Campylobacter and Helicobacter species
MICROBIOLOGY
- Gram-negative microaerophilic bacteria with a curved bacillary appearance on Gram stain [Fig].
- Generally oxidase-positive.
- Growth requirements vary by species:
- C. jejuni grows optimally at approximately 37–42°C
- Invasive non-jejuni species may require lower incubation temperatures and specialized microaerobic conditions.
- Turn to separate modules for the following organisms:
- Covered in this module:
- Important non-jejuni Campylobacter human pathogens include C. coli and C. fetus; less commonly, C. upsaliensis, C. lari, C. concisus, and others.
- C. coli is principally enteric.
- C. fetus is notable for its invasive tendencies, including endovascular infection.
- Also, this species is a worldwide zoonosis, with C. fetus causing abortion in cattle and sheep.
- Helicobacter spp. closely related to Campylobacter (e.g., H. pylori, formerly C. pylori)
- H. cinaedi, H. fennelliae, H. pullorum, and H. canadensis have all been described as causing human illness.
- H. cinaedi is especially associated with bacteremia and recurrent cellulitis, frequently in immunocompromised individuals.
- Other Helicobacter spp. do not have a clearly established set of presentations because they are rare.
- Important non-jejuni Campylobacter human pathogens include C. coli and C. fetus; less commonly, C. upsaliensis, C. lari, C. concisus, and others.
CLINICAL
- This module emphasizes non-jejuni species associated with extraintestinal disease, particularly C. fetus and H. cinaedi.
- The typical incubation is 2-5 days for enteric Campylobacter infections.
- See C. jejuni module for information specific to this species
- Most prone to infection are children < 5 years and adults ≥ 65 years; pregnancy and immunocompromise increase severe disease risk.
- C. fetus is the non-jejuni species classically associated with invasive and endovascular disease.
- Rates for all human campylobacteriosis are estimated at 20/100,000 diagnosed per year; most cases are likely unreported, with the CDC estimating ~1.5 million cases/year in the U.S.
- Infections are acquired from ingesting contaminated undercooked meat or poultry (in most cases), water, and unpasteurized milk products.
- It may also be acquired from pets with diarrhea or by visiting a petting zoo or farm.
- Campylobacter is an important cause of traveler’s diarrhea, especially in Southeast Asia, where fluoroquinolone resistance rates are high.
- In the U.S., the CDC has reported persistent XDR strains in outbreak investigations
- CDC reports 303 laboratory-confirmed REPDBR01 infections in PulseNet (as of June 30, 2026).
- Three investigated outbreaks included 113 cases in 2016–18, 56 in 2019–21, and 3 in 2024; all were linked to pet-store puppies.
- CDC reports 303 laboratory-confirmed REPDBR01 infections in PulseNet (as of June 30, 2026).
- In the U.S., the CDC has reported persistent XDR strains in outbreak investigations
- C. fetus is the non-jejuni species classically associated with invasive and endovascular disease.
- Typical extra-intestinal Campylobacter and Helicobacter infections affect debilitated or immunocompromised hosts.[5]
- These extraintestinal infections can occur in immunocompetent hosts but are less common.
- Sexual transmission has been described, including clusters among MSM.
- Dx:
- Culture considerations:
- If attempting to culture C. fetus or other species from feces [rarely achieved], alert the micro lab for specialized requirements, such as 37°C requirements and media without cephalosporins.
- H. cinaedi may require prolonged blood-culture incubation, with a median time to detection of approximately 5 days.[19]
- Identification may require MALDI-TOF MS or molecular methods
- Diarrhea or enteric disease: culture-independent diagnostic tests are increasingly used for diagnosis.
- Stool testing[2] is recommended for diarrhea with fever, bloody/mucoid stool, severe cramping/tenderness, or sepsis.
- A broader evaluation is also appropriate in immunocompromised patients.
- Stool specimen: a stool sample is preferred over a rectal swab.
- Molecular assays are now preferred, generally more sensitive and faster than culture methods, but they may detect nucleic acid from nonviable organisms.
