In February, 2012, a 52-year-old Caucasian man with no underlying disease (but a cigarette smoker) was admitted to the intensive care unit of a Dutch hospital, with high fever, shortness of breath, electrolyte imbalance, diarrhea, and neurological symptoms. Chest radiography showed areas of consolidation in both his lungs and confirmed the diagnosis of pneumonia. He was treated with intravenous ciprofloxacin (400mg daily), intravenous cefuroxime (6 days, 1000mg every 8 hours), and doxycycline oral (3 days, 200mg twice daily). Following negative results for both a L. pneumophila urinary antigen test, and a polymerase chain reaction (PCR) assay that targeted the 5S ribosomal deoxyribonucleic acid (DNA) gene performed on a sputum sample (DNA extraction by NucliSENS  easyMAG , bioMerieux, Durham, USA), treatment with intravenous ciprofloxacin was stopped after 4 days. Two days later, both PCR and culture of a bronchial lavage sample were found positive for L. pneumophila (serogroup 3), and the treatment with intravenous ciprofloxacin was continued for another 10 days. The patient left the intensive care unit after 13 days, recovered and left the hospital after 23 days.
In accordance with the National Legionella Outbreak Detection Programme that was installed in the Netherlands in 2002, an investigation was performed to find the source of infection. During the source investigation, two potential sources were identified: (1) the house of the patient where he had used taps and shower, and (2) the metal processing company where he worked and was exposed to water-based cutting fluids, and a pressure test pump (Figure 1) that uses water to evaluate the quality of the produced industrial iron molds. With this manually operated pressure test pump, molds are tested for leakages by pushing water through the mold with increasing air pressure. When a leak is present, respirable water aerosols are sprayed around by the pump, and the pressure drops. Samples were taken from the patient's home (taps and shower), from the cutting-fluids and water reservoir of the pump at the company. All nine samples from his home were negative, but one of the five samples from the company was positive for L. pneumophila. The sample from the water reservoir of the pressure test pump contained 9 8x103 colony forming units/L. Both L. pneumophila serogroup 1 and serogroup 3 were isolated from this sample. Sequence-based typing (SBT) showed the same sequence type (ST93) for both the clinical and environmental L. pneumophila serogroup 3 strains. This sequence type was previously reported for only 29 clinical and 15 environmental isolates according to the European Working Group for Legionella Infections SBT database which contains sequence types of over 6600 L. pneumophila strains. The high pressure pump was dismantled and thoroughly cleaned and rinsed several times, and control measures and changes in the working procedure were implemented. Employees are now required to wear filtering facepiece 2 respirator masks when operating the pump and the water reservoir is emptied and dried after every use. No other cases of LD related to this company were reported among the other employees.