- Volume 70, Issue 9, 2021
Volume 70, Issue 9, 2021
- Letters
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- Reviews
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Disinfection to control African swine fever virus: a UK perspective
More LessA review of African swine fever (ASF) was conducted, including manifestations of disease, its transmission and environmental persistence of ASF virus. Findings on infectious doses of contemporary highly-pathogenic strains isolated from outbreaks in Eastern Europe were included. Published data on disinfectant susceptibility of ASF virus were then compared with similar findings for selected other infectious agents, principally those used in the UK disinfectant approvals tests relating to relevant Disease Orders for the control of notifiable and zoonotic diseases of livestock. These are: swine vesicular disease virus, foot and mouth disease virus, Newcastle disease virus and Salmonella enterica serovar Enteritidis. The comparative data thus obtained, presented in a series of charts, facilitated estimates of efficacy against ASF virus for some UK approved disinfectants when applied at their respective General Orders concentrations. Substantial data gaps were encountered for several disinfectant agents or classes, including peracetic acid, quaternary ammonium compounds and products based on phenols and cresols.
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- JMM Profiles
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JMM Profile: Vibrio cholerae: an opportunist of human crises
More LessVibrio cholerae O1 is the aetiological agent of the severe diarrhoeal disease cholera. Annually, there are an estimated 1–4 million cholera cases worldwide and over 140 000 deaths. The primary mode of disease transmission is through the consumption of water or food contaminated with the bacterium. Although cholera patients can be treated effectively using rehydration therapy, the disease remains a major scourge in areas with limited access to clean water and proper sanitation. Its continued prevalence highlights the failure of socioeconomic policies leading to wealth disparities, fragile and dated public infrastructure, and lack of appropriate health surveillance.
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- Antimicrobial Resistance
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In vitro antifungal effect of a plant-based product, CIN-102, on antifungal resistant filamentous fungi and their biofilms
Introduction. The increase of invasive fungal infections (IFIs) and associated treatment failure in populations at risk is driving us to look for new treatments.
Hypothesis. The CIN-102 compound, derived from cinnamon essential oil, could be a new antifungal class with an activity, in particular, on strains resistant to current antifungals but also on biofilms, a factor of virulence and resistance of fungi.
Aim. The aim of this study is to show the activity of CIN-102 on various strains resistant to current antifungals, on the biofilm and to determine the possibility of resistance induced with this compound.
Methodology. We studied the MIC of CIN-102 and of current antifungals (voriconazole and amphotericin B) using CLSI techniques against eight different strains of three genera of filamentous fungi involved in IFIs and having resistance phenotypes to current antifungals. We also determined their effects on biofilm formation, and the induced resistance by voriconazole (VRC) and CIN-102.
Results. MIC values determined for CIN-102 were between 62.5 and 250 µg ml−1. We demonstrated the antifungal effect of CIN-102 on biofilm, and more particularly on its formation, with 100 % inhibition achieved for most of the strains. CIN-102 at a sub-inhibitory concentration in the medium did not induce resistance in our strains, even after 30 generations.
Conclusions. In this study we show that CIN-102 is effective against resistant filamentous fungi and against biofilm formation. In addition, our strains did not acquire a resistance phenotype against CIN-102 over time, unlike with VRC. CIN-102 is therefore an interesting candidate for the treatment of IFIs, including in cases of therapeutic failure linked to resistance, although further studies on its efficacy, safety and mechanism of action are needed.
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Molecular characterization of rectal isolates of carbapenemase-negative carbapenem-resistant enterobacterales obtained from ICU patients in Kuwait by whole-genome sequencing
More LessIntroduction. Carbapenem-resistant enterobacterales (CRE) are listed among the most urgent antibiotic resistance threats.
Hypothesis. Previous studies on the mechanisms of CRE in Kuwait have focused on carbapenemases. There have been no studies on non-carbapenemase-producing CRE in Kuwait.
Aim/Gap Statement. The aim of this study was to investigate the genetic characteristics of non-carbapenemase-producing carbapenem-resistant enterobacterales (NCPE) isolates using whole-genome sequencing (WGS).
Methodology. Fourteen confirmed NCPE isolates that were negative for genes encoding carbapenemase production by polymerase chain reaction (PCR) assays using rectal swabs from intensive care unit patients were characterized using phenotypic, PCR and WGS methods. Susceptibility testing was performed via Etest and clonality via multi-locus sequence typing (MLST).
