Gram staining of sputum as useful and early tool checking the effectiveness of antimicrobial agents in bacterial pneumonia and bronchitis

Abstract

The Gram staining is one of the most crucial staining techniques in microbiology. The use of Gram stain facilitates the rapid use of appropriate antimicrobial agents. In bacteria pneumonia, the most useful sample which reflect the inflammation in the lung is supposed to be sputum from the areas with infection in the lung. The changing patterns of Gram staining in the sputa can be used as the quickest indicator of the infection and as the therapeutic effectiveness of antimicrobial agent. When the first administered antimicrobial agent is effective against the target pathogen; S. pneumoniae, M. catarrhalis or Haemophilus influenzae, a decrease in number of the pathogen in the sputa was clear and almost no or little pathogen were seen in the sputum obtained several-hours after the first administration of antimicrobial agents or before the second administration which is mostly administered 8-12 hours-after the first one, showing that Gram-stained sputa is a definitive effective marker of the effectiveness of the agents. In pneumococcal pneumonia, a loss of gram-positive-staining of pneumococci was another early marker of the effectiveness of the agent. We can expect the effectiveness at least one hour after completion of the first administration of the agent, when a loss of gram-positive-staining of pneumococci with a decrease in number of cocci is found in the sputa. The reason for the loss of staining is supposed to be by reducing in peptidoglycan synthesis induced by antimicrobial agents distributed in the sputa. To find effective marker of administered antimicrobial agent in bacterial pneumonia or bronchitis, we compared the WBC and CRP levels and the decrease in the bacterial density in gram-stained sputa in which the administered antimicrobial agents were effective. The data showed that at least two to four days were needed to evaluate the effectiveness when the WBC or CRP level was used as a therapeutic parameter, but the median duration needed to determine the effectiveness of the agent was six and a half hours (range, 1 to 12 hours) in Gram-stained sputa, which showed that Gram-stained sputum after the first administration of antimicrobial agents can be used as the quickest therapeutic marker in treating bacterial respiratory infections. We showed that Gram staining of sputum is a useful effective tool to check the effectiveness of antimicrobial agents in bacterial pneumonia and bronchitis.