Spirochetes Question And Answers

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. pal¬lidum
In this method acetone fixed smear is subjected to fluorescent 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:

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
Indicator is added to detect presence or absence or complement
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 shaken and examined

Serological tests for syphilis Interpretation:

- If hemolysis does not occurs, 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 tire primary reaction but utilized by the indicator system
- Kahn test
- It is tube flocculation test
- Negative test shows uniform opalescence
- 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
- Uniform distribution of crystals in the drop indi¬cates tire serum is non reacting
- 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 simple and more rapid test which gives more quantitative results
It requires only small amount of serum and is sensitive

VDRL test Procedure:

In this test the inactivated serum is mixed with cardi- olipin antigen on a special slide and rotated for 4 min¬utes
Uniform distribution of crystals in the drop indicates the serum is non reacting
Formation of clumps indicates it is reactive
By testing serial dilutions, the antibody titre can be determined

Question 2. Vincent’s angina
Answer:

Vincent’s angina is a painful condition of the throat characvterized 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 chronic illness consisting of ulcera¬tion of tonsil
It is insidious in onset with less fever and less discom¬fort
Membrane which usually forms over the tonsil can be easily removed revealing 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 mother to foetus transplacentally.

Congenital syphilis Clinical Features:

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

Techoic acid of cell wall of staphylococci facilitates adhesion of cocci to host cell
ASO test is used for diagnosis of rheumatic fever
Pneumococci gives draughtsman or carom coin ap-pearance on blood agar
Modified Thayer Martin, selective media is used for meningococci
Corynbacterium 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 peritrichate flagella for motility
Widal test is used for diagnosis of typhoid fever
Dreyer’s tube and Felix tube are used in widal test
Food poisoning is caused by any salmonella except salmonella typhi
Yersinia pestis is causative agent of plaque or black death
Trepnema pallidum is causative agent for syphilis
VDRL test is used for syphilis
Actinomycetes gives sun ray appearance on culture
H pyroli causes peptic ulcer