Tuesday, June 14, 2016

Xenodiagnosis to detect Borrelia burgdorferi in humans

We've seen that live Borrelia burgdorferi persists (in unculturable form) when infected mice are treated with antibiotics.  What we don't know is whether they persist in humans with post-treatment Lyme disease syndrome (PTLDS), which refers to the lingering long-term symptoms experienced by a minority of Lyme disease patients who have been treated with the standard course of antibiotics.

In theory, one could simply determine whether B. burgdorferi can be detected in bits of tissue or blood extracted from volunteers with post-treatment symptoms.  This is what was done in the mouse studies that I described in my previous post.  It's easy to culture B. burgdorferi from untreated mice that have been infected for a long time.  However, humans are not mice.  Except in those with Lyme arthritis, the spirochete is hard to detect by culture or PCR in patients at later stages of Lyme disease, even in those who haven't taken antibiotics.

In fact, three of the four randomized controlled retreatment trials that I keep on bringing up on this blog included attempts to detect B. burgdorferi in cerebral spinal fluid or blood of PTLDS patients by culture and PCR.  No specimen was culture positive except for one, and none were PCR positive.  The single positive culture turned out to be a contaminant.

The rest of the scientific literature is littered with claims that Lyme Borrelia can be detected by culture or PCR in blood, urine, or CSF of treated patients.  However, critics have raised several concerns about these studies.  For instance, alternative explanations for the findings such as contamination or reinfection weren't ruled out.

With all of this as background, Marques and colleagues decided to test a different approach – xenodiagnosis.  For this procedure, uninfected ticks are deliberately placed on the skin and left for several days to give them time to take a blood meal.  If there are any spirochetes in the skin nearby, they will move towards the feeding site because they are attracted to the tick's saliva.  The spirochetes then get drawn into the tick's feeding tube along with the blood meal.  The fed ticks are then removed and tested for the presence of B. burgdorferi.  The sensitivity of xenodiagnosis can be enhanced by placing multiple ticks to increase the chance that at least one tick will drink blood containing B. burgdorferi.  Xenodiagnosis is done routinely with mice in the research setting, and I mentioned in my previous post that B. burgdorferi can be detected in antibiotic-treated mice by xenodiagnosis.

The first thing to do was a pilot study to make sure that the procedure was safe for volunteers.  25 subjects who had been treated for Lyme disease took part in the study.  10 of the 25 had PTLDS.  Ten healthy volunteers and one subject with untreated erythema migrans (EM), the skin rash of early-stage Lyme disease, were included in the study.

As for the ticks, the investigators bred and maintained Ixodes scapularis in the laboratory.  The ticks were carefully screened to make sure they were free of known infectious agents.

25-30 ticks were placed on each volunteer and covered with a special dressing to keep them in place (see images below).  The ticks were left alone for a week so that they could consume a blood meal.  Some of the fed ticks were tested for the presence of B. burgdorferi DNA by standard PCR or by a more sensitive technique:  isothermal amplification followed by PCR and mass spectrometry (IA/PCR/ESI-MS).  The remaining ticks were cultured or were placed on immune-deficient mice to determine whether B. burgdorferi, if present, could be transmitted.

Figure 1 from Marques et al., 2014.  Left panel: ticks covered with a special dressing on forearm.  Right panel: feeding ticks attached to forearm, dressing removed.

So did anyone test positive by xenodiagnosis? Yes. B. burgdorferi DNA was detected in two subjects.  One was the subject with untreated EM.  This subject served as sort of a positive control.  I say "sort of" because antibiotic therapy was started at the same time that the ticks were placed on the EM lesion – it would not have been ethical to delay treatment while the ticks were feeding.  B. burgdorferi DNA was detected in two of the ten ticks tested.  The subject was tested by xenodiagnosis again seven months later, and all ten ticks that were tested were negative for B. burgdorferi DNA.

The other positive test came from one of the PTLDS subjects.  One of the five ticks that were tested was positive for B. burgdorferi DNA.  The same subject tested positive by xenodiagnosis again 8 months later:  one of three ticks tested positive for B. burgdorferi DNA by IA/PCR/ESI-MS.

