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Salmonella enterica ssp. enterica

Salmonella enterica on Endo agar with biochemical slope

Four different serotypes of Salmonella enterica ssp. enterica on Endo agar with biochemical slope (see here). Glucose degradation is accompanied with formation of acid compounds (red slope) and gas production (serotype Typhi without gas). All strains are lactose negative and conspicuous is strongly positive reaction around mannitol tablet and H2S production with formation of black precipitate under glass and in area of loop punctures. Serotype Typhi and Typhimurium isolated from hemocultures. Highly mucoid strain of serotype Enteritidis isolated from a patient with urinary infection.

Salmonella enterica is a rod shaped, flagellated, aerobic, Gram-negative bacterium, and a member of the genus Salmonella. S. enterica has an extraordinarily large number of serovars or strains—over 2000 have been described. The biomedically most relevant subspecies is called S. enterica ssp. enterica, whose following Serovars have special clinical significance in human disease:

Salmonella enterica Serovar Typhi (historically elevated to species status as S. Typhi) is the disease agent in typhoid fever. Salmonella enterica Serovar Typhimurium (also known as S. Typhimurium) can lead to a form of human gastroenteritis sometimes referred to as salmonellosis.
Salmonella enterica Serovar Paratyphi A is associated with paratyphoid fever. It is sometimes known as Salmonella Paratyphi.

Most cases of salmonellosis are caused by food infected with S. enterica, which often infects cattle and poultry, though also other animals such as domestic cats and hamsters have also been shown to be sources of infection to humans. However, investigations of vacuum cleaner bags have shown that households can act as a reservoir of the bacterium; this is more likely if the household has contact with an infection source, for example members working with cattle or in a veterinary clinic. Raw chicken and goose eggs can harbor S. enterica, initially in the egg whites, although most eggs are not infected. As the egg ages at room temperature, the yolk membrane begins to break down and S. enterica can spread into the yolk. Refrigeration and freezing do not kill all the bacteria, but substantially slow or halt their growth. Pasteurizing and food irradiation are used to kill Salmonella for commercially-produced foodstuffs containing raw eggs such as ice cream. Foods prepared in the home from raw eggs such as mayonnaise, cakes and cookies can spread salmonella if not properly cooked before consumption.

Abbreviated from Wikipedia.

COLONY MORPHOLOGY

salmonella enterica salmonella enterica salmonella enterica salmonella enterica
salmonella enterica salmonella enterica salmonella enterica salmonella enterica
salmonella enterica salmonella enterica salmonella enterica salmonella enterica
salmonella enterica salmonella enterica salmonella enterica  
image general description
GRAM-NEGATIVE RODS
MOTILE
NONSPOREFORMING
CATALASE: POSITIVE
OXIDASE: NEGATIVE
FACULTATIVELY ANAEROBIC

BASIC TESTS
FOR IDENTIFICATION

MacConkey growth+
Indole production-
Methyl red+
Voges-Proskauer-
Citrate(Simmons)
(depends on serotype!!
e.g., serotype Typhi = "-")
+
Hydrogen sulfide(TSI)
(depends on serotype!!)
+
Urea hydrolysis-
Lysine decarboxylase
(serot. Paratyphi A
negative)
+
Arginine dihydrolaseD
Ornithine decarb.
(depends on serotype!!;
e.g., serotype Typhi = "-")
+
Motility (36 °C)
(depends on serotype!!)
+
D-glucose/gas
(depends on serotype!!
e.g., serotype Typhi "+/-")
+/+
D-mannitol fermentation+
Sucrose fermentation-
Lactose fermentation-
D-sorbitol fermentation
(depends on serotype!!)
+
Cellobiose-
Esculin hydrolisis-
Acetate utilization-
ONPG test-
 
+ positive ( > 90% of strains are positive)
D most positive (51 - 89%)
d most negative (11 - 50%)
- negative (0 - 10%)

ANTIBIOTIC
TREATMENT

Should be always guided by
in vitro susceptibility
tests!!

Gram-negative rods drawing

Gastroenteritis

Usually no ATB treatment necessary for uncomplicated diarrheal illness.

If treated:
ampicillin
amoxicillin
trimethoprim-sulfamethoxazole

Alternative

ciprofloxacin
chloramphenicol
ceftriaxone

Typhoid fever

chloramphenicol
ampicillin
amoxicillin
trimethoprim-sulfamethoxazole

Alternative

fluoroquinolones
(e.g., ciprofloxacin)
cefotaxime
ceftriaxone
list of anntibiotics
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Salmonella sp.

Salmonella enterica

Salmonellosis

Typhoid fever

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