Aminoglycosides

Investigating inhibitors of 1-deoxy-d-xylulose 5-phosphate synthase in a mouse model of UTI

The rising rate of antimicrobial resistance continues to threaten global public health. Further hastening antimicrobial resistance is the lack of new antibiotics against new targets. The bacterial enzyme, 1-deoxy-d-xylulose 5-phosphate synthase (DXPS), is thought to play important roles in central metabolism, including processes required for pathogen adaptation to fluctuating host environments. Thus, impairing DXPS function represents a possible new antibacterial strategy. We previously investigated a DXPS-dependent metabolic adaptation as a potential target in uropathogenic Escherichia coli (UPEC) associated with urinary tract infection (UTI), using the DXPS-selective inhibitor butyl acetylphosphonate (BAP). However, investigations of DXPS inhibitors in vivo have not been conducted. The goal of the present study is to advance DXPS inhibitors as in vivo probes and assess the potential of inhibiting DXPS as a strategy to prevent UTI in vivo. We show that BAP was well-tolerated at high doses in mice and displayed a favorable pharmacokinetic profile for studies in a mouse model of UTI. Further, an alkyl acetylphosphonate prodrug (homopropargyl acetylphosphonate, pro-hpAP) was significantly more potent against UPEC in urine culture and exhibited good exposure in the urinary tract after systemic dosing. Prophylactic treatment with either BAP or pro-hpAP led to a partial protective effect against UTI, with the prodrug displaying improved efficacy compared to BAP. Overall, our results highlight the potential for DXPS inhibitors as in vivo probes and establish preliminary evidence that inhibiting DXPS impairs UPEC colonization in a mouse model of UTI.IMPORTANCENew antibiotics against new targets are needed to prevent an antimicrobial resistance crisis. Unfortunately, antibiotic discovery has slowed, and many newly FDA-approved antibiotics do not inhibit new targets. Alkyl acetylphosphonates (alkyl APs), which inhibit the enzyme 1-deoxy-d-xylulose 5-phosphate synthase (DXPS), represent a new possible class of compounds as there are no FDA-approved DXPS inhibitors. To our knowledge, this is the first study demonstrating the in vivo safety, pharmacokinetics, and efficacy of alkyl APs in a urinary tract infection mouse model.

RavA-ViaA antibiotic response is linked to Cpx and Zra2 envelope stress systems in Vibrio cholerae

IMPORTANCE

The RavA-ViaA complex was previously found to sensitize Escherichia coli to aminoglycosides (AGs) in anaerobic conditions, but the mechanism is unknown. AGs are antibiotics known for their high efficiency against Gram-negative bacteria. In order to elucidate how the expression of the ravA-viaA genes increases bacterial susceptibility to aminoglycosides, we aimed at identifying partner functions necessary for increased tolerance in the absence of RavA-ViaA, in Vibrio cholerae. We show that membrane stress response systems Cpx and Zra2 are required in the absence of RavA-ViaA, for the tolerance to AGs and for outer membrane integrity. In the absence of these systems, the ∆ravvia strain's membrane becomes permeable to external agents such as the antibiotic vancomycin.

ISPD peritonitis guideline recommendations: 2022 update on prevention and treatment

Peritoneal dialysis (PD)-associated peritonitis is a serious complication of PD and prevention and treatment of such is important in reducing patient morbidity and mortality. The ISPD 2022 updated recommendations have revised and clarified definitions for refractory peritonitis, relapsing peritonitis, peritonitis-associated catheter removal, PD-associated haemodialysis transfer, peritonitis-associated death and peritonitis-associated hospitalisation. New peritonitis categories and outcomes including pre-PD peritonitis, enteric peritonitis, catheter-related peritonitis and medical cure are defined. The new targets recommended for overall peritonitis rate should be no more than 0.40 episodes per year at risk and the percentage of patients free of peritonitis per unit time should be targeted at >80% per year. Revised recommendations regarding management of contamination of PD systems, antibiotic prophylaxis for invasive procedures and PD training and reassessment are included. New recommendations regarding management of modifiable peritonitis risk factors like domestic pets, hypokalaemia and histamine-2 receptor antagonists are highlighted. Updated recommendations regarding empirical antibiotic selection and dosage of antibiotics and also treatment of peritonitis due to specific microorganisms are made with new recommendation regarding adjunctive oral N-acetylcysteine therapy for mitigating aminoglycoside ototoxicity. Areas for future research in prevention and treatment of PD-related peritonitis are suggested.

Pharmacokinetics of antiretroviral and tuberculosis drugs in children with HIV/TB co-infection: a systematic review

INTRODUCTION

Management of concomitant use of ART and TB drugs is difficult because of the many drug-drug interactions (DDIs) between the medications. This systematic review provides an overview of the current state of knowledge about the pharmacokinetics (PK) of ART and TB treatment in children with HIV/TB co-infection, and identifies knowledge gaps.

METHODS

We searched Embase and PubMed, and systematically searched abstract books of relevant conferences, following PRISMA guidelines. Studies not reporting PK parameters, investigating medicines that are not available any longer or not including children with HIV/TB co-infection were excluded. All studies were assessed for quality.

RESULTS

In total, 47 studies met the inclusion criteria. No dose adjustments are necessary for efavirenz during concomitant first-line TB treatment use, but intersubject PK variability was high, especially in children <3 years of age. Super-boosted lopinavir/ritonavir (ratio 1:1) resulted in adequate lopinavir trough concentrations during rifampicin co-administration. Double-dosed raltegravir can be given with rifampicin in children >4 weeks old as well as twice-daily dolutegravir (instead of once daily) in children older than 6 years. Exposure to some TB drugs (ethambutol and rifampicin) was reduced in the setting of HIV infection, regardless of ART use. Only limited PK data of second-line TB drugs with ART in children who are HIV infected have been published.