- Tests, however, will not yield susceptibility information.
- Culture: traditional method, but less sensitive than newer non-culture-based techniques.
- Required for susceptibility testing.
- Culture allows WGS, which is now the method of choice for public-health molecular subtyping.
- Serology: not useful for acute diagnosis.
- Stool antigen: largely supplanted by molecular assays.
- Molecular assays are now preferred, generally more sensitive and faster than culture methods, but they may detect nucleic acid from nonviable organisms.
- Stool testing[2] is recommended for diarrhea with fever, bloody/mucoid stool, severe cramping/tenderness, or sepsis.
- Culture considerations:
SITES OF INFECTION
- Campylobacter bloodstream infection:
- Relapse or reinfection occurred in 8% overall in a recent cohort and was substantially more frequent in patients with humoral immunodeficiency (18.3%).[5]
- Endovascular infections, especially by C. fetus, may cause endocarditis (rare) and mycotic aneurysms, especially of the abdominal aorta.
- Has a predilection to cause septic thrombophlebitis
- H. cinaedi
- Bacteremia also has a substantial risk of recurrence, with a 100-day cumulative incidence of 18.7% in a series of 168 patients.[14]
- Also a reported cause of culture-negative endocarditis.
- GI: Enteric disease occurs with several non-jejuni Campylobacter species; severity and duration vary by species.
- C. concisus, in a small study, was found to have caused mild but prolonged diarrhea.
- Meningitis/meningoencephalitis: C. fetus is a rare cause, described in neonates and adults.
- Cellulitis: Described particularly with H. cinaedi and C. fetus, usually in patients with underlying illness or immunocompromise.
TREATMENT
General comments
- In a large cohort study (reflecting isolates from 2009-2024 among tested bloodstream isolates), ciprofloxacin resistance was 73.8% and macrolide resistance 14.5%.
- Macrolide resistance was concentrated in C. coli (37%) compared with C. jejuni (6.3%) and C. fetus (6.9%)[5]
Gastrointestinal
- Uncommon, usually self-limited in normal hosts, non-C. jejuni infections.
- For C. jejuni, see this module for recommendations.
- Supportive care, rehydration (oral or IV).
- Zinc: WHO’s 2024 guidance suggests consideration in diarrhea up to age 10, using a 5-mg daily dose for acute watery/persistent diarrhea for up to 14 days.
- Antibiotics are usually not needed in normal hosts.
- Direct treatment data for non-jejuni enteritis are limited.
- Consider treatment for severe or prolonged infection or for patients at increased risk for severe disease.
- Macrolides: Do not rely on oral macrolide monotherapy for suspected invasive/systemic disease; obtain blood cultures and susceptibility testing.
- Preferred:
- Azithromycin 500 mg PO x 3 days
- Alternative:
- Fluoroquinolones are alternatives only when susceptibility is likely or known because resistance is common.
- Ciprofloxacin 500 mg twice daily PO x 3 days
- Fluoroquinolones are alternatives only when susceptibility is likely or known because resistance is common.
- Preferred:
- Direct treatment data for non-jejuni enteritis are limited.
Extra-intestinal infections
- Campylobacter non-jejuni infections:
- Because resistance is increasing, susceptibility tests should guide choices when possible.
- Of note, there are no consensus regimens for these uncommon systemic infections.
- Campylobacter fetus: amoxicillin/clavulanate and imipenem/cilastatin are usually reliable.
- H. cinaedi generally has low MICs to carbapenems, aminoglycosides, and tetracycline; penicillin and cephalosporin MICs are more variable.
- Recent clinical data support an IV β-lactam followed by oral amoxicillin, or amoxicillin therapy, whereas fluoroquinolone monotherapy should be avoided.[1]
- Ceftriaxone may be considered when the MIC is low, and the clinical context supports its use;
- Standardized H. cinaedi clinical breakpoints are unavailable.
- In the 2026 series, ceftriaxone MICs were 4 and 8 mg/L for MIC50 and MIC90, respectively.
