Anaerobic Rods Notes

NOTES NOTES ANAEROBIC RODS MICROBE OVERVIEW ▪ Rod-shaped (bacilli) bacteria, grampositive, strict anaerobes CLOSTRIDIUM BOTULINUM (BOTULISM) osms.it/clostridium-botulinum PATHOLOGY & CAUSES ▪ Ubiquitous presence (esp. soil, water); spore-forming; catalase negative, superoxide dismutase positive, subterminal endospore ▪ Fermentation ▫ Carbohydrates ▪ Obligate anaerobe, can tolerate small amounts of oxygen due to superoxide 316 OSMOSIS.ORG dismutase ▪ Potential bioterrorism weapon ▪ Absorption of toxin into bloodstream → spreads to nervous system → binds to presynaptic receptors → endocytosis → cleavage of SNAP-25 protein → lack of acetylcholine with impaired transduction Virulence factors ▪ Seven distinct types of neurotoxins (A–G) ▫ Type A: most potent

Chapter 56 Anaerobic Rods ▪ Heat-resistant ▫ Toxins enduring temperature of 100ºC/212°F for several hours ▪ H-antigen from flagelle Culture ▪ Chopped meat, glucose, starch medium for isolation; egg yolk agar incubation in anaerobic conditions Disease ▪ Causes disease characterized by muscle weakness, nervous system impairment ▪ Infant botulism ▫ Spores ingestion → germination in gastrointestinal (GI) tract → toxin produced in vivo ▪ Foodborne ▫ Ingestion of botulinum toxincontaminated food ▫ Average incubation period is 12–36 hours ▪ Wound botulism ▫ Wound infection with spores → toxin produced in vivo ▫ Average incubation period is 10 days ▪ Adult intestinal toxemia botulism ▫ Colonization of intestines with toxins production ▪ Iatrogenic botulism ▫ Complication of therapeutic use of botulinum neurotoxins ▪ Enteric infectious botulism ▫ C. botulinum colonizes adult GI tract RISK FACTORS ▪ Infant botulism ▫ Honey consumption in first year of life; ingestion of dust/soil containing C. botulinum spores ▪ Foodborne botulism ▫ Home-canned, improperly preserved food; smoked fish ▪ Wound botulism ▫ IV/subcutaneous drug usage; crush injuries ▪ Enteric infectious botulism ▫ Achlorhydria/other GI diseases → colonization COMPLICATIONS ▪ Sudden infant death syndrome (SIDS), seizures, ileus, death SIGNS & SYMPTOMS ▪ General symptoms precede muscle weakness ▫ Abdominal pain, nausea, vomiting, lack of fever (wound botulism only type with fever) ▪ Cranial nerve impairment ▫ Dilated pupil, ptosis; double vision (due to disconjugate eye movement); ophthalmoplegia; dry mouth, difficulty swallowing; loss of facial expressions ▪ Progressive symmetrical muscle weakness descending from head ▫ Hypotonia, hyporeflexia; floppiness in infants ▫ Respiratory muscles: breathing difficulties ▪ Hyperactivation of autonomic system ▫ ↓ salivation, lacrimation, orthostatic hypotension, obstipation, urine retention DIAGNOSIS LAB RESULTS ▪ Toxin detection/bacteria isolation Enzyme-linked immunosorbent assay (ELISA), mass spectroscopy, polymerase chain reaction (PCR) ▪ Isolation of C. botulinum from feces, vomitus, food OTHER DIAGNOSTICS ▪ History, physical examination Electromyogram (EMG) ▪ Short-lasting motor unit potentials with small amplitude OSMOSIS.ORG 317

