Antibiotics for treatment of leptospirosis.

BACKGROUND: Leptospirosis is a disease transmitted from animals to humans through water, soil, or food contaminated with the urine of infected animals, caused by pathogenic Leptospira species. Antibiotics are commonly prescribed for the management of leptospirosis. Despite the widespread use of antibiotic treatment for leptospirosis, there seems to be insufficient evidence to determine its effectiveness or to recommend antibiotic use as a standard practice. This updated systematic review evaluated the available evidence regarding the use of antibiotics in treating leptospirosis, building upon a previously published Cochrane review. OBJECTIVES: To evaluate the benefits and harms of antibiotics versus placebo, no intervention, or another antibiotic for the treatment of people with leptospirosis. SEARCH METHODS: We identified randomised clinical trials following standard Cochrane procedures. The date of the last search was 27 March 2023. SELECTION CRITERIA: We searched for randomised clinical trials of various designs that examined the use of antibiotics for treating leptospirosis. We did not impose any restrictions based on the age, sex, occupation, or comorbidities of the participants involved in the trials. Our search encompassed trials that evaluated antibiotics, regardless of the method of administration, dosage, and schedule, and compared them with placebo or no intervention, or compared different antibiotics. We included trials regardless of the outcomes reported. DATA COLLECTION AND ANALYSIS: During the preparation of this review, we adhered to the Cochrane methodology and used Review Manager. The primary outcomes were all-cause mortality and serious adverse events (nosocomial infection). Our secondary outcomes were quality of life, proportion of people with adverse events considered non-serious, and days of hospitalisation. To assess the risk of bias of the included trials, we used the RoB 2 tool, and for evaluating the certainty of evidence we used GRADEpro GDT software. We presented dichotomous outcomes as risk ratios (RR) and continuous outcomes as mean differences (MD), both accompanied by their corresponding 95% confidence intervals (CI). We used the random-effects model for all our main analyses and the fixed-effect model for sensitivity analyses. For our primary outcome analyses, we included trial data from the longest follow-up period. MAIN RESULTS: We identified nine randomised clinical trials comprising 1019 participants. Seven trials compared two intervention groups and two trials compared three intervention groups. Amongst the trials comparing antibiotics versus placebos, four trials assessed penicillin and one trial assessed doxycycline. In the trials comparing different antibiotics, one trial evaluated doxycycline versus azithromycin, one trial assessed penicillin versus doxycycline versus cefotaxime, and one trial evaluated ceftriaxone versus penicillin. One trial assessed penicillin with chloramphenicol and no intervention. Apart from two trials that recruited military personnel stationed in endemic areas or military personnel returning from training courses in endemic areas, the remaining trials recruited people from the general population presenting to the hospital with fever in an endemic area. The participants' ages in the included trials was 13 to 92 years. The treatment duration was seven days for penicillin, doxycycline, and cephalosporins; five days for chloramphenicol; and three days for azithromycin. The follow-up durations varied across trials, with three trials not specifying their follow-up periods. Three trials were excluded from quantitative synthesis; one reported zero events for a prespecified outcome, and two did not provide data for any prespecified outcomes. Antibiotics versus placebo or no intervention The evidence is very uncertain about the effect of penicillin versus placebo on all-cause mortality (RR 1.57, 95% CI 0.65 to 3.79; I2 = 8%; 3 trials, 367 participants; very low-certainty evidence). The evidence is very uncertain about the effect of penicillin or chloramphenicol versus placebo on adverse events considered non-serious (RR 1.05, 95% CI 0.35 to 3.17; I2 = 0%; 2 trials, 162 participants; very low-certainty evidence). None of the included trials assessed serious adverse events. Antibiotics versus another antibiotic The evidence is very uncertain about the effect of penicillin versus cephalosporin on all-cause mortality (RR 1.38, 95% CI 0.47 to 4.04; I2 = 0%; 2 trials, 348 participants; very low-certainty evidence), or versus doxycycline (RR 0.93, 95% CI 0.13 to 6.46; 1 trial, 168 participants; very low-certainty evidence). The evidence is very uncertain about the effect of cefotaxime versus doxycycline on all-cause mortality (RR 0.18, 95% CI 0.01 to 3.78; 1 trial, 169 participants; very low-certainty evidence). The evidence is very uncertain about the effect of penicillin versus doxycycline on serious adverse events (nosocomial infection) (RR 0.62, 95% CI 0.11 to 3.62; 1 trial, 168 participants; very low-certainty evidence) or versus cefotaxime (RR 1.01, 95% CI 0.15 to 7.02; 1 trial, 175 participants; very low-certainty evidence). The evidence is very uncertain about the effect of doxycycline versus cefotaxime on serious adverse events (nosocomial infection) (RR 1.01, 95% CI 0.15 to 7.02; 1 trial, 175 participants; very low-certainty evidence). The evidence is very uncertain about the effect of penicillin versus cefotaxime (RR 3.03, 95% CI 0.13 to 73.47; 1 trial, 175 participants; very low-certainty evidence), versus doxycycline (RR 2.80, 95% CI 0.12 to 67.66; 1 trial, 175 participants; very low-certainty evidence), or versus chloramphenicol on adverse events considered non-serious (RR 0.74, 95% CI 0.15 to 3.67; 1 trial, 52 participants; very low-certainty evidence). Funding Six of the nine trials included statements disclosing their funding/supporting sources and three trials did not mention funding source. Four of the six trials mentioning sources received funds from public or governmental sources or from international charitable sources, and the remaining two, in addition to public or governmental sources, received support in the form of trial drug supply directly from pharmaceutical companies. AUTHORS' CONCLUSIONS: As the certainty of evidence is very low, we do not know if antibiotics provide little to no effect on all-cause mortality, serious adverse events, or adverse events considered non-serious. There is a lack of definitive rigorous data from randomised trials to support the use of antibiotics for treating leptospirosis infection, and the absence of trials reporting data on clinically relevant outcomes further adds to this limitation.

