Chapter 23 Lecture 2
Bacterial Gastroenteritis: Campylobacter Diarrhea
Is responsible for more cases of diarrhea that send people to the docs in the US than any other bacterium.
Pathogen and virulence factors
Caused by Campylobacter jejuni, Gram – slightly curved bacterium with polar flagella
Virulence factors: are not fully understood but they do know that the bacterium possesses adhesins, cytotoxins, and endotoxin
The bacterium survives inside cells after being endocytized
Pathogenesis and epidemiology
Virulence factors enable for colonization in the jejunum, ileum, and colon causing bleeding lesions and inflammation
Chickens are the main source of human infections- this makes it the primary source for humans
Estimated one million people have campylobacter diarrhea each year. 100 die
Diagnosis, treatment, and prevention
Diagnosis is based on signs and symptoms and evidence of bacterium in stool
Most cases resolve without treatment if not supportive therapy and erythromycin
Prevented with proper hygiene after handling raw poultry
Bacterial Gastroenteritis: C. diff. (Antimicrobial-Associated) Diarrhea
A severe form of diarrhea with intense inflammation and formation of lesions in the colon. Will get when on an antimicrobial
Signs and symptoms
5-10 clear, foul smelling watery stools per day that can lead to
Pseudomembranous colitis occurs in severe cases
Life threatening more than 10 bloody stools per day with the formation of pseudomembrane
Pathogen and virulence factors
Caused by Clostridium difficile which is part of the normal microbiome of the large intestine.
Antimicrobial use facilitates (helps with the) overgrowth of C. difficile
C. difficile produces two toxins Toxin A and Toxin B
C-Diff does not move into blood but stays in colon making the 2 toxins
Pathogenesis
Toxins help bring on the inflammation and pseudomembrane formation
Epidemiology
By-product of modern medicine
Any antimicrobial can trigger the disease
CDC estimates more than 11 million cases occur in the US with ~2 million deaths
Shed the bacterium in the stool which can infect hospital staff and other pts
Diagnosis, treatment, and prevention
Diagnosis is based on presence of bacterial toxin in stool- sometimes we need to do a colonoscopy to see the pseudomembrane
Treated with antimicrobials, experimental fecal transplants. Antidiarrheal drugs need to be avoided because diarrhea is beneficial as it eliminates the cells and toxins
Fecal transplantation- inject a liquid containing fecal material from a close relative/spouse via NG tube or enema to reestablish a normal microbiome
Avoid unnecessary use of antimicrobials, excellent hand hygiene practices . Remember Clostridium are resistant to most disinfectants.
Bacterial Gastroenteritis: Salmonellosis and Typhoid Fever
Pathogen and virulence factors
Caused by Salmonella enterica serotypes Scientists have identified more than 2500 unique serotypes (strains)
Serotypes Typhi and Paratyphi cause typhoid fever by entering the blood passing through the intestinal cells into the bloodstream where it is phagocytized, then carry the pathogen to the liver, spleen, bone marrow and gallbladder. In some cases, the bacterium perforate the intestinal wall and bacteria enter the abdominal cavity causing peritonitis
Serotypes Enteritidis and Typhimurium cause salmonellosis
Bacteria tolerate acidity of the stomach and pass to the intestine there it attaches via specific adhesions
Toxins disrupt numerous cellular activities like mitochondria, inhibit phagocytosis and rearrange the cytoskeleton of eukaryotic cells
Pathogenesis and epidemiology
Typhoid fever is acquired by contaminated food or water with feces from a carrier
Salmonellosis is often acquired by consuming contaminated eggs 1/3 of chickens carry salmonella
Diagnosis, treatment, and prevention
Diagnosis is made by finding Salmonella in stool use the xTAG GPP nucleic acid test
Salmonellosis is usually self-limiting within a week. Replace lost fluids and electrolytes
Typhoid fever can be treated with antimicrobial drugs have a sustained fever of 104, accompanied by weakness, abdominal pain, headache, and loss of appetitie
Prevented with proper hygiene, especially in the kitchen.
CDC recommends, “Boil it, cook it, peel it, or forget it”; that is boiling drinking water, and avoid uncooked foods except fruits and vegetables that can be peeled.
People should also wear gloves when cleaning and handling pet reptiles
Bacterial Gastroenteritis: Cholera
Since 1817 there have been 7 pandemics of cholera
Current epidemic (India) may spread worldwide for the 8th pandemic
An infectious and often fatal bacterial disease of the small intestine that one can get from infected water supplies
Pathogen and virulence factors
Caused by Vibrio cholerae
Occurs in salt- and freshwater (only species that can survive both) naturally, which it prefers warm, salty alkaline water and often in association with shellfish
In saltwater it survives by forming biofilms which are not infective but when in freshwater the biofilms fall apart and a single Vibrio cell becomes motile and infective
Environment within the human body activates some Vibrio genes
Most important virulence factor is production of a potent exotoxin/ poison cholera toxin This is a virulence factor that is primarily responsible for the s/s of cholera
Pathogenesis and epidemiology
Pandemics have occurred throughout history and death can occur within hours if left untreated.
Diagnosis, treatment, and prevention
The major symptoms of cholera re attributed to the activation of adenylate cyclase. This enzyme converts ATP into cyclic AMP which stimulates the active secretion of electrolytes from the cell into the intestinal lumen, Water follows the movement of those ions from the cell via osmosis and this is where you get your severe fluid and electrolyte losses
Diagnosis is based on presence of "rice-water" stool
Treated with supportive care and administration of doxycycline
Available vaccine provides only short-lived immunity
Proper hygiene is an important preventive measure
Bacterial Food Poisoning (Intoxication)
Food poisoning is a broad term used to refer to consuming either pathogens or their toxins. It is an intoxication disorder because the toxins produced by the bacteria grow in the food are ingested long with the food.
Signs and symptoms
Nausea, vomiting, diarrhea, cramping, discomfort bloating, loss of appetite and fever.
Pathogen and virulence factors
Caused by Staphylococcus aureus
Virulence factors include five enterotoxins
Pathogenesis and epidemiology
Outbreaks are associated with social functions
Diagnosis, treatment, and prevention
Diagnosis is based on signs and symptoms
Treated with fluid and electrolyte replacement
Proper hygiene can reduce incidence