Enteric Bacteria Flashcards
What are the human pathogens of Enterobacteriaceae?
Escerichia coli Salmonella sp. Shigella sp. Yersinia sp. Klebsiella sp.
What are the main characteristics of Enterobacteriaceae?
Gram (-)
Facultative anaerobes
Non-endospore forming
What are the main characteristics of Coliform bacteria? What are some examples?
Enterobacteriaceae family
Ferment lactose (MacConkey’s agar)
Escerichia coli, enterobacter sp., Klebsiella sp.
What are bacteriocidins?
Toxins produced by Enterobacteriaceae that stop the growth of competitive bacteria
What are enterotoxins and which ones are produced by Enterobacteriaceae?
They are toxins that affect the GI tract Heat-labile enterotoxin Heat-stable enterotoxin Verotoxin Endotoxin
What does heat-labile enterotoxin do?
Constitutively activates cAMP, leads to fluid and electrolyte secretion into the gut lumen = diarrhea
What does heat-stable enterotoxin do?
STs (STa and STb)
Constitutively activates cGMP, leading to fluid and electrolyte secretion
What does Verotoxin do?
aka Shiga-like toxin
Cytotoxin acting on the vascular endothelium
Leads to vascular leakage = bloody stool
What is endotoxin?
LPS aka pyrogen
Produced by most gram (-) bacteria
What are the clinical features of LPS (enterotoxin) toxicity?
Fever Leukopenia Hypotension Anaphylaxis Vascular leakage Septic shock Systemic inflammatory response syndrome (SIRS)
What is the O antigen of enterobacters?
It is a somatic antigen
Polysaccharide component of G (-) bacteria
170 serotypes in E. coli
What is the H antigen of enterobacters?
Flagella antigen
Made of protein
56 serotypes in E. coli
What is the K antigen of enterobacters?
Capsular antigen
Can be polysaccharide or protein
80 serotypes in E. coli
What diseases are caused by Enterobacteriaceae?
UTIs
Gastroenteritis
What are the anatomical and mechanical features associated with UTIs?
Length of urethra
Disruption of urine flow and bladder voiding (congenital, surgery, catheter, disease)
Physiological (pH changes, pregnancy, immunocompromised)
Sexual intercourse
What are the risk factors for a UTI in men?
Circumcision
Enlarged prostate
What are the bacterial sources of UTIs?
E. coli (80% cases)
Coagulase-negative Staphylococci = S. saprophyticus (10%)
S. aureus, Enterococcus faecalis, Pseudomonas aeruginosa, Klebsiella sp., Enterobacter sp.
C. albicans
What are the viral causes of UTIs?
Viral causes are rare
CMV, adenovirus, mumps, rubella
Associated with hemorrhagic cystitis
What are the symptoms of gastroenteritis?
Inflammation of the GI tract
Diarrhea - involvement of small intestine
Dysentery - blood or pus in feces, pain, fever, cramps, involvement of large intestine
What infectious agents cause gastroenteritis?
Viral - rotavirus, norovirus
Bacterial - enterobacters, C. difficile
Protozoan - Giardia lamblia
What are the characteristics of Escherichia coli?
G(-) rod-shaped facultative anaerobes
Lactose fermenting, coliform bacteria
Indicator organism for fecal contamination of water
What are the symptoms of a uropathogenic E. coli (UPEC) infection?
Common cause of UTIs
Inflammation of urinary tract, difficulty or pain during urination, cloudy urine indicates bacteriuria
What are the symptoms associated with an ascending UTI infection?
More severe
Urethritis, cystitis (bladder), pyelonephritis (kidneys), prostatitis (prostate)
What are the virulence factors associated with the pathogenesis of E. coli UTI?
Adhesins (P fimbriae, Dr adhesins, etc)
K antigen contributes to biofilm formation
What are the clinical features of UTIs?
Urethritis Cystitis Pyelonephritis Prostatitis Epididymitis
What are the symptoms of epididymitis?
Low grade fever/chills, testicular inflammation and pain, may lead to infertility
What are the symptoms of Prostatitis?
Fever, chills, urinary dysfunction (painful, difficulty initiating or voiding, bloody urine)
What are the characteristics of enteropathogenic E. coli (EPEC)?
No ST, LT toxins, no fimbriae, some serotypes posses Shigatoxin
Intimin - adhesin for intestinal epithelial cells
What are the characteristics of enteropathogenic E. coli infection?
Moderately invasive to gut epithelial cells
Mild diarrhea, some inflammation, afebrile, typically seen in infants
What are the characteristics of enterotoxigenic E. coli? (ETEC)
ST, LT, fimbriae expressed, non-invasive
What are the characteristics of an enterotoxigenic E. coli (ETEC) infection?
Profuse watery diarrhea, afebrile, no inflammation
Associated with children’s and traveller’s diarrhea
What are the characteristics of enteroinvasive E. coli? (EIEC)
No ST, LT, fimbriae or Shiga-like toxin expressed
What are the characteristics of enteroinvasive E. coli infection? (EIEC)
Invasive, clinical symtpoms similar to Shigellosis
Fever, profuse diarrhea, severe inflammation, bloody stool, dysentery-like diarrhea
What are the characteristics of enteroaggregative E. coli (EAEC)
ST-like toxin and hemolysins expressed, non-invasive
What are the characteristics of anteroaggregative E. coli infection? (EAEC)
Afebrile, no inflammation, persistent diarrhea, typically seen in young children
What are the characteristics of enterohemorrhagic E. coli (EHEC)?
