Septic Arthritis: Diagnosis and Treatment.

Septic arthritis must be considered and promptly diagnosed in any patient presenting with acute atraumatic joint pain, swelling, and fever. Risk factors for septic arthritis include age older than 80 years, diabetes mellitus, rheumatoid arthritis, recent joint surgery, hip or knee prosthesis, skin infection, and immunosuppressive medication use. A delay in diagnosis and treatment can result in permanent morbidity and mortality. Physical examination findings and serum markers, including erythrocyte sedimentation rate and C-reactive protein, are helpful in the diagnosis but are nonspecific. Synovial fluid studies are required to confirm the diagnosis. History and Gram stain aid in determining initial antibiotic selection. Staphylococcus aureus is the most common pathogen isolated in septic arthritis; however, other bacteria, viruses, fungi, and mycobacterium can cause the disease. After synovial fluid has been obtained, empiric antibiotic therapy should be initiated if there is clinical concern for septic arthritis. Oral antibiotics can be given in most cases because they are not inferior to intravenous therapy. Total duration of therapy ranges from two to six weeks; however, certain infections require longer courses. Consideration for microorganisms such as Neisseria gonorrhoeae, Borrelia burgdorferi, and fungal infections should be based on history findings and laboratory results.

Forty Years of Evidence on the Efficacy and Safety of Oral and Injectable Antibiotics for Treating Lyme Disease of Adults and Children: A Network Meta-Analysis.

Lyme disease (LD) is a heavy public health burden. The most common manifestations of LD include erythema migrans (EM), Lyme neuroborreliosis (LNB), and Lyme arthritis (LA). The efficacy and safety of antibiotics for treating LD is still controversial. Thus, we performed a network meta-analysis (NMA) to obtain more data and tried to solve this problem. We searched studies in the databases of Embase and PubMed from the date of their establishments until 22 April 2021. Odds ratios (ORs) were used to assess dichotomous outcomes. A total of 31 randomized controlled trials (RCTs) involving 2,748 patients and 11 antibiotics were included. Oral amoxicillin (1.5 g/day), oral azithromycin (0.5 g/day), injectable ceftriaxone, and injectable cefotaxime were effective for treating LD (range of ORs, 1.02 to 1,610.43). Cefuroxime and penicillin were safe for treating LD (range of ORs, 0.027 to 0.98). Amoxicillin was effective for treating EM (range of ORs, 1.18 to 25.66). Based on the results, we thought oral amoxicillin (1.5 g/day), oral azithromycin (0.5 g/day), injectable ceftriaxone, and injectable cefotaxime were effective for treating LD. Cefuroxime and penicillin were safe for treating LD. Amoxicillin was effective for treating EM. We did not observe evidence proving the advantage of doxycycline in efficacy and safety for treating LD, LA, LNB, and EM of children or adults. We did not have sufficient data to prove the significant difference of efficacy for treating LA and LNB in adults and LD in children, the significant difference of safety of oral drugs for treating LD, and the significant difference of safety of drugs for treating EM. IMPORTANCE Some previous studies investigated the efficacy and safety of antibiotics for treating Lyme disease (LD). However, due to technical limitations, several questions regarding the routes of drug administration and the dosages of drug are still unclear, which might be causing problems for clinicians. Hence, we performed network meta-analysis (NMA) to quantitatively analyze the clinical data published during the last 40 years. Here, we demonstrate the evidence regarding the efficacy and safety of antibiotics commonly used for treating LD in adults and children. We found that amoxicillin, azithromycin, ceftriaxone, and cefotaxime were effective for treating LD, but we did not observe significant efficacy and safety of doxycycline for treating LD.

A selective antibiotic for Lyme disease.

Lyme disease is on the rise. Caused by a spirochete Borreliella burgdorferi, it affects an estimated 500,000 people in the United States alone. The antibiotics currently used to treat Lyme disease are broad spectrum, damage the microbiome, and select for resistance in non-target bacteria. We therefore sought to identify a compound acting selectively against B. burgdorferi. A screen of soil micro-organisms revealed a compound highly selective against spirochetes, including B. burgdorferi. Unexpectedly, this compound was determined to be hygromycin A, a known antimicrobial produced by Streptomyces hygroscopicus. Hygromycin A targets the ribosomes and is taken up by B. burgdorferi, explaining its selectivity. Hygromycin A cleared the B. burgdorferi infection in mice, including animals that ingested the compound in a bait, and was less disruptive to the fecal microbiome than clinically relevant antibiotics. This selective antibiotic holds the promise of providing a better therapeutic for Lyme disease and eradicating it in the environment.

