Comparison of PCR, immunofluorescence assay, and pathogen isolation for diagnosis of q fever in humans with spontaneous abortions.
Coxiella burnetii, an obligate intracellular parasite with a worldwide distribution, is the causative agent of Q fever in humans. We tested a total of 368 samples (placental bits, genital swabs, fecal swabs, and urine and serum samples) collected from women (n = 74) with spontaneous abortions for C. burnetii by a PCR assay targeting IS1111, the repetitive transposon-like region of C. burnetii (trans-PCR); real-time PCR; an indirect immunofluorescence assay (IFA); and the isolation of the pathogen. The IFA showed seropositivity for 25.68% of the women with spontaneous abortions, whereas trans-PCR and real-time PCR each detected the pathogen in 21.62% of cases. Overall, 25.68% of the subjects were positive by one or more assays. Real-time PCR showed a slightly higher level of sensitivity than trans-PCR. With the IFA as the reference, the two PCR assays showed a higher level of sensitivity (84.21%) than pathogen isolation (26.31%), while both the PCR assays and pathogen isolation were specific (100%). The detection of high numbers of C. burnetii cells in clinical samples and the frequent association of the pathogen with cases of spontaneous abortions observed in this study revealed that Q fever remains underdiagnosed and that the prevalence in India is underestimated.
Vaidya
V M
VM
Division of Veterinary Public Health, National Biotechnology Centre, Indian Veterinary Research Institute, Izatnagar, India. drvilasmvaidya@rediffmail.com
Malik
S V S
SV
Kaur
Simranpreet
S
Kumar
Satish
S
Barbuddhe
S B
SB
D000022:Abortion, Spontaneous / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology*; D000907:Antibodies, Bacterial / Q000097:blood*; D016997:Coxiella burnetii / Q000145:classification / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification*; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000032:analysis / Q000302:isolation & purification; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D007194:India / Q000453:epidemiology; D016133:Polymerase Chain Reaction / Q000379:methods*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology*; D015995:Prevalence; D011778:Q Fever / Q000175:diagnosis* / Q000453:epidemiology / Q000382:microbiology; D012680:Sensitivity and Specificity
D000907:Antibodies, Bacterial; D004251:DNA Transposable Elements; D004269:DNA, Bacterial