Results. All of the isolates were resistant to ertapenem; 78.6 % were resistant to imipenem, meropenem and trimethoprim–sulfamethoxazole. Resistance to the other antibiotics was variable, ranging from 28.5 (colistin) through 50 (tigecycline) and 64.3 (amikacin) up to 85.7 % against both amoxicillin–clavulanic acid and ciprofloxacin. WGS detected several resistance genes mediating the production of β-lactamases, genes encoding an outer-membrane porin permeability mutation resulting in reduced susceptibility to β-lactams, including carbapenems, and genes for multidrug-resistant (MDR) efflux pumps. The isolates also possessed global activator protein MarA, which mediated reduced permeability to β-lactams. The existence of β-lactamase genes, overexpression of MDR efflux pumps and reduced permeability mediated by the porin genes were responsible for carbapenem resistance.
Conclusions. This finding reflects the superior detection capabilities offered by WGS analysis, which can be used to complement traditional methods and overcome their limited resolution in clinical settings.
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Sickle cell disease children’s gut colonization by extended-spectrum β-lactamase (ESBL)-producing Enterobacterales: an antibiotic prophylaxis effect?
Introduction. Sickle cell disease (SCD) children have a high susceptibility to pneumococcal infection. For this reason, they are routinely immunized with pneumococcal vaccines and use antibiotic prophylaxis (AP).
Hypothesis/Gap Statement. Yet, little is known about SCD children’s gut microbiota. If antibiotic-resistant Enterobacterales may colonize people on AP, we hypothesized that SCD children on AP are colonized by resistant enterobacteria species.
Objective. To evaluate the effect of continuous AP on Enterobacterales gut colonization from children with SCD.
Methodology. We analysed 30 faecal swabs from SCD children on AP and 21 swabs from children without the same condition. Enterobacterales was isolated on MacConkey agar plates and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) (bioMérieux, Marcy l'Etoile, France). We performed the antibiogram by Vitek 2 system (bioMérieux, Marcy l'Etoile, France), and the resistance genes were identified by multiplex PCR.
Results. We found four different species with resistance to one or more different antibiotic types in the AP-SCD children’s group: Escherichia coli , Klebsiella pneumoniae , Citrobacter freundii , and Citrobacter farmeri . Colonization by resistant E. coli was associated with AP (prevalence ratio 2.69, 95 % confidence interval [CI], 1.98–3.67, P<0.001). Strains producing extended-spectrum β-lactamases (ESBL) were identified only in SCD children, E. coli , 4/30 (13 %), and K. pneumoniae , 2/30 (7 %). The ESBL-producing Enterobacterales were associated with penicillin G benzathine use (95 % CI, 22.91–86.71, P<0.001). CTX-M-1 was the most prevalent among ESBL-producers (3/6, 50 %), followed by CTX-M-9 (2/6, 33 %), and CTX-M-2 (1/6, 17 %).
Conclusion. Resistant enterobacteria colonize SCD children on AP, and this therapy raises the chance of ESBL-producing Enterobacterales colonization. Future studies should focus on prophylactic vaccines as exclusive therapy against pneumococcal infections.
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In vitro activity of dalbavancin and other anti-staphylococcal agents against infecting isolates of methicillin-resistant coagulase-negative staphylococci
Introduction. Dalbavancin was approved in Europe in 2015 for skin and soft tissue infections.
Hypothesis/Gap Statement. Data on methicillin-resistant coagulase-negative staphylococci (MR-CNS) dalbavancin susceptibility are scarce.
Aim. To assess the susceptibility of MR-CNS to dalbavancin and other anti-staphylococcal agents.
Methodology. A total of 443 MR-CNS clinical isolates from patients hospitalized in a Greek university hospital during a 2.5-year period (January 2018 to June 2020) were included. The MICs for vancomycin, teicoplanin, linezolid and daptomycin were investigated by Etest and the MIC for dalbavancin was determined according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines in 196 isolates. The consumption of the aforementioned antimicrobials was calculated.
