This document provides information on the genera Mycobacterium and Actinomycetes. It describes the characteristics and laboratory diagnosis of key mycobacterial species like M. tuberculosis and M. leprae which cause tuberculosis and leprosy, respectively. It outlines the stages of primary tuberculosis and differences between primary and post-primary disease. It also discusses Actinomyces israelii and Nocardia asteroides, including their morphology, diseases caused, and treatment.
5. CULTURE CHARACTERISTICS
On primary isolation:
– visible growth after up to 8 weeks
Colonies:
– Buff colour, dry bread crumb-like appearance
– Growth is eugonic (M. bovis = dysgonic)
Growth temperature:
– 35-37oC
Obligate aerobe
-------------------------------------------------------------------------- Heat-sensitive
Susceptible to alcohol, glutaraldehyde and
formaldehyde.
6. Some differential characteristics of
tuberculle bacilli causing human disease
____________________________________________________
Species
Atmospheric
preference Nitratase TCH Pyrazinamide
--------------------------------------------------------------------------------------M. tuberculosis Aerobic
+
S
S
M. bovis
Microaerophilic
--
R
R
_______________________________________
TCH = thiophen-2-carboxylic acid hydrazide
S = sensitive, R = resistant
7. THE DISEASE
Not highly contagious:
– transmission with prolonged contact
between susceptible and active case
– usually transmitted by airborne droplets,
must penetrate deep into respiratory tree
– infection can be via other routes:
ingestion
=> infection through cervical
or mesenteric LN
8. Virulence
– Ability to Survive within Macrophages
Primary Tuberculosis
Post-Primary Tuberculosis
9. Stages of Primary Tuberculosis in Childhood
--------------------------------------------------------------------------------------Stage
Time (from onset)
Characteristics
--------------------------------------------------------------------------------------1.
3-8 weeks
Primary complex (PC)
develops and tuberculin
conversion occurs
2.
2-6 months
Progressive healing of PC,
possibility of pleural effusion
3
6-12 months
Possibility of miliary or
meningeal tuberculosis
4
1-3 years
Possibility of bone or joint
tuberculosis
5
3-5 years
Possibilty of genito-urinary or
chronic skin tuberculosis
10. Main differences between primary and post-primary
tuberculosis in the non-immunocompromised patients
--------------------------------------------------------------------------------Characteristics
Primary
Post-primary
--------------------------------------------------------------------------------Local lesion
Small
Large
Lymphatic involvement Yes
Minimal
Cavity formation
Rare
Frequent
Tuberculin reactivity
Negative (initially) Positive
Infectivity
Uncommon
Usual
(pulmonary cases)
Site
Any part of lung Apical region
Local spread
Uncommon
Frequent
---------------------------------------------------------------------------------------
11. TUBERCULIN TEST
Tuberculin: a heat-concentrated filtrate of a
broth in which tubercle bacilli had been grown.
Injection of tuberculin into the skin >>
– Large, indurated reactions >>Post-Primary
Tuberculosis.
– No induration >> Protective immunity
Purified Protein Derivatives (PPD):
– Mantoux Method (Intracutaneous)
– Heaf Method (Spring-loaded gun)
– Tine Tests (Disposable single tests)
20. TREATMENT
Chemotherapy Recommended by International Union against
Tuberculosis and Lung Disease (examples)
--------------------------------------------------------------------------------------------------------Intial phase
Continuation
Regimen
(2 months)
phase (4 months)
Drug
Drug
--------------------------------------------------------------------------------------------------------HRZ
HR
Standard
HRZ
H3R3
Intermittent/ when
HRZ
H2R2
supervision is indicated
HRZE
HR
When there is a high
HRZS
HR
incidence of initial drug
resistance
---------------------------------------------------------------------------------------------------------
21. EPIDEMIOLOGY
Transmission:
– Open Pulmonary Tuberculosis
– Crowdness in homes and workplaces
Tuberculosis and AIDS
Tuberculosis in Developing Countries:
– Africa
22. CONTROL
Early Detection and Treatment of Open
Cases
Reducing Overcrowding
Vaccination:
– Bacille Calmette-Guerin (BCG)
– Not effective as control measure
23. Mycobacterium leprae
Leprosy (Hansen's disease)
– A chronic intracellular infectious disease
unique to man (with few exceptions).
Usually not fatal.
Never been cultivated in vitro
Armadillos:
– 1010 bacilli/gram of diseased tissue
25. M. leprae can be grown in mouse foot pads
or the nine-banded armadillo (picture).
26. PATHOGENESIS
Schwan cell >> Nerve damage >>
Anaesthesia and Muscle paralysis >>
Gradual destruction of extremities
> Nasal bones and eyes
Immune reactions >>
– Severe and permanent nerve damage
27. THE DISEASE
Manifestations of the disease depend on the
resistance of the host.
1. Tuberculoid: host is highly resistant,
clinical abnormalities limited to a few
peripheral nerves and adjacent skin areas,
tuberculoid granuloma
2. Lepromatous: host lacks resistance, all
tissues affected, foam cell granuloma
3. Borderline:
28. The feet become subject to bone damage and
deformity through unnoticed wounds and infection.
Serious infections can lead to amputations.
29. Victims of leprosy often suffer amputations of
fingertips and toes due to unfelt trauma.
X-rays of different stages.
30. Leprosy affects facial nerves > loss of blinking
reflex of the eye > dryness, ulceration, and
blindness.
40. Actinomycosis-organisms aspirated from the lung. Long,
tortuous and branching organisms can easily be visualized
using silver stain. Sulfur granules not seen in aspirations.
41. LABORATORY DIAGNOSIS
i. Direct Examination:
Sputum, Pus, etc.. >> Examined
for Granules
ii. Culture: Brain Heart Infusion Agar
TREATMENT
– Penicillin >> Several Weeks
42. Sulfur granule from human actinomycosis tissue
section (hematoxylin and eosin stain).
43. 2. NOCARDIA SPECIES
N. asteroides
– Nocardiosis.
Aerobic.
Disease Begins as Pulmonary Infection >
> 50% of Patients are Immunocompromised.
Fatality Rate >>
44. LABORATORY DIAGNOSIS
i. Direct Examination:
Sputum, Skin Lesions, Tissue Biopsies or Surgical Material
>> Microscopically.
Observe: G+ve, Multiple Branched and Beaded Filaments.
> Partially Acid-Fast.
ii. Culture:
iii. Identification: Biochemically.
TREATMENT
Sulphonamides, NA, TMP-SMX.
47. Differences between the genera
Actinomyces and Nocardia
-----------------------------------------------------------------Actinomyces species
Nocardia species
-----------------------------------------------------------------Facultative anaerobes
Grow at 35-37oC
Oral commensals
Non-acid-fast mycelia
Endogenous cause of
Disease
Strict aerobes
Wide temp range of growth
Environmental saprophytes
Usually weakly acid-fast
Exogenous cause of disease
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