Microbiology insights最新文献

Introduction: Methicillin resistant Staphylococcus aureus (MRSA) is a major human pathogen associated with nosocomial and community infections. mecA gene is considered one of the important virulence factors of S. aureus responsible for acquiring resistance against methicillin. The main objective of this study was to explore the prevalence, antibiotic susceptibility pattern, and mec A gene.

Methods: A total of 39 isolates of S. aureus were isolated from 954 clinical specimens processed in Microbiology laboratory of Himal Hospital, Kathmandu. Antimicrobial susceptibility test (AST) was performed by Kirby-Bauer disc diffusion method using cefoxitin, and performed Polymerase Chain Reaction (PCR) for amplification of mecA gene in MRSA isolates.

Results: Out of 954 clinical samples, (16.2%; 153/954) samples had bacterial growth. Among 153 culture positive isolates, 25.5% (39/153) were positive for S. aureus. Among 39 S. aureus (61.5%; 24/39) were multiple drug resistant (MDR). On AST, amoxicillin was detected as the least effective while vancomycin was the most effective. The prevalence of methicillin resistance was 46% (18/39) of which 72.2% (13/18) were positive for mecA gene in PCR assay.

Conclusion: One in 4 culture positive isolates from the clinical specimens were S. aureus, of which almost two-thirds were MDR. Around half of the MDR showed MRSA and significant proportion of them were positive for mecA gene. This study concludes that the mecA gene is solely dependent for methicillin resistance in S. aureus but the presence of gene is not obligatory. PCR detection of the mecA gene is reliable, valid and can be suggested for the routine use in diagnostic laboratories.

Background: Malaria and HIV are 2 significant infections of critical public health concern globally. Malaria infection is one of the preceding causes of morbidity and mortality in endemic developing countries, and its co-infections in HIV patients worsen prognosis; with anaemia being the most common haematologic outcome of the infections.

Context and purpose of study: This study was aimed at determining the prevalence of anaemia and malaria co-infection among HIV-infected patients attending selected hospitals in Abuja between February and July 2019.

Methods: A cross-sectional study was carried out to detect malaria in 420 HIV-positive patients who were 12 to 67 years old, using enzyme immunoassay and microscopy. A structured questionnaire was used to capture socio-demographic and risk factors ([Frequency of] Use of Malaria preventive Measures, History of anaemia, Blood type, malaria antecedents, and CD4+ Count) while packed cell volume was checked using micro haematocrit reader to determine anaemia status. Data were analysed using IBM SPSS v25.

Results: The mean age of the study participants was 37.5 (±12.48). A total of 142 (33.8%) samples were positive for malaria, and 68 of the HIV-infected patients (16.2%) were anaemic; 4.8% of the 420 patients had malaria co-infection and anaemia simultaneously. More male participants had malaria co-infection (36.0%, P = .617) while more female participants had anaemia (22.7%, P = .058). Patients aged 61 to 70 years had the highest rates of malaria and those aged 51 to 60 years were most anaemic. Except for patients with normal CD4+ count, those who were more exposed to the evaluated risk factors were more co-infected and anaemic. Malaria co-infection did not significantly affect the onset of anaemia. Test for the validity of Microscopy against Enzyme Immunoassay (EIA) showed 83.1% sensitivity and 98.6% specificity. No association was observed between the variables and the parasitaemia density of the patients.

Conclusions: This study highlighted higher rates of malaria co-infection and anaemia among HIV patients when compared with previous reports in the region although co-infection did not significantly affect anaemia status. Given this trend, strategies must be put in place to checkmate these ailments. Population studies are also advocated.

Gonorrhea, caused by Neisseria gonorrhoeae, is a common sexually transmitted infection and an urgent public health problem. Humans are the exclusive host, and the genital tract with heterogeneous epithelia is the primary niche of this bacterium, creating unique challenges for understanding its pathogenesis. The cervical tissue explant model that we have developed enabled us to show that the properties of the epithelial cells in the female reproductive tract are the main factors driving gonococcal adaptation. Gonococcal variants that colonize strongly and penetrate poorly, thereby causing asymptomatic infection, survive better in the cervix. Gonococci adapt to different epithelial cell types by varying their surfaces and modulating distinct epithelial cell-cell adhesion complexes through manipulation of host cell signaling. These findings provide critical new insights on the mechanisms by which N. gonorrhoeae adapts to the human mucosal surface and causes asymptomatic infection.

