Laboratory Portfolio Questions for A11IND 2019-2020

These questions form the basis of your A11IND coursework, the laboratory portfolio. You will need to provide data from your recent practical classes as well as answer specific questions designed to assess your application of knowledge. Please provide answers to all questions in ONE word document for submission. Materials and Methods etc. are not needed.

It is expected that you use your own images taken from the practical sessions. Any information (including figures and diagrams) that you use in your answers, that are not from your own data, need to be appropriately referenced or acknowledged.  All coursework should also be submitted through Turnitin before the submission deadline as indicated on Moodle.  This coursework contributes 40% of the final module mark.

 

Microscopy:

  1. Describe the morphological features of bacteria stained by Gram staining technique with respect to their shapes and colours.  Explain the principles underlying this method when used in bacteria identification.  (4 marks)

 

 

  1. Some bacteria cannot be stained or will not show adequate staining intensity using the Gram stain method.  Give two examples and for each example, explain the reason(s) why Gram stain fails to give good results (6 marks)

 

 

  1. A sputum sample from a patient with tuberculosis has been sent to the pathology laboratory for testing. Describe the procedure to be used for visualising the pathogen responsible for tuberculosis in this sample (4 marks)

 

 

Pathogen identification:

  1. Case scenario

A 32 year old male who has recently been to an Asian country develops projectile vomiting and profuse diarrhoea.  A stool sample has been received by the pathology department and the initial investigation on the sample has produced the following results:

 

 

Sample ID: S3

 

Culture:

Small colourless (transparent) colonies on McConkey agar

 

Heavy growth of yellow colonies on TCBS (Thioglycolate Citrate Bile Salt) agar

 

Gram stain results

S3 Yellow colony:  Gram negative curved rods

Gram positive control: Gram positive cocci present

Gram negative control: Gram negative bacillus present

 

Special staining for flagella:

S3 Yellow colony: Flagella present

Positive control: Flagella present

Negative control: Flagella not found

 

Motility test:

S3 yellow colonies: darting motility observed

Positive control: motile

Negative control: non-motile

 

Oxidase test:

S3 Yellow colony: Oxidase positive

Oxidase positive control: Oxidase positive

Oxidase negative control: Oxidase negative

 

Glucose test:

S3 Yellow colony: Glucose positive

Glucose positive control: Glucose positive

Glucose negative control: Glucose negative

 

 

  1. Based on the information provided from the initial laboratory investigation, demonstrate the elucidation of the possible identity of the yellow colonies on the TCBS agar with stepwise explanation and list the resources used in the process of identification (5 marks)

 

 

 

  1. Describe the difficulties in identifying the pathogen based on the initial laboratory findings and how to improve the identification process (4 marks)

 

 

  1. Explain how the experimental processes were validated during the initial laboratory investigation of S3 (6 marks)

 

 

  1. Explain how bacteria like S3 exerts its pathological effects on human gastrointestinal tract. A diagram may be used to support your answer (5 marks)

 

Latex agglutination:

 

  1. What would be the benefit of using IgM for agglutination reactions performed in vitro? (3 marks)  When considering the serological status of a patient, if you detect the presence of IgM antibodies to an antigen, what might that indicate? (1 mark)

 

 

  1. Explain the steps involved in the genetic testing of a micro-organism that would be performed to confirm its identity (4 marks)

 

Antimicrobial action:

  1. Use the class data set provided on Moodle and indicate whether the organisms tested are considered susceptible or resistant to the antimicrobials which they had been tested against. Refer to sensitivity testing tables 1 & 2 when you perform this task. (6 marks)

 

 

S1      
 

Antibiotic tested

 Inhibition zone diameter class median (mm)

 

And

 

 

Acceptable range (mm)

 Result interpretation

S = sensitive

R = Resistant

 Comments

 

 
 

Ampicillin

 

  

 

 

  

 

  
 

Chloramphenicol

 

  

 

 

  

 

  
 

Tetracycline

 

  

 

 

  

 

 

  
 

Sulphafurazole

 

  

NA

 

  

NA

  

NA
 

Streptomycin

 

  

NA

 

  

NA

  

NA
 

Penicillin

 

  

 

  

 

 

  
 

Cefoxitin

 

  

 

  

 

 

  
 

 

Erythromycin

 

  

 

  

 

 

  

 

 

 

S2      
 

Antibiotic tested

 Inhibition zone diameter class median (mm)

 

And

 

 

Acceptable range (mm)

 

 Result interpretation

S = sensitive

R = Resistant

 Comments
 

Ampicillin

 

  

 

  

 

 

  
 

Chloramphenicol

 

  

 

  

 

 

  
 

Tetracycline

 

  

NA

 

  

NA

  

NA
 

Sulphafurazole

 

  

NA

 

  

NA

  

NA
 

Streptomycin

 

  

 

  

 

 

  
 

Penicillin

 

  

NA

 

  

NA

  

NA
 

Cefoxitin

 

  

 

  

 

 

  
 

Erythromycin

 

  

NA

 

  

NA

  

NA

 

 

  1. Describe Penicillin’s mode of action with the aid of a diagram with emphasis on how it interferes with bacterial cell wall integrity (4 marks).

 

 

 

  1. Explain why some organisms such as E coli are generally resistant to penicillin (2 marks).

 

 

  1. When a bacterial strain such as S1 is resistant to amoxicillin, what is the possible mode of action of the gain in resistance by the bacteria (3 marks)? Are there options which can be considered to replace amoxicillin for an effective treatment to cure the infection (3 marks)?

 

 

Total marks = 60