Chlamydia psittaci Pneumonia in a patient with motor neuron disease: a case report.

BACKGROUND: Motor neuron disease (MND) is a fatal neurodegenerative disorder that leads to progressive loss of motor neurons. Chlamydia psittaci (C. psittaci) is a rare etiology of community-acquired pneumonia characterized primarily by respiratory distress. We reported a case of C. psittaci pneumonia complicated with motor neuron disease (MND). CASE PRESENTATION: A 74-year-old male was referred to the Shaoxing Second Hospital at January, 2022 complaining of fever and fatigue for 2 days. The patient was diagnosed of MND with flail arm syndrome 1 year ago. The metagenomic next-generation sequencing (mNGS) of sputum obtained through bedside fiberoptic bronchoscopy showed C. psittaci infection. Then doxycycline was administrated and bedside fiberoptic bronchoscopy was performed to assist with sputum excretion. Computed Tomography (CT) and fiberoptic bronchoscopy revealed a significant decrease in sputum production. On day 24 after admission, the patient was discharged with slight dyspnea, limited exercise tolerance. One month later after discharge, the patient reported normal respiratory function, and chest CT showed significant absorption of sputum. CONCLUSIONS: The mNGS combined with bedside fiberoptic bronchoscopy could timely detect C. psittaci infection. Bedside fiberoptic bronchoscopy along with antibiotic therapy may be effective for C. psittaci treatment.

A pediatric case of Chlamydia psittaci caused severe Acute Respiratory Distress Syndrome (ARDS) in Italy.

BACKGROUND: This case of psittacosis in children, is the first described in literature, in Italy. This respiratory infection can be transmitted to humans from the inhalation of respiratory secretions, feces and plumage aerosol of infected birds (and other animals). Usually it can have an asymptomatic or paucisymptomatic course, and the onset is often flu-like, but in this case the child risked his life for a severe respiratory failure. This report is unique because in children psittacosis is rare, and always misdiagnosed, or could cause a delayed diagnosis because of lack of awareness among the paediatricians and physicians. Furthermore, psittacosis enters a differential diagnosis with SARS-COV2 infection because both diseases may determine dyspnea and atypical pneumonia, up to acute respiratory failure. CASE PRESENTATION: This clinical case talks about a three-and-a-half-year-old male child affected by psittacosis (or ornithosis), with severe dyspnea and systemic symptoms who required oro-tracheal intubation for acute respiratory failure. The child had slept in a room at home, with some recently bought parrots affected by psittacosis. Initially the child was treated with empiric antibiotic therapy (i.v.ceftriaxone and teicoplanin), but after having isolated the DNA of the germ "Chlamydia psittaci" in both serological and through bronchoalveolar lavage (BAL), he was treated with targeted antibiotic therapy: tetracyclines (doxicillin). CONCLUSIONS: Psittacosis is an extremely contagious disease, caused by an intracellular germ, called "Chlamydia psittaci", a Gram-negative bacterium, transmitted to humans in particular by infected birds, responsible for atypical pneumonia, with acute and chronic respiratory symptoms, sometimes with multi-organ failure and disseminated intravascular coagulation. Even if it is a rare respiratory disease among children, a good doctor must think about psittacosis as cause of respiratory symptoms (and not only flu or SARS-COV2), above all through a correct medical history, in order to provide a targeted antibiotic therapy. An interesting case of psittacosis in a child is being reported here, which has been treated successfully with doxycillin.

Psittacosis caused severe community-acquired pneumonia accompanied by acute hypoxic respiratory failure: a multicenter retrospective cohort study from China.

