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The Journal of Pharmacy Technology: JPT: Official Publication of the Association of Pharmacy Technicians logoLink to The Journal of Pharmacy Technology: JPT: Official Publication of the Association of Pharmacy Technicians
. 2025 Aug 31:87551225251366324. Online ahead of print. doi: 10.1177/87551225251366324

Doxycycline for Legionella Pneumonia: Expanding Treatment Horizons Through a Case Series and Narrative Review

M Gabriela Cabanilla 1,2,✉, Aileen C Scheibner 2, Jorge R Mera 1
PMCID: PMC12399582  PMID: 40901380

Abstract

Background: Legionella pneumonia is a significant cause of community-acquired pneumonia that often requires timely and effective treatment. While fluoroquinolones and macrolides are the recommended first-line therapies, doxycycline offers an alternative with favorable pharmacokinetics, safety, and minimal drug-drug interactions. Methods: We describe three hospitalized patients with Legionella pneumonia who received doxycycline monotherapy.Clinical outcomes, including symptom resolution and survival, were assessed at 60 days. A literature review was also performed for studies published between 1980 and 2025 that evaluated doxycycline for Legionella infection. Results: All three patients achieved clinical improvement with doxycycline monotherapy, with resolution of presenting symptoms and survival at 60 days post-hospitalization. The literature review identified limited clinical data on doxycycline for Legionella pneumonia. In vitro data suggested that doxycycline may have lower bactericidal activity than fluoroquinolones, although its pharmacological profile and tolerability support its consideration in select cases. Conclusion: Doxycycline monotherapy was associated with favorable outcomes in three cases of Legionella pneumonia. Although the evidence remains sparse, doxycycline may represent a viable alternative when first-line therapy is contraindicated. Further research is required to define its role in the treatment of Legionella pneumonia.

Keywords: doxycycline, pneumonia, legionnaire’s disease, Legionella, anti-bacterial agents

Introduction

Community-acquired pneumonia (CAP) is a leading cause of hospitalization and death among adults in the United States. Approximately 1 million adults in the United States are hospitalized for pneumonia every year, and 50 000 die of this disease. 1 Despite a comprehensive diagnostic workup, an etiologic diagnosis can only be achieved in less than 38% of patients, 2 with the major bacterial pathogens being Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Legionella species, Chlamydia pneumoniae, and Moraxella catarrhalis. 3 Legionella is an important and often underdiagnosed CAP pathogen in both immunocompetent and immunocompromised patients, accounting for up to 15% of patients requiring hospitalization for CAP.4 -6 According to the US Centers for Disease Control (CDC), nearly 10 000 cases of Legionella were reported in 2018, with reported cases ranging from approximately 8000 to 9000 annually by 2022. 7 However, the true incidence is likely underestimated owing to variations in clinical suspicion, geographical incidence, diagnostic methods, and reporting practices.

The reported incidence varies geographically, with the highest case counts reported in the East North Central, Middle Atlantic, and New England census divisions. In 2018 and 2019, Ohio, New York, Pennsylvania, Michigan, and Illinois reported the highest number of confirmed cases. 7 The vast majority of these cases (96.9%) were diagnosed using urinary antigen tests, which detect only L. pneumophila serogroup 1, while culture was performed in only 4.4% of the cases. Among culture-confirmed cases, 67.7% were due to L. pneumophilia, of which 60.8% were identified as serogroup 1. 7 Diagnostic sensitivity varies by method, 8 and although serogroup 1 is the predominant clinically recognized cause of Legionnaires’ disease in the United States, these data suggest that the true distribution of species and serogroups may be broader than the current surveillance reflects.