TREATMENT MEDICATIONS ▪ IV botulinum immunoglobulin/heptavalent botulinum antitoxin ▫ Manage infection ▪ Antibiotics ▫ Manage secondary infection ▪ Cholinesterase inhibitors OTHER INTERVENTIONS ▪ Manage infection ▫ Debridement, irrigation of wound ▫ Colon cleansing (enema, cathartics) ▪ Nasogastric tube (feeding), Foley catheter (urinary retention), intubation/mechanical ventilation Prevention ▪ Pentavalent-botulinum-toxoid (PBT) vaccine ▫ Five dose vaccination with booster dose once per year CLOSTRIDIUM DIFFICILE (PSEUDOMEMBRANOUS COLITIS) osms.it/clostridium-difficile PATHOLOGY & CAUSES ▪ Ubiquitously present, can be part of “normal” flora; subterminal endospore; motile ▪ Intestinal microbiota disturbance → infection, colonization of gut → produces A, B toxins → binds to receptors on intestinal wall → internalization → fusion with lysosome → toxins exit endosome → damage of cytoskeleton → cell apoptosis → inflammatory response with accumulation of inflammatory cells, fibrin, dead cells → formation of membrane-like structure (pseudomembrane) Virulence factors ▪ Enterotoxin A (TcdA), cytotoxin B (TcdB), H-antigen from flagelle Culture ▪ Agar with cycloserine, cefoxitin, fructose ▪ C. difficile-associated colitis combined with formation of pseudomembranous plaques Transmission ▪ Fecal-oral route by ingestion of spores 318 OSMOSIS.ORG RISK FACTORS ▪ Antibiotic exposure ▫ Disturbance of intestinal microbiota ▪ Previous hospitalization ▫ ↑ risk for infection ▪ Children with neutropenia ▫ More prone to common bacterial infections requiring antibiotics → disturbance of intestinal microbiota ▪ Gastric acid suppression, > 65 years, comorbidities COMPLICATIONS ▪ Multiple relapses, dehydration (due to excessive diarrhea) GI complications ▪ Toxic megacolon (due to inflammation damaging muscularis propria, underlying neurons); ileus; colon perforation; intussusception; pneumatosis; ascites; sepsis Extraintestinal complications ▪ Splenic abscess; osteomyelitis

Chapter 56 Anaerobic Rods SIGNS & SYMPTOMS ▪ Watery diarrhea (most common) with mucus/blood ▪ Abdominal distension, cramps ▪ Malaise ▪ Fever DIAGNOSIS DIAGNOSTIC IMAGING Sigmoidoscopy/colonoscopy ▪ Visualization of plaques LAB RESULTS SURGERY ▪ Colectomy ▫ In persons with acute abdomen, refractory colitis, fulminant colitis OTHER INTERVENTIONS ▪ End previous antibiotic use ▪ Second relapse: pulse therapy ▪ Recurrent: biological therapies ▫ Fecal microbiota transplant: transplantation of microbiota from healthy individual ▪ Electrolytes, fluids replacement; appropriate nutrition ▪ Prevention of hospital-acquired infection ▫ Infection control protocol, antibiotic stewardship WBCs ▪ ↑ white blood cells Stool analysis ▪ Presence of blood/mucus ▪ Stool culture ▪ Enzyme immunoassay test ▫ Detection of glutamate dehydrogenase antigen ▪ Toxin detection ▫ Enzyme immunoassay, real-time PCR ▪ Cell culture cytotoxicity assay ▪ Biomarkers ▫ Differentiation between colonization, actual disease; ↑ fecal cytokines, CXCL5, phosphorylated p38 Figure 56.1 The gross pathological appearance of the colonic mucosa in psuedomembranous colitis. TREATMENT MEDICATIONS ▪ Mild disease: oral metronidazole ▪ Severe disease: oral vancomycin ▪ Complications: combination of oral vancomycin, IV metronidazole ▪ Second relapse: oral vancomycin tapered ▪ Recurrent: probiotics OSMOSIS.ORG 319

