Bacteria, Volume 4, Issue 2 (June 2025) – 7 articles

This study evaluated the effects of dietary dill weed (DW) on growth, hematological profile, digestive enzyme activities, antioxidative response, heat tolerance, gut microbiota composition, and disease resistance in African catfish (Clarias gariepinus). A control diet (basal diet) was compared to three DW diets (DW5, DW10, and DW15) with increasing DW levels (0.5, 1.0, and 1.5%, respectively). After eight weeks, fish fed DW diets exhibited significantly higher growth performance (p < 0.05) compared to the control group, as evidenced by increased final weight (FW), specific growth rate (SGR), and weight gain (WG). Conversely, the feed conversion ratio (FCR), hepatosomatic index (HSI), and visceral somatic index (VSI) were significantly lower (p < 0.05) in fish fed DW diets compared to the control. Dietary DW supplementation significantly enhanced (p < 0.05) hematological profiles, including red blood cell (RBC), white blood cell (WBC), hematocrit (HCT), and hemoglobin (HBG), compared to the control group. Similarly, antioxidant responses, including superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) activity, significantly increased (p < 0.05) in fish fed DW diets before or after the heat tolerance assay. Fish fed DW diets displayed a higher relative abundance of beneficial gut microbiota, including Cetobacterium spp., Akkermansia muciniphila, Phocaeicola spp., and Niameybacter massiliensis. Furthermore, dietary DW supplementation stimulated disease resistance against Edwardsiella tarda infection in African catfish. Regression analysis indicated that the optimal DW inclusion level for promoting growth performance and health status in African catfish ranged from 0.229 to 0.433%. Full article

Antibiotic resistance is a major problem worldwide, especially with the overuse and misuse of antibiotics. This makes it more challenging to treat patients infected with antibiotic-resistant bacteria, with more costs on the health system. This review article describes extended-spectrum β-lactam antibiotics as the most used antibacterial agents, and how bacteria developed beta-lactamases (ESBLs) to resist these antibiotics. The review focuses more on the problem of ESBLs in Kuwait to uncover which ESBLs are present and what ESBL gene mutations have been found in this country. The literature review, surprisingly, revealed a limited number of studies in Kuwait on ESBL gene mutations, published over the last 25 years. The results showed that Kuwait has an alarming number of bacterial strains with ESBL gene mutations. These studies reported different mutations in different bacterial strains isolated from different types of specimens, which were collected from different hospitals in Kuwait. The data from these studies were scattered and not linked or analysed together to highlight the big picture of the problem of ESBLs in Kuwait. This review article highlights that the amount of research on ESBLs in Kuwait is not up to the expectations of a country like Kuwait, which has high-standard research facilities. Bearing in mind that the geographic area of Kuwait is relatively small, the authors of this paper think that there might be more β-lactam bacteria spreading in Kuwait, which need to be explored, and that more research and more collaboration are needed among researchers in Kuwait to address this risky situation. Full article

Clostridioides difficile Infection (CDI) continues to be a major cause of antibiotic-associated diarrhea and pseudomembranous colitis, fueled in large measure by virulence factors TcdA and TcdB. These giant glucosyltransferase toxins interfere with host cytoskeletal integrity and inflammatory signaling by inhibiting Rho GTPase; however, the detailed structural dynamics, receptor selectivity, and subcellular trafficking mechanisms remain in part unspecified. This review integrates recent insights from cryo-electron microscopy (cryo-EM) and X-ray crystallography to describe the quaternary architecture of TcdA/B, emphasizing conformational changes key to pore formation and endosomal escape. We also examine the genomic heterogeneity of hypervirulent C. difficile strains (e.g., ribotype 027), correlating toxin gene polymorphisms (e.g., tcdC mutations) with increased toxin production and virulence. Mechanistic explanations of toxin-driven inflammasome activation and epithelial barrier dysfunction are situated within host immune evasion mechanisms, including microbiota-derived bile acid regulation of toxin stability. Subsequent innovative therapeutic strategies, encompassing the utilization of engineered neutralizing antibodies that specifically target the autoprocessing domain alongside structure-guided small-molecule inhibitors, are subjected to a rigorous evaluation. By integrating structural biology, systems-level omics, and clinical epidemiology, this review establishes a comprehensive framework for understanding C. difficile toxin pathogenesis and guiding next-generation precision antimicrobials. Full article

