Bacteroides, Prevotella, & Porphyromonas Flashcards
What are the 3 major characteristics of Bacteroides, Prevotella, and Porphyromonas?
- non-spore-forming
- Gram-negative
- anaerobic
What are the most common spore-forming and non-spore-forming anaerobes?
SPORE-FORMING:
- Gram +: Clostridium
NON-SPORE-FORMIN:
- Gram +: Actinomyces
- Gram -: Bacteroides, Prevotella, Porphyromonas, Fusobacterium
Why is oxygen toxic to obligate anaerobic bacteria?
these bacteria lack….
- superoxide dismutase: turns superoxide into less reactive hydrogen peroxide
- catalase: turns hydrogen peroxide into oxygen and water
Where are anaerobic bacteria typically part of the normal flora in animals and humans? What is their function?
mucous membranes - GI tract, oral cavity, urogenital tract
protect against pathogens at mucosal surfaces
What happens at each mucosal membrane when the anaerobic bacteria are able to act as opportunistic pathogens? When are they able to cause disease?
- GI tract: IBD
- oral cavity: periodontal disease
- urogenital tract: pelvic inflammatory disease, UTI
trauma/perforation of the mucous membrane
What is characteristic of anaerobic bacterial disease? How does this affect treatment?
polymicrobial nature —> synergism with facultative anaerobic bacteria
broad spectrum antibiotics required
How do obligate and facultative bacteria work together to cause polymicrobial disease?
OBLIGATE anaerobes provide protection against antimicrobials and phagocytosis by forming abscesses
FACULTATIVE anaerobes scavenge molecular oxygen, which reduces redox potential
What are 4 common virulence factors of anaerobic bacteria?
- capsule*** - antiphagocytic, abscess formation
- LPS
- fimbriae - attachment
- toxins/exoenzymes - tissue damage
What is an abscess? How do they aid in anaerobic bacterial infection?
collection of pus that includes the buildup of fluid, living/dead WBCs, dead tissue, and bacteria
- protection from antibiotics
- protection from phagocytosis
- bacteria are able to break free upon rupture, migrate into blood vessels, and cause systemic infection
What should be sampled in anaerobic infections? What are 2 important aspects to isolated these bacteria?
pus, discharges, tissues —> rapid transport in anaerobic transport media
- enriched media with vitamin K and hemin
- anaerobic cultures in a chamber jar, container, or bag
What are the 2 treatments for anaerobic infections?
- antibiotic therapy - tend to be resistant to β-lactams
- surgical intervention
What is Bacteroides?
non-spore-forming, Gram-negative, pleomorphic, bile-resistant, anaerobic rods that tend to be aerotolerant
What are 2 characteristic substances that Bacteroides produce?
- capsular polysaccharides
- short-chain fatty acids (SCFA) - strong odor characteristic of anaerobic infection
Where is Bacteroides typically found? What species is the most clinically significant pathogen?
normal flora of GI tract, oral cavity, and urogenital tract
(makes up 30% of the total colonic bacteria)
Bacteroides fragilis
How do the capsular polysaccharides and short-chain fatty acids produced by Bacteroides act as virulence factors?
CAPSULAR POLYSACCHARIDES: help with adherence to peritoneal surface, inhibit phagocytosis, and cause abscess formation
SCFA: inhibit phagocytosis and intracellular killing
What 3 enzymes are produced by Bacteroides and act as virulence factors?
- zinc metalloprotease
- protease
- hemolysin
What short-chain fatty acids are produced by Bacteroides? What is used to produce them?
- propionate
- butyrate
- acetate
dietary fiber
What are 3 beneficial effects of Bacteroides production of short-chain fatty acids?
- acts as an energy source
- inhibits the growth of other pathogens (Salmonella) by interrupting pH homeostasis (propionate)
- anti-inflammatory effects (butyrate)
What 2 media are typically used to isolate Bacteroides? What do they usually look like?
- TSA with 5% sheep blood - fastidious!
- Bacteroides bile esculin agar - bile tolerant
+ anaerobic incubation >48 hours
circular, white/gray, 2-3 mm colonies that are shiny and smooth
What antibiotics do Bacteroides tend to be resistant to?
penicillin, kanamycin, vancomycin, colistin
(can grow on media containing these)
How does the site of infection affect diseases caused by Bacteroides?
