Community-acquired Pneumonia Due to Chlamydia Pneumoniae (CHLAMPAC)

Prevalence and Phenotyping of Chlamydia Pneumoniae Infections Among Pnuemonias Tested With Simplex and Multiplex PCR

This international retrospective Franco-Swiss study focuses on community-acquired pneumonia (CAP) caused by Chlamydia pneumoniae.

The working hypothesis is that the prevalence of C. pneumoniae pneumonia is overestimated by the medical community.

The primary objective is to determine the true prevalence of C. pneumoniae infections among patients with pneumonia who underwent simplex or multiplex PCR testing.

Secondary objectives include;

1. Outpatient management
2. Hospitalization in a medical ward
3. Admission to the intensive care unit
4. In-hospital mortality
5. Radiological presentation of patients with community-acquired pneumonia (CAP) caused by Chlamydia pneumoniae
6. Prevalence of viral or bacterial co-infections associated with C. pneumoniae CAP

Study Overview

• Status: Not yet recruiting
• Conditions: Community-Acquired Pneumonia

Detailed Description

This international retrospective Franco-Swiss study focuses on community-acquired pneumonia (CAP) caused by Chlamydia pneumoniae. The working hypothesis is that the prevalence of C. pneumoniae pneumonia is overestimated by the medical community. The primary objective is to determine the true prevalence of C. pneumoniae infections among patients with pneumonia who underwent simplex or multiplex PCR testing. Secondary objectives include;1)Outpatient management2)Hospitalization in a medical ward3)Admission to the intensive care unit4) In-hospital mortality5) Radiological presentation of patients with community-acquired pneumonia (CAP) caused by Chlamydia pneumoniae 6)Prevalence of viral or bacterial co-infections associated with C. pneumoniae CAP

Detailed Description We have all learned and continue to teach that community-acquired pneumonia (CAP) is essentially represented by three bacteria: Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydia pneumoniae. While the recent Mycoplasma outbreak in France and the prevalence of severe Legionella infections in intensive care units confirm the real impact of these pathogens in CAP, the low number of Chlamydia pneumoniae cases documented by PCR raises questions.Over the past twenty years, the development of highly sensitive molecular tests (specific PCR or multiplex PCR targeting intracellular respiratory pathogens) has made it possible to precisely detect Chlamydia pneumoniae and to confirm or rule out its presence in the respiratory tract of patients with pneumonia.We are therefore conducting a retrospective study between France and Switzerland to determine, on the one hand, the number of CAP cases due to Chlamydia pneumoniae confirmed by PCR, and on the other hand, to better characterize the phenotype of these patients.

• Study Type: Observational
• Enrollment (Estimated): 200

Contacts and Locations

• Study Contact: Name: Yacine Tandjaoui-Lambiotte, Principal Investigator; Phone Number: +33 1 42 35 61; Email: yacine.tandjaouilambiotte@ch-stdenis.fr
• Study Contact Backup: Name: Clinical Research Unit Coordinator Clinical Research Unit Coordinator, GHT Plaine de France Clinical; Phone Number: 6962 +33 1 42 35 61 40; Email: coordination.rechercheclinique@ghtpdfr.fr

Study Locations

• France
  • Saint-Denis, France, 93200
    • Centre Hospitalier de Saint-Denis
    • Contact: Yacine Tandjaoui-Lambiotte, Principal Investigator; Phone Number: +33 1 42 35 61; Email: yacine.tandjaouilambiotte@ch-stdenis.fr
    • Contact: Stéphanie COSSEC; Phone Number: 6962 0142356140; Email: stephanie.cossec@ghtpdfr.fr

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

The study population consists of pediatric and adult patients from participating French and Swiss centers who had a positive simplex or multiplex PCR result for Chlamydia pneumoniae on an upper or lower respiratory tract specimen between January 2015 and December 2025. Eligible patients must have a documented diagnosis of pneumonia and available clinical data allowing characterization of disease presentation, management, radiological findings, co-infections, and outcomes. Patients who objected to the use of their medical data for research purposes or who did not have pneumonia are excluded.