An rfuABCD-Like Operon and Its Relationship to Riboflavin Utilization and Mammalian Infectivity by Borrelia burgdorferi.

Riboflavin is an essential micronutrient, but its transport and utilization have remained largely understudied among pathogenic spirochetes. Here, we show that Borrelia burgdorferi, the zoonotic spirochete that causes Lyme disease, is able to import riboflavin via products of its rfuABCD-like operon as well as synthesize flavin mononucleotide and flavin adenine dinucleotide despite lacking canonical genes for their synthesis. Additionally, a mutant deficient in the rfuABCD-like operon is resistant to the antimicrobial effect of roseoflavin, a natural riboflavin analog, and is attenuated in a murine model of Lyme borreliosis. Our combined results indicate not only that are riboflavin and the maintenance of flavin pools essential for B. burgdorferi growth but also that flavin utilization and its downstream products (e.g., flavoproteins) may play a more prominent role in B. burgdorferi pathogenesis than previously appreciated.

Impact of four local anaesthetics on growth and viability of in vitro cultured Borrelia burgdorferi sensu stricto, Borrelia bavariensis and Borrelia afzelii.

Many local anaesthetics, including lidocaine, procaine and ropivacaine inhibit bacterial growth. This study investigates potential effects of these local anaesthetics on growth of Borrelia burgdorferi sensu stricto (Bbss), Borrelia bavariensis (Bbav) and Borrelia afzelii (Ba). For this purpose, Borrelia spp. organisms were either continuously or temporarily exposed to one of four local anaesthetics preparations: 20 mg/ml procaine hydrochloride (P); 10 mg/ml ropivacaine hydrochloride (R); 20 mg/ml lidocaine hydrochloride (L1, L2). L2 also contained the preservatives methyl-benzoate and propyl-benzoate, whereas P, R and L1 did not. All four local anaesthetic preparations inhibited in vitro growth of Borrelia spp. depending on concentration and exposure time. There are differences in sensitivity among the Borrelia spp. with Bbav being more susceptible to growth inhibition than Bbss and Ba. When comparing the different local anaesthetic preparations with their regard to inhibition of growth of Borrelia spp. organisms, P showed the lowest impact. It cannot be completely excluded that preservatives present in L2, methyl-benzoate and propyl-benzoate, may be a reason for further inhibition of Borrelia spp. organisms. Concentrations of local anaesthetics used in these experiments may also be present in the skin of patients during regular medical procedures. These are preliminary findings and further experiments, preferably in vivo, are necessary. To minimize the risk to produce false negative results with cultures, we recommend using procaine in a preparation without preservatives for local anaesthesia prior to skin sampling.

Azlocillin can be the potential drug candidate against drug-tolerant Borrelia burgdorferi sensu stricto JLB31.

Lyme disease is one of most common vector-borne diseases, reporting more than 300,000 cases annually in the United States. Treating Lyme disease during its initial stages with traditional tetracycline antibiotics is effective. However, 10-20% of patients treated with antibiotic therapy still shows prolonged symptoms of fatigue, musculoskeletal pain, and perceived cognitive impairment. When these symptoms persists for more than 6 months to years after completing conventional antibiotics treatment are called post-treatment Lyme disease syndrome (PTLDS). Though the exact reason for the prolongation of post treatment symptoms are not known, the growing evidence from recent studies suggests it might be due to the existence of drug-tolerant persisters. In order to identify effective drug molecules that kill drug-tolerant borrelia we have tested two antibiotics, azlocillin and cefotaxime that were identified by us earlier. The in vitro efficacy studies of azlocillin and cefotaxime on drug-tolerant persisters were done by semisolid plating method. The results obtained were compared with one of the currently prescribed antibiotic doxycycline. We found that azlocillin completely kills late log phase and 7-10 days old stationary phase B. burgdorferi. Our results also demonstrate that azlocillin and cefotaxime can effectively kill in vitro doxycycline-tolerant B. burgdorferi. Moreover, the combination drug treatment of azlocillin and cefotaxime effectively killed doxycycline-tolerant B. burgdorferi. Furthermore, when tested in vivo, azlocillin has shown good efficacy against B. burgdorferi in mice model. These seminal findings strongly suggests that azlocillin can be effective in treating B. burgdorferi sensu stricto JLB31 infection and furthermore in depth research is necessary to evaluate its potential use for Lyme disease therapy.