INTRODUCTION: Psittacosis can cause severe community-acquired pneumonia (CAP). The clinical manifestations of psittacosis range from subclinical to fulminant psittacosis with multi-organ failure. It is essential to summarize the clinical characteristic of patients with severe psittacosis accompanied by acute hypoxic respiratory failure (AHRF). METHODS: This retrospective study included patients with severe psittacosis caused CAP accompanied by AHRF from 19 tertiary hospitals of China. We recorded the clinical data, antimicrobial therapy, respiratory support, complications, and outcomes. Chlamydia psittaci was detected on the basis of metagenomic next-generation sequencing performed on bronchoalveolar lavage fluid samples. Patient outcomes were compared between the treatment methods. RESULTS: This study included 45 patients with severe CAP and AHRF caused by psittacosis from April 2018 to May 2021. The highest incidence of these infections was between September and April. There was a history of poultry contact in 64.4% of the patients. The median PaO2/FiO2 of the patients was 119.8 (interquartile range, 73.2 to 183.6) mmHg. Four of 45 patients (8.9%) died in the ICU, and the median ICU duration was 12 days (interquartile range, 8 to 21) days. There were no significant differences between patients treated with fluoroquinolone initially and continued after the diagnosis, fluoroquinolone initially followed by tetracycline, and fluoroquinolone combined with tetracycline. CONCLUSION: Psittacosis caused severe CAP seems not rare, especially in the patients with the history of exposure to poultry or birds. Empirical treatment that covers atypical pathogens may benefit such patients, which fluoroquinolones might be considered as an alternative.

Case report: Clinical characteristics of two cases of pneumonia caused with different strains of Chlamydia psittaci.

Background: With the development of metagenomic sequencing technologies, more and more cases of pneumonia caused with Chlamydia psittaci (C. psittaci) have been reported. However, it remains unknown about the characteristics of patients with pneumonia caused by different strains of C. psittaci. Here, we shared the clinical characteristics of two cases of pneumonia caused with C. psittaci strains SZ18-2 and SZ15 which were rarely identified in humans. Case presentation: Case 1: A 69-year-old male farmer who fed ducks presented to hospital for cough, diarrhea and lethargy with the temperature of 39.8°C. Case 2: A 48-year-old male worker who slaughtered ducks was transferred to hospital for high fever, cough, myalgia, diarrhea and loss of appetite. Both patients did not take any protective measures (wearing face masks or gloves) while processing ducks. C. psittaci pneumonia was diagnosed by metagenomic next-generation sequencing and polymerase chain reaction. After treatment with doxycycline and azithromycin individually, they recovered well and discharged from hospital. Through OmpA sequencing, two different strains of SZ18-2 and SZ15 were identified in case 1 and case 2, respectively. Conclusions: Patients infected with different strains of C. psittaci may own different clinical manifestations. C. psittaci infection should be suspected when pneumonia appears, accompanied by digestive symptoms and multiple organ dysfunction, especially under the exposure of specific birds.

Clinical features of psittacosis in 46 Chinese patients.

BACKGROUND: Psittacosis is a relatively uncommon cause of community-acquired pneumonia, often leading to diagnostic difficulty. METHODS: A retrospective study was conducted on the clinical features of psittacosis patients in China. Forty-six cases of Chlamydophila psittaci infection with atypical pneumonia of varying severity in the last two years were described retrospectively. RESULTS: Fever, relative bradycardia, and other systemic upsets were the main clinical presentation. The most common radiographic abnormality was segmental or lobar shadowing or consolidation. The total white cell counts were usually normal or slightly increased. The concentration of creatine kinase, C reactive protein, and lactic dehydrogenase increased, while albumin decreased remarkably. These cases exhibited good recovery after being treated with tetracycline or quinolone antibiotics. CONCLUSION: These features may help differentiate psittacosis from other traditional bacterial pneumonia. However, they do not provide a definitive diagnosis. Psittacosis diagnosis must perform the whole-genome sequencing for Chlamydophila psittaci in respiratory, blood, or sputum specimens. Increased awareness of psittacosis can shorten diagnostic delays and improve patient outcomes.

Diagnosis and Analysis of Clinical Characteristics of Chlamydia psittaci Pneumonia.

Objective: We assessed the clinical characteristics of three patients with Chlamydia psittaci-associated pneumonia. Methods: Clinical data for three patients with C. psittaci-associated pneumonia admitted to our hospital from June 2020 to December 2020 were retrospectively analyzed, and the diagnosis, clinical features, and treatment of the disease are summarized. Results: Fever, headache, and fatigue were the main symptoms in all three patients, whereas local respiratory symptoms such as cough and expectoration were not obvious. Not all patients had a definite contact history with poultry and birds. Chest computed tomography (CT) showed inflammatory exudation, consolidation, and bronchial inflation signs on one side of the lungs, which progressed rapidly. Treatment with beta-amides did not result in positive clinical responses. Combined with clinical manifestations, the disease was confirmed by detection of C. psittaci nucleic acid sequences in alveolar lavage fluid and blood by metagenomic second-generation sequencing technology. Fever and malaise were rapidly relieved after the administration of moxifloxacin-based regimens and levels of infectious blood markers decreased; and the consolidation shadow on chest CT was gradually absorbed. Conclusion: Early application of metagenomic second-generation sequencing in patients with community-acquired pneumonia due to rare and complex pathogens that cannot be diagnosed by conventional tests and for whom empirical anti-infective therapy is ineffective is important for definitive diagnosis and selection of appropriate antibacterial drugs.

