Doxycycline vs. macrolides in combination therapy for treatment of community-acquired pneumonia

Comparison of Empiric Antibiotic Treatment Regimens for Hospitalized, Non-severe Community-acquired Pneumonia: A Retrospective, Multicenter Cohort Study

PURPOSE

Consensus guidelines for hospitalized, non-severe community-acquired pneumonia (CAP) recommend empiric macrolide + β-lactam or respiratory fluoroquinolone monotherapy in patients with no risk factors for resistant organisms. In patients with allergies or contraindications, doxycycline + β-lactam is a recommended alternative. The purpose of this study was to compare differences in outcomes among guideline-recommended regimens in this population.

METHODS

This retrospective, multicenter cohort study included patients ≥18 years of age with CAP who received respiratory fluoroquinolone monotherapy, empiric macrolide + β-lactam, or doxycycline + β-lactam. Major exclusion criteria included patients with immunocompromising conditions, requiring vasopressors or invasive mechanical ventilation within 48 hours of admission, and receiving less than 2 days of total antibiotic therapy. The primary outcome was in-hospital mortality. Secondary outcomes included clinical failure, 14- and 30-day hospital readmission, and hospital length of stay. Safety outcomes included incidence of new Clostridioides difficile infection and aortic aneurysm ruptures.

FINDINGS

Of 4685 included patients, 1722 patients received empiric respiratory fluoroquinolone monotherapy, 159 received empiric doxycycline + β-lactam, and 2804 received empiric macrolide + β-lactam. Incidence of in-hospital mortality was not observed to be significantly different among empiric regimens (doxycycline + β-lactam group: 1.9% vs macrolide + β-lactam: 1.9% vs respiratory fluoroquinolone monotherapy: 1.5%, P = 0.588). No secondary outcomes were observed to differ significantly among groups.

IMPLICATIONS

We observed no differences in clinical or safety outcomes among three guideline-recommended empiric CAP regimens. Empiric doxycycline + β-lactam may be a safe empiric regimen for hospitalized CAP patients with non-severe CAP, although additional research is needed to corroborate these observations with larger samples.

β-Lactams plus doxycycline versus azithromycin for treatment of severe community-acquired pneumonia in critically ill patients

OBJECTIVES

Community-acquired pneumonia (CAP) is a significant source of hospital admissions and mortality. Atypical organisms are implicated in up to 40% of cases of CAP diagnoses. We studied the difference in outcomes of severe CAP patients treated with doxycycline versus azithromycin in addition to β-lactam therapy.

PATIENTS AND METHODS

This was a prospective observational cohort study from March 2020 to July 2022 in a medical ICU (MICU) of an academic quaternary medical center. Adults ≥18 years admitted to the MICU receiving doxycycline or azithromycin in addition to β-lactam therapy for the treatment of CAP were included for analysis. The primary outcomes were in-hospital and 30 day mortality. Secondary outcomes were ICU and hospital length-of-stay, 30 day readmission, days of mechanical ventilation, escalation and duration of antibiotics, adverse effects such as Clostridioides difficile infection and QTc prolongation.

RESULTS

Sixty-three patients were in the azithromycin group and eighty-six patients in the doxycycline group. Both groups had similar APACHE IV and CURB-65 scores. The mean Charlson Comorbidity Index score was higher for the doxycycline group compared with the azithromycin group (P = 0.04). There was no statistically significant difference in in-hospital and 30 day mortality between the groups (P = 0.53, P = 0.57). There were no significant differences in any of the secondary outcomes.

CONCLUSIONS

MICU patients with severe CAP who received doxycycline versus azithromycin in addition to β-lactam treatment showed no significant differences in outcomes. These data offer support for inclusion of doxycycline as an alternative regimen in current IDSA recommendations.

Appropriateness of antimicrobial selection for treatment of pneumonia in selected public hospitals of Eastern Ethiopia: A cross-sectional study

Objective

Inappropriate antimicrobial use leads to drug resistance and poor clinical outcomes. Considering the lack of data regarding the drug use patterns in the treatment of pneumonia in selected study areas, the authors felt compelled to assess the appropriateness of antimicrobial usage in the treatment of pneumonia at Hiwot Fana Specialized Comprehensive University Hospital and Jugal Hospital from May 1 to 31, 2021.