CONCLUSIONS

Whereas integrase inhibitors seem favourable in older children, there are limited options for ART in young children (<3 years) receiving rifampicin-based TB therapy. The PK of TB drugs in HIV-infected children warrants further research.

Potentiating aminoglycoside antibiotics to reduce their toxic side effects

The lack of new antibiotics necessitates the improvement of existing ones, many of which are limited by toxic side effects. Aminoglycosides, antibiotics with excellent activity and low bacterial resistance, are hampered by dose-dependent toxic effects in patients (nephrotoxicity, ototoxicity). High antibiotic concentrations are often required to treat dormant, non-dividing bacteria, though previous studies show that aminoglycosides can be activated against such bacteria by specific metabolites. Here, we employed this mechanism to greatly boost the activity of low concentrations of aminoglycosides against prevalent Gram-negative pathogens (Escherichia coli, Salmonella enterica, and Klebsiella pneumoniae), suggesting that less toxic drug concentrations might be used effectively in patients. We go on to show that this effect improved treatment of biofilms, did not increase aminoglycoside resistance, and was due to the generation of proton-motive force (PMF). By single-cell microscopy, we demonstrate that stationary-phase cells, while non-dividing, actively maintain a growth-arrested state that is not reversed by metabolite addition. Surprisingly, within starved populations, we observed rare cells (3%) that divided without added nutrients. Additionally, we discovered that mannitol could directly protect human kidney cells from aminoglycoside cytotoxicity, independent of the metabolite's effect on bacteria. This work forwards a mechanism-based strategy to improve existing antibiotics by mitigating their toxic side effects.

Chemical Modifications Reduce Auditory Cell Damage Induced by Aminoglycoside Antibiotics

Although aminoglycoside antibiotics are effective against Gram-negative infections, these drugs often cause irreversible hearing damage. Binding to the decoding site of the eukaryotic ribosomes appears to result in ototoxicity, but there is evidence that other effects are involved. Here, we show how chemical modifications of apramycin and geneticin, considered among the least and most toxic aminoglycosides, respectively, reduce auditory cell damage. Using molecular dynamics simulations, we studied how modified aminoglycosides influence the essential freedom of movement of the decoding site of the ribosome, the region targeted by aminoglycosides. By determining the ratio of a protein translated in mitochondria to that of a protein translated in the cytoplasm, we showed that aminoglycosides can paradoxically elevate rather than reduce protein levels. We showed that certain aminoglycosides induce rapid plasma membrane permeabilization and that this nonribosomal effect can also be reduced through chemical modifications. The results presented suggest a new paradigm for the development of safer aminoglycoside antibiotics.

The Supramolecular Self-Assembly of Aminoglycoside Antibiotics and their Applications

Aminoglycosides, a class of antibiotics that includes gentamicin, kanamycin, neomycin, streptomycin, tobramycin and apramycin, are derived from various streptomyces species. Despite the significant increase in the antibacterial resistant pathogens, aminoglycosides remain an important class of antimicrobial drugs due to their unique chemical structure which offers a broad spectrum of activity. The modification of antibiotics and their subsequent use in supramolecular chemistry is rarely reported. Given the importance of aminoglycosides, here we give a brief overview on the modification of 4,5- and 4,6-disubstituted deoxystreptamine classes of aminoglycosides through supramolecular chemistry and their potential for real world applications. We also make the case that the work in this area is gaining momentum, and there are significant opportunities to meet the challenges of modern antibiotics through the modification of aminoglycosides by harnessing the advantages of supramolecular chemistry.

Overcoming Aminoglycoside Enzymatic Resistance: Design of Novel Antibiotics and Inhibitors

Resistance to aminoglycoside antibiotics has had a profound impact on clinical practice. Despite their powerful bactericidal activity, aminoglycosides were one of the first groups of antibiotics to meet the challenge of resistance. The most prevalent source of clinically relevant resistance against these therapeutics is conferred by the enzymatic modification of the antibiotic. Therefore, a deeper knowledge of the aminoglycoside-modifying enzymes and their interactions with the antibiotics and solvent is of paramount importance in order to facilitate the design of more effective and potent inhibitors and/or novel semisynthetic aminoglycosides that are not susceptible to modifying enzymes.

Key role of oxidative stress in animal models of aminoglycoside nephrotoxicity revealed by a systematic analysis of the antioxidant-to-nephroprotective correlation

The clinical utility of aminoglycoside antibiotics is partly limited by their nephrotoxicity. Co-administration of a variety of candidate nephroprotectants has been tested at the preclinical level. According to a recent meta-analytic study, antioxidants are the only family of compounds with enough preclinical documentation to draw solid conclusions on their class nephroprotective capacity in animal models. In this study a systematic analysis of the relation between the level of antioxidation and the level of nephroprotection was performed. A regression model is presented which crosses the y-axis (i.e. the axis representing the level of nephroprotection) very nearly the zero value, meaning that maximal prevention of the oxidative stress induced by aminoglycosides results in almost maximal nephroprotection. This indicates that oxidative stress plays a central role in the hierarchy of pathophysiological mechanisms underlying aminoglycoside nephrotoxicity. In addition, this model may potentially serve: i) as a standard to evaluate the role of the antioxidant effect of candidate nephroprotectants; ii) to reveal additional, antioxidant-independent effects among those compounds providing more nephroprotection than that expected from its antioxidant activity; and thus iii) to discriminate and focus most effective nephroprotectants on clinical usage.

