Sensorineural Hearing Loss in Multidrug-Resistant Tuberculosis Patients in Kinshasa (Democratic Republic of Congo): Prospective Cohort Study of Therapeutic Regimen with Aminoglycoside versus Bedaquiline

Context: Multidrug-resistant tuberculosis (MDR-TB) remains a major public health problem in developing countries such as the Democratic Republic of Congo (DRC), which continues to face the emergence of MDR-TB cases. Because of the ototoxic effects of AGs, the World Health Organization (WHO) has recommended the introduction of the bedaquiline regimen. However, very few data are available regarding the susceptibility of bedaquiline to induce hearing loss, hence the present study set out to compare the AG-based regimen and the bedaquiline-based regimen in the occurrence of hearing loss in MDR-TB patients. Methods: This is a prospective multicenter cohort study that included 335 MDR-TB patients, performed in Kinshasa (DRC) during the period from January 2020 to January 2021. Sociodemographic, clinical, biological and audiometric data were analyzed using Stata 17. Repeated-measures analysis of variance was used to compare changes in the degree of hearing loss over time between the two groups of patients on AG and bedaquiline regimens. The double-difference method was estimated using regression with fixed-effects. A p value < 0.05 was considered the threshold for statistical significance. Results: The degree of hearing loss was similar between the two groups at the first month [AGs (28 dB) vs BDQ (30 dB);p = 0.298]. At six months, the mean degree of hearing loss was significantly greater in the aminoglycoside regimen group [AGs (60.5 dB) vs BDQ (44 dB);p < 0.001]. The double difference was significant, with a greater increase in hearing loss in the AGs group (diff-in-diff 18.3;p < 0.001). After adjustment for age and serum albumin, the group receiving the AG-based regimen had a 2-point greater worsening than those with bedaquiline at the sixth month (diff-in-diff 19.8;p Conclusion: Hearing loss is frequent with both treatment regimens, but more marked with the Aminoglycoside-based regimen. Thus, bedaquiline should also benefit for audiometric monitoring in future MDR-TB patients.

Detection of aac(3)IIc, aac(6)Ib, armA Genes Coding for Escherichia coli Resistance to Aminoglycosides in Burkina Faso

Background and Prupose: Antibiotic resistance is a major global health concern. In addition to the existing data on the prevalence of bacterial resistance to antibiotics, there are patchy data on bacterial resistance to aminoglycosides in Burkina Faso. In this study, we determined the prevalence of aminoglycoside resistance genes in E. coli, including aac(3)-IIc, aac(6)-Ib and armA in Ouagadougou, and determined which antibiotics in this class are most affected by resistance. Material and Methods: This study was conducted on 216 E. coli strains collected from the biomedical analysis laboratories of Saint Camille and Schiphra hospitals. E. coli strains were isolated from pus and urine samples collected between September 2018 and January 2019. Antibiotic susceptibility testing was performed using aminoglycosides, β-lactams, fluoroquinolones, and sulfonamides. Aminoglycoside resistance genes were detected in strains with at least one aminoglycoside resistance gene using conventional/multiplex PCR. Results: Aminoglycoside resistance was observed in 46.8% (101/216) of strains. The resistance rates were respectively 45.37% for Tobramycin, 32.40% for Gentamicin, 14.81% for Kanamycin, 2.31% for Netilmicin, 1.84% for Neomycin, and 0.46% for Amikacin. PCR showed that 86 strains (85.15%) possessed the aac(3)-IIc gene, 71 strains or 70.30%) possessed the aac(6’)-Ib gene, and nine strains (8.91%) possessed the armA gene. Conclusion: Aminoglycoside resistance in pathogenic E. coli strains is mainly due to the presence of the aac(3’)-IIc and aac(6’)-Ib genes. The presence of armA was first reported in Burkina Faso. Netilmicin, Neomycin and Amikacin are good therapeutic options for treating urinary tract and pus-forming infections.

Mitochondrial DNA mutations associated with aminoglycoside induced ototoxicity

Aminoglycosides(Am An) are widely used for their great efficiency against gram-negative bacterial infections. However, they can also induce ototoxic hearing loss, which has affected millions of people around the world. As previously reported, individuals bearing mitochondrial DNA mutations in the 12 S rRNA gene, such as m.1555A>G and m.1494C>T, are more prone to Am An-induced ototoxicity. These mutations cause human mitochondrial ribosomes to more closely resemble bacterial ribosomes and enable a stronger aminoglycoside interaction. Consequently,exposure to Am An can induce or worsen hearing loss in these individuals. Furthermore, a wide range of severity and penetrance of hearing loss was observed among families carrying these mutations. Studies have revealed that these mitochondria mutations are the primary molecular mechanism of genetic susceptibility to Am An ototoxicity, though nuclear modifier genes and mitochondrial haplotypes are known to modulate the phenotypic manifestation.

