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Volume 69,
Issue 2,
2020
Volume 69, Issue 2, 2020

- Review
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Harnessing bacterial interactions to manage infections: a review on the opportunistic pathogen Pseudomonas aeruginosa as a case example
More LessDuring infections, bacterial pathogens can engage in a variety of interactions with each other, ranging from the cooperative sharing of resources to deadly warfare. This is especially relevant in opportunistic infections, where different strains and species often co-infect the same patient and interact in the host. Here, we review the relevance of these social interactions during opportunistic infections using the human pathogen Pseudomonas aeruginosa as a case example. In particular, we discuss different types of pathogen–pathogen interactions, involving both cooperation and competition, and elaborate on how they impact virulence in multi-strain and multi-species infections. We then review evolutionary dynamics within pathogen populations during chronic infections. We particuarly discuss how local adaptation through niche separation, evolutionary successions and antagonistic co-evolution between pathogens can alter virulence and the damage inflicted on the host. Finally, we outline how studying bacterial social dynamics could be used to manage infections. We show that a deeper appreciation of bacterial evolution and ecology in the clinical context is important for understanding microbial infections and can inspire novel treatment strategies.
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There is no hiding if you Seq: recent breakthroughs in Pseudomonas aeruginosa research revealed by genomic and transcriptomic next-generation sequencing
More LessThe advent of next-generation sequencing technology has revolutionized the field of prokaryotic genetics and genomics by allowing interrogation of entire genomes, transcriptomes and global transcription factor binding profiles. As more studies employing these techniques have been performed, the state of the art regarding prokaryotic gene regulation has developed from the level of individual genes to genetic regulatory networks and systems biology. When applied to bacterial pathogens, particularly valuable insights have been gained into the regulation of virulence-associated genes, their relative importance to bacterial survival in planktonic, biofilm or host infection scenarios, antimicrobial resistance and the molecular details of host–pathogen interactions. This review outlines some of the latest developments and applications of next-generation sequencing techniques that have used primarily Pseudomonas aeruginosa as a model system. We focus particularly on insights into Pseudomonas virulence and infection that have been gained from these approaches and the future directions in which this field could develop.
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Bacteriophages of Klebsiella spp., their diversity and potential therapeutic uses
More LessKlebsiella spp. are commensals of the human microbiota, and a leading cause of opportunistic nosocomial infections. The incidence of multidrug resistant (MDR) strains of Klebsiella pneumoniae causing serious infections is increasing, and Klebsiella oxytoca is an emerging pathogen. Alternative strategies to tackle infections caused by these bacteria are required as strains become resistant to last-resort antibiotics such as colistin. Bacteriophages (phages) are viruses that can infect and kill bacteria. They and their gene products are now being considered as alternatives or adjuncts to antimicrobial therapies. Several in vitro and in vivo studies have shown the potential for lytic phages to combat MDR K. pneumoniae infections. Ready access to cheap sequencing technologies has led to a large increase in the number of genomes available for Klebsiella -infecting phages, with these phages being heterogeneous at the whole-genome level. This review summarizes our current knowledge on phages of Klebsiella spp. and highlights technological and biological issues relevant to the development of phage-based therapies targeting these bacteria.
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Furanone quorum-sensing inhibitors with potential as novel therapeutics against Pseudomonas aeruginosa
More LessMicro-organisms use quorum sensing (QS), a cell density-dependent process, to communicate. This QS mode of interchange leads to the production of a variety of virulence factors, co-ordination of complex bacterial behaviours, such as swarming motility, degradation of host tissue and biofilm formation. QS is implicated in numerous human infections and consequently researchers have sought ways of effectively inhibiting the process in pathogenic bacteria. Two decades ago, furanones were the first class of chemical compounds identified as Pseudomonas aeruginosa QS inhibitors (QSIs). P. aeruginosa is a ubiquitous organism, capable of causing a wide range of infections in humans, including eye and ear infections, wound infections and potentially fatal bacteraemia and thus novel treatments against this organism are greatly needed. This review provides a brief background on QS and the use of furanones as QSIs. Based on the effectiveness of action, both in vivo and in vitro, we will explore the use of furanones as potential antimicrobial therapeutics and conclude with open questions.
