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By Carol A. Kemper, MD, FACP, Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases; Santa Clara Valley Medical Center, Section Editor, Updates; is Associate Editor for Infectious Disease Alert.
Utility of Pneumococcal Urinary Antigen
Source: Sordé R, et al. Current and potential usefulness of pneumococcal urinary antigen detection in hospitalized patients with community-acquired pneumonia to guide antimicrobial therapy. Arch Intern Med 2011;171:166-172.
Community acquired pneumonia "bundles" often include the use of the pneumococcal urinary antigen assay, but how useful is it for streamlining antibacterial use?
Sordé and colleagues prospectively examined 474 sequential episodes of community-acquired pneumonia in 464 patients. A diagnosis was made in 269 (57%) cases; 171 (36%) were due to pneumococcus based on the results of cultures of blood (53), pleural fluid (5), and/or sputum (38), or exclusively by urinary antigen (75). Of those with a positive culture for Streptococcus pneumoniae, pneumococcal urinary antigen tests were obtained in 50, yielding 39 (78%) positive results. The sensitivity of the assay was therefore 78%, with a specificity of 96%, and a positive predictive value of 88.8%-96.5%.
The median time to obtaining a pneumococcal urinary antigen test result and physician modification of antibiotics was about 2 days, and occurred in 41 patients (8.6%). The use of the urinary antigen test helped to identify an additional 44% of pneumococcal pneumonia infections, providing further opportunity for antibiotic reduction. The concurrent use of the Legionella pneumophila urinary antigen test also identified 14 cases of legionella pneumonia important information when rendering therapeutic decisions.
Histoplasmosis in Travelers
Source: Buitrago MJ, et al. Histoplasmosis and paracoccidioidomycosis in a non-endemic area: A review of cases and diagnosis. J Travel Med 2010;18:26-33.
Twice in the past 2 years I've encountered pulmonary histoplasmosis in travelers returning from Central America (Mexico and Costa Rica), and both times the diagnosis proved challenging. One case, in particular, was a 60-year-old man who had traveled to Costa Rica for one week and then presented with fever, persistent dry cough, malaise, and complaints of memory loss. Only a biopsy of lung tissue confirmed the diagnosis of carcinoid tumor, bronchiolitis obliterans, and histoplasmosis (based on histopathology; cultures were negative).
These authors at the Spanish Mycology Reference Laboratory in Madrid, Spain, describe their experience with the laboratory detection of histoplasmosis and paracoccidioidomycosis (PCM) in returning travelers and immigrants, including the use of a novel PCR-based technique based on DNA amplification of the internal transcriber spacer region of H. capsulatum var. capsulatum, H. capsulatum var. duboisii, and P. brasiliensis. Precipitating antibodies were detected using immunodiffusion assay.
Since 2006, histoplasmosis was diagnosed in nine returning travelers and 30 immigrants; most had come from South America (83%), Africa, or both. The nine travelers had no underlying disease, and were diagnosed with probable histoplasmosis based on positive immunodiffusion test results. The organism was not cultured in any of these patients. RT-PCR was positive in five, including three of seven serum specimens, two of three lung biopsies, and one of one sputum specimen.
In contrast, all 30 immigrants were diagnosed with disseminated histoplasmosis; 97% of these were HIV-infected and the remaining patients had a hematologic malignancy. Of these, 97% were diagnosed with proven histoplasmosis based on a positive culture or visualization of the organism in tissue specimens; only one patient was diagnosed based on the results of RT-PCR alone. Immunodiffusion testing was performed in 20 patients, and was positive in eight (40%), whereas RT-PCR was positive in 24 of 27 patients tested (89%; this included plasma or serum, bone marrow biopsy, or other tissue biopsy). Three patients from Africa were found to have H. capsulatum var. duboisii based on RT-PCR results.
Six patients, all immigrants from South America, were diagnosed with PCM; all six had positive immunodiffusion assays for PCM (which were weakly positive in three), and all six had a positive RT-PCR of plasma or serum, bronchoalveolar lavage, lung biopsy, or other biopsy.