Pharmacodynamics of aminoglycosides and tetracycline derivatives against Japanese encephalitis virus

Objective:To explore the antiviral activity of antibiotic compounds,mainly aminoglycosides and tetracyclines against Japanese encephalitis virus(JEV) induced infection in vitro.Methods:Antiviral activity were evaluated against JEV using cytopathic effect inhibition assay,virus yield reduction assay,caspase 3 level,extracellular viral detection by antigen capture ELISA and viral RNA levels.Roults:JEV induced cytopathic effect along with reduction of viral progeny plaque formation indicated antiviral potential of the compounds suggesting that antibiotics had broad spectrum activity.Doxycycline and kanamycin administration in dose dependent manner declined viral RNA replication.Conclusions:The present study shows kanamycin and doxycyclinc can affect virion structure and alter replication causing inhibition of JEV induced pathogenesis in vitro.

Prevalence and trends of aminoglycoside resistance in Shigella worldwide, 1999-2010

Shigellosis causes diarrheal disease in humans in both developed and developing countries, and multi-drug resistance in Shigella is an emerging problem. Understanding changing resistance patterns is important in determining appropriate antibiotic treatments. This meta-analysis systematically evaluated aminoglycoside resistance in Shigella. A systematic review was constructed based on MEDLINE and EMBASE databases. Randomeffect models or fixed-effect models were used based on P value considering the possibility of heterogeneity between studies for meta-analysis. Data manipulation and statistical analyses were performed using software STATA 11.0. By means of meta-analysis, we found a lower resistance to three kinds of aminoglycosides in the Europe-America areas during the 12 year study period than that of the Asia-Africa areas. Kanamycin resistance was observed to be the most common drug resistance among Shigella isolates with a prevalence of 6.88% （95%CI： 6.36%-7.43%）. Comparison of data from Europe-America and Asia-Africa areas revealed that Shigella flexneri resistance was greater than the resistance calculated for Shigella sonnei. Importantly, Shigella sonnei has played a significant role in aminoglycoside-resistance in recent years. Similarly, data showed that resistance to these drugs in children was higher than the corresponding data of adults. In conclusion, aminoglycoside-resistant Shigella is not an unusual phenomenon worldwide. Distribution in Shigella resistance differs sharply based on geographic areas, periods of time and subtypes. The results from the present study highlight the need for con- tinuous surveillance of resistance and control of antibiotic usage.

Mitochondrial DNA Mutations Associated with Aminoglycoside Ototoxicity

The mitochondrial 12S rRNA has been shown to be the hot spot for mutations associated with both aminoglycoside-induced and non-syndromic hearing loss. Of all the mutations, the homoplasmic A1555G and C1494T mutations at a highly conserved decoding region in the 12S rRNA have been associated with aminoglycoside-induced and non-syndromic hearing loss in many families worldwide. The A1555G or C1494T mutation is expected to form novel 1494C-G1555 or 1494U-A1555 base-pair at the highly conserved A-site of 12S rRNA. These transitions make the secondary structure of this RNA more closely resemble the corresponding region of bacterial 16S rRNA. Thus, the new U-A or G-C pair in 12S rRNA created by the C1494T or A1555G transition facilitates the binding of aminoglycosides, thereby accounting for the fact that the exposure to aminoglycosides can induce or worsen hearing loss in individuals carrying these mutations. Furthermore, the growth defect and impairment of mitochondrial translation were observed in cell lines carrying the A1555G or C1494T mutation in the presence of high concentration of aminoglycosides. In addition, nuclear modifier genes and mitochondrial haplotypes modulate the phenotypic manifestation of the A1555G and C1494T mutations. These observations provide the direct genetic and biochemical evidences that the A1555G or C1494T mutation is a pathogenic mtDNA mutation associated with aminoglycoside-induced and nonsyndromic hearing loss. 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 antibiotic therapy, and eventually to decrease the incidence of deafness.

