Anaerobic Infection & Normal Flora Flashcards
Abscess formation, foul discharge, gas formation, necrosis, and predisposing conditions such as pulmonary aspiration, bowel surg, bad dental hygiene, bites, and trauma are all common features of:
Anaerobic infection
T/F: most anaerobic infections are caused by a single species
FALSE; most anaerobic infections are mixed with multiple anaerobes or facultative aerobes.
Most aerobic infections are due to a single organism.
Most anaerobic infections are caused by/from:
The patient’s endogenous flora!
Bacteroides Fragilis infections (are/are not) penicillin resistant and are found (above/below) the diaphragm.
B. Fragilis infections are penicillin resistant and are found below diaphragm.
Bacteroides Fragilis are what shape
PLEOMORPHIC, but most commonly GM - rods
T/F: Bacteroides Fragilis are found in small numbers within the human large intestine
FALSE: THEY ARE FOUND IN LARGE-ASS NUMBERS 10^11 CFU per gram of poo
T/F: B. Fragilis can resist the bactericidal action of bile
TRUE
B. Fragilis and C. Perfringens together acccount for ___% of anerobic septicemias; ___% of all septicemias are anaerobic.
80%
10%
Extraintestinal infection by B fragilis may result in septicemia as a result of:
Bowel rupture, female genital infections -> abscess following birth, induced abortion, infected IUD
Name the most important anaerobe that is PENICILLIN RESISTANT:
B. Fragilis <- memorize this as penicillin resistant
The majo virulence factor for B. Fragilis is:
Its Capsule. Only encapsulated strains produce abcesses
Prevotella Melaninogenicus is a GM (+/-) ______
GM - rod
This bacterium along with other anaerobes, is a serious cause of periodontal dissease, sometime found in genital infections. Many strains are penicillin sensitive. Its name derives from ‘black pigment’ - hemin, that is required for its growth.
Prevotella melaninogenicus
This gram - rod species has TAPERED ENDS and are VERY THIN, they are penicillin and oxygen sensitive, and important causes of oral infection, lung abcess and abdominal infections
Fusobacterium
This gramm + rod is normal flora in the intestine + vagina, and important for maintaining low pH and preventing growth of pathogens by converting sugar to lactate. It is a non-pathogen. Some strains are used to make yogurt milk etc.
Lactobacillus
An infection by this GM positive branching rod species might be involved in cervico-facial, lung, or abdominal infections with SINUS TRACTS. Its microcolonies would be characterized by yellow SULFUR GRANULES
ACTINOMYCES
This GM + coccus anaerobe grows in chains and is part of normal mouth gut and urogenital flora. It may be found in pleuro-pulmonary, brain abcess, or OBGYN infections.
Peptostreptococcus
Treatment hierarchy for anaerobic infections (7)
- Penicillin! (EXCEPT FOR B. FRAGILIS -> don’t use alone for infection below diaphragm!!!)
- Clindamycin
- new cephalosporins (EFFECTIVE FOR B. FRAGILIS)
- chloramphenicol
- Metronidazole
- Gentamicin+ cefoxitin or + clindamycin for MIXED aerobe/anaerobe infection
- Surgical drainage for any acesses
Bacterial overgrowth in the small bowel can lead to: (2)
- Fat malabsorption
2. Vitamin B12 deficiency
Normal mouth flora:(5)
Viridans Streptococci Neisseria Species Diptheriods Staphlococcus epidermidis Eiknella corrodens
Viridans Streptococci
GM+ cocci in chains. Large numbers - PREDOMINANT organisms of MOUTH. Common cause of SUBACUTE ENDOCARDITIS. Highly adherent to valves and teeth. Turnn sucrose into plaque + make lactate -> cavities.
Diptheroids
Corynebacterium species other than c. diptheriae that are NON PATHOGENIC PLEOMORPHOC GM + rods. found in mouth. Also, MOST COMMON CAUSE OF BLOOD CULTURE CONTAMINATION because they also colonize skin
Staphlococci epidermidisare the major species of ________ negative staphlococci in the oral flora. They appear as GM ____ ____________
Coagulase negative
Appear as GM + cocci in grape like clusters. Along with diptheriods, they are the most common causes of blood culture contamination.
Common anaerobes in oral cavity & sensitivity (4)
- Fusobacterium, penicillin sensitive
- Prevotella, penicillin sensitive
- Streptococci such as petptostreptococcus, penicillin sensitive
- Actinomyces
T/F: anaerobes of the oral cavity (fuso, prevotella, etc) do NOT extend into the lower trachea in healthy individuals.
True!
Gastric achlorhydria
abnormality with no stomach acid -> bacteria CAN proliferate in stomach. Normally bacteria CANNOT be cultured due to the acid.
T/F: the upper small bowel is generally sterile
TRUE. sterility due to rapid movement and peristalsis and unconjugated bile acids. Bacteria may increase here in the event of obstruction.
T/F: the terminal ileum is sterile
False. Normally houses about 10^6 bacteria due to stasis
In the colon there is marked bacterial proliferation; metabolic activity of bacteria results in ammonia, acid, and gas production. HOW IS THE AMMONIA FORMED?
the bacteria split UREA to form protein
Patient ruptures a bowel, what bacteria is a frequent cause of the following intrabadominal infection? What drug should you use?
BACTEROIDES FRAGILLIS is the MOST COMMON species in STOOL.
it is penicillin RESISTANT
USE CLINDAMYCIN, CEFOXITIN, OR METRONIDAZOLE for BELOW THE DIAPHRAGM infections
Establishing flora:
- Fetal
- Born
- And then…
Fetal intestine is sterile
very very very few bacteria @ birth, but intestine is colonized within hours
Flora of breast fed infants = BIFIDOBACTERIUM
Weaning->-> adult like flora
Regarding bile acid, what is the consequence of abnormal bacterial growth in the upper small intestine?
BILE ACID DECONJUGATION: Bacterial growth will convert more conjugated bile acid into FREE BILE ACID, causing fat malabsorption.
What is a hepatic coma and how is it treated
if liver fxn is imparied, blood ammonia levels rise.
Treatment = reducing the normal intestinal flora, because their conversion of protein is a major source of ammonia to the blood.
Intestinal flora are responsible for converting bilirubin to ____ & ______
Urobilin and sterobilin
What is the fate/significance of carbs that are not absorbed by the host?
The carbs are FERMMENTED by intestinal flora, causing a drop in pH; the low pH helps maintain the gut flora.
Normal flora of skin is ~_____ CFU per cm^2 of skin
10^3 - 10^4
What are the 3/4 major normal flora of the skin?
Staph Epidermidis - Predominant, normally non-pathogenic
Staph Aureus skin + nares
Diptheriods
#4 - other anaerobes like proprionibacterium in deep follicles (acnes)
Normal flora of GU tract
Lactobacillus -> responsible for pH in vagina
E. Coli from colon
20% women have Group B streptococcus in vagina too -> newborn sepsis.