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- Antimicrobial Resistance
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In vitro activity of imipenem-relebactam against resistant phenotypes of Enterobacteriaceae and Pseudomonas aeruginosa isolated from intraabdominal and urinary tract infection samples – SMART Surveillance Europe 2015–2017
Introduction. Infections attributable to carbapenem-resistant Gram-negative bacilli are increasing globally. New antimicrobial agents are urgently needed to treat patients with these infections.
Aim. To describe susceptibility to the novel carbapenem-β-lactamase inhibitor combination imipenem-relebactam and comparators of clinical isolates of non-Proteeae Enterobacteriaceae (NPE) and Pseudomonas aeruginosa from intraabdominal infections (IAIs) and urinary tract infections (UTIs).
Methods. Broth microdilution MICs were determined for isolates collected in 22 European countries in 2015–2017 and interpreted using EUCAST breakpoints; imipenem-relebactam MICs were interpreted using imipenem breakpoints.
Results. For NPE, 98.4 % of isolates from IAIs (n=10,465) and 98.5 % of UTI isolates (n=7,446) were susceptible to imipenem-relebactam, as were 42.4 % of imipenem-nonsusceptible (n=474), 98.6 % of Klebsiella pneumoniae carbapenemase (KPC)-positive (n=138), and 93.9 % of multidrug-resistant (MDR) isolates (n=4,424) from IAIs and UTIs combined. Molecular analysis demonstrated that two-thirds of imipenem-nonsusceptible isolates rendered susceptible by relebactam carried KPCs; 96 % (261/271) of imipenem-nonsusceptible isolates of NPE that remained nonsusceptible in the presence of relebactam carried metallo-β-lactamase (MBL)-type and/or OXA-48-like carbapenemases. Among P. aeruginosa , 94.4 % of IAI (n=1,245) and 93.0 % of UTI isolates (n=714) were susceptible to imipenem-relebactam, as were 74.4 % of imipenem-nonsusceptible (n=469) and 79.8 % of MDR isolates (n=595) from IAIs and UTIs combined. Among the 120 isolates of P. aeruginosa that remained nonsusceptible to imipenem upon addition of relebactam, 72 % carried MBLs. The distribution of NPE and P. aeruginosa carrying carbapenemases varied substantially across Europe, as did resistance to imipenem and imipenem-relebactam.
Conclusions. Continued surveillance of antimicrobial resistance and resistance mechanisms, including the study of imipenem-relebactam as it approaches regulatory approval, appears warranted.
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- Clinical Microbiology
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Presence of cagPAI genes and characterization of vacA s, i and m regions in Helicobacter pylori isolated from Alaskans and their association with clinical pathologies
Introduction. Gastric cancer is a health disparity in the Alaska Native people. The incidence of Helicobacter pylori infection, a risk factor for non-cardia gastric adenocarcinoma, is also high. Gastric cancer is partially associated with the virulence of the infecting strain.
Aim. To genotype the vacA s, m and i and cag pathogenicity island (cagPAI) genes in H. pylori from Alaskans and investigate associations with gastropathy.
Methodology. We enrolled patients with gastritis, peptic ulcer disease (PUD) and intestinal metaplasia (IM) in 1998–2005 and patients with gastric cancer in 2011–2013. Gastric biopsies were collected and cultured and PCR was performed to detect the presence of the right and left ends of the cagPAI, the cagA, cagE, cagT and virD4 genes and to genotype the vacA s, m and i regions.
Results. We recruited 263 people; 22 (8 %) had no/mild gastritis, 121 (46 %) had moderate gastritis, 40 (15%) had severe gastritis, 38 (14 %) had PUD, 30 (11 %) had IM and 12 (5 %) had gastric cancer. H. pylori isolates from 150 (57%) people had an intact cagPAI; those were associated with a more severe gastropathy (P≤0.02 for all comparisons). H. pylori isolates from 77 % of people had either the vacA s1/i1/m1 (40 %; 94/234) or s2/i2/m2 (37 %; 86/234) genotype. vacA s1/i1/m1 was associated with a more severe gastropathy (P≤0.03 for all comparisons).