Results. In total, 51 isolates were resistant to teicoplanin (11.5 %) and 211 (47.6 %) to linezolid; all were susceptible to vancomycin and daptomycin. Among 196 isolates tested, 32 (16.3 %) were resistant to dalbavancin. A significant increase of MIC during the study period was found for vancomycin, teicoplanin and daptomycin, while a decrease in linezolid’s MIC was observed. Dalbavancin’s MIC remained stable. No difference in consumption was observed among the studied anti-staphylococcal agents.
Conclusion. An increase of vancomycin, teicoplanin and daptomycin MICs among MR-CNS was observed, whereas 47.6 % of isolates were non-susceptible to linezolid. Dalbavancin retains excellent potency against MR-CNS, even in the presence of non-susceptibility to other anti-staphylococcal antibiotics.
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Analysis of the antimicrobial resistance gene frequency in whole-genome sequenced Vibrio from Latin American countries
More LessVibrio species are important environmental-related bacteria responsible for diverse infections in humans due to consumption of contaminated water and seafood in underdeveloped areas of the world. This study aimed to investigate the frequency of antimicrobial resistance genes in 577 sequenced Vibrio cholerae, Vibrio parahaemolyticus and Vibrio vulnificus strains isolated in Latin American countries available at the NCBI Pathogen Detection database and to determine the sequence type (ST) of the strains. Almost all strains studied (99.8%) carried at least one antimicrobial resistance gene, while 54.2 % presented a multidrug-resistance profile. The Vibrio strains exhibited genotypic resistance to 11 antimicrobial classes and almG, varG, and catB9, which confer resistance to antibiotic peptides, β-lactams and amphenicols, respectively, were the most detected genes. Vibrio parahaemolyticus and V. vulnificus showed a broad diversity of STs. Vibrio cholerae strains isolated in Haiti after 2010’s earthquake presented the highest diversity and amount of resistance genes in the set of strains analysed and mostly belonged to ST69. In conclusion, the detection of resistance genes from 11 antimicrobial classes and the high number of multidrug-resistant Vibrio species strains emphasize that Latin American public health authorities should employ more efficient control measures and that special attention should be given for the rational use of antimicrobials in human therapy and aquaculture, since the consumption of contaminated water and seafood with resistant Vibrio may result in human infections difficult to be treated.
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Prevalence of Mycoplasma genitalium fluoroquinolone-resistance markers, and dual-class-resistance markers, in asymptomatic men who have sex with men
Introduction. Failure of fluoroquinolones, the principal treatment option for macrolide-resistant Mycoplasma genitalium infections, has recently emerged. This is of particular concern for men who have sex with men (MSM), who have high proportions of macrolide-resistant M. genitalium infections. Treatment failure with moxifloxacin is likely the result of single nucleotide polymorphisms (SNPs) in parC, whilst concurrent gyrA mutations may play a role.
Gap Statement. The levels of fluoroquinolone resistance and dual-class (i.e. macrolide and fluoroquinolone) resistance in M. genitalium among asymptomatic MSM is unknown.
Aim. To (i) determine the proportion of fluoroquinolone resistance and dual-class resistance in M. genitalium infections among asymptomatic MSM, (ii) explore any clinical and behavioural associations with fluoroquinolone resistance, and (iii) determine the distribution of antibiotic resistance among M. genitalium mgpB sequence types (STs).
Methodology. M. genitalium positive samples (N=94) were obtained from 1001 asymptomatic MSM enrolled in a study at Melbourne Sexual Health Centre (Carlton, Australia) between August 2016 and September 2017. Sanger sequencing was performed to determine the proportion of M. genitalium infections with SNPs in parC that have previously been associated with failure of moxifloxacin (corresponding to amino changes S83I, D83R, D87Y and D87N) and in gyrA (corresponding to amino acid changes M95I, D99N, D99Y and D99G). Associations between clinical/behavioural factors and parC SNPs were examined. Strain typing was performed by sequencing a portion of the mgpB gene.
Results. The proportion of MSM with infections harbouring parC and gyrA SNPs was 13.0 % [95 % confidence interval (CI): 6.8–23.2 %] and 4.7 % (95 % CI: 1.1–13.4 %), respectively; dual-class resistance was 13.0 %. No significant clinical/behavioural associations were found. Antibiotic resistance was not restricted to specific mgpB STs.