Severe pneumonia caused by Chlamydia psittaci: report of two cases and literature review.

INTRODUCTION: Chlamydia psittaci pneumonia is a zoonotic infectious disease caused by Chlamydia psittaci. Its clinical manifestations are nonspecific. Diagnosis of the disease is difficult. In recent years, next-generation sequencing has played an important role in pathogen detection. We report two cases with severe Chlamydia psittaci pneumonia confirmed by next-generation sequencing. CASE STUDY: The first case is that of a 50-year old man who presented with high fever for four days and cough with sputum for two days. The second case is that of a 57-year-old man who was admitted with high fever for one week, dyspnea and cough with sputum for four days. The second man worked at a chicken farm in the last two months. In both cases, the usual laboratory examination for pathogens detection was negative, and the initial anti-infectious therapy had limited effect. The bronchoalveolar lavage fluid of case 1 and the blood and sputum of case 2 were sent for next-generation sequencing which resulted in sequence reads of Chlamydia psittaci. Antibiotics were adjusted according to the diagnosis. RESULTS: The diagnosis of the two cases was confirmed by next-generation sequencing detecting Chlamydia psittaci, and the patients had positive results after treatment. CONCLUSIONS: The two cases suggest that next-generation sequencing could be used in early diagnosis of Chlamydia psittaci infection to initiate specific anti-infection therapy in time.

Clinical, radiological and pathological characteristics of moderate to fulminant psittacosis pneumonia.

BACKGROUND: Psittacosis pneumonia is a community-acquired pneumonia caused by Chlamydia psittaci. It is usually under-diagnosed due to its atypical clinical presentation and lack of routine laboratory tests. METHODS: To better understand the clinical features, 52 patients diagnosed with psittacosis pneumonia by metagenomic next-generation sequencing (mNGS) were enrolled in this study. The clinical, radiological and pathological characteristics were retrospectively analyzed. RESULTS: The onset of psittacosis pneumonia in this study occurred all year round, with a peak from December to January. Most of the patients were 51-80 years old. About 65.38% of patients had a history of exposure to poultry or parrots. Abnormalities of multiple clinical signals were detected in these patients. Elevated levels of neutrophil ratio, C-reactive protein, erythrocyte sedimentation rate, and procalcitonin were detected in most patients. Radiological evidence revealed air-space consolidation or ground-glass opacities in lungs of all patients, which is the typical feature of psittacosis pneumonia. In addition, hyperemia, swelling of bronchial mucosa, and bronchial patency were detected by bronchoscopy in all patients, and bronchial sub-mucosal edema, inflammatory cells infiltration and alveolar epithelial hyperplasia were identified in the bronchial mucosa and alveolar tissue. Beta-lactam antibiotics were administered for empirical treatment before mNGS in 17 patients but showed no improvement. The treatment was switched to doxycycline or moxifloxacin immediately since psittacosis pneumonia were suspected and confirmed by mNGS detection (within 48 hours). After receiving adjustment of treatment, 94.23% (49/52) of patients were cured successfully. CONCLUSIONS: In conclusion, mNGS may be a promising approach for clinical diagnosis of psittacosis. For patients with a history of exposure to birds, hyperpyrexia, nonproductive cough, multiple elevated inflammatory markers, and air-space consolidation in lung, psittacosis pneumonia should be considered, especially when beta-lactam antibiotics showed limited efficacy.

Atypical pneumonia caused by Chlamydia psittaci during the COVID-19 pandemic.

