gram negative bacilli Flashcards
bacteroides
intraabdominal infection
fusobacterium
pleuropulmonary and CNS infections
tannerella
red complex in periodontal disease
porphyromonas
red complex in periodontal disease
prevotella
orange ocmplex in periodontal disease leading to red complex bacteria
leptotrichia
bacteremia in immunocompromised patients
pseudomonas
1) line, skin, ear, and eye infections, aerobic
cardiobacterium
endocarditis, microaerobic
eikenella
meningitis, endocarditis, facultative anaerobe
bacteroides details
1) Obligate anaerobic bacilli that colonize the oropharynx, GI tract and
genital tract
The most common cause of serious anaerobic infections such as
sepsis, peritonitis and abscesses
Its lipopolysaccharide has no endotoxin activity
No phosphate on lipid A
Fewer fatty acids (5 instead of 6)
An inflammatory neurotoxin
Bacteroides
Bacteroides
fragilis
faintly
staining,
Gram-
negative rods
constitutes a minor member of intestinal flora, but
is the major cause of intraabdominal infections
treatment for bacteroides fragilis
Metronidazole (Flagyl) (Also effective against Giardia infections)
Carbapenems (e.g. imipenem)
Resistance to clindamycin and tetracycline has developed in
B. fragilis (mediated by transferrable plasmids)
Bacteroides melaninogenicus sub-species asaccharolyticus
been re-classified and include
Porphyromonas gingivalis
Porphyromonas endodontalis
Bacteroides fragilis virulence
Adhesins (capsule and fimbriae) mediate adhesion to epithelial cells
and extracellular molecules
The capsule prevents phagocytosis
Collagenase, hyaluronidase, neuraminidase cause tissue destruction
IgG protease inactivates immunoglobulins
Catalase and superoxide dismutase inactivate hydrogen peroxide and
superoxide radical, respectively
Strains of Bacteroides fragilis that cause diarrheal disease
(“enterotoxigenic” strains) produce a zinc metalloprotease
Causes F-actin rearrangement in intestinal epithelium
Where is F-actin? = cytoskeleton of many cells, incl intestinal epithelium,
Results in chloride secretion & fluid loss
metronidazole acts
metabolites integrate and cause DNA breakage
fusobacterium
LPS stimulates leukocyte chemotaxis by activating the alternate
pathway of complement (via C5a)
Fusobacterium species are common in pleuropulmonary and CNS
infections
Wolinella is a fusobacterium that populates the oropharynx
Cardiobacterium
C. hominis is present in the respiratory tract of about 70% of healthy
individuals
Most patients who develop C. hominis endocarditis have a history of
dental disease or dental procedures before clinical symptoms
developed, and pre-existing heart disease
Enters the bloodstream from the oropharynx, adheres to the
damaged heart tissue, and multiplies
Eikenella corrodens
Facultatively anaerobic, Gram-negative bacillus
A normal resident of the upper respiratory tract
Opportunistic pathogen: causes infections in immunocompromised
patients and in patients with diseases or trauma to the oral cavity
Causes sinusitis, meningitis, brain abscesses, pneumonia, lung
abscesses, and endocarditis
Can be treated with penicillin, tetracycline, Cefoxitin and the third-
generation cephalosporins
psudomonas aurigenosa
Aerobic, Gram-negative bacilli
In soil, decaying organic matter,
vegetation and water
In hospitals: food, cut flowers,
sinks, toilets, floor mops,
equipment for respiratory
therapy and dialysis
In hexachlorophene-containing soap solutions and disinfectant
solutions
pseudomonas aurigenosa
Adhesins
Bacterial neuraminidase
Polysaccharide capsule
Endotoxin
Exotoxin A
Blocks protein synthesis
ADP-ribosyltransferase
Tissue damage in burn wounds, chronic pulmonary and
ocular infections
A prevalent pathogen in cystic fibrosis patients
Exoenzymes *S and T ADP-ribosyltransferase