- Ceftriaxone may be considered when the MIC is low, and the clinical context supports its use;
- Recent clinical data support an IV β-lactam followed by oral amoxicillin, or amoxicillin therapy, whereas fluoroquinolone monotherapy should be avoided.[1]
- Of note, there are no consensus regimens for these uncommon systemic infections.
- Serious infections: due to rising macrolide and fluoroquinolone resistance, do not use these agents unless susceptibility is known.
- Preferred: an active β-lactam or carbapenem backbone with an aminoglycoside as potential adjunctive therapy in selected severe disease. May refine once susceptibility results are known.
- Imipenem/cilastatin 500 mg IV q6h or 1 g IV q8h; adjust for renal function.
- Reasonable empiric selection until susceptibilities are known.
- Carbapenem resistance is low, but not absent.
- Higher doses, such as 1 g q6, are reserved for life-threatening infections or for isolates with high MICs.
- Because fluoroquinolone resistance is common and macrolide resistance is species-dependent, avoid either empirically for severe invasive disease unless activity is established.
- Reasonable empiric selection until susceptibilities are known.
- Imipenem/cilastatin 500 mg IV q6h or 1 g IV q8h; adjust for renal function.
- Adjunctive:
- Gentamicin 5mg/kg/d IV
- Duration:
- Depends on the site:
- Uncomplicated bacteremia is often treated for approximately 10–14 days.
- Endovascular, osteoarticular, or CNS disease generally requires prolonged therapy.
- Depends on the site:
- Preferred: an active β-lactam or carbapenem backbone with an aminoglycoside as potential adjunctive therapy in selected severe disease. May refine once susceptibility results are known.
- Special situations:
- H. cinaedi: Ceftriaxone may have a role if found to be susceptible.
- Endovascular infections:
- Duration: 4-6 wks of carbapenem or active β-lactam
- Consider combination with an aminoglycoside in selected cases.
- Evaluate for an infected aneurysm or prosthetic material that may require source control.
- Duration: 4-6 wks of carbapenem or active β-lactam
- CNS: prefer a meropenem 2 g IV q 8h.
- Hypogammaglobulinemia:
- Optimize immunoglobulin replacement when indicated for the underlying humoral deficiency.
- Recurrent Campylobacter bacteremia is particularly common in this population.[5]
- Optimize immunoglobulin replacement when indicated for the underlying humoral deficiency.
- Salvage scenarios:
- Because resistance is increasing, susceptibility tests should guide choices when possible.
- Helicobacter cinaedi bacteremia:
- H. cinaedi generally has low MICs to carbapenems, aminoglycosides, and tetracycline. Penicillin and cephalosporin MICs are variable, whereas macrolide and fluoroquinolone MICs are often high.
- Duration[1]:
- Optimal duration is unknown; published regimens vary.
- Approximately 3–4 weeks is reasonable for uncomplicated bacteremia/cellulitis.
- Longer therapy is appropriate for recurrent or endovascular disease.
- Recurrence is substantial (100-day cumulative incidence 18.7% in one large series).
- Approximately 3–4 weeks is reasonable for uncomplicated bacteremia/cellulitis.
- Optimal duration is unknown; published regimens vary.
- Duration[1]:
- H. cinaedi generally has low MICs to carbapenems, aminoglycosides, and tetracycline. Penicillin and cephalosporin MICs are variable, whereas macrolide and fluoroquinolone MICs are often high.