Conclusion. One in eight (13 %) of asymptomatic MSM with M. genitalium had an infection with dual-class-resistance mutations. Typing by mgpB sequence suggested fluoroquinolone resistance is arising from independent mutation events. This study illustrates that asymptomatic MSM may act as a reservoir for antibiotic-resistant M. genitalium .
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- Clinical Microbiology
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Sample collection and transport strategies to enhance yield, accessibility, and biosafety of COVID-19 RT-PCR testing
Introduction. Non-invasive sample collection and viral sterilizing buffers have independently enabled workflows for more widespread COVID-19 testing by reverse-transcriptase polymerase chain reaction (RT-PCR).
Gap statement. The combined use of sterilizing buffers across non-invasive sample types to optimize sensitive, accessible, and biosafe sampling methods has not been directly and systematically compared.
Aim. We aimed to evaluate diagnostic yield across different non-invasive samples with standard viral transport media (VTM) versus a sterilizing buffer eNAT- (Copan diagnostics Murrieta, CA) in a point-of-care diagnostic assay system.
Methods. We prospectively collected 84 sets of nasal swabs, oral swabs, and saliva, from 52 COVID-19 RT-PCR-confirmed patients, and nasopharyngeal (NP) swabs from 37 patients. Nasal swabs, oral swabs, and saliva were placed in either VTM or eNAT, prior to testing with the Xpert Xpress SARS-CoV-2 (Xpert). The sensitivity of each sampling strategy was compared using a composite positive standard.
Results. Swab specimens collected in eNAT showed an overall superior sensitivity compared to swabs in VTM (70 % vs 57 %, P=0.0022). Direct saliva 90.5 %, (95 % CI: 82 %, 95 %), followed by NP swabs in VTM and saliva in eNAT, was significantly more sensitive than nasal swabs in VTM (50 %, P<0.001) or eNAT (67.8 %, P=0.0012) and oral swabs in VTM (50 %, P<0.0001) or eNAT (58 %, P<0.0001). Saliva and use of eNAT buffer each increased detection of SARS-CoV-2 with the Xpert; however, no single sample matrix identified all positive cases.
Conclusion. Saliva and eNAT sterilizing buffer can enhance safe and sensitive detection of COVID-19 using point-of-care GeneXpert instruments.
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Adult gonococcal conjunctivitis: Prevalence, clinical features and complications
Introduction. Gonorrhoea is a sexually transmitted disease whose incidence has increased in recent years and adult gonococcal conjunctivitis (AGC) is a relatively uncommon complication.
Hypothesis/Gap Statement. AGC is associated with increased incidence of genital gonorrhoea and must be treated correctly to avoid serious corneal complications.
Aims. To report the prevalence, clinical features, and complications of AGC in a tertiary ophthalmology centre in Barcelona, Spain. Present epidemiological data, clinical features, ocular complications, and antibiotic susceptibility. Design: Single-centre, descriptive, retrospective case series.
Methodology. Systematic case-defined search in medical records and further retrospective chart review study of microbiologically confirmed AGC attending outpatient clinic and/or emergency room from 2012 to 2020. We analysed the clinical presentation, treatments, antibiotic susceptibility, complications and ocular sequelae.
Results. Thirteen patients were diagnosed of AGC. Eleven patients had unilateral presentation. Two patients had bilateral presentation. In ten cases there was abundant mucopurulent discharge, three cases presented periocular pain and periocular inflammation requiring a CT scan to rule out post-septal cellulitis. The diagnosis was confirmed by culture. In total, 100 % of strains were susceptible to ceftriaxone, 58 % were ciprofloxacin resistant and no beta-lactamase production was detected. Three patients required hospital admission. One patient developed a complication presenting with ptosis caused by superior symblepharon.
Conclusion. AGC is a rare disease which is difficult to diagnose as it requires a high index of suspicion to prevent corneal perforation but in an important number of cases it may mimic orbital cellulitis. It is crucial that treatment starts as soon as possible to avoid serious corneal damage. Patients should promptly receive complete and correct treatment when admitted to the emergency room since an elevated number of patients do not attend their medical follow-up visit. Azithromycin or aminoglycoside eye drops are probably the best option to complete the treatment, due to high quinolone resistance.