- NATURAL HABITATS (mucous membranes): intra-abdominal infection, pelvic infections
- BITE WOUND/TRAUMA: skin and soft tissue infections
- HEMATOGENOUS: bacteremia, septic arthritis, meningitis, upper respiratory infection, endocarditis, pericarditis
What characteristic anaerobic lesions can result from Bacteroides infection?
- abscess formation
- inflammatory disease caused by polymicrobial infections
What are common clinical symptoms of bacteremia caused by Bacteroides from a cat bite? What is seen on cytological analysis? Microbiological analysis? How can infection be confirmed?
- inflammation and wound filled with pus
- neutrophilic leukocytosis
- Gram-negative tods resistant to kanamycin, vancomycin, bile, and colistin
- PCR, sequencing
Why is surgical drainage of abscesses necessary for treatment of Bacteroides infection (+ other anaerobic bacteria)?
- there is no blood supply to abscesses so antibiotics cannot be delivered hematogenously
- abscesses tend to have a low pH and antibiotics tend to work at a neutral pH
What is Prevotella?
short, Gram-negative, obligate anaerobic rod (coccobacilli)
Where is Prevotella typically found? What antibiotics do they tend to be resistant to?
flora of oral cavity and gut
- kanamycin
- vancomycin
What are the 2 clinically significant species of Prevotella? What do they cause?
- P. melaninogenica - interdigital necrobacillosis in cattle
- P. heparinolytica - lesions in the buccal cavity in horses and cats
What 3 virulence factors play an important role in Prevotella infection?
- capsule
- protease
- T9SS - specific to Bacteriodetes
What characteristic substance is produced by Prevotella? What are 3 effects it has?
succinate
- inhibit phagocytosis of polymorphonuclear leukocytes
- pro-inflammatory mediator (IBD = increased succinate in lumen)
- improves glucose homeostasis
What are 4 common post-mortem findings in septicemia caused by Prevotella in a cow? 3 findings on histopathological examination?
- hydroperitoneum
- hydropericardium
- petechial hemorrhage
- multiple abscesses in the liver
- hepatocellular necrosis
- neutrophilic infiltrates
- abscess formation
Where can specimens be taken from septicemia caused by Prevotella in a cow? What would be expected to grow?
liver lesions + blood
Gram-negative anaerobic bacteria —> P. melaninogenica
What is Porphyromonas? What fermentation does it undergo?
non-spore-forming, Gram-negative, non-motile obligate anaerobic rods/coccobacilli
ASACCHAROLYTIC, but proteolytic —> flourishes in deep periodontal pockets, which lack sugar
How does Porphyromonas grow on blood agar? Where is it commonly found?
small, black colonies (porphyrin pigment)
members of the oral microbiota in humans and animals —> etiological agent of periodontitis (P. gingivalis in humans and P. gulae in animals)
How does Porphyromonas respond to antibiotics?
- sensitive to vancomycin
- resistant to kanamycin
What unique protease is produced by Porphyromonas? What 4 functions does it have?
gingipains
- nutrient acquisition
- adhesion and tissue invasion
- destruction of host tissue
- dysregulation of host immune responses
How is periodontal disease caused by Porphyromonas infection commonly treated?
clindamycin and interferon-α (suppresses inflammatory response) —> inhibits Porphyromonas gulae
Bacteroides, Prevotella, Porphyromonas, summary:
Are Bacteroides, Prevotella, and Porphyromonas zoonotic?
YES - animal bites
Animal bites are common. 60-80% are caused by _____ and 20-30% by _______.
dogs
cats
(humans bite, too! —> Bacteroides in oral cavity)
Susie was bitten by her neighbor. She developed a fever and bacteremia was suspected. The etiological diagnosis was confirmed by…..
a. aerobic culture
b. anaerobic culture
c. both
C
Meningitis case report from a 78 year old man: CSF examination showed multiple neutrophils with bacteria within them. CSF cultures of CSF has no growth in aerobic conditions and black-pigmented colonies on blood agar in anaerobic conditions. Gram stain showed short Gram-negative rods that didn’t grow on blood agar with vancomycin. What is likely responsible?
Porphyromonas
(Prevotella and Bacteroides would grow well in agar with vancomycin)
