Gram Positive Anaerobes Flashcards
Which gram positive anaerobes form spores?
Clostridium Species (Perfringens, Tetani, Botulinum, Difficile)
What diseases can C.Perfringens cause?
Gas Gangrene
Intraabdominal infections
Food poisoning
Describe the structural features of C.Perfringens
Gram Positive Non Motile Encapsulated Spore Forming Double zone hemolysis
How does gas gangrene arise?
Requires injury/trauma -> spores and C.Perfringens get int and germinate -> effects via toxins
What are the toxins of C.Perfringens?/
a-toxin: lecithinase ; PLC; lyses inflammatory cells and tissues
B-toxin: enteritis necroticans
i toxin: necrosis and vascular permeability
e-toxin: systemic vascular permeability
What characteristic lesions are found in gas gangrene?
Bullae -> full of liquid -> will find gram positive box-car organisms but NO WBCs
What is the clinical presentation of gas gangrene?
Rapid onset Necrosis of skin and muscle Tense edema Bullae Gas formation => CREPITUS
Can lead to shock
How is gas gangrene diagnosed?
Clinical setting and history
Gram stain/culture
How is gas gangrene treated?
DEBRIDEMENT + Abx (Penicillin, B-lactam inhibitor)
Can also add Clindamycin to shut down toxin production while treatment given
What causes C.Perfringens food poisoning?
Heat resistant spores survive -> produce enterotoxin after germination -> nausea, abd pain, diarrhea within 24 hours after ingestion
How is C.Perfringens associated food poisoning treated?
Diagnosed clinically, no culture needed
Tx: Self limiting, just supportive therapy
How are C.Tetani and C.Perfringens different?
C.Tetani:NO Gas gangrene
local germination without necroses
What is the main toxin produced by C.Tetani and what does it do?
Tetanospamin- neurotoxin
Blocks post synpatic inhibition of spinal motor reflexes leading to uninhibited spasmotic contractions
What do C.Tetani look like in culture and stain?
they LOOK gram neg but are GRAM POSITIVE
Look like mini tennis raquets
What is the general clinical presentation of C.Tetani infection?
Trismus- lockjaw
Risus Sardonicus- inc tone of orbicularis oris
Opisthotonus: arm/leg flexion/extension
Respiratory- obstructioin due to diaphragm spasms
How do we take care of pts with spastic contractions in C.Tetani infecitons?
Support with respiratory help and monitoring until synapses reform (it is a permanent inhibition) -> takes weeks to months
How is tetanus diagnosed?
Clinical presentation
How is tetanus treated?
Human tetanus Ig
Control spasms
Supportive airway
How can tetanus be prevented?
3 doses of DPT for prophylaxis every 10 years
Passive immunity for people without previous vaccination
Where is C.Botulinum commonly found?
Home canned foods
How is botulism different from tetanus?
Botulism: we have paralysis (flaccid) rather than overstimulation/spasm
What causes botulinum in adults?
Preformed toxin in contaminated foods
What causes botulinum in children/infants?
Spores in honey that germinate once inside the baby
What are the characteristics of the C.Boutlinum toxin?
Bacteriophage born
Blocks release of Ach at synapse - permanent damage!
Descending Paralysis
Heat labile
How is the paralysis seen in botulinum different from that in Guillen Barre?
Botulinum: descending paralysis
Guillen Barre: Ascending paralysis
What is the clinical presentaiton of botulism?
GI: nausea, dry mouth, diarrhea
Flaccid Descending paralysis
Wound Botulism: local paralysis
How is botulism diagnosed?
Clinical history and presentation
Toxin Assay from serum, stool, food
What is in the DDx of botulism?
Botulism Myasthenia Gravis Eaton Lambert Tick PAralysis Guillen Barre
How can botulism be prevented./treated?
Avoid contaminated food
Adequate heating of food
Antitoxin
Supportive
Where is C.Diff infections mostly found?
Spores are acquierd in hospital
What precedes C.Diff infections usually?
Antibiotic therapy
Just ingestion is not enough-> abx kills off normal flora-> C.Diff proliferates then
What does Toxin A of C.Diff cause?
Enterotoxin: inflammatory response -> diarrhea
What does Toxin B of C.Diff cause?
Cytotoxic effects
What else can C.Diff cause besides diarrhea?
Diffuse hemorrhagic colitis
Pseudomembrane formation
How is C.Diff clinically presented?
Diarrhea Pseudomembrane colitis Abd Pain Leukocytosis Fever Toxic Megacolon
Why do we see leukocytosis with C.Diff?
Inflmmatory reaction in gut -> high white count
What can happen with C.diff associated toxic megaocolon?
Dilation-> can lead to perforation and pt can die without intervention
Which strain of C.Diff is associated with higher mortality and increased Toxin A production?
BI/NAP1 Strain: dominant strian in US
How is C.Diff diagnosed?
ELISA: Detect toxin A in stool
PCR: standard
Sigmoidoscopy/Colonoscopy
How is C.Diff treated?
Mild: Oral Metroinidazole, oral vancomycin
Relapsing C.Diff: Fidaxemicin
Fecal Transplat?
Colon resection
What are 2 other pathogenic clostridium species besides perfringens, tetani, botulinum, and difficile?
C.Septicum
C.Sordelli
Describe Actinomyces
Non spore forming Gram positive rod Filamentous hyphae Forms sulfur granules Neg Acid Fast Slow growing
How are actinomyces and nocardia different?
Nocardia: Acid fast positive, aerobic
Actinomyces: Acid fast negative, anaerobic
How are actinomyces presented clinically?
Orally associated (LOCK JAW) Cervicofacial
How is actinomyces treated?
Penicllin: Clindamycin or Erythromycin
What is propionobacterium acnes?
Slow growing anaerobe
Opportunistic infections
Found on prosthetic device or hardware
Commonly contaminant in blood cultures
What is the treatment for Propionobacterium acnes?
Penicillin
NO METRONIDAZOLE
Which species of bacteria are anaerobic gram positive cocci?
Peptostreptococcus
Where is peptostreptococcus found?
Normal flora of mouth, GI, pelvis
What can peptostreptococcal infections cause?
Brain abscess
How is peptostreptococcal infections treated?
Debridement and penicillin