Of course DNA doesn't equal viability.  The study didn't provide much evidence that the DNA detected in the single case of PTLDS came from spirochetes that were alive at the time that the ticks were placed.  A skin biopsy taken from where the xenodiagnostic ticks were feeding was culture negative, as were the fed ticks themselves.  The ticks also failed to transmit B. burgdorferi to immune-deficient mice, a process that probably requires live, motile spirochetes.  To be fair, this was just a pilot study with the primary goal to assess the safety of xenodiagnosis.  Nothing terrible happened to the volunteers, although half experienced mild itching at the feeding site.  The investigators are recruiting additional subjects for a larger study to determine whether positive test results by xenodiagnosis are associated with post-treatment symptoms.


Marques A, Telford SR 3rd, Turk SP, Chung E, Williams C, Dardick K, Krause PJ, Brandeburg C, Crowder CD, Carolan HE, Eshoo MW, Shaw PA, & Hu LT (2014). Xenodiagnosis to detect Borrelia burgdorferi infection: a first-in-human study. Clinical Infectious Diseases, 58 (7), 937-45 PMID: 24523212

Bockenstedt LK, & Radolf JD (2014). Xenodiagnosis for posttreatment Lyme disease syndrome: resolving the conundrum or adding to it? Clinical Infectious Diseases, 58 (7), 946-8 PMID: 24523213

Telford SR 3rd, Hu LT, & Marques A (2014). Is there a place for xenodiagnosis in the clinic? Expert Review of Anti-infective Therapy, 12 (11), 1307-10 PMID: 25301228

Related posts

Saturday, May 14, 2016

Resurgence of Borrelia burgdorferi in mice a year after antibiotic treatment

As a follow up to my previous post, I would like to say something about several mouse studies from Stephen Barthold's group.  These papers are often cited by those who believe that retreatment is needed in patients who continue to experience symptoms following treatment of Lyme disease with conventional antibiotic regimens.  The assumption is that post-treatment symptoms stem from spirochetes surviving the initial antibiotic therapy.

In the 2008 and 2010 studies (described in detail here and here), Barthold's group gave doxycycline, ceftriaxone, or tigecycline to mice with disseminated Borrelia burgdorferi infection.  As expected, all tissues were culture negative up to three months following antibiotic therapy.  Tissues from untreated mice were culture positive.  However, B. burgdorferi DNA and mRNA were detected by PCR in up to half the treated mice, and microscopy revealed a few intact spirochetes in collagen-rich tissues from these mice.  Ticks allowed to feed on the treated mice even transmitted the spirochetes to other mice (albeit immune deficient ones), where B. burgdorferi DNA was detected by PCR.  Clearly, the spirochetes that survived antibiotic treatment were alive despite being unculturable.

Although live spirochetes remained following antibiotic therapy, there was no evidence that they were capable of causing disease.  Lyme disease is driven by inflammation, but no inflammatory response in the form of infiltrating immune cells were seen in tissues harboring the spirochetes.  A critic of the work also pointed out that the number of spirochetes declined during the 3 months following treatment, implying that any lingering spirochetes would eventually disappear.  It seemed unlikely that a similar phenomenon was responsible for persisting symptoms following treatment of Lyme disease in human patients, who may suffer with disabling symptoms for years.

In 2014 Barthold's group came out with another paper, which I'm discussing here for the first time.  Again, mice with disseminated B. burgdorferi infections were treated with antibiotics, ceftriaxone in this case.  But this time, the mice were left for up to a year before their tissues were examined for the presence of B. burgdorferi.  Control mice were mock treated with saline and examined along with the treated mice.

There weren't any surprises when tissues were tested by culture.  Most of the control mice were culture positive at all time points (2, 4, 8, and 12 months) with both tissues tested, the urinary bladder and the skin where B. burgdorferi was inoculated to initiate infection.  None of the treated mice were culture positive at either site at any time point.

PCR testing for B. burgdorferi DNA was done with tissue obtained from six sites in the mice.  Ticks allowed to feed on the mice were also tested for the presence B. burgdorferi DNA by PCR in a method called xenodiagnosis.  All saline-treated mice were PCR positive in most tissues tested, and most tested positive by xenodiagnosis.

The results with the mice treated with ceftriaxone are shown in the table below.  Each row represents a single mouse.  Note that each tissue homogenate was tested three times.

