- E. coli
- Salmonella
- Pseudomonas
- Staphylococcus
- ๐๐ฌ๐๐ก๐๐ซ๐ข๐๐ก๐ข๐ ๐๐จ๐ฅ๐ข (๐. ๐๐จ๐ฅ๐ข) ๐๐จ๐ง๐๐ข๐ซ๐ฆ๐๐ญ๐ข๐จ๐ง
๐๐๐ฆ๐ฉ๐ฅ๐ ๐๐ซ๐๐ฉ๐๐ซ๐๐ญ๐ข๐จ๐ง: Inoculate the sample on MacConkey agar or EMB agar. Colony
Characteristics: E. coli appears as pink colonies on MacConkey agar (lactose fermentation)
and metallic green sheen on EMB agar.
๐๐ข๐จ๐๐ก๐๐ฆ๐ข๐๐๐ฅ ๐๐๐ฌ๐ญ๐ฌ
๐๐ง๐๐จ๐ฅ๐ ๐๐๐ฌ๐ญ: Positive (Inoculate a tryptone broth and add Kovac’s reagent a red ring indicates
indole production)
๐๐๐ญ๐ก๐ฒ๐ฅ ๐๐๐ (๐๐) ๐๐๐ฌ๐ญ: Positive
๐๐จ๐ ๐๐ฌ-๐๐ซ๐จ๐ฌ๐ค๐๐ฎ๐๐ซ (๐๐) ๐๐๐ฌ๐ญ: Negative
๐๐ข๐ญ๐ซ๐๐ญ๐ ๐๐ญ๐ข๐ฅ๐ข๐ณ๐๐ญ๐ข๐จ๐ง ๐๐๐ฌ๐ญ: Negative - ๐๐๐ฅ๐ฆ๐จ๐ง๐๐ฅ๐ฅ๐
๐๐๐ฆ๐ฉ๐ฅ๐ ๐๐ซ๐๐ฉ๐๐ซ๐๐ญ๐ข๐จ๐ง: Inoculate on Xylose Lysine Deoxycholate (XLD) agar or Hektoen Enteric agar.
๐๐จ๐ฅ๐จ๐ง๐ฒ ๐๐ก๐๐ซ๐๐๐ญ๐๐ซ๐ข๐ฌ๐ญ๐ข๐๐ฌ:On XLD agar, Salmonella produces red colonies with black centers (due to hydrogen sulfide production).
๐๐ข๐จ๐๐ก๐๐ฆ๐ข๐๐๐ฅ ๐๐๐ฌ๐ญ๐ฌ
๐๐๐ (๐๐ซ๐ข๐ฉ๐ฅ๐ ๐๐ฎ๐ ๐๐ซ ๐๐ซ๐จ๐ง):Alkaline slant/acid butt with HโS production (blackening).
๐๐ซ๐๐๐ฌ๐ ๐๐๐ฌ๐ญ: Negative
๐๐ฒ๐ฌ๐ข๐ง๐ ๐๐๐๐๐ซ๐๐จ๐ฑ๐ฒ๐ฅ๐๐ฌ๐ ๐๐๐ฌ๐ญ: Positive
๐๐ข๐ญ๐ซ๐๐ญ๐ ๐๐ญ๐ข๐ฅ๐ข๐ณ๐๐ญ๐ข๐จ๐ง ๐๐๐ฌ๐ญ: Positive
๐๐๐ซ๐จ๐ฅ๐จ๐ ๐ข๐๐๐ฅ ๐๐๐ฌ๐ญ๐ข๐ง๐ : Agglutination with specific Salmonella O and H antisera
๐๐จ๐ฅ๐๐๐ฎ๐ฅ๐๐ซ ๐๐๐ญ๐ก๐จ๐๐ฌ: PCR targeting genes like invA confirms Salmonella. - ๐๐ฌ๐๐ฎ๐๐จ๐ฆ๐จ๐ง๐๐ฌ ๐๐๐ซ๐ฎ๐ ๐ข๐ง๐จ๐ฌ๐
๐๐ฌ๐จ๐ฅ๐๐ญ๐ข๐จ๐ง: Use Cetrimide agar or Pseudomonas isolation agar
๐๐ข๐จ๐๐ก๐๐ฆ๐ข๐๐๐ฅ ๐๐๐ฌ๐ญ๐ฌ
๐๐ฑ๐ข๐๐๐ฌ๐ ๐๐๐ฌ๐ญ: Positive (distinguishes it from Enterobacteriaceae).
๐๐ซ๐จ๐ฐ๐ญ๐ก ๐๐ญ ๐๐ยฐ๐: P. aeruginosa can grow at 42ยฐC.TSI: K/K (alkaline slant and butt, no sugar fermentation).
๐๐๐ฅ๐๐ญ๐ข๐ง ๐๐ข๐ช๐ฎ๐๐๐๐๐ญ๐ข๐จ๐ง: Positive
๐ ๐ฅ๐ฎ๐จ๐ซ๐๐ฌ๐๐๐ง๐๐: P. aeruginosa shows fluorescence under UV light (due to pyoverdine production).
๐๐จ๐ฅ๐๐๐ฎ๐ฅ๐๐ซ ๐๐๐ญ๐ก๐จ๐๐ฌ: PCR detecting genes like oprL or toxA confirms Pseudomonas aeruginosa. - ๐๐ญ๐๐ฉ๐ก๐ฒ๐ฅ๐จ๐๐จ๐๐๐ฎ๐ฌ ๐๐ฎ๐ซ๐๐ฎ๐ฌ
๐๐๐ฆ๐ฉ๐ฅ๐ ๐๐ซ๐๐ฉ๐๐ซ๐๐ญ๐ข๐จ๐ง: Inoculate on Mannitol Salt Agar (MSA) or Blood Agar.
๐๐จ๐ฅ๐จ๐ง๐ฒ ๐๐ก๐๐ซ๐๐๐ญ๐๐ซ๐ข๐ฌ๐ญ๐ข๐๐ฌ: S. aureus ferments mannitol on MSA, producing yellow colonies. On blood agar, it forms golden-yellow colonies with ฮฒ-hemolysis.
๐๐ข๐จ๐๐ก๐๐ฆ๐ข๐๐๐ฅ ๐๐๐ฌ๐ญ๐ฌ
๐๐จ๐๐ ๐ฎ๐ฅ๐๐ฌ๐ ๐๐๐ฌ๐ญ: Positive (S. aureus is coagulase-positive).
๐๐๐ญ๐๐ฅ๐๐ฌ๐ ๐๐๐ฌ๐ญ: Positive (all Staphylococci are catalase-positive).DNase Test: Positive.
๐๐๐ซ๐จ๐ฅ๐จ๐ ๐ข๐๐๐ฅ ๐๐๐ญ๐ก๐จ๐๐ฌ: Latex agglutination tests for protein A and clumping factor.
๐๐จ๐ฅ๐๐๐ฎ๐ฅ๐๐ซ ๐๐๐ญ๐ก๐จ๐๐ฌ: PCR for the mecA gene (for methicillin-resistant Staphylococcus aureus,MRSA) or nuc gene (thermonuclease) confirms S. aureus.
These tests form the basis for confirming these specific pathogens in microbiological samples.