A case of leptospirosis in transcarpathia complicated with Jarisch-Herxheimer reaction.

A case report of Jarisch-Herxheimer (JHR) reaction on a 10th day of Leptospirosis caused by Leptospira Pomona. JHR occurs as a complication of an antibiotic treatment of various spirochetes and may lead to respiratory distress syndrome, renal failure, hepatic insufficiency, and multiple organ failure. This case represents a skin and cardio-vascular form of JHR with no lung involvement. The patient was treated with benzylpenicillin and low dexamethasone doses for 5th day of the disease with a shift to ceftriaxone and high doses of methylprednisolone. The fastest diagnosis of a sporadic zoonotic disease, early start of antibiotic therapy, and adequate doses of corticosteroids are key to the successful treatment of leptospirosis.

Leptospirosis-associated meningitis in a patient with sjögren's syndrome: a case report.

BACKGROUND: Leptospirosis is a zoonotic disease that afflicts both humans and animals. It progresses from flu-like symptoms to more severe hepatic and renal failure, and may also lead to aseptic meningitis. Individuals with autoimmune diseases (ADs) are potentially more susceptible to Leptospirosis. Thus far, limited data has documented the association between Leptospirosis and autoimmune disorders. CASE PRESENTATION: The patient had a definitive pathological diagnosis of Sjögren's syndrome (SS). Due to recurrent headaches, the patient sought consultation with a neurologist. Lumbar puncture revealed elevated white blood cells and protein levels in the cerebrospinal fluid, along with decreased glucose. Tuberculous meningitis was suspected. Radiographic imaging exhibited meningeal enhancement, ventricular enlargement, and hydrocephalus. The patient commenced treatment with anti-tuberculosis therapy and corticosteroids. Subsequently, high-throughput sequencing (HTS) of cerebrospinal fluid identified the presence of Leptospira interrogans. The patient was ultimately diagnosed with Leptospiral meningitis, and underwent antimicrobial and immunosuppressive therapy, resulting in stabilization of the condition and gradual symptom recovery. CONCLUSIONS: The case highlights the challenges in diagnosing and managing leptospirosis-related meningitis in the presence of ADs and emphasizes the importance of utilizing HTS for accurate pathogen detection. The potential correlation between leptospirosis and SS warrants further investigation, as does the need for multidisciplinary involvement in treatment strategies for such complex cases.

