C. pneumoniae as a Common Cause of Persistent Cough
Abstract & Commentary
Synopsis: Chlamydia pneumoniae is a significant cause of prolonged cough.
Source: Wright SW, et al. Prevalence of positive serology for acute Chlamydia pneumoniae infection in ED patients with perisitent cough. Acad Emerg Med 1997;4:179-183.
Editor’s Comment: This study is strongly suggestive that C. pneumoniae may be a cause of persistent cough in adults. However, the diagnosis in these cases was based upon serological results, a methodology that is increasingly recognized as often inaccurate when applied to this disease. Furthermore, in the absence of data from a matched control group, the conclusions of Wright et al require confirmation before they can be accepted. It is, of course, increasingly important to define the epidemiology of C. pneumoniae infection, given the mounting evidence of its association with coronary artery disease.
Assuming that C. pneumoniae is a frequent cause of persistent cough in adults, it is not the only infection with important public health consequences that does so. Pertussis has been demonstrated in two settings a half-continent apart (San Francisco and Memphis) to be associated with 12.4%-20% of coughs of at least two weeks duration in adults (Wright SW, et al. JAMA 1995;272:1044-1046; Nennig ME, et al. JAMA 1996;275:1672-1674). Pertussis in adults is the major resrvoir for pertussin in children.SD
Arecent study by wright et al examined a convenience sample of 75 patients who presented to the emergency department (ED) complaining of cough lasting between two weeks and three months. Patients with a history of malignancy, HIV, or asthma-induced cough were excluded, as were those diagnosed with pneumonia, tuberculosis, lung abscess, or foreign body aspiration. Treatment was left to the discretion of the clinician. Subjects had serologic testing for Chlamydia pneumoniae performed at the time of presentation (acute titer) and again in four weeks (convalescent titer). Acute chlamydia infection was defined as a fourfold rise in either IgM or IgG antibody titer between acute and convalescent samples, acute IgM titer more than 16, or acute IgG titer more than 512.
Sixty-five patients (mean age, 35 years) had samples adequate for testing and were ultimately included in the analysis. Twenty percent of these subjects had serologic evidence of acute C. pneumoniae infection. There were no demographic or clinical factors that distinguished those with C. pneumoniae. The typical patient had no fever or leukocytosis and was not a smoker. Sputum production was seen in the majority.
Wright et al conclude that C. pneumoniae is a significant cause of prolonged cough among ED patients.
COMMENT BY DAVID J. KARRAS, MD
During the 1990s, C. pneumoniae, formerly known as the TWAR strain of chlamydia, has gone from a newly identified cause of illness to recognition as a relatively common cause of tracheobronchitis in healthy adults. The typical illness is characterized by an acute upper respiratory infection associated with pharyngitis, sinusitis, or wheezing, followed by a persistent cough. The present study, however, demonstrates that the infection is common among patients presenting only with a cough of several weeks’ duration.
My practice regarding therapy for patients with persistent cough has been altered by recent studies of C. pneumoniae. I am more inclined to use antibiotics rather than to instruct patients to ride out what I assumed to be a post-viral recuperation phase. I also tend to use macrolides (erythromycin, azithromycin, or clarithromycin) and tetracyclines rather than amoxicillin or trimethoprim-sulfamethoxazole. Fortunately, the antibiotics effective against C. pneumoniae are also appropriate for other bacterial causes of community-acquired bronchitis, such as Streptococcus pneumoniae and Mycoplasma pneumoniae. Anecdotally, I have witnessed many cases of dramatic resolution of weeks of coughing after empiric initiation of antibiotic therapy intended to cover C. pneumoniae. That being said, it is important to acknowledge that there is no firm evidence that antibiotics shorten the course of C. pneumoniae infection; furthermore, longer courses of therapy may be necessary. (Dr. Karras is Assistant Professor of Medicine, Temple University School of Medicine, Director of Emergency Medicine Research, Temple University Hospital, Philadelphia, PA.)
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