OBJECTIVES: Here, we retrospectively described the diagnosis and treatment of 32 cases diagnosed with Chlamydia psittaci pneumonia during the COVID-19 pandemic. METHODS: Clinical information was collected from all the patients. Reverse transcription-PCR and ELISAs were conducted for the detection of COVID-19 using nasal swabs and bronchoalveolar lavage fluid (BALF) samples. Metagenomic next-generation sequencing (mNGS) was performed for the identification of causative pathogens using BALF, peripheral blood and sputum samples. End-point PCR was performed to confirm the mNGS results. RESULTS: All 32 patients showed atypical pneumonia and had infection-like symptoms that were similar to COVID-19. Results of reverse transcription-PCR and ELISAs ruled out COVID-19 infection. mNGS identified C. psittaci as the suspected pathogen in these patients within 48 hours, which was validated by PCR, except for three blood samples. The sequence reads that covered fragments of C. psittaci genome were detected more often in BALF than in sputum or blood samples. All patients received doxycycline-based treatment regimens and showed favorable outcomes. CONCLUSION: This retrospective study, with the highest number of C. psittaci pneumonia enrolled cases in China so far, suggests that human psittacosis may be underdiagnosed and misdiagnosed clinically, especially in the midst of the COVID-19 pandemic.

[0ne case report of Chlamydia psittaci pneumonia].

This paper reported a case of severe Chlamydia psittaci pneumonia. The patient had a clear history of contact with sick poultry. The clinical manifestations were dry cough, fever and respiratory failure. Chest CT showed consolidation in the lower lobe of the right lung, and a small amount of exudative ground-glass opacity in the left lung. Chlamydia psittaci was detected in bronchoalveolar lavage fluid (BALF) by metagenomic assay. After treatment with antibiotics such as nitroimidazoles and carbapenems, the patient was discharged with a better health condition.

Successful Treatment of Severe Community-Acquired Pneumonia caused by Chlamydia Psittaci: a Case Report.

BACKGROUND: Community acquired pneumonia is a common and deadly condition, which remains a major cause of morbidity and mortality throughout the world. Chlamydia psittaci pneumonia is responsible for less than 5% of community-acquired pneumonia with a fatality rate of 1%. Nonetheless, it is underestimated due to low awareness of the disease and atypical clinical presentation in a majority of the cases. Metagenomic next-generation sequencing can help us diagnose and clarify the etiology in time. METHODS: We reported a case of an 85-year-old man who presented with intermittent fever and cough with wheezing for 4 days and did a review of related literature. RESULTS: The patient was admitted to our department due to severe CAP and multiple organ dysfunction. After admission, we applied an empirical antibiotic strategy, performed intubation and invasive ventilation, fluid resuscitation, vasoactive drugs and supportive care. On the third day of admission, metagenomic next-generation sequencing results of blood and bronchoalveolar lavage fluid suggested Chlamydia psittaci. We made a diagnosis of sever Chlamydia psittaci pneumonia and adjusted antibiotics to minocycline combined with azithromycin two days after admission. The patient was successfully cured with a good prognosis. CONCLUSIONS: Detecting the pathogen as early as possible and achieving accurate diagnosis are essential in infected patients. We can benefit from careful application of metagenomic next-generation sequencing.

0ne case report of Chlamydia psittaci pneumonia / 中华劳动卫生职业病杂志

This paper reported a case of severe Chlamydia psittaci pneumonia. The patient had a clear history of contact with sick poultry. The clinical manifestations were dry cough, fever and respiratory failure. Chest CT showed consolidation in the lower lobe of the right lung, and a small amount of exudative ground-glass opacity in the left lung. Chlamydia psittaci was detected in bronchoalveolar lavage fluid (BALF) by metagenomic assay. After treatment with antibiotics such as nitroimidazoles and carbapenems, the patient was discharged with a better health condition.

Pregnancy combined with severe pneumonia caused by Chlamydia psittaci infection - a case report.

OBJECTIVE: Chlamydia psittaci (Cps) feeds on gram-negative aerobic cells. Respiratory inhalation of Cps or close contact with infected animals can cause psittacosis in humans. Given its challengeable early diagnosis and rapid progression, misdiagnosis or improper antibacterial drugs may lead to multi-organ dysfunction with a high mortality. CASE REPORT: A pregnant woman at 29+1 weeks of gestational age had a fever. CT images of the chest showed lamellar consolidations in the inferior lobe of the right lung, light inflammation in the middle lobe of the right lung. Negative results were obtained from multiple times of blood and sputum culture. Next generation sequencing (NGS) results identified that Cps caused severe pneumonia, which was alleviated by specific antibiotic treatment. CONCLUSION: Cps can cause severe pneumonia in the pregnant woman and be cured through precise antibiotic treatment. NGS is efficient in the rapid identification of pathogens and accurate diagnosis when bacteriological culture fails.