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- Disease, Diagnosis and Diagnostics
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Improved diagnosis of gastrointestinal infections using a semi-automated multiplex real-time PCR for detection of enteropathogens
Berta Fidalgo, Elisa Rubio, Victor Pastor, Marta Parera, Clara Ballesté-Delpierre, Mariana José Fernández, Genoveva Cuesta Chasco, Andrea Vergara, Yuliya Zboromyrska, Cristian Aylagas, Pilar Salvador, Adán Fernández, M. Eugenia Valls, Míriam José Alvarez Martinez, Aurea Mira, Maria Angeles Marcos, Jordi Vila, Miguel J. Martinez and Climent Casals-PascualIntroduction. The identification of enteropathogens is critical for the clinical management of patients with suspected gastrointestinal infection. The FLOW multiplex PCR system (FMPS) is a semi-automated platform (FLOW System, Roche) for multiplex real-time PCR analysis.
Hypothesis/Gap Statement. FMPS has greater sensitivity for the detection of enteric pathogens than standard methods such as culture, biochemical identification, immunochromatography or microscopic examination.
Aim.The diagnostic performance of the FMPS was evaluated and compared to that of traditional microbiological procedures.
Methodology. A total of 10 659 samples were collected and analysed over a period of 7 years. From 2013 to 2018 (every July to September), samples were processed using standard microbiological culture methods. In 2019, the FMPS was implemented using real-time PCR to detect the following enteropathogens: Shigella spp., Salmonella spp., Campylobacter spp., Giardia intestinalis, Entamoeba histolytica, Blastocystis hominis, Cryptosporidum spp., Dientamoeba fragilis, adenovirus, norovirus and rotavirus. Standard microbiological culture methods (2013–2018) included stool culture, microscopy and immunochromatography.
Results. A total of 1078 stool samples were analysed prospectively using the FMPS from July to September (2019): bacterial, parasitic and viral pathogens were identified in 15.3, 9.71 and 5.29 % of cases, respectively. During the same period of 6 years (2013–2018), the proportion of positive identifications using standard microbiological methods from 2013 to 2018 was significantly lower. A major significant recovery improvement was observed for all bacteria species tested: Shigella spp./enteroinvasive Escherichia coli (EIEC) (P <0.05), Salmonella spp. (P <0.05) and Campylobacter spp. (P <0.05). Marked differences were also observed for the parasites G. intestinalis, Cryptosporidium spp. and D. fragilis.
Conclusion. These results support the value of multiplex real-time PCR analysis for the detection of enteric pathogens in laboratory diagnosis with outstanding performance in identifying labile micro-organisms. The identification of unsuspected micro-organisms for less specific clinical presentations may also impact on clinical practice and help optimize patient management.
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Prototheca bovis, a unicellular achlorophyllous trebouxiophyte green alga in the healthy human intestine
Introduction. Prototheca species are non-photosynthetic trebouxiophyte algae ubiquitously distributed in nature and can be found in sewage and soil. This microbial eukaryote causes human protothecosis in immunocompromised individuals. Thus, Prototheca presence in the stool of individuals without gastrointestinal symptoms has been reported only rarely.
Hypothesis/Gap statement. There is an absence of detailed characterization of human Prototheca isolates.
Aim. The aim of this study was to perform morphological and molecular characterization of Prototheca isolates obtained from human stool.
Methodology. Prototheca was isolated from faecal samples of four individuals living in a rural area in Thailand. A combination of bioimaging along with molecular and bioinformatics tools was used to characterize the four strains. The growth rate was tested using four media and three temperature conditions. Phylogenetic analysis using the small subunit ribosomal RNA (SSU rRNA) and cytochrome b (cytb) was also performed.
Results. Static and live microscopy demonstrated the various life stages of Prototheca and its major defining cellular characteristics. An optimized DNA extraction methodology that improves DNA yield is provided. Partial fragments of the SSU rRNA and cytb genes were obtained. Phylogenetic analysis placed all four strains in the clade with Prototheca bovis. More broadly, Prototheca was not monophyletic but split into at least two distinct clades instead.
Conclusion. The results represent the first molecular characterization of Prototheca in Thailand. The study provides insight into transmission dynamics of the organism and potential caveats in estimating the global prevalence of Prototheca. These will spearhead further investigations on Prototheca occurrence in rural areas of both industrialized and developing nations.
