DR Medhat MRCP

Atypical bacteria
I. Mycobacterium TB
- It`s atypical , highly aerobic, acid fast bacilli
- It`s the main mycobacteria causing tuberculosis ( other types are M.bovis, M.Avium &
M.Kansisii).
• Mode of infection :
o Inhalation of TB bacilli (droplet infection pulmonary TB).
o Ingestion of milk infected with mycobacterium bovis (bovine TB).
• Pathology of TB :
- There are 2 main pattern of TB , 1ry TB & 2ndry TB.
1ry TB :
‣ Seen as an initial infection, usually in children.
‣ Characteristically asymptomatic
‣ Sub-pleural & hilar LN granulomas (Ghon`s complex)
‣ These granulomas totally resolves & no spread of infection
‣ Pleural effusion occure before PPD test is +ve
‏.سؤال ‣ PPD test is +ve 3 weeks-3 months after 1ry infection
2ndry TB :
‣ Seen mostly in adults as a reactivation of previous infection (or
reinfection).
‣ The granulomatous inflammation is much more florid,
caseating and widespread.
‣ Typically, the upper lung lobes are most affected, and
cavitation can occur.
‣ When resistance to infection is particularly poor, a "miliary"
pattern of spread can occur in which there are a myriad of
small millet seed (1-3 mm) sized granulomas, either in lung or
in other organs most commonly in young children:
1) CNS (TB meningitis , brain tuberculoma)
2) Cardiac ( TB pericarditis)
3) GIT ( ilio-caecal junction is the commonest site)
4) TB peritonitis
5) Genital (TB salpingitis ,prostatitis,epidydimitis)
6) Urinary TB.
7) TB lymphadenitis.
8) Bone (Pott`s disease)
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