<s>[INST] context: (a) Dark field microscopyLEPTOSPIRALeptospira, comprises of two species:* L. interrogans (pathogenic for humans): Causes leptospirosis or Weil's disease involving liver and kidney.* L.biflexa (saprophyte)* Mode of transmission:It is zoonotic. Direct human-to-human transmission does not occur. It is transmitted by:0 Indirect contact with water, moist soil and wet surfaces contaminated with animal urine or0 Direct contact with urine and products of parturition, placenta of infected animals* Source: Although >100 animals can be infected; but important sources of infection are rats, dogs, cattle, and pigs.* 3R's: Important epidemiological determinants for leptospirosis include exposure to rodents, rain f all and rice field.Clinical ManifestationsThe incubation period is around 5-14 days. In general, the manifestations can be divided into two distinct clinical syndromes.* Mild anicteric febrile illness: Occurs in 90% of patients. It is biphasic; septicemic phase followed by immune phase* Weil's disease (Hepato-renal-hemorrhagic syndrome): It is a severe form of icteric illness, occurs in 10% patients. Typical biphasic course may not be present. It is more severe and fulminant Mild anicteric febrile illnessWeil's diseaseFirst stage 3-10 days (septicemic)Second stage 10-30 days (immune)First stage 3-10 days (septicemic)Second stage 10-30 days (immune)Clinical FindingsFeverMyalgiaHeadacheConjunctivalsuffusionAbdominal painPharyngeal erythema without exudatesVomitingMeningitisUveitis, optic neutiris, chorioretinitisRashFeverPeripheralneuropathyHigh grade feverJaundice and raised liver enzymesHemorrhages:* Pulmonary hemorrhage* Petechiae and purpura* Conjunctival hemorrhage* GI hemorrhageKidney: Raised serum urea and creatinine and Renal failureIsolationFrom blood and CSFFrom UrineBlood and CSFUrineSerum lgMAbsentPresentAbsentPresentAntibioticsSusceptible to antibioticsRefractory to treatmentSusceptible to antibiotcsRefractory to treatmentLaboratory Diagnosis* Specimens: CSF and blood (in first 10 days of infection) and urine (between 10-30 days of infection)Microscopy: Leptospira are extremely thin, hence seen under dark ground microscope.* They are tightly and regularly coiled, with characteristic hooked ends like umbrella handle.* They are highly motile; exhibit spinning and translational movements.* Isolation:0 Culture condition: Leptospira is obligate aerobe and slow growing. Incubated at 30degC for 4-6 weeks.0 Culture media: As Leptospira is highly fastidious, requires enriched media such as: EMJH medium- MC media Korthof's media* Serology for antibody detection: Antibody detection tests can be broadly classified into:0 Genus specific tests uses broadly reactive genus specific antigen prepared from non-pathogenic L.biflexa Patoc 1 strain. They cannot detect the infecting serovar.Various tests available are: Macroscopic slide agglutination test Microcapsule agglutination test (MCAT) Latex agglutination test, ELISA and ICT Serovar specific test: Microscopic agglutination test (MAT) detects antibodies against specific serovars of L. interroagans. It is the gold standard method and reference test for the diagnosis of leptospirosis.* Molecular methods:0 Targeted genes are 16S or 23SrRNA or IS 1533 insertion sequence.0 PCR detects early before seroconversion occurs. However, PCR is not serovar specific.0 PCR-RFLP or PFGE are the methods to determine the genomospecies of Leptospira.* Fame's criteria is WHO approved guideline used for the diagnosis of leptospirosis. It is based on clinical, epidemiological and laboratory findings.Treatment* Mild leptospirosis: Oral doxycycline (Alternatively Amoxicillin)* Severe leptospirosis: Penicillin is the DOC (alternatively ceftriaxone/cefotaxime) [/INST] question: A patient was suffering from hepatorenal syndrome. A urine sample was obtained from the patient and was examined under the microscope. Which of the following technique is being used to make the organism visible? | options: A: Dark field microscopy B: Routine microscopy with negatively stained background C: Phase contrast microscopy D: Compound light microscopy | answer: A </s>