Conclusions. In this population with high rates of gastric cancer, we found that just over half of the H. pylori contained an intact cagPAI and 40 % had the vacA s1/i1/m1 genotype. Infection with these strains was associated with a more severe gastropathy.
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An optimized algorithm with improved turnaround time for detection of carbapenemase-producing Enterobacterales using the NG Test CARBA 5 in a routine laboratory
More LessIntroduction. Rapid and reliable detection of carbapenemase-producing Enterobacterales (CPE) from surveillance cultures is critical in supporting a good infection control programme. We implemented a new algorithm for CPE detection incorporating the NG Test CARBA 5 in January 2019.
Aim. Our goals were to compare turnaround time (TAT), costs and staff requirements between the old and new algorithm, and to evaluate the performance of the CARBA 5 test directly on colonies grown on CARBA Smart agar.
Methodology. We analysed and compared the TAT of CPE surveillance cultures processed using the old and new CPE screening algorithm. The total actual reagent costs and staff requirements for the new CPE algorithm were compared with the estimated costs and staff requirements of the old CPE algorithm.
Results. Of 197 isolates included in the evaluation of the new algorithm, 64 were positive for carbapenemases by both CARBA 5 and Xpert Carba-R assay. Of the 133 that were negative, two were found to harbour NDM and IMI genotypes. Significant improvements in TAT were achieved with 88.7 % of cultures with CPE, reported on the same day as growth was observed on CARBA Smart agar compared to none in the old algorithm. The new algorithm incurred lower costs and, based on our workload, the new algorithm is estimated to save 28.9 man-hours annually.
Conclusion. CARBA 5 performs well on colonies growing on CARBA Smart agar and significant improvements in TAT can be achieved without incurring additional costs or staff requirements.
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Raoultella spp. – reliable identification, susceptibility to antimicrobials and antibiotic resistance mechanisms
More LessIntroduction. Raoultella spp. representatives are Gram-negative rod-shaped bacteria of the Enterobacteriaceae family. These bacteria are commonly found in the natural environment.
Aim. The aim of the study was to indicate the reliable method for Raoultella spp. strains identification, evaluate the susceptibility of Raoultella spp. strains to selected antimicrobials and to detect their resistance mechanisms to beta-lactams.
Methodology. Susceptibility of the strains to chosen antimicrobials was determined using the automatic method. The presence of particular antimicrobial resistant mechanism and genes encoding ESBLs and MBLs was determined respectively with double-disc synergy test and commercially available kit – eazyplex SuperBug CRE test (Amplex Diagnostics) and standard PCR. For the selected strains, DNA sequencing was performed.
Results. Amongst 105 of the examined Raoultella spp. strains, majority were sensitive to: imipenem (99.0 %), meropenem (98.1 %), gentamicin (93.3 %) and ciprofloxacin (92.4 %). Of the tested Raoultella strains, thirteen (12.4 %) produced ESBLs and one strain simultaneously ESBLs and MBLs. The DNA sequencing results were as follows: for all the reference strains the correct species identification was achieved, for the analysed strains two were identified as R. planticola and one as R. ornithinolytica .
Conclusion. Although Raoultella spp. strains remain sensitive to antibiotics, there is a constant need to monitor the sensitivity of these bacteria to selected antimicrobials. Isolation of a multi-drug resistant R. ornithinolytica strain indicates that even the less frequently isolated species of Enterobacteriaceae family should be precisely identified because they might be of clinical importance and the particular strain can also produce enzymes that pose the greatest threat today.
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First outbreak of Haemophilus influenzae clone ST422 with low susceptibility to quinolones in paediatric patients in Japan
Introduction. Recently, a Haemophilus influenzae clone with low susceptibility to quinolones emerged in paediatric patients in Japan. Isolates of this clone survived for a long time when exposed to the therapeutic concentration of quinolones, despite being classified as ‘susceptible’ under the criteria of the Clinical and Laboratory Standards Institute. In the present study, we report the first outbreak of this clone in paediatric patients in 2018.