Interferes with phagocytotic killing
Cause epithelial cell damage, via actin rearrangement
Elastases: lung parenchymal damage, hemorrhagic lesions
(ecthyma gangrenosum)
Degrade complement, inhibit PMN chemotaxis
Phospholipase C
prophoryromas antibiotic resistance
Antibiotic resistance
Mutation of porin proteins
b-lactamase production
Pyocyanin
Impairs ciliary function
Stimulates IL-8 release (neutrophil migration)
Mediates tissue damage via production of superoxide
and hydrogen peroxide (in the presence of pyochelin, a
siderophore)
p aurigenosa transmission
biquitous opportunistic pathogen
Persistent carriage common in hospitalized patients
Risk factors
Prior treatment with broad-spectrum antibiotics
Respiratory therapy
Prolonged hospitalization
Compromised immune function
Exposure to contaminated water
Diabetes
Old age
iv drug use
p.. aurigenosa
Pulmonary infections
From benign tracheobronchitis to
severe necrotizing bronchopneumonia
Cystic fibrosis > involvement of pulmonary parenchyma
Primary skin infections
Mostly in burn wounds; localized vascular damage; tissue necrosis;
Bacteremia
Ecthyma gangrenosum in a child with Pseudomonas
septicemia associated with immunodeficiency
Due to degradation of elastin by bacterial elastase
Ear infections
External otitis
Most frequently caused by P. aeruginosa Swimming
is a risk factor
Malignant external otitis (elderly and diabetics) Damage to
nerves and bone
Chronic otitis media
Eye infections
Bacteremia Mostly in patients with neutropenia, diabetes,
extensive burns and hematological malignancies
Mortality rate > 50%
Endocarditis Mostly in iv drug users
p. aurigenosa treatment
Resistant to most antibiotics
Resistance can develop during therapy
ß-lactamases, plasmid-mediated transfer
Combination of aminoglycosides (poor activity in the acidic
environment of an abscess) and ß-lactam antibiotics
ticarcillin + clavulanic acid = timentin
piperacillin + tazobactam = “Zosyn”
Hyperimmune serum
Granulocyte transfusions beta lactamase inhibitors
Porphyromonas
P. gingivalis, P. endodontalis indentification
Asaccharolytic strict anaerobes
requiring vitamin K and hemin
for growth
Produce black-pigmented colonies when grown on blood agar;
the pigment may be involved in protection from the toxic effects
of oxygen
Found almost exclusively at subgingival sites, especially in
advanced periodontal lesions
. gingivalis is highly virulent in experimental infections in animals
Produces proteases (gingipains) that degrade immunoglobulins,
complement and iron- and heme-sequestering proteins
Gingipains are secreted through the
Type 9 Secretion System T9SS
Produces a hemolysin, and collagen degrading enzymes
It has fimbriae that mediate adherence to oral epithelial cells and to
saliva-coated tooth surfaces
Leptotrichia
Leptotrichia can be isolated from the oral cavity and the
genitourinary and intestinal tract and are mainly found in
biofilms. Recognized by van Leeuwenhoek in 1683.
L. buccalis has been isolated from irreversible pulpitis, pulp
necrosis, apical periodontitis and dental plaques of patients with
alveolar bone loss
It is associated with malodor, caused by volatile sulfur compounds
(VSCs), including hydrogen sulfide (H2S), methyl mercaptan
(CH3SH), other thiols, and dimethyl sulfide ((CH3)2S).
On rare occasions, Leptotrichia has been isolated from blood
cultures of patients with lesions in the oral mucosa, especially
from patients with neutropenia.
Leptotrichia
buccalis
prevotella
prevotella
P. intermedia, P. melaninogenica, P. buccae
Moderately saccharolytic strict anaerobe requiring vitamin K
and hemin for growth
Found in dental plaque
P. intermedia is associated with chronic periodontitis and
dentoalveolar abscess
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