Abstract
Here, we report on a study of acid-fast bacilli detection that we conducted at our clinic. We examined the detection of acid-fast bacilli, age distribution, sex differences, and the positivity rates for different test items in 1,898 specimens that were tested for acid-fast bacilli during a six-year period between April 2006 and March 2012. Over these six years, 12.0% of the specimens tested positive for acid-fast bacilli. When the age distribution was examined, no major changes were observed in the rates of detection of tuberculous or nontuberculous mycobacteria among patients aged 70 years or older. When sex differences were examined, the rate of detection of tuberculous mycobacteria was found to be high among men initially, but slowly decreased over time and became 50.0% for both men and women in 2010. The rate of detection of nontuberculous mycobacteria was high among women in 2006, but decreased afterward. Although clear differences between the sexes (for example, tuberculosis is predominant among men whereas nontuberculous mycobacterial infection is predominant among women) have been found, this study did not show such a trend. The patient age was 70 years or older in more than half of the cases where tuberculous or nontuberculous mycobacteria were detected. We sometimes also see young patients infected with tuberculosis bacilli at our clinic; thus, it is necessary to proactively consider the possibility of tuberculosis in young patients as well as elderly patients. When compared by test item, culture tests showed that a high percentage (≥ 80%) of specimens were positive for both tuberculous and nontuberculous mycobacteria. However, bacteria can sometimes be detected by smearing or Polymerase Chain Reaction (PCR) even when a specimen culture shows negative results, which indicates that it is important to conduct an assortment of tests. In addition, it is important to manage infections quickly and appropriately to prevent their spread after considering the geographical distribution.
