03 - Enterobacteriaceae Family 14 - 19 Flashcards
What is the gram stain of Salmonella spp.?
Gram-negative bacillus
(1) Member of the family Enterobacteriaceae
(2) One major species: Salmonella enterica
(3) Over 2500 serotypes / strains characterized by “O” and “H” antigens (most common strains have been given what appear to be “species” names). EXAMPLES: Salmonella enterica, serovar Typhi; etc etc
(4) 95% of isolates are in antigenic groups A, B, C1, C2, D, E, F, G, H, and Vi. In the USA, antigenic groups B and D predominate (40% of about 50,000 reported cases annually)
Salmonella
what is the one major species of Salmonella?
Salmonella enterica
How many serotypes of Salmonella and characterized by what?
Over 2500 serotypes (strains characterized by “O” and “H” antigens
Salmonella
Transmission and Source of infection?
– ingestion of contaminated food and water
(1) Frequent normal flora of poultry (turkeys, chickens), livestock, rodents, reptile (turtle)
(2) Transmitted by contaminated food and water, especially
(a) Meat products not properly cleaned or cooked
(b) Eggs and dairy products
(c) Other foods prepared on contaminated surfaces (e.g. cutting boards)
(3) Many bacteria are destroyed by stomach acids, so ingestion of large quantity are needed to initiate infection
Four pathogens that cause ACUTE gastroenteritis?
Salmonella enteritidis
Staph aureus
Bacillus cereus (1-6hrs after ingestion vomit THEN diarrhea within 6 -24 hrs )
Vibrio vulnificus
Pathogenicity of Salmonella enteritidis
i. invade where causing rxn where?
ii. symptoms?
i. Bacteria invade the intestinal mucous membranes causing an ACUTE INFLAMMATORY REACTION in the subepithelial tissue
ii. Symptoms include sudden onset of diarrhea (rarely bloody) and vomiting along with fever about 6 to 48 hours after consumption of contaminated food or water; symptoms persist 2 to 7 days
Generally no ABX
Acute gastroenteritis (enterocolitis syndrome) (Salmonella food poisoning) – caused by ?
Salmonella enteritidis (and numerous other serotypes)
gastroenteritis AKA
enterocolitis syndrome
which pathogen causes gastroenteritis and is similar to Salmonella?
Campylobacter jejuni
Enteric Fever (Typhoid fever) caused by
Salmonella Typhi & Paratyphi
Pathogenicity of Typhoid Fever AKA ?
i. Bacteria invade epithelial cells of terminal portion of small intestine and then into the lymphoid follicles where they multiply
ii. Bacteria migrate to the blood stream, the fever period begins, and rose spots appear on the skin. Local necrosis can lead to hemorrhage and lesions
• Fever begins 10-14 days after ingestion of bacteria
• Headache, myalgia, malaise persist for about 5-10 days
• Gastrointestinal symptoms begin about 15-20 days after ingestion of bacteria
iii. Localization of bacteria in gallbladder, spleen, liver, and sometimes bones
iv. Carrier state (excretion for 3 months) develops in about 5% of patients - Gallbladder is where most bacilli are located in carriers
AKA Salmonella Typhi & Paratyphi
Tx and control of Salmonella Typhi & Paratyphi -(Enteric Fever / Typhoid Fever)
ABX useful lik [Chloramphenicol (14 days), amoxicillin, or ceftriaxone (IV) (5 days), or trimethoprim/sulfamethoxazole]
(1) Culture and biochemical identification and “O” antigenic group designation
(2) Antimicrobic susceptibility test needed to determine drug resistant strains
(1) Culture and biochemical identification with antigenic identification
(2) Antimicrobic susceptibility testing needed to determine antibiotic resistant strains
a. Gram-negative bacillus; member of the family Enterobacteriaceae
b. Four species are determined by antigenic grouping
Shigella spp.
Shigella spp. name all four species…
(1) S. dysenteriae – Antigenic group A – Least frequently isolated in the U.S. – causes a more severe form of dysentery than the other species
(2) S. flexneri – Antigenic group B – 25% of Shigella species isolated in the U.S.
(3) S. boydii – Antigenic group C – Rare in U.S., only 0.6% of isolates
(4) S. sonnei – Antigenic group D – Most frequent isolate (74% of isolates)
Transmission and Epidemiology of Shigella spp.
(1) Transmitted by fecal-oral route
(2) Sources of infection – ingestion of food and water contaminated with feces
(3) Infection can be establish by about 200 bacteria
(4) Children under 10 years of age account for over 2/3 of all cases
dysentery w/o cellulitis means it’s of this species
shigella
Transmission and Epidemiology of shigella
(1) Transmitted by fecal-oral route
(2) Sources of infection – ingestion of food and water contaminated with feces
(3) Infection can be establish by about 200 bacteria
(4) Children under 10 years of age account for over 2/3 of all cases
Pathogenicity – Shigellosis or Bacillary Dysentery –enterocolitis syndrome
(1) Incubation: 12-48 hours depending on dose of microbes (10-100 bacteria) with symptoms lasting 1-3 days
(2) Toxin production
(a) Endotoxin - potent and is present in all strains
(b) Exotoxin
i. Produce Shiga Toxin (AB-type) – disrupts protein synthesis – damages the intestinal epithelium
ii. Neurotoxin and enterotoxin produced by S. dysenteriae type I
iii. Some strains of S. flexneri produce enterotoxins
(c) Invasive enzymes
(3) Symptoms: Diarrhea (liquid stools), lesions in the colon producing pus and blood in feces (dysentery), and fever
Disease Progression of Shigella spp
Disease progression
(a) Organisms attach to & penetrate intestinal mucosal epithelial cells
(b) Bacteria multiply intracellularly causing mucosal epithelial cells to die and slough off with some bleeding
(c) Bacteria release an endotoxin that stimulates fever and an inflammatory response causing local damage (ulcerations, pus, and bleeding)
(d) Exotoxin causes fluid loss (diarrhea)
Shigella spp.
Treatment and control – Rehydration and electrolyte replacement; acute/severe illness is usually treated with…
a third-generation cephalosporin (widespread resistance to others)