Lab Diagnosis of GI.pptx

SHAPE OF BACTERIAL CELL: Bacteria are classified by 3 basic groups: 1. Cocci (round) 2. Bacilli (rod) 3. Spirochetes (spiral) Some bacteria are of variable shapes – pleomorphic Shape is determined by rigid cell wall. Arrangement is also important: Cocci in pairs (pneumococci) Cocci in chains (strept...

SHAPE OF BACTERIAL CELL: Bacteria are classified by 3 basic groups: 1. Cocci (round) 2. Bacilli (rod) 3. Spirochetes (spiral) Some bacteria are of variable shapes – pleomorphic Shape is determined by rigid cell wall. Arrangement is also important: Cocci in pairs (pneumococci) Cocci in chains (streptococci) Cocci in clusters (staphylococci) Salmonella Gram Negative rods, measuring 2-4 X 0.6 μm. Most serotypes are motile with peritrichous flagella.  Salmonella is facultative anaerobe, oxidase -ve, catalase +ve.  Non-lactose fermenting, urease -ve, citrate +ve, VogesProskauer (VP test) -ve, potassium cyanide test (KCN)sensitive.  Salmonella comprises above 2500 serotypes, Less than 100 serotypes account for most human infections. Atmospheric conditions/oxygen requirement for the growth of microorganisms 1. Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. 2. Obligate anaerobes are organism which can only live in environments which lack oxygen. 3. Facultative anaerobes can grow with or without oxygen because they can metabolise energy aerobically or anaerobically. 4. Microaerophiles require oxygen because they cannot ferment or respire anaerobically, but require environments containing lower levels of oxygen than are present in the atmosphere (i.e.