Refinement of systemic guinea pig deafening in hearing research: Sensorineural hearing loss induced by co-administration of kanamycin and furosemide via the leg veins.

Auditory disabilities have a large impact on the human population worldwide. Research into understanding and treating hearing disabilities has increased significantly in recent years. One of the most relevant animal species in this context is the guinea pig, which has to be deafened to study several of the hearing pathologies and develop novel therapies. Applying kanamycin subcutaneously and furosemide intravenously is a long-established method in hearing research, leading to permanent hearing loss without surgical intervention at the ear. The intravenous application of furosemide requires invasive surgery in the cervical area of the animals to expose the jugular vein, since a relatively large volume (1 ml per 500 g body weight) must be injected over a period of about 2.5 min. We have established a gentler alternative by applying the furosemide by puncture of the leg veins. For this, custom-made cannula-needle devices were built to allow the vein puncture and subsequent slow injection of the furosemide. This approach was tested in 11 guinea pigs through the foreleg via the cephalic antebrachial vein and through the hind leg via the saphenous vein. Frequency-specific hearing thresholds were measured before and after the procedure to verify normal hearing and successful deafening, respectively. The novel approach of systemic deafening was successfully implemented in 10 out of 11 animals. The Vena saphena was best suited to the application. Since the animals' condition, post leg vein application, was better in comparison to animals deafened by exposure of the Vena jugularis, the postulated refinement that reduced animal stress was deemed successful.

The ototoxic effect of locally applied kanamycin and furosemide in guinea pigs.

BACKGROUND: Hearing impairment is a growing social and economic issue. New technical or biological approaches aiming hearing rehabilitation or regeneration require animal testing. Therefore, a reproducible and safe model for hearing-impaired animals is essential. NEW METHOD: Intratympanic injection of kanamycin and furosemide was administered for BFA bunt pigmented guinea pigs for either 1 or 2 h. Hearing loss was regularly measured with compound action potential response to click and tone burst stimuli for up to 26 weeks. Hair cell loss and the density of spiral ganglion neurons were histologically analyzed. RESULTS: One week after the exposure, complete hearing loss was observed in 34 ears from the 36 ears treated for 2 h and remained stable during the follow-up. Histology revealed near complete hair cell loss and secondary degeneration of spiral ganglion neurons. COMPARISON WITH EXISTING METHODS: Animal deafening is usually achieved by systemic application of aminoglycoside antibiotics or chemotherapy drugs, although side effects such as nephrotoxicity may occur which can be avoided by local application. With our procedure, unilateral hearing loss model can also be established. CONCLUSIONS: The single intratympanic application of a solution of 200 mg/ml kanamycin and 50 mg/ml furosemide is a stable and reliable deafening method.

Impact of drug-resistant tuberculosis treatment on hearing function in South African adults: Bedaquiline versus kanamycin.

BACKGROUND: Ototoxicity linked to medications used to treat tuberculosis (TB) remains a global challenge. OBJECTIVES: The aim was to describe the audiological function in a group of adults with drug-resistant tuberculosis (DR-TB) on bedaquiline (G-BDQ) treatment attending a TB hospital in South Africa and compare this with patients on kanamycin (G-KCIN). METHODS: A quantitative paradigm was adopted within a non-experimental retrospective record review design. The sample consisted of 30 records of adults with DR-TB between the ages of 18 and 50 years, recruited from a Tropical Diseases Hospital in South Africa. Data were analysed through both descriptive and inferential statistical measures. RESULTS: Clear and statistically significant differences in the audiological function were found between the two groups. The group receiving G-KCIN presented with ototoxicity that was clearly demonstrated by sensorineural hearing loss of high-frequency worsening of thresholds in over 73% of the records, which was statistically (p 0.05) and clinically significant, over the three testing sessions, demonstrating the cumulative effects of dosage. Increased evidence of tinnitus was also found in this group. The group receiving G-BDQ presented with neither statistically (p 0.05) nor clinically significant changes in hearing thresholds across all frequencies over the same monitoring timeframe. Additionally, only one report (7%) of tinnitus was found in this group. CONCLUSION: The results indicating that bedaquiline does not cause hearing loss when compared with G-KCIN highlight the need for increased availability of bedaquiline for the treatment of DR-TB within the South African context, to preserve both the quantity and quality of life of those infected.

