'School of fish' appearance under microscope is seen in:
The causative agent of chancroid / soft sore is H. ducreyi. When examined by Gram stain, organisms from culture often clump in long parallel strands, producing a so-called "school of fish" or "railroad track" appearance. This morphology can occasionally be seen in Gram-stained smears from clinical specimens Chancroid is a genital ulcerative disease (GUD) and sexually transmitted infection characterized by soft (nonindurated) ulcers with irregular borders and tender inguinal lymphadenopathy, or buboes. The specimen of choice for the diagnosis is a swab that has been taken from the base of the genital ulcer. Culture is considered the 'gold standard'. H ducreyi can grow well on a chocolate Agar supplemented with 1% Iso VitaleX and 5% sheep blood or fetal calf serum. High levels of carbon dioxide are preferred. However, nucleic acid amplification methods are more sensitive.
Cholera
Chancroid
Syphilis
Diphtheria
Systemic Bacteriology (Haemophilus, Yersinia, Spirochaetes, Ricketssia, Chlamydia, Mycoplasma and Miscellaneous Bacteria)