The transition from acetate production by a microorganism in its early growth phase to acetate re-uptake in its late growth phase has been termed acetate switch. It has been observed in several heterotrophic prokaryotes, but not in an autotroph. Furthermore, all reports hitherto have involved the tricarboxylic acid cycle. This study reports the first observation of acetate switch in a methanogenic autotroph Methanococcus maripaludis S2, which uses the Wolfe cycle for its anaerobic respiration. When grown in minimal medium with carbon dioxide as the sole carbon source, and either ammonium or dinitrogen as the sole nitrogen source, M. maripaludis S2 dissimilated acetate in the early growth phase and assimilated it back in the late growth phase. The acetate switch was more pronounced in the dinitrogen-grown cultures. We postulate that the acetate dissimilation in M. maripaludis S2 may serve as a metabolic outlet for the carbon overflow in the early growth phase, and the assimilation in the late growth phase may be due to the scarcity of the carbon source. Based on the primary and secondary protein structures, we propose that MMP0253 may function as the adenosine diphosphate (ADP)-forming acetyl-CoA synthetase to catalyse acetate formation from acetyl-CoA. To verify this, we produced MMP0253 via the ligation-independent cloning technique in Escherichia coli strain Rosetta (DE3) using pNIC28-Bsa4 as the vector. The recombinant protein showed catalytic activity, when added into a mixture of acetyl-CoA, ADP, and inorganic phosphate (P_i). The concentration profile of acetate, together with the enzymatic activity of MMP0253, shows that M. maripaludis S2 can produce acetate and exhibit an acetate switch.

Antimicrobial peptides and proteins (AMPs) are molecules that can interact with microbial cells and lead to membrane disruption or intracellular molecule interactions and death. Several molecules with antimicrobial effects also present other biological activities. One such protein group representing the duplicity of activities is the tachykinin family. Tachykinins (TKs) form a family of neuropeptides in vertebrates with a consensus C-terminal region (F-X-G-Y-R-NH2). Invertebrate TKs and TK-related peptides (TKRPs) are subfamilies found in invertebrates that present high homology with TKs and have similar biological effects. Several of these molecules have already been described but reports of TKRP in Hemiptera species are limited. By analyzing the Triatoma infestans hemolymph by reversed-phase high-performance liquid chromatography, biological assays, and mass spectrometry, two antimicrobial molecules were isolated and identified as TKRPs, which we named as TRP1-TINF and TRP2-TINF (tachykinin-related peptides I and II from T. infestans). TRP1-TINF is a random secondary structure peptide with 9 amino acid residues. It is susceptible to aminopeptidases degradation and is active mainly against Micrococcus luteus (32 μM). TRP2-TINF is a 10-amino acid peptide with a 310 helix secondary structure and is susceptible to carboxypeptidases degradation. It has major antimicrobial activity against both Pseudomonas aeruginosa and Escherichia coli (45 μM). Neither molecule is toxic to human erythrocytes and both present minor toxicity toward Vero cells at a concentration of 1000 μM. As the first description of TKRPs with antimicrobial activity in T. infestans, this work contributes to the wider comprehension of the insects' physiology and describes pharmacological relevant molecules.

Saudi Arabia is in a tropical geographical region with a population that has access to adequate diet. There is, however, a high level of vitamin D deficiency in the Kingdom, comorbid with other disease. There is the postulation of a correlation between a healthy gut microbiota and balanced levels of serum vitamin D. This investigation looks into the effect of vitamin D supplementation on the gut flora of laboratory-bred mice as well as any possible association on body weight. BALB/C mice weighing between 34 and 35.8 g were divided into 4 groups and placed on daily doses of vitamin D of 3.75 µg (low dose), 7.5 µg (normal dose), and 15 µg (high dose). The fourth group was the control group that did not receive any supplementation with vitamin D. Body weights were monitored on weekly basis, while faecal samples from the rectum were obtained for microbial culturing and the monitoring of bacterial colony count using the Vitek 2 Compact automated system (BioMerieux, Marcy-l'Etoile, France) according to manufacturer's guidelines. The data presented as mean ± SD, while significant differences were determined with 2-way analysis of variance in comparing differences within and between treatment groups. The different doses of vitamin D showed varying effects on the body weight and gut microbial colonies of the mice. There was a highly significant difference between the control, 15 µg (high), and 7.5 µg (normal) dose groups. This is suggestive that supplementation with vitamin D could a role in the gut microbial flora in the gut which could reflect in changes in body weight.