Generation of Cochlear Hair Cells from Sox2 Positive Supporting Cells via DNA Demethylation.

Regeneration of auditory hair cells in adult mammals is challenging. It is also difficult to track the sources of regenerated hair cells, especially in vivo. Previous paper found newly generated hair cells in deafened mouse by injecting a DNA methyltransferase inhibitor 5-azacytidine into the inner ear. This paper aims to investigate the cell sources of new hair cells. Transgenic mice with enhanced green fluorescent protein (EGFP) expression controlled by the Sox2 gene were used in the study. A combination of kanamycin and furosemide was applied to deafen adult mice, which received 4 mM 5-azacytidine injection into the inner ear three days later. Mice were followed for 3, 5, 7 and 14 days after surgery to track hair cell regeneration. Immunostaining of Myosin VIIa and EGFP signals were used to track the fate of Sox2-expressing supporting cells. The results show that (i) expression of EGFP in the transgenic mice colocalized the supporting cells in the organ of Corti, and (ii) the cell source of regenerated hair cells following 5-azacytidine treatment may be supporting cells during 5-7 days post 5-azacytidine injection. In conclusion, 5-azacytidine may promote the conversion of supporting cells to hair cells in chemically deafened adult mice.

Etiology of Childhood Bilateral Sensorineural Hearing Loss in Shandong Province, China.

Objectives The purpose of this study is to ascertain the etiology of bilateral sensorineural hearing loss (SNHL) in children aged ≤ 18 years living in Shandong province. Method Data were taken from a cross-sectional study, which was conducted between 2015 and 2017. The study included children aged ≤ 18 years, recruited from special schools for children with hearing loss and from hearing rehabilitation centers in Shandong province of China. Children were screened for bilateral SNHL through audiological testing. Clinical examination, genetic testing, and structured interviews were conducted for those children who were identified as having hearing loss to identify the potential cause. Results The etiology of bilateral SNHL in our sample was genetic in 874 (39.3%), acquired in 650 (29.3%), and unknown in 697 (31.4%) children. Among children with acquired SNHL, the cause was maternal viral infection in 75 (11.5%); perinatal factors in 238 (36.6%); meningitis, measles, and mumps in 146 (22.5%); and ototoxic exposure in 117 (18%) children. Among the children with genetic SNHL, only 44 (4.9%) were identified as having syndromic hearing loss, and the remainder (95.1%) were classified as nonsyndromic hearing loss. Conclusion The findings indicated that nearly 30% of bilateral SNHL in Shandong province could be preventable through immunization, early prenatal diagnosis, proper treatment of infections, and avoidance of prescription of ototoxic drugs. This finding emphasizes the need for programs aimed at improving the health services at primary and secondary levels of health care, which will in turn prevent childhood hearing loss.

Prevalence of Pre-Existing Hearing Loss Among Patients With Drug-Resistant Tuberculosis in South Africa.

Purpose Hearing loss, resulting from aminoglycoside ototoxicity, is common among patients with drug-resistant tuberculosis (DR-TB). Those with pre-existing hearing loss are at particular risk of clinically important hearing loss with aminoglycoside-containing treatment than those with normal hearing at baseline. This study aimed to identify factors associated with pre-existing hearing loss among patients being treated for DR-TB in South Africa. Method Cross-sectional analysis nested within a cluster-randomized trial data across 10 South African TB hospitals. Patients ≥ 13 years old received clinical and audiological evaluations before DR-TB treatment initiation. Results Of 936 patients, average age was 35 years. One hundred forty-two (15%) reported pre-existing auditory symptoms. Of 482 patients tested by audiometry, 290 (60%) had pre-existing hearing loss. The prevalence of pre-existing hearing loss was highest among patients ≥ 50 years (adjusted prevalence ratio [aPrR] for symptoms 5.53, 95% confidence interval (CI) [3.63, 8.42]; aPrR for audiometric hearing loss 1.63, 95% CI [1.31, 2.03] compared to age 13-18 years) and among those with a prior history of second-line TB treatment (aPrR for symptoms 1.73, 95% CI [1.66, 1.80]; PrR for audiometric hearing loss 1.33, 95% CI [1.03, 1.73]). Having HIV with cluster of differentiation 4 cell count < 200 cells/mm3 and malnutrition were risk factors but did not reach statistical significance in adjusted analyses. Conclusion Pre-existing hearing loss is common among patients presenting for DR-TB treatment in South Africa, and those older than the age of 50 years or who had prior second-line TB treatment history were at highest risk.