The clinical presentation of Legionella pneumonia is variable, ranging from mild to severe respiratory illnesses, often mimicking other CAP etiologies. In severe cases, Legionella pneumonia can lead to respiratory failure, septic shock, and death, if not promptly diagnosed and treated. 9 Current standard treatments include fluoroquinolones or macrolides as first-line agents and doxycycline as an alternative. 3 However, there is limited evidence regarding the efficacy of doxycycline monotherapy for the treatment of Legionella pneumonia, although it offers several advantages, including high oral bioavailability, excellent intracellular penetration, and a favorable safety profile with minimal drug interactions. In this case series and narrative review, the successful use of doxycycline monotherapy as a treatment option for Legionella pneumonia was described in 3 patients, and the published literature on the subject from 1997 to 2025 was reviewed.

Methods

Case Series

A retrospective review was conducted to identify patients with confirmed Legionella pneumonia treated with doxycycline between January 1, 2019, and July 15, 2023, at an academic medical center in Albuquerque, New Mexico, United States. Patients were identified through a data pull from the Tricore Reference Laboratories for positive Legionella urinary antigen tests during the study period. Fourteen patients were identified. Only 3 of the 14 patients were treated with doxycycline monotherapy per review of the electronic medical records (EMR). These 3 patients were included for further analysis. The EMR was retrospectively reviewed to gather clinical data and outcomes of these patients.

This study was exempt from Institutional Review Board (IRB) approval. According to the University of New Mexico Health Sciences Center IRB policy, formal IRB approval is not required for studies involving 3 or fewer patients.

Literature Review

This narrative review was conducted using a structured approach modeled on PRISMA principles, although it was not a systematic review. The SCOPUS and PubMed databases were searched for relevant primary literature published in English or Spanish between 1980 and 2025. The following key search terms were used: doxycycline, Legionella, and Legionella pneumonia. Studies were screened based on their titles and abstracts. Studies were included if they focused on the treatment of Legionella pneumonia with doxycycline in adults (≥ 18 years). Controlled and uncontrolled clinical studies were included. Case reports or series were included if doxycycline was used as definitive therapy.

Studies were excluded if they were unrelated to Legionella pneumonia, did not discuss doxycycline, or lacked clinical or treatment outcomes (eg, in vitro or etiological studies). Editorials, systematic reviews, narrative reviews, and studies in which full-text access was unavailable were also excluded.

Case Reports

A summary of the demographics, comorbidities, duration of doxycycline treatment, severity of Legionella pneumonia, and outcomes for the 3 patient cases described below are provided in Table 1.

Table 1.

Patient Demographics, Doxycycline Duration, and Outcomes.

Age, in years Sex Comorbid conditions Hospital LOS ICU LOS Extrapulmonary involvement Doxycycline duration Outcome
PT. 1 23 M Cerebral palsy, seizure disorder, cortical visual impairment 21 days 21 days No 5 days Recovered; alive at 60 days
PT. 2 73 M Stroke, left ventricular thrombus, HIV 4 days NA No 10 days Recovered; alive at 60 days
PT. 3 56 M ESRD with kidney transplantation, BPH, OSA 12 days NA No 21 days Recovered; alive at 60 days
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Abbreviations: BPH, benign prostate hyperplasia; ESRD, end-stage renal disease; HIV, human immunodeficiency virus; ICU, intensive care unit; LOS, length of stay; M, male; NA, not applicable; OSA, obstructive sleep apnea; PT, patient.

Case 1

A 23-year-old male with cerebral palsy complicated by scoliosis and gastrostomy tube dependence, hip dislocation, quadriplegia, seizure disorder, and visual impairment presented to the emergency department (ED) with increased lethargy and worsening cough. The patient’s caregiver noted progressively increased coughing for approximately 1 week prior to admission, bleeding per rectum, and constipation in the previous days. The caregiver reported multiple recent sick contacts with influenza pneumonia at the patient’s skilled nursing facility (SNF). As these symptoms progressed, the patient required 1 L of oxygen via a nasal cannula prior to presentation.

