Clinical features of psittacosis in 46 Chinese patients / Características clínicas de 46 pacientes con psittacitis China

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.(AU)

Antecedentes: La psitacosis es una causa relativamente poco común de neumonía adquirida en la comunidad, y a menudo conduce a dificultades diagnósticas.Métodos: Se realizó un estudio retrospectivo sobre las características clínicas de los pacientes con psitacosis en China, en el que se describen retrospectivamente 46 casos de infección por Chlamydia psittaci con neumonía atípica de gravedad variable en los últimos dos años.Resultados: La fiebre, la bradicardia relativa y otros trastornos sistémicos fueron la presentación clínica principal. La anomalía radiográfica más común fue el sombreado o consolidación segmentaria o lobular. Los recuentos totales de glóbulos blancos fueron generalmente normales o ligeramente aumentados. Las concentraciones de creatina quinasa, proteína C reactiva y deshidrogenasa láctica aumentaron, mientras que la albúmina disminuyó notablemente. Estos casos mostraron una buena recuperación después de ser tratados con antibióticos de tetraciclina o quinolona.Conclusión: Estas características pueden ayudar a diferenciar la psitacosis de otras neumonías bacterianas tradicionales. Sin embargo, no proporcionan un diagnóstico definitivo. El diagnóstico de psitacosis debe realizar la secuenciación del genoma completo de Chlamydia psittaci en muestras respiratorias, sanguíneas o de esputo. Una mayor conciencia de la psitacosis puede acortar los retrasos en el diagnóstico y mejorar los resultados de los pacientes.(AU)

Application of environmental sampling to investigate a case of avian chlamydiosis in a pet store and breeding facility leading to mass bird exposures.

Chlamydia psittaci is a bacterium that causes chlamydiosis in birds and can cause zoonotic psittacosis in people. In November 2017, we received notification of a suspected case of avian chlamydiosis in a captive cockatiel (Nymphicus hollandicus) that was sold by an online pet bird retail and breeding facility in Washington State. We describe the investigation with emphasis on how environmental sampling was used to guide veterinary and public health interventions. Bird samples were collected either from pooled droppings, pooled plumage or individual nasal and choanal swabs. Environmental samples were obtained by swabbing cleaning mops, tables and cage structures. All samples were tested by polymerase chain reaction and positive samples underwent genotyping. Approximately 1000 birds representing four taxonomic orders were kept within an open-space warehouse. Eight of 14 environmental samples and one of two pooled faecal samples were positive for Chlamydia spp. The contaminating strain of Chlamydia spp. was identified as genotype A. The facility was closed for environmental disinfection, and all psittacines were treated with oral doxycycline for 45 days. Ten of 10 environmental and two of two pooled faecal samples were negative for C. psittaci 11 months after the completion of environmental disinfection and antimicrobial treatment. This investigation highlights the importance of preventing and mitigating pathogen incursion in an online pet retail and breeding facility. Environmental sampling is valuable to guide animal and public health interventions for control of C. psittaci, particularly when large numbers of birds are exposed to the pathogen.

Prevalence of asymptomatic infections of Chlamydia psittaci in psittacine birds in Korea.

Avian chlamydiosis is an acute or chronic bacterial disease of birds. Chlamydia psittaci is the primary agent of the disease. It is also an important zoonotic pathogen. Chlamydia avium and Chlamydia gallinacea have also been recognized as potential causative agents of the disease. Clinical signs of this disease can vary in severity. Asymptomatic infections of Chlamydia have commonly been reported in various birds worldwide. In this study, we investigated the distribution of Chlamydia species in healthy psittacine birds in Korea. A total of 263 samples (pharyngeal/cloacal swabs and faeces) were collected from psittacine birds of 26 species in five zoos, five parrot farms and seven parrot cafes between 2020 and 2021. Ages of these birds had a wide range (1 month to 30 years). During sample collection, no bird showed any clinical signs indicating diseases such as chlamydiosis. Samples were tested for the presence of Chlamydia spp. using real-time PCR assays. Chlamydia spp. were detected in 168 (63.9%) samples and C. psittaci was detected in 96 (36.5%) samples. However, C. avium and C. gallinacea were not detected. There were no significant differences in the prevalence of asymptomatic infections in birds among three types of housing environments. Regarding ompA genotypes, 87 C. psittaci-positive samples had genotype A based on sequence analysis (n = 28) and genotype-specific real-time PCR (n = 59). Other positive samples were untyped (n = 9). Overall findings showed high prevalence of asymptomatic infections of C. psittaci in psittacine birds in Korea, posing a significant hazard to public health.