Non-anticoagulant Heparin as a Pre-exposure Prophylaxis Prevents Lyme Disease Infection.

Lyme disease (LD) is caused by the spirochete Borrelia burgdorferi sensu lato (Bbsl). After transmission to humans by ticks, Bbsl spreads to multiple organs, leading to arthritis, carditis, and neuroborreliosis. No effective prophylaxis against human LD prior to tick exposure is currently available. Thus, a pre-exposure prophylaxis (PrEP) against LD is needed. The establishment of LD bacteria at diverse sites is dictated partly by the binding of Bbsl to proteoglycans (PGs) and glycosaminoglycans (GAGs) in tissues. The drug heparin is structurally similar to these GAGs and inhibits Bbsl attachment to PGs, GAGs, cells, and tissues, suggesting its potential to prevent LD. However, the anticoagulant activity of heparin often results in hemorrhage, hampering the development of this compound as LD PrEP. We have previously synthesized a non-anticoagulant version of heparin (NACH), which was verified for safety in mice and humans. Here, we showed that NACH blocks Bbsl attachment to PGs, GAGs, and mammalian cells. We also found that treating mice with NACH prior to the exposure of ticks carrying Bbsl followed by continuous administration of this compound prevents tissue colonization by Bbsl. Furthermore, NACH-treated mice develop greater levels of IgG and IgM against Bbsl at early stages of infection, suggesting that the upregulation of antibody immune responses may be one of the mechanisms for NACH-mediated LD prevention. This is one of the first studies examining the ability of a heparin-based compound to prevent LD prior to tick exposure. The information presented might also be extended to prevent other infectious diseases agents.

Characterization of 5'-methylthioadenosine/S-adenosylhomocysteine nucleosidases from Borrelia burgdorferi: Antibiotic targets for Lyme disease.

BACKGROUND: Borrelia burgdorferi causes Lyme disease, the most common tick-borne illness in the United States. The Center for Disease Control and Prevention estimates that the occurrence of Lyme disease in the U.S. has now reached approximately 300,000 cases annually. Early stage Borrelia burgdorferi infections are generally treatable with oral antibiotics, but late stage disease is more difficult to treat and more likely to lead to post-treatment Lyme disease syndrome. METHODS: Here we examine three unique 5'-methylthioadenosine/S-adenosylhomocysteine (MTA/SAH) nucleosidases (MTNs or MTANs, EC 3.2.2.9) responsible for salvage of adenine and methionine in B. burgdorferi and explore their potential as antibiotic targets to treat Lyme disease. Recombinant Borrelia MTNs were expressed and purified from E. coli. The enzymes were extensively characterized for activity, specificity, and inhibition using a UV spectrophotometric assay. In vitro antibiotic activities of MTN inhibitors were assessed using a bioluminescent BacTiter-Glo™ assay. RESULTS: The three Borrelia MTNs showed unique activities against the native substrates MTA, SAH, and 5'-deoxyadenosine. Analysis of substrate analogs revealed that specific activity rapidly dropped as the length of the 5'-alkylthio substitution increased. Non-hydrolysable nucleoside transition state analogs demonstrated sub-nanomolar enzyme inhibition constants. Lastly, two late stage transition state analogs exerted in vitro IC50 values of 0.3-0.4 µg/mL against cultured B. burgdorferi cells. CONCLUSION: B. burgdorferi is unusual in that it expresses three distinct MTNs (cytoplasmic, membrane bound, and secreted) that are effectively inactivated by nucleoside analogs. GENERAL SIGNIFICANCE: The Borrelia MTNs appear to be promising targets for developing new antibiotics to treat Lyme disease.

Prospective comparison of two enzyme-linked immunosorbent spot assays for the diagnosis of Lyme neuroborreliosis.

