gram negative lecture 2 Flashcards
virulence factors of v. cholerae
- flagella
- pili to adhere to mucosal tissue
- cholera toxin- phage encoded
2 types of E. coli that cause secretory diarrhea
ETEC and EPEC
dysentery-like E. coli
EHEC
type of E. coli that causes urinary tract infections
EPEC
ETEC has a ____ infectious dose and ____ on fimbrae help to adhere to mucosal tissue
large; colonization factor antigens (cfa)
ETEC produces 2 toxins that are responsible for the disease:
heat-labile toxin (LT)
heat-stable toxin (ST)
in vibrio species, cholera toxin causes transfer of ____ from _____ to activate ___
ADP; NAD; Gs
in ETEC, ____ activates AC and ST (heat stabile toxin) activates ____
LT (heat labile toxin); GC
treatment for secretory diarrhea
- oral rehydration- mix of sugar and salt
- antibiotics can help shorten duration or reduce severity
____ used for vibrio infections
tetracyclines
____ for ETEC
2nd generation fluoroquinolones
EPEC is prevalent in ____ and causes _____
newborns; noninflammatory secretory diarrhea
EPEC is located in ____ and requires a ____ infectious dose; absence of traditional ____
distal small intestine; large; exotoxins
EPEC displays a characteristic ____ (aka an attaching and effacing lesion)
adherence pattern
stage 1 of intimate adherence by EPEC and EHEC
bundle-forming pili (bfp) assist in adherence from relative long distance
stage 2 of intimage adherence
syringe-like secretion system (called type III secretion) injects Tir into host cell
for EPEC, there is no ____ production; malabsorption due to ____ and disruptions of _____ cause diarrhea
toxin; microvilli disruptions; epithelial tight junctions
EHEC has set of ____ genes (called eae genes), so it produces an ____; also produces toxin that can lead to _____ (which is much more serious)
EPEC; attaching effacing lesion; hemolytic uremic syndrome
____ is the most common EHEC; ___ are the primary reservoir; causes an _____ (gastroenteritis)
E. coli (O157:H7); cattle; attaching effacing lesion
EHEC produces a ____-like toxin that causes ____ and _____
shiga; hemorrhagic colitis; hemolytic uremic syndrome
diagnosis of EHEC
- frankly bloody stool, edema of ascending colon
- cannot ferment sorbitol, usually
- detection of shiga-like toxins
treatment for EHEC
- no antibiotics, supportive therapy
- rehydrate if necessary
- dialysis if hemolytic uremic syndrome (HUS) pending
natural defenses found in the urinary system
- ureterovesicle valves
- peristalsis
- mucous layer
- normal microbiota
- pH
- complete voidance of bladder
UTI can spread to kidneys and cause _____
pyelonephritis
causes of retrograde flow of urine from bladder to kidneys
- neurological disorders causing poor emptying of the bladder
- hormones during pregnancy cause dilation and decreased peristalsis of the ureters
- incomplete closing of ureterovesical valves in children
causes of pyelonephritis
- retrograde flow of urine from bladder to kidney
- urethral catheters
- urinary tract stones
some bacteria like ____ species can neutralize urine and cause formation of _____ or insolube precipitate that can damage vesicles
Proteus; “struvite” calculi
UPEC can adhere to uroepithelial cells through ____
fimbriae
uncomplicated UTI assoc with fimbrial antigen FimH
acute cystitis
pyelonephritis is assoc with expression of ____
P fimbriae
UPEC assoc with production of ____ and ____ associated with pyelonephritis and has a genetic link to ____
aerobactin; hemolysin; recurrent disease
in addition to ____, ____ is another cause of uncomplicated UTI
UPEC; proteus mirabilis
proteus mirabilis virulence factors
- flagella
- an adhesion on the fimbrae is specific for urinary epithelium
- hemolysins
- IgA protease
- Urease- enzyme that raises pH of urine
effects of urease
- bacteria grow better in less acidic environment
- toxic to renal cells
- enhances formation of struvite (urinary stones) that can lead to a chronic infection
proteus can be identified by:
- consistently alkaline urine
- production of urease
treatment for UTI
- variety of antimicrobials
- trimethoprim-sulfamethoxazole (TMP/SMX) first choice
large, mucoid colonies due to large capsule
Klebsiella
____ important for adherence to urinary tract epithelium
type 1 pili
____ important for adherence to respiratory tract epithelium
type 3 pili
klebsiella enterotoxin similar to ____ so they can induce _____
ST and LT; secretory diarrhea
klebsiella virulence factors
- pili (type 3)
- enterotoxin
- aerobactin- Fe sequestering
- antiphagocytic capsule
among the most prevalent gram negative GI bugs; “slow” bacterium
Helicobacter pylori
H. pylori though to be transmitted through _____
oral to oral contact (as well as fecal to oral)
in the GI tract, H. pylori only found in ____ overlying the _____ of the stomach
mucous; mucous-secreting cells
H. pylori readily killed by ____; efficient producer of ____
gastric acid; urease
h. pylori has _____ molecules- cause epithelial cells to produce ____
inflammatory effector; IL-8
h. pylori cytotoxin is assoc with ____ (induces vacuolation and apoptosis of epithelial cells)
peptic ulcer disease
h. pylori causes downregulation of _____
somatostatin-producing D-cells
treatment for H. pylori includes use of a ____ and ____
proton pump inhibitor; antibiotic cocktail