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Group B streptococcal infections in infants in Iceland: clinical and microbiological factors
Introduction. Group B streptococcus (GBS) is a leading cause of invasive neonatal infections. These have been divided into early-onset disease (EOD; <7 days) and late-onset disease (LOD; 7–89 days), with different GBS clonal complexes (CCs) associated with different disease presentations.
Hypothesis. Different GBS CCs are associated with timing of infection (EOD or LOD) and clinical presentation (sepsis, meningitis or pneumonia).
Aim. To study infant GBS infections in Iceland from 1975 to 2019. Are specific GBS CCs related to disease presentation? Is CC17 overrepresented in infant GBS infections in Iceland?
Methodology. All culture-confirmed invasive GBS infections in infants (<90 days) in Iceland from 1975 to 2019 were included. Clinical information was gathered from medical records.
Results. A total of 127 invasive GBS infections in infants were diagnosed, but 105 infants were included in the study. Of these, 56 had EOD and 49 had LOD. The incidence of GBS infections declined from 2000 onwards but increased again at the end of the study period. Furthermore, there was a significant increase in LOD over the study period (P=0.0001). The most common presenting symptoms were respiratory difficulties and fever and the most common presentation was sepsis alone. Approximately one-third of the cases were caused by GBS CC17 of serotype III with surface protein RIB and pili PI-1+PI-2b or PI-2b. CC17 was significantly associated with LOD (P<0.001).
Conclusion. CC17 is a major cause of GBS infection in infants in Iceland. This clone is associated with LOD, which has been increasing in incidence. Because intrapartum antibiotic prophylaxis only prevents EOD, it is important to continue the development of a GBS vaccine in order to prevent LOD infections.
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- Microbiome and Microbial Ecology in Health
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Identification & correlation of bacterial diversity in oral cancer and long-term tobacco chewers- A case-control pilot study
More LessIntroduction. Squamous cell carcinoma is a highly aggressive type of oral cancer (OC). It is the most common cancer among men, and accounts for almost 90 % of all oral cancers in India. Consumption of tobacco is a leading factor contributing to maximum oral cancer incidences as per the WHO.
Hypothesis/Gap statement. Researchers reported a direct association of microorganisms with dysbiosis in various oral lesions including oral cancer. However, there is a dearth of information related to compositional changes in the oral microbiome in long-term tobacco chewers and the Indian oral cancer population.
Aim. The aim of this study was to identify and correlate the bacterial diversity in the oral cavity of tobacco chewers, patients with oral cancer and healthy subjects in the Indian population.
Methods. Oral rinse samples were collected for ten subjects in each group followed by DNA extraction. The variable regions of the bacterial 16S rRNA gene (V6-V8) were amplified, sequenced, processed, and analysed using QIIME2 platform to assess alpha and beta diversity between the study groups.
Results. This pilot study showed genus Streptococcus dominated the control group (18.54 %), and the abundance decreased in tobacco and OC group (9.63 and 5.45% respectively); whereas genus Prevotella dominated the tobacco and OC group (21.01 and 26.03% respectively). A shift in abundance of microbiome was observed from control population to oral cancer via the tobacco chewing population. Maximum alpha diversity of oral microbiome was found in Indian tobacco chewers. Beta diversity of tobacco chewers was similar to both the healthy population as well as oral cancer patients suggesting transitioning of the oral microbiome from healthy to oral cancer microbiome via the tobacco chewers microbiome.
Conclusion. The data provides evidence of oral bacterial dysbiosis due to tobacco chewing habits that can further lead to progression towards cancer.
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Impact of pH on growth of Staphylococcus epidermidis and Staphylococcus aureus in vitro
More LessThe pH of skin is critical for skin health and resilience and plays a key role in controlling the skin microbiome. It has been well reported that under dysbiotic conditions such as atopic dermatitis (AD), eczema, etc. there are significant aberrations of skin pH, along with a higher level of Staphylococcus aureus compared to the commensal Staphylococcus epidermidis on skin. To understand the effect of pH on the relative growth of S. epidermidis and S. aureus , we carried out simple in vitro growth kinetic studies of the individual microbes under varying pH conditions. We demonstrated that the growth kinetics of S. epidermidis is relatively insensitive to pH within the range of 5–7, while S. aureus shows a stronger pH dependence in that range. Gompertz’s model was used to fit the pH dependence of the growth kinetics of the two bacteria and showed that the equilibrium bacterial count of S. aureus was the more sensitive parameter. The switch in growth rate happens at a pH of 6.5–7. Our studies are in line with the general hypothesis that keeping the skin pH within an acidic range is advantageous in terms of keeping the skin microbiome in balance and maintaining healthy skin.