Table 2 from Hodzic et al., 2014.  "Interval" = time after completion of treatment; "Inoc" = skin from inoculation site; "HB" = heart base; "VM" = ventricular muscle; "QM" = quadriceps muscle; "Tt" = tibiotarsus; "XenoDx" = xenodiagnostic ticks (# ticks testing positive/# ticks placed on mouse).

They saw something remarkable with the mice left for 12 months.  Although few tissues were positive at earlier time points, most tissues extracted from mice a year after treatment tested positive.  6 of the 8 mice also tested positive by xenodiagnosis.  So, instead of eventually disappearing, the spirochetes proliferated starting at some point after 8 months elapsed following treatment.  This resurgence occurred even though the spirochetes remained unculturable.

Barthold's group also looked for evidence of inflammation.  Despite the resurgence of spirochetes, they did not see much evidence of inflammation by microscopy of the tissues 12 months  following antibiotic treatment.  However, the researchers pointed out that no conclusions can be drawn about the ability of the persisting spirochetes to cause disease since inflammation was minimal even in saline-treated mice, which harbored culturable spirochetes.

The researchers next looked for molecular evidence of inflammation.  They measured transcript levels of 18 cytokines in the base of the heart, heart muscle, quadriceps muscle, and leg joint 12 months after treatment with ceftriaxone or saline.  The levels of cytokine transcripts in the two groups were compared to those in age-matched uninfected mice.  Not surprisingly, saline-treated mice had what the authors deemed a "proinflammatory" cytokine profile, most likely due to their ongoing infection.  Antibiotic-treated mice also had a proinflammatory cytokine profile, although it differed from that of the saline-treated mice.  This observation is the first to suggest that the mice were responding to persisting spirochetes that survived antibiotic treatment.

In conclusion, the evidence is convincing that B. burgdorferi persists in mice for a long time after antibiotic treatment.  They don't eventually disappear and may even proliferate.  Whether these unculturable spirochetes are capable of generating an inflammatory condition necessary for disease is less clear, though mice do appear to generate a unique cytokine profile in response to the persisting spirochetes.

Barthold's group caution readers from applying the findings too broadly:
Because of the controversial nature of these findings, they should not be over-interpreted and certainly not translated directly into clinical management of human Lyme borreliosis.

So is there any relevance of these findings to post-treatment symptoms in humans?  I will touch upon this issue in a future post.


Hodzic E, Imai D, Feng S, & Barthold SW (2014). Resurgence of persisting non-cultivable Borrelia burgdorferi following antibiotic treatment in mice. PLOS One, 9 (1) PMID: 24466286

Related posts

Saturday, April 23, 2016

Long-term antibiotics for those with chronic symptoms that may or may not be related to Lyme disease

A Lyme disease study published a few weeks ago in the New England Journal of Medicine has received a lot of coverage in the press.  According to the abstract of the study, Berende and colleagues conducted a randomized placebo-controlled clinical trial to test the effectiveness of long-term "longer-term" antibiotics in treating "longer-term" chronic symptoms "attributed" to Lyme disease.

As many readers of this blog know, treatment of Lyme disease is a controversial topic.  Antibiotics are effective in treating Lyme disease, but 10-20% experience symptoms such as fatigue, muscular aches, and joint pain for at least 6 months following conventional treatment.  The cause of the persisting symptoms is not known.  They could be due to tissue damage caused by the infection, ongoing inflammation, or bacteria that survived antibiotic treatment.  Mainstream medical societies such as the IDSA do not believe that lingering infection is responsible for the persisting symptoms, and they do not recommend retreatment with antibiotics.  Four randomized controlled studies conducted in the U.S. showed little benefit of retreating these patients with antibiotics for up to 3 months.  On the other hand, not-so-mainstream groups such as ILADS dispute the interpretation of the data.  They insist that the treatment groups did show some improvement and that longer treatment regimens lasting longer than 3 months are needed for complete recovery of these patients.

There is another group of patients that also suffer from enduring fatigue, muscle aches, and joint pain.  They may or may not have had Lyme disease in the past, but their ongoing symptoms stem from some other condition.  Unfortunately, they may be misdiagnosed with "chronic Lyme disease" and end up being treated for a long time with antibiotics in an attempt to eradicate an infection that they don't have.

