Gentamicin Nephrotoxicity – A Comparison of In Vitro Findings with In Vivo Experiments in Equines

Gentamicin-induced sensorineural auditory loss in healthy adult horses

Background

Irreversible sensorineural auditory loss has been reported in humans treated with aminoglycosides but not in horses.

Objective

Investigate if auditory loss occurs in horses treated using the recommended IV daily dosage of gentamicin for 7 consecutive days.

Animals

Ten healthy adult horses (7‐15 years; females and males, 5 each).

Methods

Prospective study. Physical and neurological examinations and renal function tests were performed. Gentamicin sulfate was administered at a dosage of 6.6 mg/kg via the jugular vein on alternating sides for 7 days. Gentamicin peak and trough concentrations were measured. Horses were sedated using detomidine hydrochloride IV to perform brainstem auditory evoked responses (BAER) before the first dose, immediately after the last dose, and 30 days after the last dose. Peaks latencies, amplitudes, and amplitude ratios were recorded. Data from the second and last BAER were compared to results at baseline. Bone conduction was performed to rule out conduction disorders.

Results

Seven horses had auditory loss: complete bilateral (N = 1), complete unilateral (N = 2), and partial unilateral (N = 4). Based on physical examination and BAER results, sensorineural auditory loss was suspected. Absent bone conduction ruled out a conduction disorder and further supported sensorineural auditory loss in horses with completely absent BAER. Auditory dysfunction was reversible in 4 of 7 horses.

Conclusions and Clinical Importance

Gentamicin at recommended doses may cause sensorineural auditory loss in horses that might be irreversible. Follow‐up studies are needed to investigate if other dosing protocols present a similar risk.

Measurement of Selected Renal Biochemical Parameters in Healthy Adult Donkeys Considering the Influence of Gender, Age and Blood Freezing

The reference values of the serum and urine biochemical parameters have not been well-studied in donkeys. This study aimed to assess the normal values of the selected renal biomarkers, such as: serum creatinine, blood urea nitrogen (BUN), albumin, total protein (TP), electrolytes and symmetric dimethylarginine (SDMA), urine protein concentration (UPC), urine protein/creatinine ratio (UPCR), the urine gamma-glutamyl transferase (GGTP)-to-creatinine ratio, serum creatinine-to-urine creatinine ratio (sCr/uCr), serum BUN-to-serum creatinine ratio (sBUN/sCr) and UPC-to-TP ratio, as well as the fractional electrolyte excretion of sodium (FENa) and potassium (FEK) in donkeys. The effects of age, gender and deep freezing of the serum material were investigated. Sixty-five healthy adult donkeys were involved in this study. The results showed higher BUN and TP values and lower albumin, UPCR, FENa and FEK levels in donkeys when compared to the reference values in horses. A significant gender relationship for creatinine and BUN was found. Age influenced the values of albumin, TP, potassium and chlorine. Potassium, sodium and SDMA did not show significant concentration changes after freezing. The study results demonstrated that horse reference range values for some parameters cannot be applied to donkey samples. Only a few of the serum parameters were not affected by freezing, and this should be taken into account when storing biological materials.

Symmetric dimethylarginine and renal function analysis in horses with dehydration

BACKGROUND

Acute dehydration caused by a variety of diseases in horses can lead to acute kidney injury. However, current renal biomarkers usually indicate renal damage late in the course of the disease. A novel biomarker would be helpful to diagnose renal disease earlier.

OBJECTIVES

(1) To estimate the correlation of serum symmetric dimethylarginine (SDMA) concentrations with the degree of dehydration, traditional renal biomarkers and renal function analysis, and (2) to determine the value of SDMA as a prognostic and early biomarker of renal injury in horses.

STUDY DESIGN

Prospective cohort.

METHODS

Serum SDMA, creatinine and urea concentrations and renal function analysis were measured in 41 horses with dehydration at 4 time points until 48 h after admission. Horses were grouped according to their dehydration level into mildly, moderately and severely dehydrated groups.