In the ED, his oxygen requirement increased to 10 L via a facemask. On presentation, the patient was hypothermic (29°C), hypotensive (80/60 mm Hg), slightly tachycardic (90 beats per minute), and tachypneic (25 respirations per minute). His hypotension improved (blood pressure increased to 95/51 mm Hg) with 1 L of normal saline. Admission laboratories were remarkable for anemia (hemoglobin 5.4 g/dL), thrombocytopenia (platelets 105 × 103/µL), hypoglycemia (blood glucose 33 mg/dL), hyperkalemia (potassium 5.7 mmol/L), and hypoalbuminemia (albumin 2.6 g/dL). The patient did not show leukocytosis on admission. On physical examination, he was lethargic and his lungs had coarse sounds and crackles. Chest radiography revealed multifocal pneumonia. The patient met the systemic inflammatory response syndrome (SIRS) criteria, for which he was empirically treated with cefepime and vancomycin, with bacterial pneumonia as a suspected source of infection. There was also a concern for lower gastrointestinal bleeding, supported by a positive guaiac stool test. He received 2 units of blood yet remained hypotensive in the ED.

The patient was admitted to the medical intensive care unit (ICU) where vasopressors were initiated. The patient was promptly intubated when hypoxemia worsened. Post-intubation chest radiography revealed worsening pneumonia. Sputum cultures were obtained and finalized without growth. A viral respiratory panel and Streptococcus pneumoniae antigen tests were also conducted and yielded negative results. The only positive infectious diseases test was the urine Legionella antigen test, leading to the diagnosis of severe Legionella pneumonia. Vancomycin and cefepime were discontinued after 3 days of therapy. Monotherapy with doxycycline 100 mg twice daily was initiated rather than macrolide or fluoroquinolone therapy because of electrolyte abnormalities and the risk of QTc prolongation with other QTc prolonging agents. The patient initially received intravenous (IV) doxycycline, which was switched to the oral route once he was able to tolerate tube feeds via an existing gastrostomy tube. He received 2 days of IV doxycycline before transitioning to oral administration. Oral doses were spaced at least 2 hours apart from the tube feeds to minimize potential absorption issues, and no complications were encountered. He completed a total of 5 days of doxycycline therapy based on clinical improvement. No additional antibiotics were administered following completion of doxycycline therapy. Atypical pathogens, such as Legionella, are intrinsically resistant to vancomycin and cefepime; thus, these agents were not considered effective and were excluded from the treatment duration calculation. The patient eventually underwent tracheostomy with resolution of the pneumonia on follow up chest radiography 12 days later. After 21 days of hospitalization, the patient was discharged to a SNF and remained alive at 60 days.

Case 2

A 73-year-old male with a history of ischemic stroke with residual fluctuating expressive aphasia, left ventricular thrombus on anticoagulation, and well-controlled stage II HIV infection (most recent CD4 count was 383 cells/mm3) presented to the ED with altered mental status. Other associated symptoms included decreased appetite, gait difficulties, generalized weakness, progressive lethargy, and 2 episodes of non-bilious non-bloody emesis, which prompted the patient’s partner to call an ambulance.

Upon arrival at the ED, a code stroke was activated. Subsequent computed tomography (CT) and magnetic resonance imaging (MRI) of the brain were not suggestive of stroke. The patient was febrile (38.4°C), hypertensive (157/84 mm Hg), tachypneic (31 respirations per minute), and hypoxic (oxygen saturation of 91% on 2 L via a nasal cannula). Admission laboratories were remarkable for leukocytosis (white blood cell count 13.8 × 103/µL), anemia (hemoglobin 11.8 g/dL), hyponatremia (sodium 131 mmol/L), hypokalemia (potassium 3.3 mmol/L), and an elevated lactate (2.6 mmol/L) and international normalized ratio (INR, 4.12). Physical examination was unremarkable except for decreased breath sounds in the left lower lobe, aphasia, intermittent command following, and decreased strength in the bilateral upper and lower extremities. Chest radiography revealed left lower lobe opacities, consistent with pneumonia.