Methods

A cross-sectional retrospective study was conducted using the medical cards of 693 admitted patients with pneumonia. The collected data were analyzed using SPSS version 26. Bivariable and multivariable logistic regression analyses were used to identify the factors associated with an initial inappropriate antibiotic use. A p value of 0.05 was used to determine the statistical significance of the association using an adjusted odds ratio with 95% confidence interval.

Results

Of the total participants, 116 (16.74%, 95% confidence interval: 14.1-19.6) of them received an initial inappropriate antimicrobial regimen. Ceftriaxone plus azithromycin was the most prescribed antimicrobial agent. Patients who were younger than 5 years (adjusted odds ratio = 1.71; 95% confidence interval: 1.00-2.94), between 6 and 14 years (adjusted odds ratio = 3.14; 95% confidence interval: 1.64-6.00), and older than 65 years (adjusted odds ratio = 2.97; 95% confidence interval: 1.07-2.66), with comorbid conditions (adjusted odds ratio = 1.74; 95% confidence interval: 1.10-2.72) and prescribed by medical interns (adjusted odds ratio = 1.80; 95% confidence interval: 1.14-2.84) were associated with an initial inappropriate antimicrobial use.

Conclusion

Around one out of every six patients had received initial inappropriate treatments. Adherence to the recommendation of guidelines and attention to extreme-aged groups and comorbidity may improve antimicrobial use.

Doxycycline vs. macrolides in combination with a β-lactam antibiotic for the treatment of community-acquired pneumonia in inpatients

BACKGROUND

Hospitalized patients with non-severe community-acquired pneumonia (CAP) are treated with a β-lactam plus either a macrolide or doxycycline. Limited data exist on the effectiveness of the latter combination. Therefore, we aimed to compare the combination of doxycycline vs. macrolide when either is combined with a β-lactam from effectiveness and safety perspectives.

METHODS

This was a retrospective cohort study in CAP inpatients between December 2013 and November 2020. Patients were divided into BL-D (β-lactam plus doxycycline) and BL-M (β-lactam plus a macrolide [azithromycin or clarithromycin]) groups. The primary endpoint was time to clinical stability. Secondary endpoints included length of stay (LOS) and in-hospital mortality.

RESULTS

Of 197 patients included, 57 were in the BL-D arm and 140 were in the BL-M arm. Patients were similar at baseline, except for the presence of leukocytosis, risk factors for drug resistance, and duration of therapy (P < 0.05 for all comparisons). No difference in clinical cure rate was observed (94.7% vs. 91.4%; P = 0.43). Time to clinical stability and LOS were similar in both groups at 4 (P = 0.82) and 7 days (P = 0.62), respectively. While only three patients died, only one (from the BL-M group) was due to sepsis. Liver enzymes elevation was more prominent in the BL-M group (21.4% vs. 5.3%; P = 0.01). A subgroup analysis showed shorter time to clinical stability with clarithromycin but higher cure rates with azithromycin.

CONCLUSIONS

Data on doxycycline use with a β-lactam are scarce. Our study showed that such regimen was comparable in effectiveness to regimens involving macrolides with a better safety profile.

Effectiveness of Beta-Lactam plus Doxycycline for Patients Hospitalized with Community-Acquired Pneumonia

BACKGROUND

Despite clinical practice guideline recommendations to use doxycycline as part of combination therapy for some patients hospitalized with pneumonia, there is minimal evidence supporting this recommendation. Our aim was to examine the association between beta-lactam plus doxycycline and mortality for patients hospitalized with community-acquired pneumonia.

METHODS

We identified patients > 65 years of age admitted to any United States Department of Veterans Affairs hospital in fiscal years 2002-2012 with a discharge diagnosis of pneumonia. We excluded those patients who did not receive antibiotic therapy concordant with the 2019 ATS/IDSA clinical practice guidelines. Using propensity score matching, we examined the association of doxycycline with 30- and 90-day mortality.

