CH.6 Bacteria - Gram Positive Rods

Corynebacteria Diphtheria

• Caues: Diphtheria

• Transmitted: respiratory aerosol ( asymptomatic carriers/actively infected ppl) & leads to: pseudomembrane in pharynx

• Causes: resp obstruction 

• Organism: produce potent exotoxin can cause

• Myocarditis, Neurological effects, Peripheral vascular collapse 

• Diphtherotoxin: 2 part exotoxin 

• Part B binds & induce endocytosis

• Part A stops protein synthesis 

• Reservoir formed - asymptomatic human carriers (potential always present)

• Virulence factors: assist - attachment & growth 

Corynebacterium Diphtheria - Epidemiology & patho

 

• Most cases in non vax children in crowded & unsanitary conditions

• 2 stages of disease:

• Local infection - upper resp tract inflam (sore throat, nausea, vomiting, swollen lymph nodes, pseudomembrane - asphyxiation 

• Diphtherotoxin production & toxemia - target organs (heart & nerves)

Corynebacterium Diphtheria - Treatment

• Antitoxins, Penicillin/erythromycin,

• Prevention: toxoid vaccine series & booster

Genus Bacillus

• Endospore form, motile rods in soil 

• Saprohytes & versatile in breakdown macromole

• 2 species: bacillus anthracis, cereus - antibiotic source 

Bacillus Anthracis

• Cause: Anthrax

• Found: Soil

• Produces: Trough (environmentally resistant endospores)

• Transmitted: Animals to humans

• Virulence factors: Polyp capsule & exotoxin

Bacillus Anthracis - 3 types

• Cutaneous: affects skin, spore enter skin, black sore -eschar, lower mortality (least dangerous)

• Pulmonary: inhalation of spores & increases anthrax exotoxin production → cardiovascular shock (80% mortality)

• Needs v high ID (>10000 spore)

• Present w/ serve resp infection sympt (high fever & chest pain), hemorrhagic mediastinitis → septicemia 

• Gastrointestinal: ingested spores 

Bacillus anthracis - Treatment & Control

• Penicillin, tetracyclin, ciprofloxacin 

• Vaccines 

• Live spore & toxoid - protect livestock 

• Purified toxoid - increased risk occupation & military 

Bacillus Cerus

• Airborne & dustborne - usual disinfection & antisepsis ineffective

• Grow: food, spore survive in cooking & reheating

• Ingestion: nausea, vomiting, ab cramp & diarrhea - 24hr duration

• No treatment (↑ report - immunosupressed)

Clostridia - Clostridium

• Found: soil 

• Release exotoxins

• Spore forming, anaerobes & thrive deep tissues

• Synthesize organic acids, alc, exotoxins 

• Cause: wound, tissue, food intoxication/infection

Clostridium Perfringens

• Most freq in: soft tiss & wound infect

• Can progress suddenly - septic shock & death 

• Lead: tissue destruct - eg: myonecrosis & gas gangrene

• Associated/Pre-dispose factors: septic abortion, crushing injuries, compound fractures, gunshot & knife wounds, malignancies 

• Spores found: soil, human skin, intestine, vagina 

Clostridium Perfringens - Virulence Factors

Toxins

• Alpha (RBC rupture, edema & tissue destruct)

• Collagenase

• Hyaluronidase

• DNase

Clostridium Perfringens - Pathology

• Not highly invasive - need damage & dead tiss in no O2 condition 

• Condition: stim spore germ, veg growth & rel. exotoxins & other virulence factors

• Fermentation: muscle carbs → gas form & more tiss destruct

Clostridium Perfringens - Treatment

• Immediate cleaning: dirty, deep wounds, decubitus ulcers, compound fractures & infected cuts 

• Removing dead tissue

• Large dose: cephalosporin, penicillin 

• Hyperbaric O2 therapy 

• No vaccines 

Clostridium difficile associated disease (CDAD)

• Normal resident: colon (low #)

• Cause: Ab asso colitis 

• Non-invasive, treatment w/broad spectrum ab kills other bacteria - C.diff overgrow

• Prod: enterotoxins → damage intestines 

• Major diarrhea cause - hospital

Clostridium difficile associated disease (CDAD) - Treatment

• Mild & uncomplicated: fluid & electrolyte replace & w/drawl of antimicrobials 

• Severe infections: oral vancomycin/ metronidazole & replace cultures 

• More precautions 

Clostridium Botulinum 

• Cause: food poisoning - esp where bacteria can enter into low O2 environment thru bent/cracked cans 

• Botulinum toxin (exotoxin): most toxic subs & can cause death - resp failure 

Clostridium Botulinum - Pathogenesis

• Spores: on food - gathered & processed 

• Reliable temp & press not achieved = air evacuated spores stay

• Anaerobic conditions: favour spore germ & veg growth 

• Botulin rel → carried to NMJ → binds to presynaptic cholinergic nerves → blocks acetylcholine (need for muscle contract) → paralyze skeletal muscle x2 / blurry vision, difficulty swallowing, NM symptoms 

Clostridium Botulinum  - 2 types

Infant Botulism: Caused by ingested spores: germ & rel toxin (flaccid paralysis)

Wound: Spore enter wound → food poison symptoms

Clostridium Botulinum - Treatment

• Determine: toxin in food, intestinal content/feces 

• Antitoxin, cardiac & resp support

• Treat w/ penicillin (infection)

• Preserve & handle canned foods properly 

Clostridium Gastroenteritis 

• Spore: contam food not cook thoroughly enough to kill them

• Germinate & multiple (if refrigerated)

• Consumed: toxin made in intestine → act on epithelial cells, acute ab pain, diarrhea, nausea

• Rapid recovery 

Clostridium Tetani

• Cause agent: Tetanus - lockjaw (NM disease)

• Found: Soil & G.I tract - animals (resident)

• Cause infection after enter thru break in skin (cuts/penetrating wounds)

• C. tetani produce exotoxin (tetanospasmin) → target NMJ terminal synapse →binds to motor nerve endings→ inhib glycine & GABA rel → spastic parlysis 

• Eventual: resp muscle paralysis - suffocation

• Most common: older pt & IV drug abusers & neonates (devel countries)

Clostridium Tetani - Pathology

• Spores: enter → accidental puncture wounds, burns, umbilical stumps, frostbite, crushed body parts 

• Anaerobic environment ideal → veg cells → grow & rel toxin

Clostridium Tetani - Treatment

• Aim: deter degree of toxemia & infection & maintain homeostasis

• Antitoxin therapy w/human tetanus immune glpbunin → inactivate: circulating toxin & does not counteract things already bound (ok queen)

• Control w/ penicillin/tetracycline & muscle relaxants 

• Vaccines - ~10 year booster 

Listeria Monocytes

• Non spore forming 

• Cocobacilli

• No capsule 

• Resist: cold, heat, salt, pH extremes & bile 

• Virulence: ability to replicate in cell cytoplasm after phagocytosis induce → avoids humoral immune system 

Listeria Monocytes - E & P

• Prime reservoir: soil & water, animal intestines 

• Can: cont food & grow (refridge)

• Listeriosis: most asso w/ dairy, poultry & meat

• Adults: Mild/subclin

• Immunocompromised pt, fetus, neonates: affect brain & meninges (20% death rt)

Listeria Monocytes - Treatment

• Culture: needs long & cold enrichment process

• Rapid diagnostic test w/ELISA

• Ampicillin & trimethoprim sulfamethoxazole

• Prevent: pasteurization & cooking