Fimbriae or fimbria like adhesins, moderately invasive
What are the characteristics of an enterohemorrhagiv E. coli infection (EHEC)
Profuse, bloody diarrhea, low to no fever but severe inflammatory response (hemorrhagic colitis)
H7:O157 a member of this family
Haemolytic-uremic syndrome complication (anemia and kidney failure)
How is Escherichia coli transmitted?
GI - fecal:orally
UTIs - introduction of pathogen to urinary tract (sexual activity, hygiene, catheter, pre disposition)
What are the characteristics of salmonella sp?
G(-) rod shaped facultative anaerobes
Non lactose fermenting
hydrogen sulfide positive
What are the characteristics of gastroenteric infection with Salmonella sp.? Which species cause it?
S. enterica, S. typhimurium Emetic and diarrheal, febrile Associated with headache and muscle weakness Lasts several days to one week Some invasive - sepsis
What are the characteristics of typhoid? What causes it?
S. typhi
Headache, rash, abdominal pain
Diarrhea more common in children, constipation in adults
Penetration of intestinal mucosa leads to bacteremia
Endotoxin release in the bloodstream leads to cardiovascular collapse
May remain asymptomatic carriers for months
What are the characteristics of Shigella sp.?
H2S negative
Facultatively intracellular
What are the characteristics of a gastroenteric Shigella infection? What species cause it?
S. dysenteriae, S. flexneri, S. boydii Fever, vomiting, profuse bloody and/or mucoid diarrhea, abdominal cramping Dysentery, haemolytic-uremic syndrome Infection dose very low days to one week
What is reactive arthritis or Reiter’s syndrome? Risk factors?
An autoimmune, post-infectious sequelae typically following a bacterial infection
Risk factors: HLA-B27
What are the symptoms of reactive arthritis or Reiter’s syndrome?
Can’t see, can’t pee, can’t climb a tree (conjunctivitis, urethritis, arthritis) may involve dermatological lesions of the hands/feet
Additive or migratory involvement in the MSK system
Typically knee or SI joints
May involve mutocutaneous lesions
What are the characteristics of Yersinia sp.?
G(-) rod shaped facultative anaerobes
Non lactose fermenting
What are the characteristics of a gastroenteric Yersinia infection? Which species cause this?
Y. enterocolitica, Y. pseudotuberculosis (rare)
Low grade fever, vomiting, watery or mucoid diarrhea
may have erythema nodosum (painful red lesions on trunk or legs)
Long duration of symptoms (1-3 w)
What are the clinical features of Yersina pestis?
Bubonic plague: sudden fever, chills, weakness, headache, swollen lymph nodes
Pneumonic plague: fever, chills, chest pain, cough, respiratory distress, bloody or watery mucous
Septicemic plague: fever, chills, extreme weakness, bleeding into the skin and other organs, vasculitis
First two can lead to septicemic
How is Yersinia pestis transmitted?
Bubonic plague is vector borne (fleas)
Pneumonic plague transmitted by respiratory droplets
What are the characteristics of Klebsiella sp?
Oxidase-negative, encapsulated
Commensal (skin, GI) opportunistic, nosocomial
What are the symptoms of Klebsiella pneumonia?
Inflammation of the bronchi/bronchioles, lung consolidation
Sudden onset of fever, chills, cough with bloody or mucoid sputum
Transmitted by contact, drug resistance common
What nosocomial infections are caused by Klebsiella sp?
Pneumonia
UTI
Wound infection
Catheter and device related infection
What are the characteristics of Vibrio sp?
Comma shaped Gram (-) Oxidase (+) Facultative anaerobes Most species bioluminescent (aquatic species)
What are the human pathogens of Vibrio sp.
Vibrio cholera - cholera
Vibrio parahaemolyticus - gastroenteritis
Vibrio vulnificus - gastroenteritis
What are the characteristics of Vibrio cholera? What kind of toxin does it produce and what are its effects?
Asiatic cholera or epidemic cholera
Produces cholera toxin (enterotoxin): activated adenylate cyclase in intestinal epithelial cells, leading to ion and water diffusion into intestinal lumen
What is the clinical presentation of vibrio cholera?
Profuse, painless diarrhea of clear fluid and severe electrolyte loss
Mucus, epithelial cell shedding leads to rice water stool
Highly fatal
Potassium ion loss leads to cardiac complications
How is vibrio cholera transmitted?
Fecal:oral
What is the infectious dose of Vibrio cholera?
100 million bacteria
Lowered in less acidic gastric environments
Young children more susceptible
What are the symptoms of V. parahaemolytica?
Severe diarrhea if ingested, self-resolving
Skin infection if open wound exposed to contaminated water
treatment supportive
What are the symptoms of V. vulnificus?
Diarrhea, skin infection/dermatitis (blistering skin lesions)
Commonly associated with sepsis
Treatment supportive, broad spectrum antibiotic for severe cases
Where are V. parahaemolytica and V. vulnificus found?
Brackish saltwater (estuaries)
Commonly associated with ingestion of contaminated sea food
Prper seafood cooking (oysters)
What is a unique quality of vibrio parahaemolytica and vibrio vulnificus?
They require salt for growth - halophiles
