Antitoxin

The discovery and study of toxin-antitoxin (TA) systems helps us advance our understanding of the strategies prokaryotes employ to regulate cellular processes related to the general stress response, such as defense against phages, growth control, biofilm formation, persistence, and programmed cell death. Here we identify and characterize a TA system found in various bacteria, including the global pathogen Mycobacterium tuberculosis. The toxin of the system (DarT) is a domain of unknown function (DUF) 4433, and the antitoxin (DarG) a macrodomain protein. We demonstrate that DarT is an enzyme that specifically modifies thymidines on single-stranded DNA in a sequence-specific manner by a nucleotide-type modification called ADP-ribosylation. We also show that this modification can be removed by DarG. Our results provide an example of reversible DNA ADP-ribosylation, and we anticipate potential therapeutic benefits by targeting this enzyme-enzyme TA system in bacterial pathogens such as M. tuberculosis.

Background: Foodborne botulism is a fatal paralytic illness caused mainly by the neurotoxin produced by an anaerobic bacterium called Clostridium botulinum. In this study, the frequency of foodborne botulism in patients referred to a hospital in Iran has been reviewed for ten years. Methods: In this routine database study, medical records of patients with foodborne botulism referred to Loghman Hospital in Tehran City, Iran, from March 20, 2008, to March 20, 2019, were reviewed. Information on variables of age, sex, place of residence, food consumed, clinical symptoms of patients (such as dysphagia, nausea, vomiting, ataxia, etc.), toxin type, and length of hospitalization were collected with a researcher-made questionnaire. Finally, the collected data were analyzed in SPSS-24 with descriptive and analytical statistical tests. Results: In this study, 61 suspected botulism patients were clinically diagnosed in Loghman Hospital, of whom 55 patients were clinically suspected of foodborne botulism, 5 patients had iatrogenic botulism, and 1 patient had infant botulism. Of these 55 patients with the clinical diagnosis of foodborne botulism, 19 patients were confirmed by laboratory examinations, and 2 patients died. Sixteen patients confirmed by laboratory had neurotoxin botulinum type A. The mean age of the patients was 36.9 years with a standard deviation of 18.6 years. About 54.5% of the patients were male and 45.5% female. Weaknesses (58.2%), ptosis (droopy eyelid) (56.4%), and diplopia (double vision) (52.7%) were the common clinical symptoms of the patients under study. Canned foods and dairy products were the main foods consumed by the patients. The duration of admission time ranged between 1 and 41 days, with an average of 7.7 days. About 23.64% of patients were admitted to the intensive care unit. Conclusion: The prevalence of foodborne botulism is rare compared with other food poisonings but is still a major public health problem due to the consumption of traditional food products and unboiled canned foods in Iran.