Minimally processed foods (MPFs), often considered ready-to-eat, do not undergo cooking and therefore require proper handling and preparation to ensure safety. If not handled correctly, these foods can serve as a pathway for diseases caused by pathogenic bacteria, including Escherichia coli and Salmonella spp. The antibacterial activity of essential oils (EOs) has been increasingly studied as a tool for controlling microorganisms in the food sector. Therefore, we aimed to verify the contamination of MPF by E. coli and Salmonella and to test the sensitivity of these strains to Copaifera langsdorffii, Schinus terebinthifolius, Citrus reticulata, Eucalyptus citriodora, Elettaria cardamomum, Ocimum basilicum, and Eugenia caryophyllus EOs using the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. From 25 MPF samples, one E. coli strain and one Salmonella spp. were isolated. C. langsdorffii and C. reticulata EOs did not show antibacterial activity, while S. terebinthifolius and E. citriodora inhibited the growth of both strains. The E. cardamomum, O. basilicum, and E. caryophyllus EOs presented inhibitory and bactericidal responses at concentrations 0.78, 0.39, and 0.19% (v/v), respectively, compared to the two isolated strains. The present study reinforces the antibacterial potential of EOs and suggests their application in the MPF production chain. Full article

Pathogenic Escherichia coli can cause a variety of intestinal and extra-intestinal infections in humans and animals. The availability and subsequent misuse of antimicrobials, especially in poultry production systems, has contributed immensely to the emergence and spread of multidrug-resistant E. coli. This study investigated the genotypic characterization of colistin-resistant E. coli and selected antimicrobial-resistance encoding genes along with their phenotypic resistant pattern and the multiple antimicrobial resistant (MAR) index from village chickens in Kelantan. Sixty E. coli isolates obtained from a previous study’s stock culture were enriched and analyzed using routine microbiological methods: Kirby–Bauer disc diffusion method, minimum inhibitory concentration (MIC), and PCR amplification of E. coli species-specific and multidrug-resistance mcr-positive E. coli. All the isolates were confirmed as E. coli and 16.6% (10/60) were positive for mcr. Five isolates were positive for mcr-1, three for mcr-4, and two for mcr-9. The mcr-positive isolates showed varying degrees of resistance to different antimicrobials. The isolates were resistant to gentamicin (100%), chloramphenicol (100%), and tetracycline (89.4%) and susceptible to ceftaxidime (2.26%) and imipenem (18%). Furthermore, 100%, 94.7%, and 89.4% of isolates from village chickens belonged to phylogroup C, B2, and E, while 21.0% and 42.1% of the isolates belonged to phylogroup A and B1, respectively. Sequence types (STs) of selected E. coli isolates were further analyzed using multi-locus sequence typing, and 10 different STs were identified. This study showed the emerging threats of multidrug-resistant mcr-positive E. coli gene in village chickens that are believed to be raised with minimal or no antibiotics. Full article

Background: Shigella species are the leading cause of human shigellosis. In Zambia, more than 30% of children experiencing diarrhea are infected with Shigella species. The increasing resistance of Shigella species to the recommended therapy is of great concern. Therefore, this study investigated the antibiotic resistance profiles and phenotypic and genotypic characteristics of Shigella isolates at the largest referral hospital in Zambia. Methodology: Of the forty-eight archived presumptive Shigella isolates, thirty-two were serologically confirmed and subjected to antimicrobial susceptibility testing using the Kirby Bauer disk diffusion method. Thereafter, polymerase chain reaction was performed to detect the bla genes. Results: Most isolates were Shigella flexneri (16/32, 50%) and Shigella sonnei (14/32, 44%), while Shigella boydii and Shigella dysenteriae were rare. High resistance rates were noted for sulfamethoxazole/trimethoprim (78%) and tetracycline (75%), while 15.6% of the isolates showed resistance to ciprofloxacin and/or azithromycin. The bla_TEM gene encoding beta-lactamase was detected in 7/32 (22%) of isolates. Conclusions: In this study, a significant number of multidrug-resistant isolates were identified. Additionally, Shigella species resistant to the World Health Organization-recommended drugs call for strengthened laboratory diagnosis and close monitoring of these pathogens to guide the clinical management of shigellosis. Full article

Concerns about the health consequences of seafood-born human pathogens are ongoing given their occurrence, prevalence, and ability to cause infections, and sometimes death in humans as well as seafood-associated morbidity and mortality worldwide. An applied time-series (2000–2017) analysis of six reefs examined pathogen-specific annual trends and seasonal patterns in the eastern oyster, Crassostrea virginica, in Galveston Bay (Texas), a subtropical estuary in the Gulf of Mexico. Pearson correlation coefficients showed that temperature had a strong positive correlation with Vibrio vulnificus and V. parahaemolyticus (r = 0.66 and 0.51), but not the pathogenic thermostable direct hemolysin (tdh+) V. parahaemolyticus (r = 0.12). The correlations between Vibrio spp. and salinity showed the opposite trend. A cross-correlation factor analysis revealed the strongest positive correlations (r = 0.41 and r = 0.36, respectively) for high densities of V. vulnificus during high Perkinsus marinus infections with short lags (up to 1 month); this was not the case for total or tdh+ V. parahaemolyticus. These results reveal some of the complexity of interannual and long-term patterns of pathogens in oysters. Given climate change impacts and a growing aquaculture industry, examinations of oyster microbiomes in response to environmental and water quality variables are needed. Full article