The transcriptional response of pathogenic Leptospira to peroxide reveals new defenses against infection-related oxidative stress.

Pathogenic Leptospira spp. are the causative agents of the waterborne zoonotic disease leptospirosis. Leptospira are challenged by numerous adverse conditions, including deadly reactive oxygen species (ROS), when infecting their hosts. Withstanding ROS produced by the host innate immunity is an important strategy evolved by pathogenic Leptospira for persisting in and colonizing hosts. In L. interrogans, genes encoding defenses against ROS are repressed by the peroxide stress regulator, PerR. In this study, RNA sequencing was performed to characterize both the L. interrogans response to low and high concentrations of hydrogen peroxide and the PerR regulon. We showed that Leptospira solicit three main peroxidase machineries (catalase, cytochrome C peroxidase and peroxiredoxin) and heme to detoxify oxidants produced during peroxide stress. In addition, canonical molecular chaperones of the heat shock response and DNA repair proteins from the SOS response were required for Leptospira recovering from oxidative damage. Identification of the PerR regulon upon exposure to H2O2 allowed to define the contribution of this regulator in the oxidative stress response. This study has revealed a PerR-independent regulatory network involving other transcriptional regulators, two-component systems and sigma factors as well as non-coding RNAs that putatively orchestrate, in concert with PerR, the oxidative stress response. We have shown that PerR-regulated genes encoding a TonB-dependent transporter and a two-component system (VicKR) are involved in Leptospira tolerance to superoxide. This could represent the first defense mechanism against superoxide in L. interrogans, a bacterium lacking canonical superoxide dismutase. Our findings provide an insight into the mechanisms required by pathogenic Leptospira to overcome oxidative damage during infection-related conditions. This will participate in framing future hypothesis-driven studies to identify and decipher novel virulence mechanisms in this life-threatening pathogen.

Recovery of Leptospires in Short- and Medium-Term Cryopreservation Using Different Glycerol and Dimethyl Sulfoxide Concentrations.

Cryopreservation is a recognized method for the maintenance of Leptospira collections. Although cryoprotectants are commonly used in order to prevent or reduce the adverse effects of freezing, there is no consensus regarding the protocols of cryopreservation. This study aimed to compare cryopreservation protocols for Leptospira using different glycerol and dimethyl sulfoxide (DMSO) concentrations. Leptospira interrogans serovar Icterohaemorrhagiae, L. interrogans serovar Bratislava, and L. borgpetersenii serovar Hardjo were used as the experimental strains. For each strain, three protocols were tested using 5% and 10% glycerol and 2.5% DMSO. For each protocol, 12 tubes containing 1.5 mL of serovar were frozen at -70°C on the same day. An aliquot of each serovar/protocol was thawed once a month throughout 1 year. The viability of leptospires was evaluated by the recovery of those at days 7, 14, and 21 after thawing. Although no significant difference was found among the leptospiral recovery rates for the 9 serovar/protocols tested, DMSO (2.5%) was shown to be slightly better than glycerol, and its use should be encouraged as a cryoprotectant for leptospires.

Coexistence and survival of pathogenic leptospires by formation of biofilm with Azospirillum.

Pathogenic Leptospira spp. represent one cause of leptospirosis worldwide and have long been regarded as solitary organisms in soil and aquatic environments. However, in the present study, Leptospira interrogans was observed to be associated with environmental biofilms with 21 bacterial isolates belonging to 10 genera. All 21 isolates were examined for their coaggregation and biofilm-forming ability with leptospires in vitro. Among these, Azospirillum brasilense RMRCPB showed maximum interspecies coaggregation with leptospiral strains (>75%, visual score of +4). Other significant coaggregating isolates belonged to the genera Sphingomonas, Micrococcus, Brevundimonas, Acinetobacter and Paracoccus. Biofilms of leptospires in combination with A. brasilense RMRCPB showed high resistance to penicillin G, ampicillin and tetracycline (minimum bactericidal concentration ≥800 µg/mL) and tolerance to UV radiation and high temperature (up to 49°C). This study hypothesized that biofilm formation with A. brasilense protects the pathogenic Leptospira from adverse environmental conditions/stress. This coexistence of pathogenic Leptospira with other bacteria may be the key factor for its persistence and survival. However, the mechanism of biofilm formation by leptospires needs to be explored to help devise an appropriate control strategy and reduce transmission of leptospires.