A rare case of severe leptospirosis infection presenting as septic shock in a non-endemic area: a case report and literature review.

BACKGROUND: Leptospirosis is a zoonosis caused by spirochete "genus" leptospira. The clinical presentations of leptospirosis range from an influenza-like presentation of fever and myalgia, to severe forms. Leptospirosis can potentially lead to a misdiagnosis or delay in diagnosis when clinical similarities exist. CASE PRESENTATION: A 63-year-old man presented with fever, shock and thrombocytopenia followed by diffuse pulmonary hemorrhage. Peripheral blood Metagenomic Next-generation Sequencing (mNGS) reported Leptospira interrogans. The patient was treated with piperacillin-tazobactam (TZP) plus doxycycline and improved dramatically after 7 days. CONCLUSION: We conclude that leptospirosis can potentially lead to a misdiagnosis or delay in diagnosis. Correctly evaluation of thrombocytopenia in acute febrile illnesses facilitates the differential diagnosis of leptospirosis. mNGS can accurately detect Leptospira DNA during the early stage of the infection.

Report of Weil's disease with a fatal course triggered by Jarisch-Herxheimer reaction.

Leptospirosis, a zoonotic disease characterized by a spectrum of influenza-like symptoms, can manifest as severe cases so called Weil's disease. Early diagnosis and treatment are crucial to avoid the potentially fatal course of the disease. Within 24 hours of the initial administration of antibiotics, patients may experience the Jarisch-Herxheimer reaction (JHR), characterized by chills, fever, hypotension, and impaired consciousness. The Okinawa Prefecture, where our hospital is situated, boasts the highest incidence rate of leptospirosis among all regions in Japan. This reports our encounter with the initial leptospirosis case after a period of 16 years within the Okinawa Prefecture. This case exhibited JHR and required the utilization of noradrenaline (NA). Despite evidence indicating that JHR does not correlate with mortality, we contend that diagnosis of Weil's disease necessitates admission to an intensive care unit (ICU) and vigilant monitoring for JHR, as it may result in impairment of general condition and fatal outcome, as observed in our case.

Evaluating the Antimicrobial and Anti-Hemolytic Activity of Synthesized Pseudopeptide against Leptospiral Species: In Silico and In Vitro Approach.

Bacterial infections are one of the leading causes of morbidity, mortality, and healthcare complications in patients. Leptospirosis is found to be the most prevalent, re-emergent, and neglected tropical zoonotic disease worldwide. The adaptation to various environmental conditions has made Leptospira acquire a large genome (~4.6 Mb) and a complex outer membrane, making it unique among bacteria that mimic the symptoms of jaundice and hemorrhage. Sph2 is another important virulence factor that enhances hemolytic sphingomyelinase-capable of moving inside mitochondria-which increases the ROS level and decreases the mitochondrial membrane potential, thereby leading to cell apoptosis. In the present study, 25 suspected bovine serum samples were subjected to the Microscopic Agglutination Test (MAT) across the Mysuru region. Different samples, such as urine, serum, and aborted materials from the confirmed MAT-positive animals, were used for isolation and genomic detection by conventional PCR targeting virulence gene, Lipl32, using specific primers. Further, in vitro and in silico studies were performed on isolated cultures to assess the anti-leptospiral, anti-hemolytic, and sphingomyelinase enzyme inhibition using novel pseudopeptides. The microdilution technique (MDT) and dark field microscope (DFM) assays revealed that at a concentration of 62.5 µg/mL, the pseudopeptide inhibited 100% of the growth of Leptospira spp., suggesting its efficiency in the treatment of leptospirosis. The flow cytometry analyses show the potency of the pseudopeptide against sphingomyelinase enzymes using human umbilical vein endothelial cells (HUVECs). Thus, the present study demonstrated the efficacy of the pseudopeptide in the inhibition of the growth of Leptospira, and therefore, this can be used as an alternative drug for the treatment of leptospirosis.

