Bacteria Causing Gastrointestinal Infections
K. Balamurugan, U. Prithika in Pocket Guide to Bacterial Infections, 2019
EIEC are very similar to Shigella and possess the same toxin and virulence factors as that of Shigella. Both EIEC and Shigella appear to have evolved from nonpathogenic E. coli by acquisition of invasion plasmid (pINV) at different times. The pathogenesis and clinical features are similar to Shigella infection (Refer Shigella); however, the incidence is less when compared to Shigella. Children younger than 5 years of age are more commonly affected. They are transmitted through contaminated food and water and person-to-person spread also occurs. They are diagnosed by the presence of nonlactose fermenting colonies on MacConkey agar and later by nucleic acid hybridization technique and phenotypic assay for identifying the specific virulence genes and their cytotoxicity pattern. Antibiotics are not routinely recommended for EIEC infections.
Escherichia
Dongyou Liu in Laboratory Models for Foodborne Infections, 2017
E. coli grown on EMB agar produces black colonies with a diagnostic greenish-black metallic sheen. In addition, being lactose positive, E. coli generates deep red colonies on MacConkey agar, as fermentation of lactose decreases the medium’s pH and darkens the medium. Other biochemical features of E. coli include the ability to reduce nitrates to nitrites and to generate succinate, ethanol, acetate, and carbon dioxide. While most E. coli strains are positive for catalase, they are negative for oxidase, citrate, urease, and hydrogen sulfide. Further, E. coli is positive for indole production and the methyl red test. Given that about 98% of E. coli strains are positive in the indole test, it offers a useful approach to differentiate E. coli from other members of the family Enterobacteriaceae.
Escherichia
Dongyou Liu in Handbook of Foodborne Diseases, 2018
Physiologically, E. coli is versatile and adapted to the characteristics of the habitat, being able to grow in a medium with glucose as the only organic source. It can grow in the presence or absence of O2. Under anaerobic conditions, it can proliferate by fermentation, producing a mixture of acids and gas as final products. It can also grow by means of anaerobic respiration as it is able to use NO3, NO2, or fumarate as final electron acceptors by respiratory electron transport processes. This versatility of E. coli confers the ability to adapt to the intestinal (anaerobic) and extraintestinal habitat (aerobic or anaerobic).13 It is abundant in human and animal feces and is readily isolated by plating on selective media. The change in pH due to lactose fermentation can be used to differentiate between lactose-fermenting and non-lactose-fermenting strains on media such as MacConkey agar. Together with other enteric bacteria, for example, Citrobacter, Klebsiella, and Enterobacter, E. coli constitutes the coliform group, which could be easily detected and isolated from contaminated water and food, for their capacity to ferment lactose with acid and gas production within 48 hours at 35°C.14 Detection and enumeration of coliforms are used as indicators of sanitary quality of water and food products.15 Colony-forming units and most probable number are two methods commonly used to assess the threat of pathogen contamination. Monitoring the levels of E. coli contamination is important, because differences between nonpathogenic and pathogenic strains are often detectable only on the molecular level.16
Detection of mobile colistin-resistance gene variants (mcr-1 and mcr-2) in urinary tract pathogens in Bangladesh: the last resort of infectious disease management colistin efficacy is under threat
Published in Expert Review of Clinical Pharmacology, 2021
Bayasrin Ara, Umme Laila Urmi, Tanjum Ara Haque, Shamsun Nahar, Adity Rumnaz, Tamanna Ali, Mohammed Shah Alam, Abu Syed Md. Mosaddek, nor Azlina a Rahman, Mainul Haque, Salequl Islam
Collected urine samples were inoculated on MacConkey agar (Liofilchem, Italy) and cysteine-, lactose-, and electrolyte-deficient (CLED) agar (Liofilchem, Italy) simultaneously. MacConkey agar supports gram-negative UTI pathogens (Supplementary Figure 1A), while CLED agar aids in the growth of gram-negative bacteria and gram-positive cocci if present in urine samples. Urine cultures were incubated at 37°C overnight in aerobic conditions. Colony counts of 102 or 103 CFU/mL were considered a cutoff value for a probable UTI infection [23]. Gram’s staining and biochemical tests initially identified Growth-positive bacteria. A rapid biochemical-test kit API 20E (BioMe´rieux, Durham, NC), consisting of carbohydrate batteries and enzymatic substrates in a set of chromogenic panels, was used to confirm the isolated identity (Supplementary Figure 1B) [24]. A part of the bacterial identity was validated by the polymerase chain reaction (PCR) amplification and sequencing of the 16S rDNA gene [25]. The isolates were preserved in 30% glycerol in Trypticase Soy Broth (TSB) at – 80°C until further antimicrobial susceptibility analysis.
Effects of Brazilian green propolis extract on planktonic cells and biofilms of multidrug-resistant strains of Klebsiella pneumoniae and Pseudomonas aeruginosa
Published in Biofouling, 2020
Pâmela Beatriz do Rosário Estevam dos Santos, Damara da Silva Ávila, Lucas de Paula Ramos, Amanda Romagnoli Yu, Carlos Eduardo da Rocha Santos, Andresa Aparecida Berretta, Samira Esteves Afonso Camargo, Jonatas Rafael de Oliveira, Luciane Dias de Oliveira
Eight multidrug-resistant strains of K. pneumoniae and P. aeruginosa were evaluated. The bacteria were donated by clinical laboratories from the Grupo Policlin Saúde (São José dos Campos, SP, Brazil) and Valeclin Laboratório de Análises Clínicas (São José dos Campos, SP, Brazil), with identification and antibiograms performed using the MicroScan autoSCAN-4 system (Beckman Coulter, Brea, CA, USA). Additionally, reference strains from the American Type Culture Collection (ATCC) of K. pneumoniae (ATCC 4352) and P. aeruginosa (ATCC 15442), stored at the Laboratory of Microbiology and Immunology (ICT-UNESP), were evaluated for comparative purposes. These strains were kept at −80 °C in Brain Heart Infusion broth (BHI; Himedia, Mumbai, India) with 20% glycerol. Bacterial activation was performed on MacConkey agar (Kasvi, São José dos Pinhais, PR, Brazil) with incubation at 37 °C for 24 h.
Soft, chewable gelatin-based pharmaceutical oral formulations: a technical approach
Published in Pharmaceutical Development and Technology, 2018
Morten J. Dille, Magnus N. Hattrem, Kurt I. Draget
A QuanticultTM suspension containing ≤100 CFU/0.1 ml of Escherichia coli (ATCC 8739) was prepared. Duplicate inoculum plates were set up on TSA. Test samples with 10 g chewable ibuprofen tablets were prepared with 990 ml DNP with a pH of 7.0 was prepared and inoculated with not more than 100 CFU of E. coli. Negative and positive controls were prepared as described before. The inoculated suspension (100 ml) was transferred to 100 ml of tryptone soya broth (TSB), mixed and incubated at 30–35 °C for 24 h. After incubation 1 ml of the TSB/inoculated suspension was transferred to 100 ml MacConkey broth and was incubated for another 24 h at 42–44 °C and followed by subculture on MacConkey agar. The MacConkey agar was incubated at 30–35 °C for 24 h. After incubation the identification of E. coli was examined. The test was negative when absence of E. coli was observed. This validation method was successful. Microbial stability of samples stored for 12 months was assessed in a similar manner.
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