RESULTS

Our overall cohort was comprised of 70,533 patients and 5,282 (7.49%) received doxycycline. Unadjusted 30-day mortality was 6.4% for those who received a beta-lactam plus doxycycline vs. 9.1% in those who did not (p<0.0001), and 90-day mortality was 13.8% for those who received a beta-lactam + doxycycline vs. 16.8% for those who did not (p<0.0001). In the propensity score matched models, both 30- (odds ratio 0.72, 95% confidence interval, 0.63-0.84) and 90-day (0.83, 0.74-0.92) mortality were significantly lower for those who received doxycycline.

CONCLUSIONS

In this retrospective observational cohort study, we found that doxycycline use, as part of guideline-concordant antibiotic therapy, was associated with lower 30- and 90-day mortality than regimens without doxycycline. While this supports the safety and effectiveness of antibiotic regimes that include doxycycline, additional studies, especially randomized clinical trials, are needed to confirm this.

Use of Oral Tetracyclines in the Treatment of Adult Patients with Community-Acquired Bacterial Pneumonia: A Literature Review on the Often-Overlooked Antibiotic Class

Oral tetracyclines have been used in clinical practice for over 60 years. Overall, one of the most common indications for use of oral tetracyclines is for treatment of adult outpatients with lower respiratory tract infections, including community-acquired pneumonia (CAP). Despite the longstanding use of oral tetracyclines, practice patterns indicate that they are often considered after other guideline-concordant oral CAP treatment options (namely macrolides, fluoroquinolones, and β-lactams). However, there are growing resistance or safety concerns with the available oral agents listed for outpatients with CAP in the updated American Thoracic Society (ATS)/Infectious Diseases Society of America (IDSA) CAP guidelines, especially among patients with comorbidities or notable risk factors for resistant pathogens. Given the need for alternative oral agents to macrolides, fluoroquinolones, and beta-lactams for adult outpatients with CAP, this review summarizes the literature on the use of oral tetracyclines (i.e., doxycycline, minocycline, and omadacycline) for this indication. As part of this review, we described their mechanism of action, common mechanisms of resistance, susceptibility profiles against common CAP pathogens, pharmacokinetics, pharmacodynamics, clinical data, and safety. The intent of the review is to highlight the important considerations when deciding between doxycycline, minocycline, and omadacycline for an adult outpatient with CAP in situations in which use of an oral tetracycline is warranted.

Adherence to Treatment Guideline Improves Patient Outcomes in a Prospective Cohort of Adults Hospitalized for Community-Acquired Pneumonia

Background

Understanding local epidemiology and etiologies of community-acquired pneumonia in hospitalized patients is crucial for determining the appropriateness of treatment guidelines. We aim to determine the etiologies, severity, and outcomes in adults hospitalized for community-acquired pneumonia and to study the impact of empirical antibiotic therapy on patient outcomes.

Methods

We performed a prospective observational cohort study involving adults hospitalized for community-acquired pneumonia in Hong Kong. Sputum, nasopharyngeal aspirate, blood, and urine were collected for bacterial culture, molecular tests for detection of viruses and atypical pathogens, and antigen tests. Multivariable logistic regression model and Cox proportional hazard models were performed to determine independent factors associated with prolonged hospitalization and mortality.

Results

From February 2017 to July 2018, 258 patients were enrolled. The median age was 73 (interquartile range, 61-80) years, 66% were male, 57% had underlying chronic illnesses, 13% had CURB-65 score ≥3, and 10% had higher 1-year mortality. Pathogens were identified in 45% of patients; 20% had viral, 15% had bacterial, and 9% had polymicrobial pneumonia. Streptococcus pneumoniae (12%), influenza virus (12%), and Mycoplasma pneumoniae (1.2%) were the most common bacterial, viral, and atypical pathogens, respectively. Nonadherence to local empirical antibiotic treatment guidelines (primarily recommending beta-lactam and doxycycline) was observed in 25% and was independently associated with prolonged hospitalization (≥7 days) and higher mortality, after adjustment for age, underlying chronic illness, and disease severity.

Conclusions

Adherence to treatment guidelines was associated with shorter hospitalization and improved survival. We provided evidence for the use of doxycycline for coverage of atypical pathogens in nonsevere pneumonia.

