STOOL CULTURE: 1. Pathogenic organisms are Shigella, Salmonella, Campylobacter. 2. Stool general may reveal: a) Leukocytes and pus cells by methylene blue stain. b) Gram stain is not performed

3. Culture on McConkey & Eosin-methylene blue, & other selective media. Identify by biochemical reactions and antisera. Widal test is made for enteric fever. 4. C.jejuni is cultured on selective Skirrow agar at 42˚C in 10% Co 2.

URINE CULTURE : 1. Performed to diagnose pyelonephritis & cystitis. Organisms isolated are: E.coli, Prot., Enterobacter E.faecalis, Pseud., Klebs.

2. Midstream, morning urine sample is collected after washing external orifices. Suprapubic aspiration and catheterization may also be used for urine collection. 3. If there is delay culture urine within one hour after collection, or store at 4˚C for no more than 18 hrs.

4. Bacterial urine counts are made by inoculating the sample on McConkey agar using a 0.001(1µl) loop Then multiply number of colonies by 1000 (10 3 ).

@ Count interpretation : a)For symptomatics: significant count is 100 × 10 3 colonies/ml. b) For asymptomatics: significant count is only 100 colonies /ml.

GENITAL TRACT CULTURE: 1. Performed to diagnose gonorrhea caused by N.gonorrheae, using culture and microscopical examination.

2. Discharge is swabbed from urethra, cervix, & anal canal. It is inoculated quickly on Thayer-Martin, chocolate agar, or transported in trans-grow or Stuart media.

3. N.gonorrheae is identified microscopically as gram negative intracellular, diplococci within the pus (neutrophil) cell. 4. C.trachomatis may cause NSU. It is cultured on yolk sac of chick embryo or human tissue culture.

5. Syphilis T.pallidum is seen by D-F microscopy of a chancre fluid. Syphilis is diagnosed by non-specific VDRL, RPR & specific TPHA, FTA-ABS serological tests.

WOUND AND ABSCESS CULTURES: 1. Abscess is caused by Bacteroides, S. aurous, S.pyogenes. 2. Wound infections are due to C.perfringes, S.aurous, P.multocida.

2. Swab is transported immediately to lab. in thioglycolate or RCMM. Several aerobic and anaerobic media are inoculated.

SEROLOGICAL METHODS : There are two methods: 1.Identification of an organism with known antiserum:  Capsular swelling(Quelling) reaction: The capsule swells up when comes in touch with specific antiserum. Reaction is positive with S.pneumoniae, H.influenzae, N.meningitidis.

 Slide agglutination test: Used to identify Salmonella, & Shigella, looking for O, H, & Vi antigens.

 Latex agglutination test: Latex beads are coated with specific antibody, and agglutinated by homologous antigen. The test is used in diagnosis of H.influenzae, N.meningitidis, Cryptococcus neoformans.

 Counter immunoelectrophoresis test: The unknown bacterial antigen and the known specific antibody move towards each other and form a precipitate. The test is used to diagnose CSF pathogens, e.g.: H.influenzae, N.meningitidis, S.pneumoniae.

 ELISA: an enzyme is linked to the known antibody and used to detect the homologous antigen.  Fluorescent – antibody test: the known antibody is labeled with a fluorescent dye & detected by an U.V.microscope, either directly or indirectly when antibody unites with antigen.

2. Identification of serum antibodies with known antigens:  Slide & tube agglutination test Serial 2-fold dilution is made for patient serum and then bacterial antigen is added. Highest dilution of serum with agglutination shows the titre.

This test is to diagnose: enteric fever, brucellosis, plague, leptospirosis and rickettsial diseases.

 Serological tests for syphilis: Non-treponemal tests: using cardiolipin antigen: Rapid plasma regain (RPR) and VDRL Treponemal tests: include TPHA and FTA-ABS tests.

 Cold agglutinin test: Patients infected with Mycopl. pneumoniae will develop autoimmune antibodies that agglutinate human RBC at 4˚C but not at 37˚C.