Question

I. Solve the next problem You are asked to identify the cause of infection from a serious skin wound of a 60-year-old sailor involved in a ship fire. 50% of the patient's body presents second and third degree burn injuries. You are provided with a cotton swab with the patient's skin suppuration, which technique would you use to isolate all the cultivable bacterium infecting the wounds of the patient? Which type of medium would you use for this purpose? give an example of that type of media. You found 7 different microorganism morphologies after your isolation technique. To complete your identification, you were provided with MSA, MCK, EMB media plates and a set of biochemical tests to help your identification. From the seven morphologies, a singular pale mucous colony calls your attention, it grows in MCK and EMB media only. Based on the plate results: • What is the Gram of microorganism? • Which color did the microorganism would look alike after the Gram technique? • Does the bacterium ferments lactose? You find the next results after running your biochemical tests. • Simmons citrate : The whole tube looks blue. What does this mean?

Answer 1

The open wound and the exposed skin due to burn are opportunities for the bacteria to colonise and cause infection. These bacteria can either be from contact with the contaminated surrounding or due to the opportunistic bacteria in our normal flora. The possible bacteria that can cause infections in burn are.,

Gram positive- Staphylococcus aureus, Methicillin-resistant S. aureus, Coagulase-negative Staphylococci ,Enterococcus spp., Vancomycin-resistant Enterococci and

Gram negative-  Pseudomonas aeruginosa, E scherichia coli, Klebsiella pneumoniae, Serratia marcescens, Enterobacter spp., Proteus spp., Acinetobacter spp., Bacteroides spp.(Burn Wound Infections, Church et al)

1. The swab collected from the burn sites can be inoculated by swabbing in suitable media, incuabted and then isolated into a single pure colony by streak plate for identification. Other than this biochemical tests are also performed to identify the bacteria according to the metabolism
2. Selective and differential media are used for identifying the bacteria into two broad classifications- Gram positive (Blood, Chocolate agar, etc ) and Gram negative bacteria (EMB, MacConkey, etc)
3. Bacteria that grows in MCK and EMB are Gram negative bacteria because they inhibit the growth of Gram positive bacteria.  

Based on plate results,

1, It is a Gram negative bacteria

2, Pale reddish colour will be shown after the Gram staining.

3, No, the isolated bacteria do not ferment lactose. Because lactose fermenting colonies look reddish or pinkish colony in Macconkey agar. Since the organsim shows pale colour- it do not ferment lactose

Based on biochemical,

1, Simmon s citrate- the change of green colour Simmon citrate media to prussian blue after incubation of the bacteria shows positive citrate test which means that the bacteria has used citrate as sole source of carbon.

2, TSI- complete red with no bubbles indicates negative result i.e., the organism do not ferment sugars. (acidic fermentation is not seen)

3, MRVP- No colour change indicates negative result for MR which means that the bacteria do not ferment glucose

4, SIM- Growth on the surface of the agar indicates that the bacteria is aerobic. No other colour change or preciptate formation shows that the bacteria do not ferment sugars or produce hydrogen sulphide gas.

S ear' 2016 DECEMBER 50th Week 342nd Day GLOBE ENERLASTINE PLYWOOD Wednesday Gram Staining Grom positive Gram negative bacteria Lactose fermentors Citrobacter, kool, Non-lactose formentors - TEdwardsiella, Proteus, IP aeroginosa) Morganella Glucose formentors Cedwardsiella) Non-Glucose fermentats. Proteus. P aeroginosa Citrate (Citrate positive) Variable t Tucoid colonies show these that biochemical characters the bacteria is aerogimosa seadomonas JAN 2017 S M T W T F S 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 erb we would like to be known as logical beings, but most of our decisions are emotional.

the identified organism is found to be Pseudomonas aeroginosa. It is the most common infection seen in burns and wound. The results of cultural charcteristics and biochemical tests shows that it is Pseudomonas aeroginosa