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Microbiology: Gram Negative Bacteria
Terms in this set (109)
what are enteric bacteria?
cause infections in intestine
what are some members of the family enterbacteriaceae?
Yersinia pestis .
what are some members of enterobacteriaceae that do not cause enteric infections?
what is the shape of enterobacteriaceae?
what enzyme do enterobacteriaceae not have?
Cytochrome oxidase negative
important features of enterobacteriaceae?
Gram negative rods (Largest group of clinically relevant Gram negative bacilli)
Ferment glucose (use of other sugars are used to distinguish members within the Family)
Cytochrome oxidase negative (useful to distinguish enterics from others)
Peritrichous Flagella (if motile)
what are the virulence factors of enterobacteriaceae?
Sequestration of Growth Factors (e.g. iron).
Antigenic phase Variation.
Type III secretion systems.
what is the antigen name of capsule?
or Vi (special for klebsella)
what is the antigen name of flagella?
what are the two important media for enteric bacteria?
Hektoen enteric agar:
what is MacConkey agar?
Contains bile salts and crystal violet to inhibit other bacteria; contains lactose and pH indicator to differentiate lactose fermenters.
What is Haktoen enteric agar?
Hektoen enteric agar:
Contains bile salts to inhibit other bacterial
Contains iron to detect H2S producing bacteria such as Salmonella and distinguish from other bacteria such as Shigella and E. coli.
What is the reservoir of Ecoli?
Human colon, vagina, and urethra.
Can contaminate crops.
Enterohemorrhagic strains in animal feces.
what are the different strains of Ecoli?
ETEC, EPEC,EIEC, EHEC, EAEC
what are important virulence factors of ecoli strains?
what are the types of adhesins for E. Coli?
P-pili: pyelonephritis-associated pili are important for binding uroepithelium
Colonization Factor Antigens CFA/I, II, and III
Aggregative Adherence Fimbriae AAF/I and III
what are the exotoxins produced bu different strains of E coli?
Heat-stable Toxins (stimulate guanylate cyclase)
Heat-labile Toxins (stimulate adenylate cyclase)
Shiga-like Toxins (inhibit protein synthesis)
what are some diseases that E. Coli can cause?
Urinary Tract Infections
Enterotoxigenic E. coli (ETEC)
what does it cause and what toxins does it have?
LT and ST producing strains
Enteropathogenic E. coli (EPEC)
what does it cause, what type of damage odes it cause and what virulence factor does it have?
Second most common cause of infant diarrhea
Plasmid encoded EAF (E. coli Adherence Factor)
Cause effacement of brush border microvilli
Enteroaggregative E. coli
what does it cause? and what virulence factor does it have?
Plasmid-encoded AAF proteins mediate attachment in a "stacked brick" arrangement
Enterohemorrhagic E. coli (EHEC)
what does it cause? what type of virulence factor?
Verotoxin-producing strains (aka VTEC); Shigalike toxins (Stx-1 and Stx-2)
From mild diarrhea to hemorrhagic colitis
May cause hemolytic uremic syndrome (HUS), associated with Stx-2
what what is the most common strain of EHEC in US?
Enterotoinvasive E. coli (EIEC)
Similar to shigellosis; about 10% progress to dysentery
Plasmid-encoded invasion genes
which E. Coli strains act in small intestines and which in large?
Small: ETEC, EPEC, EaEC
Large: EHEC, EIEC
what diseases can salmonella cause?
Enteric fever (Typhoid fever).
how are the species written for salmonella?
Salmonella and then the subspecies
what is the important species of salmonella?
what is the reservoir for salmonella?
All from eggs or animals as well as humans except Salmonella Typhi and Salmonella Paratyphi, which have only human hosts.
how do you grow salmonella?
Selective medium required for isolation.
what are the virulence factors for Salmonella?
O antigens used to serogroup
Capsular (K) antigen is antiphagocytic. Virulence (Vi) antigen of Salmonella Typhi (also a capsular antigen).
Identified further by the presence of different flagellar (H) antigens.
Endotoxin causes fever, leukopenia, hemorrhage, hypotension, shock, and disseminated intravascular coagulation.
Some may produce an exotoxin (enterotoxin).
They can survive within macrophages by an unknown means.
whta do salmonella produce that can be detected to help distinguish them?
what is the first thing salmonella cause and what species cause it?
