Module 9 part 2 Flashcards
main groups of enteric bacteria
enterobacteriaceae, cibrionaceae, bacteriodaceae, and pseudomonadacaea
E. coli, klebsiella, shigella, and Salmonella are which group of enteric bacteria?
enterobacteriaceae
What enteric bacteria cannot ferment lactose?
Salmonella, shigella, and Pseudomonas aeruginosa
Bile salts in this growth medium inhibit gram positive bacteria, and lactose fermenters turn pink-purple
MacConkey agar
This medium inhibits gram positive bacteria, makes lactose fermenters turn deep purple or black, and E. coli looks metallic green
EMB agar (eosin methylene blue)
3 major surface antigens of enterics
O, K, and H antigens
Antigen that is the most external component of the LPS
O antigen
Antigenic capsule that covers the O antigen
K antigen (think Kapsule)
Antigen that makes up the subunits of bacterial flagella, so only motile bacteria have this antigen
H antigen
2 main types of diseases caused by enterics
diarrhea and other infections (UTI, pneumonia, bacteremia, sepsis)
3 types of intestinal enteric invasion that cause diarrhea
no cell invasion (release exotoxins), invasion of intestinal epithelial cells, and invasion of lymph nodes and blood stream
Enterotoxigenic bacteria
E coli and V cholera
Enteroinvasive bacteria
E. coli, Shigella, and salmonella enteritidis
Enteric bacteria that invade lymph nodes and blood stream
Salmonella typhi, Yersinia enterocolitica, and Campylobacter jejuni
Common nosocomial gram neg bacteria
E. coli, Klebsiella pneumoniae, proteus mirabilis
How does E. coli acquire virulence?
conjugation via plasmid exchange, lysogenic conversion via temperate bacteriophages, and direct transposon mediated DNA insertion
Virulence factors of E. coli
mucosal adherence with pili and invading intestinal epithelial cells, exotoxin production by LT, ST, and shiga-like toxin, endotoxin production
What causes traveler’s diarrhea?
E. coli
Virulence factor of enterotoxigenic E. coli
pili bind to intestinal epithelia and release heat labile (LT) exotoxin
Variation of E. coli that secretes shiga-like toxin or verotoxin
Enterohemorrhagic E. coli (EHEC)
How does EHEC cause disease?
inhibits 60S ribosome which inhibits protein synthesis and results in intestinal epithelial cell death
What disease is associated with EHEC E. coli 0157:H7 found in infected meat?
hemolytic uremic syndrome (with anemia, thrombocytopenia, and uremia (renal failure))
Main virulence factor for enteroinvasive E. coli (EIEC)
plasmid, shared by Shigella too
How does E. coli cause UTI’s?
pili help it travel up the urethra to cause cystitis and sometimes pyelonephritis
Second most common cause of neonatal meningitis
E. coli meningitis
most common cause of gram negative sepsis due to the lipid A component of the LPS
E. coli sepsis
Enteric with a capsule but is non-motile (no H antigen)
Klebsiella pneumoniae
2nd most common cause of nosocomial sepsis
Klebsiella pneumoniae
4 species of Shigella
dysenteriae, flexneri, boydii, and sonnei
What enteric has no flagella, does not ferment lactose, or produce H2S?
Shigella
transmission method of Shigella
fecal-oral route
Clinical symptoms of Shigella infection
diarrhea with flecks of bright red blood and pus, and shallow ulcers in colon found on colonoscopy
Structure of Shiga toxin
A subunit and 5 B subunits
Which subunit of Shiga toxin is responsible for the toxicity
A subunit
Enteric with flagella, produces H2s but does not ferment lactose
Salmonella
Virulence factor for Salmonella
Vi antigen around the O antigen that protects it from antibody attack
Polysaccharide capsule around the O antigen on Salmonella
Vi antigen
3 main serotypes of Salmonella
Salmonella typhi, S. cholerae-suis, and S. enteritidis
most common places Salmonella is found
undercooked chicken and eggs
Which type of Salmonella is not zoonotic and only carried by humans?
Salmonella typhi
Disease also called enteric fever
Typhoid fever
Transmission route of Typhoid fever
fecal-oral
What does typhoid invade in the body?
intestinal epithelium first, then lymph nodes then multiple organ systems
What bacteria is also known as a facultative intracellular parasite?
S. typhi
How long does salmonellosis take to develop?