CLOSTRIDIUM PERFRINGENS osms.it/clostridium-perfringens PATHOLOGY & CAUSES ▪ Ubiquitous in nature, also part of human microbiota; subterminal endospore; nonmotile Virulence factors ▪ Divided into subtypes A–E ▪ Produces 12 toxins ▪ Alpha ▫ Enzyme lecithinase splits lecithin → ↑ vascular permeability → cell destruction ▫ Responsible for gas gangrene, hemolysis ▪ Beta ▫ Formation of selective pores → ↑ permeability with cell destruction ▫ Responsible for enteritis necroticans; deactivated by trypsin ▪ Epsilon ▫ Pores form on cells → destruction ▪ Iota ▫ AB toxin: enzyme (A), binding (B) domain ▫ Destruction of cells through affection of cytoskeleton Culture ▪ Growth on tryptose sulfite cycloserine agar Clostridial gas gangrene ▪ Saprophytic anaerobic bacteria → clostridial gas gangrene due to tissue infection/food poisoning through ingestion ▪ Disease characterized by necrosis, gangrene due to infection of skin, deep tissues ▪ Bacteria produces gas → characteristic crepitation sound during palpitation ▪ Divided into ▫ Traumatic: wound → spore inoculation → bacteria growth in appropriate anaerobic conditions → production of toxins → destruction of fibroblasts, 320 OSMOSIS.ORG blood cells, muscle cells → necrosis of muscles, subcutaneous fat with blood vessels thrombosis ▫ Postoperative: after interventions on intestinal system ▫ Spontaneous: due to immune system weakness/intestinal diseases Food poisoning ▪ Begins 6–24 hours after ingestion ▪ Infection of food with spores → food standing temperature 30–50ºC/86–122°F → development of vegetative form → ingestion of infected food → toxin production → ↓ glucose absorption, ↑ water, sodium, chloride secretion → damage of intestinal epithelium Enteritis necroticans ▪ Inflammation of jejunum, ileum; type of food poisoning in persons who lack trypsin RISK FACTORS ▪ Gas gangrene: begins 1–4 days after infection ▫ Traumatic: injury during war/natural disaster; car crash ▫ Postoperative: GI/biliary surgery; septic abortion ▫ Spontaneous: colorectal adenocarcinoma; neutropenic states (e.g. AIDS, chemotherapy); intestinal diseases ▪ Food poisoning: improper food-handling ▪ Enteritis necroticans: improper nutrition (e.g. too many sweet potatoes); trypsin inhibitors → ascariasis COMPLICATIONS ▪ Disseminated intravascular coagulation; hemodynamic shock, hypotension, renal failure; systemic hemolysis; peritonitis; sepsis; death

Chapter 56 Anaerobic Rods DIAGNOSIS SIGNS & SYMPTOMS Gas gangrene ▪ Two types ▫ Cellulitis: infection of necrotic skin; crepitation sounds ▫ Clostridial myonecrosis: infection, destruction of muscles, adjacent tissue ▪ Paleness, serosanguineous exudate, pain, swelling, tenderness at injury site → color changes to bronze → purple bullae with green/black discoloration due to necrosis ▪ Characteristic sweet odor ▪ ↑ heart rate with low-grade fever Food poisoning ▪ If only toxins ingested ▫ Asymptomatic/diarrhea ▪ If vegetative form ingested ▫ Watery diarrhea without blood/mucus; abdominal cramps, last > 24 hours Enteritis necroticans ▪ Abdominal cramps; diarrhea; vomiting; meteorism (excessive gas production in intestines); blood in stool; fever DIAGNOSTIC IMAGING X-ray ▪ Gas gangrene: detection of gas in softtissue ▪ Enteritis necroticans: small bowel dilatation with presence of gas LAB RESULTS ▪ Gas gangrene: molecular methods for detection of alpha toxins; ELISA, PCR ▪ Food poisoning: detection of toxins in feces; PCR Biopsy ▪ Gas gangrene: necrosis of myocytes, connective tissue with small number of neutrophils OTHER DIAGNOSTICS ▪ Gas gangrene: physical examination; characteristic discoloration, odor, crepitation sound TREATMENT MEDICATIONS ▪ Gas gangrene: antimicrobial therapy (combination of penicillin G, clindamycin) ▪ Enteritis necroticans: penicillin G/ metronidazole; destruction of bacteria SURGERY Figure 56.2 An individual with gas gangrene of the right leg. The causative agent is Clostridium perfringens. ▪ Gas gangrene: removal of dead tissue; hyperbaric oxygen (augments neutrophil, ↓ clostridial exotoxin, spore production); amputation ▪ Enteritis necroticans: resection of necrotic intestinal parts OTHER INTERVENTIONS ▪ Food poisoning: oral/IV rehydration OSMOSIS.ORG 321

