DIAGNOSIS OF 'TORCH' INFECTIONS - PRACTICAL METHODS

LABORATORY DIAGNOSIS OF TORCH INFECTIONS : 

LABORATORY DIAGNOSIS OF TORCH INFECTIONS Dr. P.SREENIVASULU REDDY MD Professor of MICROBIOLOGY NARAYANA MEDICAL COLLEGE NELLORE-2 ANDHRA PRADESH

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TORCH complex (TORCHES or TORCH infections) is a medical acronym for a set of congenital infections. T – Toxoplasmosis/Toxoplasma gondii O – Other infections (HBV,HIV,Syphilis,V-Z virus Parvo B19) R – Rubella C – Cytomegalovirus H – Herpes simplex virus

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Modes of transmission Toxoplasmosis Handling of excrement of infected cats, Drinking unpasteurized goat’s milk, Eating contaminated meat . Rubella Cytomegalo virus Herpes virus Salivary secreytions. Secretions from cutaneous ulcers. Cervical secretions Syphilis, HIV, HBV Sexula contact Blood & its products

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Usually presents as: Purpura, Jaundice, Cutaneous vesicles, oral ulcers, Intracerebral calcification, Chorioretinitis, and microcephaly, Deafness, Cataract, Congenital heart disease, Hepatosplenomegaly Intrauterine growth retardation.

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ANTI BODY DEMONSTRATION (Screening tests) ELISA METHOD. Direct agglutination Test. Indirect IF test. Complement Fixation Test.

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TIME TO PERFORM . At the time of 1st antenatal visit . Repeat Ig G (Serum) at mid trimester. (possibility of seroconversion) Amniotic fluid. Cord blood to know fetal infection.

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Serological test (ELISA) Serial serological testing is preferable. Diagnosis of acute infection : <12 weeks of gestation: Positive for IgG and IgM antibodies. If IgM nagative & IgG positive: Repeat after 3 weeks see for 4 four fold rise. If negative in early pregnancy: Do test at 18-20 weeks of gestation. (Joul. Of OBGI Feb-2006)

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Why Get Tested? When to Get Tested? Sample required To screen pregnant women And New born Suspected case of pregnancy. Flu-like symptoms & Rash while pregnancy. Baby born with congenital defects. Blood from a vein. Heelstick for infants.

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MICROSCOPY : Tachyzoites in smears of lymph nodes ,Brain ,Bone marrow . Stain :PAS Wright’s Giemsa . Tachyzoites in clusters : Acute infection CONFIRMATORY TESTS

SABIN –FELDMAN DYE TEST : 

SABIN –FELDMAN DYE TEST Live tachyzoites +Accessory factor +Test serum Alcoholic solution of Methylene Blue Dye Incubation at 370 C for one hr. If Abs are present If Abs are absent <50% of tachyzoites 90-100 % do not stain . tachyzoites Stain

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B) ISOLATION OF VIRUS : Tissue fibroblast cell culture .

Tissue cysts: Chronic /Latent infection : 

Tissue cysts: Chronic /Latent infection

DIAGNOSIS OF RUBELLOSIS : : 

DIAGNOSIS OF RUBELLOSIS : 1.Isolation of virus Blood Nasopharyngeal swab :Prodromal phase . Urine CSF . 1.SHELL VIAL culture . 2.CELL culture : RK13 , Rabbit cornea, Vero cells.

IMMUNO PEROXIDASE STAINING : 

IMMUNO PEROXIDASE STAINING

DIAGNOSIS OF CMV . : 

DIAGNOSIS OF CMV . SPECIMENS : Specimen from Active lesions of Cervix ,Vagina . Transport media :Leibovitz—Emory medium. CULTURE: Human Fibroblast cell line cultures.

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2.By immuno peroxidase staining using virus specific monoclonal antibody .

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H & E stain from cervical secretions of CMV infected individual.

DIAGNOSIS OF HSV : 

DIAGNOSIS OF HSV Direct Examination –Electron Microscopy . Tzank smear from secretions on Microscopy

IF staining of virus by using monoclonal antibodies . : 

Isolation : Cell line cultures: Human fibroblast cells. Vero cell line cultures. IF staining of virus by using monoclonal antibodies .

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CONFIRMATORY SEROLOGICAL TESTS 1.ANTIGEN DETECTION: ELISA. 2.MOLECULAR METHODS: PCR. DNA probes .