A systematic meta-analysis on the efficacy of pre-clinically tested nephroprotectants at preventing aminoglycoside nephrotoxicity

Nephrotoxicity limits the use of aminoglycoside antibiotics. Kidney damage is produced mainly in the renal tubule due to an inflammatory and oxidative process. At preclinical level, many drugs and natural products have been tested as prospective protectors of aminoglycoside nephrotoxicity. The main objective of this work was to make a systematic literature review of preclinical studies about aminoglycoside nephrotoxicity protection and a statistical analysis based on the meta-analysis methodology. Studies published up to January 2016 were identified. After applying inclusion criteria, 54 studies were chosen. The size of the experimental groups, means and standard deviations of data on renal function (i.e. plasma creatinine and blood urea nitrogen [BUN] concentrations) were extracted and registered in a database. The studies were grouped according to the mechanism of nephroprotection and their route of administration. The Mean Difference (95% confidence interval) was calculated for each study and group. 40 of 54 products tested produced an amelioration of aminoglycoside nephrotoxicity based on creatinine results. Also a dose dependent protective effect was observed (both in creatinine and BUN). Products orally administered were more effective than via i.p. Products with attributed antioxidant activity were the most used and those which proved statistically significant nephroprotection as a class effect. Aminoglycoside tubular reuptake inhibitors, excretion inducers and calcium channel blockers also showed a promising and rather homogeneous class tendency towards nephroprotection, although more research is necessary to obtain solid and conclusive results, based on a larger number of studies.

Gentamicin for prevention of intraoperative mesh contamination: demonstration of high bactericide effect (in vitro) and low systemic bioavailability (in vivo)

INTRODUCTION

Mesh infection is a severe complication after incisional hernia repair and occurs in 1-3 % of all open mesh implantations. For this reason, topical antimicrobial agent applied directly to the mesh is often used procedure. So far, however, this procedure lacks a scientific basis.

MATERIALS AND METHODS

Two different meshes (Parietex™, Covidien; Ultrapro™, Ethicon Johnson & Johnson) were incubated with increasing amounts of three different Staphylococcus aureus strains (ATCC 25923; Mu50; ST239) with or without gentamicin and growth ability were determined in vitro. To further address the question of the systemic impact of topic gentamicin, serum levels were analyzed 6 and 24 h after implantation of gentamicin-impregnated multifilament meshes in 19 patients.

RESULTS

None of the gentamicin-impregnated meshes showed any bacterial growth in vitro. This effect was independent of the mesh type for all the tested S. aureus strains. In the clinical setting, serum gentamicin levels 6 h after implantation of the gentamicin-impregnated meshes were below the through-level (range 0.4-2.9 mg/l, mean 1.2 ± 0.7 mg/l). After 24 h the gentamicin serum levels in all patients had declined 90-65 % of the 6 h values.

CONCLUSION

Local application of gentamicin to meshes can completely prevent the growth of even gentamicin-resistant S. aureus strains in vitro. The systemic relevance of gentamicin in the clinical controls showed to be very low, without reaching therapeutic concentrations.

Guidelines for aminoglycoside use and applicability to geriatric patients

OBJECTIVES

The authors had for objective to evaluate the applicability of AFSSAPS guidelines for aminoglycoside use to geriatric patients.

METHODS

Theoretical doses and dosing regimens allowing reaching target concentrations in this population were calculated by applying a pharmacokinetic model to 30 geriatric patients treated by amikacin.

RESULTS

The dose allowing reaching a maximum concentration of 60 mg/L was 1.217 mg on average. The time required to reach a blood concentration lower than or equal to 2.5mg/L was 62.5±70.4 hours. Forty-six percent of patients had a trough concentration greater than 2.5 mg/L, 48 hours after administration. For these patients, the time between critical minimum inhibitory concentration (MIC) and toxicity threshold concentration was 21.9±14.9 hours.

CONCLUSION

Reaching a target concentration can be problematic in geriatric patients. It is frequently necessary to use dosing intervals greater than 48 hours. The effectiveness and safety of these regimens remain uncertain.

Novel nucleotide changes in mutational analysis of mitochondrial 12SrRNA gene in patients with nonsyndromic and aminoglycoside-induced hearing loss

Mitochondria have essential role in cellular energy metabolism and defects in their function lead to many metabolic diseases. Mitochondrial DNA (mtDNA) mutations have been associated with number diseases such as nonsyndromic and aminoglycoside-induced hearing loss. Mutational screening of entire 12SrRNA and tRNA (ser (UCN)) genes in 107 unrelated Iranian patients with amino glycoside-induced and nonsyndromic bilateral hearing loss by direct sequencing analysis method were performed. Twenty different homoplasmic sequence variants were identified; including fifteen common polymorphisms, two putatively pathogenic variants: m.921T>C and m.1005T>C, one 12SrRNA sequence variant m.739C>T and two nucleotides substitution; m.1245T>C and m.1545T>C. Deafness-associated mutation, m.1555A>G, was not found. In our patients we found the mutation 1005 was associated with R haplogroup. These finding show that m.1555A>G mutation is not important in our population. Nucleotide change, m.739C>T, previously reported with very low frequency. We suggested the variation of two nucleotides 1245 and 1545 that localized at conserved site of 12SrRNA may be new candidate for amino glycoside-induced and nonsyndromic hearing impairment associated mutations. However, aminoglycoside exposure is a risk factor for clinical phenotype appearance of these mutations.

Therapeutic drug monitoring of aminoglycosides in acute myeloid leukaemia patients

International guidelines limit the use of aminoglycosides in febrile neutropenia to severe situations. We retrospectively reviewed the use of aminoglycosides in adult acute myeloid leukaemia patients admitted in 2009. Our guidelines include precise indications (severe sepsis, shock, drug resistance), dosing regimens (once-daily 20 mg/kg/day amikacin, 5 mg/kg/day gentamicin), durations of treatment, drug monitoring timing, and target C(max) concentrations (40 mg/l amikacin, 20 mg/l gentamicin). Thirty-one patients received 46 aminoglycoside courses: 31 amikacin and 15 gentamicin. The mean prescribed dosage was 19 ± 2.8 mg/kg/day for amikacin and 4.7 ± 0.9 mg/kg/day for gentamicin. The mean duration of use was 2.9 days for both drugs. The mean C(max) for amikacin was 47 ± 13 mg/l and for gentamicin was 13.6 ± 7.5 mg/l. In compliant regimens, all amikacin patients and a third of gentamicin patients had adequate C(max). Among 23 isolated pathogens, 65.5% were susceptible to both drugs and 11.5% to amikacin only. This vindicates the 20 mg/kg/day amikacin dosage and suggests a need to increase the gentamicin dosage.