[Kanamycin-induced ototoxicity during treatment of multidrug-resistant tuberculosis]. / Ototoxicité liée à la kanamycine au cours du traitement de la tuberculose multirésistante.

INTRODUCTION: Aminoglycosides are commonly used in the treatment of multidrug-resistant tuberculosis (MDR-TB). Their use can cause ototoxicity with irreversible hearing loss. The aim of this study was to determine the incidence and to identify factors associated to kanamycin-induced ototoxicity during MDR-TB treatment in Yaounde. METHODS: The records of patients hospitalized in the pulmonology department of the Jamot Hospital of Yaounde between May 2008 and July 2015 (7 years) for treatment of MDR-TB with regimens containing kanamycin were analyzed. Logistic regression was used to identify for factors associated with ototoxicity during this treatment. RESULTS: Of the 79 patients included, 60.7% were male and their median age (25th-75th percentile) was 31 (25-43) years. Eighteen (22.8%) patients had HIV infection. During treatment, the incidence of kanamycin-induced ototoxicity [95% confidence interval (95% CI)] was 36.7 (26.9-47.7) %. Factors independently associated with this ototoxicity [odds ratio (95% CI)] during MDR-TB treatment were age>40 years [13.47 (3.66-49.49)] and a body mass index<18.5kg/m2 [4.58 (1.36-15.44)]. CONCLUSION: The incidence of kanamycin-induced ototoxicity during MDR-TB treatment is relatively high. Taking these factors into consideration at the initiation of MDR-TB treatment would allow to reduce the occurrence of irreversible functional impairment induced by the treatment of MDR-TB.

Pharmacokinetics and other risk factors for kanamycin-induced hearing loss in patients with multi-drug resistant tuberculosis.

Objective: The toxicity associated with the use of kanamycin includes irreversible hearing loss. There are limited data describing the relationship between hearing loss and kanamycin pharmacokinetics (PK). We explored the association of kanamycin PK with hearing loss in patients on MDR-TB treatment.Design: We prospectively recruited patients on kanamycin-based MDR-TB treatment in Cape Town. Hearing thresholds from 0.25 to 16 kHz were tested at baseline and at 4, 8 and 12 weeks. We determined kanamycin concentrations at steady-state in serial plasma samples over 10 h, and explored factors associated with hearing loss.Study sample: One hundred and two participants including 58 (56.9%) men had analysable audiometric data; median age was 34.9 years, 65 (63.7%) were HIV-positive, and 24 (23.5%) had been treated for MDR-TB previously.Results: Eighty-four participants (82.4%) developed hearing loss. We found a 3% (95% CI: 1-6%, p = 0.028) increased risk of cochleotoxicity for each 10 µg h/L increase in 0-10 h AUC.Conclusion: We describe a high incidence of hearing loss in MDR-TB patients treated with kanamycin, with higher AUC0-10 significantly associated with hearing loss.

Nephrotoxicity and ototoxic symptoms of injectable second-line anti-tubercular drugs among patients treated for MDR-TB in Ethiopia: a retrospective cohort study.

