Family Enterobacteriaceae Genus Salmonella spp Lab 16 Genus

Family: Enterobacteriaceae Genus: Salmonella spp Lab. 16

Genus: Salmonella Clinically important serotypes S. typhi &S. paratyphi Enteric fever(typhoid) only in human but not part of normal flora S. choleraesuis Bacteremia & extraintestinal S. typhimurium Salmonellosis

Genus: Salmonella General characteristics: 1 -Grams negative flagellated Motile bacilli or coccobacilli. 2 -Grow on Mac. Conkey's agar non lactose fermentor. 3 -Facultative anaerobic. 4 -Ferment glucose acid and gas 5 -Catalase +ve & oxidase –ve. 6 -Most strains produces hydrogen sulfide (H 2 S).

Genus: Salmonella 7 -Has (O), (H), and (Vi) antigens. Used to classify salmonella into groups; according to (O) Ag into (A, B, C 1, C 2, D& E): A • S. Paratyphi A B • S. Paratyphi B C 1 • S. Choleraesuis D • S. typhi

Genus: Salmonella Laboratory diagnosis 1 -Specimens: according to disease. Gastroenteritis Bacteremia Enteric fever • Stool • Blood (during high fever) • Stool (infrequently +ve) • Blood (+ve in the 2 nd & 3 rd week of disease) • Stool (+ve from 2 nd week on; -ve earlier in disease) • Serum (+ve 2 nd & 3 rd week)

Laboratory diagnosis 2 -Staining: By Grams stain short bacilli or coccobacilli.

Laboratory diagnosis 3 -Culture : at 37 C for 24 -48 h. On differential & selective media. Mac. Conkey's agar non-lactose fermentor.

Laboratory diagnosis � Hektoen enteric (HE) agar. color of medium is green-blue � Selective : because it contain bile salt, dyes (bromthymol blue + acid fuchsin) slow the growth of most non pathogenic G-ve bacilli found in the GIT and allow Salmonella & Shigella to grow. � Differential because of lactose fermentation Salmonella & Shigella non lactose fermentor colorless colonies (same color of HE which is greenblue). If Salmonella produce H 2 S black precipitate within colonies. Others if do grow appears orange because of lactose fermentation.

Laboratory diagnosis �Hektoen enteric (HE) agar. Salmonella spp. on HE (black precipitate)

Shigella spp. on HE (blue - green)

Laboratory diagnosis �Salmonella & Shigella agar. � Selective because of bile salt & brilliant green inhibit G+ve. � Differential because of lactose fermentation Salmonella with H 2 S black colonies � Shigella colorless colonies (same agar color) � Other G-ve appear red colonies

Laboratory diagnosis �Salmonella & Shigella agar. SS agar with both Salmonella & Shigella spp. growth

Laboratory diagnosis � Xylose –lysine- deoxycholate (XLD). Color of medium is red-pink � Selective because of bile salt& Na+ deoxycholate inhibt G+ve &G-ve bacilli that are not enteric pathogens. � Differential because of lactose fermentation (e. g. E. coli) can ferment lactose decreases PH change the phenol red indicator into yellow appears yellow colonies � Pathogenic (Salmonella & Shigella) non lactose fermentor colorless colonies (same medium color) which is red –pink. If salmonella produced H 2 S dark colonies

Laboratory diagnosis � Xylose –lysine- deoxycholate (XLD).

Laboratory diagnosis 4 -Biochemical: (carbohydrate fermentation & H 2 S production). Salmonella ferment glucose only acid &gas; Can be detected by carbohydrate fermentation test by using Durham’s tube or (triple sugar iron or kligler iron agar) agar which can detect carbohydrate fermentation and H 2 S production.

Laboratory diagnosis Triple sugar iron (TSI) • (lactose>sucrose>glucose) +iron +phenol red indicator • The color of uncultured agar is red. Kligler iron agar (KIA) • (lactose>glucose) +iron + phenol red indicator. • The color of uncultured agar is red.

Laboratory diagnosis Interpretation for salmonella on KIA: Salmonella fement only glucose acid produced the butt will be yellow (acidic), the slant (surface) remain (alkaline) red because it is in contact with O 2 which render the acid that produced by glucose fermentation into alkaline. If H 2 S produced bind with iron black color of the butt which can mask the yellow butt.

1 2 Tube Lactose 4 3 Glucose 1 2 3 control -ve +ve 4 +ve Gas H 2 S +ve +ve

Laboratory diagnosis 5 - Molecular method: method like DNA hybridization which the most sensitive & specific but expensive. 6 - Motility test: test by semisolid agar chrisms tree. inverted

Laboratory diagnosis 6 -Serology: Widal test (tube dilution) results �If (O) Ab titer ≥ 1: 160 Infection. �If (H) Ab titer ≥ 1: 160 �If (Vi) Ab titer ≥ 1: 80 Active Past immunization or past infection. Carrier. The test must be repeated at least after 7 -10 days interval for follow up of rising titer for active infection.

Thank you