Aim. Our aim was to characterise the first outbreak of an H. influenzae clone with low susceptibility to quinolones.
Methodology. All H. influenzae isolates (n=62), collected at a Japanese teaching hospital in 2018, were characterized by both antimicrobial susceptibility tests and multilocus sequence typing. In addition, the similarity in genetic backgrounds was analysed by PFGE.
Results. Among all the isolates (n=62), quinolone low-susceptible isolates accounted for 19.4 % (n=12). Seven out of 12 isolates were identified as sequence type 422 (ST422) and showed more than 90 % similarity to each other by PFGE analysis. All ST422 isolates exhibited identical amino acid substitutions in both quinolone resistance-determining regions in GyrA and ParC. In addition, all these isolates were from paediatric patients who had been referred by different primary care clinics and had no relationship to each other.
Conclusion. In this study, we describe an outbreak of a quinolone low-susceptible ST422 clone in paediatric patients in Japan. Because ST422 isolates have already been reported in at least five other countries, it has the potential to spread worldwide.
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- Disease, Diagnosis and Diagnostics
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Performance of the ResistancePlus MG diagnostic test for Mycoplasma genitalium using samples collected with Hologic Aptima Specimen Collection kits
Introduction. Mycoplasma genitalium is a sexually transmitted organism with high levels of resistance to the recommended first-line therapy, azithromycin. The ResistancePlus MG test concurrently detects M. genitalium, and the presence of macrolide-resistance mutations (MRM). European, UK and Australian guidelines recommend a diagnostic test that reports MRM to optimize treatment through resistance-guided therapy. Hence, for samples collected for use on other platforms, reflex testing using the ResistancePlus MG test would be beneficial.
Aim. To validate the ResistancePlus MG assay using samples collected in Aptima buffer for testing on the Hologic Panther.
Methodology. Positive (n=99) and negative (n=229) clinical samples collected in Aptima buffer were extracted on the MagNA Pure 96 (Roche Diagnostics), and tested with the ResistancePlus MG test on the LightCycler 480 II (Roche Diagnostics). Results were compared to matched samples collected using standard sample collection (urine or swab resuspended in PBS), with positive percent agreement (PPA), negative percent agreement (NPA) and Cohen’s Kappa statistic.
Results. The ResistancePlus MG test had high performance with a 200 µl input volume (PPA/NPA for M. genitalium detection, 92.9 % [95 % confidence interval (CI): 85.5–96.9]/100 % [95 % CI: 97.9–100], MRM detection, 96.9 % [95 % CI: 88.2–99.5]/85.7 % [95 % CI: 66.4–95.3]) and for 1 ml input volume (PPA/NPA for M. genitalium detection, 95.9%/96.6%, MRM detection, 98.4%/90.3%). Samples remained positive after storage at room temperature beyond the manufacturer-recommended storage of <60 days (mean storage time for 1 ml extraction: 129 days).
Conclusion. Samples collected using Aptima collection kits are suitable for reflex testing using the ResistancePlus MG test, allowing detection of macrolide resistance.
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Rapid multiplex detection of the resistance genes mecA, vanA and vanB from Gram-positive cocci-positive blood cultures using a PCR-dipstick technique
Introduction. Among the causative agents of bloodstream infections (BSIs), methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant Enterococcus (VRE) are the key causative pathogens. Their rapid detection directly from Gram-positive cocci-positive blood culture specimens will promote timely treatment and help to implement effective infection control measures.
Aim. We aim to develop a PCR-dipstick technique for the rapid detection of MRSA and VRE directly from positive blood culture specimens.
