Is enrichment culture necessary for clinical samples?

Inoculation of enrichment broth in addition to direct plating of tissue and fluid specimens has been recommended by some authors but not others.1,2 It is assumed that broth inoculation improves the recovery of clinically relevant isolates as it provides favourable growth conditions for organisms in low numbers, or where the sample may already contain antibiotics as a result of current treatment. Criteria determining the need to subculture the broth included moderate to large numbers of white blood cells (WBCs) seen on a direct Gram-stained smear of the original sample (>5 WBCs/high power field), tissue sent for culture or when the patient was diagnosed as human immunodeficiency virus (HlV)-positive or suffering from leukaemia or lymphoma.