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Scombrotoxin
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Detection of HPB is important in outbreak investigations and in management of SFP. The main challenges are the diversity of the bacteria that are able to produce histamine and the different growth and media conditions required to detect all types of HPB. Culture- and molecular-based methods exist for detection of gram-negative HPB in fish. For the culture-based methods, differential histidine-containing broths or agar media containing indicator dyes have been developed. These media rely on a color change of the indicator dyes resulting from an increase in pH that occurs during histamine formation. One of the most frequently used methods for detection of gram-negative HPB is use of Nivens medium (68), a differential medium based on the color change of bromocresol purple from green to purple as the pH of the media increase from initial pH of 5.3. The incubation temperature of 35°C for 36–72 hours was used for isolation of M. morganii and R. planticola using this method. Several attempts have been made to modify this method with variable results (69,70). A similar broth media was developed using bromocresol green and chlorophenol red as indicator dyes where tubes were incubated at 30°C and color change from green to purple was seen within 12 hours (71). The main drawback of these differential culture-based methods is the high false-positive (15%–63%) and false-negative reactions (42,55,72). False-positive reactions are likely due to production of other basic compounds (other than histamine) that increase the pH of the medium. In addition, the low pH and salt content of the media may inhibit growth of some HPB, and the incubation time and temperature have to be carefully selected to account for all HPB species. For that reason, this method is suitable for screening purposes only where histamine production of isolates is confirmed by inoculation into histidine-containing broths under ideal conditions, and histamine concentrations are determined.
Acids produced by lactobacilli inhibit the growth of commensal Lachnospiraceae and S24-7 bacteria
Published in Gut Microbes, 2022
Emma J. E. Brownlie, Danica Chaharlangi, Erin Oi-Yan Wong, Deanna Kim, William Wiley Navarre
To examine the influence of pH more extensively across our entire collection of Lactobacillaceae species, we selected one isolate of each species to test the effects of their respective culture supernatants on the growth of the S24-7 strain NM74_B14 (with the exception of L. iners, which was unable to grow under these conditions). Supernatants were taken from cultures of each Lactobacillaceae species, either adjusted to pH 7 or left unadjusted, and subsequently inoculated with NM74_B14 to evaluate growth. Both turbidity and pH were measured for each Lactobacillaceae culture before taking supernatant, and turbidity measurements varied dramatically between Lactobacillaceae species independent of inhibitory capacity (Table S4). The pH of uninhibitory cultures ranged from pH 6.3–6.7 compared to pH 5.2–6.3 for inhibitory cultures, thereby corroborating the observations from the bromocresol purple assay. In the supernatants of uninhibitory Lactobacillaceae species NM74_B14 grew with and without pH adjustment, while for inhibitory species it only grew when the pH was adjusted to 7.0 (Figure 4b). The exception was S. shenzhenensis (inhibitory), which grew poorly in the liquid media we used and maintained a high culture pH relative to other inhibitory isolates. NM74_B14 grew in both unadjusted and adjusted S. shenzhenensis supernatants.
Evaluation of association between parameters related to penetration into cerebrospinal fluid and the microbiological efficacy of vancomycin in patients with bacterial meningitis
Published in Journal of Chemotherapy, 2022
Masayuki Ishikawa, Masashi Uchida, Shingo Yamazaki, Yuki Shiko, Yohei Kawasaki, Takaaki Suzuki, Yasuo Iwadate, Itsuko Ishii
VMser and VMCSF were measured by a chemiluminescence immunoassay with an ARCHITECT® analyzer (Abbott Laboratories, Irving, TX). The method was fully validated over a concentration range of 3.0–100.0 μg/mL. The lower limit of quantification and the lower limit of detection were 3.0 μg/mL and 0.24 μg/mL, respectively. SA concentrations were measured by the bromocresol green or bromocresol purple method. The SA value measured by the bromocresol green method is known to be about 0.3 mg/dL higher than that measured by the bromocresol purple method. Therefore, if the SA was measured by the bromocresol green method, we subtracted 0.3 mg/dL from the measured value based on the guidelines [14]. CSF proteins and CSF glucose concentrations were measured by the pyrogallol red and hexokinase methods, respectively. CSF cell counts were performed manually. The MIC for bacteria was determined via the broth microdilution method of the Clinical and Laboratory Standards Institute. Creatinine clearance was calculated by the Cockcroft–Gault formula, using actual body weight [15].
Production, purification and biochemical characterisation of a novel lipase from a newly identified lipolytic bacterium Staphylococcus caprae NCU S6
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2021
Junxin Zhao, Maomao Ma, Zheling Zeng, Ping Yu, Deming Gong, Shuguang Deng
It was reported that the lipases were generally produced in the presence of lipid sources, such as olive oil15. A total of 36 bacterial isolates were identified from the sewerage samples collected at Nanchang City, Jiangxi Province, China. In the preliminary screening, only 22 isolates showed clear halo on the bromocresol purple plates after 24-h cultivation at 37 °C, among them 13 isolates also produced a zone of clearance surrounding each colony after 2-day incubation on tributyrin agar plates. However, the tributyrin was not only sensitive to hydrolysis by lipases, but also by esterases. Rescreening of the 13 isolates found that only 6 of them showed obvious effect of lipase production on Rhodamine B agar plate. NCU S6 was found to be the best lipolytic strain that showed the broadest orange fluorescence halos around each colony through UV irradiation.