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- Molecular and Microbial Epidemiology
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Absence of SARS-CoV-2 in the air and on the surfaces within the school environment
More LessTo the best of our knowledge to date there are no scientific studies specifically investigating whether the SARS-CoV-2 virus is present in the air or on the various surfaces in the school environment. The aim of this study was to determine if SARS-CoV-2 is present on various high touch surfaces and in the air across the elementary, middle and high schools in the Chester County of Pennsylvania, USA. One hundred and fifty surface swab samples and 45 air samples were analysed for the presence of the virus. All the samples tested were negative for the presence of SARS-CoV-2. The results indicate that the spread of the virus through contact and through air in the school buildings across the USA is highly unlikely.
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- One Health ‒ Emerging, Zoonotic and Environmental Diseases
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Challenges on the development of a pseudotyping assay for Zika glycoproteins
Introduction. Zika virus (ZIKV) emerged as a public health concern on the American continent during late 2015. As the number of infected grew so did the concerns about its capability to cause long-term damage especially with the appearance of the congenital Zika syndrome (CZS). Proteins from the TAM family of receptor tyrosine kinases (RTKs) were proposed as the cellular receptors, however, due to the ability of the virus to infect a variety of cell lines different strategies to elucidate the tropism of the virus should be investigated.
Hypothesis. Pseudotyping is a powerful tool to interrogate the ability of the glycoprotein (GP) to permit entry of viruses.
Aim. We aimed to establish a highly tractable pseudotype model using lenti- and retro-viral backbones to investigate the entry pathway of ZIKV.
Methodology. We used different glycoprotein constructs and different lenti- or retro-viral backbones, in a matrix of ratios to investigate production of proteins and functional pseudotypes.
Results. Varying the ratio of backbone and glycoprotein plasmids did not yield infectious pseudotypes. Moreover, the supplementation of the ZIKV protease or the substitution of the backbone had no positive impact on the infectivity. We showed production of the proteins in producer cells implying the lack of infectious pseudotypes is due to a lack of successful glycoprotein incorporation, rather than lack of protein production.
Conclusion. In line with other reports, we were unable to successfully produce infectious pseudotypes using the variety of methods described. Other strategies may be more suitable in the development of an efficient pseudotype model for ZIKV and other flaviviruses.
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- Pathogenesis, Virulence and Host Response
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The S. Typhi leuO gene contains multiple functional promoters
The S. Typhi leuO gene, which codes for the LysR-type transcriptional regulator LeuO, contains five forward promoters named P3, P1, P2, P5 and P4, and two reverse promoters, P6 and P7. The activity of the forward promoters was revealed by primer extension using gene reporter fusions in an S. Typhi hns lrp mutant strain. Likewise, the activity of the reverse promoters was revealed in an hns background. Derepression of the transcription of the chromosomal gene was confirmed by RT-PCR in the hns lrp mutant. The leuOP1 transcriptional reporter fusion, which contained only the major P1 promoter, had a lower expression in a relA spoT mutant strain, indicating that the steady-state levels of the (p)ppGpp alarmone positively regulate it. In contrast, the leuOP3, leuOP5P4, leuOP6 and leuOP7 transcriptional fusions were derepressed in the relA spoT background, indicating that the alarmone has a negative effect on their expression. Thus, the search for genetic regulators and environmental cues that would differentially derepress leuO gene expression by antagonizing the action of the H-NS and Lrp nucleoid-associated proteins, or that would fine-tune the expression of the various promoters, will further our understanding of the significance that multiple promoters have in the control of LeuO expression.
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Volumes and issues
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Volume 73 (2024)
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Volume 72 (2023 - 2024)
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Volume 71 (2022)
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Volume 70 (2021)
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Volume 69 (2020)
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Volume 68 (2019)
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Volume 67 (2018)
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Volume 66 (2017)
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Volume 65 (2016)
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