Anti-macrophage migration inhibitory factor (MIF) activity of ibudilast: A repurposing drug attenuates the pathophysiology of leptospirosis.

To develop the macrophage migration inhibitory factor (MIF) directed therapeutic approach for the treatment of leptospirosis, we identified potential MIF inhibitors by screening 10 essential tautomerase inhibition classes of chemical compounds and 7 existing anti-inflammatory and anti-microbial drugs. Dopachrome tautomerase assay was performed to measure the anti-MIF activity of selected compounds. Among 17 chemical compounds, ibudilast, an anti-inflammatory agent showed the MIF tautomerase IC50 value at a very lower concentration (9.5 ± 5.6 µM) which is considered similar to the IC50 of standard MIF antagonist, ISO-1 (6.2 ± 3.8 µM) with non-significant cytotoxicity. The in vitro analysis of the therapeutic potential of MIF inhibitor revealed that ibudilast significantly reduced the leptospiral lipopolysaccharide (LPS) mediated expression of inflammatory mediators such as intercellular adhesion molecule (ICAM), p38 and p44/42 mitogen-activated protein kinase (MAPK), inflammatory cytokines, and decreased the reactive oxygen species (ROS) production, mitochondrial membrane potential (ΔΨm) loss and cell death of LPS treated THP-1 cells. In vivo analysis demonstrated that the administration of anti-MIF Ibudilast significantly reduced the histopathological changes, downregulates the pro-inflammatory cytokines, and protects the leptospiral BALB/c model from lethality by increasing the survival rate from 25% to 66%. Finally, the biocompatibility of the evaluated anti-MIF compound was explored by cytotoxicity, hemocompatibility, and cell death assay. Ibudilast showed no significant cytotoxicity and hemolytic activity was noticed even at the higher concentration of ≤50 µM and ≥250 µM, when compared with the positive control, 0.1% Triton X-100; no significant cell death was observed at ≤50 µM concentration of Ibudilast in THP-1 cells. From these lines of evidence, we propose that Ibudilast may be a great MIF targeting repurposing drug for reliable supportive treatment of severe leptospirosis.

Cerebral infarct induced by severe leptospirosis-a case report and literature review.

BACKGROUND: Although most leptospirosis is mild, the severe form can cause multiple complications, with a fatality rate of over 50% even with ICU support. The clinical manifestations of leptospirosis vary depending on organs and tissues involved. Both cerebral artery and coronary artery can be damaged by leptospirosis. Although cerebral arteritis induced by leptospirosis has been reported, cerebral infarction caused by leptospirosis is rarely reported. CASE PRESENTATION: We report the case of a 79-year-old man admitted to intensive care unit (ICU) because of 3 days duration of fever, bloody sputum and dyspnea. Five days before he was admitted to hospital, he had harvested rice in flooded fields. After admission, leptospira interrogans DNA sequence was identified in bronchoalveolar lavage fluid (BALF) by next-generation sequencing (NGS). Microscopic agglutination test (MAT) showed the serum antibody of Mini serovars was 1,600 and Hebdomadis serovars was 800. On the eighth day of admission, the patient noted left hemiplegia. Cranial CT scan revealed low-density shadow in the right basal ganglia, so cerebral infarction was diagnosed. The patient's condition rapidly deteriorated and he died on the eleventh day of admission despite penicillin treatment, invasive mechanical ventilation and continuous renal replacement support. CONCLUSION: Neurologic leptospirosis manifested as cerebral occlusion, although rare, might be deadly and should not be ignored.