Aminoglycoside use in renal failure

Aminoglycosides are the mainstay in the treatment of serious gram negative infections including catheter-associated infections. They are not metabolized and are rapidly excreted as such by glomerular filtration resulting in a plasma t^½ of approximately two hours in those with normal renal function. The t^½, however, can extend to 30-60 hours in patients who are functionally anephric; therefore, dosage reduction or modification is necessary in renal failure patients. In patients on hemodialysis the clearance of aminoglycosides is significant and variable. The concept of conventional postdialysis dosing in patients on hemodialysis needs to be revised in favor of higher predialysis doses to maintain effective bactericidal activity. This article is a brief review of the use of aminoglycosides in renal failure patients.

A high G418-resistant neo(R) transgenic mouse and mouse embryonic fibroblast (MEF) feeder layers for cytotoxicity and gene targeting in vivo and in vitro

Aminoglycoside antibiotics have been in use since 1944 with the discovery of streptomycin. The aim of this study was to derive a new, highly resistant multicopy neo(R) transgenic mouse strain, named TgN3Ems, by random insertion of the plasmid, pPGKneobpA, and compare the level of drug resistance of wild-type and transgenic mice in vivo and corresponding primary mouse embryonic fibroblasts (MEFs) in vitro to a model neomycin analog, G418. The expression neoR in transgenic animals caused a 5-fold increase in the approximate lethal dose of G418, compared to wild type. No adverse pathological changes were found for the transgenic mice treated with G418, as they all died within minutes after injection. In contrast, the G418 treatment of wild-type mice resulted in a marked liver and kidney toxicity detected microscopically and via increases of serum biomarkers for liver and kidney damage. In addition, there was a mild bone marrow and lymphoid depletion. In in vitro studies, the transgenic MEFs survived 20-fold higher G418 levels, compared to the wild-type MEF cells. Therefore, TgN3Ems transgenic mice could be used as a source of G418-resistant feeder cells for gene targeting. Since the expression of drug-resistance genes in transgenic animals confers resistance to toxicity, the TgN3Ems mice might serve as a tool applicable in drug design.

Sub-acute toxicity study of a new aminoglycoside etimicin sulphate in swiss albino mice

Etimicin sulfate, an ethylization derivative of gentamicin, is a new soluble wide-spectrum synthetic aminoglycoside drug. It has wide antibacterial spectrum with high effect and less cross resistance as compared to other aminoglycosides. In order to further explore its safety and tolerance, we have conducted a subactute toxicity study on swiss albino mice. Results from the present study have elucidated that treatment of etimicin sulfate exerts no significant signs of toxicity at any dose level used in the study. Physiological as well as hematological parameters were unaltered throughout the study. Biochemical examination and histopathology of all organs confirmed no significant alteration at any dose levels. The result of this study has suggested there was no obvious toxicity observed with the treatment of etimicin sulphate. It was found to be a safe alternative for various severe infections.

Mitochondrial 12S rRNA mutations associated with aminoglycoside ototoxicity

The mitochondrial 12S rRNA is a hot spot for mutations associated with both aminoglycoside-induced and nonsyndromic hearing loss. Of those, the homoplasmic 1555A>G and 1494C>T mutations at the highly conserved decoding region of the 12S rRNA have been associated with hearing loss worldwide. In particular, these two mutations account for a significant number of cases of aminoglycoside ototoxicity. The 1555A>G or 1494C>T mutation is expected to form a novel 1494C-G1555 or 1494U-A1555 base-pair at the highly conserved A-site of 12S rRNA. These transitions make the human mitochondrial ribosomes more bacteria-like and alter binding sites for aminoglycosides. As a result, the exposure to aminoglycosides can induce or worsen hearing loss in individuals carrying one of these mutations. Biochemical characterization demonstrated an impairment of mitochondrial protein synthesis and subsequent defects in respiration in cells carrying the A1555G or 1494C>T mutation. Furthermore, a wide range of severity, age-at-onset and penetrance of hearing loss was observed within and among families carrying these mutations. Nuclear modifier genes, mitochondrial haplotypes and aminoglycosides should modulate the phenotypic manifestation of the 12S rRNA 1555A>G and 1494C>T mutations. Therefore, these data provide valuable information and technology: (1) to predict which individuals are at risk for ototoxicity; (2) to improve the safety of aminoglycoside antibiotic therapy; and (3) eventually to decrease the incidence of hearing loss.

Genetics of aminoglycoside-induced and prelingual non-syndromic mitochondrial hearing impairment: a review

Pathogenic mitochondrial DNA mutations are most often implicated in inherited and acquired hearing impairment. The current review mainly focuses on the 12S rRNA mitochondrial gene mutations associated with non-syndromic deafness without or after aminoglycosides exposure. Aminoglycoside-induced and nonsyndromic deafness has been shown to have a genetic susceptibility and the pathogenic mitochondrial 12S rRNA A1555G mutation was identified as the primary factor underlying the hearing loss in many familial as well as in genetically unrelated cases, particularly in Asian populations where aminoglycoside antibiotics are commonly used even for minor infections. Many families were shown to transmit the aminoglycoside ototoxicity through matrilineal inheritance and the A1555G mutation in the 12S rRNA gene was frequently identified. The aminoglycoside antibiotics are believed to target the mitochondrial ribosome in the cochlea resulting in abnormal RNA processing or decreased efficiency of translation thereby leading to irreversible auditory dysfunction. Such cases may have a genetic predisposition to aminoglycoside ototoxicity following autosomal dominant, autosomal recessive, X-linked, or mitochondrial pattern of inheritance.