RESULTS

Serum SDMA concentrations at admission correlated with creatinine concentrations (r = .412, P < .001). Differences in SDMA concentrations at admission were detected among dehydration levels but not between survivors and nonsurvivors. Significant correlations of SDMA concentrations with other markers of renal function analysis and short-term outcome were not observed.

MAIN LIMITATIONS

Besides the small sample size and low statistical power, missing urine samples at specific time points were also 1 of the main limitations. Only 1 of the horses developed acute kidney injury, which made the evaluation of the predictive value of SDMA difficult.

CONCLUSIONS

SDMA concentrations correlated significantly with creatinine concentrations in dehydrated horses. Further research is needed to reveal the application of SDMA in horse.

Renal Resistive Index as A Potential Indicator of Acute Kidney Injury in Horses

Reliable and simple tests are constantly being sought to enable the quick detection of acute kidney injury in humans and animals. Diagnosis of subclinical AKI in horses, mainly in field practice, is difficult. An ultrasound scan is a routine test performed when kidney disease is suspected. The aim of the study was to establish the value of the renal resistive index (RRI) in intrarenal arteries in horses with clinical AKI and compare it to that of healthy horses. The second goal was to determine whether potentially nephrotoxic agents can influence RRI. The kidney ultrasonography examination was performed in 30 healthy horses, 11 horses with AKI and 30 horses at risk for AKI (10 colic horses, 10 horses receiving gentamicin and 10 horses receiving NSAIDs). RRI values were measured using pulsed-wave Doppler. Differences in RRI between groups were observed only in the right kidney. Horses with AKI had significantly higher RRI values compared to healthy horses. In the risk group, there was no effect of potentially nephrotoxic agents on the RRI value. RRI value in horses seem to be lower than in other species. The increase in this parameter in horses with AKI affected only one kidney and these values did not reach values obtained in other species. The clinical application of this method in non-cooperating animals remains questionable, and therefore RRI Doppler ultrasonography of blood flow in the intrarenal arteries may have poor clinical utility as a diagnostic tool in the diagnosis of AKI in horses.

Evaluation of Serum and Urine Neutrophil Gelatinase-associated Lipocalin and Cystatin C as Biomarkers of Acute Kidney Injury in Horses

Introduction

Diagnosis of acute kidney injury (AKI) in horses is difficult at the subclinical stage, due to nonspecific clinical signs. The aim of this study was to evaluate the concentrations of selected serum and urinary biomarkers in healthy horses, horses at risk of AKI, and those with clinical AKI.

Material and Methods

Thirty healthy horses, 30 horses at risk of AKI and 11 horses with clinical AKI and azotaemia were included in the study. Serum and urinary neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C were measured using commercially available enzyme immunoassay tests.

Results

The median and (in parentheses) first and third quartile concentrations of selected biomarkers in healthy horses, horses at risk of AKI and horses with AKI were respectively as follows: serum cystatin C – 0.25 (0.19–0.37), 0.23 (0.15–0.37) and 0.61 (0.37–1.13) mg/L; serum NGAL – 50.5 (38.8–58.8), 51.1 (40.4–66.9) and 98.1 (59.4–128.2) ng/mL; urinary NGAL – 20.7 (17.9–24.5), 32.3 (32.7–55.8) and 36.6 (26.8–89.9) ng/mL; and urinary cystatin C – 0.1 (0.07–0.13), 0.13 (0.1–0.2) and 0.34 (0.22–0.37) mg/L. There were significant differences in the concentration of all biomarkers between the healthy and AKI-affected horses.

Conclusion

Horses with AKI all had biomarker concentrations higher than the healthy horses. None of the biomarkers made azotaemia recognisable in all affected horses. The obtained results indicate the need to create a serum and urinary biomarker panel to detect AKI.

