Preparation of a Blood Culture Pellet for Rapid Bacterial Identification and Antibiotic Susceptibility Testing

Bloodstream infections and sepsis are a major cause of morbidity and mortality. The successful outcome of patients suffering from bacteremia depends on a rapid identification of the infectious agent to guide optimal antibiotic treatment. The analysis of Gram stains from positive blood culture can be rapidly conducted and already significantly impact the antibiotic regimen. However, the accurate identification of the infectious agent is still required to establish the optimal targeted treatment. We present here a simple and fast bacterial pellet preparation from a positive blood culture that can be used as a sample for several essential downstream applications such as identification by MALDI-TOF MS, antibiotic susceptibility testing (AST) by disc diffusion assay or automated AST systems and by automated PCR-based diagnostic testing. The performance of these different identification and AST systems applied directly on the blood culture bacterial pellets is very similar to the performance normally obtained from isolated colonies grown on agar plates. Compared to conventional approaches, the rapid acquisition of a bacterial pellet significantly reduces the time to report both identification and AST. Thus, following blood culture positivity, identification by MALDI-TOF can be reported within less than 1 hr whereas results of AST by automated AST systems or disc diffusion assays within 8 to 18 hr, respectively. Similarly, the results of a rapid PCR-based assay can be communicated to the clinicians less than 2 hr following the report of a bacteremia. Together, these results demonstrate that the rapid preparation of a blood culture bacterial pellet has a significant impact on the identification and AST turnaround time and thus on the successful outcome of patients suffering from bloodstream infections.     

Observations on some common parasites of Bagrus docmac Forskahl (pisces: siluroidea) of lake Victoria

During the June–August period, 1977, four sets of water and sediment samples were collected for bacteriological analysis, from a salt-fresh water shoreline transect in Northern Canada (51°30 north latitude). Samples were processed for health indicator bacteria, organic sulfur reducing bacteria, ammonifying bacteria, denitrifying bacteria and ATP. Some chemical parameters were also studied. Based on the water classification scheme proposed by Sorokin & Kadota, the total bacterial population found in the sea sampling stations, would indicate that these waters are very eutrophic. The microbial biomass in these waters leads one to suspect that there may be an underestimation of the potential biodegradation capacity of these waters.     

Vertical distribution of bacteria in arctic sea ice

Abstract Heterotrophic bacteria were enumerated in north polar sea ice cores obtained near Point Barrow, Alaska. Highest concentrations of total and viable bacteria were found in the layer containing the sea ice microbial community identified by the maximum chlorophyll a content. Gas vacuolate bacteria were also found in the sea ice, a discovery which is consistent with their recent report from antarctic sea ice microbial communities. The gas vacuolate bacteria comprised 0.2% or less of the viable bacteria isolated from sea ice cores, lower than concentrations reported for most antarctic samples. Most gas vacuolate isolates from the sea ice cores were pigmented pink, orange, or yellow. An ice core from nearby saline Elson Lagoon contained an inverted sea ice microbial community with highest chlorophyll a concentrations and bacterial counts found in the top 0–20 cm of the ice. This surface layer also contained high numbers (up to 186 bacteria/ml) of a nonpigmented, gas vacuolate, elongated rod-shaped bacterium.     

Akkermansia muciniphila might improve anti-PD-1 therapy against HCC by changing host bile acid metabolism

PD-1 monoclonal antibodies (mAb) have demonstrated remarkable efficacy in a variety of cancers, including Hepatocellular carcinoma (HCC). However, the patient response rates remain suboptimal, and a significant proportion of initial responders may develop resistance to this therapeutic approach. Akkermansia muciniphila (AKK), a microorganism implicated in multiple human diseases, has been reported to be more abundant in patients who exhibit favorable responses to PD-1mAb. However, the underlying mechanism has yet to be elucidated. In our study, we found that AKK could enhance the efficacy of PD-1mAb against HCC in a tumor-bearing mouse model. It promotes HCC tumor cells apoptosis and raise the CD8⁺T proportion in the tumor microenvironment. Additionally, AKK downregulates PD-L1 expression in tumor cells. Furthermore, the analysis of metabonomics demonstrates that AKK induces alterations in the host's bile acid metabolism, leading to a significant increase in serum TUDCA levels. Considering the immunosuppresive roles of TUDCA in HCC development, it is plausible to speculate that AKK may reinforce the immunotherapy of PD-1mAb against HCC through its impact on bile acid metabolism.     

Resident bacteria in a mixed population of rhesus macaque (Macaca mulatta) monkeys: a prevalence study

Background  Microflora populations residing in oropharyngeal and gastrointestinal sites defend against pathogenic bacterial colonization. Perturbations in these microbial communities may allow opportunistic pathogenic bacteria to establish themselves and cause morbidity and mortality from sepsis particularly after stressful experimental procedures. This study determined the prevalent facultative bacteria in a resident population of Macaca mulatta prior to use in experimentally induced immunosuppressive radiation studies.
Methods  Standard microbiological methods were used to assess prevalent facultative bacteria in the oropharynx and rectum of 24 male M. mulatta .
Results  The majority of the bacteria isolated from the oropharyngeal and rectal sites were gram-positive cocci. Species of Staphylococcus and Streptococcus predominated in all samples. Few gram-negative bacteria were isolated.
Conclusions  Bacteriological assessment is recommended to identify predominant bacterial species to be prepared to provide appropriate antimicrobial therapy in non-human primates that are expected to undergo stressful immunocompromising procedures.     

