GENUS: BACILLUS. Genus Features. Gram-positive rods Spore forming Aerobic. Species of Medical Importance. Bacillus anthracis Bacillus cereus

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1 GENUS: BACILLUS Genus Features Gram-positive rods Spore forming Aerobic Species of Medical Importance Bacillus anthracis Bacillus cereus Bacillus anthracis 1. Distinguishing Features Large, boxcar-like, gram-positive, spore-forming rods Capsule is polypeptide (poly-d-glutamate) Potential biowarfare agent causes anthrax, a disease especially prevalent in goats, sheep, and cattle. is a spore former. Spores play an important role in transmission; they can survive in soil or on the skin of animals for years. Spores are either traumatically implanted or inhaled by humans and then taken up by macrophages and transported to regional lymph nodes. The spores germinate into vegetative cells 2. Reservoir animals, skins, soils 3. Transmission: contact with infected animals or inhalation of spores (bioterrorism) 4. Pathogenesis o o Anthrax toxin includes 3 protein components: Protective antigen (B component) mediates entry of LF or EF into eukaryotic cells Lethal factor kills cells Edema factor is an adenylate cyclase (calmodulin-activated like pertussis adenylate cyclase) 5. Diseases o Cutaneous anthrax results from entry of spores into a cut or an abrasion papule papule with vesicles filled with blood or clear fluid (malignant pustules) central necrosis (eschar) with erythematous border often with painful regional lymphadenopathy; fever in 50% o Pulmonary (wool sorter s disease) : Life-threatening pneumonia results from entry of spores into the lungs; cough, fever, malaise, marked hemorrhagic necrosis of the lymph nodes and ultimately facial edema, dyspnea,cyanosis, and shock with mediastinal hemorrhagic lymphadenitis o Gastrointestinal anthrax Rare: Edema and blockage of gastrointestinal tract can occur, vomiting and bloody diarrhea, high mortality 6. Diagnosis

2 o Visualization of the organism in cutaneous lesions or blood shows large, gram-positive rods; spores are absent. o Culture aerobically on blood agar o Toxicity is demonstrated by injecting B anthracis into mice; death occurs in a few days, with large numbers of bacilli in the blood 7. Prevention of anthrax o Infected animals should be killed and buried deeply. Vaccinate animals where outbreaks have occurred o Vaccine for at high risk people (anthrax lab workers, farmers, animal processors, military) Bacillus cereus Spore forming bacterium 2. Reservoir : found in nature 3. Transmission Foodborne, intoxication Major association with fried rice from Chinese restaurants Associated with food kept warm, not hot (buffets) 4. Pathogenesis : Emetic toxin: preformed fast (1 6 hours), similar to S. aureus with vomiting and diarrhea; associated with fried rice Diarrheal toxin produced in vivo (meats, sauces): 18 hours, similar to E. coli; LT: increasing camp watery diarrhea 5. Diseases : gastroenteritis, non-bloody with or without vomiting Clostridium Genus features Gram-positive rods Spore forming Anaerobic Species of medical importance Clostridium tetani Clostridium botulinum Clostridium perfringens Clostridium difficile Clostridium tetani Large gram-positive, spore-forming rods spores are ubiquitous in soil

3 Anaerobes Produces tetanus toxin 2. Reservoir : soil 3. Transmission : Dirty puncture wound Trauma Requires low tissue oxygenation 4. Pathogenesis Spores germinate in the tissues, producing tetanus toxin (an exotoxin also called tetanospasmin). Carried intra-axonally to CNS Binds to ganglioside receptors Blocks release of inhibitory mediators (glycine and GABA) at spinal synapses Excitatory neurons are unopposed extreme muscle spasm One of the most toxic substances known 5. Disease : tetanus (extreme muscle spasm ) Infection follows minor trauma (such as a laceration or puncture) Manifestations include muscle stiffness, tetanospasms of lockjaw and back arching, and short, frequent spasms of voluntary muscles. Death occurs after several weeks from exhaustion and respiratory failure 6. Prevention The toxoid is a component of the DTP vaccine. Its formaldehyde-inactivated toxin. A booster should be given every 10 years; for major trauma, a booster should be given if the patient has not had one within the last 5 years. Boosters should be given to pregnant women to stimulate maternal antibodies that will protect the newborn. Care of wounds: proper wound cleansing and care plus treatment Clostridium botulinum Anaerobic Gram-positive spore-forming rods spores are ubiquitous in soil and are highly resistant to environmental conditions 2. reservoir : soil / dust 3. transmission : foodborne / traumatic implantation 4. pathogenesis : Spores survive in soil and dust; germinate in moist, warm, nutritious but nonacidic and anaerobic conditions (Home-canned alkaline vegetables) Botulinum toxin a) A-B polypeptide neurotoxin (actually a series of 7 antigenically different; type A and B most common) b) Coded for by a prophage (lysogenized Clostridium botulinum).