Leptospirosis in an urban setting: cases diagnosed at a private medical center of Western Colombia, 2008-2012.

INTRODUCTION: Leptospirosis has reemerged as significant threat particularly in developing countries, including those in Latin America. Data from Colombia is still limited and there are no published studies in the Western area of the country. METHODS: Data on suspected cases were collected over the study period (2008- 2012). Cases were diagnosed clinically and confirmed by ELISA IgG and microscopic agglutination test (MAT) (titers ≥1:400). RESULTS: During the study period 264 suspected cases of leptospirosis were found. From those, 8.33% (22 cases) were microbiologically confirmed. Number of suspected cases increased in the period from 20 (2008) (40 cases/100,000 consultations) to 58 (2012) (120 cases/100,000 consultations). Regard sex distribution, 62.5% were males, 14% in the age group 21-30 y-old, from confirmed cases 95% live in urban areas of Pereira, 25.7% own dogs and 13.2% cats, 32.3% reporting rats at home as well 22.7% at work places. From confirmed cases 72.7% were hospitalized. Clinical findings found were: fever (60.2%), myalgias (47%), and headache (41.9%), among others. All the cases corresponded to Leptospira interrogans. Regard the serovars, in these patients 6 were identified: Australis (54.5%), Icterohaemorrhagiae (45.5%), Canicola (45.5%), Panama (45.5%), Pomona (36.3) and Grippotyphosa (1%). Thirty nine percent of the patients received antimicrobial therapy, 50% ceftriaxone. No deaths occurred. CONCLUSION: Leptospirosis is an emerging infectious disease that has changed from an occupational disease of veterinarians, farmers, butchers, and other animal handlers to a cause of epidemics in poor and decayed urban communities in developing countries, including those in Latin America such as Colombia.

Para-(benzoyl)-phenylalanine as a potential inhibitor against LpxC of Leptospira spp.: homology modeling, docking, and molecular dynamics study.

Leptospira interrogans, a Gram-negative bacterial pathogen is the main cause of human leptospirosis. Lipid A is a highly immunoreactive endotoxic center of lipopolysaccharide (LPS) that anchors LPS into the outer membrane of Leptospira. Discovery of compounds inhibiting lipid-A biosynthetic pathway would be promising for dissolving the structural integrity of membrane leading to cell lysis and death of Leptospira. LpxC, a unique enzyme of lipid-A biosynthetic pathway was identified as common drug target of Leptospira. Herein, homology modeling, docking, and molecular dynamics (MD) simulations were employed to discover potential inhibitors of LpxC. A reliable tertiary structure of LpxC in complex with inhibitor BB-78485 was constructed in Modeller 9v8. A data-set of BB-78485 structural analogs were docked with LpxC in Maestro v9.2 virtual screening workflow, which implements three stage Glide docking protocol. Twelve lead molecules with better XP Gscore compared to BB-78485 were proposed as potential inhibitors of LpxC. Para-(benzoyl)-phenylalanine - that showed lowest XP Gscore (-10.35 kcal/mol) - was predicted to have best binding affinity towards LpxC. MD simulations were performed for LpxC and para-(benzoyl)-phenylalanine docking complex in Desmond v3.0. Trajectory analysis showed the docking complex and inter-molecular interactions was stable throughout the entire production part of MD simulations. The results indicate para-(benzoyl)-phenylalanine as a potent drug molecule against leptospirosis. An animated Interactive 3D Complement (I3DC) is available in Proteopedia at http://proteopedia.org/w/Journal:JBSD:10.

Molecular characterization, serotyping, and antibiotic susceptibility profile of Leptospira interrogans serovar Copenhageni isolates from Brazil.