BACKGROUND: Nephrotoxicity and ototoxicity are clinically significant dose-related adverse effects associated with second-line anti-tubercular injectables drugs (aminoglycosides and capreomycin) used during intensive phase of treatment of multi-drug resistant tuberculosis (MDR-TB) patients. Data are scarce on injectable-induced nephrotoxicity and ototoxicity in Ethiopian MDR-TB patients. The aim of this study was to assess the prevalence, management of nephrotoxicity and ototoxic symptoms and treatment outcomes of patients treated for MDR-TB with injectable-based regimens. METHOD: This was retrospective cohort study based on review of medical records of about 900 patients on MDR-TB treatment from January 2010 to December 2015 at two large TB referral hospitals in Addis Ababa, Ethiopia. Nephrotoxicity in study participants was screened using baseline and monthly measurement of serum creatinine and clinical diagnosis and patient reports. RESULTS: Overall, 473 (54.2%) of participants were male. Children accounted for 47 (5.5%) of cases and the mean age of participants was 32 ± 12.6 years with range of 2-75 years. The majority (n = 788, 84.6%) of participants had past history of TB. The most commonly used injectable anti-TB drug was capreomycin (n = 789, 84.7%), while kanamycin and amikacin were also used. There was a statistically significant increment (p<0.05) in the mean serum creatinine values from baseline throughout intensive phase of treatment with a 10-18% prevalence of nephrotoxicity. Based on clinical criteria, nephrotoxicity was detected in 62 (6.7%) and ototoxic symptoms were detected in 42 (4.8%) participants. Nephrotoxicity and ototoxic symptoms were clinically managed by modification of treatment regimens including dose and frequency of drug administration. CONCLUSION: Nephrotoxicity and ototoxic symptoms were significant problems among patients on follow-up for MDR-TB treatment. Based on laboratory criteria (serum creatinine), nephrotoxicity remained significant adverse events throughout intensive phase of treatment, indicating close monitoring of patients for successful outcome is mandatory until countries adopt the recent injectable-free WHO guideline and under specific conditions.

Treatment Outcomes of Patients Switching From an Injectable Drug to Bedaquiline During Short Standardized Treatment for Multidrug-resistant Tuberculosis in Mozambique.

Bedaquiline was recommended by the World Health Organization as the preferred option in treatment of multidrug-resistant tuberculosis (MDR-TB) with long regimens. However, no recommendation was given for the short MDR-TB regimen. Data from our small cohort of patients who switched from injectable drug to bedaquiline suggest that a bedaquiline-based short regimen is effective and safe.

Endoplasmic reticulum stress is involved in spiral ganglion neuron apoptosis following chronic kanamycin-induced deafness.

Aminoglycoside antibiotics-induced hearing loss is a common sensorineural impairment. Spiral ganglion neurons (SGNs) are first-order neurons of the auditory pathway and are critical for the maintenance of normal hearing. In the present study, we investigated the time-course of morphological changes and the degeneration process of spiral ganglion cells (SGCs) following chronic kanamycin-induced deafness and determined whether the endoplasmic reticulum (ER) stress was involved in the degeneration of SGNs. We detected density changes in SGCs and the expressions of Bip, inositol requirement 1 (IRE1)α, activating transcription factor-6α, p-PERK, p-eIF2α, CHOP, and caspase-12 at each time point after kanamycin treatment. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining was also performed. The number of SGC deletions reached ∼50% at the 70th day after kanamycin administration and the ER of most SGCs were dilated. The expression of p-PERK, p-eIF2α, p-IRE1α, Bip, caspase-12, and Chop was significantly unregulated after kanamycin treatment. The number of SGCs that were positive for both TUNEL and caspase-12 increased from day 7 to 28. Taken together, these data demonstrate that ER stress was involved in kanamycin-induced apoptosis of SGNs. Kanamycin-induced SGN apoptosis is mediated, at least in part, by ER stress-induced upregulation of CHOP and caspase-12.

The Novel Peptide Vaccine GV1001 Protects Hearing in a Kanamycin-induced Ototoxicity Mouse Model.

HYPOTHESIS: We tested whether GV1001 has any ototoxic side effects at different doses and whether it protects hearing in an aminoglycoside-induced ototoxicity mouse model. BACKGROUND: GV1001, a novel peptide vaccine currently being examined in a Phase 3 clinical trial to treat pancreatic cancer, also has anti-inflammatory and antioxidant effects. METHODS: In the first experiment, C57/BL6 mice were injected with GV1001 preparations at concentrations of 0.1 to 100 mg/kg for 7 days to evaluate the toxicity of GV1001 on the inner ear and kidneys. In the second experiment, the protective effect of GV1001 was tested in an ototoxicity mouse model that was generated by injecting 800 mg/kg kanamycin (KM) for 2 weeks. The hearing threshold and hair cell loss were compared between the KM + GV1001 group (treated with 10 mg/kg GV1001 for 2 wk) and the KM + saline group. The hearing threshold was measured before, and 7, 14, and 21 days after the initial treatment. The blood urea nitrogen level was measured. RESULTS: No ototoxicity or renal toxicity was found following treatment with different doses of GV1001 (0.1-100 mg/kg). The KM + saline group showed impaired auditory function and markedly disoriented and missing cochlear hair cells, while the KM + GV1001 group showed significant hearing and hair cell preservation in comparison (p < 0.05). CONCLUSION: GV1001 itself did not have any detrimental effects on the inner ear or kidney. In the KM induced ototoxicity model, concomitant administration of GV1001 protected against cochlear hair cell damage and preserve hearing.

