Geographic Expansion into the Southeast

Scientists are increasingly focusing their attention on identifying tick-borne pathogens present in the Southeastern United States. In 2015, Lantos and colleagues released a paper which reviewed the geographic expansion of Lyme disease in the Southeast over the past 14 years. They found “a marked increase in Lyme disease cases in Virginia, particularly from 2007 onwards … with development of a new disease cluster in the southern Virginia mountain region.”

And since 2009, five counties in North Carolina have been considered endemic for Lyme disease. The introduction of tick-transmitted diseases into new areas is likely to continue. According to the authors, “we may also see expansion into the mountainous areas of neighboring states, such as Kentucky, West Virginia, and Tennessee” in the coming years.

First Recovery of Live Borrelia from Southeast Residents

Rudenko and colleagues’ recent study looks at 24 individuals living in the South, who were treated for tick-borne illnesses. Three individuals were from North Carolina, 11 from Georgia and 10 from Florida. Out of the 24 people, 71% recalled a tick bite and 50% had a lesion resembling a tick bite, which ranged in size from a few centimeters in diameter to 9-12 centimeters.

The authors describe the subjects as “humans who suffered from undefined disorders, had symptoms not typical for Lyme borreliosis, but had undergone antibiotic treatment due to suspicion of having Lyme disease even though they were seronegative.”

Major symptoms included “severe headache, nausea, muscle and joint pain, numbness and tingling sensations in extremities, neck pain, back pain, panic attacks, depression, dizziness, vision problems, sleep problems, and shortness of breath.”

Successful Cultivation Despite Seronegative Status

The researchers successfully cultivated Borrelia burgdorferi and Borrelia bissettii-like spirochete from these individuals. This is the “first recovery of live Borrelia burgdorferi sensu stricto from residents of southeastern United States,” writes Rudenko. “And, the first successful cultivation of live Borrelia bissettii-like strain from a resident of North America.”

This finding is groundbreaking for several reasons. First, it demonstrates that Borrelia burgdorferi sensu stricto—the primary Lyme disease pathogen in North America—is present and causing illness in the Southeast, a region not considered endemic by the CDC. Second, it proves that patients can harbor viable, cultivable spirochetes despite being seronegative by current CDC surveillance criteria. Third, it shows that culture can succeed where serology fails.

Modified Culture Medium Enables Detection

A modified Kelly-Pettenkofer medium was used to culture the specimens, rather than a Barbour-Stoenner-Kelly-H (BSK-H) medium. The positive cultures were further characterized by DNA purification, PCR amplification, sequencing, sequence analysis and multilocus sequence analysis (MLSA) followed by transmission electron microscopy.

The choice of culture medium matters. Standard BSK-H medium is widely used but may not support optimal growth of all Borrelia strains. The modified Kelly-Pettenkofer medium may have enabled detection of spirochetes that would have failed to grow in standard media.

The comprehensive characterization—DNA sequencing, MLSA, electron microscopy—provided definitive identification of the cultured organisms as Borrelia burgdorferi sensu stricto and Borrelia bissettii-like spirochetes, eliminating possibility of contamination or misidentification.

Borrelia bissettii: An Emerging Pathogen

Borrelia bissettii has been examined as a cause of Lyme disease by detections of spirochetes in serum samples in Europe, aortic valve tissue of Lyme borreliosis patients in the Czech Republic, and B. bissettii-like DNA detected in north-coastal California.

This strain of Borrelia is widely distributed in ticks and wildlife in North America, including the Southeast. Infection with B. bissettii causes Lyme-like symptoms including flu-like symptoms, arthralgia, weakness, and myalgia.

The successful cultivation of B. bissettii-like spirochete from a North American resident represents the first time this organism has been isolated from human tissue in North America. Previously, it was known to exist in ticks and wildlife, with DNA detected in patient samples, but live organism had never been cultured.

This suggests B. bissettii may be a more significant human pathogen than previously recognized, causing illness attributed to “seronegative Lyme disease” or dismissed as non-specific symptoms.

Why These Patients Typically Would Not Be Studied

Rudenko and colleagues concede that typically his subjects would not have been studied because:

Southeastern U.S. is not considered endemic for Lyme disease by the CDC. Patients were negative by the current CDC surveillance definition. They had been treated for an extended time with antibiotics. The study was retrospective. Patients could have been re-infected.

These exclusion criteria reflect standard research practices that systematically eliminate the very patients most likely to have atypical presentations, treatment-refractory disease, or infection with non-standard Borrelia species.

By studying patients specifically excluded from typical research—seronegative, antibiotic-treated, living in non-endemic regions—Rudenko identified viable spirochetes that conventional approaches would never detect.

Persistence After Extended Antibiotic Treatment

The recovery of Borrelia bissettii-like spirochetes from individuals in the Southeast highlights the need for further study of tick-borne pathogens in that region. Furthermore, culturing live Borrelia burgdorferi sensu stricto and Borrelia bissettii-like bacterium, even after a patient has received extended treatment (some up to 9 months) with doxycycline is concerning.