Leptospira interrogans serogroup Icterohaemorrhagiae is the major serogroup infecting humans worldwide, and rodents and dogs are the most significant transmission sources in urban environments. Knowledge of the prevalent serovars and their maintenance hosts is essential to understand the epidemiology of leptospirosis. In this study, 20 Leptospira isolates were evaluated by pulsed-field gel electrophoresis (PFGE), variable number tandem-repeat analysis (VNTR), serotyping, and determination of antimicrobial resistance profile. Isolates, originated from bovine, canine, human, and rodent sources, were characterized by microscopic agglutination test with polyclonal and monoclonal antibodies and were identified as L. interrogans serogroup Icterohaemorrhagiae serovar Copenhageni. MICs of antimicrobials often used in veterinary medicine were determined by broth microdilution test. Most of tested antibiotics were effective against isolates, including penicillin, ampicillin, and ceftiofur. Higher MIC variability was observed for fluoroquinolones and neomycin; all isolates were resistant to trimethoprim/sulfamethoxazole and sulphadimethoxine. Isolates were genotyped by PFGE and VNTR; both techniques were unable to discriminate between serovars Copenhageni and Icterohaemorrhagiae, as expected. PFGE clustered all isolates in 1 pulsotype, indicating that these serovars can be transmitted between species and that bovine, rodent, and dogs can maintain them in the environment endangering the human population.

Synthesis, leptospirocidal activity and QSAR analysis of novel quinoxaline derivatives.

A simple and efficient method has been developed for the synthesis of series of N-Mannich bases of (E)-3- (phenylimino/4-chlorophenylimino)-2,3-dihydro-1-[(N-substituted piperazinyl) methyl]quinoxaline-2-(1H)-one 3a-f and 4a-f. The requisite 2a and 2b were obtained by reaction between quinoxaline-2,3-dione 1 and aniline/p-chloroaniline. These compounds underwent NMannich reaction with various substituted piperazines to yield (title compounds 3a-f and 4a-f respectively. Structures of synthesized compounds were confirmed by spectral studies (IR, 1H NMR, 13C NMR and Mass) and elemental analysis. All the synthesized compounds were screened for in vitro leptospirocidal activty against Leptospira interrogans. The potent compounds 4a, 4b and 4c which showed maximum activity during in vitro studies were subjected to in vivo studies. The inhibitory activity of enzymes carboxypeptidase and transpeptidase, in leptospirosis by the synthesized compounds were determined. 3D-QSAR studies model developed showed the need for more hydrophobic and less steric groups as substituent groups to enhance the in vitro activity.

Rapid isolation and susceptibility testing of Leptospira spp. using a new solid medium, LVW agar.

Pathogenic Leptospira spp., the causative agents of leptospirosis, are slow-growing Gram-negative spirochetes. Isolation of Leptospira from clinical samples and testing of antimicrobial susceptibility are difficult and time-consuming. Here, we describe the development of a new solid medium that facilitates more-rapid growth of Leptospira spp. and the use of this medium to evaluate the Etest's performance in determining antimicrobial MICs to drugs in common use for leptospirosis. The medium was developed by evaluating the effects of numerous factors on the growth rate of Leptospira interrogans strain NR-20157. These included the type of base agar, the concentration of rabbit serum (RS), and the concentration and duration of CO(2) incubation during the initial period of culture. The highest growth rate of NR-20157 was achieved using a Noble agar base supplemented with 10% RS (named LVW agar), with an initial incubation at 30°C in 5% CO(2) for 2 days prior to continuous culture in air at 30°C. These conditions were used to develop the Etest for three species, L. interrogans (NR-20161), L. kirschnerii (NR-20327), and L. borgpetersenii (NR-20151). The MICs were read on day 7 for all samples. The Etest was then performed on 109 isolates of pathogenic Leptospira spp. The MIC(90) values for penicillin G, doxycycline, cefotaxime, ceftriaxone, and chloramphenicol were 0.64 units/ml and 0.19, 0.047, 0.5, and 2 µg/ml, respectively. The use of LVW agar, which enables rapid growth, isolation of single colonies, and simple antimicrobial susceptibility testing for Leptospira spp., provides an opportunity for new areas of fundamental and applied research.