The patient was admitted to the hospital with concerns of meningitis and pneumonia, for which he was empirically treated with IV ampicillin, ceftriaxone, vancomycin, and acyclovir. Lumbar puncture was deferred because of his elevated INR. The encephalopathy resolved 1 day after hospital admission. Given the lack of symptoms and imaging findings associated with meningitis, antimicrobials were changed to focus on the empiric treatment of CAP with ampicillin/sulbactam and oral doxycycline. Importantly, antimicrobial coverage for Legionella was not initiated until this regimen change. Doxycycline was selected over fluoroquinolones and macrolides because the patient had a reported allergy to levofloxacin and was receiving other medications with the potential for QTc prolongation. The patient’s antiretroviral regimen did not pose significant interaction risks with doxycycline. The viral respiratory panel and S. pneumoniae antigen test were negative. A sputum culture was not obtained as the patient was unable to produce a sample. Legionella pneumonia was ultimately diagnosed based on a positive urine Legionella antigen test. The patient was discharged home with a 10-day course of oral doxycycline with satisfactory improvement based on a follow-up visit with his primary care provider at the end of treatment. The patient remained alive at 60 days.

Case 3

A 56-year-old male with end-stage renal disease and restored renal function after kidney transplantation more than 1 year prior to admission, benign prostate hyperplasia, and obstructive sleep apnea presented to the ED with abdominal pain, nausea, vomiting, and dysuria. The patient reported fever and chills that started a few days prior to presentation. He noted foul-smelling urine, decreased urine output, and loose stools after symptom onset.

In the ED, a urinary tract infection workup revealed pyelonephritis complicated by E. coli bacteremia. Vital signs were normal and stable on admission, with laboratories remarkable for leukocytosis (white blood cells 14 × 103/µL), hyponatremia (sodium 131 mmol/L), hypokalemia (potassium 2.9 mmol/L), hypoalbuminemia (albumin 2.2 g/dL), as well as elevated blood urea nitrogen (75 mg/dL) and serum creatinine (4.03 mg/dL).

The patient was admitted to the hospital and treated with IV ceftriaxone, with prompt resolution of his symptoms. On day 7 of hospital admission, the patient’s white blood cell count revealed up-trending leukocytosis. The white blood cell count increased to 25.7 × 103/µL from 16.4 × 103/µL 2 days prior while on ceftriaxone. The patient was on room air, afebrile, and clinically stable. Leukocytosis prompted the investigation of concomitant infections. Chest radiography revealed multifocal pneumonia. Physical examination revealed decreased breath sounds in the lung bases. Given the immunocompromised state of the patient, a broad infectious workup was performed to rule out nosocomial and opportunistic pathogens. Antibiotics were also broadened at that time, with the discontinuation of ceftriaxone and initiation of IV cefepime and oral doxycycline. Doxycycline was selected due to existing drug-drug interactions and the risk of QTc prolongation with other medications. Sputum culture was collected and finalized without growth. Endemic fungal serology and viral respiratory panel tests were negative. Legionella pneumonia was diagnosed when the urine Legionella antigen test returned positive results. The patient was discharged to complete a 21-day course of oral doxycycline given his immunocompromised status. He experienced no complications, as confirmed during a follow-up clinic visit with an infectious diseases provider at the end of the treatment. The patient remained alive at 60 days.

Discussion

The Infectious Disease Society of America (IDSA) practice guidelines recommend doxycycline monotherapy as an alternative CAP therapy for patients who do not require hospitalization or for hospitalized patients who have contraindications to both macrolides and fluoroquinolones. 3 These recommendations are based on sparse evidence, with few randomized clinical studies demonstrating positive results when doxycycline was used for CAP treatment that required hospitalization.10 -15 Despite this paucity of data, doxycycline is often considered as an appropriate therapy for the treatment of Legionella pneumonia.3,16