Selected Drug Comments
Drug | Recommendation |
For H. cinaedi, the best recent clinical outcome data come from a 2026 retrospective cohort study showing that initial IV β-lactam therapy followed by oral amoxicillin or amoxicillin monotherapy was successful in 42/45 (93.3%). There are no organism-specific clinical breakpoints.[1] | |
Usually active against C. fetus with no resistance among 22 tested isolates in the 2026 multinational BSI cohort, although activity is less predictable for C. coli or C. jejuni.” | |
Appropriate for susceptible enteric infection; not preferred empirically for invasive infection. Resistance is strongly species-dependent. | |
Not reliably active against Campylobacter spp.; avoid for invasive Campylobacter unless species-specific susceptibility supports use. May have a role for susceptible H. cinaedi. | |
Use only when susceptible; fluoroquinolone resistance is common, particularly in C. jejuni and C. coli bacteremia. | |
Usually active and may be considered as part of combination therapy for severe C. fetus infections, including endovascular sites. Avoid prolonged courses due to toxicity and limit once clinical stability is obtained. Has poor CNS penetration. | |
Use for severe infections, especially when high-level resistance is a concern, particularly for C. fetus infections. Imipenem is among the most reliably active agents; the activity of other carbapenems varies by species. | |
It may be used as an alternative to imipenem. Has good CNS penetration. | |
Potential salvage option based chiefly on in vitro activity; limited clinical evidence. For C. coli in the 2026 cohort, resistance was 18.8%.[5] | |
In a 2026-published multinational BSI cohort, tetracycline resistance was 54% overall, 75% in C. coli, 55% in C. jejuni, and only 12.5% in C. fetus.[5] |
FOLLOW-UP
- Routine follow-up or test of cure is not recommended in patients with resolved diarrhea.
- Following gastroenteritis, some may develop persistent symptoms reflective of postinfectious irritable bowel syndrome.
- Occasional post-infectious complications include
- Reactive arthritis
- Guillain-Barré syndrome
- Guillain-Barré syndrome is well recognized but rare, occurring in an estimated 0.2–1.7 cases per 1,000 Campylobacter infections.[20]
- An epidemiologic association with subsequent IBD has been reported, but causality is uncertain.
OTHER INFORMATION
- Mortality from C. fetus and other invasive Campylobacter infections is higher among older adults and patients with malignancy/immunodeficiency, renal or liver disease, or diabetes.
- Appropriate active antimicrobial therapy is associated with improved survival.
- Systemic Campylobacter infections deserve initial parenteral therapy.
- Fluoroquinolone resistance is common; macrolide resistance varies markedly by species and geography.
Basis for recommendation
- Araoka H, Tomida J, Yoshino C, et al. Correlation between antimicrobial susceptibility data and clinical efficacy for Helicobacter cinaedi bacteraemia. JAC Antimicrob Resist. 2026;8(2):dlag056. [PMID:41993158]
Comment: Study correlating MICs with outcomes in 131 first episodes of H. cinaedi bacteremia. Carbapenems, aminoglycosides, and tetracycline had low MICs; penicillin/cephalosporin MICs varied, and fluoroquinolone MICs were high. IV β-lactam→oral amoxicillin or amoxicillin monotherapy succeeded in 42/45 (93.3%); levofloxacin monotherapy failed in 4 of 8.
- Shane AL, Mody RK, Crump JA, et al. 2017 Infectious Diseases Society of America Clinical Practice Guidelines for the Diagnosis and Management of Infectious Diarrhea. Clin Infect Dis. 2017;65(12):e45-e80. [PMID:29053792]
Comment: Current IDSA infectious-diarrhea guideline addressing indications for stool testing and antimicrobial treatment; supports treatment of severe/prolonged Campylobacter disease and treatment of immunocompromised patients.
- Author opinion;
Comment: No guidelines exist for non-gastrointestinal infections related to Campylobacter or Helicobacter. Recommendations mostly guided by case reports and published in vitro susceptibility profiles.
References
- Zerbato V, Guicciardi S, Baldan R, et al. Clinical Outcomes of Campylobacter Bacteremia: A Systematic Review with Meta-Analysis. Pathogens. 2026;15(7). [PMID:42515013]
Comment: This review includes 25 studies and 2,480 bacteremia episodes, with pooled mortality of 5%, secondary localization of 9%, endocarditis of 2%, and an association between appropriate therapy and lower mortality (OR 0.49).