4 c) Highly toxic d) Heat labile (unlike staph), 10 minutes 60.0 C e) Mechanism of action o Absorbed by gut and carried by blood to peripheral nerve synapses o Blocks release of acetylcholine at the myoneuronal junction resulting in a reversible flaccid paralysis o Floppy baby syndrome (infant with flaccid paralysis) 5. Laboratory diagnosis:the presence of the toxin in food, stool, blood, and vomitus is demonstrable by injection of sample into mice; botulinum antitoxin protects against lethality. 6. Diseases : C botulinum causes two types of infection: A. Food poisoning follows ingestion of the preformed toxin in contaminated food. Clinical findings include nausea, vomiting, dizziness, double vision, swallowing and speech problems, muscle weakness, respiratory paralysis, and death (in 20% of cases). B. (infant) botulism occurs in infants after spore ingestion and subsequent germination in the gastrointestinal tract. The exotoxin disseminates, causing constipation, generalized weakness, and loss of head and limb control (resulting in a floppy appearance). 7. Prevention Give antitoxin to all persons who ate contaminated food, even if symptoms have not developed Heat food to C آCâ 100 آ 80 for 10 minutes to inactivate the toxin (but not the spores). Use proper sterilization techniques for home canning Refrain from giving honey, which may contain organisms, to infants younger than 1 year of age. Clostridium perfringens Large gram-positive, spore-forming, anaerobic rod. Anaerobic: stormy fermentation in milk media Double zone of hemolysis has soil as a natural habitat; contamination can occur in home-canned goods, smoked fish, and honey requires germination of spores and emergence of vegetative cells for toxin production. 2. Reservoir : soil and human colon 3. Transmission : foodborne and traumatic implantation 4. Pathogenesis : Spores germinate under anaerobic conditions in tissue. Vegetative cells produce Alpha toxin (phospholipase C) is a lecithinase. It disrupts membranes, damaging RBCs, platelets, WBCs, endothelial cells massive hemolysis, tissue destruction, hepatic toxicity Identified by Nagler reaction: egg yolk agar plate one side with anti- α- toxin; lecithinase activity is detected on side with no antitoxin. Twelve other toxins damage tissues

5 Enterotoxin produced in intestines in food poisoning: disrupts ion transport watery diarrhea, cramps (similar to E. coli); resolution 5. Diseases : Gas gangrene (myonecrosis) following severe trauma o Contamination of wound with soil or feces o Acute and increasing pain at wound site o Tense tissue (edema, gas) and exudate o destruction of traumatized tissue and surrounding healthy tissue o Systemic symptoms include fever and tachycardia o progresses rapidly to shock and renal failure o Rapid, high mortality People at risk of gas gangrene o Gunshot o car and industrial accidents o motorcycle accident o compound fractures food poisoning a) Enterotoxin production in gut; self-limiting noninflammatory, watery diarrhea b) Reheated meat dishes, organism grows to high numbers; 8 24 hour incubation c) abdominal pain with severe cramps and diarrhea occur for 1 day 6. prevention extensive debridement of the wound antibiotics Clostridium difficile 1. distinguishing features gram-positive, spore-forming, anaerobic rod a component of the normal intestinal flora of infants and some adults contamination of hospitals and hospital personnel persists via asymptomatic carriers. 2. Pathogenesis Toxin A: enterotoxin damaging mucosa leading to fluid increase; granulocyte attractant Toxin B: cytotoxin: cytopathic toxin that kills mucosal cells 3. Diseases : Antibiotic associated diarrhea also called pseudomembranous colitis and follows antibiotic therapy to treat other bacterial infections. Antibiotic treatment kills organisms that normally restrict growth of C difficile, resulting in overgrowth of the latter 4. Diagnosis Culture is not diagnostic because organism is part of normal flora The presence of exotoxins in the filtrate of a patient's stool specimen is the basis of the laboratory diagnosis cytotoxicity test. In the cytotoxicity test, human cells in culture are exposed to the exotoxin in the stool filtrate and the death of the cells is observed.

