Clostridium Bacteria: A Detailed Overview PDF

Clostridium Chapter 5 Introduction Clostridium, genus of rod-shaped, usually gram-positive bacteria, members of which are found in soil, water, and the intestinal tracts of humans and other animals. While some species in this genus may appear to be Gram- negative Most species grow on...

Clostridium Chapter 5 Introduction Clostridium, genus of rod-shaped, usually gram-positive bacteria, members of which are found in soil, water, and the intestinal tracts of humans and other animals. While some species in this genus may appear to be Gram- negative Most species grow only in the complete absence of oxygen. Dormant cells are highly resistant to heat, desiccation, and toxic chemicals and detergents Clostridium was discovered by the French microbiologist Louis Pasteur in the 1860s as a proof of existing anaerobic microorganisms Today, over 200 species belonging to the genus Clostridium have been identified. Of these, at least 30 are of clinical significance.  Display heterogeneous phenotypes, and are able to grow over a wide range of temperature (3.3 to 80 °C) with optimum between 25 and 40 °C for most species related to dairy products With the exception of C. perfringens(non motile), Clostridium species have peritrichous flagella that allow the organisms to move from one location to another (swim) Usually catalase-negative.  The G + C content (mol %) of chromosomal DNA ranges from approximately 22 to 53, which is considered to be too extensive a range for a single genus Clostridium genus harmful pathogens such as C. botulinum, Clostridium difficile, Clostridium perfringens, Clostridium tetani, C. butyricum, and Clostridium sordellii  Clostridium species are saprophytes, which means that they obtain their nutrients from dead plants and animals in soil and various aquatic environments play an important role in nitrogen fixation have the nif gene. species of genus Clostridium capable of nitrogen fixation include: C. beijerinkii C. acebutylicum Media for Growth For culture: Anaerobic Blood Agar or Brucella with H(Hemin) & K(Vitamin K) For selective isolation: Anaerobic PEA(Phenyl Ethyl Alcohol), Cycloserine-Cefoxitin Fructose Agar (CCFA; for Clostridium difficile ). For identification: Egg Yolk Agar For maintenance: Cooked Meat Media or Thioglycollate with Supplements. C perfrigenes Thioglycolate medium Colony morphology Clostridia possess no one typical colony morphology. They are generally a large colony (>2mm) with irregular edges or swarming growth. Some Clostridia form small, convex, non-hemolytic colonies with a smooth edge Clostridium perfringens usually produces a double zone of beta-hemolysis. The inner zone shows complete hemolysis, whereas the outer zone may display partial hemolysis On blood agar, Clostridium difficile are usually 2mm or more in diameter after 24 hours of incubation, fluoresce yellow-green, and emit a horse stable odor. C.perfrigenes Clostridial toxins Neurotoxins Neurotoxins are produced by two Clostridium species namely, Clostridium tetani (tetanus toxin) and Clostridium botulinum (botulinum toxin). The two toxins share several features including heavy H and light L chains that are bound by a disulfide bond. Botulinum Toxin (BoNT) Produced by C. botulinum, Botulinum toxin (BoNT) is a poisonous substance that works by binding to nerve endings (cholinergic nerve terminals). In doing so, the toxin blocks the release of neurotransmitter acetylcholine thus affecting muscle contraction. There are several types of toxins (BoNT) that include: A, B, E, F, C, C1, and C2. Tetanus Toxin (TeNT) Tetanus toxin is released by Clostridium tetani and is the primary cause of tetanus. From the bloodstream and lymphatic systems, the toxin is taken up through lower motor neurons and transported to the spinal cord or the brainstem. Although the toxin affects the central nervous system on several points, it significantly affects the neurotransmitter by blocking its release at the central inhibitory interneurons. In turn, this results in the disinhibition of the lower motor neurons which leads to uncontrollable contraction of muscle Enterotoxin Enterotoxin, a toxin released by C. perfringens is one of the main causes of gastrointestinal illness. While the bacteria produces several types of the toxin (A, B, C, D, E), Type A (and Type C in some cases) is the only toxin that is responsible for human illness. In the body (in vivo) the toxin is released during bacterial sporulation. The toxin is released into the intestinal lumen where it binds to the claudin receptors. This results in the formation of pre-pores and consequently functional pores (CH-1 pore) that cause oncosis(cell death with swelling) through calcium influx. Some of the other toxins released by Clostridium bacteria include: Cholesterol-dependent Cytolysins - This toxin is released by some of the Gram-positive Clostridium. Once released, the toxin bind to target cells and cause pore formation. Binary Bacterial Toxins - This toxin is released by a number of Clostridium bacteria including C. perfringens, C. spiroforme and C. botulinum. Through its mode of action (synergistic binary mechanism) the toxin causes intoxication and destruction of eukaryotic cells. EPIDEMIOLOGY Organisms of the genus Clostridium are important members of the humans’ anaerobic gastrointestinal and cervical-vaginal flora Clostridia are ubiquitous and are found in the soil, marine sediment, decaying vegetation and intestinal tract of humans, other vertebrate and insects Human infections with clostridia can result from endogenous or exogenous infection Usefulness Clostridium toxins can be used in therapy, research, and cosmetic industry. Besides, Clostridium strains have been widely used for the production of organic acids, organic solvent, and enzymes. Clostridium butyricum MIYAIRI has been studied for several decades, for its cholesterol-lowering effects, in cancer prevention and treatment of Clostridium difficile infection C. tetani Clostridium tetani is the causative organism for the disease process known as tetanus. Clostridium tetani is one of the 4 most well-known exotoxin producing pathogens Clostridium tetani is a motile, anaerobic, spore forming bacteria (terminal spores with drum stick appearance) Growth CLOSTRIDIUM TETANI CULTURE ON SHEEP’S BLOOD AGAR MEDIUM CONTAINING 3% AGAR Epidemiology The World Health Organization (WHO) estimates that in 2015, approximately 34,000 neonates died from neonatal tetanus The age groups at highest risk are children and the elderly secondary to reduced immunity Tetanus infection has been associated with: crush injuries injuries with dead tissue burns puncture wounds from piercings, tattoos, injection drug use, or injury (such as stepping on a nail) wounds contaminated with dirt, feces, or saliva  The incubation period of tetanus is approximately 8 days but ranges from 3 to 21 days Typically, spores of the bacteria (C. tetani) enter the body through wounds on the epidermal and dermal layers. Once in the body, the spore starts to germinate followed by the release of toxins into the bloodstream as well as the lymphatic system. symptoms of tetanus (Tetanus toxin) Rigidity or muscle spasms (hyperactivity of muscles) Lockjaw Respiratory failure (as a result of muscle spasm/rigidity) General muscle ache Neuronal inactivation Tachycardia(abnormal rapid heart rate) Diagnosis Doctors diagnose tetanus based on a physical exam, medical and immunization history, and the signs and symptoms of muscle spasms, stiffness and pain. Laboratory tests generally aren't helpful for diagnosing tetanus. Treatment Prevention