Necrotising fasciitis due to Vibrio cholerae non-O1/non-O139 after exposure to Austrian bathing sites
The study of Hirk et al. reports two cases of necrotising fasciitis of the lower leg due to non-toxigenic Vibrio cholera, both one day after swimming in two different ponds with 20 km distance between them, in the province of Lower Austria. Neither pond was registered in the European Union as a bathing site.
The study of Hirk et al. reports two cases of necrotising fasciitis of the lower leg due to non-toxigenic Vibrio cholera, both one day after swimming in two different ponds with 20 km distance between them, in the province of Lower Austria. Neither pond was registered in the European Union as a bathing site. Cases reported minor excoriation or skin trauma before swimming in these local ponds.
Case 1 was a 73-year-old obese woman with hypertonia and diabetes mellitus, and case 2 an 80-year-old man with medical history of ichthyosis cutis and several episodes of cellulitis. Both patients were hospitalised with symptoms of necrotising fasciitis on 18 July and 15 August 2015, respectively. Intraoperative swabs from both cases were positive for V. cholerae non-O1/non-0139, negative for cholera toxin gene ctx and positive for hemolysis genes hlyAand hlyB (tested by next generation sequencing). No other microbiological findings were reported. Case 1 was discharged in good clinical condition after 73 days of hospitalisation, but case 2 died after four months of hospitalisation.
Water samples from the two ponds tested positive (32 days and seven days after exposure of case 1 and case 2, respectively) for V. cholerae non-O1/non-O139 with most probable numbers of > 11,000 per 100 ml each. Both ponds were resampled two weeks later with similar results. On 17 and 18 August 2015, 90 of 175 Austrian officially registered EU bathing sites were tested for V. cholerae with the identification of seven positive bathing sites: Lake Neusiedl and six other bodies were positive to V. cholerae non-O1/non-O139.
The authors comment that other cases of V. cholerae non-O1/non-O139, reported with various clinical manifestations, but not necrotising fasciitis, have been linked to swimming in Lake Neusiedl, a saline steppe lake in eastern Austria. In addition, the authors discuss that these two necrotising fasciitis cases could be linked to the extreme weather conditions (heat wave and drought) during 2015 summer in Austria, which could have supported the growth of V. cholerae non-O1/non-O139 in these ponds.
This article reports two cases of necrotising fasciitis, a rare condition, each after bathing in one of two Austrian ponds. Clinical samples from human cases and water samples from these ponds tested positive to V. cholerae non-O1/non-O139. These are the first two cases reported as being infected by this pathogen in non-saline waters in Austria. The persistence of Vibrios in these ponds was demonstrated and could partly be explained by extreme weather conditions during the summer 2015, i.e. highest temperature in July and precipitation 20% below average of previous 30 years , which could stimulate the growth of this pathogen due to high temperature and nutrient concentration.
Some other studies have also analysed the presence of V. cholerae non-O1/non-O139 in the largest lake in Austria, Lake Neusiedl, which has a concentration of salt that is approximately one-twentieth of that of sea water . Kirschner et al. found a significant correlation between the presence of the pathogen and temperature (rho = 0.65; P < 0.001; n = 102), zooplankton biomass (rho = 0.43; P < 0.001; n = 100) and conductivity (rho = 0.33; P < 0.01; n = 102) . Schauer et al. found that the higher water and air temperatures jointly with being sheltered from the wind in the summer of 2012 led to a higher concentration of this pathogen in Lake Neusiedl . Likewise, climate change has been considered one possible factor increasing Vibrio growth in seawater due to an increase in sea surface temperature of bathing sites [5,6].
Previous travel-associated and autochthonous cases of infections due to V. cholerae non-O1/non-O139 have been reported in Austria [2,7]. Most of the 14 autochthonous reported cases in these publications were linked to Lake Neusiedl including five cases of diarrhoea, four cases of otitis media, two cases of otitis externa, one case with septicaemia, and one asymptomatic case.
Other Vibrio spp. (e.g. Vibrio vulnificus) have caused wound infections in patients with underlying conditions after bathing in salt water, such as the Baltic Sea . Vibrio vulnificus has been isolated in co-infections with V. cholerae non-O1/non-O139 from a patient with a wound infection .
The occurrence of two rare but very severe Vibrio cholerae non-O1/non-O139 skin infections followed by swimming in natural, non-saline ponds is notable and deserves further investigation. The persistence of Vibrios in these ponds, which are not considered as natural environments for these bacteria, suggests an external source of contamination through human faeces facilitated by favourable climate conditions. Further investigation of the Vibrio isolates and background environmental factors would be helpful to better understand this exceptional event and determine the most effective prevention and control options. For example, comparison of Vibrio isolates from humans and water samples using whole genome sequencing would help in assessing the relatedness of the bacteria in the two ponds as well as with human infections.
Determining possible options for preventing and mitigating the impact of this type of infection would require not only educational activities for at-risk groups  (i.e. individuals with skin trauma or excoriations and underlying immunosuppressive conditions) but also collaborative studies with environmental authorities so that the risk for Vibrio infections from non-saline bathing waters could be better assessed. Based on the Austrian study, 8% of tested official bathing sites were positive for Vibrio cholera non-O1/non-O139, which suggests a wider prevalence of this bacteria than previously thought. Prompt diagnosis of Vibrio spp. in patients with wound infections and reporting of exposure to natural (salt)waters is essential to ensure appropriate antibiotic therapy in the early treatment phase . Further testing is warranted to identify those water areas where these pathogens are growing and where people might become exposed , particularly focusing on non-salt water bathing sites where climate conditions may support the growth of this bacteria.
A tool has been developed by ECDC to assess the environmental suitability of vibrio blooms in coastal waters and is available on the E3 Geoportal.
Read the study: Necrotizing fasciitis due to Vibrio cholerae non-O1/non-O139 after exposure to Austrian bathing sites
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