Gram Negative Rods in the GI Tract

what is the oxygen preference of salmonella?

facultative anaerobe

is salmonella motile?

yes, has flagella

what are the 2 types of salmonella?

typhoidal and non-typohoidal

typhoidal salmonella

causes typhoid/enteric fever

s. typhi, s. paratyphi A, B, or C

non-typhoidal salmonella

causes gastroenteritis and in rare cases osteomyelitis

s. typhimurium

how can humans acquire salmonella?

fecal-oral route- ingesting food or water contaminated by human and/or animal feces (s. typhi is only transmitted by humans), humans may excrete salmonella before or after an episode of gastroenteritis

can you get a chronic infection of salmonella?

yes, chronic infection of gallbladder and bacteria can be excreted in feces for years

what are the 3 types of damage that salmonella can cause?

gastroenteritis, typhoid/enteric fever, non-typhoidal salmonella bacteremia

gastroenteritis

12-48 hr incubation period, begins with nausea/vomiting and progresses to abdominal pain/diarrhea (mild or severe, with or without blood), most common form of salmonella disease in the US, most cases caused by s. typhimurium and s. enteritidis, usually self-limiting within a few days

typhoid/enteric fever

caused by s. typhi and several other species, slow onset with fever and constipation, bacteremia, anemia, tender abdomen, enlarged spleen, leukopenia, maculopapular rash (at end of 1st week), resolution by 3rd week of infection

non-typhoidal salmonella bacteremia

usually in very old, very young, immunocompromised, or cancer patients, begins with fever, little or no gastroenteritis, then organ specific, most commonly bones

what virulence factors does salmonella have?

capsular Vi antigen, entero and exo toxins, type II secretion systems, somatic O antigen, flagella (H antigen), fimbriae (adhesion protein) and pili, biofilm, siderophore

how can you treat salmonella infection?

usually supportive treatment is sufficient for gastroenteritis, fluids and electrolytes prevent dehydration

are antibiotics common for salmonella?

no, only recommended for neonates and others at risk for disseminated disease, antibiotic resistance is prevalent

how can you prevent salmonella?

mainly handwashing to prevent fecal-oral route of transmission, 2 vaccines for typhoid/enteric fever (recommended for travelers to countries where it is prevalent)

what is the oxygen preference of shigella?

facultative anaerobe

is shigella motile?

no

where is shigella found?

only in humans, no animal reservoirs, outbreaks occur in day-care centers and institutions where fecal-oral transmission is hard to control

how is shigella transmitted?

fecal-oral route, has a very low ID50, ~100 organisms are sufficient to cause disease, foodborne outbreaks are most common

what damage can shigella cause?

enterocolitis/shigellosis/bacillary dysentery

dysentery

bloody diarrhea

what does the severity of shigella infections depend on?

species and age of patient

young children and elderly usually have more severe disease

s. dysenteriae causes most severe disease (usually occurs in developing countries)

s. sonnei causes a milder disease (common in US)

what virulence factors does shigella have?

shiga toxin, damages intestinal epithelium, encoded by lysogenic phage

shiga toxin

A/B exotoxin, produced by s. dysenteriae, s. sonnei does not produce

what is the treatment for shigella infection?

supportive treatment is usually sufficient- fluids and electrolytes to prevent dehydration, antibiotics may be given for severe cases but resistance is a problem, prevention depends on interrupting fecal-oral route of transmission

is there a vaccine for shigella?

no

Infection with the organism that causes shigellosis most commonly

occurs through:

A. sexual contact.

B. the fecal-oral route.

C. respiratory droplets.

D. cuts in the skin.

E. biting insects.

B. the fecal-oral route

what is the shape of vibrio cholerae?

curved, comma shaped

what is the oxygen preference of vibrio cholerae?

facultative anaerobe

is vibrio cholerae motile?

yes, has flagella

how is vibrio cholerae transmitted?

transmitted by oral-fecal route, ingestion or water or food contaminated with (usually) human feces, humans in incubation or convalescence periods often excrete organisms asymptomatically, outbreaks occur under conditions of overcrowding, poor sanitation, malnutrition

what damage does vibrio cholerae cause?