Deconstructing the Chlamydial Cell Wall

The evolutionary separated Gram-negative Chlamydiales show a biphasic life cycle and replicate exclusively within eukaryotic host cells. Members of the genus Chlamydia are responsible for many acute and chronic diseases in humans, and Chlamydia-related bacteria are emerging pathogens. We revisit past efforts to detect cell wall material in Chlamydia and Chlamydia-related bacteria in the context of recent breakthroughs in elucidating the underlying cellular and molecular mechanisms of the chlamydial cell wall biosynthesis. In this review, we also discuss the role of cell wall biosynthesis in chlamydial FtsZ-independent cell division and immune modulation. In the past, penicillin susceptibility of an invisible wall was referred to as the "chlamydial anomaly." In light of new mechanistic insights, chlamydiae may now emerge as model systems to understand how a minimal and modified cell wall biosynthetic machine supports bacterial cell division and how cell wall-targeting beta-lactam antibiotics can also act bacteriostatically rather than bactericidal. On the heels of these discussions, we also delve into the effects of other cell wall antibiotics in individual chlamydial lineages.

Autophagy Limits Inflammasome During Chlamydia pneumoniae Infection

Autophagy can either antagonize or promote intracellular bacterial growth, depending on the pathogen. Here, we investigated the role of autophagy during a pulmonary infection with the obligate intracellular pathogen, Chlamydia pneumoniae (CP). In mouse embryonic fibroblasts (MEFs) or macrophages, deficiency of autophagy pathway components led to enhanced CP replication, suggesting that autophagy exerts a bactericidal role. However, in vivo, mice with myeloid-specific deletion of the autophagic protein ATG16L1 suffered increased mortality during CP infection, neutrophilia, and increased inflammasome activation despite no change in bacterial burden. Induction of autophagy led to reduced CP replication in vitro, but impaired survival in CP-infected mice, associated with an initial reduction in IL-1β production, followed by enhanced neutrophil recruitment, defective CP clearance, and later inflammasome activation and IL-1β production, which drove the resulting mortality. Taken together, our data suggest that a delicate interplay exists between autophagy and inflammasome activation in determining the outcome of CP infection, perturbation of which can result in inflammatory pathology or unrestricted bacterial growth.

Diagnosis and treatment of community-acquired pneumonia in adults: 2016 clinical practice guidelines by the Chinese Thoracic Society, Chinese Medical Association

Community‐acquired pneumonia (CAP) in adults is an infectious disease with high morbidity in China and the rest of the world. With the changing pattern in the etiological profile of CAP and advances in medical techniques in diagnosis and treatment over time, Chinese Thoracic Society of Chinese Medical Association updated its CAP guideline in 2016 to address the standard management of CAP in Chinese adults. Extensive and comprehensive literature search was made to collect the data and evidence for experts to review and evaluate the level of evidence. Corresponding recommendations are provided appropriately based on the level of evidence. This updated guideline covers comprehensive topics on CAP, including aetiology, antimicrobial resistance profile, diagnosis, empirical and targeted treatments, adjunctive and supportive therapies, as well as prophylaxis. The recommendations may help clinicians manage CAP patients more effectively and efficiently. CAP in pediatric patients and immunocompromised adults is beyond the scope of this guideline. This guideline is only applicable for the immunocompetent CAP patients aged 18 years and older. The recommendations on selection of antimicrobial agents and the dosing regimens are not mandatory. The clinicians are recommended to prescribe and adjust antimicrobial therapies primarily based on their local etiological profile and results of susceptibility testing, with reference to this guideline.

Azithromycin and Doxycycline Attenuation of Acanthamoeba Virulence in a Human Corneal Tissue Model

Background

Amoebic keratitis is a potentially blinding eye infection caused by ubiquitous, free-living, environmental acanthamoebae, which are known to harbor bacterial endosymbionts. A Chlamydia-like endosymbiont has previously enhanced Acanthamoeba virulence in vitro. We investigated the potential effect of Acanthamoeba-endosymbiont coinfection in a human corneal tissue model representing clinical amoebic keratitis infection.