CLOSTRIDIUM TETANI (TETANUS) osms.it/clostridium-tetani PATHOLOGY & CAUSES ▪ Ubiquitously present in soil; resistant to chemical/heat disinfection; terminally present endospore; motile ▪ Anaerobic rod causes nervous system disorder (i.e. tetanus) ▪ Injury → infection with spores → development of vegetative form in appropriate anaerobic conditions → production of exotoxins (tetanospasmin) → blood/lymphatic transmission → spread to neurons through neuromuscular junction → retrograde transport to spinal cord → endocytosis into inhibitory Renshaw cell interneurons → exotoxins protease activity cleaves SNARE proteins → block of glycine, gamma-aminobutyric acid (GABA) neurotransmitter-filled vesicles release at neuromuscular junction → overactivation of muscles → muscle spasms Virulence factors ▪ Two toxins: tetanolysin (relatively unknown function); tetanospasmin (responsible for clinical presentation of tetanus) ▪ H-antigen from flagelle Culture ▪ Oxygen-reduced blood agar with anaerobic incubation TYPES ▪ Four types of tetanus ▫ Generalized: affects whole musculature, from head downwards ▫ Localized: affects only area near injury ▫ Cephalic: cranial nerves affected due to head/neck injury ▫ Neonatal: tetanus occurring in neonates via infection of umbilical stump 322 OSMOSIS.ORG RISK FACTORS ▪ Deep puncture wounds with/without splinters, crush injuries, middle ear infections, frostbites, burns ▪ IV/subcutaneous drug abuse ▪ Infected diabetic wounds ▪ Septic abortion ▪ Umbilical stump infection via contaminated instruments, hands, cultural practices (e.g. application of cow dung, ghee) ▪ Lack of vaccination/immunization COMPLICATIONS ▪ Cardiac arrest ▫ Due to ↑ catecholamine levels, brainstem damage ▪ Palsies of phrenic, laryngeal nerves due to toxic effect ▪ Respiratory muscles ▫ Apnea ▪ Vertebral fractures/intramuscular bleeding (due to opisthotonus) SIGNS & SYMPTOMS Generalized ▪ Masseter muscle spasm → trismus/“lockjaw” → severe generalized muscle contractions ▫ Risus sardonicus: characteristic sarcastic-like facial expression due to facial muscles contraction ▫ Opisthotonus: arched back due to contraction of back muscles ▪ Abdominal respiratory muscles, diaphragm: breathing arrest Localized ▪ Weakness, pain of muscles/extremites in proximity of injury ▪ Stiffness of affected muscles occurring in following days, lasting up to few months ▪ May progress into generalized form

Chapter 56 Anaerobic Rods Cephalic ▪ Palsy of facial nerve ▪ Difficulty swallowing ▪ Weakness of extraocular muscles Neonatal ▪ Sucking difficulty in first days of life ▪ Generalization, opisthotonus may occur Sympathetic overactivity ▪ ↑ heart rate, arrhythmias ▪ Agitation, diaphoresis ▪ ↑/↓ blood pressure ▪ Fever ▫ Due to overactivity/superinfection TREATMENT MEDICATIONS ▪ Human tetanus immunoglobulin (TIG)/ intravenous immunoglobulins (IVIG) ▫ Neutralization of toxin ▪ Antibiotics ▫ Penicillin, cephalosporins, tetracyclines, metronidazole, vancomycin ▪ Benzodiazepines ▫ Muscle relaxation, sedation ▪ Muscle relaxants ▫ Pancuronium/vecuronium ▪ Labetalol ▫ Autonomic hyperactivity management OTHER INTERVENTIONS Figure 56.3 This body posture is known as opisthotonus and is caused by the Clostridium tetani toxin. ▪ Active immunization with tetanus/ diphtheria toxoid (Td) ▪ Respiratory support if needed ▪ Prevention ▫ Primary: vaccination at two months of life, with booster doses at 4, 6, 12–18 months, 4–6, 11–12 years (booster doses every ten years later); passive immunization in immunocompromised ▫ Secondary: vaccination, antitoxin after injury ▫ Tertiary: vaccination, antitoxin after tetanus presentation DIAGNOSIS OTHER DIAGNOSTICS ▪ History, physical investigation ▪ Spatula test ▫ Touching oropharynx with spatula causes reflex biting due to masseter spasm EMG ▪ Loss/shortening of silent interval between action potentials with continuous discharge from motor units OSMOSIS.ORG 323

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