Medication-related complications in the trauma patient

Trauma patients are twice as likely to have adverse reactions to medication as nontrauma patients. The need for medication in trauma patients is high. Surgery is often necessary, and immunosuppression and hypercoagulability may be present. Adverse drug events can be caused in part by altered pharmacokinetics, drug interactions, and polypharmacy. Medications may also have serious long-term adverse effects, which must be considered. It is not the purpose of this review article to discuss all adverse effects of all medications. This article will discuss the more common adverse effects of medications for trauma patients in the acute care setting, in the following categories: pain control, sedation, antibiotics, seizure prophylaxis in head trauma, atrial fibrillation, deep vein thrombosis and pulmonary embolism prophylaxis, hemodynamic support, adrenal insufficiency, factor VIIa.

Aminoglycosides and Kidney Function

The aminoglycosides are bactericide antibiotics with predominant effecting on the Gramm-negative bacteries, then staphylococci and mycobacteria with a small therapeutic range and with expressive ototoxic, nephrotoxic and with rare neurotoxic side effects. In this work the value of creatinine are investigated in serum of patients who are hospitalized in Internal department of the Health Center in Kosovska Mitrovica, before, in the course of and after therapy with the aminoglycosides antibiotics were given in different doses. The creatinine was determined by kinetic method (Jaffe). The significant increasing of creatinine values in serum was recorded with the groups of patients who have got gentamicine 2x120 mg i.m., gentamicine 2x120 mg in combination with furosemide, the gentamicine 2x120 mg with the patients with diabetes mellitus, gentamicine 2x120 mg in the course of 14 days until with the groups who have been getting gentamicine 1x120 mg, gentamicine 2x80 mg and amikacine 2x500 mg were not recorded the significant increased values of creatinine. The determination of creatinine for the sake of the following degree damage of kidney function in the course therapy of the aminoglycosides was very important.

Experimental Study of a New Vascular Graft Prebonded with Antibiotic: Healing, Toxicity, and Antibiotic Retention

Despite refinements in surgical techniques, routine antibioprophylaxis, and anesthesiology, vascular prosthetic infections remain a serious complication of reconstructive vascular surgery. The purpose of this study was to evaluate the healing, the toxicity, and the antibiotic delivery of a new vascular graft, preloaded with rifampin and tobramycin. Sixteen dogs underwent infrarenal aortic bypass. They were divided into three groups. In test group 1 (n = 8), dogs received grafts loaded with a standard concentration of antibiotics. In test group 2 (n = 4), dogs received grafts loaded with twice the standard concentration of antibiotics. A control group (n = 4) received a commercial gelatin-sealed graft. Grafts were harvested after different periods of time and submitted to histological evaluation and antibiotic dose determination. Liver and kidney toxicities were evaluated from dosages performed on serum samples taken at different time periods between graft implantation and harvesting. The healing of antibiotic-loaded grafts was similar to that of commercial grafts, without any signs of toxicity. These results suggest resistance to infection of these prebonded grafts in an animal model.

Extremely low penetrance of deafness associated with the mitochondrial 12S rRNA mutation in 16 Chinese families: Implication for early detection and prevention of deafness

Mutations in mitochondrial DNA (mtDNA) have been found to be associated with sensorineural hearing loss. We report here the clinical, genetic, and molecular characterization of 16 Chinese pedigrees (a total of 246 matrilineal relatives) with aminoglycoside-induced impairment. Clinical evaluation revealed the variable phenotype of hearing impairment including audiometric configuration in these subjects, although these subjects share some common features: being bilateral and sensorineural hearing impairment. Strikingly, these Chinese pedigrees exhibited extremely low penetrance of hearing loss, ranging from 4% to 18%, with an average of 8%. In particular, nineteen of 246 matrilineal relatives in these pedigrees had aminoglycoside-induced hearing loss. Mutational analysis of the mtDNA in these pedigrees showed the presence of homoplasmic 12S rRNA A1555G mutation, which has been associated with hearing impairment in many families worldwide. The extremely low penetrance of hearing loss in these Chinese families carrying the A1555G mutation strongly supports the notion that the A1555G mutation itself is not sufficient to produce the clinical phenotype. Children carrying the A1555G mutation are susceptible to the exposure of aminoglycosides, thereby inducing or worsening hearing impairment, as in the case of these Chinese families. Using those genetic and molecular approaches, we are able to diagnose whether children carry the ototoxic mtDNA mutation. Therefore, these data have been providing valuable information and technology to predict which individuals are at risk for ototoxicity, to improve the safety of aminoglycoside therapy, and eventually to decrease the incidence of deafness.

Antibiotic prophylaxis for endocarditis: time to reconsider

Some cardiac conditions require antibiotic prophylaxis for some types of dental treatment to reduce the risk of infective endocarditis (IE). All medical and dental practitioners are familiar with this practice but tend to use different regimens in apparently similar circumstances. Generally, the trend has been to prescribe antibiotics if in doubt. This review explores the evidence for antibiotic prophylaxis to prevent IE: does it work and is it safe? The changing nature of IE, the role of bacteraemia of oral origin and the safety of antibiotics are also reviewed. Most developed countries have national guidelines and their points of similarity and difference are discussed. One can only agree with the authority who describes antibiotic guidelines for endocarditis as being 'like the Dead Sea Scrolls, they are fragmentary, imperfect, capable of various interpretations and (mainly) missing!' Clinical case-controlled studies show that the more widely antibiotics are used, the greater the risk of adverse reactions exceeding the risk of IE. However, the consensus is that antibiotic prophylaxis is mandatory for a small number of high-risk cardiac and high-risk dental procedures. There are a large number of low-risk cardiac and dental procedures in which the risk of adverse reactions to the antibiotics exceeds the risk of IE, where prophylaxis should not be provided. There is an intermediate group of cardiac and dental procedures for which careful individual evaluation should be made to determine whether IE or antibiotics pose the greater risk. These categories are presented. All medical and dental practitioners need to reconsider their approach in light of these current findings.

