Access microbiology最新文献

A potentially new species of Streptomyces was isolated from station 177 of the Sundarbans Seasonal Time Series in the Indian Sundarbans mangrove. The isolate was cultured from a sediment sample on TYS medium of salinity 15. Sequencing and annotation of the 16S rRNA showed 100% identity against S. laurentii NPS17 against GenBank/ENA/DDBJ. Annotation of the whole genome against the GTDB database showed closest identity with S. terrae SKN60 and belongs to the same clade as S. roseicoloratus TRM44457T and S. laurentii ATCC 31255. The genome is ~7.2 Mb and has a G+C% of 73%. The average amino acid identity was 85.01% with S. roseicoloratus and 80.34% with S. roseolus. The assembly reflected the presence of all essential genes and had 19 biosynthetic gene clusters predicted.

Salmonella enterica serovar Typhi primarily persists in chronic carriers by forming biofilms on gallstones in the gallbladder. We have developed a gallstone mouse model to study chronic carriage. To better understand the infection timeline and differentiate between mice that have maintained long-term gallbladder carriage from those that have cleared infection, we utilized bioluminescent S. Typhimurium and in vivo imaging to detect and track the organ-specific presence of bacteria in living mice. The mice infected with our bioluminescent S. Typhimurium showed luminescence in the abdomen as early as 3 days in comparison to the mice infected with non-luminescent WT S. Typhimurium. With our methods, we achieve image resolution such that we can confidently identify the presence of S. Typhimurium in the gallbladder at >60 days post-infection. Using these methods, we have determined that the minimum number of bacteria necessary to detect luminescence in the mice is 10³ c.f.u. and that one out of six initially infected mice will remain persistently infected for greater than 60 days, with gallbladder bacterial loads reaching upwards of 10³ per milligram of tissue. Given that our limit of detection of luminescence is 10³ c.f.u., our sensitivity is robust enough to identify the bacterial loads present in the average chronically infected mouse. The quantification of individual organs' bacterial c.f.u. and comparison of luminescence between WT and luminescent S. Typhimurium validate that our technique is specific and sensitive enough to detect organ-specific infection in our model of typhoidal chronic carriage.

The use of membrane-specific dyes for in vivo fluorescent microscopy is commonplace. However, most of these reagents are non-specific and cannot track specific lipid species movement, instead often acting as non-covalent lipid-associated probes or requiring the uptake of whole lipids and acyl tails into the membrane. This issue has been solved in eukaryotic cell biology by the use of click-chemistry-liable phospholipid headgroup pulse labels. Here, we describe a method for in vivo phospholipid labelling by fluorescent imaging in Pseudomonas aeruginosa using a phosphatidylcholine mimic, 'propargyl-choline' (PCho). This click-chemistry-liable headgroup mimic is visible by microscopy and allows the covalent labelling of lipids. Fluorescence of the cell membranes, visible in heterogeneous patches, is dependent on PCho concentration and is localized in the membrane fraction of cells, demonstrating that it is suitable for membrane labelling and cell imaging.

Our study aimed to identify the bacterial source of a previously detected mobile antibiotic-resistant gene, mecA, found in a lake that serves as a source to a water treatment plant operated by a First Nation reserve. Three methicillin-resistant presumptive Staphylococcus spp. isolated from the sample using selective media were verified as mecA positive by PCR. MALDI-TOF and whole-genome sequencing of each isolate confirmed that all three were Mammaliicoccus fleurettii. Antibiotic-resistant gene analysis of the assembled genomes predicted mecA with 99.7% sequence identity, and phylogenetic analysis grouped our three mecA genes with the mecA allele from a methicillin-resistant strain of Staphylococcus aureus. Identifying microbial species known to harbour mobile antibiotic-resistant elements can provide greater depth of information about drinking water, an especially essential need in First Nation reserves where water quality too frequently is poor.

In the European region, diphtheria is now rarely suspected in patients presenting with upper respiratory tract symptoms. Corynebacterium ulcerans is the underestimated zoonosis that is replacing C. diphtheria infections in industrialized countries, but extensive human and animal prevalence studies are lacking. The range of hosts that can act as reservoirs for C. ulcerans is very broad, companion pets currently being the main source of human infection. We report a case of macrolide-resistant C. ulcerans infection with no apparent zoonotic transmission and outline the efforts required for the public and zooprophylactic management of these cases. We describe the main critical issues to be addressed to comprehensively tackle this zoonosis in the future.

Antimicrobial-resistant pathogens such as Pseudomonas aeruginosa and Acinetobacter baumannii can cause potentially fatal infections in susceptible individuals, with respiratory tract infections among the most common clinical presentations. The development of novel treatments or prophylactic interventions to combat these infections is urgently needed and requires robust, reliable animal models for their preclinical evaluation. In particular, the bacterial burden needs to be accurately determined before and after administration of the potential therapy under evaluation to quantify the effectiveness of the treatment. We provide two reliable, non-invasive murine acute lung challenge models with either P. aeruginosa or A. baumannii using an oropharyngeal aspiration technique, which has been widely overlooked in studies testing vaccines or treatments for these pathogens. Here, we show that this non-surgical technique to deliver suspensions into mouse lungs does not significantly impact animal welfare (based on welfare monitoring and weight) and allows uniform bilateral distribution of the bacterial dose, resulting in even bioburden in both lungs. The optimal timepoint for humane killing and organ harvest was 24 h after challenge for both pathogens, and at least 4×10⁶ and 10⁷ c.f.u. per mouse were needed to obtain a reproducible P. aeruginosa or A. baumannii bioburden, respectively. These mouse challenge models offer a valuable tool to assess therapeutic interventions against P. aeruginosa or A. baumannii infections.

