Question

Outbreak on a Cruise ship Your job is to think about the results and to use the information to make a recommendation to the Cruise line. How can they best get rid of the problem? Part I -Legionnaire's Disease 1) What causes Legionnaire's Disease? Briefly describe the lifestyle of the pathogen Involved in this disease. Why is it such a problem on cruise ships? (2 points) Part II - Sampling the Environment 2A) The Direct Fluorescent Antibody (DFA) Assay was used to find the pathogen In ship samples. Explain how this method works, as used to detect this pathogen. (2 points) 2B) Which of the WATER samples were positive for the pathogen? Which of the SWABBED samples were positive? Did the positive samples look different from the control? Why or why not? (2 pts) Part III - Your Experimental Results 3) You went into the lab to try your own set of experiments. Briefly describe the set up and the results you got (2 points) You may find it convenient to put your results in the chart below. The control has been completed for you Day CONTROL CHLORINE HEAT CHLORINE UV RADIATION OZONE OZONE CHLORINE Part IV - Your Conclusion 11 Besed on your result, Which one treatment do you recommend Your recommendation must include why you think that treatment is the best option IN THIS CASE, compared to the others. You must refer to the results and include background information from the references as needed. (2 points)

Answer 1

Cause of Legionnaires' disease

Legionnaires' disease is a severe form of lung inflammation or pneumonia usually caused by infection. It's caused by a bacterium known Legionella WHICH is a pathogenic group of Gram-negative bacteria that includes the species L. pneumophila

Lifestyle

Most of these bacteria are located in the extracellular space between intracellular infection cycles and display thus a dual intracellular/extracellular lifestyle. They have the ability to replicate within a large number of different host cells

Why in cruise ships?

Cruise ships are a hotbed of bacteria and potential illnesses. These organisms live within aerosolized water, and the infection spreads through inhaling or aspirating the contaminated water. In a cruise ship setting, this is particularly dangerous as they rely on potable water and boast multiple spa areas with hot tubs that create breeding grounds for Legionella.

Detection of the disease

DFA staining can detect legionella in respiratory secretions and tissue samples, in which fluorescein-labelled monoclonal or polyclonal antibodies directed against Legionella species are used. Commercial DFA tests contain fluorescently labelled antibodies that specifically target antigens present in the Legionella species. This technique has the advantage of providing results within 2-4 h but the sensitivities are dependent on the quality and specificity of the antibodies used.

Direct Fluorescent Antibodies Antigen Bacterial col Antibacterial antibody labeled with Fluorescent dye

Legionella Detection in water:

We can detect the bacterial presence by swabbing water sample with a sterile swab in a specific culture medium like BCYE agar. colonies will grow in a positive sample compared to the control plate.

a plate showing steak of Legionella colonies.

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EXPERIMENTAL SETUP

You can treat each water sample with chlorine, UV etc (as given in the table). after that, spread plate a specific dilution for colony counting.so that we can find whether the bacterial load have any difference or not.

EFFECTIVE TREATMENT

All the given treatments have the capability to decrease the legionella load in the water . The Legionella disinfection range of hot water is 158 – 176 °F. Chlorine and hot water can kill legionella, but not amoebae. both ozone and UV radiation are effective.

but if we give two treatments together, it will be more effective. so heat chlorination and ozone chlorination have more probability.

note: the exact result will depend on the experimental dose and time of exposure.