Question

Microbiology Unkown Identification Lab

Gretchen is a 2-year-old toddler that was previously healthy but is now suffering from an intensely sore throat with inflammation and fever. She has not had any of the routine childhood vaccinations.

1. What kind of infection do you suspect for this patient and why do you have that hypothesis?

2. What sample do you want to take from your patient and have grown on nutrient agar?

Choose ONE of the following possible samples for culture results:

- Blood Culture

- Fecal Culture

- Mouth and Throat Swab Culture

- Penile Swab Culture

- Sinus swab and Sputum Culture

- Urine Culture

- Vaginal/Cervical Swab Culture

- Wound Swab and Culture

3. Which staining process are you requesting?

4. How will you interpret the results of this stain?

5. What Biochemical tests should you run and why? (What biochemical function are you testing for?; What will a positive reaction look like and what will a negative reaction look like? )

Answer 1

Answer 1) Sore throat is present so either ( Streptococcal pharyngitis ) or Diphtheriae can be the the infection the child is suffering from .Sore throat because of Streptococcal pharyngitis is most common in children less than 3 years presenting with fever ,sore throat and inflammation .Also Diphtheria is common in less than 4 years of age and the child is unimmunized for age so Diagnosis go in favour of Faucial Diphtheria caused by Corynebacterium Diphtheriae .

Answer 2)Throat swab one or two swabs taken from inflmmatory exudative part .

Answer 3) Gram and Albert stain

Answer 4)-->Diphtheriae appear as irregularly stained club-shaped gram-positive bacilli typically arranged in Chinese letter or cuneiform arrangement (V-or L-shaped). It is difficult to differentiate them from other commensal coryneforms found in the respiratory tract Albert's stain: It is more specific for C. diphtheriae, as they appear as green bacilli with bluish black metachromatic granules at the poles.

Answer 5)HISS SERUM sugar media: Diphtheria bacilli ferment glucose and maltose (by all biotypes) and starch (by only gravis biotype), with the production of acid but no gas. As it is fastidious, only enriched sugar media such as Hiss's serum sugar media can be used for testing sugar fermentation test

Pyrazinamidase test: This test is positive by most of the corynebacteria (possessing pyrizinamidase enzyme); however, the exotoxin producing human pathogenic corynebacteria such as, C. diphtheriae, C. ulcerans and C. pseudotuberculosis, give a negative test result as they do not produce this enzyme

Urease test: C. diphtheriae does not hydrolyze urea. This property differentiates it from C. ulcerans and C. pseudotuberculosis which are urease positive

Corynebacterium is catalase positive but oxidase negative and nonmotile.