Our literature search yielded 67 studies, of which 61 were excluded for reasons detailed in Figure 1. The key findings of this narrative review are summarized in Table 2. A case report that ultimately utilized dual coverage with doxycycline and moxifloxacin in a complicated case of Legionella pneumonia was identified. 17 Furthermore, only 5 studies have quantified the number of Legionella cases treated with doxycycline. One was a single-center retrospective analysis in which only 12 of 160 patients received doxycycline for the treatment of Legionella pneumonia. 18 The second was a prospective, randomized trial, in which < 1% of the enrolled patients (n = 414) were ultimately diagnosed with Legionella and treated with doxycycline. 13 The third was a retrospective observational study examining combination therapy for CAP, in which 6 of 27 patients (22.2%) with Legionella received beta-lactam plus doxycycline compared to 24 of 90 patients (26.7%) who received beta-lactam plus a macrolide, with comparable clinical outcomes between groups. 19 The fourth study was a multicenter, point-prevalence study of 2564 immunocompetent adults hospitalized with CAP, which reported that 27% of the patients received empiric doxycycline, However, the specific outcomes for Legionella cases treated with doxycycline were not described. 20 The fifth study was a retrospective cohort of 642 patients with Legionella pneumonia that evaluated the impact of adequate empiric therapy on outcomes, but did not specify the number of patients who received doxycycline. 21

Figure 1.

Screening and selection criteria for researching doxycycline treatment in Legionella pneumonia infections.

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Screening and selection process for articles on doxycycline therapy in Legionella pneumonia.

Table 2.

Summary of Key Findings From the Literature Review on Doxycycline in Legionella Pneumonia Management.

Author (Year) Design Population characteristics Doxycycline duration and route of administration Adverse events due to doxycycline Relevant findings
Deng et al 17 Case report 52-year-old male admitted to the ICU with hypoxic respiratory failure diagnosed with Legionella via mNGS Total duration of antimicrobial therapy and route not described
Day 1:
MXF + DOX + IMP
Day 3:
MXF + DOX		 None described Discharged on day 43 after hospital course complicated by septic shock, mechanical ventilation, rhabdomyolysis, and CRRT
Beaty et al 18 Retrospective cohort Hospitalized patients (n = 160) with Legionella pneumonia confirmed by urine antigen, serum antibodies, or culture
Mean PSI score = 114
12 (7.5%) patients received DOX		 Not described None described 25% (n = 40) of patients required ICU admission
10.6% (n = 17) of patients required invasive mechanical ventilation
7.5% (n = 12) of patient died during hospital admission
Allgaier et al 21 Retrospective cohort 642 patients with Legionella pneumonia, 112 (17.4%) were immunosuppressed
495 (77%) were empirically treated with either AZT, LEV, CIP, MXF, CLA, ERY or DOX
Number of patients that received DOX not specified		 Not described
Route: allowed either IV or PO routes of administration but exact proportions were not described		 None described Those with inadequate empiric therapy a had higher rates of ICU admission (30.6% vs 16.7%, P = 0.001), late mechanical ventilation (21.6% vs 13.4%, P = 0.02), and death (13.6% vs 5.5%, P < 0.001) compared to those with adequate therapy
Carugati et al 20 Multicenter, point-prevalence 2564 immunocompetent adults hospitalized with CAP
899 (35.1%) patients had a positive Legionella urinary antigen
Doxycycline was empirically started in 27% of patients		 Not described None described Patient outcomes of those specifically diagnosed with Legionella or treated with DOX were not described
Teh et al 19 Retrospective cohort 858 patient episodes with CAP and combination therapy
178 (20.7%) received BLA + DOX
680 (79.2%) received BLA + MAC
For Legionella specifically:
6 of 27 patients (22.2%) in BLA + DOX group
24 of 90 patients (26.7%) in BLA + MAC group		 Not described None described Those treated with BLA + DOX had shorter hospital LOS compared to BLA + MAC (P < 0.001)
No difference in 30-day mortality between the 2 groups for atypical pathogens, including Legionella (3.7% for BLA + DOX vs 3.3% for BLA + MAC, P = 1.0)
Time to clinical stability was similar between groups (P = 0.11)
Concluded that DOX + BLA is an appropriate alternative to MAC for treatment atypical pathogens, including Legionella
Norrby et al 13 Prospective, randomized, double-blind 414 adult patients (inpatients and outpatients) across 20 centers in Denmark, Finland, Iceland, Sweden, and Norway with chest radiography-verified pneumonia
209 (50.5%) patients received DOX
Legionella spp. identified in 9 patients
Of the patients with Legionella, 4 patients received DOX		 10 days
Route: PO only		 71 (33.9%) patients experienced adverse reactions to DOX with the most common adverse effect being nausea, diarrhea, or vomiting (42 patients)
2 (0.9%) patients had serious adverse effects related to DOX: syncope (case 1), UV-light sensitivity (case 2)		 The efficacy and safety outcomes specific to patients diagnosed with Legionella pneumonia were not reported
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Abbreviations: AZT, azithromycin; BLA, beta-lactam antibiotic; CAP, community-acquired pneumonia; CCRT, continuous renal replacement therapy; CIP, ciprofloxacin; CLA, clarithromycin; DOX, doxycycline; ERY, erythromycin; ICU, intensive care unit; IMP, imipenem; LEV, levofloxacin; LOS, length of stay; MAC, macrolide; mNGS, metagenomic next-generation sequencing; MXF, moxifloxacin; PSI, pneumonia severity index; UV, ultraviolet.

