The factors triggering the high rates of morbidity and mortality in CF patients are not well elucidated. In this study, we aim to highlight the genome diversity of two clinical isolates of B. cenocepacia through comparative genome analysis.
Methodology. The repertoire of virulence factors and resistance genes compared to reference strains J2315 and K56-2 was elucidated. The isolates were screened for the presence of phages and insertion sequences. Two methods were combined to obtain an accurate prediction of genomic islands (GIs): the cumulative GC profile and the IslandViewer web tool. To study evolutionary relatedness, whole genome-based single-nucleotide polymorphism (wgSNP) analysis was also performed with 43 publically available strains of the Bcc of various sequence types.
Results/Key findings. Genome-based species identification of the two isolates BC-AUH and BC-BMEH confirmed the species as B. cenocepacia. Both belonged to ST-602, a double-locus variant of ST-32 (CC31), genomovar IIIA, and carried a large number of antibiotic resistance genes. Eighteen GIs were predicted in BC-AUH and BC-BMEH, occupying 9.3 and 6.1 % of the respective genomes. Comparison to J2315 revealed 89 and 85 genes unique to BC-BMEH and BC-AUH, respectively. Additionally, 1823 intergenic SNPs were detected between BC-BMEH and BC-AUH.
Conclusion. This study mapped existing genetic variations in B. cenocepacia associated with notorious outcomes in CF patients, and the data obtained provide comprehensive, genome-inferred insights and multifactorial examination of an important human pathogen.
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ASC acts in a caspase-1-independent manner to worsen acute pneumonia caused by Pseudomonas aeruginosa
More LessPurpose. Pseudomonas aeruginosa expresses a type III secretion system (T3SS) that activates the host inflammasome-mediated immune response. We examined the role of inflammasome activation in severe infection outcomes.
Methods. We infected C57BL/6 (B6) mice lacking inflammasome components ASC or caspase-1/11 with a highly virulent strain of P. aeruginosa, PSE9, using a mouse model of pneumonia. We evaluated inflammasome activation in vitro by infecting bone marrow-derived macrophages (BMDMs) with PSE9 and measuring cell death and release of inflammasome-dependent cytokines IL-18 and IL-1β. A bioluminescent reporter assay was used to detect activity of caspase-1 and caspase-3/7 in BMDMs from B6 and ASC-deficient mice.
Results/Key Findings. ASC−/− mice exhibited significantly improved survival relative to caspase-1/11−/− mice and B6 mice, demonstrating that ASC and caspase-1/11 play differential roles in P. aeruginosa infection. We found that ASC−/− BMDMs exhibited significantly reduced cell death relative to B6 BMDMs, while caspase-1/11−/− BMDMs were resistant to cell death. IL-18 and IL-1β were both detected from supernatants of infected B6 BMDMs, but cytokine release was abrogated in both ASC−/− and caspase-1/11−/− BMDMs. We detected a 2.5-fold increase in the activation of caspase-3/7 in PSE9-infected B6 BMDMs, but no increase in infected ASC−/− BMDMs. Cell death, cytokine release and caspase-3/7 activity were dependent on a functional T3SS.
Conclusions. Collectively, these results are consistent with a model whereby the T3SS apparatus of P. aeruginosa activates the caspase-1-dependent inflammasome and caspase-3/7 through an ASC-dependent mechanism. This activation may have implications for the outcomes of P. aeruginosa infections.
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Changes in bacterial diversity and composition in the faeces and colon of weaned piglets after feeding fermented soybean meal
More LessPurpose. The microbiota composition of faeces and colonic contents were analysed to investigate the mechaninsm by which fermented soybean meal improves intestinal microbial communities, growth and immunity in weaning piglets.
Methodology. Microbiota were investigated using16S rRNA gene sequencing and systematical bio-information Operational Taxonomic Units; α-diversity analyses indicated that fermented soybean meal increased bacterial species diversity.
Results. The levels of Actinobacteria and Proteobacteia in faeces, and Firmicutes and Tenericutes in the colon, increased significantly in piglets fed fermented soybean meal (P<0.05). The relative abundance of Clostridium sensu stricto1, Lachnospira and Bacteoides had positive correlations with diarrhoea in the piglets. Lactobacillus, Blautia and Clostridium sensu stricto1 levels were correlated with increases in the average daily feed intake of piglets. Lactobacillus and Lachnospira also had positive relationships with IgM levels, and lymphocytes levels were increased relative to Clostridium sensu stricto1. Lymphocyte numbers also increased with higher levels of Blautia and decreased with Clostridium sensu stricto1. Increased levels of Blautia were also correlated with significant increases in white blood cells.
Conclusion. The significant differences in faecal and colonic bacteria were correlated with enhanced immunity and overall improved health in the weaning piglets.
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