Psittacosis

PurposeChlamydia psittaci infection in humans can lead to serious clinical manifestations, including severe pneumonia, adult respiratory distress syndrome, and, rarely, death. Implementation of metagenomic next-generation sequencing (mNGS) gives a promising new tool for diagnosis. The clinical spectrum of severe psittacosis pneumonia is described to provide physicians with a better understanding and to highlight the rarity and severity of severe psittacosis pneumonia.MethodsNine cases of severe psittacosis pneumonia were diagnosed using mNGS. Retrospective analysis of the data on disease progression, new diagnosis tool, treatments, and outcomes, and the findings were summarised.ResultsFrequent symptoms included chills and remittent fever (100%), cough and hypodynamia (100%), and headache and myalgia (77.8%). All patients were severe psittacosis pneumonia developed respiratory failure, accompanied by sepsis in 6/9 patients. mNGS takes 48-72 h to provide the results, and help to identify diagnosis of psittacosis. Laboratory data showed normal or slightly increased leucocytes, neutrophils, and procalcitonin but high C-reactive protein levels. Computed tomography revealed air-space consolidation and ground-glass opacity, which began in the upper lobe of one lung, and spread to both lungs, along with miliary, nodular, or consolidated shadows. One patient died because of secondary infection with Klebsiella pneumoniae, while the other eight patients experienced complete recoveries.ConclusionsThe use of mNGS can improve accuracy and reduce the delay in diagnosis of psittacosis. Severe psittacosis pneumonia responds well to the timely use of appropriate antibiotics.

BackgroundPsittacosis outbreak investigations require rapid identification of cases in order to trace possible sources and perform public health risk assessments. In recent outbreaks in the Netherlands, such investigations were hampered by the non-specificity of laboratory testing methods to identify human Chlamydia psittaci infections.MethodA systematic search of PubMed and Scopus databases of literature published between 01 January, 1986 and 03 July, 2017 was done to find best practices of laboratory-testing methods used in psittacosis outbreaks of two or more human cases. Reference lists of included articles were hand searched to identify additional articles.ResultsThirty-seven eligible articles were identified, describing 44 human psittacosis outbreaks in 12 countries. Laboratory tests performed were PCR (with various targets), serologic tests (complement binding reactions, ELISA's, immunofluorescence tests and immuno-peroxidase tests) and culture, in various combinations. The literature provided no 'gold standard' laboratory testing strategy to identify recent human C. psittaci infections. In most psittacosis outbreaks, for a considerable number of cases (or tested individuals in an exposed cohort), C. psittaci infection could not be confirmed, nor excluded as causative pathogen. None of the testing strategies was found to be suitable for (nearly) full case finding.ConclusionPCR enables rapid identification of human psittacosis patients and helps source finding by genotyping but has the disadvantage that sensitivity is high only in the acute phase. In outbreak situations, there is often a time delay and therefore, there is a need for new serologic testing methods next to PCR, with good specificity and sensitivity. Moreover, serum is easier to collect than the preferred diagnostic materials for PCR. A serologic test that can reliably confirm infection status without the necessity of convalescent serum sampling would enhance case finding, source tracing, identification of risk factors and assessment of burden of disease in various settings.

The recognition of genital chlamydial infection as an important public health problem was made first by the recognition of its role in acute clinical syndromes, as well as in serious reproductive and ocular complications, and secondly by our awareness of its prevalence when diagnostic tests became widely accessible. The recent availability of effective single dose oral antimicrobial therapy and sensitive molecular amplification tests that allow the use of noninvasive specimens for diagnosis and screening is expected to have a major impact in reducing the prevalence of disease in the next decade. Clinical manifestations associated with Chlamydia pneumoniae infection continue to emerge beyond respiratory illness. In particular, its association with atherosclerosis deserves further investigation. Chlamydia pecorum, a pathogen of ruminants, was recently recognized as a new species. The continued application of molecular techniques will likely elucidate an expanding role for chlamydiae in human and animal diseases, delineate the phylogenetic relationships among chlamydial species and within the eubacteria domain, and provide tools for detection and control of chlamydial infections.

Background and objectiveChlamydia psittaci and Legionella pneumophila are common atypical pathogens that cause severe community-acquired pneumonia (CAP). This study aimed to compare the clinical features and outcomes of Chlamydia psittaci pneumonia (CPP) and Legionella pneumophila pneumonia (LPP) identified using next-generation sequencing (NGS) for accurate identification.MethodsThis retrospective study included 68 patients with CPP and 42 patients with LPP. All cases were confirmed by metagenomic or targeted next-generation sequencing (mNGS/tNGS) of bronchoalveolar lavage fluid, serum, or sputum samples.ResultsPatients with LPP had a higher prevalence of diabetes and were predominantly male. Poultry contact was common in CPP (64.7% vs. 14.3%), whereas recent travel was associated with LPP (47.6% vs. 2.9%). LPP presented with increased extrapulmonary symptoms. Inflammatory marker levels were higher in LPP, including leukocytosis, neutrophilia, C-reactive protein, and procalcitonin (all p ConclusionLPP demonstrated greater initial clinical and laboratory severity compared to CPP. Under NGS-guided targeted therapy, both groups achieved comparable outcomes. The observational finding that both pathogens respond to azithromycin and cause severe disease when left undetected underscore the value of guideline-recommended β-lactams/macrolide combination therapy in CAP settings, particularly where these intracellular pathogens remain undiagnosed without NGS.