salmonella Flashcards
characteristics of salmonella
- gram neg
- rod shaped
- facultatively anaerobic
- motile with peritrichous flagella
- non lactose fermenter
is salmonella a zoonotic pathogen?
yes
where does salmonella naturally reside?
GI tract of all animals, including fish, and reptiles. Very hardy animals
what are salmonella’s antigenic characteristics?
- O-antigen
- H-antigen
- Vi (virulence or capsular) - S. Dublin
which subspecies of salmonella is responsible for 99% of animal and human infections?
subspecies 1 (enterica)
what is the mode of infection of salmonella?
- oral transmission
- transovarian transmission (ovary to egg in poultry (yolk))
- flies
what is a predisposing factor for salmonella
STRESS
-shipping, cold, overcrowding, surgery, antimicrobial therapy, etc
what are two major sources of acquiring salmonella?
infected animals and asymptomatic carriers
what are the virulence factors of salmonella?
- enterotoxins
- cytotoxins
- LPS
- flagella
- siderophore
- heat shock proteins
what are the characteristics of the enterotoxins of salmonella?
- cholera-like; (LT)
- heat labile
- induces fluid secretions
what are the characteristics of the cytotoxins of salmonella?
- damage intestinal cells
- three types:
1. heat labile
2. low MW protein
3. cell associated hemolysin
what are the characteristics of the LPS of salmonella?
- mutants that lack LPS are less virulent
- cause vascular damage and thrombosis in the intestine
- responsible for systemic signs: fever, DIC, circulatory collapse, and shock
what are the characteristics of the siderophores of salmonella?
-iron chelators
what are the characteristics of the HSPs of salmonella?
- outer membrane proteins produces in response to stress
- essential for the survival in macrophages
what are the two types of salmonella infections?
- intestinal infections
- systemic infections
what is the pathogenesis of intestinal infections?
- colonization of the intestine
- invasion and damage of the intestinal epithelium
- stimulation of fluid production and excretion
what is the colonization of the intestine
- adherence to the enterocytes (receptor mediated)
- larger numbers of organisms are required to initiate the disease
- stress is a critical factor
describe the invasion of the intestinal epithelium of salmonella
- enter the cells through the microvilli or via the junction complexes
- multiply and atack the adjacent cells
- enter lamina propria and are engulfed by macrophages
what is a key feature to the salmonella’s invasiveness?
ability to survive and multiply inside phagocytes
what is salmonella enteritis?
most often ileum is affected, later spreads to jejunum and colon
- shortening and distortion of villi
- degeneration of enterocytes
- increased emptying of goblet cells (mucus productin)
- neutrophilic infiltration and migration into the lumen (neutrophilic shedding in the feces)
how does salmonella stimulate fluid production and excretion?
- net secretion of water, bicarbonate and chloride into the lumen
- loss of epithelial cells results in impaired absorption
“diarrhea”
what is the key virulence factor of salmonella?
LPS
what does salonellosis cause?
- enteritis
- septicemia
- abortion
- food borne gastroenteritis in humans (diarrhea)
what serotypes cause bovine salonellosis
S. Dublin and S. Typhinurium
what serotypes cause equine salmonellosis
- S. Typhimurium
- S. Newport
- S.Enteritidis
- S. Heidelberg
what serotypes cause swine salmonellosis?
- S. Choleraesuis
- S. Typhimurium
what serotypes cause ovine salmonellosis?
- S. Abortusovis
- S. Typhimurium
- S. Dublin
what serotypes cause canine and feline salmonellosis?
- not very common
- racing greyhounds can get it from eating contaminated raw meat
what causes avian salmonellosis
- S. Pullorum
- S. Gallinarum
- S. Typhimurium (food poisoning)
what are pullorum disease and fowl typhoid?
- in chickens anturkeys
- rare in commercial farms
- septicemic diseases
- transmitted through the egg “transovarian transmission”
what causes pullorum disease?
- salmonella pullorum
- adult birds are resistant bu are carriers
- excreted in feces
- mode of infection: transovarian, ingestion, inhalation
- lesions: caseous areas in the gizzard or lungs
- diagnosis: serology (agglutination test)
what causes fowl typhoid?
- salmonella gallinarum
- chickens and turkeys
- excreted in feces
- mode of infection: transovarian, ingestion, inhalation, or tick-borne
what are the signs of fowl typhoid?
- acute septicemic disease, weakness, hyperexcitability, paresis and diarrhea
- lesions: meningitis, multiple small necrotic areas in the liver and heart
what are a few mandatory reportable diseases by the National Eradication Program?
Pullorum and Fowl typhoid
what causes avain salmonellosis?
- S. Typhimurium
- S. Anatum
what is the immunity toward salmonella?
- both humoral and cell mediated
- secretory IgA may provide local immunity
- serum IgG against O-specific polysaccharide confers prodection
what is the best protection against salmonella?
-live attenuated, orally administered vaccine
how do you treat salmonellosis
antibiotics are useful (must conduct sensitivity test)
-fluid and electrolyte therapy
why should you conduct a sensitivity test?
- multiple antibiotic resistance is common
- the wrong antibiotic may:
- lead to systemic infection
- prolong fecal shedding
what are some control measures to prevent salmonellosis?
- reduce contamination of the environment
- eliminate source of infection
- minimizing stress
what are the three sources of salmonellosis in humans?
- typhoid fever
- enteric fever
- gastroenteritis (most common)
gastroenteritis characteristics
- zoonotic disease
- symptoms: diarrhea, abdominal cramps, chills, fever, nausea, vomiting, headache
what two serotypes are multi-drug resistant (MDR) Salmonella?
- Typhimurium DT 104
- Newport