- Paniagua-García M, Bernal-Aznar JM, Gkrania-Klotsas E, et al. Campylobacter spp Bloodstream Infections in Immunocompetent vs Immunodeficient Patients: A Multinational Cohort Study (2009-2024). Open Forum Infect Dis. 2026;13(7):ofag380. [PMID:42488720]
Comment: Multinational cohort of 261 Campylobacter BSIs: 65.9% occurred in immunodeficient patients. C. jejuni was most frequent overall, whereas C. coli was disproportionately frequent with humoral immunodeficiency. Relapse/reinfection occurred in 8% overall and 18.3% with humoral immunodeficiency. Ciprofloxacin and macrolide resistance among tested isolates were 73.8% and 14.5%, respectively
- Kitaya S, Otani H, Yanagi M, et al. Campylobacter fetus meningitis and bacteremia: A case report in a post-liver transplant and post-splenectomy patient and a restructured literature review. J Infect Chemother. 2025;31(12):102862. [PMID:41241280]
Comment: Updated literature review comprising 37 adult C. fetus meningitis cases. Relapse occurred in 22% and mortality in 5%. The authors emphasize targeted therapy and long-term follow-up because of the relapse risk.
- Ioannou P, Sourris A, Tsantes AG, et al. Infective Endocarditis by Campylobacter Species-A Narrative Review. Pathogens. 2024;13(7). [PMID:39057821]
Comment: This 2024 review found only 26 published Campylobacter IE cases. β-lactam and aminoglycoside regimens were common. Surgery occurred in 48%, and mortality was 26.9%. This is little solid evidence to back any antibiotic regimen.
- Oren I, Temper V, Michael-Gayego A, et al. Helicobacter cinaedi Bacteremia in Children: A Case Report and Literature Review. Pediatr Infect Dis J. 2024;43(4):e135-e138. [PMID:38295230]
Comment: Seven cases were described in either immunocompromised individuals or neonates.
- Zhang MM, Melton TA, Akhtar H, et al. Antimicrobial susceptibilities of Campylobacter fetus: report from a reference laboratory. J Clin Microbiol. 2024;62(4):e0144723. [PMID:38421164]
Comment: U.S. reference-laboratory susceptibility study of 105 C. fetus isolates. Organism-specific CLSI/EUCAST clinical breakpoints are lacking. Gentamicin and meropenem showed favorable MIC distributions.
- Zayet S, Klopfenstein T, Gendrin V, et al. Campylobacter fetus Invasive Infections and Risks for Death, France, 2000-2021. Emerg Infect Dis. 2023;29(11). [PMID:37877803]
Comment: Although C. fetus accounts for ~1% of Campylobacter infections overall, it accounted for 39/991 (4%) cultured Campylobacter infections at this hospital. Of the 21 cases of bacteremia, five had endovascular components. One-third of these patients succumbed within 30 days, reflecting a substantial mortality rate. As expected, the presence of septic shock and multiorgan failure were risk factors for mortality. Fever was the predominant clinical sign for those with bacteremia, not GI symptoms. In this series, amox/clav was the most commonly used regimen and the dual therapy for patients with bacteremia. Resistance was 10% for azithromycin and 33% for ciprofloxacin. No isolates were resistant to amox/clav, gentamicin, or imipenem.
- Tinévez C, Velardo F, Ranc AG, et al. Retrospective Multicentric Study on Campylobacter spp. Bacteremia in France: The Campylobacteremia Study. Clin Infect Dis. 2022;75(4):702-709. [PMID:34849656]
Comment: Large French multicenter cohort of 592 Campylobacter bacteremias. C. jejuni and C. fetus each accounted for ~43%. C. fetus was associated with secondary localizations. Median treatment duration was 10 days overall and 41.5 days with secondary localization. The appropriate antimicrobial treatment was independently associated with lower 30-day mortality.
- Ménard A, Smet A. Review: Other Helicobacter species. Helicobacter. 2019;24 Suppl 1:e12645. [PMID:31486233]
Comment: A review of non-pylori species over the last two years includes a description of a new candidate species: “Helicobacter caesarodunensis." The authors consider both human and animal diseases.