The new NEJM paper describes a randomized placebo-controlled trial that was conducted in the Netherlands.  281 subjects who had been experiencing chronic symptoms blamed on Lyme disease (fatigue, muscle aches, joint pain) were randomized into three groups.  All three groups were treated with ceftriaxone intravenously for two weeks.  The subjects were next given oral antibiotics or placebo for 12 weeks.  One group was treated with doxycycline, another group with both clarithromycin and hydroxychloroquine, and the third group was given placebo pills.

The graph below shows that the physical quality of life, the primary outcome measure, improved a little for all groups.  Because there was no difference in outcome among the three groups, the authors concluded that longer-term antibiotics were no better than short-term antibiotics in alleviating symptoms.  We don't know whether the initial two-week treatment with ceftriaxone had anything to do with the slight improvement since there was no true placebo (antibiotic-free) group.

Change in mean SF-36 physical component summary scores before and after treatment period.  Figure 2 from Berende et al., 2016.

Why wasn't a true placebo group?  The authors worried about withholding antibiotics from subjects who might have an infection that should be treated.  11% of the subjects hadn't been treated with antibiotics for their symptoms prior to their acceptance into the study.  This wasn't an issue with the earlier U.S. trials since previous treatment of Lyme disease with antibiotics was a requirement for acceptance into those studies, which included true placebo groups.

One baffling aspect of the study was the inclusion of subjects who might not have had Lyme disease prior to the appearance of their chronic symptoms. Only a third of the subjects had objective clinical features of Lyme disease (erythema migrans, meningoradiculitis, or acrodermatitis chronica atrophicans) immediately preceding their chronic symptoms, and a little more than a half recalled a tick bite.  Contrast this with the earlier U.S. studies, which only accepted patients with chronic symptoms that followed antibiotic treatment of a well-documented case of Lyme disease.

The remaining subjects did not have any objective features of Lyme disease before their chronic symptoms appeared.  The only evidence of a previous episode of Lyme disease was positive antibody testing by Western blot.  However, the antibodies may have been elicited by a Borrelia infection in the distant past.  Their past episode of Lyme disease may not be related to their chronic symptoms, which aren't specific for Lyme disease.  Another problem with relying solely on Western blots to diagnose Lyme disease is that false positives occur.  Without additional evidence, it is hard to be sure that their chronic symptoms were related to Lyme disease.

Nevertheless, the editorial accompanying the paper expressed support for the relaxed inclusion criteria used to select the subjects for the study:
Critics may rightly say that this trial does not truly capture with certainty the consequences of bona fide Lyme disease. However, studies with more stringent inclusion criteria have already been conducted, and the approach used by Berende and colleagues probably reflects the common practice in ambulatory care settings, in which patient presentations of fatigue or nonspecific pain prompt serologic checks for Lyme disease, despite evidence suggesting that these tests will not identify a probable cause or result in a treatment benefit.
The study population may reflect what's encountered by clinicians in the real world, but for a clinical trial it doesn't seem right to lump those whose chronic problems followed a real episode of Lyme disease with those whose issues had nothing to do with Lyme.  Any benefit of the antibiotics experienced by those who had genuine Lyme disease (assuming that there was any benefit) may have been obscured by the lack of benefit in those whose chronic symptoms aren't related to Lyme disease.

Berende and colleagues also defended the length of treatment, which is considered to be on the short end by those who support lengthy courses of antibiotic therapy:
...it may be argued that 14 weeks of treatment is insufficient to show a beneficial treatment effect. However, whereas prolonged antimicrobial treatment is not uncommon for various infectious diseases, the purpose of prolonged therapy for such diseases is for the prevention of microbiologic relapse rather than for a delayed onset of clinical alleviation of signs or symptoms. We are not aware of any infectious disease in which the initial effect on signs, symptoms, and laboratory findings is delayed beyond the first 3 months of effective therapy.
But the graph above clearly shows that the subjects felt better following the treatment period.  Unfortunately, as I mentioned earlier, the improvement in the quality of life can't be attributed to the antibiotics because there was no true placebo group.

With these issues, I'm not sure how this study got published in NEJM.  Regardless of my opinion, it will undoubtedly be cited as further proof that long-term antibiotics don't alleviate long-term symptoms that stem from Lyme disease.

Edit: Corrected quotes in first paragraph.