Methods

Environmental and corneal Acanthamoeba isolates from the American Type Culture Collection were screened for endosymbionts by amplifying and sequencing bacterial 16S as well as Chlamydiales-specific DNA. Each Acanthamoeba isolate was used to infect EpiCorneal cells, a 3-dimensional human corneal tissue model. EpiCorneal cells were then treated with azithromycin, doxycycline, or control medium to determine whether antibiotics targeting common classes of bacterial endosymbionts attenuated Acanthamoeba virulence, as indicated by decreased observed cytopathic effect and inflammatory biomarker production.

Results

A novel endosymbiont closely related to Mycobacterium spp. was identified in Acanthamoeba polyphaga 50495. Infection of EpiCorneal cells with Acanthamoeba castellanii 50493 and A. polyphaga 50372 led to increased production of inflammatory cytokines and cytopathic effects visible under microscopy. These increases were attenuated by azithromycin and doxycycline.

Conclusions

Our findings suggest that azithromycin and doxycycline may be effective adjuvants to standard antiacanthamoebal chemotherapy by potentially abrogating virulence-enhancing properties of bacterial endosymbionts.

Mast cells play an important role in chlamydia pneumoniae lung infection by facilitating immune cell recruitment into the airway

Mast cells are known as central players in allergy and anaphylaxis, and they play a pivotal role in host defense against certain pathogens. Chlamydia pneumoniae is an important human pathogen, but it is unclear what role mast cells play during C. pneumoniae infection. We infected C57BL/6 (wild-type [WT]) and mast cell-deficient mice (Kit(W-sh/W-sh) [Wsh]) with C. pneumoniae. Wsh mice showed improved survival compared with WT mice, with fewer cells in Wsh bronchoalveolar lavage fluid (BALF), despite similar levels of cytokines and chemokines. We also found a more rapid clearance of bacteria from the lungs of Wsh mice compared with WT mice. Cromolyn, a mast cell stabilizer, reduced BALF cells and bacterial burden similar to the levels seen in Wsh mice; conversely, Compound 48/80, a mast cell degranulator, increased the number of BALF cells and bacterial burden. Histology showed that WT lungs had diffuse inflammation, whereas Wsh mice had patchy accumulations of neutrophils and perivascular accumulations of lymphocytes. Infected Wsh mice had reduced amounts of matrix metalloprotease-9 in BALF and were resistant to epithelial integral membrane protein degradation, suggesting that barrier integrity remains intact in Wsh mice. Mast cell reconstitution in Wsh mice led to enhanced bacterial growth and normal epithelial integral membrane protein degradation, highlighting the specific role of mast cells in this model. These data suggest that mast cells play a detrimental role during C. pneumoniae infection by facilitating immune cell infiltration into the airspace and providing a more favorable replicative environment for C. pneumoniae.

Atypical pneumonia

PURPOSE OF REVIEW

We present the key advances in the infections that clinicians conventionally associate with atypical pneumonia: legionellosis, Mycoplasma pneumonia, Chlamydophila species pneumonia and Q fever.

RECENT FINDINGS

There have been significant developments in molecular diagnosis to include Mycoplasma pneumoniae and Chlamydophila pneumoniae in multiplex PCR of respiratory specimens. There are diagnostic challenges in distinguishing carriage from infection, which is recognized in C. pneumoniae and now also evident in M. pneumoniae. Macrolide-resistant M. pneumoniae has emerged in Asia. There are new antimicrobials on the horizon in the ketolide class with activity against typical and atypical pathogens and useful empirical agents.

SUMMARY

There are few advances in our knowledge of the epidemiology of atypical pathogens or the effectiveness of antimicrobial therapy--empirical or pathogen specific. However, if molecular testing becomes widely implemented, there will be an increased understanding of the epidemiology and presentation of atypical pneumonia and a shift to more targeted antimicrobial therapy.

Chlamydia genomics: providing novel insights into chlamydial biology

Chlamydiaceae are obligate intracellular pathogens that have successfully evolved to colonize a diverse range of hosts. There are currently 11 described species of Chlamydia, most of which have a significant impact on the health of humans or animals. Expanding chlamydial genome sequence information has revolutionized our understanding of chlamydial biology, including aspects of their unique lifecycle, host-pathogen interactions, and genetic differences between Chlamydia strains associated with different host and tissue tropisms. This review summarizes the major highlights of chlamydial genomics and reflects on the considerable impact these have had on understanding the biology of chlamydial pathogens and the changing nature of genomics tools in the 'post-genomics' era.

