20 Anaerobes 1 (Clostridium) Flashcards
T/F
After a stay of two days in a hospital, 10% of patients will develop infection with C. difficile
True
What are general characteristics of anaerobes?
- grow better in anaerobic atmosphere
- lack mechanisms of oxygen metabolism and/or detoxification
- should be considered when signs of infection but aerobic culture negative
What are general characteristics of anaerobe infections?
- Adjacent to surfaces that normally harbor anaerobes as normal flora (e.g. mucosal surface)
- Abscess formation or tissue necrosis
- Putrid odor (fermentation)
- Gas formation
- Polymicrobic infection or organisms that look like anaerobes
What level of blood supply promotes anaerobic growth?
Poor blood supply > low O2 levels
Basic lab characteristics of genus Clostridium?
anaerobic G+ rods
spore formers
Which Clostridium species is non-motile, is a large rectangular rod, and rarely forms spores?
Clostridium perfringens
Which bacterium produces this group of exotoxins? alpha toxin (lecithinase) beta toxin epsilon toxin iota toxin heat-labile enterotoxin collagenase
Clostridium perfringens
What characteristic divides Clostridium perfringens into 5 types?
exotoxins
How does each exotoxin secreted by Clostridium perfringens contribute to disease? alpha toxin (lecithinase) beta toxin epsilon toxin iota toxin heat-labile enterotoxin collagenase
Alpha toxin (lecithinase) - massive hemolysis, increased vascular permeability, tissue destruction, hepatic toxicity, myocardial dysfuntion
Beta toxin - intestinal stasis, necrotizing enteritis
Epsilon toxin - increased vascular permeability of GI wall
Iota toxin - increased vascular permeability, necrosis
Collagenase - penetration deep into tissues -> fulminating gangrene
Heat-labile enterotoxin - no other info
Where is Clostridium perfringens found in the environment? Is it part of the human microbiome?
Spores are in soil and water
Found in the intestinal tract of animals
Yes, found in the intestinal and genito-urinary tracts of humans
What is the cause of Clostridial food poisoning? What form is it ingested in? Symptoms?
Clostridium perfringens
Ingestion of preformed toxin, which inserts in membrane of SI altering permeability -> diarrhea
Watery diarrhea and crampy abdominal pain 8-24 hours post ingestion
What infections/diseases are caused by Clostridium perfringens?
Cellulitis Fasciculitis/suppurative myositis Myonecrosis Anaerobic puerperal sepsis Septic abortions Clostridial food poisoning Necrotizing enterocolitis
What is the mode of infection, complications, and death from Clostridium perfringens soft tissue infections?
- spores germinate and vegetative cells grow in traumatized tissue; degradative enzymes ferment carbohydrates and produce gas in tissue
- bacteria produce necrotizing toxin and hyaluronidase; tissue necrosis extends resulting in incr. bacterial growth, hemolytic anemia, severe toxemia, renal failure, and death
How is a C. perfringens infection diagnosed?
appearance and foul smell, smears showing large G+ rods, spores not usually seen, double zone of hemolysis on blood agar
Which exotoxin is most responsible for causing necrotizing enterocolitis?
beta toxin
What infection(s)/disease(s) are caused by C. difficile? Symptoms?
- pseudomembraneous colitis
- range from non-bloody diarrhea to severe life-threatening pseudomembranous colitis with fever and abdominal cramping
Which bacterium produces this group of exotoxins?
enterotoxin (toxin A)
cytotoxin (toxin B)
C. difficile
How does each exotoxin secreted by Clostridium difficile contribute to disease?
Enterotoxin (toxin A) - stimulates infiltration of PMNs into the ileum -> inflammation
Cytotoxin (toxin B) - glycosylates G proteins involved in actin filament polymerization & depolymerization -> loss of cytoskeletal integrity -> death of enterocytes & inflammation
What is the cause of increased virulence of the hypervirulent strain of C. difficile?
produces increased levels of toxins A & B
How is a C. difficile infection diagnosed?
Isolation from feces and testing for toxins
How is pseudomembranous colitis treated?
Metronidazole
may require surgical repair of intestines and stool transplant
Which Clostridium species is non-motile, is a large rectangular rod, and produces round terminal spores (drumstick/tennis racket bacilli)?
Clostridium tetani
What toxin(s) does C. tetani secrete? What disease symptoms result?
Tetanospasmin (tetanus toxin) - plasmid-encoded heat labile A-B neurotoxin; acts by cleaving neurotransmitter inhibitors resulting in spastic paralysis and muscle spasms
What is the mode of infection for neonatal sepsis?
Spores enter via contaminated umbilicus/circumcision
What is the clinical significance of a C. tetani infection?
Incubation period? Mortality rate?
Incubation period 3-21 days (variable)
Death results from compromised breathing (50% mortality)
How is a C. tetani infection diagnosed?
In most cases diagnosed based on signs, symptoms, and patient history
organism rarely cultured from wounds and antibodies/tetanus toxin are not detected in patients
How many doses of vaccine must a patient have received so that no tetanus prophylaxis is not necessary?
What is this prophylaxis
3 or more
Clean minor wounds give tetanus toxoid and metronidazole
All other wounds give tetanus toxoid and tetanus immune globulin
What bacterium produces the most lethal toxin known?
C. botulinum
botulinum neurotoxin
What is the incubation period and symptoms of botulinum toxin ingestion?
12-36 hours after ingestion begins with nausea, vomiting, and bilateral CN impairment
then drooping eyelids, double/blurred vision, difficulty articulating words & swallowing
then paralysis descends to involve muscles of thorax and extremities leading to death from respiratory and cardiac failure
What is the pathogenesis/mode of action of the botulinum neurotoxin?
Synthesized during growth as zinc-endopeptidase (an A-B toxin)
Inactivates proteins regulating ACh release from nerve termini, blocking neurotransmission at synapses and resulting in flaccid paralysis
What is necessary for recovery after the effects of the botulinum neurotoxin?
regeneration of nerve endings (takes months to years)
What is the treatment of botulinum neurotoxin ingestion?
ventilator support, gastric lavage, metronidazole, and injection of trivalent (A, B, E) botulinum antitoxin
How it botulism foodborne intoxication diagnosed?
based on symptoms and past history (organism not usually cultured)
confirm diagnosis with mouse protection test
What is infant botulism? Age affected? Mode of infection? Signs/symptoms?
infected infants 3 weeks-6 months old
preformed toxin not detected in any food - bacterial spores ingested (honey, infant milk powder) and germinate colonizing in intestinal tract
constipation, lethargy with feeding difficulties; followed by marked loss of muscle tone, especially in the head and neck
What are the 3 forms of botulism infection/toxin ingestion?
Foodborne intoxication
Infant botulism
Wound botulism
What is the cosmetic use of a Clostridium species?
C. botulinum toxin A used cosmetically (Botox) to remove wrinkles or as muscle relaxant
T/F
Botulinum vaccine exists
True but immunization of general population not warranted since disease so rare
What other Clostridium species is associated with infections in IUDs and cancer patients?
C. novyi