a

Allgaier et al 21 defined inadequate empiric therapy as anything other than a macrolide, fluoroquinolone, or doxycycline given in the first 2 days of hospitalization.

Larger studies on Legionella pneumonia treatment have grouped doxycycline with fluoroquinolones and macrolides,20,21 which makes it difficult to discern the true frequency and efficacy of doxycycline monotherapy. Confirming the real-world efficacy of doxycycline is important given that studies evaluating the in vitro susceptibility of Legionella species have demonstrated higher minimum inhibitory concentrations for doxycycline than for fluoroquinolones (most active) and macrolides.22,23 This may be due to the more rapid bactericidal activity of fluoroquinolones than that of doxycycline. 24

Doxycycline may offer clinical advantages over other classes of antibiotics for the treatment of Legionella pneumonia, despite its slower bactericidal activity. It has favorable pharmacokinetic properties, including 90% to 100% oral bioavailability, excellent penetration into respiratory tissues, and in vitro activity against Legionella species.25 -28 Doxycycline is approved and widely used in adults, with an excellent safety profile. 28 No dose adjustments are required for renal impairment, and clinically significant drug-drug interactions are limited given that doxycycline is not metabolized by cytochrome P450 enzymes. 28 Its most common adverse effects are gastrointestinal, with photosensitivity and pediatric tooth discoloration in children under 8 years of age (which has now been largely disproven), 29 are notable, but infrequent concerns. 30

Compared with fluoroquinolones and macrolides, doxycycline carries a significantly lower risk of Clostridioides difficile infection (CDI). A meta-analysis that included 5 studies comparing antimicrobial exposure to no antimicrobial exposure found that fluoroquinolones were within the group of antibiotics that had the largest impact on the risk of CDI. 31 Macrolides had a lower impact on CDI risk than fluoroquinolones, and doxycycline had no impact on CDI risk,31,32 further emphasizing its attractive safety profile. Despite these favorable characteristics, doxycycline monotherapy remains underutilized in clinical practice for the treatment of Legionella infections. Several factors may contribute to its underutilization, including clinical criteria inertia, strong emphasis on fluoroquinolones and macrolides, and concerns regarding its perceived lower bactericidal activity. However, recent infectious diseases literature increasingly recognizes that the distinction between bactericidal and bacteriostatic agents has limited clinical relevance in most settings, particularly when host immunity is intact. 33 Moreover, the role of doxycycline in CAP has historically been associated with outpatients or mild cases, which may bias prescribing decisions against its use in hospitalized patients, even when clinically appropriate. Although the risks associated with fluoroquinolone and macrolide therapies have been well documented,34 -37 differences in patient outcomes due to antimicrobial selection in the treatment of Legionella pneumonia have not been described.

