microbiology revision notes

1. Mycobacteria

2. Atypical mycobacteria

3. Atypical mycobacteria
• Nontuberculous mycobacteria (NTM)
• occur as saprophytes of soil and water
• No person to person transmission
• Usually acquired in presence of immunodeficiency

4. Runyons classification

7. Photochromogens
• M. kansasii
• Pulmonary disease
• Mycobacterium marinum,
• Swimming pool granuloma
• Fish tank granuloma
• development of superficial granulomatous lesions in the skin
• Mycobacterium simiae

8. Scotochromogens
• Mycobacterium scrofulaceum,
• lymphadenopathy
• Mycobacterium gordonae, and
• Mycobacterium szulga

9. Nonphotochromogens
• These include
• M. avium complex (MAC)
• MAC includes mycobacterium intracellulare (battey bacillus)& mycobacterium avium
• Highly resistant to ATT
• Lymphadenopathy
• Mycobacterium xenopi, and
• Mycobacterium ulcerans

10. Rapid Growers
• Among this group itself involve
• photochromogens,
• M phlei M smegmatis
• scotochromogens, or
• nonphotochromogens species
• M fortuitum
• M chelonie
Post
trauma/injection
abscess

11. M ulcerans
•  burulis disease
• Only mycobacteria producing toxin

12. • Saprophytic mycobacteria are non pathogenic
• M phlei
• M smegmatis
• M gordonae
• M paratuberculosis

13. Pulmonary disease
• MAC is the commonest cause of pulmonary disease d/t non
tuberculous mycobacteria in developed countries
• M kansasii produces pulmonary ds indistinguishable from TB

14. Fish tank granuloma
• M marinum

15. Disseminated ds
• In AIDS related
• Caused by MAC

16. Mycobacterium leprae
Mycobacterium leprae

17. Mycobacterium leprae
• Acid fast (5 % H2SO4)
• Less acid fast than M tuberculosis (20 % H2S04)

18. M leprae
• Less acid fast than M tuberculae (hence 5 % H2SO4 or 1% HCl is used)
• First bacillus to be associated with human disease
• Modified fite stain
• In tissue sections

20. • Phenolic glycolipoprotein 1 plays
important role in pathogenesis
• LAM B1 external to cell wall in
serodiagnosis

21. • Lepra bacilli has affinity for RE cells & schwann cells
• Prefer cooler areas of body
• Skin / peripheral N / anterior chamber of eye /URT/ testis
• sparing warmer areas
• Axila groin scalp midline of back

22. • Schwaan cells are first cell to be involved in leprosy

23. • Virchows cells are
undifferentiated macrophages
• Abundant in lepromatous
leprosy

25. • Obligate intracellular bacillus
• Can remain viable 1- 7 days
• propagation is limited to
• Armadillo
• Also used for production of lepromin A
• mouse foot pad
• Sensitivity of antileprotic drug
• nude mice
• Generation time 12-13 days

26. Cardinal signs of leprosy
• Hypopigmented or erythematous skin lesions with definite loss of
sensation
• Involvement of peripheral nerves  definite thickening
• Skin smear  AFB

27. • Highly infectious with low pathogenicity
• Attack rate among house hold contacts is 4.4 -12 %
• Clinical infection Source of infection
• Active leprosy
• Multibacillary >>sub
• Portal of entry  skin and respiratory tract
• Chief mode of exit  nasal mucosa of untreated LL patients
• Modes of transmiision
• Droplets >>contact>breast milk>transplacental>insect vectors

28. • The Ridley Jopling classification
• Indeterminate
• Tuberculoid
• Borderline:
• borderline-tuberculoid,
• borderline-borderline,
• borderline-lepromatous
• Lepromatous

29. Indian classification (by indian leprosy
association)

30. • In TT is the most common form of leprosy

31. WHO Classification  treatment
Paucibacillary
• 1-5 lesion
• No nerve or only one nerve
• Skin smears –ve at all sites
• BI <2
• Involves IL BT TT
Multibacillary
• > 6 lesions
• > 1 nerve irrespective of skin lesions
• Skin smears + at all sites
• BI > 2
• Involves BB BL LL

33. Diagnosis
• Skin smears
• 7 in number
• 4 from skin lesion
• 2 from ear lobes
• 1 from nasal swb
• Nerve biopsy is taken from sural nerve

36. Morphological index response to Rx/drug
resistance/ disease activity/
• Percentage of solid staining bacilli in a stained smear to total no of
bacilli
Live bacilli  solid stained
Dead bacilli Fragmented

37. Bacteriological index  density of bacilli in
stained smear

38. • Bacilli are absent in lungs , ovaries and CNS
• Most common cranial nerve to get involve is VII
• Goll & burdech tract  proprioception
• Not involved in leprosy
• Other organs involved in leprosy are
• Eyes
• Iritis
• Corneal beading
• Testes
• Muscles
• Myopathy , wasting

39. Mouse foot pad culture
• Detect drug resistance
• Evaluating potency of antileprosy treatment
• Detecting viability of bacilli during Rx

40. Histamine test
• Very reliable method to detect at an early stage
• Peripheral N damage d/t leprosy  flare response is lost if peripheral N is
damaged

41. Lepromin test  to detect CMI / Test for prognosis
Early or Fernandez reaction
• after 48 hours of injection
• Erythema & induration >10 mm
is +ve
• Delayed hypersensitivity
reaction to soluble constituents
Late or Mitsuda reaction
• After 3 weeks
• Nodule > 5 mm is +ve
• indicates CMI to bacillary
component of Ag of lepra bacilli
Mitsuda lepromin / Dharmendra lepromin antigen intradermally
BCG vaccination can covert it from
negative to positive

