Enteric Pathogens (Salmonella Species)

How to differentiate regular E. Coli from E. Coli O157:H7?

Using MacConkey with sorbitol agar. Regular E. Coli will be pink and E. coli O157:H7 will be colorless

What are the two main species of Salmonella?

Salmonella enterica and Salmonella bongori –rare isolate

Salmonella Enterica nomenclature is now based on a?

Continuum of a single species with 6 subspecies and  over 2500 serotypes. Salmonella enterica

What is the most common type of Salmonella enterica?

Salmonella enteric serotype typhi ( causes typhoid fever)

What are the second most common serotypes of Salmonella enterica?

Salmonella enterica serotype paratyphi and Salmonella enterica serotype cholerasesuis

What are Salmonella enterica serotypes based on?

O, H and Vi antigens.

Who uses the nomenclature for Salmonella?

CDC

What are the seven groups of nomenclature based on?

DNA-DNA hybridization

Which group of salmonella cause the most human infections?

Group I with more then 1400 serotypes

What are the most common isolates of salmonella?

Salmonella serotype typhi and Salmonella serotype enteriditis

What are the Salmonella enterica serotypes general characteristics?

Motile

Usually do not ferment lactose or sucrose

Most found in intestine of humans and animals

Infections associated with consumption of fecal contaminated food and water

All produce H2S except for serotype paratyphi

What are the clinical significance of the Salmonella enterica serotypes?

Most serotypes cause salmonellosis

(Acute gastroenteritis or food poisoning)

Usually acquired form ingesting foods of animal origin ( eggs, milk, poultry)

Occasionally acquired from human contact.

Salmonella clinical significance?

Very common source of food poisoning. Many recalled food products due to contamination with Salmonella serotypes

How long does it take for Salmonella to have an effect?

8-36 hours after ingestion

What is required to have salmonella?

A high microbial load for infection

What can happen with salmonella in people?

Self-limiting in health individuals (antibiotics and antidiarrheal agents may prolong symptoms)

What is an exception involving Salmonella serotype paratyphi and serotype typhi?

Animals serve as the reservoir for human infections.

What is a cause of Salmonella serotype typhi?

Typhoid Fever

How is salmonella serotype typhi acquired most often?

Most often acquired while traveling outside the U.S.

Where is salmonella serotype typhi found excusively in?

Humans

When are Blood Cultures positive with Salmonella serotype typhi?

Within 1st or 2nd week of infection

What is the major reservoir for Salmonella serotype typhi?

Is the gall bladder ( removal of gallbladder may be the only solution to carrier state)

What percentage of Salmonella serotype typhi become carriers?

1-2%

Where will carriers shed salmonella serotype typhi?

Carriers will shed bacteria in the stool

Typhoid and Other Enteric Fevers?

Prolonged fever

Bacteremia

Involvement of the RE system, particularly liver, spleen, intestines, and mesentery

Dissemination to multiple organs

Occurs more often in tropical and subtropical countries

Salmonella Culture characteristics?

Culture medium used to detect nonlactose fermenters

EMB, MAC, Desoxycholate

Culture medium used to detect H2S production

SS, HE, XLD, Desoxycholate-citrate agar

Enrichment medium for fecal pathogens

GN broth and Selenite F or Tetrathionate broth

Salmonella Biochemicals?

H2S and lysine decarboxylase positive

Indole and ONPG negative

S. typhi is differentiated from other Salmonella by a negative citrate and ornithine decarboxylase test

Salmonella is PYR negative while Citrobacter is PYR positive

What is the final ID done for Salmonella?

Agglutination testing

What are the Clinical significance's of Salmonella?

´Antibiotic treatment of enterocolitis can result in carrier state

´Neonates with enterocolitis should be treated

´Bacteremia and Typhoid fever should be treated with antibiotics

´Multi-drug resistance is on the rise

´Vaccination and other methods of control