- Montgomery MP, Robertson S, Koski L, et al. Multidrug-Resistant Campylobacter jejuni Outbreak Linked to Puppy Exposure - United States, 2016-2018. MMWR Morb Mortal Wkly Rep. 2018;67(37):1032-1035. [PMID:30235182]
Comment: In an outbreak of 113 cases, the most notable finding is that the organisms were resistant to the usual oral therapies, macrolides and fluoroquinolones. The implicated puppies had often received antibiotics for at least one course.
- Araoka H, Baba M, Okada C, et al. Risk Factors for Recurrent Helicobacter cinaedi Bacteremia and the Efficacy of Selective Digestive Decontamination With Kanamycin to Prevent Recurrence. Clin Infect Dis. 2018;67(4):573-578. [PMID:29462291]
Comment: Retrospective study of 168 patients with H. cinaedi bacteremia. The 100-day cumulative incidence of recurrent bacteremia was 18.7%; anticancer chemotherapy and systemic corticosteroid therapy were independent risk factors for recurrence.
- Marchand-Senécal X, Bekal S, Pilon PA, et al. Campylobacter fetus Cluster Among Men Who Have Sex With Men, Montreal, Quebec, Canada, 2014-2016. Clin Infect Dis. 2017;65(10):1751-1753. [PMID:29020280]
Comment: Broad review of non-H. pylori and Helicobacter species and their recognized human and animal disease associations.
- Esan OB, Pearce M, van Hecke O, et al. Factors Associated with Sequelae of Campylobacter and Non-typhoidal Salmonella Infections: A Systematic Review. EBioMedicine. 2017;15:100-111. [PMID:27965105]
Comment: Systematic review of postinfectious sequelae, including reactive arthritis, Guillain-Barré syndrome, and IBD; substantial heterogeneity limits precise risk estimates.
- Saito S, Tsukahara M, Ohkusu K, et al. Helicobacter fennelliae Bacteremia: Three Case Reports and Literature Review. Medicine (Baltimore). 2016;95(18):e3556. [PMID:27149471]
Comment: The authors reviewed three cases and 24 cases in the world literature. The findings were that most patients are immunosuppressed and have GI presentations, with cellulitis not seen as often as H. cinaedi.
- van Samkar A, Brouwer MC, van der Ende A, et al. Campylobacter Fetus Meningitis in Adults: Report of 2 Cases and Review of the Literature. Medicine (Baltimore). 2016;95(8):e2858. [PMID:26937916]
Comment: Review of 22 adult C. fetus meningitis cases, with most patients having underlying illness or immunocompromise. Recurrent or persistent illness occurred in approximately 18%, emphasizing the potential for relapse and the need for prolonged therapy. Evidence regarding the optimal antimicrobial regimen and duration remains limited to case reports and small series.
- Araoka H, Baba M, Kimura M, et al. Clinical characteristics of bacteremia caused by Helicobacter cinaedi and time required for blood cultures to become positive. J Clin Microbiol. 2014;52(5):1519-22. [PMID:24574294]
Comment: This primary study found a median of 5 days, with a range of 2–12; 45% of cultures took >5 days.
- CDC. Clinical Overview of Campylobacter. https://www.cdc.gov/campylobacter/hcp/clinical-overview/index.html [revised 8/12/26, accessed 8/24/2026]
Comment: Current CDC overview of Campylobacter epidemiology, diagnosis, treatment, risk groups, and complications. CDC estimates ~1.5 million U.S. illnesses annually. Adults ≥65 years, pregnant persons, and immunocompromised patients are at increased risk for severe disease, and fluoroquinolone resistance is common.
CDC surveillance of persistent extensively drug-resistant C. jejuni strains associated predominantly with dog and pet-store puppy exposure. As of June 30, 2026, 303 laboratory-confirmed infections had been reported to PulseNet; three investigated outbreaks involved 113, 56, and 3 cases. Resistance commonly includes usual oral Campylobacter therapies
Media
C. fetus
Characteristic Gram negative, spiral-shaped bacilli after growth in brain-heart infusion (BHI), and a 7% addition of rabbit blood agar plate culture.
Source: CDC