Question

Date: Group: Name: Table 2. Bacteria isolated from the skin on the blood agar plate. Colony type-II Colony type-l Colony type-III Gram stai Colony morphology, margin, elevation, color, etc. Hemolysis Table 3, Bacteria isolated from the rectal area on the EMB plate. Colony type-I Colony type-III Colony type-II Gram stain Colony morphology, margin, elevation, color, etc. Colony arrangement 4. Review questions d. In summary, what is the major purpose of this experiment? What are four reasons for knowing which microorganisms are associated with different parts of the body? e When doing a throat culture, what specific area of the throat is swabbed, and why? f. g. When doing a skin culture, why is the swab first moistened with saline? h. Why is EMB agar used for rectal cultures? What are fastidious streptococci?

Answer 1

4. d. The major purpose of this experiment is to study the different microorganisms associated with different parts of the body and how these are collected and studied.

e. 1. To know which organisms are present normally in a particular part of the body, their significance, and why different parts have different microorganisms and what role do they play there.

2. To know if there is an infection in particular area of the body (seen by change in normal flora or an imbalance).

3. To get a greater insight into infections caused from injury to these sites. And the possible impact on the body due to absence, decrease, or increase in these microorganisms.

4. To study the different human-microbe interactions associated with different part.

f. For the collection of throat swabs, swab is gently rubbed over the tonsillar bed or area where there is exudate or a lesion. The tongue is avoided so that the sample does not get contaminated by contact with the oral mucosa.

g. When doing a skin culture from intact skin the swab is moistened using sterile saline because it helps in the transfer of bacteria from the skin to swab and can also increase the number of microorganisms that are collected from the site.

h. EMB Agar (Eosin Methylene Blue Agar) is a selective and differential medium for coliforms. It is used to isolate gram negative enteric bacteria from clinical and nonclinical specimens. It inhibits the growth of Gram-positive bacteria and allows us to distinguish between organisms that ferment lactose (e.g., E. coli) and those that do not (e.g., Salmonella, Shigella). Rectal cultures will show presence of Ecoli as the normal flora and in case the person is infected by any other gram negative bacteria they will also appear on the media.

i. A fastidious organism is the one that has a complex nutritional requirement and it will only grow when specific nutrients are provided in the growth medium.

Fastidious streptococci are gram-positive cocci that require the addition of blood or serum to culture media in order to grow. Because some streptococcal species are obligate pathogens and strictly infects humans they require blood to grow in vitro.