Symptoms appear 6-48 hours after consumption.
Caused by a variety of serovars (S. Enteritidis, S. Thphimurium....)
what is enteric fever? symptoms?
Gradual onset of a fever that increases during the day, reaching a plateau of 102-105°F (38.8-40.6°C) each day.
Blood cultures are positive in symptomatic phase.
"Rose spots" may appear on the trunk.
Complications are GI hemorrhage and bowel perforation with peritonitis.
what is the pathogenesis of enteric fever?
Initial colonization is in M-cells of small intestine (ileocecal region).
Disseminate into bloodstream then to multiple organs.
Multiplies in the reticuloendothelial system and lymphoid tissue of the bowel, producing hyperplasia and necrosis of the lymphoid Peyer's patches.
what is the reservoir of typhoid fever causing organisms?
what is the virulence factor for typhoid fever?
how do carriers happen?
Carriers harbor bacteria in gall bladder.
Low acid stomach predisposes host.
how is typhoid spread?
what are common vectors of typhoid fever?
Poultry, eggs, anddairy foods are mostcommon vectors.
what type of organism is salmonella?
what individuals usually get septicemia from salmonella?
what is a means of causing septicemia?
contaminated intravenous fluids, abdominal or pelvic
what does shigella cause?
what is dysentary?
Formerly known as flux or the bloody flux.
An inflammatory disorder of the intestine, especially of the colon.
Results in severe diarrhea containing mucus and/or blood in the feces with fever and abdominal pain.
If left untreated, dysentery canbe fatal.
whta can cause dysentry?
Can be caused by Entamoeba histolytica (amoebicdysentery)
or bacteria (bacilli).
Bacillary can be Shigella, Salmonella, invasive E. coli
what is the only known resivoir of shigella?
how is shigella spread?
most common in shigella?
Most common in U.S.
which shigella causes the most sever disease?
Most severe disease
which shigella is most common in underdevleped countries?
Most common in underdeveloped countries
how many bacteria does it take to establish shigellosis?
w bacteria can establishan infection (100-200)
what is shigellosis
Initial water diarrhea progressing within 1-2 days to abdominal cramps and tenesmus.
With or without bloody stools.
what bacteria largely causes shigellosis and how?
S. dysinteriae disrupts protein synthesis and produces endothelial damage
how does organism spread
CUT THIS DOWN
Shigella spp. cross M (microfold) cells of the follicle-associated epithelium that covers the lymphoid nodules associated with the colonic mucosal tissues. In this subepithelial location, Shigella spp. cause extensive apoptosis of macrophages. This process allows escape of bacteria into the tissues and efficient basolateral entry to epithelial cells, followed by cell-to-cell spreading, which generates efficient intracellular colonization. Caspase-1-mediated apoptosis can also initiate inflammation through the release of mature interleukin-1 (IL-1). The inflammatory mechanism is considerably amplified by the presence of intracellular bacteria that activate the NOD1 (nucleotide-binding oligomerization domain protein 1) pathway through the release of peptidoglycan (PGN). CXCL8, CXC-chemokine ligand 8; NF-B, nuclear factor-B.
What causes Shigella virulence?
Actin- Based Motility
what is shiga toxin produced by and what does it do?
Produced by S. dysenteriae type 1.
Inhibits protein synthesis.
Affects intestinal epithelium and glomerular endothelium (HUS).
what does IpaA-D protein do?
Secreted into M cells and macrophages.
Mediate membrane "ruffling".
Induces host cells to engulf bacterium.
what does the actin based motility for shigella do?
enables cell-to-cell spread.
what are the four most common enteric bacteria causing diseases in the states
what is the resivoir for yersenia and what type of infections do they usually cause?
Zoonotic infections (animal reservoirs)
what are the virulence factors of yersinia?
Antiphagocytic protein capsule (Y. pestis)
Plasmid-encoded virulence genes.
what 2 diseases does yersinia pestis cause?
what is yersinia spread by
Spread by fleas or direct contact.
what symptoms does bubonic plague cause?
Fever, painful buboes, andconjunctivitis.
how is pulmonary plague spread?
how does pulmonary plague kill?
rapid necrotic pneumonia.
Highly contagious and fatal
what are other names for bubonic plague?