Commercial cellular tests are used to diagnose Lyme borreliosis (LB), but studies on their clinical validation are lacking. This study evaluated the utility of an in-house and a commercial enzyme-linked immunosorbent spot (ELISpot) assay for the diagnosis of Lyme neuroborreliosis (LNB). Prospectively, peripheral blood mononuclear cells (PBMCs) were isolated from patients and controls and analysed using an in-house Borrelia ELISpot assay and the commercial LymeSpot assay. B. burgdorferi B31 whole cell lysate and a mixture of outer surface proteins were used to stimulate the PBMCs and the numbers of interferon-gamma-secreting T cells were measured. Results were evaluated using receiver operating characteristic (ROC) curve analysis. Eighteen active and 12 treated LNB patients, 10 healthy individuals treated for an early (mostly cutaneous) manifestation of LB in the past and 47 untreated healthy individuals were included. Both assays showed a poor diagnostic performance with sensitivities, specificities, positive and negative predictive values ranging from 44.4-66.7%, 42.0-72.5%, 21.8-33.3% and 80.5-87.0%, respectively. The LymeSpot assay performed equally poorly when the calculation method of the manufacturer was used. Both the in-house and the LymeSpot assay are unable to diagnose active LNB or to monitor antibiotic treatment success.

A Novel Laminin-Binding Protein Mediates Microbial-Endothelial Cell Interactions and Facilitates Dissemination of Lyme Disease Pathogens.

Borrelia burgdorferi conserved gene products BB0406 and BB0405, members of a common B. burgdorferi paralogous gene family, share 59% similarity. Although both gene products can function as potential porins, only BB0405 is essential for infection. Here we show that, despite sequence homology and coexpression from the same operon, both proteins differ in their membrane localization attributes, antibody accessibility, and immunogenicity in mice. BB0406 is required for spirochete survival in mammalian hosts, particularly for the disseminated infection in distant organs. We identified that BB0406 interacts with laminin, one of the major constituents of the vascular basement membrane, and facilitates spirochete transmigration across host endothelial cell barriers. A better understanding of how B. burgdorferi transmigrates through dermal and tissue vascular barriers and establishes disseminated infections will contribute to the development of novel therapeutics to combat early infection.

Generality of Post-Antimicrobial Treatment Persistence of Borrelia burgdorferi Strains N40 and B31 in Genetically Susceptible and Resistant Mouse Strains.

A basic feature of infection caused by Borrelia burgdorferi, the etiological agent of Lyme borreliosis, is that persistent infection is the rule in its many hosts. The ability to persist and evade host immune clearance poses a challenge to effective antimicrobial treatment. A link between therapy failure and the presence of persister cells has started to emerge. There is growing experimental evidence that viable but noncultivable spirochetes persist following treatment with several different antimicrobial agents. The current study utilized the mouse model to evaluate if persistence occurs following antimicrobial treatment in disease-susceptible (C3H/HeJ [C3H]) and disease-resistant (C57BL/6 [B6]) mouse strains infected with B. burgdorferi strains N40 and B31 and to confirm the generality of this phenomenon, as well as to assess the persisters' clinical relevance. The status of infection was evaluated at 12 and 18 months after treatment. The results demonstrated that persistent spirochetes remain viable for up to 18 months following treatment, as well as being noncultivable. The phenomenon of persistence in disease-susceptible C3H mice is equally evident in disease-resistant B6 mice and not unique to any particular B. burgdorferi strain. The results also demonstrate that, following antimicrobial treatment, both strains of B. burgdorferi, N40 and B31, lose one or more plasmids. The study demonstrated that noncultivable spirochetes can persist in a host following antimicrobial treatment for a long time but did not demonstrate their clinical relevance in a mouse model of chronic infection. The clinical relevance of persistent spirochetes beyond 18 months following antimicrobial treatment requires further studies in other animal models.

Six versus two weeks treatment with doxycycline in Lyme neuroborreliosis: the protocol of a multicentre, non-inferiority, double-blinded and randomised controlled trial.