Methodology. PCR-dipstick is a PCR-based multiplex detection technique where DNA–DNA hybridization is employed, and the results are interpreted with the naked eye. It was designed to target three drug resistance genes: mecA in MRSA and vanA/vanB in VRE from positive blood culture specimens. A total of 120 clinical isolates were used to evaluate the sensitivity and specificity of PCR-dipstick. Then, PCR-dipstick was examined for MRSA and VRE detection directly from positive blood cultures.
Results. PCR-dipstick showed 100 % sensitivity and specificity in detecting mecA, vanA and vanB genes directly from bacterial colonies in comparison with multiplex PCR for genomic DNA followed by agarose gel electrophoresis. Further, it could differentially detect multiple resistant genes in pooled bacterial colonies (n=10). Ultimately, PCR-dipstick could detect MRSA and VRE in positive blood cultures in ~3 h.
Conclusion. The results of the current study substantiate that PCR-dipstick can be used as an efficient detection system for MRSA and VRE directly from Gram-positive cocci-positive blood cultures. Its affordability and rapidity indicate that PCR-dipstick can be an effective tool for controlling nosocomial pathogens.
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Validation of the Seegene RV15 multiplex PCR for the detection of influenza A subtypes and influenza B lineages during national influenza surveillance in hospitalized adults
J. J. LeBlanc, M. ElSherif, S. Mulpuru, M. Warhuus, A. Ambrose, M. Andrew, G. Boivin, W. Bowie, A. Chit, G. Dos Santos, K. Green, S. A. Halperin, T. F. Hatchette, B. Ibarguchi, J. Johnstone, K. Katz, J. M. Langley, P. Lagacé-Wiens, M. Loeb, A. Lund, D. MacKinnon-Cameron, A. McCarthy, J. E. McElhaney, A. McGeer, A. Poirier, J. Powis, D. Richardson, M. Semret, V. Shinde, D. Smyth, S. Trottier, L. Valiquette, D. Webster, L. Ye and S. A. McNeilBackground. The Serious Outcomes Surveillance Network of the Canadian Immunization Research Network (CIRN SOS) has been performing active influenza surveillance since 2009 (ClinicalTrials.gov identifier: NCT01517191). Influenza A and B viruses are identified and characterized using real-time reverse-transcriptase polymerase chain reaction (RT-PCR), and multiplex testing has been performed on a subset of patients to identify other respiratory virus aetiologies. Since both methods can identify influenza A and B, a direct comparison was performed.
Methods. Validated real-time RT-PCRs from the World Health Organization (WHO) to identify influenza A and B viruses, characterize influenza A viruses into the H1N1 or H3N2 subtypes and describe influenza B viruses belonging to the Yamagata or Victoria lineages. In a subset of patients, the Seeplex RV15 One-Step ACE Detection assay (RV15) kit was also used for the detection of other respiratory viruses.
Results. In total, 1111 nasopharyngeal swabs were tested by RV15 and real-time RT-PCRs for influenza A and B identification and characterization. For influenza A, RV15 showed 98.0 % sensitivity, 100 % specificity and 99.7 % accuracy. The performance characteristics of RV15 were similar for influenza A subtypes H1N1 and H3N2. For influenza B, RV15 had 99.2 % sensitivity, 100 % specificity and 99.8 % accuracy, with similar assay performance being shown for both the Yamagata and Victoria lineages.
Conclusions. Overall, the detection of circulating subtypes of influenza A and lineages of influenza B by RV15 was similar to detection by real-time RT-PCR. Multiplex testing with RV15 allows for a more comprehensive respiratory virus surveillance in hospitalized adults, without significantly compromising the reliability of influenza A or B virus detection.
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- Molecular and Microbial Epidemiology
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First isolation of human adenovirus type 85 by molecular analysis of adenoviruses in cases of urethritis
More LessIntroduction. Human adenovirus (HAdV) has been reported as a potential cause of sexually transmitted urethritis.
Aim. We aimed to investigate HAdVs associated with urethritis in Osaka, Japan through molecular characterization.
Methodology. Urine samples were obtained from male patients with urethritis from 2015 to 2018. Molecular analysis of the isolated strains and follow-up real-time polymerase chain reaction analyses of the clinical samples were performed.