Estimation of absolute protein quantities of unlabeled samples by selected reaction monitoring mass spectrometry.

For many research questions in modern molecular and systems biology, information about absolute protein quantities is imperative. This information includes, for example, kinetic modeling of processes, protein turnover determinations, stoichiometric investigations of protein complexes, or quantitative comparisons of different proteins within one sample or across samples. To date, the vast majority of proteomic studies are limited to providing relative quantitative comparisons of protein levels between limited numbers of samples. Here we describe and demonstrate the utility of a targeting MS technique for the estimation of absolute protein abundance in unlabeled and nonfractionated cell lysates. The method is based on selected reaction monitoring (SRM) mass spectrometry and the "best flyer" hypothesis, which assumes that the specific MS signal intensity of the most intense tryptic peptides per protein is approximately constant throughout a whole proteome. SRM-targeted best flyer peptides were selected for each protein from the peptide precursor ion signal intensities from directed MS data. The most intense transitions per peptide were selected from full MS/MS scans of crude synthetic analogs. We used Monte Carlo cross-validation to systematically investigate the accuracy of the technique as a function of the number of measured best flyer peptides and the number of SRM transitions per peptide. We found that a linear model based on the two most intense transitions of the three best flying peptides per proteins (TopPep3/TopTra2) generated optimal results with a cross-correlated mean fold error of 1.8 and a squared Pearson coefficient R(2) of 0.88. Applying the optimized model to lysates of the microbe Leptospira interrogans, we detected significant protein abundance changes of 39 target proteins upon antibiotic treatment, which correlate well with literature values. The described method is generally applicable and exploits the inherent performance advantages of SRM, such as high sensitivity, selectivity, reproducibility, and dynamic range, and estimates absolute protein concentrations of selected proteins at minimized costs.

Transcriptional response of Leptospira interrogans to iron limitation and characterization of a PerR homolog.

Leptospirosis is a globally significant zoonosis caused by Leptospira spp. Iron is essential for growth of most bacterial species. Since iron availability is low in the host, pathogens have evolved complex iron acquisition mechanisms to survive and establish infection. In many bacteria, expression of iron uptake and storage proteins is regulated by Fur. L. interrogans encodes four predicted Fur homologs; we have constructed a mutation in one of these, la1857. We conducted microarray analysis to identify iron-responsive genes and to study the effects of la1857 mutation on gene expression. Under iron-limiting conditions, 43 genes were upregulated and 49 genes were downregulated in the wild type. Genes encoding proteins with predicted involvement in inorganic ion transport and metabolism (including TonB-dependent proteins and outer membrane transport proteins) were overrepresented in the upregulated list, while 54% of differentially expressed genes had no known function. There were 16 upregulated genes of unknown function which are absent from the saprophyte L. biflexa and which therefore may encode virulence-associated factors. Expression of iron-responsive genes was not significantly affected by mutagenesis of la1857, indicating that LA1857 is not a global regulator of iron homeostasis. Upregulation of heme biosynthetic genes and a putative catalase in the mutant suggested that LA1857 is more similar to PerR, a regulator of the oxidative stress response. Indeed, the la1857 mutant was more resistant to peroxide stress than the wild type. Our results provide insights into the role of iron in leptospiral metabolism and regulation of the oxidative stress response, including genes likely to be important for virulence.

Characterization of a lipopolysaccharide mutant of Leptospira derived by growth in the presence of an anti-lipopolysaccharide monoclonal antibody.