Description

Inclusion Criteria:

• Positive simplex or multiplex PCR for Chlamydia pneumoniae on an upper or lower respiratory tract specimen between January 2015 and December 2025.
• Availability of clinical data allowing confirmation of pneumonia diagnosis.

Exclusion Criteria:

• Patient opposition to the use of medical data for research purposes.
• Absence of pneumonia diagnosis.
• Insufficient clinical data for analysis.

Study Plan

How is the study designed?

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Prevalence of Chlamydia pneumoniae Among Pneumonia Cases Tested by PCR	Proportion of pneumonia cases with a positive simplex or multiplex PCR for Chlamydia pneumoniae among all patients who underwent respiratory PCR testing during the study period.	January 2015 to December 2025

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Clinical Severity of Chlamydia pneumoniae Pneumonia	Distribution of patients according to outpatient management, hospitalization in a medical ward, admission to intensive care, and in-hospital mortality.	From hospital admission through hospital discharge (up to 90 days)
Radiological Characteristics	Chest radiograph and chest computed tomography findings associated with PCR-confirmed Chlamydia pneumoniae pneumonia.	Baseline (at the time of pneumonia diagnosis)
Viral Co-Infection Rate	Proportion of patients with concomitant viral infection identified by microbiological testing.	Baseline (at the time of PCR testing)
Bacterial Co-Infection Rate	Proportion of patients with concomitant bacterial infection identified by microbiological testing.	Baseline (at the time of PCR testing)
Length of Hospital Stay	Duration of hospitalization among admitted patients.	From hospital admission through hospital discharge (up to 90 days)

Collaborators and Investigators

• Sponsor: Centre Hospitalier de Saint-Denis

Publications and helpful links

General Publications

• Garin N, Hugli O, Genne D, Greub G. Lack of Chlamydia-related bacteria among patients with community-acquired pneumonia. New Microbes New Infect. 2015 Oct 22;8:164-5. doi: 10.1016/j.nmni.2015.10.002. eCollection 2015 Nov. No abstract available.
• Garin N, Marti C, Skali Lami A, Prendki V. Atypical Pathogens in Adult Community-Acquired Pneumonia and Implications for Empiric Antibiotic Treatment: A Narrative Review. Microorganisms. 2022 Nov 24;10(12):2326. doi: 10.3390/microorganisms10122326.
• Miyashita N. Atypical pneumonia: Pathophysiology, diagnosis, and treatment. Respir Investig. 2022 Jan;60(1):56-67. doi: 10.1016/j.resinv.2021.09.009. Epub 2021 Nov 5.
• Cunha BA. The atypical pneumonias: clinical diagnosis and importance. Clin Microbiol Infect. 2006 May;12 Suppl 3:12-24. doi: 10.1111/j.1469-0691.2006.01393.x.

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): September 1, 2026
• Study Completion (Estimated): June 1, 2027

Study Registration Dates

• First Submitted: June 24, 2026
• First Submitted That Met QC Criteria: June 30, 2026
• First Posted (Actual): July 1, 2026

Study Record Updates

• Last Update Posted (Actual): July 1, 2026
• Last Update Submitted That Met QC Criteria: June 30, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Prevalence; PCR; Respiratory infection; Co-infection; Chlamydia pneumoniae; Community-acquired pneumonia; Atypical pneumonia
• Additional Relevant MeSH Terms: Infections; Respiratory Tract Diseases; Lung Diseases; Pneumonia; Bacterial Infections; Bacterial Infections and Mycoses; Gram-Negative Bacterial Infections; Pneumonia, Bacterial; Mycoplasmatales Infections; Community-Acquired Infections; Mycoplasma Infections; Respiratory Tract Infections; Coinfection; Pneumonia, Mycoplasma; Community-Acquired Pneumonia
• Other Study ID Numbers: 0079_MIR_CHLAMPAC

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No