Anaerobes, Bacteroides, others Flashcards
Why do Anaerobe (except Clostridium) infections have facultative anaerobes too?
the facultatives use up the oxygen, then the strict anaerobes take over
do Anaerobes (except Clostridium) produce spores
no
Name the Clinically significant nonspore-forming Gram (-) rods anaerobes (4)
Gram (-) rods - Bacteroides, Prevotella, Porphyromonas, Fusobacterium
Name the Clinically significant nonspore-forming Gram (+) cocci anaerobes (1)
Gram (+) cocci – Peptostreptococcus
Name the Clinically significant nonspore-forming Gram (+) rods anaerobes (1)
Actinomyces
When do infections by Clinically significant nonspore-forming anaerobes occur? (4)
• Infections occur when:
- there has been a breach in integrity of body site,
- loss in immune function, or
- antibiotic-induced change in normal flora (overgrowth of certain anaerobes).
- Anaerobic bacteria can also travel from their normal site to enter a normally sterile site. (in blood)
Name 6 clinical manifestations of anaerobic infections
• Abscesses (from normal flora-site) • Peritonitis, wound infx (after surgery) • Dental and oral infx (cervico-facial) • Necrotizing PNA • PID Bite Wounds
Why does trauma increase risk of anarobic infx
the loss of blood supply –> anaerobic conditions
Infection by anaerobes commonly follows what 2 events?
Infection following human or animal bites or related to ABX use
actinomyces infx presents with what in discharges?
Presence of sulfur granules in discharges
What is seen on wounds to indicate anaerobic infx (3)
- Foul-smelling wound or dischrage
2. Tissue necrosis or 3. abscess formation near mucosal surface
What would the gram stain and culture of an aerobic infx look like
Organisms seen on Gram stain, but no growth on routine aerobic culture- “sterile pus”
What do the inappropriate specimens for culturing an anaerobe have in common
(all likely to contain normal anaerobic flora or are not anaerobic sites): throat swabs, gingival swabs, sputum, feces, gastric contents, urine, vaginal swabs
What are the Category 1 drugs for anaerobes (3)
Carbapenems- cover aerobes as well
Metronidazole
B-lactams with B-lactamase inhibitors (ampicillin/sulbactam, ticarcillin/clavulenic acid)
What are the 2 Category 2 drugs for anaerobes
Clindamycin, cefoxitin (ceph)
gram stain and shape of Bacteroides, Porphyromonas and Prevotella
gram-negative rods.
Porphyromonas -what species name and where found normally
P. gingivalis - normally oral
Prevotella -what species name and where found normally
P. melaninogenica - oral (and vagina)
What anaerobe is Tan to black pigmentation on blood agar; requires vitamin K, hemin?
P. melaninogenica
P. gingivalis is uniquely found in what infx
abscesses (gingiva)
P. melaninogenica is found in what infx (3)
bite wounds, lung abscesses, genital infections
What is the Most commonly isolated anaerobe from opportunistic infections
B. fragilis
What does P. melaninogenica look like on blood agar? What does it require to grow? (2)
Tan to black pigmentation on blood agar; requires vitamin K, hemin
What is B. fragilis oxygen requirement? Why?
Moderate anaerobes (can tolerate a higher redox potential than some anaerobes bc it contains: SOD- resists oxygen toxicity
What is the major virulence factor for invasive disease from B. fragilis?
Polysaccharide capsule –
Does B. fragilis show bacteremia, toxemia, sepsis or some combo? and why?
bacteremia without sepsis bc the LPS- shows no endotoxin activity-
No texemia - bc there is no histotoxin produced!!!
What populations does Enterotoxin-producing B. fragilis (ETBF) affect and how?
kids: 1-5 yo = diarrhea
Adults: IBD
What is the virulence factor produced by ETBF?
Zinc metalloprotease called fragilysin
4 infx/disease processes caused by B. fragilis
i. Abdominal abscesses, surgical infections such as peritonitis
ii. Pelvic inflammatory disease (PID) – (spread to vagina from intestines)
iii. Bacteremia without sepsis, with spread to lung, brain etc. (abscesses) – 25% mortality
iv. Diarrhea (ETBF)
4 effective drugs for B. fragilis infx
- metronidazole – most commonly recommended
- carbapenems such as imipenem, ertapenum, doripenum, meropenum
- β-lactam/β-lactamase inhibitor
How to prevent B. fragilis infx
Pre-surgery prophylactic ABX treatmen
fusobacterum morphology and gram stain
gram-negative bacilli
long and thin with pointed ends (fusiform morphology)
F. nucleatum and F. necrophorum are normally found where, respectively
F. nucleatum= oral
F. necrophorum= intestinal
F. nucleatum and F. necrophorum cause what diseases, respectively?
F. nucleatum = Acute necrotizing ulcerative gingivitis (ANUG) (trench mouth)
F. necrophorum = liver and abdominal abscesses
What is the gram stain and morphology of poststreptococcus?
the only anaerobic gram-positive cocci seen in human infections
Tx for poststreptococcus
PCN
Actinomyces gram stain, acid fast stain, morphology
Gram-positive filamentous branching bacilli; non acid-fast
Nocardia: gram and acid fast stain
doesn’t gram stain
AFB
Actinomyces oxygen requirements
grow best anaerobically, some are more aerotolerant
Actinomyces normal where (3)
Normal flora- oral cavity, intestinal tract, vagina.
classic finding in actinomyces CP
“sulfur” granules in pus
3 disease processes caused by Actinomyces
Cervicofacial lesions
Abdominal lesions
Salpingitis (IUD-related)
Eikenella corrodens: gram stain and oxygen requirements
G(-)
NOT AN ANEROBE - facultative anaerobe
How is Eikenella corrodens transmitted and where is it normal
human bites- normal in oral
potential serious CP of Eikenella corrodens
subacute endocarditis (HACEK bacteria)
Tx for Eikenella corrodens
PCN-G
What is MC bacteria found in dog/cat bites?
Pasteurella multocida
Pasteurella multocida Gram stain and morphology. Also- special staining chc
gram-negative coccobacilli or rods.
Exhibit bipolar staining
virulence factor for Pasteurella multocida
anti-phagocytic capsule.
Clinical manifestations of Pasteurellosis (2)
Cellulitis = MC
Spread to blood (septicemia, meningitis)-
Tx of Pasteurella multocida (3)
Penicillin G - anaerobe,
ampicillin, cefuroxime- aerobic