A lipopolysaccharide mutant of Leptospira interrogans (LaiMut) was obtained by growth in the presence of an agglutinating monoclonal antibody (mAb) against lipopolysaccharide. Agglutination reactions with anti-lipopolysaccharide mAbs and polyclonal antibodies showed that LaiMut had lost some serogroup Icterohaemorrhagiae agglutinating epitopes. However, LaiMut displayed an increased reactivity to antisera against related serogroups, suggesting that the disruption of some lipopolysaccharide epitopes resulted in greater exposure to cross-reactive epitopes, not accessible to antibodies in the wild type (LaiWT). Comparison of the nucleotide sequences of the lipopolysaccharide loci of LaiMut and Lai wild type (LaiWT) strains showed an inframe stop mutation in the gene encoding undecaprenyl-galactosyltransferase, a protein that provides a fundamental and nonredundant function essential for lipopolysaccharide biosynthesis. Despite this, the biosynthesis of lipopolysaccharide agglutinating antigens was not abolished by the mutation. Based on the phenotype of LaiMut and analysis of the domain structure of the undecaprenyl-galactosyltransferase in relation to the mutation, we propose that the mutation results in the expression of two functional proteins in place of the undecaprenyl-galactosyltransferase. We hypothesize that the loss of coordination of the coupled function afforded by the intact dual function protein present in the parent strain results in an inefficient production of lipopolysaccharide in LaiMut.

Global transcriptomic response of Leptospira interrogans serovar Copenhageni upon exposure to serum.

BACKGROUND: Leptospirosis is a zoonosis of worldwide distribution caused by infection with pathogenic serovars of Leptospira spp. The most common species, L. interrogans, can survive in the environment for lengthy periods of time in between infection of mammalian hosts. Transmission of pathogenic Leptospira to humans mostly occurs through abraded skin or mucosal surfaces after direct or indirect contact with infected animals or contaminated soil or water. The spirochete then spreads hematogenously, resulting in multi-organ failure and death in severe cases. Previous DNA microarray studies have identified differentially expressed genes required for adaptation to temperature and osmolarity conditions inside the host compared to those of the environment. RESULTS: In order to identify genes involved in survival in the early spirochetemic phase of infection, we performed a transcriptional analysis of L. interrogans serovar Copenhageni upon exposure to serum in comparison with EMJH medium. One hundred and sixty-eight genes were found to be differentially expressed, of which 55 were up-regulated and 113 were down-regulated. Genes of known or predicted function accounted for 54.5 and 45.1% of up- and down-regulated genes, respectively. Most of the differentially expressed genes were predicted to be involved in transcriptional regulation, translational process, two-component signal transduction systems, cell or membrane biogenesis, and metabolic pathways. CONCLUSIONS: Our study showed global transcriptional changes of pathogenic Leptospira upon exposure to serum, representing a specific host environmental cue present in the bloodstream. The presence of serum led to a distinct pattern of gene expression in comparison to those of previous single-stimulus microarray studies on the effect of temperature and osmolarity upshift. The results provide insights into the pathogenesis of leptospirosis during the early bacteremic phase of infection.

Visual proteomics of the human pathogen Leptospira interrogans.

Systems biology conceptualizes biological systems as dynamic networks of interacting elements, whereby functionally important properties are thought to emerge from the structure of such networks. Owing to the ubiquitous role of complexes of interacting proteins in biological systems, their subunit composition and temporal and spatial arrangement within the cell are of particular interest. 'Visual proteomics' attempts to localize individual macromolecular complexes inside of intact cells by template matching reference structures into cryo-electron tomograms. Here we combined quantitative mass spectrometry and cryo-electron tomography to detect, count and localize specific protein complexes in the cytoplasm of the human pathogen Leptospira interrogans. We describe a scoring function for visual proteomics and assess its performance and accuracy under realistic conditions. We discuss current and general limitations of the approach, as well as expected improvements in the future.

Efficacy of fluoroquinolones against Leptospira interrogans in a hamster model.

Ciprofloxacin, gatifloxacin, and levofloxacin were evaluated for their abilities to prevent mortality in hamsters infected with a lethal inoculum of Leptospira interrogans serovar Portlandvere. Each agent produced a statistically significant survival advantage compared to no treatment and demonstrated survival similar to that seen with doxycycline therapy.

Efficacy of macrolides and telithromycin against leptospirosis in a hamster model.