This finding challenges assumptions about antibiotic efficacy in Lyme disease. Some patients had received up to 9 months of doxycycline—far exceeding standard treatment duration of 2-4 weeks. Yet viable, cultivable spirochetes were recovered from their blood or tissue.

Several explanations exist: antibiotic tolerance (organisms survive in protected niches where drug concentrations are inadequate), persister cells (metabolically inactive bacteria resistant to antibiotics targeting active growth), inadequate dosing or duration (9 months may still be insufficient for complete eradication), or reinfection (though this seems less likely given multiple patients showing same pattern).

The clinical implication is clear: extended antibiotic treatment does not guarantee spirochete eradication, and culture positivity can occur despite prolonged therapy.

Frequently Asked Questions

Was live Borrelia cultured from Southeast US patients?
Yes. This is the first recovery of live Borrelia burgdorferi sensu stricto from residents of southeastern United States, and the first successful cultivation of live Borrelia bissettii-like strain from a resident of North America.

Were these patients seronegative?
Yes. All patients were seronegative by current CDC surveillance definition, yet researchers successfully cultured live spirochetes from their samples. This demonstrates that viable infection can exist despite negative serology.

Can Borrelia be cultured after antibiotic treatment?
Yes. Live spirochetes were cultured from patients who had received extended antibiotic treatment—some up to 9 months of doxycycline. This raises concerns about persistence despite prolonged therapy.

What is Borrelia bissettii?
A Borrelia species widely distributed in ticks and wildlife in North America, causing Lyme-like symptoms including flu-like illness, arthralgia, weakness, and myalgia. This study represents first cultivation from North American human patient.

Why is the Southeast not considered endemic for Lyme disease?
CDC surveillance focuses on Northeast and upper Midwest. However, Virginia has shown marked increase in cases since 2007, five North Carolina counties are endemic since 2009, and this study cultured live Borrelia from GA and FL residents—suggesting broader geographic distribution than officially recognized.

Clinical Takeaway

Rudenko’s groundbreaking study demonstrates successful cultivation of live Borrelia burgdorferi sensu stricto and Borrelia bissettii-like spirochetes from 24 patients living in the Southeastern United States—a region not considered endemic by the CDC. This represents the first recovery of live B. burgdorferi from Southeast residents and first cultivation of B. bissettii-like organism from North American patient. The patients shared several characteristics that would typically exclude them from research studies: they lived in non-endemic region (NC, GA, FL), were seronegative by CDC surveillance definition, had received extended antibiotic treatment (some up to 9 months doxycycline), and presented with symptoms considered “not typical for Lyme borreliosis.” Yet live, viable spirochetes were successfully cultured from their samples. Seventy-one percent recalled tick bite, 50% had lesions ranging from few centimeters to 9-12 centimeters diameter. Symptoms included severe headache, nausea, muscle and joint pain, numbness and tingling in extremities, neck pain, back pain, panic attacks, depression, dizziness, vision problems, sleep problems, and shortness of breath. The successful culture required modified Kelly-Pettenkofer medium rather than standard BSK-H medium, suggesting culture media choice affects detection sensitivity. Comprehensive characterization through DNA sequencing, multilocus sequence analysis, and electron microscopy confirmed organism identity definitively. The Borrelia bissettii finding is particularly significant. This organism is widely distributed in North American ticks and wildlife but had never been cultured from human patient in North America. It causes Lyme-like symptoms including flu-like illness, arthralgia, weakness, myalgia. Its successful cultivation suggests it may be significant human pathogen causing illness attributed to “seronegative Lyme” or dismissed as non-specific symptoms. The authors acknowledge their subjects typically would not be studied because: Southeast not considered endemic, patients seronegative by CDC criteria, extended antibiotic treatment received, retrospective design, possible reinfection. These exclusion criteria reflect standard research practices that systematically eliminate patients most likely to have atypical presentations or treatment-refractory disease. By studying specifically excluded patients, Rudenko identified spirochetes conventional approaches would never detect. Most concerning: live spirochetes cultured after extended antibiotic treatment up to 9 months. This challenges assumptions about treatment efficacy. Possible explanations include antibiotic tolerance in protected tissue niches, persister cells resistant to antibiotics, inadequate dosing/duration, or reinfection. Clinical implication: extended treatment doesn’t guarantee eradication, and culture positivity can occur despite prolonged therapy. Geographic expansion context matters. Lantos documented marked increase in Virginia cases since 2007 with new disease cluster in southern Virginia mountains. Five NC counties endemic since 2009. Expansion likely continuing into Kentucky, West Virginia, Tennessee mountainous regions. Successfully culturing live Borrelia from GA and FL residents confirms tick-borne disease presence far beyond traditionally recognized endemic zones.