Clinical evaluation and mitochondrial DNA sequence analysis in two Chinese families with aminoglycoside-induced and non-syndromic hearing loss

We report here the clinical, genetic, and molecular characterization of two Chinese pedigrees with aminoglycoside-induced and non-syndromic hearing impairment. Clinical evaluation revealed the variable phenotype of hearing impairment including audiometric configuration in these subjects. Penetrances of hearing loss in BJ105 and BJ106 pedigrees are 67% and 33%, respectively. In particular, three of 10 affected matrilineal relatives of BJ105 pedigree had aminoglycoside-induced hearing loss, while seven affected matrilineal relatives in BJ105 pedigree and six affected matrilineal relatives in BJ106 pedigree did not have a history of exposure to aminoglycosides. Sequence analysis of the complete mitochondrial genomes in these pedigrees showed the identical homoplasmic A1555G mutation and distinct sets of mtDNA variants belonging to haplogroups F3 and M7b. These variants showed no evolutionary conservation, implying that mitochondrial haplotype may not play a significant role in the phenotypic expression of the A1555G mutation in these Chinese pedigrees. However, aminoglycosides and nuclear backgrounds appear to be major modifier factors for the phenotypic manifestation of the A1555G mutation in these Chinese families.

Infection control in a hernia clinic: 24 year results of aseptic and antiseptic measure implementation in 4,620 "clean cases"

Post Mesh Herniorrhaphy Infection [PMHI] occurs between 3 to 4% of inguinal and 8 to 14% of ventral herniorrhaphies producing an unacceptably high morbidity. Before opening a Hernia Clinic, our infection rate was around 5% for "clean" inguinals and 8% for "clean" ventral herniorrhaphies. Starting in 1982 we implemented a stricter operative aseptic protocol plus the per-operative administration of 1 g of intravenous Cefazolin. In addition, wounds were irrigated with a solution containing 80 mgs of Gentamycin Sulphate dissolved in 250 ml of Normal Saline Solution. During a period of 25 years these measures were used in 4300 consecutive "clean "Inguinal and 320 "clean" Ventral herniorrhaphies. Since the implementation of the above-mentioned aseptic and antiseptic steps no further wound infections were encountered. In our hands, the combination of rigorous aseptic operating room routine plus intravenous and topical antibiotics have, up to now, effectively eliminated wound infections in "clean" herniorrhaphy cases.

Mutational analysis of the mitochondrial 12S rRNA gene in Chinese pediatric subjects with aminoglycoside-induced and non-syndromic hearing loss

Mutations in mitochondrial DNA (mtDNA) have been found to be associated with sensorineural hearing loss. We report here a systematic mutational screening of the mitochondrial 12S rRNA gene in 128 Chinese pediatric subjects with sporadic aminoglycoside-induced and non-syndromic hearing loss. We show that aminoglycoside ototoxicity accounts for 48% of cases of hearing loss in this Chinese pediatric population. Of the known deafness-associated mutations in this gene, the incidence of the A1555G mutation is approximately 13% and approximately 2.9% in this Chinese pediatric population with aminoglycoside-induced and non-syndromic hearing loss, respectively. Furthermore, mutations at position 961 in the 12S rRNA gene account for approximately 1.7% and 4.4% of cases of aminoglycoside-induced and non-syndromic hearing loss in this Chinese clinical population, respectively. The T1095C mutation has been identified in one maternally inherited family with aminoglycoside-induced and non-syndromic hearing loss. However, the C1494T mutation was not detected in this clinical population. In addition, three variants, A827G, T1005C and A1116G, in the 12S rRNA gene, localized at highly conserved sites, may play a role in the pathogenesis of aminoglycoside ototoxicity. These data strongly suggest that the mitochondrial 12S rRNA is a hot-spot for deafness-associated mutations in the Chinese population.

Genetic factors in aminoglycoside toxicity

Ototoxicity is the major irreversible toxicity of aminoglycosides, and it occurs both in a dose-dependent and idiosyncratic fashion. The idiosyncratic pathway is presumably due to genetic predispositions, and an inherited mutation in the mitochondrial 12S ribosomal RNA gene that predisposes carriers to aminoglycoside ototoxicity was identified in 1993. Up to a third of patients with aminoglycoside ototoxicity carry this mutation. Two other mutations in the same mitochondrial gene affect a small minority of additional patients. Thus, the prevention of aminoglycoside-induced ototoxicity through family history and molecular diagnosis is possible in many cases. It is the challenge of genomic medicine to translate this more than a decade-old knowledge into clinical practice.

The Importance of Bactericidal Drugs: Future Directions in Infectious Disease

BACKGROUND

Although a considerable amount of research has gone into the study of the role of bactericidal versus bacteriostatic antimicrobial agents in the treatment of different infectious diseases, there is no accepted standard of practice.

METHODS

A panel of infectious diseases specialists reviewed the available literature to try to define specific recommendations for clinical practice.

RESULTS

In infections of the central nervous system, the rapidity with which the organism is killed may be an important determinant, because of the serious damage that may occur during these clinical situations. The failure of bacteriostatic antibiotics to adequately treat endocarditis is well documented, both in human studies and in animal models.

CONCLUSION

The bulk of the evidence supports the concept that, in treating endocarditis and meningitis, it is important to use antibacterial agents with in vitro bactericidal activity. This conclusion is based on both human and animal data. The data to support bactericidal drugs' superiority to bacteriostatic drugs do not exist for most other clinical situations, and animal models do not support this concept in some situations. Clinicians should be aware that drugs that are bacteriostatic for one organism may in fact be bactericidal for another organism or another strain of the same organism.