Dipotassium glycyrrhizinate relieves leptospira-induced nephritis in vitro and in vivo.

Chronic leptospirosis usually occurs during sublethal doses infection of susceptible animal and reservoir host, which typical symptom is interstitial nephritis, and leptospira urine, contaminating the environment and threatening other susceptible animals and humans. Dipotassium glycyrrhizinate (DG) is a replacement for glycyrrhizic acid, which exhibits anti-inflammation, immunomodulation effects. This study is to investigate whether DG relieves leptospira-induced nephritis. In vitro, DG inhibited the leptospira-induced transcription levels of IL-1ß, IL-6, TNF-α, RANTES, MCP-1 and iNOS, and protein levels of IL-1ß and TNF-α, and downregulated NF-κB and MAPK pathway in TCMK-1 cells. In vivo, DG attenuated the kidney histopathological change and downregulated the expression of IL-1ß and TNF-α, as well as reduced kidney leptospiral burden. In summary, DG alleviated leptospira-induced inflammation through inhibitory NF-κB and MAPK pathway, and DG decreased the renal colonization of leptospires in mice.

Immune-enhanced effect of Iris polysaccharide is protective against leptospirosis.

Leptospirosis, caused by pathogenic Leptospira species, is an essential but neglected zoonosis. There are more than 300 serovars of pathogenic Leptospira, while inactivated bacteria offers only short-term serovar-specific protection. Leptospirosis treatment is mainly dependent on the use of antibiotics. However, the side effects of antibiotics and the risk of antibiotic resistance remain major problems. Thus, alternative agents which are fewer side effects on humans and efficient in leptospirosis would be welcome. Many studies have reported that polysaccharides could be used as immunostimulants in treating infection and cancer. In this study, we examined the protective effect of polysaccharides isolated from Iris against leptospirosis. To our knowledge, it is the first time to report Iris polysaccharides (IP) as an immunostimulant in treating infection. The results showed that IP treatment significantly increased the survival rate of hamsters challenged by a lethal dose of leptospires. Besides, the tissue injury and leptospiral load were reduced in IP-treated infection group compared with the untreated infection group at 4 days post-infection (p.i.). Intriguingly, IP treatment sustained intense immune response at 4 days p.i. analyzed by qPCR. The results exhibited that the gene expression of TLR2 and TLR4 was significantly increased in the group coinjected with IP and leptospires than in the infected controls. And the expression of IL-1ß and TNF-α were also up-regulated after IP treatment, except the expression of IL-1ß in the kidney. Our results not only broaden the medicinal value of Iris, but also provide a competent candidate for the control of Leptospira infection.

Aseptic meningitis as the initial presentation of Leptospira borgpetersenii serovar Tarassovi: two case reports and a literature review.

BACKGROUND: Leptospirosis is a zoonotic illness caused by pathogenic spirochetes of the genus Leptospira. The disease spectrum ranges from a mild influenza-like presentation to a more serious Weil's syndrome. Leptospirosis rarely presents as a primary neurological syndrome. We report two cases of Leptospira borgpetersenii serovar Tarasssovi presenting as aseptic meningitis in Sri Lanka. CASE PRESENTATION: We describe case reports of two patients presenting as symptomatic aseptic meningitis due to neuroleptospirosis. Both patients had significant neurological involvement at presentation in the absence of common clinical features of leptospirosis. These patients were initially managed as bacterial or viral meningitis and leptospirosis was suspected due to a history of exposure to contaminated water. Subsequently, they were diagnosed to have neuroleptospirosis by positive Leptospira serology and both patients gained full recovery. CONCLUSION: Our report highlights the importance of considering leptospirosis as a differential diagnosis in patients with aseptic meningitis in endemic settings. Obtaining a detailed occupational and recreational history is helpful in diagnosing neuroleptospirosis promptly. We report the association of Leptospira borgpetersenii serovar (sv.) Tarassovi (strain bakeri) in causing aseptic meningitis, which has not been reported to the best of our knowledge.

