Growth in Acanthamoeba sp. and antibiotic susceptibility of Legionella micdadei isolated from hot spring water samples

Pneumonia and pulmonary abscess due to Legionella micdadei in an immunocompromised patient

Introduction

Legionella micdadei are gram-negative bacilli living in soil and aquatic habitats. They are responsible for less than 10% of legionellosis, but have a propensity to affect people suffering from immunodeficiency. Lung cavitations may also occur in this population. Isolation of L. micdadei on clinical samples requires specific culture media that are not routinely used. Moreover, serologic methods and urinary assays are specific for Legionella pneumophila serogroup 1 (the most frequent serogroup isolated from clinical specimens), and lack sensitivity for diagnosing L. micdadei infection. As a consequence, this diagnosis is difficult to confirm.

Case report

We report here a severe case of community-acquired legionellosis due to L. micdadei, in a patient under immunosuppressive medications and high-dose corticosteroids for rheumatoid arthritis. The source of his infection was hypothesized to be his continuous positive airway pressure device, which was regularly cleaned with tap water instead of sterile water, thus potentially resulting in Legionella contamination.

Conclusions

L. micdadei must be considered as a possible cause of community-acquired severe pneumonia in case of immunodeficiency. For outpatients, advice concerning the cleaning of aerosols-generating devices at home must be emphasized.

Isolation of Legionella species from Noyu (unattended natural hot springs in mountains and fields) samples in Japan

In order to understand the habitation conditions of the bacteria of the genus Legionella in Noyu (unattended natural hot springs in mountains and fields) in Japan, isolation of Legionella spp. was attempted in the Noyu samples from 11 prefectures nationwide between May and September 2012, and the following results were obtained. Overall, Legionella spp. was isolated from 16 of 43 samples (37.2%). The species was isolated from the Hokkaido region to the Chugoku region but not from the Shikoku region to the Kyushu region. The number of bacteria detected was usually small, less than 5.0 × 10(1) CFU/100 ml, as found in 11 samples (68.8%), while counts of 10(2) or more to 10(3) or less CFU/100 ml were found in two samples (12.5%). Legionella pneumophila was the most commonly found strain, with 19 strains (90.5%) found, and was the dominant species. Regarding the serogrouping, four strains (21.1%) fell under group 1, the most common grouping, followed by three strains (15.8%) in group 3, two strains (10.5%) in group 5, etc. Moreover, the detected bacterial strains other than L. pneumophila included two strains (9.5%) of L. londiniensis. The temperature of the Noyu from which Legionella spp. was isolated was between 33.1°C and 41.5°C with a pH ranging from 5.2 to 8.1. The present report is the first report to clarify the habitation conditions of strains of Legionella spp. isolated from Noyu in Japan.

The first case of Legionella nagasakiensis isolation from hot spring water

In August, 2010, strain HYMO-6 was isolated from a sample of hot spring water in Aomori, Japan. The 16S rDNA sequences (1,496bp) of this strain (accession number: AB597175) had a similarity of less than 96.6% to other Legionella species, prompting us to hypothesize that this strain might be a novel species belonging to the genus Legionella. However, in March of 2011, it was became clear that the HYMO-6 strain (=JCM 17450 =KCTC 23560 =DSM 24727) was Legionella nagasakiensis CDC-1796-JAP-E(T) (=ATCC BAA-1557(T) =JCM 15315(T)). When this strain was cultured on BCYEα agar at 36°C for 7 d, no long cells were observed. The dominant fatty acids of strain HYMO-6 were 16:1ω7c (32.4%), and the DNA G+C content was 42.0 mol%.