Molecular pathogenetic mechanism of maternally inherited deafness

Mutations in the mitochondrial DNA (mtDNA) have been shown to be one important cause of deafness. In particular, mutations in the mtDNA have been associated with both syndromic and nonsyndromic forms of sensori-neural hearing loss. The deafness-linked mutations often occur in the mitochondrial 12S rRNA gene and in tRNA genes. Mutations in the 12S rRNA gene account for most of the cases of aminoglycoside ototoxicity. The other hot spot for mutations associated with hearing impairment is the tRNA(Ser(UCN)) gene, as five deafness-linked mutations have been identified in this gene. Nonsyndromic deafness-linked mtDNA mutations are often homoplasmic or at high levels of heteroplasmy, indicating a high threshold for pathogenicity. Phenotypic expression of these mtDNA mutations requires the contribution of other factors such as nuclear modifier gene(s), environmental factor(s), or mitochondrial haplotype(s).

A cost-effectiveness analysis of bacterial endocarditis prophylaxis for febrile children who have cardiac lesions and undergo urinary catheterization in the emergency department

OBJECTIVE

To prevent bacterial endocarditis (BE) in those at risk, the American Heart Association recommends antibiotics for patients who have a known urinary tract infection and are about to undergo urinary catheterization (UC). In young children who have cardiac lesions and undergo UC for fever without a source, the problem with prophylaxis only in the presence of infected urine is that the presence of urinary tract infection is unknown before testing. This study was conducted to determine the cost-effectiveness of BE prophylaxis before UC in febrile children aged 0-24 months with moderate-risk cardiac lesions.

METHODS

We evaluated the cost-effectiveness of BE prophylaxis compared with no prophylaxis from the societal perspective. Clinical outcomes were based on BE incidence and quality-adjusted life years (QALYs). Probabilities were derived from the medical literature. Costs were derived from national and local sources in US dollars for the reference year 2000, using a discount rate of 3%.

RESULTS

On the basis of the analysis, prophylaxis prevents 7 BE cases per 1 million children treated. When antibiotic-associated deaths were included, the no-prophylaxis strategy was more effective and less costly than the prophylaxis strategy. When antibiotic-associated deaths were excluded, amoxicillin cost 10 million dollars per QALY gained and 70 million dollars per case prevented. For vancomycin, it was 13 million dollars per QALY gained and 95 million dollars per case prevented. The results were robust to variations in the prophylactic efficacy of antibiotics, incidence of bacteremia after UC, incidence of BE after bacteremia, and costs associated with BE prophylaxis and treatment.

CONCLUSION

In the emergency department, BE prophylaxis before UC in febrile children who are aged 0 to 24 months and have moderate-risk cardiac lesions is not a cost-effective use of health care resources.

A study of once-daily amikacin with low peak target concentrations in intensive care unit patients: pharmacokinetics and associated outcomes

PURPOSE

The aim of this study was to assess the pharmacokinetics of individualized amikacin single-dosage regimens targeting low peak serum concentrations in a population of intensive care unit (ICU) patients, and to describe the outcomes associated with this dosing strategy.

MATERIALS AND METHODS

In this prospective, noncomparative, pharmacokinetic study, 36 ICU patients with adequate renal function were treated with amikacin (intravenous infusion), in combination with other antibiotics, for hospital-acquired infections. The initial doses of amikacin were calculated based on individual creatinine clearance values whereas subsequent doses were calculated by using the amikacin pharmacokinetic parameters estimated from the serum concentration-time data of each individual patient (samples were drawn postinfusion, 1 h, 3 h, 6 h, and 10 h after the onset of the infusion and just before the next dose on days 2, 4, and 7 of therapy).

RESULTS

Results showed moderate only interpatient and lack of intrapatient (except for the volume of distribution) variability in amikacin pharmacokinetic parameters. There were no significant differences between achieved and target peak levels. Clinical response was noted in 94% and bacteriologic response was noted in 86% of patients. Nephrotoxicity did not occur during or after treatment.

CONCLUSIONS

Amikacin dosage individualization with low peak target concentrations was successful for the 36 ICU patients. This dosing strategy was not associated with nephrotoxicity, but conclusions on clinical efficacy cannot be drawn from this limited study.

[Aminoglycosides]

Aminoglycosides remain as a efficacious class of antimicrobials, commonly used in the clinical practice. In spite of the existence of several mechanisms of resistance, they continue being active against most of the aerobic Gram-negative bacilli. Currently, although aminoglycosides may be used as monotherapy in the urinary tract infections, they are mainly used in combination with b-lactam antibiotics in severe infections caused by Gram-negative bacilli. The knowledge about the pharmacokinetic and pharmacodynamic parameters of aminoglycosides has suggested their use in an once-daily dosing regimen. This dosing has shown as efficacious as multiple-daily dosing regimen in several studies, which also have shown a trend toward a lower toxicity. Among the adverse events, nephrotoxicity and ototoxicity require a careful evaluation during its administration.

Recurrent fatal drug-induced toxic epidermal necrolysis (Lyell's syndrome) after putative beta-lactam cross-reactivity: Case report and scrutiny of antibiotic imputability

OBJECTIVE

A series of antibiotics may be responsible for toxic epidermal necrolysis. We report two successive episodes of toxic epidermal necrolysis in the same patient. Drug imputability criteria designate a cross-reactivity between two antibiotics of different chemical classes but sharing the beta-lactam ring in common.

DESIGN

Descriptive case report and review of the literature.

SETTING

Medical intensive care unit in a university medical center. PATIENT AND MAIN RESULTS: A 75-yr-old woman developed a first episode of toxic epidermal necrolysis (involving 40% of the body surface) after intake of cefotaxime, a third-generation cephalosporin. Perfusions of high-dose immunoglobulins rapidly improved the lesions, followed by partial reepithelialization in 5 days. Sepsis required the administration of meropenem, which is a carbapenem antibiotic. The epidermal destruction immediately recurred, with extension to previously uninvolved skin areas and fatal consequences.