Pulmonary histoplasmosis should be suspected in any traveler returning from Central or South America with fever, headache, malaise, dry cough, and chest discomfort (especially if they have visited caves), although confirming the diagnosis may be challenging. Immunodiffusion assays are helpful in many patients, but it may be necessary to obtain tissue.
HIV Transmission and Premastication of Food
Source: Centers for Disease Control and Prevention. Premastication of food by caregivers of HIV-exposed children nine U.S. sites, 2009-2010. Morb Mortal Wkly Rep 2011;60:273-275.
HIV transmission generally is not believed to occur from contact with saliva (it has been estimated that there is approximately one HIV particle in a gallon of saliva) although patients with dental or gingival disease may transmit virus through close contact, such as deep kissing or oral sex. Approximately 13% of pediatric HIV infection is believed to occur through mechanisms other than perinatal exposure. It was only recently discovered that transmission in three children had occurred because they were being fed food pre-chewed by their HIV-infected mothers. Prompted by this discovery, the Centers for Disease Control and Prevention (CDC) conducted a survey of pediatric HIV clinics at nine centers throughout the United States. These clinics included both HIV-infected and non-HIV-infected children born to HIV-infected mothers.
Caregivers of pediatric patients attending the clinics were surveyed regarding the practice of pre-chewing food fed to small children. Since children younger than 6 months are more likely to be bottle-fed, the survey focused on those 154 primary caregivers with children ≥ 6 months of age. Amazingly, 48 (31%) reported that they or someone in the household fed their child pre-chewed food; most (79%) of these were the biological HIV-positive mothers, and the rest were other members (possibly HIV-infected) of the household. Premastication was more common among younger mothers and non-Hispanic black women. Two-thirds of the respondents reported this was a common practice, and occurred at least once per week. Common reasons for this practice included the child wanted "adult food," they were afraid the child would "choke on real food," and because it was common practice in their family. Premastication may, in fact, be a part of certain cultures.
Based on these results, the CDC recommends that caregivers in pediatric HIV clinics be counseled about the risk of pre-chewing food for their young children. Other infections that may be transmitted through this practice include HSV, group A Strep, Helicobacter pylori, and other enteric pathogens as well as syphilis (see Infectious Disease Alert, May 2009). Syphilis has been reported in two infants as the result of transmission from the parent (or grandparent) with secondary syphilitic oral lesions.1
Source: Rothberg MB, et al. Phantom vibration syndrome among medical staff: A cross sectional survey. BMJ 2010;341:c6914.
Infectious diseases may be the most heavily curb-sided specialty (see Infectious Disease Alert, November 2010). There are times when I am glued to the phone with "beeper paralysis," and check my pager "just in case." The term "phantom vibration" was first described in 2007 in a survey of cell phone behavior, where two-thirds of cell phone users described phantom rings. The term has become increasingly popular, moving on to the Net and Facebook.
Rothberg and colleagues wondered how often this phenomenon might affect medical personnel who carry cell phones and pagers. They conducted a survey of 176 hospital medical staff (including 160 attending physicians, residents, and medical students) who regularly carried a pager in hospital. Phantom vibrations occurred with 68% of cell phones users and 69% of those with pagers. The majority had been carrying their pagers for at least 1 month, and 99% used their device ≥ 6 hours per day; one-third used their device ≥ 12 hours per day. Nearly half (46%) received an average of five or more pages per hour, and nearly half (46%) indicated their maximum number of pages per hour was in the range of 11-15. One-fourth received a maximum of 15 or more calls or pages per hour.
Phantom vibrations occurred daily (13%), weekly (39%), or monthly (49%). Risk factors associated with phantom vibrations included younger age, being a resident or medical student, frequency of use, and keeping the device in a breast pocket. Most respondents agreed the sensation was not at all or "only a little" bothersome, but 2% found the sensation bothersome or "very bothersome" (worse than being paged?). Strategies to reduce the sensation included turning the device off or removing the pager (!) but moving it to another location sometimes helped.
Because younger age was more frequently associated with this phenomenon, the authors likened it to "new mom syndrome" (listening for the baby crying), but I imagine the hyperacute state (and, at times, sheer anxiety) of taking primary hospital call is more likely to trigger the sensation.