Health authorities were notified of a suspected outbreak of foodborne disease in a hospital in South Africa, where staff and patients reported acute onset of abdominal cramps, diarrhoea, fever and rigours after eating a chicken pasta meal. The aim of this report is to discuss the use of whole genome sequencing (WGS) analysis of bacterial isolates to support an epidemiological investigation. An epidemiological investigation led by the Infection Control Manager of the hospital and supported by an outbreak response team was conducted. Standard microbiological procedures were used to process stool samples and culture/identify diarrhoeal pathogens. Bacterial cultures were investigated using WGS performed using Illumina NextSeq technology, and WGS data were analysed using multiple bioinformatics tools, including those available at the Center for Genomic Epidemiology and EnteroBase. Core genome multilocus sequence typing (cgMLST) was used to investigate the phylogeny of isolates. Forty-nine cases were identified, with stool samples collected from 21 cases, and nontyphoidal Salmonella isolated from 19 out of 21 (90%) of the samples. All isolates were identified as Salmonella enterica serovar Enteritidis and differed from each other by ≤2 allele differences on cgMLST, indicating that isolates are highly genetically related. Delays in testing of food retention samples rendered the negative test results of limited value. A case-control study was conducted; eating chicken pasta was strongly associated with developing gastroenteritis (Odds Ration (OR) = 15.4, Chi-Square test with Yates correction p value = 0.02). The epidemiological evidence suggests that the chicken pasta was the likely vehicle of transmission in this outbreak, although the source of S. enterica serovar Enteritidis remains unknown.

We announce the deposition of the first two enterotoxigenic Escherichia coli (ETEC) genomes from Malawi. They were isolated from the faeces of asymptomatically infected children obtained in 2014. Both genomes encode the porcine variant of the heat-labile toxin and no known ETEC colonization factors.

Background. According to the World Health Organization, neglected tropical diseases (NTDs) affect over two billion people worldwide. While the links between nutrition and many diseases have become clear over recent decades, NTDs have lagged behind and the linkage with nutrition is largely unknown. We conducted this systematic review with meta-analysis to determine the current knowledge on the association between NTDs and malnutrition. Methodology. PubMed, Embase, Scopus and African Journals Online databases were searched using predefined search terms. We included all original articles with a case-control design and at least one NTD. The studies had to compare nutritional parameters between infected cases and control participants. Articles that did not report original data were excluded. The quality of the studies was assessed using the Newcastle-Ottawa scale. Pooled estimates were conducted using the random effect model. The publication bias of the studies was determined by funnel plots. Q and I ² statistics were used to assess the heterogeneity of the studies. Results. After screening 1294 articles, only 16 qualified for the systematic review and 12 for meta-analysis. These predominately had a focus on soil-transmitted helminthiasis (ascariasis, hookworm diseases and trichuriasis) and schistosomiasis, with a minority concerning leishmaniasis and leprosy. Pooled estimates showed an association between intestinal parasites and stunting in children [odds ratio (OR) = 1.38, 95% confidence interval (CI): 1.14-1.66, I ² = 0%, tau² = 0]. We also identified a moderate association established between serum iron deficiency (OR = 4.67, 95% CI: 1.91-11.44, tau² = 0) and intestinal parasites. Conclusions/significance. Of the 20 NTDs, the links between diet and disease have been explored for only 4. There is a paucity of data from low- and middle-income countries and least-developed countries where the NTD burden is high. Therefore, more research into the role of malnutrition in NTDs other than intestinal parasites, leishmaniasis and leprosy is needed.

The Tol-Pal proteins stabilize the outer membrane during cell division in many Gram-negative bacteria, including Escherichia coli. Pal is an outer membrane lipoprotein that can bind peptidoglycan. It accumulates at the septum during division by a mobilization-and-capture mechanism. This work further substantiates and extends knowledge of Pal's localization in E. coli using immunolabelling; this method enables the detection of endogenous proteins. The midcell localization of Pal and TolB, as seen with fluorescent protein fusions, during cell division, was confirmed. The retention of Pal in newly formed cell poles seemed to persist longer than observed with fluorescent Pal fusions. The concentration of endogenous Pal during the cell division cycle fluctuated: it decreased initially (to half the fluorescence concentration (32.1 au µm^-3) of the maximum (64.1 au µm^-3) reached during the cell cycle) and then increased during the second half of the cell division cycle. We probed for possible regulators and proposed two new putative regulators of Pal. By deleting the periplasmic protease, Prc decreased the total Pal abundance (to ~65% of the fluorescence concentration in WT cells) and affected its concentration fluctuation during the cell cycle. This suggests that Prc controls a cell division stage-specific regulator of Pal. Immunolabelling also supported the prediction that the small RNA MicA suppresses Pal expression (the fluorescence concentration of Pal in cells without MicA is double that of Pal in WT cells). However, the regulation by MicA occurred in a cell cycle-independent manner. All these findings urge further research on the tight regulation of the dividing cell envelope stability.