Physcion, a novel anthraquinone derivative against Chlamydia psittaci infection.

Physcion, a natural anthraquinone derivative, has been reported to exert remarkable antibacterial activities against Staphylococcus aureus,Staphylococcus epidermidis and Pseudomonas aeruginosa. However, it is not fully illustrated as anti-Chlamydia substance. In the present study, minimum inhibitory concentration(MIC)values for physcion against Chlamydia psittaci(C.psittaci) 6BC, C.psittaci SBL and C.psittaci HJ were 128 µg/mL,256 µg/mL and 128 µg/mL while minimum bactericidal concentration (MBC) values were 256 µg/mL,512 µg/mL and 256 µg/mL,respectively. Moreover, Chlamydial adhesion to Hela 229 cells was blocked in a dose-dependent manner and RB-to-EB differentiation was inhibited by physcion from 28 to 48 hpi.Post treatment,upregulation of LC3-II was in a dose-dependent manner, indicating physcion activated autophagy and bacterial clearance.To validate clinical efficacy,49 SPF chickens aged 21days were divided into 5 groups and infected intra-laryngeally with 0.2 mL of 1 × 107 IFU/mL C.psittaci 6 BCE.Three days later, birds received orally with serial doses of physcion (4 mg/kg to 9 mg/kg), or 3 mg/kg of doxycycline for 6 days.Chickens with difficulty in breathing were alleviated significantly with increasing concentrations of physicon.Postmortem,lesions of air sacs were reduced significantly in a dose-dependent manner.More importantly,birds with 9 mg/kg of physcion could alleviate lesions of air sacs and lungs, and reduce bacterial loads in spleens, which was comparable to doxycycline treatment. Based on above evidences, physcion is a promising cost-effective natural drug by blocking Chlamydial adhesions to host cells, RB-to-EB differentiation and activating bacterial autophagy and it will be a good alternative to doxycycline combating virulent C.psittaci infection, contributing to eradication of Chlamydial transmission from animals to human beings.

Chlamydia psittaci inclusion membrane protein CPSIT_0842 induces macrophage apoptosis through MAPK/ERK-mediated autophagy.

Chlamydia psittaci is a multi-host zoonotic pathogen, which mainly infects poultry and inflicts an appreciable economic burden on the livestock farming industry. C. psittaci inclusion membrane proteins are uniquely positioned at the host-pathogen interface and are important virulence proteins. We have previously confirmed that Incs regulate host cell survival to help Chlamydia sp. evade host-cell-mediated defense mechanisms. However, the role of the Inc, CPSIT_0842, in the regulation of cell death following the establishment of persistent C. psittaci infection remains unknown. This study explored the effect of CPSIT_0842 on the crosstalk between the autophagic and apoptotic pathways in macrophages. Results showed that CPSIT_0842 initiated autophagy and blocked autophagic flux in human macrophages, as indicated by autophagy-related protein LC3-II, Beclin-1, and p62 upregulation, autophagosome accumulation, and lysosomal protein LAMP1 diminution. We also showed that the disruption of autophagic flux had a regulatory effect on CPSIT_0842-induced apoptosis. Moreover, the suppression of autophagy initiation by 3-methyladenine attenuated CPSIT_0842-induced apoptosis. By contrast, the induction of autophagic flux by rapamycin did not significantly affect CPSIT_0842-induced apoptosis. Taken together, these findings demonstrate that CPSIT_0842 induced macrophage apoptosis by initiating incomplete autophagy through the MAPK/ERK/mTOR signaling pathway, which may be instrumental to the ability of C. psittaci to evade the host innate immune response and establish persistent infection. The improved understanding of the autophagic and cell death pathways triggered upon bacterial inclusion will likely help in the development of novel treatment strategies for chlamydia infection.