Cycloserine Induced Suicidal Tendencies and Kanamycin Induced Ototoxicity in Indian MDR-TB Patient: A Case Report.

INTRODUCTION: Cycloserine and Kanamycin are approved for treatment of multidrug-resistant tuberculosis with good tolerability in Tuberculosis patients and have various labeled adverse reactions but the neuropsychiatric adverse drug reactions with cycloserine are rarely explained. CASE REPORT: We present a case report on Cycloserine induced Suicidal tendencies and Kanamycin induced decrease in hearing sensation in Indian MDR-TB patient. A 55-year-old male patient who was diagnosed with MDR-TB was prescribed with category IV anti-tubercular therapy. Within one month of initiation of therapy, he developed repeated suicidal thoughts, joint pain, restlessness, depression, constipation, insomnia, tinnitus and a decrease in hearing sensation. RESULTS AND DISCUSSION: Cycloserine and kanamycin were closely associated with suicidal tendency and tinnitus followed by a decrease in hearing sensations respectively. On causality assessment using WHO-UMC Causality assessment scale, Adverse Drug Reaction with Cycloserine was found to be certain and for kanamycin, ADR was found to be possible. CONCLUSION: Early management of such fatal ADR can improve the compliance, thus preventing the relapse of infection as well as improving therapeutic outcome in Tuberculosis patients.

Secondary Degeneration of Auditory Neurons after Topical Aminoglycoside Administration in a Gerbil Model.

Hair cells in the cochlea can be damaged by various causes. Damaged hair cells can lead to additional destruction of parts of the auditory afferent pathway sequentially, which is called secondary degeneration. Recently, researches regarding cochlear implants have been actively carried out for clinical purposes; secondary degeneration in animals is a much more practical model for identifying the prognosis of cochlear implants. However, an appropriate model for this research is not established yet. Thus, we developed a secondary degeneration model using an ototoxic drug. 35 gerbils were separated into four different groups and kanamycin was applied via various approaches. ABR was measured several times after drug administration. SGCs were also counted to identify any secondary degeneration. The results showed that outer and inner HCs were damaged in all kanamycin-treated groups. Twelve weeks after kanamycin treatment, the round window membrane injection group showed severe subject differences in hair cells and SGC damage, whereas the gelfoam group showed consistent and severe damage in hair cells and SGCs. In this study, we successfully induced secondary degeneration in hair cells in a gerbil model. This model can be used for various purposes in the hearing research area either for treatment or for preservation.

Risk of Nephrotoxicity in Patients With Drug-Resistant Tuberculosis Treated With Kanamycin/Capreomycin With or Without Concomitant Use of Tenofovir-Containing Antiretroviral Therapy.

BACKGROUND: The intersection of HIV and drug-resistant (DR) tuberculosis (TB) presents the challenge of managing convergent drug toxicities. METHODS: We conducted a retrospective study of adult patients with DR-TB treated with a kanamycin/capreomycin-based (KM) regimen, with or without concomitant antiretroviral therapy (ART). We estimated the incidence of nephrotoxicity (defined as an increase in serum creatinine greater than 26.5 µmol, or an increase in serum creatinine to 1.5 times the baseline value, or a decline in glomerular filtration rate to less than 60 mL/min/1.73 m), and evaluated the association between reported drug use and nephrotoxicity using Kaplan-Meier plots. RESULTS: A total of 215 patients with DR-TB were treated with a kanamycin/capreomycin-based regimen, with or without concomitant ART. The incidence rate of nephrotoxicity was 3.6 [95% confidence interval (CI): 1.4 to 7.3], 6.9 (95% CI: 5.2 to 9.0), and 12 (95% CI: 3.3 to 30.9) cases per 100 person-months of follow-up in the KM only group (n = 42), the KM + TDF (tenofovir disoproxil fumarate) group (n = 163), and the KM + Other ART group (n = 10), respectively. Using the KM only group as a reference, the hazard ratio was 2.06 (95% CI: 0.92 to 4.63) in the KM + TDF group, and 4.09 (95% CI: 1.17 to 14.25) in the KM + Other ART group. Advancing age was an independent predictor of nephrotoxicity (adjusted hazard ratio 1.29, 95% CI: 1.14 to 1.46). CONCLUSIONS: Our findings provide evidence of a significant risk of nephrotoxicity during treatment with a kanamycin/capreomycin-based DR-TB regimen, with or without concurrent treatment with ART. This study lends further support to calls for the substitution of TDF during the intensive phase of DR-TB treatment and for close monitoring of renal function during DR-TB treatment, especially in settings where the use of kanamycin/capreomycin is unavoidable.

