Legionellosis and Paving Machine | CDC EID

EID Journal Home > Volume 16, Number 9–September 2010

Volume 16, Number 9–September 2010
Research
Legionellosis Outbreak Associated with Asphalt Paving Machine, Spain, 2009
Mireia Coscollá , José Fenollar, Isabel Escribano, and Fernando González-Candelas
Author affiliations: Universidad de Valencia/Instituto Cavanilles de Biodiversidad y Biología Evolutiva, Valencia, Spain (M. Coscollá, F. González-Candelas); Centro de Investigación Biomédica en Red en Epidemiología y Salud Pública, Barcelona, Spain (M. Coscollá, F. González-Candelas); Swiss Tropical and Public Health Institute, Basel, Switzerland (M. Coscollá); Centro Salud Pública, Alcoi, Spain (J. Fenollar); and Hospital Virgen de los Llirios, Alcoi (I. Escribano)

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Abstract
From 1999 through 2005 in Alcoi, Spain, incidence of legionellosis was continually high. Over the next 4 years, incidence was lower, but an increase in July 2009 led health authorities to declare an epidemic outbreak. A molecular epidemiology investigation showed that the allelic profiles for all Legionella pneumophila samples from the 2009 outbreak patients were the same, thus pointing to a common genetic origin for their infections, and that they were identical to that of the organism that had caused the previous outbreaks. Spatial-temporal and sequence-based typing analyses indicated a milling machine used in street asphalt repaving and its water tank as the most likely sources. As opposed to other machines used for street cleaning, the responsible milling machine used water from a natural spring. When the operation of this machine was prohibited and cleaning measures were adopted, infections ceased.
Legionella pneumophila (1) is a gram-negative bacterium identified as the causative agent of an outbreak of pneumonia that occurred in a Philadelphia hotel during a Legionnaires' convention in 1977 (2). This outbreak affected 221 persons, of whom 34 died (2). Although other Legionella spp. can cause the disease, L. pneumophila is responsible for 90% of the cases of legionellosis globally. This species is 1 of the most common causes of community-acquired bacterial pneumonia (3–7) and the second most common cause of severe pneumonia (8).

L. pneumophila is a waterborne bacterium that can cause respiratory illness when a susceptible person inhales contaminated, aerosolized water. Infection sources are usually human-made aquatic habitats, such as potable water supplies (9), whirlpool spas (10), cooling towers (11,12), showers (13), decorative fountains (14,15), and hoses (16).

Molecular epidemiologic analyses of L. pneumophila usually compare sequence-based typing patterns from bacterial cultures derived from putative environmental sources with L. pneumophila cultures from patients' sputum samples. This approach consists of amplifying and sequencing internal fragments of 7 loci and assigns a number to the different alleles derived from each locus (17,18). The combination of allele variants for each locus determines the allelic profile that characterizes each sample. Isolation of L. pneumophila from respiratory secretions on selective media is fastidious and time-consuming. Moreover, some L. pneumophila strains may be viable but cannot be cultured (19); despite high specificity of this method, culturing L. pneumophila is not efficient (20,21). Therefore, the efficiency of sequence-based typing of L. pneumophila can be improved by direct amplification and sequencing of DNA extracted from uncultured respiratory samples (22).

Since 2000, a specific epidemiologic surveillance system for legionellosis has been in place in the Hospital Virgen de los Llirios in Alcoi, Spain. Every patient with signs of pneumonia is scanned by chest radiography and urine analysis for L. pneumophila serogroup 1 antigen. This surveillance system enables early detection and better prognosis for L. pneumophila–infected patients. It also helps distinguish between sporadic cases and outbreaks, thus enabling early start of epidemiologic investigations.

At the end of July 2009, the epidemiology surveillance system detected 2 cases of legionellosis in persons who had stayed in Alcoi, Spain, during their incubation periods. New cases appeared during the first week of August, at which time an epidemic outbreak was declared and an epidemiologic investigation was started. Patients in the outbreak were questioned about clinical and personal aspects. Spatial–temporal analysis was used to identify the most likely areas of exposure for infection. L. pneumophila was isolated from environmental samples obtained in those areas. Because the usual facilities and municipal water systems associated with risk were not contaminated, other facilities not previously linked to legionellosis outbreaks were considered. To verify the common genetic origin of the outbreak and its environmental source, we performed an epidemiologic molecular analysis using sequence-based typing for clinical and environmental samples.

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