large volumes of watery diarrhea, rice water stool, loss of up to 15 l of water a day, no blood or white blood cells in stool, no abdominal pain, symptoms due to severe dehydration (loss of fluid and electrolytes can lead to heart and kidney failure, 40% mortality in untreated cases)

what virulence factors does vibrio cholerae have?

mucinase, enterotoxin, genes for cholera toxin and other virulence factors are carried on a lysogenic phage

mucinase in vibrio cholerae

helps them adhere to the cells in the brush border of the small intestine

enterotoxin in vibrio cholerae

mediates the persistent stimulation of adenylate cyclase, resulting in loss of fluid and electrolytes from cells

how do you treat vibrio cholerae infection?

prompt and adequate fluid and electrolyte replacement is critical, antibiotic treatment is usually not necessary

how can you prevent vibrio cholerae?

travelers at risk are advised to take precautions and carry packets of oral rehydration salts if they will not have access to medial care

is there a vaccine for vibrio cholerae?

not used in the US, but there are 2 licensed for use in many countries

what shape is campylobacter jejuni?

curved, comma shaped, or S shaped

what does the gram negative cell wall of campylobacter jejuni contain?

lipooligosaccharide (LOS)

what is the oxygen preference of campylobacter jejuni?

microaerophilic (requires reduced oxygen levels and CO2 for optimal growth, grows better at 42C than 37C)

t/f campylobacter jejuni has a capsule and flagella

true

how is campylobacter jejuni transmitted?

oral-fecal route, ingestion of water or food, unpasteurized milk contaminated with animal feces, domestic animals, including cattle/poultry/dogs are the source of organisms for humans

t/f campylobacter jejuni is NOT a major cause of diarrhea in the US?

false- is a major cause with estimates 1.3 million cases/year and ~76 deaths

what damage does campylobacter jejuni cause?

gastroenteritis, foul-smelling diarrhea followed by bloody stools with leukocytes, fever and severe abdominal pain (mimics acute appendicitis), septicemia and dissemination to multiple organs can occur but is rare, guillain-barre syndrome (complication of infections, due to cross-reactive antibodies)

what virulence factors does campylobacter jejuni have?

adhesins, cytotoxic enzymes, enterotoxins, roles of virulence factors in pathogenesis is not clear

how can you prevent and treat campylobacter jejuni?

prevention: good hygiene, food processing and preparation

treatment: usually supportive care (fluids and electrolytes) is sufficient but antibiotics can be used in serious cases

is there a vaccine for campylobacter jejuni?

no

what shape is helicobacter pylori?

curved rods

is helicobacter pylori motile?

yes, has flagella

what does helicobacter pylori cause?

urea breath

how is helicobacter pylori transmitted?

acquired by ingestion but has not been isolated from food, water or stool, clustering of infection is observed in families (suggests person-person transmission), can be present as persistent infection in humans

what damage can helicobacter pylori cause?

carriage is usually asymptomatic, but gastritis and peptic ulcer disease are possible, and if prolonged can develop gastric carcinoma

what virulence factors does helicobacter pylori have?

urease, mucinase, vacuolating cytotoxin A, cytotoxin CagA

urease

breaks down urea and produces ammonia, ammonia neutralizes gastric acid and enables survival of the organism

vacuolating cytotoxin A (vacA)

causes damage to epithelial cells by creating vacuoles

cytotoxin CagA

enters and interferes with cell cytoskeletal structure

how can you treat helicobacter pylori infection?

broad spectrum antibiotics

how can you prevent helicobacter pylori infections?

no definitive preventative measures known yet but food consumption habit or diet changes are suggested

is there a vaccine for helicobacter pylori?

no

Glucose and water is an effective treatment to rehydrate patients who lose up to

12 to 15 liters of fluid per day with watery, non-bloody diarrhea due to

malabsorption in the small intestine caused by:

A. Salmonella typhi.

B. Enterohemorrhagic E. coli (EHEC)

C. Campylobacter jejuni.

D. Vibrio cholerae.

E. Shigella sonnei.

D. Vibrio cholerae.