[Clinical and imaging features of Chlamydia psittaci pneumonia: an analysis of 48 cases in China].

Objective: To explore the clinical characteristics, imaging findings, laboratory tests and treatment strategies for Chlamydia psittaci pneumonia. Methods: From January 1, 2019 to January 20, 2021, 48 cases of Psittacosis from 11 hospitals in China were diagnosed via metagenomic next-generation sequencing(mNGS). The data of all patients on occupational history, clinical manifestations, laboratory tests, chest computed tomography(CT)findings, treatment outcomes and prognosis were retrospectively analyzed. Results: Among the 48 patients, there were 29 males and 19 females, with a mean age of (57.1±10.3) years. Thirty patients had a confirmed history of exposure to poultry. The onset to admission interval was (6.5±3.2) days, and hospital stay was (12.4±4.8) days. Clinical manifestations included fever (100%, 48/48), relative bradycardia (71%, 34/48), cough (54.2%, 26/48), sputum (27.1%, 13/48), fatigue (16.7%, 8/48), headache and delirium (20.8%, 9/48), and gastrointestinal symptoms (16.7%, 8/48). Laboratory data showed that white blood cells were (8.0±3.8)×109/L, and the proportion of neutrophils increased in 44 patients. The level of C-reactive protein was (155.3±74.1)mg/L, and that of procalcitonin (PCT)in 59.5% of patients was more than 0.5 µg/L. Percentages of patients with increased lactate dehydrogenase and creatine kinase were 82.9% and 45.2%, respectively. Chest CT scans showed unilateral lung involvement in 34 cases(70.8%) and single lobe involvement in 27 cases(56.3%).The most common imaging change was consolidation, with 38 cases (79.2%) showing lobar consolidation. In terms of treatment, 25 patients were treated with fluoroquinolones alone, 6 patients with doxycycline alone, and 13 patients with combined treatment. The combined-treatment group and the doxycycline alone group were similar in the course of defervescence. The combined treatment group and the doxycycline alone group were both superior to the fluoroquinolones alone group. However, 11 patients were admitted to ICU, all of them received artificial ventilation, and 5 cases developed shock, and one died. Conclusions: Chlamydia psittaci pneumonia is an animal-derived infectious disease with unique features in clinical symptoms, laboratory tests and chest imaging. Appropriate treatment is able to significantly shorten the course of disease and improve the prognosis.

A case of chlamydia psittaci caused severe pneumonia and meningitis diagnosed by metagenome next-generation sequencing and clinical analysis: a case report and literature review.

BACKGROUND: Psittacosis, which is also known as parrot fever, is Chlamydia psittaci (C. psittaci) caused infectious disease. The clinical manifestations vary from asymptomatic infection to severe atypical pneumonia or even fatal meningitis. Early recognition of psittacosis is difficult because of its nonspecific clinical manifestations. Culture and gene probe techniques for C. psittaci are not available for routine clinical use, which makes the diagnosis difficult too. Although psittacosis has increasingly been recognized and reported in recent years, cure of severe pneumonia complicated with meningitis, with etiologic diagnosis aided by the use of metagenomic next-generation sequencing (mNGS), is still uncommon. So, it is necessary to report and review such potentially fatal case. CASE PRESENTATION: This report describes a 54-year-old woman with C. psittaci caused severe atypical pneumonia and meningitis. She presented with symptoms of fever, dry cough and dyspnea, accompanied by prominent headache. Her condition deteriorated rapidly to respiratory failure and lethargy under the treatment of empirical antibacterial agents, and was treated with invasive mechanical ventilation soon. She denied contact with birds, poultry or horses, but unbiased mNGS of both the bronchoalveolar lavage fluid (BALF) and the cerebrospinal fluid (CSF) identified sequence reads corresponding to C. psittaci infection, and there was no sequence read corresponding to other probable pathogens. Combined use of targeted antimicrobial agents of tetracyclines, macrolides and fluoroquinolones was carried out, and the patient's condition improved and she was discharged home 28 days later. Her status returned close to premorbid condition on day 60 of follow-up. CONCLUSIONS: When clinicians come across a patient with atypical pneumonia accompanied by symptoms of meningitis, psittacosis should be taken into consideration. mNGS is a promising detection method in such condition and is recommended.