First detection of Chlamydia avium in healthy Amazon parrots (Amazona aestiva) in Argentina.

In recent years, new Chlamydia species, other than Chlamydia psittaci, have been confirmed in birds. One of these new species, Chlamydia avium, was reported mainly in pigeons and parrots in Europe. Analyzing multimucosal swabs obtained from 7 Amazon parrots (Amazona aestiva) from illegal trade and admitted to the Reserva Experimental Horco Molle (Tucuman, Argentina) for their rehabilitation, we describe the finding of the genetic material of C. avium in 2 of these birds. There were no signs compatible with the chlamydiosis-like disease in the studied birds or in the rehabilitation center staff. The use of sensitive and wide-ranging molecular tools is necessary for the detection of all Chlamydiaceae present in birds and would aid in the selection of control measures in wildlife rehabilitation centers to prevent outbreaks in the facilities and the introduction of pathogens in nature. We provide the first molecular evidence of the presence of C. avium in Argentina and a new species of psittacine host.

Persistent renal replacement requirement following fulminant psittacosis infection in pregnancy.

Chlamydia psittaci is a zoonotic bacterial infection that most commonly causes mild flu-like symptoms in humans. However, in pregnancy, it can present as fulminant psittacosis associated with systemic illness, disseminated intravascular coagulation, renal and hepatic failure. We describe a case of a veterinary nurse in her 30s who presented at 32 weeks' gestation with rapidly progressive multiorgan failure, with positive, C. psittaci serology. Further history revealed that she had delivered a number of dead lambs in the preceding weeks to her illness, highlighting the importance of a thorough social history. C. psittaci should be suspected in the differential as a causative organism for severe pneumonia with multiorgan failure particularly in pregnant women with animal or bird contacts.

A Chlamydia psittaci Outbreak in Psittacine Birds in Sardinia, Italy.

Chlamydia psittaci is an intracellular bacterium belonging to the Chlamydiaceae family. It is the ethiologic agent of psittacosis, an occupational zoonotic disease that mainly concerns people who work in close contact with birds that represent the main infection route for human transmission. In Italy, information about this disease is lacking. This study is the first case of avian chlamydiosis reported from a pet shop in Sardinia, Italy. Chlamydia psittaci detected in psittacine birds by molecular analysis, direct immunofluorescence test together with anatomo-pathological observed lesions, highlighted the importance of focusing the attention over this underestimated zoonosis in a "One Health" prospective.

Application of Metagenomic Next-Generation Sequencing in the Diagnosis of Pneumonia Caused by Chlamydia psittaci.

Psittacosis is an uncommon disease which mainly presents as community-acquired pneumonia (CAP). We aim to apply metagenomic next-generation sequencing (mNGS) as a promising tool in the diagnosis of psittacosis pneumonia and to describe its clinical spectrum to provide physicians with a better understanding and recognition of this disease. Thirteen cases of psittacosis pneumonia were diagnosed by using mNGS. A retrospective analysis of the data on clinical manifestations, laboratory data, computed tomography (CT) images, new diagnosis tools, treatments, and outcomes was summarized. These patients had common symptoms of fever and weakness; some had poor appetite, cough, myalgia, and headache. Ten patients developed acute respiratory distress syndrome (ARDS), among which six patients were severe pneumonia cases and needed ventilator therapy. Most patients got psittacosis pneumonia during the cold season. Ten cases were sporadic, but three were family clustering. All of the 13 patients were traced to an exposure history to birds, cat, or poultry, among which 2 only touched the innards of killed poultry before cooking, which may be an atypical exposure history not been reported before, to our knowledge. Most patients had various degrees of liver dysfunction. Air-space consolidations, along with ground-glass opacities and reticular shadows, were detected on chest CT scan. mNGS takes 48 to 72 h to provide results and helps to diagnose psittacosis. After being diagnosed by mNGS, with effective medicines, all patients finally had complete recoveries. The use of mNGS can improve the diagnostic rate of psittacosis pneumonia and shorten the course of disease control. IMPORTANCE Psittacosis pneumonia is easily underdiagnosed and misdiagnosed. In this study, we use mNGS in the diagnosis of psittacosis pneumonia. We found this disease is prone in the cold season, and touching the innards of killed poultry during cooking may be an atypical exposure history which has not been reported before to our knowledge. There are sporadic cases and family outbreak cases as well. Except for typical symptoms of fever and weakness, headache may be the main and only symptom in some patients. The rate of severe pneumonia is high among inpatients with psittacosis pneumonia, and the incidence of hepatic involvements is also high. Psittacosis pneumonia can be cured if the diagnosis is accurate and in time, even if it is severe pneumonia on admission. Some problems worthy of our attention about psittacosis pneumonia were put forward, such as its sick season, special exposure history, the rate of severe disease, and the high cure rate. mNGS can quickly and objectively detect more rare pathogenic microorganisms in clinical specimens without the need for specific amplification and has an advantage in the diagnosis of rare pathogenic bacteria in difficult cases such as psittacosis pneumonia. The use of mNGS can improve the accuracy and reduce the delay in the diagnosis of psittacosis, which shortens the course of disease control.

