Updates: Pseudomonas Outbreak from Oral Hygiene Product; VRE Super-Bug Spreads in Transplant Unit; Invasive Aspergillosis: How Likely Is It?
Pseudomonas Outbreak from Oral Hygiene Product
Source: ProMED-mail post, April 11, 2002. www.promedmail.org.
An increasing number of pseudomonas infections in hospital patients in Norway since August 2001 led to the discovery of a contaminated oral hygiene product, called Dento-o-sept, manufactured by Snogg Industri AS. Dent-o-sept is one of those pre-moistened oral foam swabs that are extensively used in hospitalized patients, especially in the intensive care unit and in ill patients who are unable to brush their teeth. The swabs are commonly saturated with oral mouthwash, glycerine and flavoring, and are not sterile. Pulsed gel electrophoresis identified a strain of pseudomonas contaminating this product, which had subsequently infected patients. Thus far, a total of 78 patients in 9 hospitals in Norway have been infected or colonized with this strain, and public health experts have begun a hospital-wide survey to identify other subjects. Distribution of the product, which has since been quickly halted, is limited to Norway and Denmark.
VRE Super-Bug Spreads in Transplant Unit
Source: Herrero IA, et al. N Engl J Med. 2002;346:867-869.
This report from the mayo clinic in Minnesota describes the transmission of a linezolid-resistant, vancomycin-resistant Enterococcus faecium ("Li-VRE") among 7 patients in their liver transplant unit. The isolate was first identified in a liver transplant recipient who received linezolid for 20 days for intra-abdominal infection. He was known to be previously colonized with a linezolid-susceptible VRE.
During routine surveillance of rectal swabs for VRE, the same multi-drug resistant Li-VRE isolate was subsequently detected in the stools of 6 other patients hospitalized on the same unit, none of whom developed clinical infection. All of the isolates carried the vanA gene, as well as a ribosomal mutation (G2576T 23s rDNA) conferring resistance to linezolid (mean MIC, 16 mg/mL). This mutation has also been recently described in a patient with Staphylococcus aureus, as well as 2 other isolates of E faecium and laboratory-derived mutant strains of E faecalis. The Mayo strain was also resistant to penicillin, ampicillin, gentamicin, and streptomycin but fortunately susceptible to quinopristin-dalfopristin (Q/D), as well as 2 newer investigational agents, oritavancin and tigecyclin.
The staff on this unit were previously required to use gloves when entering rooms—all of which were private. After this outbreak, all persons entering rooms were required to wear gloves and gowns. The emergence of Q/D and linezolid resistance in patients during treatment with these agents, as well as the ready transmission of these MDR isolates, especially in high-risk units, is of obvious concern. Clinical laboratories should begin gearing up to perform susceptibility testing of enterococci for Q/D and linezolid, rather than sending isolates out to specialized laboratories for testing, where the delay in receipt of results may be too long.
Invasive Aspergillosis: How Likely Is It?
Source: Perfect JR, et al. Clin Infect Dis. 2001;33:1824-1833.
This mycoses study group conducted an extensive evaluation of the diagnosis, risk factors, management, and outcome of 1209 patients with Aspergillus isolated from various clinical specimens (1477 positive cultures). The majority (81%) of the isolates were obtained from nonsterile sites, such as sputum (n = 733) and bronchioalveolar lavage (n = 344). Based on specific criteria, they focused on 245 cases, 148 of which were consistent with invasive Aspergillus (61% were definite and 33% were probable). The remaining 97 cases were believed to be consistent with chronic necrotizing aspergillosis, aspergilloma, or allergic bronchopulmonary aspergillosis.
Based on multivariate analysis, the likelihood of invasive disease in patients with a positive culture varied significantly. More than half of the patients (50-64%) with allogeneic bone marrow transplantation, neutropenia, or hematologic malignancy, and a positive culture from any site had invasive disease. Patients at intermediate risk included those with autologous BMT (28%), malnutrition (27%), corticosteroids (20%), HIV infection (18%), and solid organ transplant (17%). On the other hand, patients less likely to have invasive disease in the presence of a positive culture included those with diabetes (11%), pulmonary disease (9%), solid tumors (8%), and connective tissue disease (0%). Many patients had more than 1 risk factor, which significantly amplified the likelihood of invasive disease in the presence of a positive culture from any site. While the source of the specimens (sterile vs nonsterile site) is obviously important, the predictive value of a positive culture must be evaluated in the context of the underlying disease process. Although these data are interesting, there are many times in the clinical setting where the demand for empirical treatment in patients with a positive culture outweighs any "guesstimates" of the likelihood of disease, especially with the availability of the newer antifungals with reduced toxicity.
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