Detecting acute kidney injury in horses by measuring the concentration of symmetric dimethylarginine in serum

BACKGROUND

Acute kidney injury (AKI) in horses may develop as a complication of a primary disease or following the administration of nephrotoxic drugs, and may pose a diagnostic challenge. Hence, the main objective of this study was to evaluate the concentrations and diagnostic significance of serum symmetric dimethylarginine (SDMA) and conventional renal dysfunction biomarkers in healthy horses, horses at risk of developing AKI, and horses with clinically evident AKI. A second aim was to assess how gastrointestinal disease and exposure to potentially nephrotoxic drugs affected SDMA levels. Thirty healthy horses, 30 horses with gastrointestinal disease and/or receiving phenylbutazone or gentamicin (risk group) and 11 horses with AKI were included in the study. Serum SDMA levels were measured using commercially available enzyme immunoassay tests.

RESULTS

SDMA levels in healthy horses, horses at risk of AKI and horses with AKI were 12 µg/dL (11-14), 12 µg/dL (11-13) and 20 µg/dL (20-37), respectively (all results presented as a median (quartile 1-quartile 3)). There was a significant difference in SDMA concentration between the healthy horses and those with AKI, whereas the SDMA levels in healthy horses and those at risk of AKI were comparable. A SDMA cut-off value of 19 µg/dL was established. Horses from the risk group had higher urine protein concentration and urine protein to creatinine ratio compared with healthy horses. Furthermore, horses with colic from the risk group presented with elevated urine γ-glutamyl transpeptidase to creatinine ratio.

CONCLUSION

The SDMA cut-off value established in healthy horses was higher than previously reported. The SDMA level correlated with the azotaemia levels. Horses from the AKI risk group had normal SDMA levels but single urine parameters was abnormal indicating their higher sensitivity in assessing subclinical kidney dysfunction.

Evaluation of podocin in urine in horses using qualitative and quantitative methods

No sensitive method for diagnosing early kidney dysfunction in horses has been identified so far. Many studies carried out in humans and small animals show that podocin can be useful to diagnose various kidney diseases, mainly affecting the glomeruli. The aim of this study was to perform a qualitative and quantitative analysis of podocin in urine samples obtained from healthy horses, horses with clinical kidney dysfunction and horses at risk of acute kidney injury. The study objectives aimed to assess: (1) whether the selected podocin tryptic peptide for LC-MS-MRM allows for podocin detection in horse; and (2) whether the species-specific ELISA test makes this detection possible as well;, (3) whether the chosen methods are sensitive enough to detect kidney dysfunction and glomerular injury, (4) whether the results of the tests applying both methods correspond with one another, (5) whether the results correlate with the hematological and biochemical data. The signals that may indicate the presence of trypsin fragments of podocin were found in three healthy horses, all the horses diagnosed with kidney dysfunction and half of the animals at risk for acute kidney injury. The concentration of podocin, diagnosed with the ELISA test was as follows: from 0.19 to 1.2 ng/ml in healthy animals, from 0.19 to 20.0 ng/ml in AKI horses, from 0.29 to 5.71 ng/ml in horses at risk for acute kidney injury. The results of both methods corresponded significantly. Podocin may be a potential biomarker of clinical kidney disease in horses and may be used in the detection of glomerular injury. However, its use is limited by the possibility of physiological podocyturia. LC-MS-MRM seems to be a more sensitive method to evaluate the presence of podocin than the ELISA test, whilst selected tryptic peptides of podocin appear to apply to horses. The ELISA test showed greater effectiveness in excluding the disease than in confirming it.

Tarsocrural joint polymyxin B concentrations achieved following intravenous regional limb perfusion of the drug via a saphenous vein to healthy standing horses

OBJECTIVE

To determine whether therapeutic concentrations (> 0.5 to 1.0 μg/mL) of polymyxin B (PB) were achieved in the tarsocrural joint of horses when the drug was administered by IV regional limb perfusion (IV-RLP) via a saphenous vein at doses of 25, 50, and 300 mg and to describe any adverse systemic or local effects associated with such administration.

ANIMALS

9 healthy adult horses.

PROCEDURES

In the first of 2 experiments, 6 horses each received 25 and 50 mg of PB by IV-RLP via a saphenous vein with at least 2 weeks between treatments. For each treatment, a tourniquet was placed at the midmetatarsus and another was placed midway between the stifle joint and tarsus. Both tourniquets were removed 30 minutes after the assigned dose was administered. Blood and tarsocrural joint fluid samples were collected for determination of PB concentration before and at predetermined times after drug administration. In experiment 2, 4 horses were administered 300 mg of PB by IV-RLP in 1 randomly selected pelvic limb in a manner identical to that used in experiment 1.

