Lecture 11

Question 1

Two organisms of mycobacterium

Answer 1

myco. tuberculosis, myco leprae

Question 2

What does myco tuberculosis cause

Answer 2

Tuberculosis disease- world wide distribution

Question 3

Describe the growth of mycobacterium tuberculosis

Answer 3

grows slowly- doubling time is 18 hours

culture growth occurs after 6-8 weeks in lowenstein jenson medium

Question 4

Transmission route of myco tuberculosis

Answer 4

respiratory aerosol- human is the reservoir, no animal source. Organism resist drying and desiccation - common in low socioeconomic groups

Question 5

Pathogenesis of myco tuberculosis

Answer 5

do not produce any exo or endotoxins. Organism survive and multiply in the phagocytic cells

Question 6

2 types of histological inflammatory responses to myco tuberculosis

Answer 6

1. exudative lesion- acute inflammatory response at the initial site of infection
2. granulomatous lesion- central area of giant cells containing bacilli surrounded by epithelial cells

Question 7

result of first time infection in childhood of TB

Answer 7

lesion in lung just beneath pleura in lower lobe- it heals

Question 8

result of reactivation of TB disease later in life

Answer 8

produce lesions in apex of lung- destructive resulting in cavity formation

Question 9

Ways lesions can spread within the body

Answer 9

tubercle eroding a bronchi- emptying material and spilling to other lobes/GIT
Dissemination via blod stream to other organs

Question 10

What is resistance to TB organism mediated through?

Answer 10

through cell mediated immunity - Tcells and macrophages limit lesion so it heals faster

Question 11

Tuberculin test (Mantoux Test)

Answer 11

way prior infection of TB is diagnosed

Question 12

Are there antibodies for TB?

Answer 12

NO

Question 13

Are most TB findings symptomatic or asymptomatic?

Answer 13

asymptomatic (90%)

Question 14

What is the major manifestation of TB?

Answer 14

pulmonary tuberculosis- cough, fever, night sweats, fatigue, loss of appetite, loss of weight

Question 15

Where will a more serious pulmonary tuberculosis cause?

Answer 15

spread of infection to cervical lymph nodes causing cervical lymphadenitis (scrofula)

Question 16

Miliary tuberculosis

Answer 16

resemble millet seeds- multiple disseminated lesions either in lung itself or in organs like the kidney, spleen, liver

Question 17

TB osteomyelitis

Answer 17

occurs in any bone- involvement of vertebral body known as Potts’ disease

Question 18

Erythema nodosum

Answer 18

tender nodules on extensor aspect of tibia and ulna

Question 19

Lab diagnosis of caseation necrosis

Answer 19

isolation of AFB, staining of sputum for fast screening by fluorescent microscope, culture takes 6 weeks to develop on medium

Question 20

Liquid BACTEC medium for TB

Answer 20

radioactive metabolites are present- growth can be detected by radioactive CO2

Question 21

Biochemical test for TB

Answer 21

Niacin is produced by TB- others do not

Question 22

QuantiFERON gold test for TB

Answer 22

recent test approved in US not yet well studied- based on gamma interferon estimation

Question 23

Clinical investigations for TB

Answer 23

chest Xray, PPD skin test, blood test- ESR and WBC count

Question 24

Treatment for someone with TB

Answer 24

multidrug therapy only- INH, Rifampicin, pyrazinamide, ecthambutal- single drug therapy is not recommended
6 months get 3 drug therapy recommended

Question 25

Prevention of TB

Answer 25

vaccination, - should not be given to AIDS patients
early detection helps to not spread disease
PPD skin test is screening test

Question 26

Describe the growth of mycobacterium leprae

Answer 26

slow growing organism- doubling time 14 days

causes leprosy- humans are the natural host

Question 27

Route of infection of myco leprae

Answer 27

prolonged contact, nasal secretions- mostly imported from immigrants

Question 28

Pathogenesis of myco leprae

Answer 28

affects skin, mucous membrane and nerves- replicate intracellularly in histiocytes

Question 29

Symptoms of myco leprae

Answer 29

incubation period is serval years!- lepromatous type shows multiple nodules over skin, skin anesthesia, resorption of bones, depressed nose
in tuberculoid type see anesthetic, hypo pigmented patch, thickening of ulnar nerve

Question 30

Lab diagnosis of myco leprae

Answer 30

bacillus seen by acid fast technique from skin scrappings or nasal discharge

Question 31

Treatment of myco leprae

Answer 31

Dapsone and rifampicin for 2 years

Question 32

What is mycoplasma

Answer 32

smallest organism -only one sero type

causes atypical pneumonia- pathogenic only to humans

Question 33

How is mycoplasma spread

Answer 33

only pathogenic to humans- spread through respiratory droplets

Question 34

Does mycoplasma have a cell wall?

Answer 34

NO- hence antibiotics acting on cell wall will not be effective

Question 35

Symptoms of mycoplasma

Answer 35

causes pneumonia- cough, core throat, ear ache, self limiting is 10-14 days

Question 36

Treatment of mycoplasm

Answer 36

Erythromycin, TC/Doxy

Question 37

Define actinomycosis

Answer 37

G + rods forming long filaments, found as normal flora in oral cavity - human infection is rare- common in cattle

Question 38

How do humans get actinomycosis infection?

Answer 38

trauma causes infection- hard non tender swelling in face and neck opens and forms sinus track discharging yellow pus- caused by IUD in women

Question 39

Treatment of actinomycosis

Answer 39

prolonged penicillin