anaerobic gram-negative bacteria

Question 1

anaerobic gram-negative bacteria metabolism

Answer 1

obligate anaerobes are incapable of using oxygen as a final electron acceptor; depending on the species, the bacteria may have variable tolerance to survive in the presence of oxygen for short periods of time

Question 2

anaerobes

Answer 2

the predominant bacteria microbiota on the mucous membranes of the human upper respiratory tract, gastrointestinal tract, and genitourinary tract; the majority of anaerobic infections are caused by microbiota that become opportunistic pathogens

Question 3

pathogenesis of anaerobic gram-negative infections

Answer 3

infection with anaerobes occurs in settings of reduced oxidation-reduction potential in tissues that are normally well-oxygenated and therefore resistant to invasion by anaerobes; caused by impaired blood supply, tissue necrosis, etc.

end result - localized tissue destruction and inflammation

Question 4

how to anaerobic microbiota gain access to desirable environments?

Answer 4

through breaks in the mucosal epithelium; caused by surgery, trauma, cancer, etc.

Question 5

clinical characteristics of anaerobic infecitons

Answer 5

• foul-smelling discharge
• infection is close to mucosal surfaces
• tissue necrosis
• infeciton related to the use of antibioitcs that have poor –activity against anaerobes (e.g. aminoglycosides)
• infection following human or animal bites

Question 6

bacteroides species

Answer 6

obligate anaerobes

Question 7

bacteroides epidemiology

Answer 7

opportunistic pathogens; b. fragilis is the major inhabitants of the human colon; in this location they are beneficial to the host (mutualistic relationship)

Question 8

bacteroides pathogenesis

Answer 8

bacteroides species will cause disease if they access areas of the body where they do not belong; they may invade body tissue through wounds in the intestinal mucosa (cancerous lesions, surgical wounds, etc.)

once they are in the body tissue, the bacteria form an abscess; a localized mass of bacteria and pus contained in a cavity of dead tissue

the interior of the abscess in anaerobic and generally impenetrable to antibiotics

Question 9

bacteroides virulence factors

Answer 9

capsule (antiphagocytic)

fimbriae (allows for adherence to host epithelium)

lipases, proteases, collagenases - allow for tissue destruction and ultimately abscess formation

b-lactamase -hydrolyzes the beta-lactam ring in penicillin

Question 10

bacteroides culturing

Answer 10

culture the organism on bile-esculin agar; if the specimen contain bacteroides, the media will become dark brown in areas surrounding bacterial growth

Question 11

prevotella species

Answer 11

obligate anaerobes

Question 12

prevotella epidemiology

Answer 12

opportunistic pathogen; prevotella species colonize the human mouth, vagina, and gastrointestinal tract

Question 13

prevotella pathogensis

Answer 13

prevotella species may cause disease if they access areas of the body where they do not belong; they may penetrate the mucosal epithelium and establish an infection nearby

Question 14

prevotella virulence factors

Answer 14

capsule
IgA, IgM, IgG proteases - hydrolyzes antibodies
collagenases - allow for tissue destruction
beta-lactamase - hydrolyzes the beta-lactam ring in penicillin

Question 15

prevotella diseases

Answer 15

abscesses, aspiration pneumonia, bacteremia, wound infections, UTIs, periodontitis

Question 16

fusobacterium

Answer 16

obligate anaerobes

Question 17

fusobacterium epidemiology

Answer 17

opportunistic pathogens; colonize the human mouth, vagina, and GI tract

Question 18

fusobacterium pathogenesis

Answer 18

may cause disease if they access areas of the body where they do not belong; they may penetrate the mucosal epithelium and establish an infection nearby

Question 19

fusobacterium virulence factors

Answer 19

capsule
leukotoxin - destroy WBCs
hemolysins - lyse red blood cells
hemagglutinin - facilitate attachment to host cells
phospholipase C - mediates host tissue destruciton
beta-lactamase

Question 20

fusobacterium diseases

Answer 20

lemierre syndrom - complication of a throat infection that leads to inflammation of the internal jugular vein

peritonisllar abscess

bacteremia

intra-abdominal infections

pulmonary infections

wound infections

Question 21

porphyromonas species

Answer 21

obligate anaerobes; most common species to cause disease in humans (p. gingivalis)

Question 22

porphyromonas gingivalis epidemiology

Answer 22

opportunistic pathogens; colonizes the mouth (resides below the gingival surface), respiratory tract, and GI tract

Question 23

p. gingivalis pathogenesis

Answer 23

a member of the “red complex”

below the gingival surface, along with other microorganisms, it creates a biofilm; this shifts the balance of the species that are found in a healthy vs. diseased subgingival space; gram-negative bacteria accumulate; the host responds with inflammation resulting in detachment of the gums from the teeth

Question 24

p. gingivalis virulence factors (FOUR)

Answer 24

capsule
fimbriae
collagenases
beta-lactamase

Question 25

p. gingivalis disease

Answer 25

chronic adult periodontitis

Question 26

preventing and managing anaerobic infections

Answer 26

these organisms are part of our microbiota so it is difficult to prevent opportunistic infections caused by the endogenous spread of these anaerobes; avoid conditions that reduce the oxidation-reduction potential of the tissues (tissue with impaired blood supply, necrotic tissue); attempt to prevent the introduction of anaerobic microbiota into wounds or closed cavities

when the natural barrier around the mucosal surfaces are disrupted, prophylactic treatment with antibiotics may be recommended

treatment with antibiotics that are intrinsically ineffective against anaerobes (such as aminoglycosides) can exacerbate the infection

since anaerobes typically flourish within an abscess which antibiotics cannot penetrate, treatment generally requires surgical intervention