Bacteria_Identification

Student’s Name: Course: Institution: Pseudomonas aeruginosa is a gram negative, rod shaped, non spore forming, aerobic bacteria which belongs to the family pseudomonadaceae, genus Pseudomonas and species aeruginosa. It has polar flagella used in locomotion. The major distinguishing characteristic is the ability to produce fluorescent pigments known as pyoverdine (blue green) and pyocyanin (yellow green). The ability to produce these pigments plays a great role in identification, understanding metabolic activities, genetic characteristics and growth requirements. Pseudomonas aeruginosa inhabits soil, water plants and animals (including humans) (Balcht et al 83-84). This bacterium only causes diseases in immunocomprised individuals and rarely in healthy persons hence referred to as an opportunistic pathogen. In most cases patients who have been admitted for more than week develops infections related to Pseudomonas aeruginosa. Such Infections which arise from a hospital set up are referred to as nosocomial infections (Cowan and Steele 16). The mixture of the unknown specimen was plated on the TSA media and incubated at 37oc for 24 hours. This produced distinct colonies. Gram staining was done to know the unknown was gram positive or gram negative. A portion of the colony was picked and smeared on a slide. The slide was stained with crystal violet as the primary stain and then washed in distilled water slowly. The smear was then treated with a few drops of iodine solution which acts as a mordant. Once more the slide was with distilled water and then decolorized with acetone (alcohol) (Leboffe and Pierce 11). The smear was then stained with a counter stain and in this case it was safranin. Finally it was washed with distilled water, blot dried and mounted on a microscope for observation. The results were a mixture of purple cocci and purple rod shaped bacteria. This means both the gram negative and gram positive bacteria were present. Smears were then made on the TSA media to obtain a pure culture. This resulted to well isolated and clear colonies. To differentiate them further, KOH test was performed. A few drops of 3 % KOH were placed on the glass slide containing the unknown. There was formation of sticky or mucoid substance on the slide indicating presence of gram negative bacteria (Cowan and Steele 13). EMB media was used to select only the gram negative bacteria by inhibiting gram positive bacteria. Distinct colonies were observed indicating presence of gram negative bacteria. To known the specific gram negative, oxidase test was performed. This was denoted as unknown 25 B. The unknown 25 B was transferred into the oxidase disk using an inoculating wire loop. After 20-30 secs the color of the disk changed from dark blue to pink (Ryan and Ray 60). This showed presence of Pseudomonas aeruginosa since it is oxidase positive. References Balcht, Johannes. Pseudomonas Aeruginosa: Infections and Treatment. Informa Health Care. New York: Cambridge University Press, 1994. Print. Cowan, S and Steele. Manual for the identification of medical bacteria. New York: Cambridge University Press, 1965. Print. Hugh, A. and Leifson. The taxonomic significance of fermentative versus oxidative metabolism of carbohydrates by various gram-negative rods. Journal of Bacteriology 66.8 (1953): 24–26. Print. Leboffe, and Pierce. Microbiology laboratory theory and application. Englewood: Morton Publishing Company, 2006. Print. Ryan, and Ray. Sherris Medical Microbiology. USA: McGraw Hill, 2004. Print.