Diphtheria and Clostridium Notes PDF

04/03/2024 21 CORYNEBACTERIUM -Corynebacterium diphtheriae : pathogenic. C. Diphtherae → →pathogenic to man, cause diphtheria Diphtheroids → normal flora in respiratory tract and skin C. Diphtheriae → causes diphtheria Gram Positi...

04/03/2024 21 CORYNEBACTERIUM -Corynebacterium diphtheriae : pathogenic. C. Diphtherae → →pathogenic to man, cause diphtheria Diphtheroids → normal flora in respiratory tract and skin C. Diphtheriae → causes diphtheria Gram Positive Rods Aerobic, Non-sporeforming, Non-motile Arranged in small groups at acute angles or parallel to each other “Chinese letter arrangement” -The bacilli are beaded due to presence of metachromatic volutin granules contain polyphosphate which can be stained by methylene blue or Neisser stain. 24 1  04/03/2024 Clinical significance: 1. Diphtheria. 2. Cutaneous diphtheria. Virulence factor: -The organism produces a powerful exotoxin. Heat Labile, Highly Toxic, and Highly Antigenic -Only lysogenized strains are toxigenic & virulent. Transmission: Respiratory droplet or by contact. Pathogenesis: The organism is not invasive. Causes Local inflammatory condition & toxaemia It colonizes the epithelium of oropharynx or skin in cutaneous diphtheria. The toxigenic strains start to produce toxins. 26 1. The toxin inhibits protein synthesis 2. This leads to inflammation of throat ----- resulting in formation of a greyish- white, adherent pseudo membrane covering the tonsils.--------Any attempt to remove this membrane causes bleeding. 3. This membrane may extend to larynx and cause suffocation ‫ا‬if not rapidly managed by tracheostomy. 4. The toxin also diffuses to the blood stream and affects: a) Heart leading to heart failure. b) Nervous tissue -------leading to paralysis of muscles of the soft palate 28 2  04/03/2024 Diagnosis: 1-Sample: Throat swab from beneath the membrane or swabs from any suspected lesions. 2-Film: 3-Culture: they are catalase +ve a-loffler's serum (enriched media) grayish white or creamy colonies. b-Blood tellurite(selective): grey to black colonies 4-Biochemical reactions: ▪Catalase positive ▪Ferment glucose and maltose with acid production. 29 Toxigenicity testing of C. diphtheriae: 1- Elek’s test (in vitro). the antitoxin diffusing from the filter paper will form ppt lines with the toxin diffusing from the toxigenic strains. 2-ELISA:detection of diphtheria toxin 3-PCR: detection of toxin gene. 30 3  04/03/2024 Treatment 1-Diphtheria antitoxin serum: should be given without waiting for the lab results when there is a clinical suspension of diphtheria. -The antitoxin neutralizes the toxin before it causes irreversible damage. 2-Antibiotics: e.g. Pecinillin and erythromycin. They inhibit growth of organism in throat → reduce toxin production. 31 Prophylaxis: TOXOID can be converted to toxoid by formalin and is neutralized by antitoxin. Diphtheria toxoid combined with Tetanus toxoid and Pertussis killed vaccine in one vaccine "DTP’’ DTP is given IM to children at age of 2,4,6 and 18 months. A booster dose is given at school age or every 10 years, but it should contain diphtheria and tetanus toxoids only because pertussis vaccine may cause encephalopathy if given after 6 years of age. 32 4  04/03/2024 Clostridium (G+ve anaerobic spore forming bacilli) 1- Gram +ve Bacilli 2-Anaerobic ‫ال هوائية‬ 3-Spore forming → Can survive in dust ❖The position of the developing spore is useful in identifying the species. 40 The most important members are 1- Cl. tetani 2- Cl. perfringens 3- Cl. botulinum 4- Cl. difficile 42 5  04/03/2024 I- Clostridium tetani Morphology: Gram +ve bacilli (drum stick appearance) terminal spherical projecting spores (drum stick appearance). Culture: (ANAerobic) 43 2- Neonatal tetanus Disease: Tetanus “lock jaw” Mode of transmission: Wound tetanus = tetanus= Lock jaw: by contamination of deep wound with dust (or soil) containing the spores (ex. contaminated surgical wound, gun shot wound, drug abusers) deep wound Cl tet. Cl tet. 45 6  04/03/2024 Virulence factors and Pathogenesis: At the site of infection, the spores--→ germinate & release a potent neurotoxin “tetanospasmin” which diffuses to CNS and cause excitation of the neurons leading to generalized muscle spasm & spastic paralysis. Signs: - contractions of voluntary muscles including a spasm in the Jaw muscle leading to trismus (Lock jaw), facial spasm & arching of the back due to spasm in the back muscles (opisthotons). -Death occurs due to respiratory or cardiac failure. 