Gram-Negative Bacilli (Enteric) Flashcards
Enterobacterales characteristics (metabolism)
Facultative anaerobic bacilli and coccobacilli, many are opportunistic pathogens
Escherichia coli (what diseases it causes)
UTIs, diarrhea, hospital-acquired pneumonia
E. coli determinants of pathogenicity
Alpha-hemolysin, aerobactin, polysaccharide capsule (AAP)
Pore-forming toxin, iron siderophore, reduces phagocytosis
E. coli K1 capsule (what it is associated with)
Meningitis and bacteremia in neonates
UPEC (what is causes)
Uropathogenic E. coli: UTIs
UPEC (types of pili)
Type I pili: Binding in the bladder
P pili: Binding in the upper urinary tract, cause pyelonephritis
ETEC (how is it spread)
Enterotoxigenic E. coli: Spread through contaminated food and water
ETEC (2 toxins)
Heat labile toxin (stimulates adenylate cyclase in gut epithelial cells)
Heat stable toxin (stimulates guanylate cyclase in gut epithelial cells)
EPEC (what it causes)
Enteropathogenic E. coli: Diarrhea in developing countries
EPEC (mechanism)
Bundle-forming pili - attach to intestinal epithelium
Intimin - adhesin
Type III secretion system
Type III Secretion Systems
Directly inject bacterial proteins into cytoplasm of host cells
EPEC Type III Secretion (what does it do)
Loss of normal microvilli structure, pedestal formation, injects Tir (acts as receptor for intimin -> allows for tight adherence)
EHEC (what does it cause)
Enterohemorrhagic E. coli: Bloody diarrhea, abdominal pain, usually no or low-grade fever
EHEC toxin (and what it is responsible for)
Shiga-like toxin, responsible for HUS (hemolytic-uremic syndrome)
E. coli diagnostic laboratory tests
Growth on routine media, biochemical tests (lactose fermentation: MacConkey Agar)
ETEC treatment
Rehydration
EHEC treatment
No antibiotics
Uropathogenic E. coli treatment
Nitrofurantoin, fosfomycin, trimethoprim-sulfamethoxazole
Shigella species (what do they cause)
Dysentery (cramps, tenesmus, frequent small-volume, bloody, mucoid stools)
Salmonella enterica
Facultative intracellular pathogens, common cause of diarrhea
S. enterica serovar Typhimurium (what does it cause)
Typhoid fever
Tenesmus
Feeling that you need to pass stools
Types of enterobacterales
Escherichia coli, Shigella, Salmonella enterica, Yersinia, Klebsiella pneumoniae, Proteus
Gastroenteritis
Stomach virus
Hemolytic-uremic syndrome
Condition that affects the blood and blood vessels, results in the destruction of blood platelets, a low red blood cell count (anemia), and kidney failure
2 Yersinia species (what do they cause)
Y. enterocolitica (infectious diarrhea), Y. pestis (plague)
Myalgias
Muscle aches and pains
Beta-lactam antibiotics (4 classes)
Penicillins, cephalosporins, monobactams, carbapenems
Which beta-lactam antibiotic is active against most gram-negatives?
Carbapenems
ESBL
Extended spectrum beta-lactamases (Cleave cephalosporins and monobactams)
Dysuria
Painful or difficult urination
Y. pestis DP
Bubo formation, LPS in bloodstream, Bacteria make their way to macrophages in the lungs
Type III secretion (paralyze macrophages and neutrophils to prevent phagocytosis), antiphagocytic capsule (F1), Pla cleaves fibrin clots -> facilitates bacterial dissemination
Y. pestis CD
Bubonic plague, Pneumonic plague
Y. pestis DLT (appearance)
Closed safety pins appearance
K. pneumoniae DP
Polysaccharide capsule, siderophores
Proteus species characteristic
“Swarming motility” - hundreds of flagella per cell
Proteus spp (what do they cause and how)
UTIs, nosocomial infections, urease splits urea into ammonium hydroxide, raises urine pH, promotes formation of “struvite” kidney stones
Pseudomonads (metabolism, ferment, where found)
Aerobic Gram-negative rods, cannot ferment glucose (unlike enterobacterales), moist environments
P. aeruginosa DP
Pili, exotoxin A, alginate (exopolysaccharide, antiphagocytic), Type III secretion system, quorum-sensing
PEATQ
P. aeruginosa CD
Opportunistic pathogen, lungs of cystic fibrosis patients, nosocomial infections (pneumonia, UTIs, wound infections), bacteremia and sepsis in neutropenic cancer patients (ecthyma gangrenosum), hot tub folliculitis
P. aeruginosa DLT
Produces grape-like odor, fluorescent pigments, oxidase positive
Acinetobacter baumannii (what do they cause)
Hospital-acquired infections, 50% isolates resistant to carbapenems
Vibrios 2 species and what do they cause
V. cholerae (cause cholera), V. vulnificus (cause gastroenteritis, wound infections following cuts exposed to seawater)
Helicobacter pylori (shape)
Gram-negative, slender, spiral-shaped
H. pylori (common cause of which disease)
Peptic ulcer disease
H. pylori DP
Urease, VacA, Type IV secretion
H. pylori DLT
Endoscopy, Serological tests for IgG, antibody tests to detect in stool, urea breath test
H. pylori treatment
Proton-pump inhibitor + clarithromycin + amoxicillin/metronidazole
Campylobacter (what does it cause)
Gastroenteritis leading to diarrhea
Typhoid fever symptoms
Prolonged fever, persistent bacteremia, occasionally a rash consisting of a few pink macules observed
Salmonella enterica treatment
Treat typhoid fever and bacteremia: Fluoroquinolones, azithromycin
Typhoid fever prevention
Vaccine