RESULTS

For all 3 doses, the mean synovial fluid PB concentration was > 10 times the therapeutic concentration and below the level of quantification at 30 and 1,440 minutes after drug administration, respectively. No adverse systemic or local effects were observed following PB administration.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that IV-RLP of PB might be a viable alternative for treatment of horses with synovial infections caused by gram-negative bacteria.

The Sick Adult Horse: Renal Clinical Pathologic Testing and Urinalysis

Clinicopathologic evaluation of renal function and renal disease in sick adult horses remains grounded in detection of azotemia, assessment of serum and urine electrolyte concentrations, and evaluation of urinalysis findings, including specific gravity, reagent strip analysis, and sediment examination. Because increases in serum or plasma urea nitrogen and creatinine concentrations are insensitive indicators of a decreased glomerular filtration rate, there is considerable interest in identifying novel biomarkers of renal function or injury in blood and urine, with serum symmetric dimethylarginine concentration being the most recent addition to the commercial market.

Antimicrobial labelling in Australia: a threat to antimicrobial stewardship?

Antimicrobial resistance is a public health emergency, placing veterinary antimicrobial use under growing scrutiny. Antimicrobial stewardship, through appropriate use of antimicrobials, is a response to this threat. The need for antimicrobial stewardship in Australian veterinary practices has had limited investigation. A 2016 survey undertaken to investigate antimicrobial usage patterns by Australian veterinarians found that antimicrobial dose rates were varied and often inappropriate. Doses of procaine penicillin in horses and cattle were often low, with 68% and 90% of respondents, respectively, reporting doses that were unlikely to result in plasma concentrations above minimum inhibitory concentrations for common equine and bovine pathogens. Frequency of penicillin administration was also often inappropriate. Gentamicin doses in horses were largely appropriate (89% of dose rates appropriate), but 9% of respondents reported twice daily dosing. Amoxycillin and amoxycillin-clavulanate were administered at the appropriate doses, or above, to dogs and cats by 54% and 70% of respondents, respectively. Here, we explore the potential reasons for inappropriate antimicrobial dose regimens and report that antimicrobial labels often recommend incorrect dose rates and thus may be contributing to poor prescribing practices. Changes to legislation are needed to ensure that antimicrobial drug labels are regularly updated to reflect the dose needed to effectively and safely treat common veterinary pathogens. This will be especially true if changes in legislation restrict antimicrobial use by veterinarians to the uses and doses specified on the label, thus hampering the current momentum towards improved antimicrobial stewardship.

Cytoprotection by omega-3 fatty acids as a therapeutic drug vehicle when combined with nephrotoxic drugs in an intravenous emulsion: Effects on intraglomerular mesangial cells

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Distinct concentrations of Ketorolac/Gentamicin are toxic to mesangial (MES 13) cells.

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Omega-3 fatty acids protect intraglomerular mesangial cells against nephrotoxic drugs.

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Omega-6 fatty acids do not protect MES 13 cells against nephrotoxic drugs.

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Cytoprotection by n-3 PUFA may be due to increased intracellular redox state.

During therapeutic interventions, blood concentrations of intravenously applied drugs are higher, and their onset of pharmacological action is faster than with other routes of drug administration. However, acute drug therapy often produces nephrotoxic side effects, as commonly seen after treatment with Ketorolac or Gentamicin leading to questions about their use, especially for patients at risk for acute renal failure. Omega-6(n-6) and omega-3(n-3) polyunsaturated fatty acids (PUFA) affect eicosanoid metabolism, which plays a role in the regulation of inflammation. Eicosanoids derived from n-6 FA have proinflammatory and immunoactive functions, whereas eicosanoids derived from n-3 PUFA have anti-inflammatory and cytoprotective properties. We hypothesized that providing such injectable drugs with nephrotoxic potential in combination with n3-PUFAs from the outset, might afford rapid cytoprotection of renal cells, given the recent evidence that intravenously administered n3-PUFAs are rapidly incorporated into cell membranes. We used intraglomerular mesangial cells (MES13) that are sensitive to treatment with Ketorolac or Gentamicin instead of proximal tubular cells which do not respond to Ketorolac. We found a significant inhibition of Ketorolac (0.25, 0.5, 1 mM) or Gentamicin (2.5, 5 mM) induced cytotoxicity after pretreatment of MES13 cells with 0.01% of 20%w/v LipOmega-3 Emulsion 9/1, containing 90:10 wt/wt mixture of fish oil derived triglycerides to medium chain triglycerides.