49 Treatment: 1-Human tetanus immunoglobulins (HTIG). (AntiToxin) 2- Proper care of the wound. 3-Penicillin or metronidazole (large doses) 4- Respiratory support and Benzodiazepines (e.g. valium) to prevent spasm. DTP Prevention: ‫الوحيدة في عائلة الكلوستريديم اللي ليها تطعيم‬ 1-Acitve immunization: by tetanus toxoid which is given in combination with diphtheria toxoid and pertussis (DPT) in 3 doses IM at 2, 4, 6 months. Pregnant women should receive 2 doses of tetanus toxoid to stimulate IgG production which cross the placenta and protect from neonatal tetanus. 52 7  04/03/2024 II-Clostridium botulinum Mode of transmission: botulism has 3 clinical forms oval subterminal spores Virulence factor: The organism produces a potent neurotoxin that inhibits the neurons leading to → flaccid paralysis. 56 Mode of transmission: it Causes botulism which has 2 clinical forms 1-Wound botulism: as tetanus leading to→ flaccid paralysis. 2-Classical botulism: it is a type of food poisoning that results from ingestion of inadequately sterilized canned food (meat, fish or alkaline vegetables as beans). -Canning provides anaerobic conditions for multiplication of organism and production of exotoxin → that causes flaccid paralysis. -Death results from respiratory or cardiac failure 3-Infant botulism ”floppy child syndrome” Note: Botox is a preparation of the Cl botulinum neurotoxin used to remove wrinkles of the face. 63 8  04/03/2024 Treatment: 1. Antitoxin: The antitoxin is only effective if give within the 12 hr after ingestion to bind to the toxin before in binds the neuromuscular junction. 2. Respiratory support. Prevention: 1-Careful sterilization of food before canning. 2-Swollen cans should be discarded. 64 III-Clostridium perfringens Morphology: Gram +ve large bacilli, with oval sub-terminal non projecting spores. Disease: -It causes Gas Gangrene (myeonecrosis) (It is a bad smelling wound). Mode of transmission: by contamination of deep wound with dust (or soil) containing the spores 66 9  04/03/2024 Virulence factors and Pathogenesis: Spores germinate under anaerobic condition in tissues produce vegetative cells which produce many toxins that damage tissues, 1-Alpha toxin: lecithinase enzyme causes cell death necrosis. 2-Theta toxin: a haemolytic effect cause necrosis 3-Spreading enzymes ( Hyaluronidase, collagenase, Dnase) 4-Some strains produce enterotoxin: cause food poisoning. 68 Pathogenesis: - organism multiplies and ferment sugars producing large amounts of gas which distends the tissue and interferes with the blood supply leading to necrosis. -Necrotizing toxin, collagenase and hyaluronidase favor necrosis and spreading of infection. -Proteolytic organisms digest the dead tissues leading to change in color and foul odor of the wound. -The condition is accompanied by generalized toxemia, shock and death. 69 10  04/03/2024 Diagnosis: 1-sample: wound exudate 2-fim 3- culture 4-BR: a-Sugar fermentation → acid and large amount of gas b-Stormy clot reaction C-Nagler’s reaction: lecithinase enzyme → Opalescence on Egg yolk medium 70 Treatment: 1-Surgical debridement and removal of foreign material. Amputation ‫بتر‬may be needed. 2-Penecillin and metronidazole. 3-Hyperbaric oxygen chamber. Prevention: No vaccine Proper cleaning of contaminated wounds, removal of foreign bodies and administration of antibiotics. 71 11  04/03/2024 IV-Clostridium difficile -It is present in the intestine of 30% of hospitalized patients (carriers). Disease: It causes antibiotic-associated diarrhea or pseudo-membranous colitis. Pathogenesis: -Cl difficile is a minor component of the normal flora of intestine. -During antibiotic treatment (ex.by Clindamycin and broad spectrum antibiotics)→ the sensitive normal flora are killed → this allows Cl.difficile to overgrow and multiply and produce: a) exotoxin A (which is an enterotoxin that causes diarrhoea) and b) exotoxin B (which is a cytotoxin) that kills colonic mucosal cells →leading to colitis pseudomembrane formation. Treatment: 1- Stop the causing antibiotic. 2-Fluid and electrolyte replacement. 3-Use vancomycin or metronidazole which is preferred to avoid Vancomycin resistant enterococci (VRE). 74 79 12