Q1 ] Toxoplasma infection in a human host can occur by which of following …..

(a) Unsporulated oocyst

(b) Sporulated oocyst

(c) Tissue cyst

(d) Tachyzoite

ANSWER = Both (b) and (c)

EXPLANATION ; We should first take a look on life cycle of toxoplasma.

Toxoplasmosis is caused by infection with the obligate intracellular parasite Toxoplasma gondii. There are two distinct stages in the life cycle of T. gondii….

(a) Non feline stage = which occurs in intermediate hosts (e.g., a human, mouse, sheep, pig, or bird) and starts with ingestion of sporulated oocyst ( source = materials contaminated with soil having cat excreta) or Tissue cyst ( having bradyzoite) which are formed in intermediate host and ingested by other intermediate host as undercooked meat eg ; human eating undercooked pork or lamb.


(b) Feline stage = definitive cycle = sexual cycle occur in cat ( definitive host) and its prey.

This phase is defined by the formation of oocysts within the feline host. This cycle begins with the ingestion of the bradyzoite tissue cysts and culminates  as an unsporulated oocyst being excreted along with feces. After 2-3 days noninfectious oocyst sporulates to produce eight sporozoite progeny in sporulated oocyst = infectve for intermediate host.


1. Definitive host = cat

2. Infective stage for definitive host = Tissue cyst ( by eating its prey eg rat)

3. Intermediate host = human , sheep , pig , rat , birds.

4. Infective stage for intermediate hosts = (a) sporulated oocyst having 8 sporozoite and (b) tissue cyst containing bradyzoite.

ALSO KNOW : The cyst( sporulated oocyst or tissue cyst ) rapidely digested in stomach to release sporozoite or bradyzoite which enters in gut epithelium forming tachyzoite . Tacyzoite mount systemic infection and after 7-10 days start forming TISSUE CYST.

NOTE : Apart from these a human can acquire toxo infection by transplacental passage or Transmission Via Blood or Organs.

Clinical features : Rabies

Three phases of disease :

(A) Prodrome

(B) Acute neurological phase

(C) coma and death

PRODROME( 2 – 10 days ) : After average incubation period of 20-90 days

(a) Local ; pain, paresthesia and pruritis  near site of bite strongly suggests development of Rabies.

(b) Systemic ; Fever ,malaise, headache, agitation etc

ACUTE NEUROLOGICAL PHASE : Note that there are two different presentations of this phase and typical presentations of rabies is seen in ENCEPHALITIC form of disease which is found in 80 % of patients and rest 20 % patients present with PARALYTIC form of disease .

ENCEPHALITIC FORM :{ Note that rabies is atypical encephalitis …. why? Because it doesnt show loss of conciousness as in ther encchephalitides , infact the patient is agitated in course of disease.} Clinical features are a sum of viral encephalitis features + autonomic dysfunction( hypersalivation, arrythmia, priapism) + prominent early brainstem involvement ( hydrophobia , aerophobia , painful  involuntary diaphragmatic contractions).

Cardinal feature of rabies encephalitis = Hyperexitability + Hydrophobia + Aerophobia.

PARALYTIC FORM : In about 20 % of patients the cardinal features of rabies does nt develop and it presents as muscle weakness begining in bitten extremity and procedes to Quadriparesis.

COMA AND DEATH : death usually within 2 weeks …. 100 % mortality.

Q 1] Which of following is not a cardinal feature of rabies …..

(a) Hyperexitability

(b) Hydrophobia

(c) Aerophobia

(d) Hypersalivation.

ANS = (d) see above { ref Harrisons manual of medicine 18ed/ page 718}


Bacillus anthrax : it is a gram + bacilli in bamboo stick or box car shape. on staining with polychrome methylene blue it shows MAC FADYEANS reaction which represent capsular material [ AiiMS 04,06,07].

Corynebacterium diptheriae : is a gram positive non motile rod. it contains granules called as Babes Ernst /volutin granules which r more strongly gram + . on staining with loeffers methylene blue granule shows metachromatism( AIIMS 07, PGI 2000). special stains to see granules are ALBERT, NEISSER,PONDER (JIPMER03).

MYCOBACTERIUM TUBERCULOSIS: ZN STAIN is used and it is acid fast. Auramine Rhodamine stain in which organism show reddish yellow fluorescence is used in  fluorescent microscopy( this is more sensitive than ZN staining).

NON LACTOSE FERMENTATER : ie colourless on mac conkey agar ; shigella ( except s. sonnei) . salmonella, proteus.

CHOLERA RED REACTION : it is due to nitrate reduction & sucrose ferfentation in v.cholerae

YERSINEA PESTIS : bipolar safety pin appearance with WAYSON STAIN (AI 2006), GIEMSA,  METHYLENE

T.PALLIDUM: silver impregnation method by using warthin starry silver stain. Fontana method is for staining  films and levaditi for tissue sections.

MYCOPLASMA: Colony is biphasic with “fried egg appearance”. when stained by. dienes method (PGI 95, 99)

CRYPTOCOCCUS NEOFORMANS:  it has polysaccharide capsule which is stained by india ink preparation. This is method of choice for detecting crypto in csf.(AI05,PGI 02)

FUNGAL STAIN: best ( most sensitive) fungal stain is gomori methamine silver stain. Best stain for fungal detection in biopsy sample is PAS ( Aiims 06)


cat scratch disease is caused by being scratched , licked or bitten by cats or kittens, etiological agent being  Bartonella henslae. Typical disease consists of papule vesicle or a nodule at site of innoculation which is followed by painful regional lymphadenopathy 1-3 weeks after cat contact. it resolves spontaneously in immunocompetent patients so antibiotic treatment is not routinely indicated.Azithromycin is only indicated in pt with extensive lymphadenopathy.



Q1) Empirical antibiotics are indicated in which of following tyes of animal bite even in immunocompetent patients …

a) dog bite 

2) cat bite  

3) fish bite 

4) human bite


ANS 2) cat bite,, as cat bites are the most likely animal bites to lead to cellulitis due to deep inoculation and frequent presence of pasteurella multicoda. so inimmunocompetent patient only cat bite require empirical antibiotics..



ALSO KNOW : other disease caused by bartonella.


TRENCH FEVER ( 5 day fever )  B quintana 

BARTONELLOSIS (  CARRION DISEASE) caused by B bacilliformis..( it is a biphasic disease, initial phase is called OROYA FEVER  and  late stage as  VERRUGA PERUANA )


NOTE : cry Du cat syndrome is caused by 5 p deletion.

cat eye syndrome is caused by extra chromosome 22..




REFERENCES :cpdt 17 e , harrison 18 e ,Image