CONCLUSIONS

The beta-lactam ring present in cephalosporins and carbapenems represents the putative chemical structure responsible for the presently reported cross-reactivity to two antibiotics of different classes. Drugs having any chemical similarity to the initial culprit compound should be strictly avoided when possible in the management of toxic epidermal necrolysis.

Individualising aminoglycoside dosage regimens after therapeutic drug monitoring: simple or complex pharmacokinetic methods?

Measurements of aminoglycoside concentration in serum are used to individualise dosage regimens (dose per administration and/or administration interval) with the goal of attaining the desired therapeutic range as quickly as possible. Therapeutic range is defined in terms of peak concentration (to monitor effectiveness) and trough concentration (to avoid toxicity). This article focuses on methods to individualise aminoglycoside dosage regimens in the context of extended dosage intervals. Simple pharmacokinetic methods involve linear dosage adjustment based on peak or trough concentrations or area under the concentration-time curve, or nomograms. The once daily aminoglycoside nomogram determines the dosage interval for aminoglycosides given as a fixed dose per administration, based on a single concentration measurement drawn 6 to 14 hours after the start of the first infusion. This is a preferred method because of its simplicity, strong pharmacodynamic rationale and prospective validation in a large population. However, it does not work when the fixed dose assumed is not relevant, for example for patients with burns, cystic fibrosis, ascites or pregnancy. Furthermore, it has not been validated in children. In these cases, a more sophisticated method is required. Complex pharmacokinetic methods require dedicated software. Non-Bayesian least-squares methods allow the optimisation of both the dose and the dosage interval, but require aminoglycoside concentrations from two or more samples taken in the post-distributive phase during a single dosage interval. With Bayesian least-squares methods, only one concentration measurement is required, although any number of samples can be taken into account. In the Bayesian maximum a posteriori (MAP) method, the parameter estimates are taken as the values corresponding to the maximum of the posterior density. In 'full' Bayesian approaches (also called stochastic control), all the information about the parameters revealed by the posterior distribution is taken into account, and the optimal regimen is found by minimising the expected value of the weighted sum of squared deviations between predicted and target concentrations. If the population model is reasonably well known, Bayesian methods (MAP or stochastic control) should be used because of their good predictive performance. Although only one concentration measurement is required, better precision is afforded by a two-sample strategy, preferably drawn 1 and 6 hours after the start of the first infusion. If the population model is not known, then the non-Bayesian least-squares method is the method of choice, because of its robustness and lack of requirement for prior information about the distribution of parameters in the population.

Renal transport of antibiotics and nephrotoxicity: a review

The renal excretion of a drug can essentially be divided schematically into three functional processes: glomerular filtration, tubular reabsorption and tubular secretion. When assessing nephrotoxicity, the tubular secretion system, which allows transport of the drug from the blood to the urine via the tubular cells, is particularly important. Historically, two distinct tubular secretion mechanisms have been described for drugs: one via organic cations and the other via organic anions. More recently, a third tubular secretion mechanism has been identified, mediated by P-glycoprotein. In the present review, a number of examples will be given relating to antibiotic-induced kidney damage determined via the tubular reabsorption mechanism (aminoglycosides, amphotericin B) and via the tubular secretion mechanism (cephalosporins, vancomycin), respectively. Drug transport within the tubular cells is the first fundamental stage in the onset of the nephrotoxic process. Knowledge of these concepts is important for the prevention of iatrogenic kidney damage, particularly in patients with underlying disease receiving concomitant treatment with several potentially nephrotoxic molecules.

Should aminoglycoside antibiotics be abandoned?

BACKGROUND

Aminoglycosides can cause nephrotoxicity and ototoxicity. Alternatives are available.

METHODS

Surgical service antibiotic use, aminoglycoside toxicity, and perioperative culture/sensitivity results from July 1998 to June 1999 were reviewed.

RESULTS

Of 289 positive cultures in 243 patients, 92 cultures (32%) grew 151 Gram-negative rods (GNRs). Aminoglycosides were used in 26 patients and 4 of 26 (15%) suffered nephrotoxicity. Of the 112 GNRs tested against ceftazidime, 111 (99%) were sensitive to it which was significantly better than amikacin (56 of 61, 92%, P = 0.038), gentamicin (116 of 134, 87%, P <0.001), and tobramycin (67 of 81, 83%, P <0.001). The proportion sensitive to cefuroxime (26 of 30, 87%) was equivalent to the proportions sensitive to gentamicin (87%, P = NS) and tobramycin (83%, P = NS). Of the 35 GNRs that were resistant to gentamicin and/or tobramycin, 15 (43%) were Pseudomonas aeruginosa.

CONCLUSION

Aminoglycosides produce a significant rate of nephrotoxicity. There are antibiotics with equal or better sensitivity profiles than aminoglycosides against GNRs and Pseudomonas. Aminoglycoside use is rarely, if ever, indicated.

Gentamicin for the practicing urologist: review of efficacy, single daily dosing and "switch" therapy

PURPOSE

We review the literature on gentamicin, including single daily dosing and "switch" therapy.

MATERIALS AND METHODS

We used MEDLINE to search the literature from 1966 to June 1997, and then manually searched bibliographies to identify studies that our initial search might have missed.

RESULTS

Gentamicin has attractive characteristics, including wide spectrum, infrequent resistance, economy and familiarity. Although limited by well known toxicities, gentamicin remains a drug of choice for serious Gram-negative infections. Dosing strategies, such as single daily dosing and switch therapy, have renewed enthusiasm for this time-honored drug.

CONCLUSIONS

Gentamicin remains a valuable drug in urology. Once daily dosing and switch therapy offer the potential to increase effectiveness and convenience while decreasing toxicity and costs.