Results. The isolates were classified into five types belonging to species D (18 cases) or E (one case). HAdV-85 (species D) was detected for the first time in a urethritis case. Follow-up examination demonstrated that HAdV was isolated from urine samples half a month after the first sampling in four cases, and that viral DNA could be detected after 1 month in two cases.
Conclusion. The HAdV types detected from urethritis cases were related to respiratory and ocular HAdV infections, while a novel HAdV type identified as a cause of conjunctivitis also causes urethritis. Sexual contact should be avoided for 1 month after HAdV genital infection.
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The longitudinal health economic impact of viral encephalitis in the United States
Introduction. Previous studies of viral encephalitis have focused on acute costs, estimating incidence at 7.3 per 100 000 and total US annual charges at $2 billion in 2010.
Aim. We aim to quantify the most updated longitudinal health economic impact of viral encephalitis in the USA from 2008 to 2015.
Methodology. Data on patients diagnosed with viral encephalitis were obtained from the Truven Health Analytics MarketScan database. Patients with a primary diagnosis of viral encephalitis, from herpetic viruses and other viral aetiologies (e.g. West Nile fever) were included in the analysis. Data concerning healthcare resource utilization, inpatient mortality, length of stay and accrued healthcare costs were collected for up to 5 years.
Results. Among 3985 patients with continuous enrolment for 13 months prior to the encephalitis diagnosis, more non-herpes simplex encephalitis (61.7 %) than herpes simplex encephalitis (HSE; 38.3 %) cases were recorded, with the majority concentrated in the southern USA (29.2 %). One-year inpatient mortality was 6.2 %, which over a 5-year period rose to 8.9 % for HSE and 5.8 % for all other viral encephalitides. HSE resulted in longer cumulative stays in the hospital (11 days vs. 4 days; P=0.0025), and accrued 37 % higher first-year costs, after adjusting for known confounders [P<0.001, cost ratio=1.37, 95 % confidence interval (1.20, 1.57)]. Additionally, HSE was associated with greater 5-year cumulative median charges ($125 338 vs. $82 317, P=0.0015).
Conclusion. The health economic impact and long-term morbidity of viral encephalitis in the USA are substantial.
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Unexpected predominance of rotavirus G9P[8] strain in Tunisian adult diarrheal patients
Introduction. Group A Rotavirus (RVA) is known to be a major cause of acute gastroenteritis (AGE) in children but its role as a potential pathogen in immunocompetent adults is probably underestimated.
Aim. To compare RVA infections in patients from different age groups.
Methodology. Fecal samples were collected from patients aged from birth to 65 years, hospitalized or consulting for AGE between 2015 and 2017. All samples were screened by RT-PCR for the detection of VP6 gene specific of RVA. RVA-positive samples were VP7 and VP4 genotyped using multiplex semi-nested RT-PCR. Full-length VP7 gene of G9-positive strains were sequenced and submitted for phylogenetic analysis.
Results. Of 1371 stool specimens collected from children (<5 years; n=454), older children (5 to <15 years; n=316) and adults (15-65 years; n=601), 165 (12.0 %) were RVA-positive. RVA detection rates were significantly higher in children and adults than in older children (15.8 % and 12.1 Vs 6.3 %, respectively; P<0.001). While RVA infections were mostly detected during the coldest months in children, they were observed all year-round in patients aged >5 years. Although G1P[8] remained the most prevalent combination (41.7 %) detected in children, G9P[8] strains widely predominated in adults (58.1 %), followed by G2P[4] (12.9 %). All characterized G9 strains clustered in the modern lineage III.
Conclusion. RVA play an important role in AGE not only in children but also in adults. The findings of a wide G9 predominance in patients >5 years highlights the need for continuing surveillance in both pediatric and mature populations.
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- Pathogenesis, Virulence and Host Response
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A mouse model of Staphylococcus aureus small intestinal infection
More LessIntroduction. Staphylococcus aureus is a recognised cause of foodborne intoxication and antibiotic-associated diarrhoea (AAD), which are both mediated by staphylococcal enterotoxins. However, unlike foodborne intoxication, AAD appears to require infection of the host. While S. aureus intoxication is widely studied, little is known about S. aureus pathogenesis in the context of gastrointestinal infection.