INTRODUCTION: Current treatment guidelines for European Lyme neuroborreliosis (LNB) recommend cephalosporins, penicillin or doxycycline for 14-28 days but evidence for optimal treatment length is poor. Treatment lengths in clinical practice tend to exceed the recommendations. Most patients experience a rapid improvement of symptoms and neurological findings within days of treatment, but some report long-term complaints. The underlying mechanisms of remaining complaints are debated, and theories as ongoing chronic infection with Borrelia burgdorferi, dysregulated immune responses, genetic predisposition, coinfection with multiple tick-borne pathogens, structural changes in CNS and personal traits have been suggested. The main purpose of our trial is to address the hypothesis of improved outcome after long-term antibiotic treatment of LNB, by comparing efficacy of treatment with 2 and 6 weeks courses of doxycycline. METHODS AND ANALYSIS: The trial has a multicentre, non-inferiority, double-blinded design. One hundred and twenty patients diagnosed with LNB according to European Federation of Neurological Societies (EFNS)guidelines will be randomised to 6 or 2 weeks treatment with oral doxycycline. The patients will be followed for 12 months. The primary endpoint is improvement on a composite clinical score (CCS) from baseline to 6 months after inclusion. Secondary endpoints are improvements in the CCS 12 months after inclusion, fatigue scored on Fatigue Severity Scale, subjective symptoms on the Patient Health Questionnaire-15 scale, health-related quality of life scored on RAND 36-item short form health survey and safety as measured by side effects of the two treatment arms. Blood and cerebrospinal fluid (CSF) are collected from inclusion and throughout the follow-up and a biobank will be established. The study started including patients in November 2015 and will continue throughout December 2019. ETHICS AND DISSEMINATION: The study is approved by the Norwegian regional committees for medical and health research ethics and the Norwegian Medicines Agency. Data from the study will be published in peer-reviewed medical journals. TRIAL REGISTRATION NUMBER: 2015-001481-25.

Azithromycin nanocrystals for dermal prevention of tick bite infections.

Azithromycin was optimized as nanocrystals with a drug content of 10.0 % (w/w) and a surfactant D-α -tocopheryl polyethylenglycol 1000 succinate (TPGS) content of 1.0 % (w/w) using bead milling for 10 min. The photon correlation spectroscopy (PCS) diameter of the bulk population was 189 nm, laser diffraction (LD) diameter 90 % was 370 nm. Spherical morphology of the optimal nanocrystals was observed by transmission electron microscope (TEM). They were stable over 1 year of storage at 4 °C with the particle size within the nanometer range which was confirmed by PCS, LD and light microscope. An acceptable physical stability of 2 years was also obtained when stored at 4 °C. No microbial attack to the nanocrystals was observed before 3 years storage at 4 °C. The saturation solubility of the nanocrystals was up to triple compared to the raw drug powder (RDP) in water. When incorporated into the gel base, highest penetration efficacy was achieved by the optimal nanocrystals compared to 1) the clinically effective ethanol-solution-gel, 2) the gel with propylene glycol and 3) the gel with RDP in the ex vivo porcine ear penetration study. Even though propylene glycol improved saturation solubility of nanocrystals, it could not bring benefit to nanocrystals in the penetration study. Based on these optimized azithromycin nanocrystals, topical administration for enhanced dermal bioavailability of azithromycin seems to be feasible.

Molecular Testing of Serial Blood Specimens from Patients with Early Lyme Disease during Treatment Reveals Changing Coinfection with Mixtures of Borrelia burgdorferi Genotypes.

Borrelia burgdorferi is the etiological agent of Lyme disease. In the current study, we used direct-detection PCR and electrospray ionization mass spectrometry to monitor and genotype B. burgdorferi isolates from serially collected whole-blood specimens from patients clinically diagnosed with early Lyme disease before and during 21 days of antibiotic therapy. B. burgdorferi isolates were detected up to 3 weeks after the initiation of antibiotic treatment, with ratios of coinfecting B. burgdorferi genotypes changing over time.

Latent Lyme Disease Resulting in Chronic Arthritis and Early Career Termination in a United States Army Officer.

Lyme disease is a continuing threat to military personnel operating in arboriferous and mountainous environments. Here we present the case of a 24-year-old Second Lieutenant, a recent graduate from the United States Military Academy, with a history of Lyme disease who developed recurrent knee effusions following surgery to correct a hip impingement. Although gonococcal arthritis was initially suspected from preliminary laboratory results, a comprehensive evaluation contradicted this diagnosis. Despite antibiotic therapy, aspiration of the effusions, and steroid treatment to control inflammation, the condition of the patient deteriorated to the point where he was found to be unfit for duty and subsequently discharged from active military service. This case illustrates the profound effect that latent Lyme disease can have on the quality of life and the career of an active duty military member. It highlights the need for increased surveillance for Borrelia burgdorferi (B. burgdorferi) in military training areas and for the early and aggressive diagnosis and treatment of military personnel who present with the symptoms of acute Lyme disease.