Chlamydia psittaci plasmid-encoded CPSIT_P7 induces macrophage polarization to enhance the antibacterial response through TLR4-mediated MAPK and NF-κB pathways.

Although the protective effects of Chlamydia psittaci plasmid-encoded protein CPSIT_P7 as vaccine antigens to against chlamydial infection have been confirmed in our previous study, the function and mechanism of CPSIT_P7 inducing innate immunity in the antibacterial response remain unknown. Here, we found that plasmid protein CPSIT_P7 could induce M1 macrophage polarization upregulating the genes of the surface molecule CD86, proinflammatory cytokines (TNF-α, IL-6, and IL-1ß), and antibacterial effector NO synthase 2 (iNOS). During M1 macrophage polarization, macrophages acquire phagocytic and microbicidal competence, which promotes the host antibacterial response. As we observed that CPSIT_P7-induced M1 macrophages could partially reduce the infected mice pulmonary Chlamydia psittaci load. Furthermore, CPSIT_P7 induced M1 macrophage polarization through the TLR4-mediated MAPK and NF-κB pathways. Collectively, our results highlight the effect of CPSIT_P7 on macrophage polarization and provide new insights into new prevention and treatment strategies for chlamydial infection.

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.

Development and comparative evaluation of droplet digital PCR and quantitative PCR for the detection and quantification of Chlamydia psittaci.

Chlamydia psittaci is a zoonotic pathogen mainly transmitted by psittacine birds and poultry. The low shedding rate of the pathogen in the apparently healthy birds and human clinical cases may result in false-negative results. In the present study, a droplet digital PCR (ddPCR) assay was developed and compared with optimized quantitative PCR (qPCR) for the detection of C. psittaci from the clinical samples. The ddPCR assay was found to be comparatively more sensitive than the qPCR, wherein the limit of detection (LOD) of ddPCR was upto 2.4 copies of the DNA template, whereas, the qPCR could detect upto 38 copies of the DNA template in the reaction mixture. Overall, the developed ddPCR assay was found to be robust, specific, and could reliably quantify up to 17.8 copies of the DNA template. Finally, the applicability of the developed ddPCR assay was tested by screening the field samples (n = 124), comprising lung tissues from dead poultry and feral birds; pooled faecal samples from the free-living birds, commercial and backyard poultry farms; pharyngeal and cloacal swabs collected from the duck farms. Of these, a total of seven samples were found to be positive by the ddPCR, whereas, three samples could be detected as positive using the qPCR. The developed ddPCR could serve as a reliable screening tool, particularly in those clinical samples wherein the shedding of C. psittaci is substantially very low.

Application of metagenomic next-generation sequencing in the diagnosis of severe pneumonia caused by Chlamydia psittaci.

