Question

These questions can be approached from a number of angles, and in many cases, there is no single correct answer. All questions are of equal value. Question

One How are bacterial endospores different from the cysts of protozoa? How are they alike?

Question Two Discuss some of the ways in which bacteriophages might be used to treat bacterial diseases? What might be some disadvantages?

Question Three Give some suggestions for treating anaerobic infections by manipulating the gas content.

Question Four Some human pathogenic bacteria are resistant to most antibiotics. How would you prove that a particular bacterium is resistant to antibiotics using laboratory culture techniques?

Answer 1

■ The production of cysts is an integral part of the life cycle of many free-living parasitic protozoa, allows these organisms to survive adverse environmental conditions.

Cysts are typically resting, dormant or resistant stages in the full life cycle of many protozoan species.

Protozoans at cyst stage will form a coating outside of the cell. This outer coating is protective and allows parasites to survive harsh conditions outside of a host, usually in the environment.


Bacterial spores are highly resistant, dormant structures formed in response to adverse environmental conditions.

They help in the survival of the organisms during adverse environmental condition such as heating, drying, temperature, and radiation.

endospore survives until a variety of environmental stimuli trigger germination, allowing outgrowth of a single vegetative cell.

On comparing cyst in protozoa and endodpore in bacteria,both structures are protective in nature. Both helps the organisms to persist in an unfavorable environment.They are dormant resistant structures.

There are also differences between the two structures.

Endospores are only produced by bacteria (only gram-positive bacilli), whereas cysts are only produced by some protozoa parasites.

Endospore is an internal structure whereas cysts form an outside wall around the cell for protection.

■.Bacteriophages are the viruses that infect bacterias.virus infects the bacteria by injecting its genes DNA or RNA. The phage virus copies itself inside the the bacteria cell resulting in the rupture or lysis of the cell.

Phages are harmless to animals,birds and plants.They are often called natural antibiotics.So that they can be used in treatment of the infections caused by bacterias.This is commonly known as phage therapy.

Bacteriophages can only multiply and grow inside a bacterium. Once all the bacteria are lysed they’ll stop multiplying.

¤.Advantages:

•Phages work against both treatable and antibiotic-resistant bacteria.
•They can be used with other drugs.
•Slightly destroys the normal flora of microbes in host
•Phages are natural and easy to find and
non toxic to animals, plants, and the environment.

¤.Disadvantage:

•specificity,since phages are specific for each bacterias phage will kill a bacterium only if it matches the specific strain
•Difficulty of finding an effective phage for a particular infection.
•Long term treatment is not possible
bacteria may develop phage resistance in future.
•May trigger immune system

■.Anaerobic bacteria are germs that can survive and grow where there is no oxygen.It can thrive in human tissue that is injured and does not have oxygen-rich blood flowing to it. Infections like tetanus and gangrene are caused by anaerobic bacteria. Anaerobic infections typically cause abscesses, and death of tissue. Many anaerobic bacteria produce enzymes that destroy tissue.

Many antibiotics are available to treat anearobic infection.To treat infection the best away is to introduce or to elevate the concentration of oxygen in the affected area since the organisms cannot survive under the presence of oxygen.

If the tissues are built with pus,pus drainage is the best way to get more aeration.

■.There are many laboratory techniques to demonstrate the antibiotic resistance of bacterias.Two of them are mentioned below.

•Agar dilution method

Agar dilution method follows the principle of establishing the lowest concentration of the serially diluted antibiotic concentration at which bacterial growth is still inhibited. On this agar plate, a bacterial isolate is tested for resistance to each of twelve different antibiotics. The clear zones around each disc are the zones of inhibition that indicate the extent of the test organism’s inability to survive in the presence of the test antibiotic.

•Disc diffusion method

This is the most commonly used technique

A growth medium, usually Mueller-Hinton agar plate with the isolate of interest that has been diluted at a standard concentratio. Commercially prepared disks, each of which are pre-impregnated with a standard concentration of a particular antibiotic, are then evenly dispensed and lightly pressed onto the agar surface. After an overnight incubation, the bacterial growth around each disc is observed. If the test isolate is susceptible to a particular antibiotic, a clear area of “no growth” will be observed around that particular disk.