High-dose intravenous methylprednisolone for hantavirus cardiopulmonary syndrome in Chile: a double-blind, randomized controlled clinical trial.

BACKGROUND: Andes virus (ANDV)-related hantavirus cardiopulmonary syndrome (HCPS) has a 35% case fatality rate in Chile and no specific treatment. In an immunomodulatory approach, we evaluated the efficacy of intravenous methylprednisolone for HCPS treatment, through a parallel-group, placebo-controlled clinical trial. METHODS: Patients aged >2 years, with confirmed or suspected HCPS in cardiopulmonary stage, admitted to any of 13 study sites in Chile, were randomized by study center in blocks of 4 with a 1:1 allocation and assigned through sequentially numbered envelopes to receive placebo or methylprednisolone 16 mg/kg/day (≤1000 mg) for 3 days. All personnel remained blinded except the local pharmacist. Infection was confirmed by immunoglobulin M antibodies or ANDV RNA in blood. The composite primary endpoint was death, partial pressure of arterial oxygen/fraction of inspired oxygen ratio ≤55, cardiac index ≤2.2, or ventricular tachycardia or fibrillation within 28 days. Safety endpoints included the number of serious adverse events (SAEs) and quantification of viral RNA in blood. Analysis was by intention to treat. RESULTS: Infection was confirmed in 60 of 66 (91%) enrollees. Fifteen of 30 placebo-treated patients and 11 of 30 methylprednisolone-treated patients progressed to the primary endpoint (P = .43). We observed no significant difference in mortality between treatment groups (P = .41). There was a trend toward more severe disease in placebo recipients at entry. More subjects in the placebo group experienced SAEs (P = .02). There were no SAEs clearly related to methylprednisolone administration, and methylprednisolone did not increase viral load. CONCLUSIONS: Although methylprednisolone appears to be safe, it did not provide significant clinical benefit to patients. Our results do not support the use of methylprednisolone for HCPS. CLINICAL TRIALS REGISTRATION: NCT00128180.

Dynamics of clinical and environmental Vibrio parahaemolyticus strains during seafood-related summer diarrhea outbreaks in southern Chile.

Seafood consumption-related diarrhea became prevalent in Chile when the pandemic strain of Vibrio parahaemolyticus serotype O3:K6 reached a region in the south of Chile (Region de los Lagos) where approximately 80% of the country's seafood is produced. In spite of the large outbreaks of clinical infection, the load of V. parahaemolyticus in shellfish of this region is relatively low. The pandemic strain constitutes a small but relatively stable group of a diverse V. parahaemolyticus population, composed of at least 28 genetic groups. Outbreaks in Region de los Lagos began in 2004 and reached a peak in 2005 with 3,725 clinical cases, all associated with the pandemic strain. After 2005, reported cases steadily decreased to a total of 477 cases in 2007. At that time, 40% of the clinical cases were associated with a pandemic strain of a different serotype (O3:K59), and 27% were related to V. parahaemolyticus isolates unrelated to the pandemic strain. In the results published here, we report that in the summer of 2008, when reported cases unexpectedly increased from 477 to 1,143, 98% of the clinical cases were associated with the pandemic strain serotype O3:K6, a change from 2007. Nevertheless, in 2009, when clinical cases decreased to 441, only 64% were related to the pandemic strain; the remaining cases were related to a nonpandemic tdh- and trh-negative strain first identified in shellfish in 2006. Overall, our observations indicate that the pandemic strain has become a relatively stable subpopulation and that when the number of diarrhea cases related to the pandemic strain is low, previously undetected V. parahaemolyticus pathogenic strains become evident.

Vibrio parahaemolyticus strains isolated during investigation of the summer 2006 seafood related diarrhea outbreaks in two regions of Chile.