Aim. To develop a mouse model of S. aureus gastrointestinal infection.
Methodology. An established AAD mouse model was adapted for S. aureus infection, and damage observed via histopathological analysis and immunostaining of intestinal tissues.
Results. Various strains colonised the mouse model, and analysis showed that although clinical signs of disease were not seen, S. aureus infection induced damage in the small intestine, disrupting host structures essential for epithelial integrity. Studies using a staphylococcal enterotoxin B mutant showed that this toxin may contribute to damage during gastrointestinal infection.
Conclusion. This work presents a new mouse model of S. aureus gastrointestinal infection, while also providing insight into the pathogenesis of S. aureus in the gut.
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- Prevention, Therapy and Therapeutics
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Dental floss impregnated with povidone-iodine coated with Eudragit L-100 as an antimicrobial delivery system against periodontal-associated pathogens
More LessIntroduction. Periodontitis is among the most widespread oral bacterial diseases affecting 15-20% of the world population.
Aim. This study aimed to develop dental floss impregnated with povidone-iodine (PVP-I) as an antimicrobial delivery system against periodontopathogenic bacteria in a planktonic form and within biofilms.
Methods. Identical lengths of dental floss impregnated with PVP-I formulations were placed on agar along with previously grown periodontal pathogens. The bioactivity of the dental floss was investigated by response-surface methodology. In order to explore the antibacterial activity of the selected formulation and the potential application in the prevention and treatment of plaque-caused diseases such as periodontitis and caries, the antibacterial and anti-biofilm activity of the selected PVP-I formulation against pathogenic bacteria were investigated.
Results. The results indicated that the coating formulation containing Eudragit L-100 2.90 %, PVP-I 24.58 % and PEG 400 3.73 % had antimicrobial activity for all pathogens. The mechanism of this formulation involved disruption of bacterial cell membranes. Moreover, this formulation inhibited the formation of oral pathogenic biofilms.
Conclusion. It was concluded that Eudragit L-100 and PVP-I-coated dental floss represented a potential therapeutic agent to prevent periodontal diseases and dental caries and exhibited non-toxicity to periodontal ligament cells.
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Myoviridae phage PDX kills enteroaggregative Escherichia coli without human microbiome dysbiosis
Introduction. Bacteriophage therapy can be developed to target emerging diarrhoeal pathogens, but doing so in the absence of microbiome disruption, which occurs with antibiotic treatment, has not been established.
Aim. Identify a therapeutic bacteriophage that kills diarrhoeagenic enteroaggregative Escherichia coli (EAEC) while leaving the human microbiome intact.
Methodology. Phages from wastewater in Portland, OR, USA were screened for bacteriolytic activity by overlay assay. One isolated phage, PDX, was classified by electron microscopy and genome sequencing. A mouse model of infection determined whether the phage was therapeutic against EAEC. 16S metagenomic analysis of anaerobic cultures determined whether a normal human microbiome was altered by treatment.
Results. Escherichia virus PDX, a member of the strictly lytic family Myoviridae, killed a case-associated EAEC isolate from a child in rural Tennessee in a dose-dependent manner, and killed EAEC isolates from Columbian children. A single dose of PDX (multiplicity of infection: 100) 1 day post-infection reduced EAEC recovered from mouse faeces. PDX also killed EAEC when cultured anaerobically in the presence of human faecal bacteria. While the addition of EAEC reduced the β-diversity of the human microbiota, that of the cultures with either faeces alone, faeces with EAEC and PDX, or with just PDX phage was not different statistically.
Conclusion. PDX killed EAEC isolate EN1E-0007 in vivo and in vitro, while not altering the diversity of normal human microbiota in anaerobic culture, and thus could be part of an effective therapy for children in developing countries and those suffering from EAEC-mediated traveller’s diarrhoea without causing dysbiosis.
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