Spirochetes - Class Notes

Spirochaetes Long Essays

Question 1. Laboratory diagnosis of syphilis
(or)
Serological tests for syphilis
Answer:

1. Microscopy

It is useful in primary and secondary syphilis
Direct fluorescent antibody test is used for T. pallidum
In this method, acetone fixed smear is subjected to fluorescently tagged anti-T. pallidum antiserum

2. Serological Tests

Tests for antibodies reacting with cardiolipin anti¬gen
- Standard tests for syphilis
  - Wassermann test
It is a complement fixation test

Serological Tests For Syphilis Method:

The patient’s serum is inactivated by heating at 56s C for 30 minutes
Incubated with cardiolipin antigen and guinea pig antigen at 37° C for 1 hour
The indicator is added to detect the presence or absence of a compliment
0.15 ml of inactivated serum is taken in three test tubes containing 0.05, 0.025, and 0.0125 ml of freshly prepared antigen dilution
Tubes are shaken on Kahn’s and examined

Serological Tests For Syphilis Interpretation:

- If hemolysis does not occur, it indicates that the complement is utilized
- This is positive Wassmann’s reaction
- It hemolysis takes place, it indicates the comple¬ment is not been utilized in the tire’s primary reaction but utilized by the indicator system
- Kahn test
- It is a tube flocculation test
- The negative test shows uniform opalescence
- A positive test shows floccules
- VDRL test
- In this test, the inactivated serum is mixed with cardiolipin antigen on a special slide and rotated for 4 minutes
- The uniform distribution of crystals in the drop indicates tire serum is non-reacting
- The formation of clumps indicates it is reactive
Tests for antibodies reacting with group-specific treponemal antigen
- Reiter protein complement fixation test
  - In this method, lipopolysaccharide protein complex antigen derived from the cultivable Reiter’s stain is used
  - It is less sensitive
Tests for specific antibodies to pathogenic tre¬ponema
- Treponema pallidum immobilization test
  - It employs live T. pallidum
  - The test serum is mixed with actively motile Nichol’s strain of T. pallidum and incubated anaerobically
  - If antibodies are present, the treponemas are immobilised

Question 1. VDRL Test
Answer:

Venereal Disease Research Laboratory test is the most widely used serological test for diagnosis of syphilis
It is a simple and more rapid test that gives more quantitative results
It requires only a small amount of serum and is sensitive

VDRL test Procedure:

In this test, the inactivated serum is mixed with cardiolipin antigen on a special slide and rotated for 4 minutes
The uniform distribution of crystals in the drop indicates the serum is non-reacting
The formation of clumps indicates it is reactive
By testing serial dilutions, the antibody titer can be determined

Question 2. Vincent’s angina
Answer:

Vincent’s angina is a painful condition of the throat characterized by local ulceration of the tonsils, mouth, and pharynx
Vincent’s bacilli is the causative organism
It may occur as an acute illness with diffuse involve¬ment of tissue or as a chronic illness consisting of ulcera¬tion of tonsil
It is insidious in onset with less fever and less discom¬fort
The membrane that usually forms over the tonsil can be easily removed revealing an irregular ulcer on the tonsil

Question 3. Borrelia vincentii
Answer:

It is a motile spirochaete which is a normal mouth commensal but a potential pathogen.
Under predisposing conditions such as malnutrition (or) viral infections, it gives rise to ulcerative gin¬givostomatitis or oropharyngitis (Vincent’s angina).
Borrelia vincenti in association with fusiform bacilli causes an infection known as fusospirochetosis.
Diagnosis may be made by demonstrating spirochaetes and fusiform bacilli in stained smears of exudates from the lesions.
Cultivation is difficult but can be done in enriched me¬dia anaerobically.
Penicillin and metronidazole are effective in treatment.

Question 4. Congenital syphilis
Answer:

In congenital syphilis, the infection is transmitted from the mother to the fetus transplacentally.

Congenital Syphilis Clinical Features:

Hutchinson’s triad
- Hyperplasia of the incisor and molar teeth
- Interstitial keratitis
- Eight nerve deafness.
Frontal bossing
Saddle nose
High palatal arch
Poorly developed maxillae
Irregular thickening of clavicle
Enlarged liver and spleen
Diagnosis may be done by demonstrating spirochetes in lesions under dark dark-ground microscope.
IgM FTA – ABS test, the modification of indirect immune fluorescence test is useful for the diagnosis of congenital syphilis and distinguishing from seropositivity due to passively transferred maternal antibodies

Technic acid of the cell wall of staphylococci facilitates the adhesion of cocci to the host cell
ASO test is used for the diagnosis of rheumatic fever
Pneumococci gives draughtsman or carom coin appearance on blood agar
Modified Thayer Martin, selective media is used for meningococci
Corynebacterium diphtheria shows Chinese letter or cuneiform arrangement
DTP vaccine consists of diphtheria toxoid, tetanus toxoid, and pertussis vaccine
Bacillus coreus causes food poisoning
Clostridium contains peritrich flagella for motility
Widal test is used for diagnosis of typhoid fever
Dreyer’s tube and Felix’s tube are used in Widal test
Food poisoning is caused by any salmonella except salmonella typhi
Yersinia pestis is a causative agent of plaque or black death
Treponema pallidum is the causative agent for syphilis
VDRL test is used for syphilis
Actinomycetes gives sun ray appearance on culture
H payroll causes peptic ulcer