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Vol. 53. Issue 5.
Pages 277-279 (May 2017)
Scientific Letter
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Atypical Chlamydia psittaci Pneumonia. Four Related Cases
Neumonía atípica por Chlamydia psittaci. Cuatro casos relacionados
Nuria Arenas-Vallsa, Silvia Chacónb, Alfredo Pérezc, Roberto del Pozoa,
Corresponding author

Corresponding author.
a Pneumonology Department, Hospital Universitario 12 de Octubre, Madrid, Spain
b Critical Care Unit, Hospital Universitario 12 de Octubre, Madrid, Spain
c Microbiology Department, Hospital Universitario 12 de Octubre, Madrid, Spain
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Table 1. Comparative Characteristics of the Cases.
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To the Editor,

Psittacosis is a globally distributed zoonotic disease caused by Chlamydia psittaci (C. psittaci), an intracellular bacteria.1 Birds constitute its main reservoir and the mechanism of transmission is direct contact or inhalation of respiratory secretions or dry feces of infected birds.2 Individuals with occupational or recreational exposure to various birds have a greater risk of infection.3 Psittacosis generally occurs sporadically, but outbreaks have been reported.2 Presentation varies from subclinical infection to severe sepsis and multisystemic involvement.3,4 We describe an outbreak of 4 cases of C. psittaci pneumonia, the focus of infection being a store selling birds (Table 1).

Table 1.

Comparative Characteristics of the Cases.

  Case 1  Case 2  Case 3  Case 4 
Exposure  Customer  Employee  Employee  Employee 
Place admitted  ICU  ICU  Hospital ward  Hospital ward 
Days admitted  60+21  6+
CRP (mg/ml) admission  49  58  41  39 
CRP (mg/ml) 7246  21 
Chest radiograph admission  Infiltrate both lower lobes  Alveolar infiltrate 3 right lobes
Alveolar infiltrate right lower lobe  Alveolar infiltrate right upper and middle lobe 
Chest radiograph at 1 month  Bilateral infiltrate consistent with ARDS  Normal  Normal  Normal 
Complications  Septic shock Multiorgan failure  Septic shock  Severe sepsis  Severe sepsis 
C. psittaci serology 

CRP: C-reactive protein; ICU: Intensive Care Unit.

Case 1

A 47-year-old man was admitted with a 5-day history of dyspnea and fever. On admission, he presented tachypnea and crackles in the right lung base, respiratory failure (RF) (PaO2 55mmHg), neutrophilia (91%), elevated C-reactive protein (CRP) (49mg/dl), procalcitonin (PCT) 1mg/ml, and alveolar infiltrate in the right lower lobe. Antibiotic treatment with ceftriaxone, levofloxacin and doxycycline was administered for 2 weeks, followed by oseltamivir for 5 days. After 24h he developed respiratory failure and progressive radiological infiltration, renal failure and shock, so was admitted to the intensive care unit (ICU). Invasive mechanical ventilation was initiated, with noradrenaline 0.4mcg/kg/min and extrarenal depuration. In view of the lack of response, veno-venous extracorporeal membrane oxygenation support (ECMO) was required. Progress was slow and weaning prolonged, and the patient was discharged from the ICU after 60 days, and from the hospital 81 days after admission. C. psittaci DNA was detected in respiratory samples (nasopharyngeal exudate and tracheal aspirate) by polymerase chain reaction (PCR). No other microorganisms were found, including influenza virus. Immunofluorescence testing for C. psittaci serology was positive (IgG seroconversion 1:256 after 14 days from the first sample).

Case 2

A 22-year-old man was admitted with a 1-week history of fever, dry cough, and general malaise. Physical examination showed fever, arterial hypertension, tachycardia, and crackles in the entire right hemithorax. The patient presented respiratory failure (PaO2 53mmHg), neutrophilia (87%), elevated CRP 58mg/dl, clotting disorders with prothrombin activity 55%, and multilobar infiltrate in right lung. He received high-flow oxygen therapy in the ICU. Ceftriaxone, levofloxacin and doxycycline were administered for 2 weeks. C. psittaci serology was positive, with IgG seroconversion (1:256) in convalescent serum. All other microbiological results were negative, including C. psittaci PCR of nasopharygeal exudate. Clinical symptoms and radiological signs resolved after 6 weeks.