1-3 weeks after exposure
Antibiotics to treat typhoid
cipro and ceftriaxone
Who are prone to salmonella infections?
no spleen or sickle cell anemic
Where do ‘carrier state’ patients harbor S. typhi?
in their gallbladder
What form of salmonella causes sepsis usually?
S. cholerae-suis
How does the immune system clear encapsulated bacteria
opsonizing it w antibodies
What immune cells in the spleen phagocytize Salmonella bacteria?
macrophages and neutrophils
Most common type of salmonella infection caused by everything but typhoid
diarrhea/gastroenteritis
Treatment for Salmonella gasstroenteritis
fluid and electrolyte replacement, NOT antibiotics
Curved gram neg rod with a single polar flagellum
Vibrio cholerae
Transmission route for cholera
fecal-oral route
name of cholera toxin
choleragen
How does cholera cause death
dehydration
Structure of choleragen
2 A subunits and 5 B subunits
Mechanism of action of choleragen
B subunits bind to the receptor. A subunit enters the cell membrane and activates a G protein which stimulates adenylate cyclase. this produces increased cAMP and causes active secretion of ions and water
bacteria usually associated with immunocompromised nosocomial infections
Pseudomonas
obligate aerobic, non-lactose fermenting, gram neg bacteria
Pseudomonas
Bacteria that produces a green and blue pigment (pyoverdin and pyocyanin)
Pseudomonas
Important Pseudomonas aeruginosa infections
“BE PSEUDO” Burns, Endocarditis, Pneumonia, Sepsis, External malignant otitis media, UTI, Diabetic Osteomyelitis
2 pathogenic species of Mycobacterium
mycobacterium tuberculosis and M. leprae
thin rods with lipid-laden cell walls, acid fast, and obligate aerobes
Mycobacterium
mycolic acid bound to a carbohydrate that forms a glycolipid
mycoside
mycoside formed by 2 mycolic acids and trehalose, found in virulent strains of M. tuberculosis
cord factor
What virulence factor of M. tuberculosis inhibits neutrophil migration and damages mitochondria
Cord factor
Mycosides that resemble cord factor with sulfates attached to the disaccharide, that inhibit phagosome fusion with lysosomes
Sulfatides
complicated mycoside that acts as an adjuvant on M tuberculosis that activates the protective cellular immune system
Wax D
Pathogenesis of TB
facultative intracellular growth, cell mediated immunity (not very good): macrophages present bacteria to CD4+ T cells, which become Th1 cells and produce IFN gamma and TNF alpha and activate macrophages. Destruction of lung tissue occurs and the bacteria can still stick around
Clinical manifestations of TB
symptomatic primary TB, asymptomatic primary TB, secondary or reactivation TB (pulmonary TB), pleural and pericardial infection, lymph node infection, sterile pyuria, POTT’s disease, arthritis, meningitis, and miliary TB
RBCs and WBCs found in the urine but not bacteria
sterile pyuria
calcified TB tubercle in the middle or lower lung zone
Ghon focus
Vaccine for TB that may result in a false positive PPD
bacillus calmette-guerin (BCG)
What could cause a false negative PPD
anergy from steroid use, malnutrition, AIDS, etc
Drugs used to treat TB
isoniazid, rifampin, ethambutol, streptomycin, and pyrazinamide
Length of treatment for TB
6 months for normal TB and 18-24 mo for drug resistant TB
Bacteria that causes leprosy or Hansen’s disease
mycobacterium leprae
5 subdivisions of Leprosy
Lepromatous leprosy (LL), tuberculoid leprosy (TL), borderline lepromatous (BL), borderline (BB), and borderline tuberculoid (BT)
most severe form of leprosy
Lepromatous leprosy
symptoms of LL
skin lesions all over the body, destroyed nasal cartilage and saddlenose deformity, blindness, thickening of peripheral nerves and neuropathy
Form of leprosy where patients cannot mount a cell mediated immune response
lepromatous leprosy (LL)
form of leprosy where patients CAN mount a cell mediated response
Tuberculoid leprosy
Form of leprosy where there are only a few well defined lesions on the skin
TL
Treatment for mycobacterium leprae
sulfones (like dapsone), rifampin, and clofazamine
Common opportunistic infection in AIDS patients
Mycobacterium avium-complex (MAC) disease, caused by non tuberculous mycobacteria (NTM)