Urban plague.-in urban areas
Sylvatic plague.- in nature
how is rural plague spread?
happens between rats and fleas
how is urban plague spread?
spread from rural rats and fleas to rural rats and fleas and causes bubonic form
how can bubonic plague spread from human to human?
how does resipiratory plague spread from person to person?
what type of environment can yersinia pestis grow in?
Facultative intracellular pathogen
how is yersinia pestis stained?
Bipolar staining with Giemsa stain.
how exactly is yersinia replicated in fleas and spread?
Coagulase coagulates in the blood of flea GI tract makes fibrin clot where bacteria replicate. Flea tries to feed again, high numbers of bacteria regurgitated into the host's bloodstream.
what is virulance factor in yersinia pesitS?
Capsular polysaccharide. Survives in phagocytes (PMN cells and macrophages).
what is LPS role in yersinia pestis?
LPS interferes with platelet function. Vascular collapse and disseminated intravascular coagulopathy Thrombi in pulmonary vessels leads to pneumonic plague.
what is vibrio? and what type of infections does it cause?
gram negative that causes gastrointestinal disease or wound infections.
how is vibrio spread?
water and sea food
what ar three important species of vibrio and what do they cause?
V. cholerae (gastroenteritis, cholera)
V. parahaemolyticus (seafood poisoning and wounds)
V. vulnificus (wound infections and seafood poisoning )
shape of vibrio?
how does vibrio move?
with POLAR flagella
how can vibrio be distinguest from enterobacteriacea when testing?
it is oxidase positive
what are the serotypes of vibrio cholerae?
Serotyped by O antigens (LPS)
O1 and O139 strains produce cholera toxin
what is the main virulence factor of cholerae and how does it work?
Cholera toxin (an A/B type toxin) causes tremendous water loss from intestinal cells.
how does cholera toxin cause water loss?
read slide 38 that says vibriocholerae
what are symptoms of cholera?
Rice water diarrhea.
Loss of fluid (15-20 liters/day).
how can cholera replicate and spread?
Is endemic in marine environments.
Can replicate in water.
Associated with poor sanitation and hygiene.
can it be spread from person to person?
what can be a reservoir in endemic areas?
Asymptomatic carriers may be reservoir in endemic areas.
how many organisms does it take to infect a person?
A large number of organisms is required for infection due to the sensitivity to gastric acidity.
how do you treat cholera?
Fluid and electrolyte replacement. Patient appear healthier within 1 to 3 hours. Reduces fatality from 60% to 1%.
If antibiotics are not given, the patient will recover but will shed organisms for as long as 1 year.
what are three oppertunistic bacteria?
what are the important species of klebsiella?
Klebsiella pneumoniae Klebsiella oxytoca
what is the virulence factor of kleb?
Large mucoid polysaccharide capsule.
what are some characteristics of kleb?
Lactose positive, non-motile.
Common to human colon and urinary tract
what diseases does kleb cause?
Pneumonia (blood tinged sputum "currant jelly", Associated with alcoholism)
Wound and soft tissue infections.
Urinary tract infections.
if you see a stained slide and there are white rings around the bacteria what does that indiciate?
"halo" is common because capsule didnt stain
what kind of infections can it cause?
what are distinguishing characteristics of proteus mirabilis?
Strong urease reaction.
Highly motile "swarming motility".
Environmental or human origin.
what can proteus mirabilis cause?
Urinary tract infections
Transmitted by catheters.
Urease activity raises pH, can precipitate kidney stones
what does pseudomonas aeruginosa cause?
Most infections are opportunistic, affecting compromised tissues
Pulmonary Infections (particular problem for cystic fibrosis patients).
Open wound and soft tissue infections
Cellulitis with blue-green pus.
Urinary Tract Infections.
Ear and Eye infections.
where is pseduomonas found?
Ubiquitous (commonly found in water and soil).
how common is pseudomonas in hospital infections?
10% of nosocomial infections
what is pseudomonas notorious for?
Notorious antibiotic resistance.
if you have infection with blue-green pus what should you think?
what are distinguishing factors and growth factors of pseudomonas?
Strict aerobe. - Simple growth requirements. - Hemolytic.
Distinct color and odor when grown the solid medium.
what are the virulence factors of psedomonas
Pilli for adherence.
Pyocyanin. (blue green)
fluorescein (yellow) and pyorubin (red-brown).
Mainly through outer membrane porins.
what is pyocyanin
Blue-green pigment that is also a toxin.
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