C. pneumoniae Causes Infectious Outbreaks in Nursing Homes
Acute respiratory infections are a substantial source of morbidity and mortality in the elderly, yet little study has been done in the role of Chlamydia in outbreaks of respiratory disease among elderly persons in nursing homes. The Centre for Disease Control of Ottawa, Canada, was invited to investigate outbreaks of acute respiratory illness in three nursing homes that had resulted in pneumonia and some deaths.
Respiratory case surveillance was done using a case definition requiring three or more of the following clinical events: new cough, chest congestion, sore throat, fever, or nasal discharge.
In nursing home A, an outbreak occurred September 12-October 26; 68% of residents had respiratory illness. In nursing home B, the outbreak occurred October 1-31. In nursing home C, the outbreak occurred October 6-November 14.
Thirty to 50% of the ill residents had at least four-fold titer rise of C. pneumoniae during the study period, whereas among asymptomatic persons (nursing home A) 11% demonstrated antibody titer rise. Direct fluorescent antibody assay was felt to be the only laboratory tool that proved to be useful in a timely fashion.
Since macrolide antibiotics and tetracyclines are the agents of choice for treatment of Chlamydia, clinicians should be aware that this pathogen, just like the more familiar influenza and S. pneumoniae, can produce rapid onset of respiratory disease outbreaks in elder populations in nursing homes.
Troy CJ, et al. JAMA 1997;277: 1214-1218.
Clinical Scenario: The rhythm in the Figure was obtained from an older adult who presented in pulmonary edema. The patient was alert but in acute respiratory failure at the time this tracing was recorded. As shown in the figure, the telemetry recording interpreted this rhythm as ventricular tachycardia. Do you agree?
Interpretation: This is a difficult tracing to interpret. As noted above, the patient is in marked respiratory distress. This accounts for the wandering baseline and large amount of artifact. Nevertheless, the first two beats in the tracing appear to be sinus conducted--as suggested by a narrow and relatively normal-appearing QRS complex that is preceded by an upright P wave in this lead II recording. (The letter P indicates the P wave in front of the second QRS complex.) Note that the R-R interval between these first two sinus beats is four large boxes, which corresponds to a sinus rate of 75 beats/minute.
Thereafter, things change. Specifically, a series of large amplitude undulations at an exceedingly rapid rate is seen. However, despite telemetry indication of this run as "VENT FIB/TACH"this is not the true interpretation of this rhythm.
The key to arriving at the correct diagnosis lies with use of calipers and appreciation that the underlying mechanism is normal sinus rhythm at a regular rate of 75 beats/minute. Set your calipers to this rate (i.e., to an R-R interval of 4 large boxes). While maintaining this setting, "walk" the calipers through the rhythm strip. Note that each advance of the calipers falls right on a narrow upright deflectionthat in fact represents persistence of normal sinus rhythm at a regular rate of 75 beats/minute throughout the tracing. Admittedly, many of the QRS deflections are at least partially hidden by the large amplitude sinusoid-like undulations. Nevertheless, QRS complexes are regularly occurring every four large boxes. For example, directly above the letters x and y on this tracing are seen small narrow upright deflections that correspond to the fourth and fifth QRS complexes.
The large amplitude sinusoid-like undulations do not represent sinus tachycardia. They can’tbecause many of them occur too soon after the QRS complex (at a time when the absolute refractory period is operative). Proof that these large amplitude undulations represent artifact is forthcoming from the fact that the underlying rhythm (which is sinus) continues at a regular rate (of 75 beats/minute) throughout the tracing.