Bacteria,Yeasts, Parasites, Spermatozoa in urine

Bacteria- A properly collected urine specimen from a healthy individual should be free from bacteria. Presence of bacteria in a fresh urine indicates infection. Urine is a very good medium for the growth of bacteria. Therefore, even a few bacteria, whether as a result of infection or contamination, can grow into large numbers if unpreserved urine is allowed to stand at room temperature for a long time. Bacterial infection is generally associated with increased number of leukocytes.

Most bacteria causing urinary tract infection are bacilli, which are rod shaped organisms measuring 0.5-1.0 x 2-5 um in size. Sometimes cocci may also cause infection. They are spherical bacteria and measure about 1.0 um in diameter.For bacteriological examination of urine, refer to Bacteriology in Microbiology section.

Yeasts-- Yeast cells are oval cells, some of which may show budding. They are about the same size as red cells and can be mistaken for them. To differentiate, a drop of 2% acetic acid should be added to the sediment and only the red cells will be lysed.

Yeast cells appear in urine as a result of contamination from women with vaginal candidiasis. They may also be seen in the urine of diabetic patients due to the presence of sugar in the urine. They may cause recurrent infections in debilitated and immunocompromised patients. A fresh, properly collected specimen of urine should be examined to differentiate between an infection and contamination.

Parasites Except for the ova of the trematode parasite Schistosoma haematobium, all other parasites or ova appearing in urine are a result of faecal or vaginal contamination. These include Trichomonas, a flagellated protozoan slightly larger than leukocytes showing a typical motility; amoebae such as Entamoeba histolytica and adult worms such as Enterobius vermicularis.

The eggs of Schistosoma haemotobium are elongated measuring 110-180 X 40-70 um, and have a distinctive terminal spine. The ova are usually accompanied by red cells from the urinary bladder. Microfilariae of Wucheteria bancrofti may appear in urine rarely, especially when the urine is milky white (chyluria)

Spermatozoa Spermatozoa may also be present as urinary contaminants. They have oval heads with long delicate tails.

Note

1. Mucus strands Strands of mucus may appear in urine and can be mistaken for casts. Unlike casts, they have undefined edges and pointed or split ends.

2.Artefacts Cotton fibres, hair, fibres from diapers, wood fibres from applicator or mixing sticks and starch granules can be mistaken for various formed elements of urine. Careful examination can distinguish them.