Direct Demonstration of Influenza Virus and Mycoplasma Pneumoniae in the Respiratory Tract

Abstract: Diagnostic tests based on nucleic acid amplification have become available for Mycoplasma pneumoniae (MP) and influenza viruses. Here, an MP PCR test detected 100% of infections during the first three symptomatic weeks, whereas classical serology detected 21% week 1, 56% week 2, and 100% week 3. Positive PCR results were uncommon in healthy individuals. Levels of MP DNA were significantly higher in hospitalized patients (considered to have more severe disease) than in outpatients. The MP pathogen load gradually fell during the course of the disease, and all patients cleared the bacteria. A Kaplan Meier survival curve for 60 patients indicated a median time of MP shedding of 7½ weeks. MP DNA was detected for up to 7 months. The MP genotype, MP1 or MP2, was determined in 83 samples by partial DNA sequencing of the P1 gene. The genotypes were found to co-circulate and were not related to disease severity. For influenza, the sensitivity of a fast membrane immunochromatography test was 71% during the first three days of illness and subsequently declined. No false positive results were detected. Turn-around time for these results (30 min) was 2.5 days shorter than for PCR results. Influenza virus persistence was studied using nasal flocked swab samples. The viral load was lower on day 1 of disease, peaked on days 2–3, and thereafter gradually decreased. A Kaplan Meier survival curve for 61 patients indicated a median time of viral shedding of 8 days. Influenza virus was detected up to day 12.