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Bacteria Causing Gastrointestinal Infections
Published in K. Balamurugan, U. Prithika, Pocket Guide to Bacterial Infections, 2019
B. Vinoth, M. Krishna Raja, B. Agieshkumar
Isolation of the organism by culture is required for making a confirmatory diagnosis. Because the organisms are fastidious, the stool should be inoculated in to a specific medium at the bed side, or it has to be transported in a special medium (i.e., Cary-Blair medium or Buffered glycerol saline). The World Health Organization (WHO) has recommended a diagnostic algorithm for diagnosing Shigella infection according to which the stool samples are inoculated on MacConkey agar and a more selective xylose lysine deoxycholate agar (XLD agar). Shigella is nonlactose fermenter and hence appears pale pink on MacConkey agar and appears pink on XLD medium. The suspected colonies are then inoculated in to Kligler iron agar (KIA) and motility indole urea (MIU) medium. Based on the specific characteristic features on these medium, they can be differentiated from E. coli (i.e., Shigella are nonmotile, produce alkaline slant, indole positive, urease and oxidase negative with no gas or hydrogen sulfide production, and ferment glucose). Molecular studies like PCR-based assays are currently available to detect the invasion-associated locus of specific species and can detect as few as 10–100 organisms (Avraham et al. 1982; Nataro et al. 1995). The advantage of culture over the molecular studies is that antibiotic susceptibility can also be tested, which is important in deciding appropriate antibiotics, especially in the current scenario of growing antibiotic resistance.
Plesiomonas
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Gabriel Forn-Cuní, Zoha Tavakkoliamol, Juan M. Tomás
P. shigelloides appears in different colony shapes depending on the medium used for growth. For example, colonies are flat, round, with smooth edges or flat with irregular edges using blood or deoxy chocolate agar, respectively. Most P. shigelloides strains can be cultured in routine enteric media, such as MacConkey agar (MAC), xylose lysine decarboxylase (XLD) agar, or Hektoen enteric agar (HE) [86]. Of note, P. shigelloides colonies will be green in HE agar [50,87]. Plesiomonads have also been recovered from deoxycholate citrate agar, deoxy cholate lactose agar, and Salmonella-Shigella agar, although some strains do not grow well in the latter. More specific and useful media for P. shigelloides identification are inositol brilliant green-bile salts (IBB) and cefsulodin-irgasan-novobiocin agar (CIN). CIN can be useful to distinguish plesiomonads from other oxidase-positive bacteria: Plesiomonas colonies are colorless, while Aeromonas colonies have pink centers in this medium [88]; IBB is regarded as the most specific medium for Plesiomonas identification [89].
Shigella
Published in Dongyou Liu, Laboratory Models for Foodborne Infections, 2017
Soumik Barman, Yoshifumi Takeda
For daily laboratory screening of shigellae, two different selective media are generally used, namely Hektoen enteric (HE) agar and xylose lysine desoxycholate (XLD) agar. Shigella colonies on XLD agar appear translucent, pink, or red and are smooth in nature. S. dysenteriae 1 colonies on XLD agar are commonly very small, unlike those of other Shigella species.23 Colonies of shigellae on HE agar appear green. Serological identification by slide agglutination with polyvalent somatic antigen grouping sera further confirms the serotypes and subserotypes.
The effect of gold and silver nanoparticles, chitosan and their combinations on bacterial biofilms of food-borne pathogens
Published in Biofouling, 2020
Ondrej Chlumsky, Sabina Purkrtova, Hana Michova (Turonova), Viviana Svarcova (Fuchsova), Petr Slepicka, Dominik Fajstavr, Pavel Ulbrich, Katerina Demnerova
The liquid media used for the cultivation of bacteria were brain heart infusion (BHI) or tryptone soya broth supplemented with 1% glucose (TSB + 1Gl). The following solid media were used: the selective-diagnostic agars Baird-Parker (BP) agar, agar Listeria according to Ottaviani and Agosti (ALOA) agar, xylose lysine deoxycholate (XLD) agar and the non-selective plate count agar (PCA). All media were purchased from Merck (Darmstadt, Germany). Dimethyl sulfoxide (DMSO), 96% ethanol, 99% acetic acid, sodium hydroxide, and glucose were purchased from Penta (Czech Republic). 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide (MTT), crystal violet, polyethylene glycol (PEG) 600, sodium dodecyl sulfate (SDS) and low molecular weight chitosan (50 kDa) were purchased from Sigma Aldrich (St Louis, MO, USA). Gold and silver of 99.9999% purity were both purchased from Safina (Vestec, Czech Republic). Phosphate-buffer-solution (PBS) was bought from Lonza (Kourim, Czech Republic), and 1% sodium silicotungstate from Fisher Scientific (Waltham, MA, USA).