PURPOSE: Psittacosis is a zoonotic infectious disease caused by the transmission of the bacterium Chlamydia psittaci (C. psittaci) from birds to humans. Infections in humans mainly present as community-acquired pneumonia (CAP). However, most cases are treated without diagnostic testing, and the importance of Chlamydia psittaci infection as a cause of CAP is therefore unclear. Diagnostic tools, including culture, serologic test, and PCR-based methods, are available but prone to false negative results. Metagenomic next-generation sequencing (mNGS) has been increasingly used in the diagnosis of infectious diseases, particularly when conventional diagnostic approaches have limitation. Detection of nucleic acid sequence of C. psittaci in respiratory tract samples by metagenomic next-generation sequencing (mNGS) is effective for early diagnosis of severe C. psittaci pneumonia. Timely treatment based on tetracycline can reduce unnecessary use of antibiotics and improve prognosis of patients with severe C. psittaci pneumonia. METHODS: Clinical data of thirteen patients with severe C. psittaci pneumonia diagnosed by mNGS were collected. Clinical manifestations, treatment and prognosis of patients were summarized. RESULTS: The typical symptoms of pneumonia caused by C. psittaci include fever, headache, myalgia, cough, and dyspnea. In the current study, all patients met the criteria for severe C. psittaci pneumonia and received mechanical ventilation, including noninvasive mechanical ventilation (five/thirteen) and invasive mechanical ventilation (eight/thirteen). The findings showed that patients with C. psittaci pneumonia presented with normal or slightly increased leucocytes and procalcitonin, and high C-reactive protein levels. Computed tomography manifestations included consolidation of lung parenchyma, with air bronchogram and pleural effusion in some patients. mNGS analysis results were obtained within 48-72 h. Eleven patients fully recovered after targeted treatment, however, two patients died from secondary multidrug-resistant Pseudomonas aeruginosa infection. CONCLUSIONS: The findings of the current study show that mNGS is effective in diagnosis of C. psittaci pneumonia, and has significant diagnosis value in patients with severe infection. Patients responds well to the timely use of appropriate antibiotics.

Genetic and phenotypic analysis of the pathogenic potential of two novel Chlamydia gallinacea strains compared to Chlamydia psittaci.

Chlamydia gallinacea is an obligate intracellular bacterium that has recently been added to the family of Chlamydiaceae. C. gallinacea is genetically diverse, widespread in poultry and a suspected cause of pneumonia in slaughterhouse workers. In poultry, C. gallinacea infections appear asymptomatic, but studies about the pathogenic potential are limited. In this study two novel sequence types of C. gallinacea were isolated from apparently healthy chickens. Both isolates (NL_G47 and NL_F725) were closely related to each other and have at least 99.5% DNA sequence identity to C. gallinacea Type strain 08-1274/3. To gain further insight into the pathogenic potential, infection experiments in embryonated chicken eggs and comparative genomics with Chlamydia psittaci were performed. C. psittaci is a ubiquitous zoonotic pathogen of birds and mammals, and infection in poultry can result in severe systemic illness. In experiments with embryonated chicken eggs, C. gallinacea induced mortality was observed, potentially strain dependent, but lower compared to C. psittaci induced mortality. Comparative analyses confirmed all currently available C. gallinacea genomes possess the hallmark genes coding for known and potential virulence factors as found in C. psittaci albeit to a reduced number of orthologues or paralogs. The presence of potential virulence factors and the observed mortality in embryonated eggs indicates C. gallinacea should rather be considered as an opportunistic pathogen than an innocuous commensal.

Detection of Chlamydia psittaci in both blood and bronchoalveolar lavage fluid using metagenomic next-generation sequencing: A case report.

RATIONALE: Chlamydia psittaci (C psittaci) is a gram-negative obligate intracellular parasite, with birds as main hosts. The main route of infection in humans is inhalation of aerosols from contaminated animal excreta through the respiratory tract. The main manifestation of C psittaci infection is pneumonia. Patients suffering from severe infection are prone to sepsis and multiple organ failure. We report a case of simultaneous detection of C psittaci in blood and bronchoalveolar lavage fluid using metagenomic next-generation sequencing (mNGS) technology. PATIENT CONCERNS: The 71-year-old male patient was a farmer with a long history of raising poultry and initial symptoms of fever and muscle pain accompanied by limb weakness and paroxysmal cough. DIAGNOSES: The patient was diagnosed with sepsis, severe pneumonia, and multiple organ failure. INTERVENTIONS: Anti-infective therapy with doxycycline and meropenem was applied. OUTCOMES: The patient's body temperature and infection indicators improved and the chest X-ray findings showed the amelioration of lesions after 18 days of treatment. The patient was discharged without treatment on hospital day 19 due to financial constraints and subsequently died after 7 days. LESSONS: mNGS is an excellent diagnostic tool when specific pathogens are undetected by traditional assays.