Cimetidine as a novel adjunctive treatment for early stage Lyme disease.

Lyme disease, caused by the spirochete Borrelia burgdorferi (Bb), is the most common vector-borne illness in the United States. It is a complex disease which may affect the skin, joints, heart, eyes, and central nervous system. Prompt diagnosis and treatment is curative in most instances. However, a significant percentage of patients experience ongoing symptoms after treatment. Currently, there is much controversy regarding the diagnosis, pathophysiology, and treatment of Lyme disease. Pathogen persistence despite treatment lies at the heart of this debate. Many believe that the ongoing symptoms are due to factors such as autoimmunity or permanent damage that is incurred during the active infection. However, there is an emerging school of thought that states that ongoing symptoms are due to a persistent infection that is able to survive both the immune response and antibiotic therapy. Numerous studies have shown that Bb can indeed persist within the host despite treatment and several mechanisms have been proposed to explain Bb's persistence capabilities. These include: polymorphism, antigenic variance, biofilm formation, persister cells, and immunomodulation. There is evidence that Bb is able to alter cytokine profiles within the host which may allow the organism to survive the immune response. This immunomodulation follows a pattern of T-helper 1 (TH1) suppression in favor of T-helper 2 (TH2) processes. In contrast, it has been shown that the optimal immune response to Bb infection involves an early, robust TH1 response and a later conversion to TH2 dominance once the infection is controlled or cleared. It has been proposed that a reconstitution of proper immune-competency in the infected host may improve clinical outcomes in Lyme disease. Cimetidine (CIM) is an over-the-counter histamine-2 (H2) antagonist that is primarily used to lower acid secretions in the stomach. T-regulatory (Treg) cells also possess the H2 receptor, which has spurred interest in CIM as a potential immunomodulator. CIM therapy has been shown to increase levels of the TH1 associated cytokines IL-12, TNF-α, and IFN-γ while decreasing levels of the TH2 associated cytokine IL-10. The author proposes a novel theory that CIM therapy during early Bb infection may promote a more appropriate immune response and increase the utility of antibiotic therapy during early stage Lyme disease, thus improving clinical outcomes of the disease.

Borrelia burgdorferi protein interactions critical for microbial persistence in mammals.

Borrelia burgdorferi is the causative agent of Lyme disease that persists in a complex enzootic life cycle, involving Ixodes ticks and vertebrate hosts. The microbe invades ticks and vertebrate hosts in spite of active immune surveillance and potent microbicidal responses, and establishes long-term infection utilising mechanisms that are yet to be unravelled. The pathogen can cause multi-system disorders when transmitted to susceptible mammalian hosts, including in humans. In the past decades, several studies identified a limited number of B. burgdorferi gene-products critical for pathogen persistence, transmission between the vectors and the host, and host-pathogen interactions. This review will focus on the interactions between B. burgdorferi proteins, as well as between microbial proteins and host components, protein and non-protein components, highlighting their roles in pathogen persistence in the mammalian host. A better understanding of the contributions of protein interactions in the microbial virulence and persistence of B. burgdorferi would support development of novel therapeutics against the infection.

Fluorescent Proteins, Promoters, and Selectable Markers for Applications in the Lyme Disease Spirochete Borrelia burgdorferi.