A comparison of BGM and LLC-PK1 cells for the evaluation of nephrotoxicity

Nephrotoxicity is one of the most frequent effects observed after the use of medicine. Such situations have been tardily discovered because of existing methods to determine toxicity. The validation of sensitive, alternative methods for the early identification of toxic effects is as important as restrictions on the use of animals. In this light, the present study evaluated the effects of gentamicin on BGM and LLC-PK1 cells, using MTT and Neutral Red (NR). Although the LLC-PK1 cell line is used for toxicological studies, the BGM cell line is relatively new for this purpose. MTT (BGM: EC(50) = 6.29 mM; LLC-PK1: EC(50) = 8.01 mM) was found to be more sensitive than NR (EC(50) was greater than 10 mM for both cells). By using MTT, both cells demonstrated the involvement of mitochondria in a manner that was dose dependent, with an apoptotic process occurring at the concentrations of 1 and 3 mM and necrosis at concentrations above 4 mM. It could, therefore, be concluded that 1) BGM appears to be useful in the study of the mechanism of nephrotoxicity caused by gentamicin and 2) because of its sensitivity to MTT, in addition to its ease of manipulation, it is believed that the BGM cell line can also be used as an alternative method to evaluate nephrotoxicity.

Effect of Taurine on the antimicrobial efficiency of Gentamicin

CONTEXT

Gentamicin is mainly used in severe infections caused by gram-negatives. However toxicity including nephrotoxicity and ototoxicity is one of the most important complications of its treatment. The production of free radicals seems to be involved in gentamicin toxicity mechanism. Taurine, a major intracellular free β-amino acid, is known to be an endogenous antioxidant. So potentially the co-therapy of taurine and gentamicin would reduce the adverse effects of the antibiotic.

OBJECTIVES

In this study, we wished to know the effect of taurine on the antibiotic capacity of gentamicin.

METHODS

strainsof P. aeruginosa, E. coli, S. aureus and S. epidermidis were used as test organisms. Minimum inhibitory concentrations of gentamicin in the presence and absence of taurine at quantities from 40 to 2 mg/L were determined using macro-dilution method.

RESULTS

MICs were determined in the various concentrations of taurine for bacterial indicators. The MIC values of gentamicin for P. aeruginosa, S. aureus and E. coli remained unchanged in the values of 2.5, 5 and 20 μg/ml respectively in the absence and presences of different concentrations of taurine. The bactericidal activity of gentamicin against S. epidermidis was increased by addition of taurine in the concentrations higher than 6 mg/L.

CONCLUSION

According to our study the antibacterial activity of gentamicin against the indicator microorganisms were not interfere with taurine at selected concentrations. Further in vivo studies are needed to establish if a combination of gentamicin and taurine would have the same effect.

Urinary Activities of Proximal Tubule Enzymes in Neonates Treated with Gentamicin