The findings of this narrative review highlight the lack of data on doxycycline monotherapy for the treatment of Legionella pneumonia and demonstrate the need for further research in this area. This case series describes the successful use of doxycycline monotherapy as a definitive treatment in 2 immunocompromised and 1 immunocompetent patient with Legionella pneumonia. All 3 patients experienced complete resolution of symptoms without any complications or adverse effects associated with doxycycline use. These outcomes suggest that doxycycline may be a viable alternative to traditional fluoroquinolone- or macrolide-based regimens for the treatment of Legionella pneumonia, particularly in patients with contraindications to or intolerance to these agents.

However, the optimal duration of therapy for Legionella pneumonia remains unclear. Our patients received treatment durations of 5, 10, and 21 days, reflecting clinical variability. This range highlights the need for additional research to define the appropriate duration of doxycycline treatment, particularly in immunocompromised populations. It is also important to consider that macrolides have prolonged half-lives, and that both macrolides and fluoroquinolones exhibit post-antibiotic effects that may extend antimicrobial activity beyond the dosing period. As a result, a 5-day course of azithromycin may provide longer effective coverage than an equivalent duration of doxycycline.

While guidelines do not specify a fixed duration, most of the published data suggest 5 to 10 days of fluoroquinolones or macrolides for uncomplicated cases and up to 21 days in severe or immunocompromised patients.38 -41 Comparing the variable doxycycline duration in our series with these reference standards further supports the need for prospective studies to guide treatment duration. These findings should be interpreted as hypothesis generating rather than definitive evidence.

Conclusion

This exploratory case series and narrative review described positive clinical outcomes in 3 patients treated with doxycycline monotherapy for Legionella pneumonia. Despite its favorable pharmacokinetic properties and safety profile, doxycycline remains underutilized because of the limited clinical data supporting its use as a primary therapy. Although larger prospective studies are needed to better define its efficacy, treatment duration, and role in the guidelines, our findings suggest that doxycycline may be a reasonable alternative in patients with contraindications to macrolides or fluoroquinolones.

Acknowledgments

The authors would like to express their gratitude to the clinical teams at the University of New Mexico Hospital for their contributions to patient care. We also thank the biomedical librarians at the National Institutes of Health Library for their guidance and assistance with the literature search.

Footnotes

Author Contributions: MGC and JRM conceived the original idea. MGC collected data from electronic health records. JRM conducted the database search. MGC, ACS and JRM reviewed the articles identified through the literature search and wrote the manuscript. All authors discussed the results, reviewed, edited, and provided critical feedback on the manuscript, and approved the final draft.

Ethical Approval: This study was exempt from Institutional Review Board (IRB) approval. According to the University of New Mexico Health Sciences Center IRB policy, formal IRB approval is not required for studies involving 3 or fewer patients.

Data Sharing and Data Availability Statement: The data that supports the findings of this study as it relates to the case series section is not publicly available data and cannot be shared publicly because of privacy/ethical restrictions. Data are accessible upon approval by the University of New Mexico Health Sciences Center Institutional Review Board in accordance with institutional policy and the sensitive nature of the data (contact via email: hsc-hrpo@salud.unm.edu) for researchers who meet the criteria for access to confidential data. Individuals outside the institution would need to establish a data use agreement with the University of New Mexico Health Sciences Center Sponsored Project Office (contact via email: hsc-preaward@salud.unm.edu) to request the study data.

The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: MGC has received research funding from Merck & Co, Inc. for a separate study, as well as honoraria as an advisor. JRM has received research funding from Gilead Sciences, AbbVie, Inc., Abbott Diagnostics, and Cepheid for separate studies. No other authors have any financial disclosures to report.

Funding: The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD: M. Gabriela Cabanilla Inline graphic https://orcid.org/0000-0001-5402-0240

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