Question

Describe the below diseases, bacteria associated and associated characteristics

-Psittacosis

-Pneumonia (Be sure to include the predominant etiological agent)

-Q fever

-Tuberculosis

-Whooping cough

If applicable, identify the causative agent(s) reservoir for pathogen (e.g. human, animal, environment) mode of transmission diagnostic indicators (e.g. Ghon complexes, spherules, fried-egg appearance on media, thick-walled cysts, etc…)

Answer 1

Pneumonia:

Pneumonia is caused by various etiological agents like bacteria, virus, mycoplasma and fungi etc. Of these bacterial pneumonia caused by Streptococcus pneumoniae is common type of infection. The causative agent is Streptococcus pneumoniae. The infection is transmitted by air droplets and the reservoir is human. The symptoms include the alveoli of the lungs are infected and filled with fluids and interfere with the oxygen uptake, cough and phlem. The condition is diagnosed by serological tests and culturing of bacteria from sputum and other fluids. The infection is treated by Penicillin, fluoroquinolones and the infection is prevented by pneumococcal vaccine.

Q fever:

Q fever is caused by Coxiella burnetii. The infection is mainly transmitted by unpasteurized milk. Several mammals act as reservoirs. Ticks act as vectors and the symptoms include fever and respiratory illness. Mild repiratory disease may last for 1 to 2 weeks and occasional complications like endocarditis may arise. The infection is diagnoised by growth of infectious agent in cell culture. The infection is treated by Doxycycline and chloroquine antibiotics.

Tuberculosis:

Tuberculosis is caused by obligate aerobic, acid fast bacillus called Mycobacterium tuberculosis. Several factors such as host resistance levels, presence of other illness, physiological and environmental factors, malnutrition and stress may lead to the infection. The infection is caused by inhaling the bacillus. The bacilli reach the lungs where the alveolar macrophages phagocytize them to destroy the bacilli. But the bacilli usually escape this action because of the mycolic acids that occur in the cell wall of the bacteria stimulate the inflammatory response in the host.

The infection is initiated by lesion in the lungs called tubercle. The lesions become calcified and show up Ghon’s complexes in the X-ray films. The tubercle breaks down releasing the virulent bacilli in to the lungs, cardiovascular and lymphatic systems. Coughing is the obvious system of lung infection. Sputum may contain blood because of the tissue damage result in fatal hemorrhaging. The disseminated infection is called miliary tuberculosis.

First effective antibiotic used was streptomycin and was introduced in 1944. The current treatment recommended by world health organization (WHO) requires minimum 6 months of antibiotic therapy including 3 to 4 drugs. Anti T.B drugs like isoniazid and rifampin are mostly administered. Other drugs include pyrazinamide, rifapentine and ethambutol. Diagnosis can be done by tuberculin skin test which is resulted due to sensitized T cells as response of humoral immunity develops in the skin. Other tests like Mantoux skin test and chest X-ray are C.T examination to detect lung lesions are carried out.

The BCG vaccine containing the live culture of M.bovis responsible for causing bovine tuberculosis has been made avirulent by long cultivation on artificial media. The BCG vaccine (bacillus of Calmette and Guerin) has been available since 1920 and was found to be effective and new vaccines are also developing to control the multidrug resistant strains.

Whooping cough:

Pertussis or whooping cough is the infection caused by an obligate aerobic, gram negative, cocco-bacillus called Bordetella pertussis. The virulent bacterial strain possesses a capsule that attaches to ciliated cells in the trachea and escapes the ciliary escalatory system. The bacteria produce many toxins of which the tracheal cytotoxin which is a cell wall fraction damages the ciliated cells and the pertussis toxin enters the blood stream to cause systemic infection. It is a childhood disease and in the initial stage called the catarrhal stage resembles the common cold. Severe coughing is observed in the paroxysmal stage or second stage.

Severe coughing in children may result in broken ribs and gasping for air between the coughs causes whooping sound. The coughing may occur several times in a day for 1 to 6 weeks. The convalescence stage may last for months. Immunization by DTP vaccine (diphtheria, tetanus and pertussis) in children has found to decrease the incidence of the infection. Treatment of pertussis is by using antibiotics like erythromycin and other macrolides before the onset of paroxysmal coughing stage is effective