Berende A, ter Hofstede HJ, Vos FJ, van Middendorp H, Vogelaar ML, Tromp M, van den Hoogen FH, Donders AR, Evers AW, & Kullberg BJ (2016). Randomized Trial of Longer-Term Therapy for Symptoms Attributed to Lyme Disease. The New England Journal of Medicine, 374 (13), 1209-20 PMID: 27028911

Melia MT, & Auwaerter PG (2016). Time for a Different Approach to Lyme Disease and Long-Term Symptoms. The New England Journal of Medicine, 374 (13), 1277-8 PMID: 27028918

Monday, March 21, 2016

The genomes of 20 species of Leptospira

A massive study describing the genomes of 20 species of Leptospira was published a few weeks ago in PLOS Neglected Tropical Diseases.  The deluge of sequence information will be valuable to those in the leptospirosis field.  Scientists will be able to examine differences in genetic content between various categories of Leptospira species to generate hypotheses for experimental testing.  For example, genes present in species that cause infections but missing in species that don't may be important factors responsible for the pathogenesis of Leptospira.  The genome information will also aid in vaccine and serodiagnostics development by allowing researchers to identify protein antigens that are conserved among Leptospira species circulating within a region of interest.

The 20 Leptospira species are divided into 14 infectious and six noninfectous species.  (Actually, there are now 22 species known but only 20 when this study was launched.)  The infectious species are divided further into nine pathogenic and five "intermediate" species based on their genetic relatedness.

The Venn diagram below shows the number of genes that are shared among and within the three categories of Leptospira and Leptonema illini, a closely-related spirochete.  Looking at the relevant intersection (overlap) in the diagram, there are 255 genes that are carried by infectious Leptospira but not by saprophytic Leptospira.  (The other two figures in the overlap are the number of shared genes tabulated using looser criteria.  In these cases there are 302 genes found in all but one infectious Leptospira and 369 genes when those found in the majority of infectious species are counted.)  Similarly, there are 109 genes unique to the pathogenic species (or 161 or 416, if you want to use less stringent criteria).  The small circles at the periphery show the number of genes unique to each species.  So for example, L. interrogans, the species favored for study in molecular biology labs, has 672 genes that are not found in any other Leptospira species.

Figure 2A from Fouts et al., 2016.  Source.


Fouts DE, Matthias MA, Adhikarla H, Adler B, Amorim-Santos L, Berg DE, Bulach D, Buschiazzo A, Chang YF, Galloway RL, Haake DA, Haft DH, Hartskeerl R, Ko AI, Levett PN, Matsunaga J, Mechaly AE, Monk JM, Nascimento AL, Nelson KE, Palsson B, Peacock SJ, Picardeau M, Ricaldi JN, Thaipandungpanit J, Wunder EA Jr, Yang XF, Zhang JJ, & Vinetz JM (2016). What makes a bacterial species pathogenic?: Comparative genomic analysis of the genus Leptospira. PLoS Neglected Tropical Diseases, 10 (2) PMID: 26890609

Thursday, February 11, 2016

How a new species of Lyme disease bacteria was discovered

A new agent of the tick-borne illness known as Lyme disease has emerged in the upper Midwest.  The bacterium is genetically related to Borrelia burgdorferi, until now believed to be the only cause of Lyme disease in the United States.  The name proposed for the bacterium is Borrelia mayonii because the work was conducted at the Mayo Clinic.  B. mayonii has not been detected in patients outside of the Midwest (so far).  The findings are described in The Lancet Infectious Diseases.

The new species was discovered at the Mayo Clinic during routine testing of specimens (blood, cerebral spinal fluid, and joint fluid) received from all regions of the U.S.  Over 100,000 specimens collected from 2003 through 2014 were tested for Lyme disease bacteria by real-time PCR . The PCR probes were designed to detect the oppA1 gene from Borrelia species belonging to the Lyme disease group, known in the scientific literature as "B. burgdorferi sensu lato."  The Lyme disease group comprises 18 species that fall into the same genetic cluster within the genus Borrelia.  They include species known or suspected to cause Lyme disease (B. burgdorferi, B. garinii, B. afzelii, B. spielmanii, B. valaisiana, B bissettii, B. bavariensis, and B. lusitaniae) and another ten species that do not cause illness.  The PCR probes do not react with DNA from species belonging to the other cluster of Borrelia, the relapsing fever group.

