Anaerobic Organisms Flashcards
What is an obligate anaerobe?
growth occurs only in an anaerobic environment, absent of oxygen
Describe a STRICT obligate anaerobe
usually not diagnosed with human infections, oxygen is toxic. Diagnosis usually not via culture as difficult for organisms to survive outside in vivo environment
Describe MODERATE obligate anaerobe
These are the cause of human infections. They are able to survive in reduced oxygen environments. These can routinely be cultured in the the labs. They require appropriate transport.
How do anaerobes obtain energy?
fermentation because it does not require oxygen. some can carry out anaerobic respiration where the final electron receptor is something other than oxygen.
What are exogenous anaerobes?
exist outside the body, live in soil, freshwater, and saltwater sediments.
What are endogenous anaerobes?
exist inside the body and live on skin and mucosal surfaces.
what do anaerobic infections generally contain?
a mixture of anaerobic and facultative anaerobic organsims.
What are some examples of exogenous infections
foodborne illnesses, such as botulism and gastroenteritis. Wound infection: tetanus, gas gangrene, crepitant cellulite, benign superficial infections, human and animal bites.
What are some examples of endogenous infections?
bacteremia, meningitis, endocarditis, abscess of an organ, dental infections, intrabdominal abcess, osteomyelitis.
What are some predisposing conditions?
trauma of mucous membranes or skin that decrease blood flow so that there is decreased 02. Conditions that cause vascular stasis: surgery, shock, edema, tissue necrosis
what are macroscopic indications that anaerobes are involved in the infection?
purulent specimen, large quanities of gas or foul odors, black exudate, sulfur granules, necrosis and gangrene.
if an infection continues despite aminoglycoside treatment, then it is an indication for what?
anaerobic culture
What is critical for specimen collection?
selection of the appropriate medium and transport
What are examples of sites that may be contaminated by indigenous flora? are these acceptable?
cervix, decubitis ulcers, stool, vagina, urine, sputum, bronchial washing. not acceptable
What are some examples of acceptable specimens?
synovial fluid, CSF, blood and bone marrow, aspirated exudates, direct lung aspirates, lung tissue, tissue biopsies, suprapubic aspirate.
The best specimen collection…
sterile body sites, aspirates, and tissues. the worst is swabs.
What is an anaerobic chamber?
allows for oxygen free environment, media used for culture stored in this oxygen free environment.
What are the steps involved in specimen processing?
grinding the tissues, centrifuge to concentrate specimens and plate the sediment.
What are the exceptions to antibiotic susceptibility testing (because its not normally performed)
for research purposes, to assist in life-threatening disease, known resistance, persistence of infections, severity of infection.
What antibiotics should be tested/
PCN G, broad-spectrum antipseudomonal PCN, clindamycin, cefotoxin and possibly other cephalopsorins.
How do we create an environment where anaerobes can not grow?
debridement, draining, stop spread, use of antitoxins, hyperbaric oxygen.
Describe the clostridium species?
normal flora of lower GI tract, found in soil, most infections are exogenous sources. Its virulence factors are toxins.
What is clostridium species clinical significance?
botulsim, gas gangrene, tetanus, psuedomenbranous colitis, wounds, abcesses, bactermia, food poisoning and gastroenteritis.
What is clostridium’s gram stain?
gram-positive bacilli (some may stain gram negative). most can produce spores when they are stressed.
Describe clostridium botulinum
widely distributed in soil and water. associated with home canning. its virulence factor is a neurotoxin.
What is clostridium botulinum’s clinical significance?
foodborne: symptoms 1 to 3 days after ingestion. symptoms include blurred vision, dry mouth, constipation, abdominal pain, progressing bilateral weaknes. treatment is an antitoxin. usually seen in infants up to 6 months. they eat honey. “floppy baby syndrome”
Can clostridium botulim cause a problem with wounds?
yes. symptoms usually develop within 4 days. treatment is supportive, antitoxin, and antibiotics.
Where is clostridium botulinum normally identified?
a public health lab
Describe clostridium perfringens
It is the MOST FREQUENTLY isolated clostridium species. it is frequently found in soil which suggest surfaces contaminated with the organism. virulence factor is an ALPHA EXOTOXIN.
What does the alpha exotoxin do?
it lyses things.
What food products can clostridium perfringens be found in?
meat products. incubation is usually 8-24 hours. abdominal cramps, watery diarrhea with no fever, vomitting, self-limiting. NO TREATMENT NECESSARY.
What type of skin infection can clostridium perfringens?
gas gangrene, pain an swelling on infected area within a week. gas formation in the tissue. gram stain will show large rectangular rods with lack of inflammatory cells.
What is the treatment for clostridium perfringens?
debride, excise, or amputation of dead tissue. antibiotic therapy: pcn and clindamycin. hyperbaric chamber.
What is the causative agent of tetanus?
clostridium tetani
What can prevent clostridium tetani?
dtap or td or tdap
What is the antibiotic associated clostridium?
clostridium difficile.
describe clostridium difficile
endogenous or nosocomial (spores in hospital environment)
What is the bactericides fragilis group?
normal flora of the mouth, upper respiratory tract, GI TRACT, urogenital
What is the most common anaerobe isolated in the lab?
bacteroides fragilis
Describe bacteroides fragilis
growth occurs at 48-72 hours, produces beta-lactamases causing PCN and some cephalosporin resistance.