6 This test is more sensitive and specific but requires 24 to 48 hours' incubation time enzyme-linked immunosorbent assay (ELISA) using known antibody to the exotoxins. The ELISA tests are rapid but are less sensitive than the cytotoxicity test Important Features of Pathogenesis by Clostridium Species Organism Disease Transmission Action of toxin Clo. tetani Tetanus Spores in soil Blocks enter wound release of inhibitory transmitters, e.g., glycine Prevention Toxoid vaccine Clo. botulinum Botulism Exotoxin in food is ingested Blocks release of acetylcholine Proper canning; cook food Clo. perfringens Clo. difficile Gas gangrene Food poisoning Pseudomembranous colitis Spores in soil enter wound Antibiotics suppress normal flora Lecithinase Cytotoxin damages colon mucosa Proper wound debridement and food cooking Appropriate use of antibiotics Gram-positive, non spore forming rods Listeria Genus features Gram-positive, non spore forming rods Facultative intracellular Tumbling motility Listeria monocytogenes Small gram-positive rods arranged in V- or L-shaped formations Beta hemolytic, nonspore-forming rod on blood agar Tumbling motility in broth Facultative intracellular parasite

7 Cold growth 2. Reservoir : Widespread: animals (gastrointestinal and genital tracts), unpasteurized milk products, plants, and soil Cold growth: soft cheeses, deli meats, cabbages (coleslaw), hotdogs. so storage of contaminated food in the refrigerator can increase the risk of gastroenteritis 3. Transmission Foodborne o ingestion of unpasteurized milk products o undercooked meat o raw vegetables o Contact with domestic farm animals and their feces vertical, or across the placenta 4. pathogenesis Listeriolysin O, a β-hemolysin: which allows it to escape from the phagosome into the cytoplasm, thereby escaping destruction in the phagosome 5. Diseases Listeriosis (human, peaks in summer) o Healthy adults and children: generally asymptomatic or diarrhea with low % carriage o Pregnant women: symptomatic carriage, septicemia characterized by fever and chills; can cross the placenta in septicemia. Neonatal disease o Early-onset: in utero transmission; sepsis with high mortality; disseminated granulomas with central necrosis o Late-onset: 2 3 weeks after birth from fecal exposure; meningitis with septicemia In immunocompromised patients o Septicemia and meningitis (most common clinical presentation) o renal transplant patients and adults with cancer 6. Diagnosis Blood or CSF culture CSF wet mount or Gram stain 7. Prevention Pasteurization of milk and dairy products Pregnant women should avoid cold foods Genus CORYNEBACTERIUM Genus features Gram-positive rods Non spore forming Aerobic Species of medical importance Corynebacterium diphtheria

8 Diphtheroids (normal flora) Corynebacterium diphtheria Gray-to-black colonies of club-shaped gram-positive rods arranged in V or L shapes on Gram stain Granules (volutin) produced on Loeffler coagulated serum medium stain metachromatically Aerobic, non spore forming Toxin-producing strains have β-prophage carrying genes for the toxin (lysogeny, β-corynephage). The phage from one patient with diphtheria can infect the normal nontoxigenic diphtheroid of another person and cause diphtheria. 2. Reservoir : throat and nasopharynx 3. Transmission : bacterium or phage via respiratory droplets 4. Pathogenesis : o Organism not invasive; colonizes epithelium of oropharynx or skin in cutaneous diphtheria o Diphtheria toxin (A-B component) inhibits protein synthesis by adding ADP-ribose to eef-2 o Effect on oropharynx: Dirty gray pseudomembrane (made up of dead cells and fibrin exudate, bacterial pigment) o Extension into larynx/trachea obstruction o Effect of systemic circulation heart and nerve damage 5. Diseases diphtheria (sore throat with pseudomembrane, bull neck, potential respiratory obstruction, myocarditis, cardiac dysfunction, recurrent laryngeal nerve palsy, and lower limb polyneuritis) 6. Diagnosis o Elek test to document toxin production (ELISA for toxin is now the frontline) o Toxin produced by toxin-producing strains diffuses away from growth. o Antitoxin diffuses away from the strip of filter paper. o Precipitin lines form at zone of equivalence Genus 7. Prevention : toxoid vaccine (formaldehyde-modified toxin is still immunogenic but with reduced toxicity. part of DTP, or Td, boosters 10-year intervals