Nine hundred cases of seafood related diarrhea were reported in the region of Puerto Montt, Chile during the austral summer of 2006. This is the continuation of the large outbreaks associated with the consumption of seafood containing the Vibrio parahaemolyticus serovar O3:K6 pandemic clonal group that arose last decade in Chile. The initial outbreaks occurred during the summer of 1998 in Antofagasta (23 degrees 39'S 70 degrees 24'W). Subsequently, outbreaks there were rare, but since 2004 outbreaks have been frequent farther south in Puerto Montt (41 degrees 29'S 72 degrees 24'W). The large outbreaks in Puerto Montt and their rarity in Antofagasta is atypical because the seawater temperature at Puerto Montt is 5 degrees C lower than at Antofagasta and the presence of V. parahaemolyticus in seafood has been associated with higher water temperatures. To better understand the role of seafood in outbreak occurrences in these regions, we analyzed the V. parahaemolyticus populations in clinical cases and shellfish from Puerto Montt during diarrhea outbreaks in 2006 and in shellfish from Antofagasta, where no cases were observed. Enrichment culture from shellfish yielded no V. parahaemolyticus from samples from the north, but its presence was detected in 80% of the samples from the south. Grouping of the V. parahaemolyticus isolates by the fragment restriction pattern of their DNA showed that all pathogenic (tdh+) isolates obtained from Puerto Montt shellfish corresponded to the serovar O3:K6 South East Asian pandemic clone, while the non-pathogenic (tdh-) isolates corresponded to at least six discrete groups. The possible causes for the disappearance of the pandemic strain from the north and its persistence in the south are discussed.

A non-randomized multicentre trial of human immune plasma for treatment of hantavirus cardiopulmonary syndrome caused by Andes virus.

BACKGROUND: In Chile, Andes virus (ANDV) is the sole aetiological agent of hantavirus cardiopulmonary syndrome (HCPS) with mean annual incidence of 55 cases, 32% case fatality rate (CFR) and no specific treatment. Neutralizing antibody (NAb) titres at hospital admission correlate inversely with HCPS severity. We designed an open trial to explore safety and efficacy and evaluate pharmacokinetics of immune plasma as a treatment strategy for this disease. METHODS: We performed plasmapheresis on donors at least 6 months after HCPS and measured NAb titres through a focus-reduction neutralization test. Subjects admitted to 10 study sites with suspected/confirmed HCPS were eligible for treatment with immune plasma by intravenous infusion at an ANDV NAb dose of 5,000 U/kg. HCPS was confirmed through immunoglobulin M serology or reverse transcriptase-PCR. The main outcome was mortality within 30 days. RESULTS: From 2008-2012, we enrolled and treated 32 cases and confirmed HCPS in 29. CFR of hantavirus plasma-treated cases was 4/29 (14%); CFR of non-treated cases in the same period in Chile was 63/199 (32%; P=0.049, OR=0.35, CI=0.12, 0.99); CFR of non-treated cases at the same study sites between 2005-2012 was 18/66 (27%; (P=0.15, OR=0.43, CI=0.14, 1.34) and CFR in a previous methylprednisolone treatment study was 20/60 (33%; P=0.052, OR=0.32, CI=0.10, 1.00). We detected no serious adverse events associated to plasma infusion. Plasma NAb titres reached in recipients were variable and viral load remained stable. CONCLUSIONS: Human ANDV immune plasma infusion appears safe for HCPS. We observed a decrease in CFR in treated cases with borderline significance that will require further studies for confirmation.

Vibrio parahaemolyticus in shellfish and clinical samples during two large epidemics of diarrhoea in southern Chile.

Large epidemics of diarrhoea associated with seafood consumption and Vibrio parahaemolyticus occurred during the austral summers of 2004 and 2005 in the environs of Puerto Montt, Chile (41 degrees 29'S 72 degrees 24'W). There are no reports of V. parahaemolyticus infections before 2004 in this region, their absence being explained by the low ocean temperatures which seldom reach 16 degrees C. We analysed V. parahaemolyticus obtained from shellfish and clinical samples during epidemics. Isolates were examined using conventional protocols and an improved method for restriction enzyme analysis using total bacterial DNA which permits direct genome restriction enzyme analysis by conventional gel electrophoresis (DGREA) with a similar discrimination index as restriction fragment length polymorphism-pulsed field gel electrophoresis (RFLP-PFGE). Analysis of clinical samples showed that the epidemics were caused by the V. parahaemolyticus O3:K6 pandemic clonal group. On the other hand, analysis of shellfish samples during both epidemics showed that 53% contained V. parahaemolyticus (3-93 g(-1)). Detailed analysis of 50 positive shellfish samples showed that only three contained detectable levels of the pandemic clone. Most V. parahaemolyticus isolates obtained from shellfish corresponded to non-pandemic clones differentiated into 14 groups by DGREA. In summary, the causative agent during epidemics was only a minor component of a small but diverse population of V. parahaemolyticus in shellfish.