Metagenomic next-generation sequencing in the family outbreak of psittacosis: the first reported family outbreak of psittacosis in China under COVID-19.

Chlamydia psittaci infection in humans, also known as psittacosis, is usually believed to be an uncommon disease which mainly presents as community-acquired pneumonia (CAP). It is usually sporadic, but outbreaks of infection may occasionally occur. In outbreaks, diagnosis and investigations were usually hampered by the non-specificity of laboratory testing methods to identify C. psittaci. In this study, we use metagenomic next-generation sequencing (mNGS) in the diagnosis of a family outbreak of psittacosis under COVID-19. Three members of an extended family of 6 persons developed psittacosis with pneumonia and hepatic involvement with common symptoms of fever and weakness. Two newly purchased pet parrots, which had died successively, were probably the primary source of infection. Imagings show lung consolidations and infiltrates, which are difficult to be differentiated from CAP caused by other common pathogens. mNGS rapidly identified the infecting agent as C. psittaci within 48 h. The results of this work suggest that there are not characteristic clinical manifestations and imagings of psittacosis pneumonia which can differentiate from CAP caused by other pathogens. The use of mNGS can improve accuracy and reduce the delay in the diagnosis of psittacosis especially during the outbreak, which can shorten the course of the disease control. Family outbreak under COVID-19 may be related to the familial aggregation due to the epidemic. To our knowledge, this is the first reported family outbreak of psittacosis in China, and the first reported psittacosis outbreak identified by the method of mNGS in the world.

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.

A recombinase polymerase amplification-based assay for rapid detection of Chlamydia psittaci.

Chlamydia psittaci is a zoonotic agent of systemic wasting disease in birds and atypical pneumonia in mammalians including humans, constituting a public health risk. A rapid diagnostic assay would be beneficial in screening C. psittaci in the field. In this study, we developed a probe-based recombinase polymerase amplification (RPA) assay for the rapid detection of C. psittaci. The specific primer pairs and probe targeting the conserved region of the outer membrane protein A gene were designed and applied to the real-time real-time RPA assay. The test can be performed at 39°C for 20 min using a portable device, with sensitivities approaching 100 copies of DNA molecules per reaction, with no cross-reaction with other pathogens. The clinical performance of the RPA assay was evaluated in an outbreak of C. psittaci and has high accuracy levels in field applications. The epidemic C. psittaci strains were classed into 2 genotypes: A and C. Collectively, this study offers a promising approach in screening for C. psittaci both in a laboratory setting and in field settings, and RPA can be used as an effective clinical test to monitor outbreaks in domestic fowl populations.

Polymorphic Membrane Protein 17G of Chlamydia psittaci Mediated the Binding and Invasion of Bacteria to Host Cells by Interacting and Activating EGFR of the Host.

Chlamydia psittaci (C. psittaci) is an obligate intracellular, gram-negative bacterium, and mainly causes systemic disease in psittacine birds, domestic poultry, and wild fowl. The pathogen is threating to human beings due to closely contacted to employees in poultry industry. The polymorphic membrane proteins (Pmps) enriched in C. psittaci includes six subtypes (A, B/C, D, E/F, G/I and H). Compared to that of the 1 pmpG gene in Chlamydia trachomatis (C. trachomatis), the diverse pmpG gene-coding proteins of C. psittaci remain elusive. In the present study, polymorphic membrane protein 17G (Pmp17G) of C. psittaci mediated adhesion to different host cells. More importantly, expression of Pmp17G in C. trachomatis upregulated infections to host cells. Afterwards, crosstalk between Pmp17G and EGFR was screened and identified by MALDI-MS and Co-IP. Subsequently, EGFR overexpression in CHO-K1 cells and EGFR knockout in HeLa 229 cells were assessed to determine whether Pmp17G directly correlated with EGFR during Chlamydial adhesion. Finally, the EGFR phosphorylation was recognized by Grb2, triggering chlamydial invasion. Based on above evidence, Pmp17G possesses adhesive property that serves as an adhesin and activate intracellular bacterial internalization by recognizing EGFR during C. psittaci infection.