The lengthy tuberculosis therapy is emblematic of how hard drug-persistent infections are to eradicate. Phenotypic variation within clonal bacterial communities contributes to drug evasion and has major implications for the treatment of drug-persistent infections. We reported that single mycobacterial cells exhibit differential drug susceptibility, contingent on their inherent phenotypic variation in DNA damage response. Individual cells experiencing severe DNA damage massively induce the SOS response and exhibit signs of programmed cell death (PCD), such as unbalanced growth, chromosomal fragmentation, autolysis, and release of the intracellular content. Toxin-antitoxin systems are known to contribute to PCD in model microorganisms by targeting essential cellular processes, and they might function similarly in mycobacteria. We have found that the toxin MazF and a Clp protease, possibly responsible for degrading the MazF cognate antitoxin MazE, are induced during harsh conditions in a model organism for tuberculosis, and that cells that are about to lyse from drug exposure display a buildup of toxin. Deeper analysis of PCD in mycobacteria may reveal whether this process belongs to a broader strategy for the community's survival. Finally, disrupting the balance between survival and PCD may prove useful to tackle drug evasion in mycobacterial persistent subpopulations.

Clostridium perfringens enterotoxin (CPE) is responsible for the symptoms of common intestinal infections due to C. perfringens type F isolates. CPE is a pore-forming toxin that uses certain claudins as a receptor. Previous studies showed that, in enterocyte-like Caco-2 cells, low CPE concentrations cause caspase 3-mediated apoptosis but high CPE concentrations cause necrosis. The recent work published in mBio by Shrestha, Mehdizadeh Gohari, and McClane determined that RIP1 and RIP3 are involved in both CPE-mediated apoptosis and necrosis in Caco-2 cells. Furthermore, mixed lineage kinase-domain (MLKL) oligomerization was shown to be important for necrosis caused by CPE, identifying this necrosis as programmed necroptosis. In addition, calpain activation due to Ca²⁺ influx through the CPE pore was identified as a critical intermediate step for MLKL oligomerization and, thus, CPE-induced necroptosis. These findings may have applicability to understand the action of some other pore-forming toxins that induce necroptosis and may also be important for understanding CPE action in vivo.

Background: Chronic hepatitis B (CHB) infection and nonalcoholic fatty liver disease (NAFLD) are liver diseases which may lead to hepatocellular carcinoma (HCC) formation. Both disease entities have been attributed independently to increase risk of HCC development. While concomitant hepatic steatosis in patients with CHB are becoming more frequent in view of increasing NAFLD prevalence, there is no conclusive evidence linking presence of hepatic steatosis and increased HCC risk in patients with CHB infection. This study explores the association of hepatic steatosis among CHB-infected individuals in HCC development.

Methods: This is a retrospective study on a cohort of patients with CHB who underwent liver biopsy between January 2000 and December 2014. They were stratified according to presence and severity of histologically proven hepatic steatosis and subsequently followed up to evaluate the association between hepatic steatosis and HCC development.

Results: Among 289 patients with a median follow-up of 111.1 months, hepatic steatosis was present in 185 patients (64.0%). In all, 27 patients developed HCC on follow-up and 21 of them had hepatic steatosis. Univariate Cox analysis showed that age (hazard ratio [HR] = 1.08, 95% CI = 1.042-1.12), type 2 diabetes mellitus (T2DM) (HR = 4.00, 95% CI = 1.622-9.863), and Ishak score (HR = 1.221, 95% CI = 1.014-1.472) were associated with HCC development, whereas multivariate Cox analysis demonstrated that age and T2DM (HR = 2.69, 95% CI = 1.072-6.759) were significant risk factors for development of HCC.

Conclusions: Concurrent hepatic steatosis in patients with CHB infection is not a risk factor for hepatocellular carcinoma formation.