Pituitary apoplexy and panhypopituitarism following acute leptospirosis.

Leptospirosis is a common tropical febrile illness which may manifest with the hepatorenal syndrome and systemic hemorrhagic manifestations. Pituitary apoplexy is a rare but life-threatening condition characterized by a hemorrhage within the pituitary gland or a pituitary adenoma. Apoplexy is very rarely associated with some inducing events such as infectious diseases such as dengue hemorrhagic fever, Hantaan virus, Puumala virus have also been reported to cause pituitary apoplexy. We present the first case of pituitary apoplexy in a patient who was being treated for leptospirosis and discuss the possible mechanisms of apoplexy in the scenario presented. We also review other reports of infectious causes that may result in pituitary apoplexy.

Veno-venous extracorporeal membrane oxygenation successfully treated a case of severe pulmonary hemorrhage caused by leptospirosis.

BACKGROUND: Pulmonary hemorrhage is an important complication of leptospirosis. Once acute respiratory distress syndrome (ARDS) occurs as a secondary condition, treatment is extremely difficult and the mortality rate is very high. CASE PRESENTATION: The patient was a 49-year-old. He was admitted to the hospital because he had experienced a fever and cough for 4 days. Hemorrhage, respiratory failure, ARDS and other symptoms appeared soon after admission. Due to severe pulmonary hemorrhage secondary to ARDS, mechanical ventilation was performed through tracheal intubation. During intubation, the patient suffered cardiac arrest, and the patient's condition worsened. He was confirmed to have leptospirosis through second-generation sequencing of the alveolar lavage fluid. Finally, we successfully treated the patient with penicillin as an anti-infective medication and venous-venous extracorporeal membrane oxygenation (v-vECMO). To the best of our knowledge, this report is the first to describe the successful application of ECMO in mainland China. CONCLUSIONS: Leptospirosis can induce serious but transient ARDS with a better prognosis than other causes of ARDS. Our patient was successfully treated with V-vECMO.

Severe pulmonary haemorrhage syndrome in leptospirosis in a returning traveller.

Clinical presentation of leptospirosis ranges from asymptomatic infection to fulminant, life-threatening disease. Pulmonary involvement in terms of severe pulmonary haemorrhage syndrome (SPHS) has recently become a more frequently reported facet of leptospirosis and correlates with high mortality rates. It has not yet been described in returning German travellers. We present a case of a healthy young man developing massive pulmonary haemorrhage and severe ARDS requiring mechanical ventilation and high-dose catecholamines after travelling to Indonesia. Leptospirosis was verified by blood PCR as well as serology and treated with high-dose, intravenous penicillin. Outcome was favourable, the patient recovered completely. Leptospirosis and SPHS should be taken into account as an emerging infectious disease in patients with fever and lung involvement.

Liver function assessment using indocyanine green plasma disappearance rate in a young male with icteric leptospirosis: a case report.

