ENTEROBACTERIACEAE
The Enterobacteriaceae are usually considered to be only transiently ,present in the normal oral cavity ,and when their found their numbers are so small ,so that it unlikely play any important role in the mechanisms of the biological balance in the oral ecosystemEnterobacteriaceae Genera
ESCHERICHIA KLEBSIELLA SALMONELLA SHIGELLAENTEROBACTER SERRATIA PROTEUS CITROBACTER
General Characteristic :1-Gram negative, rods or bacilli . 2- most genus are motile ( Peritrichous flagella ) except Shigella & Klebisella. 3- Non spore forming . 4- Grow aerobically of facultative anaerobic. 5- Catalase ( + ) , oxidase ( - ) . 6- all species are fermentation glucose . 7-all Enterobacteriaceae produce similar growth on blood agar and chocolate agar are large, gray and smooth colonies , klebisella and Enterobacter may be mucoid colonies.
Serologic identification based on presence or absence of several antigenic structures
Oantigen: somatic antigen, heat-stable lipopolysaccharide cell wall antigen K antigen:capsular antigen heat labile capsular polysaccharide that occurs in about 100 different antigenic type H antigen: flagellar antigen, flagella of motile speciesClassification the family depending to the lactose fermentation on MacConkey agar : 1-Lactose fermentation.EX : E . coli, Klebisella spp. Colonies appear pink.2- Non – lactose fermentation.EX : Salmonella spp. , Shigella spp. .
1. Escherichia coli :
Serology of E.coli: According to the cell wall (O antigen) over 160 types recognized. According to the flagellar (H antigen) 55 types. Making over 8000 possible O-H seotypes. Some E.coli types are capsulatedPathogenicity of E.coli
1-urinary tract infection.2-diarrhoeal diseases.Diarrhoeal –producing E.coli can be divided into four types: enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC) , enterohemorrhagic E. coli (EHEC).3-neonatal miningitis and septicaemia4-Periapical root channel infection. .Culture
1-Mac Conkey agar : Pink colonies due to the lactose fermentation 2-Blood agar : Some strains show beta haemolysis 3-Eosin methylene blue agar ( EMB ) : green to black with metallic sheen.2. Klebisella Spp.
Characteristics : G- , thick to short rod, non motile, capsulated, ( polysaccharide ). Biochemical reaction : Catalase ( + ) . oxidase ( - ) , LF , Urease ( + ) , IMVIC : - - + +Culture :
Blood agar : mucoid colonies . MacConkey agar : large mucoid, pink colonies ( mucoid because accumulation of capsule ) .pathogenicity
Klebsiella pneumonia may sometimes cause a severe destructive pneumonia , urinary tract infection, septicemia and meningitisTable to differentiate between E. Coli & klebisella .
klebisella
E. Coli
* capsulated
* non capsulated
* thick and short
* Slender and long
* non motile
* motile
* IMVIC - - + +
* IMVIC + + - -
* Urease ( + )
* Urease ( - )
* mucoid Colonies
* Colonies not mucoid
3. Salmonella spp.
Characteristics :G- , rod , motile , All species except S.typhi are Non –capsulate , non sporing .Biochemical reaction :Catalase ( + ) . oxidase ( - ) , fermentation many carbohydrate forming acid and gas , IMVIC : - + - + .Species S. typhi typhoid fever S.paratyphi A,B,C Paratyphoid fever S. typhimurium food posining
Typhoid Fever
Salmonella typhi Pathogenesis contaminated food or water Bacteria spread in the body in phagocytes 1-3% recovered patients become carriers, harboring Salmonella in their gallbladder Symptoms: severe fever/headache weakness, abdominal pain and rashDiagnosis of typhoid fever Blood cultures are positive during the first week and after the second week Stool cultures and sometimes urine cultures are positive after the second week The Widal test is a serological test for antibodies against Salmonella typhi. rise in titer .
Culture :Mac Conkey agar : Colonies colourless ( NLF )Salmonella – Shigella agar : brown colonies with black center ( SS agar ) .
S. typhi produce H2S : 1-S release from sodium thiosulfate by bacteria enzyme action . 2-Coupling S with H ( found on media ) to form H2S . 3-Delecting H2S by iron lead to produce heavy sulfides that appear black precipitate. H2S + FeSo4 FeS black
Bismuth Sulfate agar :
To differentiate between the species of salmonella S. typhi black colonies Other species of salmonella brown colonies4. Shigella spp.
Characteristics :G- , rods , non motile , non capsulated .Biochemical reaction :Catalase ( + ) . oxidase ( - ) , TSI K/A with NO gasUrea –Motility -All ferment mannitol except S. dysenteriaeS. sonnei may show delayed lactose fermentation .
Species :
Contains four species that differ antigenically S. dysenteriae S. flexneri S. Boydii S. sonnei .Shigella
Clinical significance Causes shigellosis or bacillary dysentery. Transmission is via the fecal-oral rout under crowded conditions. The infective dose required to cause infection is very low (10-200 organisms). There is an incubation of 1-7 days followed by fever, cramping, abdominal pain, and watery diarrhea (due to the toxin)for 1-3 days.
The severity of the disease depends upon the species which infected with it. S. dysenteria is the most pathogenic followed by S. flexneri, S. sonnei and S. boydii.
Culture
MacConkey agar : Pale colonies except Sh. sonnei after 48hr . SS agar : Colourless without black center .5. Proteus spp.
Characteristics : G- , motile , swarming present only in the absence of bile salt , . Biochemical reaction : Catalase ( + ) . oxidase ( - ) , urease ( + ) , NLF .Culture
1-nutrient agars produce swarming, fishy odor 2-urea agar.Species : P. vulgaris . P. mirabilis . P. morganii . P. rettgeri .. Virulence factors Urease , the ammonia produced may damage the epithelial cells of the UT Clinical Significance UT infections, as well as pneumonia, septicemia, and wound infections
6. Citrobacter :
Species :C.freandii C.koseri C.amalonaticus Pathogenicity : U. T. I . C.koseri associated with meningitis and brain abscesses in infant
.7. Enterobacter :
Species :
E.aergenes E.clocae E.taylorae Pathogenicity Gastroenteritis Septecemia Liver Abscesses UTI Endocarditis Meningitis Pneumonia DiarrheaEMB PLATE: E. coli is seen on the left and E. aerogenes on the right
8.Serratia spp.Characteristics : G- , bacilli, Produce characteristic red pigment, especially when cultures are left at room temperature 2-Biochemical reactions vp( + ) . gelatinase ( - ) , citrate( + ) , lactose fermenter .