Intranasal immunization with inactivated chlamydial elementary bodies formulated in VCG-chitosan nanoparticles induces robust immunity against intranasal Chlamydia psittaci challenge.

Vaccines based on live attenuated Chlamydia elementary bodies (EBs) can cause disease in vaccinated animals and the comparably safer inactivated whole EBs are only marginally protective. Recent studies show that a vaccine formulation comprising UV-inactivated EBs (EB) and appropriate mucosal delivery systems and/or adjuvants induced significant protective immunity. We tested the hypothesis that intranasal delivery of UV-inactivated C. psittaci EB formulated in Vibrio cholerae ghosts (VCG)-chitosan nanoparticles will induce protective immunity against intranasal challenge in SPF chickens. We first compared the impact of VCG and CpG adjuvants on protective immunity following IN mucosal and IM systemic delivery of EB formulated in chitosan hydrogel/microspheres. Immunologic analysis revealed that IN immunization in the presence of VCG induced higher levels of IFN-γ response than IM delivery or the CpG adjuvanted groups. Also, vaccine efficacy evaluation showed enhanced pharyngeal bacterial clearance and protection against lung lesions with the VCG adjuvanted vaccine formulation, thereby establishing the superior adjuvanticity of VCG over CpG. We next evaluated the impact of different concentrations of VCG on protective immunity following IN mucosal immunization. Interestingly, the adjuvanticity of VCG was concentration-dependent, since protective immunity induced following IN mucosal immunization showed dose-dependent immune responses and protection. These studies reveal that formulation of inactivated chlamydial antigens with adjuvants, such as VCG and chitosan increases their ability to induce protective immune responses against challenge.

Characterization and comparison of differentially expressed genes involved in Chlamydia psittaci persistent infection in vitro and in vivo.

Chlamydia psittaci is an obligate intracellular zoonotic pathogen that can enter a persistence state in host cells. While the exact pathogenesis is not well understood, this persistence state may play an important role in chronic Chlamydia disease. Here, we assess the effects of chlamydial persistence state in vitro and in vivo by transmission electron microscopy (TEM) and cDNA microarray assays. First, IFN-γ-induced C. psittaci persistence in HeLa cells resulted in the upregulation of 68 genes. These genes are involved in protein translation, carbohydrate metabolism, nucleotide metabolism, lipid metabolism and general stress. However, 109 genes were downregulated following persistent C. psittaci infection, many of which are involved in the TCA cycle, expression regulation and transcription, protein secretion, proteolysis and transport, membrane protein, presumed virulence factor, cell division and late expression. To further study differential gene expression of C. psittaci persistence in vivo, we established an experimentally tractable mouse model of C. psittaci persistence. The C. psittaci-infected mice were gavaged with either water or amoxicillin (amox), and the results indicated that the 20 mg/kg amox-exposed C. psittaci were viable but not infectious. Differentially expressed genes (DEGs) screened by cDNA microarray were detected, and interestingly, the results showed upregulation of three genes (euo, ahpC, prmC) and downregulation of five genes (pbp3, sucB_1, oppA_4, pmpH, ligA) in 20 mg/kg amox-exposed C. psittaci, which suggests that antibiotic treatment in vivo can induce chlamydial persistence state and lead to differential gene expression. However, the discrepancy on inducers between the two models requires more research to supplement. The results may help researchers better understand survival advantages during persistent infection and mechanisms influencing C. psittaci pathogenesis or evasion of the adaptive immune response.

Clinical Symptoms and Outcomes of Severe Pneumonia Caused by Chlamydia psittaci in Southwest China.

Here, we aimed to retrospectively analyze the clinical characteristics of 27 patients with severe pneumonia caused by Chlamydia psittaci between January 2019 and April 2021 in southwest China. To this end, we collected data on the exposure history, clinical symptoms, laboratory examination, imaging characteristics, evolution, etiology, treatment, and outcomes to suggest a better diagnosis and prevention system. Our results showed that a metagenomic next-generation sequencing test could provide early diagnosis. All patients were sensitive to quinolones and tetracyclines, and the recovery rate was relatively high. Overall, all patients were in critical condition with moderate to severe acute respiratory distress syndrome and shock. In conclusion, early diagnosis of pneumonia caused by C. psittaci depends on effective molecular testing, and most patients recover after treatment.