Impact of routine systematic polymerase chain reaction testing on case finding for Legionnaires' disease: a pre-post comparison study.

BACKGROUND: Legionnaires' disease cannot be clinically or radiographically distinguished from other causes of pneumonia, and specific tests are required to make the diagnosis. Currently, testing occurs erratically and, instead, clinicians rely on empiric treatment strategies and ignore public health implications of the diagnosis. We aimed to measure the increase in case detection of Legionnaires' disease following the introduction of routine polymerase chain reaction (PCR) testing of respiratory specimens. PCR is the most sensitive diagnostic tool for Legionnaires' disease. METHODS: In a quasi-experimental study in Christchurch, New Zealand, we compared the number of cases of Legionnaires' disease requiring hospitalization diagnosed during a 2-year period before the introduction of a routine PCR testing strategy (November 2008-October 2010) with a similar period after the introduction (November 2010-October 2012). With this testing strategy, all respiratory specimens from hospitalized patients with pneumonia sent to the region's sole tertiary-level laboratory were tested for Legionella by PCR, whether requested or not. RESULTS: During November 2008 to October 2010, there were 22 cases of Legionnaires' disease compared with 92 during November 2010 to October 2012. Of 1834 samples tested since November 2010, 1 in 20 was positive, increasing to 1 in 9 during peak Legionella season (November to January). Increasing bacterial load was associated with increasing disease severity. CONCLUSIONS: In our region, the burden of Legionnaires' disease is much greater than was previously recognized. Routine PCR testing provides results within a clinically relevant time frame and enables improved characterization of the regional epidemiology of Legionnaires' disease.

The burden of Legionnaires' disease in New Zealand (LegiNZ): a national surveillance study.

BACKGROUND: Legionnaires' disease is under-diagnosed because of inconsistent use of diagnostic tests and uncertainty about whom to test. We assessed the increase in case detection following large-scale introduction of routine PCR testing of respiratory specimens in New Zealand. METHODS: LegiNZ was a national surveillance study done over 1-year in which active case-finding was used to maximise the identification of cases of Legionnaires' disease in hospitals. Respiratory specimens from patients of any age with pneumonia, who could provide an eligible lower respiratory specimen, admitted to one of 20 participating hospitals, covering a catchment area of 96% of New Zealand's population, were routinely tested for legionella by PCR. Additional cases of Legionnaires' disease in hospital were identified through mandatory notification. FINDINGS: Between May 21, 2015, and May 20, 2016, 5622 eligible specimens from 4862 patients were tested by PCR. From these, 197 cases of Legionnaires' disease were detected. An additional 41 cases were identified from notification data, giving 238 cases requiring hospitalisation. The overall incidence of Legionnaires' disease cases in hospital in the study area was 5·4 per 100 000 people per year, and Legionella longbeachae was the predominant cause, found in 150 (63%) of 238 cases. INTERPRETATION: The rate of notified disease during the study period was three-times the average over the preceding 3 years. Active case-finding through systematic PCR testing better clarified the regional epidemiology of Legionnaires' disease and uncovered an otherwise hidden burden of disease. These data inform local Legionnaires' disease testing strategies, allow targeted antibiotic therapy, and help identify outbreaks and effective prevention strategies. The same approach might have similar benefits if applied elsewhere in the world. FUNDING: Health Research Council of New Zealand.

Characteristics of Streptococcus pseudopneumoniae isolated from purulent sputum samples.

Streptococcus pseudopneumoniae is a recently described streptococcus that is phenotypically and genetically distinct from Streptococcus pneumoniae and other viridans streptococci. Key characteristics of S. pseudopneumoniae are the absence of a pneumococcal capsule, insolubility in bile, resistance or indeterminate susceptibility to optochin when incubated in 5% CO2 but susceptibility to optochin when incubated in ambient air, and a positive reaction with the AccuProbe DNA probe hybridization test. The clinical importance of this bacterium is currently unknown. We report the characteristics and associated clinical data of 35 strains of S. pseudopneumoniae isolated from sputum samples from 33 patients. All isolates produced a positive result with the NOW S. pneumoniae antigen test (Binax, Inc.). No isolate was resistant to penicillin, but 60% were resistant to erythromycin and 77% were resistant to tetracycline. All patients had lower respiratory tract symptoms, 79% had chronic obstructive pulmonary disease (COPD), and 33% had chest radiographic infiltrates. Compared with matched control patients who had Streptococcus pneumoniae isolated from sputum, patients with S. pseudopneumoniae infection were more likely to have a history of COPD (odds ratio [OR], 5.0; 95% confidence interval [CI], 1.67 to 20.11) or exacerbation of COPD (OR, 6.5; 95% CI, 2.61 to 16.20). Further research is needed to better characterize the epidemiology of S. pseudopneumoniae colonization and the role of S. pseudopneumoniae in COPD and other diseases.