42. Uses of lepromin test
• To classify lesions into tuberculoid or lepromatous
• To assess prognosis
• If positive  good prognosis
• Not used for diagnosis
• In the first 6 mth of life most children are lepromin negative

43. Nerve commonly involved
• Ulnar N  elbow (posteriorly)
• Median N  at wrist
• Dorsal cutaneous N of ulnar @ wrist
• Common peroneal  around fibular neck
• Superficial peroneal in front of ankle
• Posterior tibial  below medial malleoli

44. Great auricular N involvement

46. Nerve involvement

47. Types

49. Indeterminate leprosy
• Bacteriologically negative
• One or two vague hypopigmented macules
• Definite sensory impairement

50. Tuberculoid leprosy (most common type of
leprosy in INDIA and Africa
• CMI ↑↑
• Lepromin +ve
• Bacillary load ↓↓
• Skin lesions anaesthetic early
• One or few sharply defined
annular asymmetric macules or
plaques with a tendency towards
central clearing , elevated border

51. Tuberculoid leprosy histopathology
• Noncaseating granuloma with
epitheliod and giant cells

52. Grenz zone is involved in TL

53. Borderline Tuberculoid
• SATellite lesions
• Nerve Abscess (mainly ulnar nerve abscess)
• Rx with I & D
• SANTA BanTa
SATellite lesions

54. Borderline leprosy (BL)
• Inverted saucer shaped ulcers
• All kinds of bizzare lesions in single
patient distributed asymmetrically
• Epitheliod cells +

55. Lepromatous leprosy
• CMI ↓↓
• lepromin test negative
• Bacillary load ↑↑
• Temperature and pain lost first >>
Hypoaesthesia is a late sign
• Ulnar N most common >>low median
>posterior tibial>
• Radial N is involved last  serious
• Acral,distal,symmetric anaesthesia
common
• M.leprae PGL-1(phenolic glycolipid)
ab +

56. Lion with out teeth
• Leonine facies
• Atrophy of anterior nasal spine  collapse of nose
• Alveolar resorption Loosening of teeth
• Diffuse dermal infiltration of face
• Loss of eye brow

58. Lepromatousleprosy
Lionwithoutteeth&testis

59. Lepromatous leprosy
• Clear sub epidermal free grenz zone
• Virchow or lepra cells
• Foamy macrophages laden with acid
fast bacilli
• Intracellular bacilli in spheroidal
masses (globi)
• Epitheliod and giant cells are not seen
(absence of CMI)

61. Globi in LL/ AFB forming spherical cluster

62. Lucio phenomenon
• On lower extremities
• High parasitism in endothelial
cell  endothelial proliferation
 thrombus formation
• Characterised by arteritis and
ulcers on legs is limited to
patients with diffuse non
nodular lepromatous leprosy
• Untreated patients
• Mexico and carribean only

63. Histoid leprosy
• Type of LL
• Shiny cutaneous and subcutaneous
nodules
• Caused by drug resistant lepra bacilli
• In b/w skin appears normal

64. • Pure neuritic (indian classification)
• Asymmetric nerve involvement with no skin lesion and usually of tuberculoid
origin
• Painless trophic ulcers

65. Treatment
• Chaulmoogra oil
• First effective antileprosy Rx
• Form Myanmar
• MDT is used since 1982
• Not C/I in HIV infected patients and is safe in pregnancy
• Rifampicin  highly bactericidal and most effective against M leprae
• Dapsone is bacteriostatic

66. Blister packets for MDT

67. • Paucibacillary
• Under surveillance for
atleast 2years
• Multibacillary
• Under surveillance for
5vyeras

68. Treatment of single lesion leprosy
• ROM regimen
• Rmp
• Ofloxacin
• Minocycline
• ROM -6 (Monthly for 6 months) - Paucibacillary
• ROM -12 (Monthly for 12 months) – Multibacillary

69. Follow up
Annually for 2 years
Annually for 5 years

70. • Rifampicin is the most active (bactericidal & rapidly acting) for
leprosy

71. • In pure neuritic type
• Corticosteroids are also given along with multi drug therapy

72. Lepra reactions
Type 1 (reversal)
• Borderline type of leprosy (BT,BB,BL)
• In 1st month or yr after Rx initiation
• Sudden increase in effective CMI in
reponse to rapid killing of bacilli
• Type IV
• a/c tenderness and swelling at the site
of skin or nerve lesion
• a/c neuritis  wrist drop
• Rx
• Mild  NSAIDS
• Severe  high dose glucocorticoid
Type 2 (erythema nodosum leprosum)
• In lepromatoum leprosy and also in BL
• With in 2 years of RX
• d/t activation of t helper cells
• Type III HS (arthus reaction)
• Tender inflamed subcutaneous nodules
• Rx
• Glucocorticoids
• Thalidomide (DOC)
• Cloazimine
• Aspirin

73. Nosystemicfeatures

74. Type2leprareaction

75. Erythema nodosum leprosum
• Thalidomide  DOC

76. Downgrading reaction
• In untreated patients and in 3rd trimester of pregnancy
• Clinically mimic reversal reaction

77. Dapsone
• Bacteriostatic
• 1-2 mg/kg
• Half life >24 hours
• s/e
• Hemolutic anemia
• Methaemoglobinemia
• c./I
• Hb <7
• G6PD deficiency

78. clofazimine
• Dye with leprostatic and anti inflammatory property
• s/e
• Reddish brown discolourarion of exposed parts
• Hair and body secretions
• Dry & itchy skin

79. New drugs
• Rifapentine
• Most effective