Chlamydia pneumoniae infection in mice induces chronic lung inflammation, iBALT formation, and fibrosis

Chlamydia pneumoniae (CP) lung infection can induce chronic lung inflammation and is associated with not only acute asthma but also COPD exacerbations. However, in mouse models of CP infection, most studies have investigated specifically the acute phase of the infection and not the longer-term chronic changes in the lungs. We infected C57BL/6 mice with 5×10⁵ CP intratracheally and monitored inflammation, cellular infiltrates and cytokine levels over time to investigate the chronic inflammatory lung changes. While bacteria numbers declined by day 28, macrophage numbers remained high through day 35. Immune cell clusters were detected as early as day 14 and persisted through day 35, and stained positive for B, T, and follicular dendritic cells, indicating these clusters were inducible bronchus associated lymphoid tissues (iBALTs). Classically activated inflammatory M1 macrophages were the predominant subtype early on while alternatively activated M2 macrophages increased later during infection. Adoptive transfer of M1 but not M2 macrophages intratracheally 1 week after infection resulted in greater lung inflammation, severe fibrosis, and increased numbers of iBALTS 35 days after infection. In summary, we show that CP lung infection in mice induces chronic inflammatory changes including iBALT formations as well as fibrosis. These observations suggest that the M1 macrophages, which are part of the normal response to clear acute C. pneumoniae lung infection, result in an enhanced acute response when present in excess numbers, with greater inflammation, tissue injury, and severe fibrosis.

Does empiric therapy for atypical pathogens improve outcomes for patients with CAP?

The present controversy regarding the need to cover atypical pathogens in the empiric therapy of community-acquired pneumonia is related to several issues, including the relevance of terminology, imprecise diagnostic methods, and perceived contradictory results of published evidence. Studies evaluating the time to clinical recovery and the use of earlier endpoints for evaluation suggest that appropriate therapy provides a benefit if an atypical pathogen is a pathogen. Because recent surveillance studies suggest these pathogens are common and until there is the availability of accurate, cost-effective, and easily interpreted laboratory tests to provide the etiologic diagnosis at the time of point of care, empiric therapy of atypical pathogens is supported.

[Microbiological diagnosis of infections due to Chlamydia spp. and related species]

Until recently the number of completed genomes belonging to Chlamydia trachomatis was very low, despite its importance in Public Health. Now, there are currently sixty-six completed genomes of C.trachomatis sequenced in different parts of the world. This genomic revolution has helped in understanding its biology, as well as improved the sensitivity and specificity in the diagnosis, and the development of epidemiological tools, not only for in C.trachomatis, but also for related species such as C.pneumoniae and C.psittaci. The diagnosis based on cell culture, serology and microimmunofluorescence is gradually being replaced by molecular techniques based on PCR or real-time PCR. This is because these molecular tests do not have cross-reactions problems and the procedures are easily standardised between laboratories. Moreover, molecular epidemiology tools described recently, such as Multi-Locus Sequence Typing (MLST) and Variable Number Tandem Repeat (VNTR), have increased our knowledge on local and global epidemiology. This article focuses on the impact of the genomics advances achieved over the last few years as applied to the diagnosis, epidemiology and biology of the family Chlamydiaceae family and related species.

Chlamydia pneumoniae: modern insights into an ancient pathogen

Chlamydia pneumoniae is an enigmatic human and animal pathogen. Originally discovered in association with acute human respiratory disease, it is now associated with a remarkably wide range of chronic diseases as well as having a cosmopolitan distribution within the animal kingdom. Molecular typing studies suggest that animal strains are ancestral to human strains and that C. pneumoniae crossed from animals to humans as the result of at least one relatively recent zoonotic event. Whole genome analyses appear to support this concept - the human strains are highly conserved whereas the single animal strain that has been fully sequenced has a larger genome with several notable differences. When compared to the other, better known chlamydial species that is implicated in human infection, Chlamydia trachomatis, C. pneumoniae demonstrates pertinent differences in its cell biology, development, and genome structure. Here, we examine the characteristic facets of C. pneumoniae biology, offering insights into the diversity and evolution of this silent and ancient pathogen.