BACKGROUND: Leptospirosis is one of the leading global zoonotic causes of morbidity and mortality. It is induced by a pathogenic spirochete of the genus Leptospira. The icteric form of leptospirosis is characterized by pronounced hyperbilirubinemia and associated with significantly increased mortality. Conventional static liver function tests insufficiently assess hepatic damage and have limited prognostic value. Dynamic tests, such as indocyanine green plasma (ICG) clearance, more adequately reflect hepatic functional status. In this case report we describe the ICG plasma disappearance rates (ICG-PDR) in a patient with leptospirosis and massive hyperbilirubinemia, expanding our knowledge of liver dysfunction in icteric leptospirosis. CASE PRESENTATION: A 21-year-old Caucasian man presented with acute-onset jaundice, myalgia, fever and headaches. Laboratory tests upon admission revealed, most notably, acute kidney failure and hyperbilirubinemia of 17 mg/dl with mild elevation of aminotransferases. In the course of the following 4 days, total serum bilirubin increased to 54 mg/dl. The clinical outcome was favorable with intravenous ceftriaxone and doxycycline. Presumptive diagnosis of leptospirosis was later confirmed by PCR-based amplification of leptospiral DNA in the blood. ICG-PDR values, bilirubin as well as aminotransferases were recorded throughout hospitalization and a 3-month follow-up period. Initially dramatically reduced ICG-PDR (2.0%/min, normal range: 18-25%/min) rapidly normalized within 10 days, while bilirubin remained elevated up to week 7. Mild elevation of serum alanine aminotransferase was at its peak of 124 U/l by day 12 and reached close to normal levels by week 7 upon admission. CONCLUSIONS: Markedly diminished ICG-PDR values presented in this case report suggest severe liver function impairment in the acute phase of icteric leptospirosis. Prolonged elevation of serum bilirubin may not adequately reflect recovery of liver injury in this disease. ICG clearance appears to be a promising marker for the detection of hepatic dysfunction and recovery in icteric leptospirosis in addition to the static tests.

Acute pancreatitis and vasoplegic shock associated with leptospirosis - a case report and review of the literature.

BACKGROUND: Leptospirosis or Weil's disease is caused by pathogenic spirochete bacteria called Leptospira. It is considered the most common zoonosis in the world and is usually transmitted by urine of rodents and dogs with an incubation time of 7-14 days. The clinical spectrum ranges from a subclinical infection to a fulminant septic course. CASE PRESENTATION: Here, we report the case of a German patient with acute pancreatitis associated with Leptospira interrogans causing fulminant septic shock. The patient was successfully treated with intravenous antibiotics and left the hospital fully recovered after 18 days. CONCLUSIONS: To our knowledge, this is the first case of leptospirosis with acute pancreatitis as the leading clinical manifestation in Central Europe. Serologic and molecular genetic tests for leptospirosis should be considered, if no other causes for pancreatitis can be identified.

Pharmacokinetics of enrofloxacin HCl-2H2 O (ENRO-C), PK/PD, and Monte Carlo modeling vs. Leptospira spp. in cows.

The pharmacokinetics, PK/PD ratios, and Monte Carlo modeling of enrofloxacin HCl-2H2 O (Enro-C) and its reference preparation (Enro-R) were determined in cows. Fifty-four Jersey cows were randomly assigned to six groups receiving a single IM dose of 10, 15, or 20 mg/kg of Enro-C (Enro-C10 , Enro-C15 , Enro-C20 ) or Enro-R. Serial serum samples were collected and enrofloxacin concentrations quantified. A composite set of minimum inhibitory concentrations (MIC) of Leptospira spp. was utilized to calculate PK/PD ratios: maximum serum concentration/MIC (Cmax /MIC90 ) and area under the serum vs. time concentration of enrofloxacin/MIC (AUC0-24 /MIC90 ). Monte Carlo simulations targeted Cmax /MIC = 10 and AUC0-24 /MIC = 125. Mean Cmax obtained were 6.17 and 2.46 µg/ml; 8.75 and 3.54 µg/ml; and 13.89 and 4.25 µg/ml, respectively for Enro-C and Enro-R. Cmax /MIC90 ratios were 6.17 and 2.46, 8.75 and 3.54, and 13.89 and 4.25 for Enro-C and Enro-R, respectively. Monte Carlo simulations based on Cmax /MIC90  = 10 indicate that only Enro-C15 and Enro-C20 may be useful to treat leptospirosis in cows, predicting a success rate ≥95% when MIC50  = 0.5 µg/ml, and ≥80% when MIC90  = 1.0 µg/ml. Although Enro-C15 and Enro-C20 may be useful to treat leptospirosis in cattle, clinical trials are necessary to confirm this proposal.