Human studies support the use of beta-lactams and tetracyclines in the treatment of leptospirosis. Additional agents from these and other classes of antimicrobials also have in vitro activity against Leptospira species, though corroborating in vivo data are limited or lacking. We evaluated the therapeutic efficacy of azithromycin, clarithromycin, and telithromycin in a lethal hamster model of leptospirosis using Leptospira interrogans serogroup Canicola serovar Portlandvere. A range of dosages for each antimicrobial was given to the infected animals on days 2 through 7 (5 days) of the 21-day survival model. All untreated control animals survived less than 10 days from infection. Ninety to 100% of doxycycline controls, treated for 5 days with 5 mg/kg of body weight of drug, survived to 21 days. Treatment with azithromycin (daily dose: 6.25, 12.5, 25, 50, 100, or 200 mg/kg) resulted in 100% survival at all evaluated doses. Animals receiving 20 mg/kg or more of clarithromycin (daily dose: 1, 5, 10, 15, 20, 40, 60, or 100 mg/kg) had improved survival. Ninety-eight percent of animals treated with telithromycin (daily dose: 1, 5, 10, 15, 20, or 40 mg/kg) survived. We conclude that all agents tested have demonstrated in vivo efficacy in treating acute leptospirosis. These results provide support for further evaluation of macrolide and ketolide antimicrobial agents in human trials.

A novel bioerodible deep scleral lamellar cyclosporine implant for uveitis.

PURPOSE: To determine the feasibility, safety, and effectiveness of an episcleral or deep scleral lamellar sustained release cyclosporine (CsA) device in a naturally occurring animal model of uveitis. METHODS: A two-compartment perfusion chamber was used to assess in vitro human and equine scleral permeability of fluorescein, dexamethasone-fluorescein, or CsA. A biodegradable, matrix-reservoir CsA implant was designed, and release rates of CsA were determined in vitro. Tissue CsA levels were measured in eyes with the implant. Horses with equine recurrent uveitis (ERU) received episcleral or deep scleral lamellar CsA implants and were monitored for up to 3 years. RESULTS: Dexamethasone-fluorescein and CsA penetrated the in vitro equine sclera poorly; however, low but detectable levels of CsA were detected intraocularly in vivo. The implant placed episclerally failed to control inflammatory episodes in ERU. CsA implants placed in the deep sclera adjacent to the suprachoroidal space resulted in high levels of CsA in most ocular tissues. In clinical equine patients with ERU, frequency of uveitic flare-ups was significantly decreased after implantation of a deep scleral lamellar CsA implant. CONCLUSIONS: Diffusion of CsA across the sclera from the episcleral space was not a feasible method of drug delivery to the equine eye. However, placing a deep scleral lamellar CsA implant adjacent to the suprachoroidal space was effective in achieving therapeutic ocular drug concentrations and controlling uveitis in horses with ERU.

[Development of a method to determine the minimum inhibitory concentration in reference strains from leptospiras]. / Desarrollo de un método para determinar la concentración mínima inhibitoria en cepas de referencias de leptospiras.

A method to determine the minimum inhibitory concentration for leptospiras was developed, since there is not a standard method to measure it at the international level. Reference strains from the pathogenic complex L. interrogans and L. biflexa were used against penicillin, cyprofloxacine, chloramphenicol, rifampicine and tetracycline. The minimum inhibitory concentration was defined as the lowest concentration of antibiotic where it was observed the inhibition of the bacterial mobility by direct examination in dark field. Ranges for penicillin were from 0.095 to 152 microg/mL, for tetracycline from 0.156 to 3.13 microg/mL, for chloramphenicol, from 0.08 to 12.52 microg/mL, for rifampicine from 0.08 to 1.56 microg/mL, and for cyprofloxacine from 0.15 to 2.4 microg/mL. The antibiotics that showed the lowest values were cyprofloxacine, rifampicine and tetracycline, whereas the most elevated value was obtained against chloramphenicol and penicillin. The strains from the serogroups circulating more frequently in Cuba were used in this research. This study will allow in a near future to determine the antimicrobial susceptibility in autochthonous strains isolated from patients with Leptospirosis at the national level.