Human mesenchymal stromal cell therapy for damaged cochlea repair in nod-scid mice deafened with kanamycin.

BACKGROUND: Kanamycin, mainly used in the treatment of drug-resistant-tuberculosis, is known to cause irreversible hearing loss. Using the xeno-transplant model, we compared both in vitro and in vivo characteristics of human mesenchymal stromal cells (MSCs) derived from adult tissues, bone marrow (BM-MSCs) and adipose tissue (ADSCs). These tissues were selected for their availability, in vitro multipotency and regenerative potential in vivo in kanamycin-deafened nod-scid mice. METHODS: MSCs were isolated from informed donors and expanded ex vivo. We evaluated their proliferation capacity in vitro using the hexosaminidase assay, the phenotypic profile using flow-cytometry of a panel of surface antigens, the osteogenic potential using alkaline phosphatase activity and the adipogenic potential using oil-red-O staining. MSCs were intravenously injected in deafened mice and cochleae, liver, spleen and kidney were sampled 7 and 30 days after transplantation. The dissected organs were analyzed using lectin histochemistry, immunohistochemistry, polymerase chain reaction (PCR) and dual color fluorescence in situ hybridization (DC-FISH). RESULTS: MSCs showed similar in vitro characteristics, but ADSCs appeared to be more efficient after prolonged expansion. Both cell types engrafted in the cochlea of damaged mice, inducing regeneration of the damaged sensory structures. Several hybrid cells were detected in engrafted tissues. DISCUSSION: BM-MSCs and ADSCs showed in vitro characteristics suitable for tissue regeneration and fused with resident cells in engrafted tissues. The data suggest that paracrine effect is the prevalent mechanism inducing tissue recovery. Overall, BM-MSCs and ADSCs appear to be valuable tools in regenerative medicine for hearing loss recovery.

Modulation of Global Transcriptional Regulatory Networks as a Strategy for Increasing Kanamycin Resistance of the Translational Elongation Factor-G Mutants in Escherichia coli.

Evolve and resequence experiments have provided us a tool to understand bacterial adaptation to antibiotics. In our previous work, we used short-term evolution to isolate mutants resistant to the ribosome targeting antibiotic kanamycin, and reported that Escherichia coli develops low cost resistance to kanamycin via different point mutations in the translation Elongation Factor-G (EF-G). Furthermore, we had shown that the resistance of EF-G mutants could be increased by second site mutations in the genes rpoD/cpxA/topA/cyaA Mutations in three of these genes had been discovered in earlier screens for aminoglycoside resistance. In this work, we expand our understanding of these second site mutations, the goal being to understand how these mutations affect the activities of the mutated gene products to confer resistance. We show that the mutation in cpxA most likely results in an active Cpx stress response. Further evolution of an EF-G mutant in a higher concentration of kanamycin than what was used in our previous experiments identified the cpxA locus as a primary target for a significant increase in resistance. The mutation in cyaA results in a loss of catalytic activity and probably results in resistance via altered CRP function. Despite a reduction in cAMP levels, the CyaAN600Y mutant has a transcriptome indicative of increased CRP activity, pointing to an unknown role for CyaA and / or cAMP in gene expression. From the transcriptomes of double and single mutants, we describe the epistasis between the mutation in EF-G and these second site mutations. We show that the large scale transcriptomic changes in the topoisomerase I (FusAA608E-TopAS180L) mutant likely result from increased negative supercoiling in the cell. Finally, genes with known roles in aminoglycoside resistance were present among the misregulated genes in the mutants.

