infections with intraerythrocytic parasites, the morphologic characteristics observed on
microscopic examination of blood smears do not allow an unambiguous differentiation
between Babesia and Plasmodium. Moreover, potential blood
donors may have subclinical symptoms and very low parasitemia, undetectable in blood smears. In such cases, the diagnosis can be
derived from molecular techniques, such as PCR using the appropriate primers
and single-step, or the more sensitive nested PCR technique. In addition,
molecular approaches are very valuable in investigations of new Babesia
variants (or species) observed in recent human infections in the US and in
gel (2%) analysis of a PCR diagnostic test for detection of Babesia
microti DNA. PCR was performed using a nested protocol with
primers BAB1 and BAB41 (first round) and BAB2 and BAB3 (second round).1
- Lane S: Molecular base
pair standard (50-bp ladder). Black arrows show the size of standard bands.
- Lane 1:
First step amplification with primers BAB1 and BAB41 of the
nested PCR protocol for detection of B.
microti in DNA extracted from whole blood. The specimen,
serologically positive for B. microti, was
submitted to CDC by the American Red Cross. The red arrow shows the single-step PCR
band for B. microti (size: 238 bp).
Nested PCR with primers BAB2 and BAB31 using as template the
product of the first step amplification. The blue arrow shows the
nested PCR diagnostic
band for B. microti (size: 154 bp). Please note
the enhanced sensitivity of B. microti DNA detection with the
Persing DH, Mathiesen D,
Marshall WF, Telford SR, Spielman A, Thomford JW, Conrad PA. Detection of
Babesia microti by polymerase chain reaction. J Clin Microbiol 1992;30:2097-103.