Updates

by Carol A. Kemper, MD, FACP

Advice for the Asplenic Traveler

Source: Watson AR. J Travel Med. 2003;10:117-121.

Extrapolating from epidemiological data, Watson and colleagues estimate that 1 in 300-500 travelers are asplenic. About 10% of splenectomized adults will experience overwhelming sepsis during their lifetime, about half of which will be fatal, although the risk is greatest for children and in the first 2 years following splenectomy. Immediate access to adequate medical care is critical to reducing the risk of fatal infection, which is often a problem when traveling.

In order to reduce these risks, Watson et al advocate the following guidelines for asplenic travelers. Most importantly, the patient should be cautioned to seek medical advice promptly for management of febrile illness. Standby antibiotic treatment, in the event of fever or respiratory symptoms, should be prescribed with the recommendation to start treatment immediately upon development of symptoms, even before (or en route) to medical care. Prophylactic antibiotic therapy can be considered, especially for travelers going to wilder areas or for longer durations of travel. Because of the possibility of more significant symptoms from malaria, adherence to malaria prophylaxis should be emphasized, and Watson et al advocate empiric treatment for symptoms suggestive of malaria if traveling to areas with limited medical care. Of the tick-born diseases, babesiosis may result in overwhelming infection in asplenic individuals, and patients traveling to endemic areas should be forewarned.

In addition, patients should be offered vaccination with the polysaccharide vaccines against S pneumoniae (23-valent) and N meningitidis (quadrivalent), as well as the conjugate vaccine for H influenzae, if they’ve not been recently vaccinated. General recommendations include revaccination every 5 years for S pneumoniae and every 3 years for N meningitidis. While vaccine responses may be diminished, vaccination may provide partial protection against fatal disease. In addition to these recommendations, serologic response can be verified; repeated vaccination for S pneumoniae can be attempted sooner than 5 years in patients with an inadequate response to vaccination, although there are no formal guidelines. There may be some advantage to the administration of the conjugate pneumococcal vaccine (which is more immunogenic), although it has not been approved for asplenic adults based on a lack of data. 


Persistent Bacteria in Cardiac Valve Tissue

Source: Morris AJ, et al. Clin Infect Dis. 2003;36:697-704.

The presence of persistent bacteria on Gram stain of valvular tissue in patients undergoing valve replacement or repair for endocarditis often results in prolongation of antimicrobial therapy, perhaps unnecessarily in some cases. Morris and associates retrospectively examined the frequency of microbiologic and histopathogic findings in 480 patients undergoing a total of 506 valve replacements or repairs. In patients who were still undergoing treatment at the time of their surgical procedure, positive Gram stains or histopathologic evidence of acute inflammation was common, although cultures were seldom positive.

In patients who had received more than 50% of the standard recommended antibiotic therapy, 69% and 52%, respectively, had positive Gram stains performed by the microbiology laboratory or in histopathologic specimens, but only 9.8% had positive cultures. In patients who had received more than 100% of the recommended therapy, 65% still had positive Gram stain results performed by the micro lab, 55% had pathology specimens with evidence of organisms, and 9% had positive cultures. Acute inflammation was seen in 21% of valve specimens. Even in those patients who had completed therapy within the previous month, 47% had positive Gram staining of ground valvular tissue, but none had positive cultures.

In conclusion, because nonviable organisms may persist in valvular tissue for weeks to months, microbiologic and histopathologic evidence of organisms in valve tissue is quite common following valve replacement or repair. Continued antibiotic therapy, beyond the usual standard recommendations, should therefore be considered only for those cases that remain culture positive. Morris et al propose that pathologists reconsider the description of "active" endocarditis based on the presence of inflammation alone.

Dr. Kemper is Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases; Santa Clara Valley Medical Center Section Editor, Updates Section Editor, HIV