Case 3

A 20-year-old man was admitted with a 1-week history of fever, cough with white sputum, and general malaise. Physical examination revealed fever and crackles in the right lung base. Clinical laboratory results showed neutrophilia (84%), CRP 41mg/dl and prothrombin activity 58%. Chest radiograph revealed alveolar infiltrate in the left lower lobe. Treatment began with azithromycin (discontinued on day 3), ceftriaxone, and doxycycline lasting 10 days. The patient showed clinical, analytical and radiological improvement. IgG seroconversion (1:256) observed in convalescent serum. All other microbiological results were negative, including C. psittaci PCR of nasopharygeal exudate. At 1 month, the patient was asymptomatic and radiological images were resolved.

Case 4

A 52-year-old woman was admitted with a 1-week history of fever, cough, and mucous expectoration, with a tendency toward arterial hypertension. Respiratory failure (PaO2 57mmHg), neutrophilia (87%), raised CRP (39mg/dl), procalcitonin 30ng/ml, and right bilobar infiltrate. Treatment began with ceftriaxone and azithromycin and continued for 10 days. PCR of nasal exudate was negative for C. psittaci, and IgG seroconversion (1:256) was observed in the convalescent serum. All other microbiological results were negative. At 1 month, the patient was asymptomatic and radiological images had resolved.

Outbreaks of psittacosis have been described primarily in individuals exposed to birds, for example, veterinary surgeons and employees of stores selling animals.4 Other outbreaks of psittacosis associated with occupational exposure in bird farms have been described.5,6 We report an outbreak of 4 cases of psittacosis with different degrees of severity, ranging from mild pneumonia to multiorgan failure requiring ECMO and a prolonged ICU stay. All of the subjects visited a bird store which sold Agapornis (love birds) that showed signs of disease. The infection may be indistinguishable from other atypical pneumonias, so the history of exposure to birds was key to guiding the suspected diagnosis.3,7 Severity may vary widely, from mild respiratory infection to full-blown disease, requiring intensive care and even ECMO.3 Diagnosis is based on the clinical examination, epidemiological history, and laboratory confirmation using direct (culture, PCR) or indirect (serology) methods.1 Given the complexity of culturing C. psittaci (biosafety level 3) and the unavailability of commercial molecular methods (PCR), diagnosis is based on serologies.1,8 In the cases discussed here, serological confirmation was obtained when specific IgG seroconversion was detected at 14–17 days after the initial sample, except for case 3, in whom it was detected in a third sample obtained at 37 days. In all cases detection of specific IgM in the acute phase was negative. DNA detection of C. psittaci was performed in respiratory samples from all patients using a non-commercial PCR technique,9 but this was positive in the most severe case only. C. psittaci infections are very rare in humans and molecular tests are not standardized, so these techniques have not been widely evaluated in clinical samples, and sensitivity and specificity data are scant.10

Tetracyclines, macrolides and quinolones are the best empirical treatments for intracellular bacteria.11 Our cases were initially treated in different hospital departments (emergency room, UCI) by different physicians, thus explaining the different treatment regimens. Antibiotic cover was maintained on the pulmonology ward with a betalactam and an antibiotic with intracellular action. Improvement is generally observed 48h after starting antibiotic treatment.2


The authors would like to thank Dr. Carlos José Álvarez of the Respiratory Medicine Department of the Hospital 12 de Octubre for his critical review of the manuscript, and Dr. Nerea García Benzaquén, of the Department of Emerging Rare and Biologically Aggressive Zoonosis of the Center for Veterinary Health Surveillance (VIVASET) of the Universidad Complutense, Madrid, for performing C. psittaci DNA molecular dectection assays. We would also like to thank Sara Álvarez and Lidia Sotillo, medical students at the Universidad Complutense, Madrid, for their clinical interest in these cases.

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Please cite this article as: Arenas-Valls N, Chacón S, Pérez A, del Pozo R. Neumonía atípica por Chlamydia psittaci. Cuatro casos relacionados. Arch Bronconeumol. 2017;53:277–279.

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