Updates
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; Section Editor, HIV, is Associate Editor for Infectious Disease Alert.
Legionella pneumophila in Rainwater on Roads
Source: Sakamoto R, et al. Emerg Infect Dis. 2009;15:1295-1297.
Epidemiologists have pondered the possible environmental source for sporadic cases of legionella infection in humans. Limited evidence suggests an association with rainfall, with one outbreak occurring following a heavy storm. Following an episode of legionella pneumonia secondary in a commercial truck driver, these researchers decided to test whether puddles of rainwater on roadways could be a potential source for infection.
Multiple 100 mL samples of rainwater were suctioned from four different points on an asphalt road outside of Kyoto. Direct samples of rainwater were also collected, and sterile containers were placed on the roadside to collect rainwater spray from the roads. In addition, swab specimens of dry asphalt were collected on sunny days. The specimens were mixed and plated on WYO plates and incubated for seven days. A loop-mediated isothermal amplification (LAMP) kit was used to detect Legionella spp., and PCR primers were used to detect 18s rDNA from free-living acanthamoeba.
Initial cultures yielded L. pneumophilia spp from seven of 18 roadways rainwater puddle specimens. Sixteen of 45 specimens taken from puddles at the four different observations points were also positive. Samples collected from these same areas on sunny days were all negative by culture, but two of 12 specimens were positive using LAMP technique, consistent with the presence of viable but non-replicating organism. While direct rainwater specimens were negative for organism, 10% of samples from the roadside yielded legionella.
The yield in culture appeared dependent on the ambient temperature — cultures at < 20 C, 20-25 C, and > 25 C yielded organism 16%, 43%, and 58% of the time. Colony counts were generally < 100 CFU/mL, although nearly one-fifth were higher. A total of 150 strains of L. pneumophila were isolated (37% belonged to serogroup 1). Free-living acanthamoeba spp were detected by PCR from four of 18 puddles, and two of 10 swab specimens from roadways on sunny days.
The authors hypothesize that rainwater on roadways, especially on warmer days, can result in aerosols of viable legionella as passing cars create water sprays. The presence of free-living amoeba, which are known to ingest L. pneumophila, may contribute to the reactivation of more dormant organisms.
Resistant H1N1 Goes to Summer Camp
Source: Oseltamivir-resistant pandemic influenza A (H1N1) 2009 virus infection in 2 summer campers receiving prophylaxis - North Carolina, 2009. MMWR. September 2009.
Reports of oseltamivir-resistant H1N1 viral infection thus far have been limited to a handful of cases in the United States (well, perhaps two handfuls now). While the WHO has reported multiple cases of oseltamivir-resistant virus isolated from patients who developed active infection during receipt of chemoprophylaxis, the frequency of this occurrence is not known. The CDC revised its flu guidelines 9/08/09, stipulating that only persons at higher risk of complications from influenza, with significant exposure, should receive chemoprophylaxis, and instead placed emphasis on observation and treatment for active symptoms as needed.
This is not what occurred at camp this summer. During an outbreak of H1N1 at a camp in North Carolina in June, more than 418 campers and 189 staff members received a 10-day course of oseltamivir chemoprophylaxis for exposure to influenza. A total of 65 persons (61 campers and four staff members) with influenza-like illness (ILI) were segregated, and all but one was treated for the flu.
During this outbreak, one previously healthy teenage girl had just completed one 10-day course of oseltamivir when, three days later, she was again exposed to someone with the flu, prompting a second course of oseltamivir (TamifluR).
Within one day, she developed cough and headache but no fever, but there was no change in her chemoprophylaxis. She hung out at camp, went home with her folks for a couple of days, and returned to camp on day five of prophylactic treatment — at which point, she had a positive nasopharyngeal swab rapid screening test for Influenza A. Her dose of oseltamivir was increased to the usual BID treatment dose.
Her cabin mate also had been started on oseltamivir chemoprophylaxis at the same time. Three days into her prophylactic treatment course, she traveled home with her family, and the following day, developed fever, sore throat, and cough. Despite ongoing symptoms, she went shopping at the mall and to the movie theater(!). Upon returning to the camp on day five, she also had a positive rapid screening test for Influenza A, at which point zanamivir treatment was begun; both girls recovered uneventfully.
Further specimen obtained from both girls at day seven confirmed the presence of H1N1 virus using rRT-PCR, and subsequent molecular studies at the CDC confirmed the H2754 mutation known to be associated with oseltamivir-resistance; viral cultures were negative.
Six other persons at the camp developed ILI while receiving chemoprophylaxis, but specimens taken from only one of these proved negative. Fifty-nine surveillance specimens yielding H1N1 virus from this part of North Carolina showed no evidence of the H2754 mutation, and there was no direct evidence that resistant infection had been transmitted by the girls. None of their family members developed illness. Whether the girls acquired resistant virus from a common source, or whether the first teen developed resistant virus during chemoprophylactic treatment and shared it with her cabin mate, is unknown.
Late Relapses of Multibacillary Leprosy
Source: Fajardo TT, et al. A comparative clinical trial in multibacillary leprosy with long-term relapse rates of four different multidrug regimens. Am J Trop Med Hyg. 2009;812:330-334.
These authors followed 189 patients treated in the Phillipines for multibacillary (MB) leprosy with four different regimens, most of whom were followed for at least nine years, and up to 12 years for some. The study included 147 men and 42 women, with a mean age of 28 years at diagnosis (15-60 yrs). To participate in this study, patients were required to have > 2 +AFB on one or more skin smears; most of the patients recruited were either LL or BL on biopsy. Relapses were evaluated by an outside expert not directly involved in the project, and viability of organism was confirmed using mouse footpad inoculation.
Patients were followed for a total of 1,728 patient-years, and an average of 82% of the patients were seen on a regular basis at annual follow-up. Patients were assigned to one of four drug regimens (see Table), and the first month of therapy was directly observed.
Nine years following initiation of therapy, relapse occurred in one of 57 patients (1.87%) receiving regimen A (at year six), one of 55 patients (1.87%) receiving regimen B (at year seven), and no relapses occurred in patients receiving regimen 4. (Another late relapse occurred at year nine in a patient randomized to regimen B, but was lost to follow-up after one month.)
In contrast, seven of 64 patient receiving short-course therapy in regimen C relapsed, all within five to seven years. The overall relapse rate at nine years (11%) and at 12 years (25%) for patients receiving the short-course therapy was significantly greater than patients treated with any of the other WHO-based regimens Two-thirds of the patients who relapsed had high bacteriologic loads with > 4 +AFB skin smears at baseline. (The authors presumed that all patients with recurrent infection had relapsed, although they acknowledged that re-infection was possible).
Relapses generally remained sensitive to therapy, and none of the isolates were multi-drug resistant. The patient who had been lost to follow-up proved to have a rifampin-resistant organism upon representation; one patient's isolate developed resistance to clofazimine and one had low-level resistance to dapsone.
Remarkably, despite the impressive length of follow-up, only 0%-3% of patients appear at risk for relapse following receipt of a WHO-based, longer-term, MDT regimen. Relapses occurred much later than anticipated, and generally occurred at least six to seven years after initiation of treatment. Even patients who received short-course chemotherapy, who were at greater risk for failure, relapsed at least five to nine years after their initial treatment. Long-term follow-up, for up to 9-12 years, with annual exams and screening smears for patients with MB leprosy is important.
Epidemiologists have pondered the possible environmental source for sporadic cases of legionella infection in humans.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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