Reduced Chance of Hearing Loss Associated with Therapeutic Drug Monitoring of Aminoglycosides in the Treatment of Multidrug-Resistant Tuberculosis.

Hearing loss and nephrotoxicity are associated with prolonged treatment duration and higher dosage of amikacin and kanamycin. In our tuberculosis center, we used therapeutic drug monitoring (TDM) targeting preset pharmacokinetic/pharmacodynamic (PK/PD) surrogate endpoints in an attempt to maintain efficacy while preventing (oto)toxicity. To evaluate this strategy, we retrospectively evaluated medical charts of tuberculosis (TB) patients treated with amikacin or kanamycin in the period from 2000 to 2012. Patients with culture-confirmed multiresistant or extensively drug-resistant tuberculosis (MDR/XDR-TB) receiving amikacin or kanamycin as part of their TB treatment for at least 3 days were eligible for inclusion in this retrospective study. Clinical data, including maximum concentration (Cmax), Cmin, and audiometry data, were extracted from the patients' medical charts. A total of 80 patients met the inclusion criteria. The mean weighted Cmax/MIC ratios obtained from 57 patients were 31.2 for amikacin and 12.3 for kanamycin. The extent of hearing loss was limited and correlated with the cumulative drug dose per kg of body weight during daily administration. At follow-up, 35 (67.3%) of all patients had successful outcome; there were no relapses. At a median dose of 6.5 mg/kg, a correlation was found between the dose per kg of body weight during daily dosing and the extent of hearing loss in dB at 8,000 Hz. These findings suggest that the efficacy at this lower dosage is maintained with limited toxicity. A randomized controlled trial should provide final proof of the safety and efficacy of TDM-guided use of aminoglycosides in MDR-TB treatment.

Clinical predictors of aminoglycoside-induced ototoxicity in drug-resistant Tuberculosis patients on intensive therapy.

OBJECTIVE: The study objectives were to determine the incidence of aminoglycoside-induced ototoxicity in institutionalized patients on intensive phase of therapy for drug-resistant Tuberculosis (DR Tb) and also to assess clinical factors which could predict the ototoxicity. METHODS: The study was a prospective analytical study among consecutive DR Tb patients who were admitted for intensive phase of therapy (of 4 months) at the DR-Tb center over a 12-month period. Patients were diagnosed as DR Tb using the Gene Xpert machine to confirm Rifampicin resistance. All eligible 70 out of 87 consenting patients were consecutively recruited into the study. Patients had baseline (admission) and serial pure tone audiometries (PTAs) performed at 4 weekly intervals until discharge after 4 months of admission. Audiometric confirmation of aminoglycoside-induced ototoxicity was done by comparing serial with baseline PTA. RESULTS: Among the 70 patients the male:female ratio was 1.7:1. Nine patients (12.9%) were retroviral-positive, and 16 patients (22.9%) were confirmed to have ototoxicity by audiometric criteria. The duration of treatment when ototoxicity was detected in the patients ranged 4-17 (Mean±SD; 9.4±3.4) weeks. Ototoxicity was detected in the audiometric low frequency ranges in 7 (43.8%) and at the high frequencies in 4 (25.0%) of the patients. Univariate analyses of clinical parameters found that age, underlying diabetes mellitus, deranged baseline PTAv >25dB HL, BMI on admission and retroviral status were significantly associated, while sex and previous drug regimen failure were not associated with ototoxicity. Multivariate adjusted logistic regression analyses, controlling for sex, revealed age (OR=1.068, p=0.018), BMI on admission (OR=0.673, p=0.012) and retroviral positivity (OR=8.822, p=0.014) of patients could significantly predict aminoglycoside-induced ototoxicity. CONCLUSION: Incidence of aminoglycoside-induced ototoxicity in DR Tb patients was 22.9%. The clinical predictors for ototoxicity were age, BMI on admission, and co-existing retroviral infection in the patients. Clinicians should consider these factors in making choices of aminoglycosides to be used during intensive phase of treatment with second line anti-Tuberculous therapy.