Pseudomonas aeruginosa is a Gram negative, aerobic, rod shaped bacterium with unipolar motility (Ryan et al., 2004). It is a common bacterium which can cause disease in human and animals, mostly found in soil, water, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also with little oxygen, and has thus colonized in many natural and artificial environments. Because it thrives on moist surfaces, this bacterium is also found on and in medical equipment’s including catheters, causing cross infections in hospitals and clinics. P. aeruginosa is a slender Gram negative bacillus, 1.53Hm x 0.5Hm, actively motile by a polar flagellum. Clinical isolates are often piliated. It is non-capsulated but many strains have a mucoid slime layer. A mucoid strains, particularly isolates from cystic fibrosis patients have an abundance of extracellular polysaccharides composed of alginate polymers. This forms a loose capsule in which micro colonies of the bacillus are enmeshed and protected from host defences (Ananthanarayan et al., 2000).
The Enterobacteriaceae are a large, heterogeneous group of gram-negative rods whose natural habitat is the intestinal tract of humans and animals. The family includes many genera ( Escherichia, Shigella, Salmonella, Enterobacter, Klebsiella, Serratia, Proteus, and others). Some enteric organisms, such as Escherichia coli, are part of the normal microbiota. (Funke et al., 2009). E.coli bacteria may give rise to infection in wound, urinary tract, and abnormal cavity. This organism may cause septicemia and hemorrhagic diarrhea.( Madigan et al., 2006). An E. coli infection may also rise due to environmental exposure. Infection with this type of bacteria pose a serious threat to public health with outbreak rising from food and water that has been conterminated with human or animal feces sewage. This type of bacteria has been used as a biological indicator for safety of drinking water since the 1860s.
2.2. MORPHOLOGY AND IDENTIFICATION OF PSEUDOMONAS AEROGENOSA
AND ESCHERICHIA COLI
Pseudomonas aerogenosa is a motile organism (polar flagella) and is rod in shaped, is about (0.6 × 2 ?m)in length . It is gram negative and occurs as single bacteria, in pairs, and occasionally in short chains. The best known are pyocyanin (blue-green), pyoverdine (yellow-green, flourenscent). It is commonly found free living in moist environments and is also pathogen of plants, animals, and humans.
Pseudomonas aerugenosa is often preliminarily identified by its typical odor in vitro. The smell is described as grape-like, tortilla-like. It is not an active fermenter of carbonhydrate and produces acid, but no gas, in glucose and is lactose-negative. The oxidase and catalase test for P. aerugenosa are positive. (Wikipedia).
The multiply slowly in anaerobic environment if nitrate is present as a hydrogen acceptor. It is able to grow at 42?. The combination of pyocyanin production and the ability to grow at 42? is sufficient to distinguish P.aerogenosa from other Pseudomonas spp. e.g., P.fluorenscens, P.putida, P.stutzeri, P.putrefaciens), certain strains of P.aerugenosa may not produce pyocyanin (Wikipedia).
Escherichia coli and most of the other enteric bacteria form circular, convex, smooth colonies with distinct edges. Enterobactercolonies are similar but somewhat more mucoid. Klebsiellacolonies are large and very mucoid and tend to coalesce with prolonged incubation. Th e salmonellae and shigellae produce colonies similar to E. coli but do not ferment lactose. Some strains of E coli produce hemolysis on blood agar.
Escherichia—E coli typically produces positive test results for indole, lysine decarboxylase, and mannitol fermentation and produces gas from glucose. An isolate from urine can be quickly identified as E coli by its hemolysis on blood agar, typical colonial morphology with an iridescent “sheen” on differential media such as EMB agar, and a positive spot indole test result. More than 90% of E coli isolates are positive for ?-glucuronidase using the substrate 4-methylumbelliferyl-?-glucuronide (MUG). Isolates from anatomic sites other than urine, with characteristic properties (above plus negative oxidase test results) often can be confirmed as E coli with a positive MUG test result.