TYPES OF CULTURE MEDIA-II

Giardiasis [Ref. Harrison 16^1h/e p 1520]

• Pulmonary diseases associated with tissue or blood eosinophilia are a heterogenous group of disorders.
• They are classified as :

Loeffler’s syndrome

• It is a benign acute eosinophilic pneumonia of unknown cause characterized by migrating pulmonary infiltrates and minimal clinical manifestations.
• These are usually secondary to parasites or drugs.
• Loeffler’s syndrome reflects a hypersensitive response to an ingested or inhaled antigen from food, medication or an infectious agent. Causes of Loeffler’s syndrome

Parasitic infections

• Ascaris
• Schistosomiasis
• Strongyloides
• Ancyclostomiasis
• Trichomoniasis
• Clonorchiasis
• Visceral larva migrans
• Tapeworm
• Paragonimiasis

Ans. D: LJ medium

Diagnosis of tuberculosis

Microscopy

– Rapid diagnosis

– Low sensitivity. Concentration may increase sensitivity up to hundred folds

– Can not differentiate tuberculosis and non-tuberculosis mycobacteria

– False positive results

– Samples must always be studied with one positive and one negative control

Culture

– The gold standard method for tb diagnosis

Culture in LJ media takes 3 to 6 weeks

– Commonly used rapid culture systems have disadvantages:

1. Radioactive, expensive, blood containing samples give false results
2. All culture methods require decontamination

When grown on LJ medium, M. tuberculosis appears as brown, granular colonies (sometimes called “buff, rough and tough”). The media must be incubated for a significant length of time, usually four weeks, due to the slow doubling time of M. tuberculosis compared with other bacteria (15-20 hours).

Lowenstein-Jensen (g) medium is most widely used for tuberculosis culture.

LJ medium containing glycerol favours the growth of M. tuberculosis while LJ medium without glycerol but containing pyruvate encourages the growth of M. bovis. Both should be used in countries or regions where patients may be infected with either organism.

Ingredients

Mineral salt solution

Potassium dihydrogen phosphate anhydrous (1(1-12PO4) 2.4g Magnesium sulphate (MgSO4. 7H20) 0.24g

Magnesium citrate 0.6g

Asparagine 3.6g

Glycerol (reagent grade) 12m1

Distilled water 600m1

Ans. is ‘b’ i.e., Inhibits growth of other bacteria

Lowenstein-Jensen Medium (LJ medium)

LJ medium consists of mineral salts, asparagine, glycerol, malachite green and hen’s egg.

The malachite green prevents the growth of other microorganisms on medium.

It is used as a primary isolation medium for mycobacteria.

Ans. is. ‘a’ i. e., LJ medium

Ans: d. Muller-Hinton…

• Thayer-Martin is a useful selective media for Neisseria gonorrhoeae”.
• Mueller-Hinton is an enriched media for Neisseria.
• C diphtheriae and other corynebacterial grow aerobically on most ordinary laboratory media. On Loeffler’s serum medium, corynebacterial grows much more readily than other respiratory organisms, and the morphology of organisms is typical in smears.
• Lowenstein-Jensen Medium. It is used to culture tubercle bacilli. It contains egg, malachite green and glycerol.
• Chocolate Agar or Heated Blood agar: Prepared by heating blood agar. It is used for culture of pneumococcus, gonococcus, meningococcus and Haemophilus. Heating the blood inactivates inhibitors of growth.