Lyme disease is the most widely reported vector-borne disease in the United States. Its incidence is rapidly increasing, and disease symptoms can be debilitating. The need to understand the biology of the disease agent, the spirochete Borrelia burgdorferi, is thus evermore pressing. Despite important advances in B. burgdorferi genetics, the array of molecular tools available for use in this organism remains limited, especially for cell biological studies. Here, we adapt a palette of bright and mostly monomeric fluorescent proteins for versatile use and multicolor imaging in B. burgdorferi We also characterize two novel antibiotic selection markers and establish the feasibility of their use in conjunction with extant markers. Last, we describe a set of promoters of low and intermediate strengths that allow fine-tuning of gene expression levels. These molecular tools complement and expand current experimental capabilities in B. burgdorferi, which will facilitate future investigation of this important human pathogen. To showcase the usefulness of these reagents, we used them to investigate the subcellular localization of BB0323, a B. burgdorferi lipoprotein essential for survival in the host and vector environments. We show that BB0323 accumulates at the cell poles and future division sites of B. burgdorferi cells, highlighting the complex subcellular organization of this spirochete.IMPORTANCE Genetic manipulation of the Lyme disease spirochete B. burgdorferi remains cumbersome, despite significant progress in the field. The scarcity of molecular reagents available for use in this pathogen has slowed research efforts to study its unusual biology. Of interest, B. burgdorferi displays complex cellular organization features that have yet to be understood. These include an unusual morphology and a highly fragmented genome, both of which are likely to play important roles in the bacterium's transmission, infectivity, and persistence. Here, we complement and expand the array of molecular tools available for use in B. burgdorferi by generating and characterizing multiple fluorescent proteins, antibiotic selection markers, and promoters of varied strengths. These tools will facilitate investigations in this important human pathogen, as exemplified by the polar and midcell localization of the cell envelope regulator BB0323, which we uncovered using these reagents.

Antimicrobial action of calprotectin that does not involve metal withholding.

Calprotectin is a potent antimicrobial that inhibits the growth of pathogens by tightly binding transition metals such as Mn and Zn, thereby preventing their uptake and utilization by invading microbes. At sites of infection, calprotectin is abundantly released from neutrophils, but calprotectin is also present in non-neutrophil cell types that may be relevant to infections. We show here that in patients infected with the Lyme disease pathogen Borreliella (Borrelia) burgdorferi, calprotectin is produced in neutrophil-free regions of the skin, in both epidermal keratinocytes and in immune cells infiltrating the dermis, including CD68 positive macrophages. In culture, B. burgdorferi's growth is inhibited by calprotectin, but surprisingly, the mechanism does not involve the classical withholding of metal nutrients. B. burgdorferi cells exposed to calprotectin cease growth with no reduction in intracellular Mn and no loss in activity of Mn enzymes including the SodA superoxide dismutase. Additionally, there is no obvious loss in intracellular Zn. Rather than metal depletion, we find that calprotectin inhibits B. burgdorferi growth through a mechanism that requires physical association of calprotectin with the bacteria. By comparison, calprotectin inhibited E. coli growth without physically interacting with the microbe, and calprotectin effectively depleted E. coli of intracellular Mn and Zn. Our studies with B. burgdorferi demonstrate that the antimicrobial capacity of calprotectin is complex and extends well beyond simple withholding of metal micronutrients.

Identifying Vancomycin as an Effective Antibiotic for Killing Borrelia burgdorferi.

Borrelia burgdorferi is the causative agent of Lyme borreliosis. Antibiotic therapy of early acute infection is effective for most patients, but 10 to 20% go on to develop posttreatment Lyme disease syndrome (PTLDS). The nature of PTLDS remains unknown, but currently approved antibiotics for the treatment of Lyme disease do not appear to impact these symptoms after they have developed. We reason that minimizing the time the pathogen interacts with the host will diminish the probability of developing PTLDS, irrespective of its nature. This calls for an efficient eradication of the pathogen during acute infection. In search of a superior killing antibiotic, we examined approved antibiotics for their ability to kill B. burgdorferi Vancomycin proved more effective in killing the pathogen in vitro than ceftriaxone, the standard of care for disseminated B. burgdorferi infection. Both compounds were also the most effective in killing stationary-phase cells. This is surprising, given that inhibitors of cell wall biosynthesis are known to only kill growing bacteria. We found that peptidoglycan synthesis continues in stationary-phase cells of B. burgdorferi, explaining this paradox. A combination of vancomycin and gemifloxacin sterilized a stationary-phase culture of B. burgdorferi Examination of the action of antibiotics in severe combined immunodeficient (SCID) mice showed that doxycycline, a standard of care for uncomplicated acute infection, did not clear the pathogen. In contrast, both ceftriaxone and vancomycin cleared the infection. A trial examining the early use of more potent antibiotics on the development of PTLDS may be warranted.