In order to determine the nephrotoxicity of gentamicin, an aminoglycoside antibiotic, activity of the enzymes dominantly localized in proximal tubules, i.e. alanine aminopeptidase (AAP), γ-glutamyl transferase (GGT) and N-acetylβ-D-glucosaminidase (NAG) was examined. Determinations were performed in 12-h urine samples of 30 neonates i.v. receiving gentamicin against Gram negative infections in daily doses of 5.0 mg/kg body mass for 10 consecutive days. The activities of the same enzymes were measured in 12-h urine samples of 30 examinées of the control group. The groups consisted of neonates of both sexes. The pretreatment period lasted for 5 days. On day 8 of gentamicin application, statistically significant differences in the activity of AAP and GGT expressed in U/mmol creatinine between the gentamicin-receiving and control group (p<0.01) were found. No significant differences in NAG activity of the gentamicin-treated group in comparison with the control were recorded during the 10-day gentamicin therapy. It can be concluded that 10-day treatment of neonates with usually prescribed gentamicin doses results in mild nephrotoxic changes close to the end of the therapy accompanied by increased activity of both urinary AAP and GGT, known as very sensitive indicators of nephrotoxicity. During the same treatment period no changes in NAG activity were observed, meaning that the antibiotic causes no severe injuries to proximal tubule cells at the level of cellular organelles.

Urinary clinical pathologic findings and glomerular filtration rate in the horse

Urinary specific gravity (USG) measurements are underused by equine ambulatory veterinarians. Urinary dipstick and USG findings can assist in the diagnosis and prognosis of many disease processes in the horse. Simple methods for measurement of the glomerular filtration rate and urinary biochemical markers can improve equine urinary diagnostic abilities in critical care patients. Fractional excretion of electrolytes and minerals assists in fluid care and in management of nutrition of horses.

Food flavor cinnamaldehyde-induced biochemical and histological changes in the kidney of male albino wistar rat

Rats were given food flavor cinnamaldehyde (CNMA) orally by gavage at the dose of 2.14, 6.96, 22.62 and 73.5mg/kg body weight/day for 10, 30 and 90 days. Only the group of rats treated with CNMA at the dose 73.5mg/kg body weight/day for 90 days showed histological changes in the kidney followed by increased activities of renal, serum and urinary enzymes. CNMA-induced glucosuria in these rats was accompanied by marked proteinuria and creatinuria. Increased serum blood urea nitrogen and serum creatinine and decreased serum protein and glucose levels were observed in these rats. Thus, CNMA at the dose of 73.5mg/kg body weight/day for 90 days exert its effect on kidney of male albino wistar rat and its effect is time and dose dependent.

Toxins affecting the urinary system

Many different substances can induce toxic damage to various structural components of the equine kidney, and most lack pathognomonic signs. Some of these agents have specific treatments, although many do not. Supportive and symptomatic therapy is an important aspect of treatment of most cases of equine nephrotoxicosis. Regardless of cause, if the toxic substance is removed or neutralized before significant renal damage, full recovery of renal function may occur. Many horses already have significant renal damage before a definitive diagnosis is made, and the prognosis for full recovery thus remains guarded.

Detecting early kidney damage in horses with colic by measuring matrix metalloproteinase -9 and -2, other enzymes, urinary glucose and total proteins

Background

The aim of the study was to investigate urine matrix metalloproteinase (MMP-2 and -9) activity, alkaline phosphatase/creatinine (U-AP/Cr) and gamma-glutamyl-transpeptidase/creatinine (U-GGT/Cr) ratios, glucose concentration, and urine protein/creatinine (U-Prot/Cr) ratio and to compare data with plasma MMP-2 and -9 activity, cystatin-C and creatinine concentrations in colic horses and healthy controls. Horses with surgical colic (n = 5) were compared to healthy stallions (n = 7) that came for castration. Blood and urine samples were collected. MMP gelatinolytic activity was measured by zymography.

Results

We found out that horses with colic had significantly higher urinary MMP-9 complex and proMMP-9 activities than horses in the control group. Colic horses also had higher plasma MMP-2 activity than the control horses. Serum creatinine, although within reference range, was significantly higher in the colic horses than in the control group. There was no significant increase in urinary alkaline phosphatase, gamma-glutamyltranspeptidase or total proteins in the colic horses compared to the control group. A human cystatin-C test (Dako Cytomation latex immunoassay^® based on turbidimetry) did not cross react with equine cystatin-C.

Conclusion

The results indicate that plasma MMP-2 may play a role in the pathogenesis of equine colic and urinary MMP-9 in equine kidney damage.