The key to the discovery of the new species was the melting temperature analysis routinely programmed onto the end of real-time PCR runs.  The oppA1 PCR products amplified from B. burgdorferi strains have melting temperatures of 63.6 through 64.9°C.  For other Lyme disease species, the melting temperature ranges from 52.3°C (B. valaisiana) to 59.2°C (B. californiensis).  Therefore, the melting temperature of the oppA1 PCR product was used to distinguish B. burgdorferi from other Lyme disease Borrelia.

Over 9,000 specimens were collected from the states of Minnesota, Wisconsin, and North Dakota from January 2012 through September 2014.  102 were PCR positive, and most of the PCR products had the melting temperature profile of B. burgdorferi.  However, six had melting temperatures ranging from 60.4°C to 61.2°C, too low to be B. burgdorferi but too high to be any other member of the Lyme disease group.  The novel spirochetes were cultured from the blood of two of the patients.  The DNA sequence of several "housekeeping" genes of the new isolates differed enough from those of other Borrelia species to signify that a new Borrelia species has been found.  The investigators named the new spirochete Borrelia mayonii.  No specimen collected from other regions of the U.S. exhibited the atypical melting temperatures, and neither did any collected earlier than 2012 from the Midwest.  These findings led the authors to conclude that B. mayonii has recently emerged in the upper Midwest and that the six patients are the first known cases of Lyme disease to be caused by the new species.

The investigators also collected Ixodes scapularis ticks in Wisconsin.  PCR and melting temperature analysis showed that 19 of 658 ticks (2.9%) were positive for B. mayonii, 195 (29.6%) positive for B. burgdorferi, and two positive for both.

One striking feature of B. mayonii infections is the large number of spirochetes circulating within the patients.  The densities ranged from 420,000 to 6,400,000 bacterial cells per milliliter, at least a hundred times higher than observed in the blood of patients with B. burgdorferi infections.  The numbers were high enough that spirochetes could be seen in blood collected from one of the patients.

Fig. 1b from Pritt et al., 2016

The six patients had many of the typical Lyme disease symptoms:  headache, neck pain, muscle aches, joint pain, and fatigue.  Although mild fever is also common in Lyme disease, two of the six patients had severe fevers with temperature readings approaching 40°C (104°F).  Four had nausea or were vomiting, which are also uncommon Lyme disease symptoms.  Two patients were hospitalized because of the severity of their illness.  Lyme disease may be missed in those infected with B. mayonii because of the unusual symptoms.

The standard two-tier antibody test, which uses B. burgdorferi antigens to detect reactive antibody, may help with the diagnosis.  Blood specimens from five of the six patients were tested.  Four patients either tested positive or, if negative initially, tested positive with blood drawn weeks later.  The one patient who tested negative had blood drawn only on the first day of illness, so it's likely that the antibody response hadn't kicked in fully.  The test appears to help with the diagnosis of Lyme disease caused by B. mayonii, but the number of patients tested was too small to draw firm conclusions.

The authors conclude:

In view of the differing clinical manifestations for patients infected with the novel B burgdorferi sensu lato genospecies, it is likely that Lyme borreliosis is not being considered—and therefore not diagnosed—in some patients with this infection. The clinical range of illness must be better defined in additional patients to ensure that physicians can recognise the infection and distinguish it from other tick-borne infections. Many tick-borne pathogens have global distribution, therefore studies are needed to establish the geographic distribution of human beings and ticks infected with the novel B. burgdorferi sensu lato genopecies. Finally, clinicians should be aware of the potential role of oppA1 PCR for diagnosing infection with this novel pathogen.


Pritt BS, Mead PS, Johnson DK, Neitzel DF, Respicio-Kingry LB, Davis JP, Schiffman E, Sloan LM, Schriefer ME, Replogle AJ, Paskewitz SM, Ray JA, Bjork J, Steward CR, Deedon A, Lee X, Kingry LC, Miller TK, Feist MA, Theel ES, Patel R, Irish CL, & Petersen JM (2016). Identification of a novel pathogenic Borrelia species causing Lyme borreliosis with unusually high spirochaetaemia: a descriptive study. The Lancet. Infectious diseases. PMID: 26856777