[Evaluation of the transcription of locus rfb for the biosynthesis of LPS in Leptospira interrogans subtype hardjoprajitno]. / Evaluacion de la transcripción del locus rfb para la biosíntesis de LPS en Leptospira interrogans subtipo hardjoprajitno.

Plasmid pGL4W15-96 was constructed from the pGL4W74 vector without promoter for kanamycin and a sequence of 480pb containing the supposed J15 promoter with the objective of confirming the role of J15 sequence as a promoter for Leptospira, which restored the transcription of the gene of resistance to kanamycin in Escherichia coli and Leptospira biflexa, corroborating this way the function of the insertion as a promoter for both organisms.

Production of tumor necrosis factor alpha by Treponema pallidum, Borrelia burgdorferi s.l., and Leptospira interrogans in isolated rat Kupffer cells.

Stimulation of isolated rat Kupffer cells by viable Leptospira interrogans, Treponema pallidum and Borrelia garinii elicited cellular responses resulting in the release of different tumor necrosis factor alpha (TNF-alpha) levels, depending on the spirochetes. L. interrogans induced TNF-alpha levels higher than those achieved with B. garinii and T. pallidum (in this order), but lower than the levels achieved with lipopolysaccharide (LPS). In contrast to L. interrogans, pretreatment of borreliae and treponemes with polymyxin B did not substantially diminish the ability of B. garinii and T. pallidum to stimulate Kupffer cells. Purified T. pallidum lipoproteins TpN47, TmpA, TpN15-TpN17, and B. garinii OspA induced TNF-alpha responses comparable to that achieved by LPS. This response was almost insensitive to the action of polymyxin B.

Leptospirosis / Leptospirosis

La leptospirosis es probablemente la zoonosis más extendida en el mundo. Se presenta más comúnmente en climas húmedos y cálidos. Es una fécción producida por una variedad de espiroqueta llamada Leptospira ínterrogans, de la cual se conocen más de 200 serovariedades. El contagio es infrecuente en el hombre, y se contrae a través del contacto directo o indirecto de la piel o mucosas con la orina de animales salvajes o domésticos infectados. Puede ser asintomática o presentarse como una enfermedad parecida a la influenza, a veces asociada a compromiso meníngeo. En una minoría de los casos se agregan ictericia, manifestaciones hemorrágicas e insuficiencia renal sintomática, constituyendo la enfermedad de Weil, que es la forma más grave y potencialmente fatal de la enfermedad. No son raros los cuadros clínicos incompletos o parciales. La transmisión tiene comúnmente lugar en ámbitos ocupacionales, recreacionales o domésticos. Los grupos ocupacionales más expuestos son aquellos que trabajan en contacto con suelos húmedos o con aguas estancadas, y en la esfera recreacional aquellos que se bañan, pescan o hacen deportes en aguas de poca movilidad. En el hogar tiene importancia la presencia de roedores, o el contacto estrecho con perros dentro de la casa. La mayoría de los casos se presenta en hombres, durante el verano u otoño. En su forma más común la leptospirosis adopta el aspecto clínico de un síndrome febril anictérico con múltiples síntomas inespecíficos, lo que hace difícil sospechar el diagnóstico. Sin embargo, la relevancia de la cefalea, fiebre o intensas mialgias en una persona con riesgo de exposición debe sugerir esta posibilidad. La inyección conjuntival, la presencia de meningitis aséptica, las alteraciones de sedimento urinario y la elevación frecuente de la CPK sérica pueden constituir claves clínicas valiosas. La presencia de ictericia y de insuficiencia renal clínicamente significativa definen el cuadro como enfermedad de Weil. El diagnóstico definitivo se hace por cultivo del agente causal, o más comúnmente por serología. El tratamiento antibiótico precoz y aún después de varios días de comienzo con penicilina, amoxicilina, ampicilina, tetraciclina o doxiciclina se ha demostrado como muy útil. Dado que el germen tiene una amplia sensibilidad, es posible que otros antimicrobianos también sean eficaces