Evaluation of potential health risks to Eastern Elliptio (Elliptio complanata) (Mollusca: Bivalvia: Unionida: Unionidae) and implications for sympatric endangered freshwater mussel species

Conservation efforts for freshwater musselspecies require identification and evaluationof potential health risks to populations. Sampling large numbers of individual mussels,however, could damage the small, fragile,extant populations of imperiled mussel species. In this study, a small sample size was designedto reduce lethal sampling, costs, andenvironmental disruption, while still allowing95% confidence in detecting health risks of25% or greater prevalence in the population. Health assessments were conducted on twentyspecimens of the Eastern Elliptio, Elliptio complanata, collected from two NorthCarolina sites as part of a survey to evaluatepotential disease threats to mussels in theregion. Bacteriological sampling of thegastrointestinal tracts yielded 18 aerobicbacterial species, of which Aeromonashydrophila (55.0%), Enterobacter spp.(40.0%), and Bacillus spp.(30.0%) were predominant. Histologicallesions of internal organs included mild tomoderate digestive gland atrophy andinflammation in one mussel, and mild tomoderate parasitism in several individuals. Adistinct difference in parasite prevalence wasevident between infections in E.complanata from the two collection sites. Thetrematode metacercaria of Homalometronarmatum and what appears to be three gillciliate species, the most abundant beingtentatively identified as the scyphidiidperitrich Mantoscyphidia sp., were foundin mussels from one site only. This studydemonstrates a comprehensive diagnosticapproach incorporating multiple modalities toassess the health status of mussel populations,while minimizing the sample size required toobtain valuable information. Furthermore, thisstudy provides baseline health data of E.complanata at two sites in south-central NorthCarolina and suggests the potential usefulnessof E. complanata as an environmentalbioindicator of health risks to sympatricthreatened freshwater mussel populations.     

Classification of leprosy into multibacillary and paucibacillary groups: an analysis

Classification of leprosy patients into multibacillary and paucibacillary determines the duration of their treatment. Misclassification leads to increased risk of relapse due to insufficient treatment if a multibacillary patient is classified as paucibacillary. This also prolongs the time the patient is infective. Over the years, the criteria used for classification (for treatment purpose) of leprosy patients have changed significantly from bacterial index measuring approach through number of skin lesions. The reliability of both of these criteria has been questioned. Several studies have shown that the presence of antibodies to the Mycobacterium leprae -specific antigens correlates with the bacterial load of a leprosy patient. Further, there are reports where results of serology and bacteriological approaches have been found to agree substantially. Thus, serology seems to be a worthwhile convenient alternative tool for classification of leprosy into multibacillary or paucibacillary. Nevertheless, in view of the limitations of various classification criteria, follow-up studies are called for to understand the efficiency of various approaches in preventing relapse after treatment. The method ensuring the lowest rate of relapse could be adopted for future use in classifying these patients.     

In vitro fermentability and physicochemical properties of fibre substrates and their effect on bacteriological and morphological characteristics of the gastrointestinal tract of newly weaned piglets

Abstract

Fermentability of fibre has a great impact on the bacterial flora along the gastrointestinal tract of newly weaned piglets. Therefore, this parameter was determined by incubating in vitro different fibre substrates (chicory roots, sugar beet pulp, wheat bran and corn cobs) with contents of jejunum or caecum sampled from slaughtered pigs. Incubating with small intestinal contents, lactic acid was the only fermentation product. Fermentability was highest for chicory roots, followed by wheat bran and sugar beet pulp, while corn cobs were not fermented. Based on SCFA formed in the incubations with caecal contents, ranking of the fermentability of the fibre substrates was in the same order. The effect of adding different fibre substrates to diets of newly weaned piglets on bacteriological and morphological aspects of the gastrointestinal tract was also investigated. In Experiment 1 three groups of five piglets, weaned at four weeks of age, received a control feed (C), C supplemented with corn cobs (50 g/kg) or with chicory roots (20 g/kg). In Experiment 2, diet C was supplemented with sugar beet pulp (120 g/kg) or with wheat bran (75 g/kg). After three weeks animals were euthanized and digesta were sampled from stomach, proximal and distal jejunum, caecum and colon. Furthermore, mucosal scrapings were prepared and tissue samples were taken from jejunum, caecum and colon. Viscosity was determined for jejunal, caecal and colon contents. Corn cobs in the feed increased the number of total bacteria, lactobacilli and bifidobacteria in the stomach and proximal duodenum, while a decreased count of streptococci in distal jejunum contents was noted. Chicory roots increased the counts of Escherichia coli in the distal jejunum and on the mucosa, while sugar beet pulp decreased the number of lactobacilli on the mucosa only. Wheat bran seemed to increase the count of E. coli in jejunal digesta and on the mucosa, and also the number of lactobacilli in the stomach and jejunum. Bifidobacterial numbers were increased but only in the proximal part of the jejunum. Fibre substrates affected the concentration of lactate and SCFA in different parts of the intestinal tract. Feeding corn cobs increased villus length in the proximal jejunum by 13%. The number of intra-epithelial lymphocytes in the villous epithelium of proximal and distal jejunum was decreased by corn cobs and chicory roots supplementation while beet pulp and wheat bran had the opposite effect. In Experiment 1, apoptotic index of the mucosa of the distal jejunum was very low and decreased when corn cobs were fed. Mitotic index in the crypts was only affected by the wheat bran diet and a small decrease was noted. It was concluded that the fermentability of fibre was not an ideal criterion for predicting its effects on the flora. The effect of fibres on viscosity of digesta was negligible probably explaining the lack of clear and consistent influences on the intestinal mucosa.     

Enterococcus faecalis can be distinguished from Enterococcus faecium via differential susceptibility to antibiotics and growth and fermentation characteristics on mannitol salt agar

Enterococcus faecalis and Enterococcus faecium are both human intestinal colonizers frequently used in medical bacteriology teaching laboratories in order to train students in bacterial identification....