LOWER DOSE OF AMINOGLYCOSIDE OTOTOXIC EXPOSURE CAUSES PRESYNAPTIC ALTERATIONS ASSOICATED WITH HEARING LOSS

Objective To study presynaptic alternations of cochlear ribbons arising from aminoglycoside ototoxic stimuli in C57BL/6J mice. Methods Animals were injected with low dose gentamicin (100 mg/kg/day) for 14 days, From the 14th to 28th days, the mice were maintained free of gentamicin treatment. Immunohisto-chemistry labeling was employed to trace RIBEYE, a major presynaptic componment of ribbon synapses. RIBEYE/CtBP2 expression levels were assessed and compared with hearing threshold shifts. Auditory func-tion was assessed by auditory brainstem responses. The stereocilia of outer hair cells (OHCs) and IHCs was examined by scanning electron microscopy (SEM). Results Hearing thresholds were elevated with peak hearing loss observed on the 7th day after gentamicin exposure, followed by improvement after the 7th day. RIBEYE/CtBP2 expression directly correlated with observed hearing threshold shifts. Strikingly, we did not see any obvious changes in stereocilia in both OHCs and IHCs until the 28th day. Mild changes in stereocil-ia were only observed in OHCs on the 28th day. Conclusions These findings indicate that presynapse co-chlear ribbons, rather than stereocilia, may be sensitive to aminoglycoside ototoxic exposure in mice cochle-ae. A pattern of RIBEYE/CtBP2 expression changes seems to parallel hearing threshold shifts and suggests presynaptic response properties to lower dosage of aminoglycoside ototoxic stimuli.

Investigation on the Mechanism of Exacerbation of Myasthenia Gravis by Aminoglycoside Antibiotics in Mouse Model

To investigate the underlying mechanism of the exacerbation of myasthenia gravis by aminoglycoside antibiotics. C57/BL6 mice were immunized with acetylcholine receptor (AChR), extracted from electric organ of Narcine timilei according to Xu Haopeng's methods, in complete Fruend's adjuvant (CFA) to establish experimental autoimmune myasthenia gravis (EAMG). EAMG mice were divided randomly into 5 groups: MG group, NS group and three antibiotics groups. The clinical symptom scores of mice were evaluated on d7 after the last immunization and d14 of antibiotics treatment. Repetitive nerve stimulation (RNS) was performed and the levels of anti-AChR antibody (AChR-Ab) were tested at the same time. The mean clinical symptom grades of gentamycin group (1.312, 2.067), amikacin group (1.111, 1.889) and etimicin group (1.263, 1.632) were significantly higher than those of MG group (1.000, 1.200) (P<0.05). The positive rates of RNS of three antibiotics groups were 69.23 %, 58.82 % and 63.16 % respectively, which were significantly higher than those of MG group and NS group (40.00 %, 40.00 %, P<0.05). The AChR-Ab level in serum and the expression of AChR on neuromuscular junction (NMJ) of mice in three antibiotics groups were also higher than those of MG group. Our results indicated that aminoglycoside antibiotics could aggravate the symptom of myasthenia gravis. The exacerbation of myasthenia gravis by these antibiotics probably involves competitively restraining the release of acetylcholine from presynaptic membrane, impairing the depolarization of postsynaptic membrane, depressing the irritability of myocyte membrane around the end-plate membrane and consequently leading to the blockade of neuromuscular junction.

Pharmacokinetics of Aminoglycosides

The Pharmacokinetics informations of aminoglycosides, their monograph and clinical Pharmacokinetics parameters are reported in this review. The Aminoglycosides are highly polarity and in reserve for serious infections caused by aerobic gram negative bacteria and some gram positive bacteria but their toxicity are major limitations in clinical use.

Optimization and Comparisons for Separation, Detection and Quantification of 12 Aminoglycosides Using 2 Chromatographic Conditions by LC-MS/MS

Aminoglycosides are a family of antibiotics with important applications in veterinary medicine. Their ionic character, the similarity structures and the high polarity due to the presence of two or more amino and hydroxyl groups cause a difficulty in separation and make these compounds poorly retained on the reversed phase column. An analytical method for the separation and detection of 12 aminoglycosides has been optimized using two kinds of chromatographic conditions (HILIC, Ion pairing). In Hydrophilic Interaction, ZIC_HILIC column was used, by which the following parameters for the mobile phase were evaluated: concentration of ammonium acetate buffer, percentage of formic acid and effect of acid type. The maximum and adequate concentration of ammonium acetate for the majority of analytes was set to 30 mM. The percentage 0.1% of formic acid increases the response for the majority of analytes. On the other side, the use of 0.1% of trifluoroacetic acid improves the response when compared with the response obtained with 0.1% of formic acid except for Spectinomycin Dihydrostreptomycin and Streptomycin. For ion pairing chromatography, the concentration of pentafluoropropionic acid was tested and the greatest value appeared to be 9.2 mM. Therefore, the comparison between the two separation methods shows that the response area of the majority of analytes tested increases when using the ion pair mode. Also, the high value of S/N and the lower detection limit (5 - 15 μg m·L﹣1 for most aminoglycosides studied make the ion pairing method more preferable than HILIC interaction.

The Central Cattle Breeding and Dairy Farm, Bangladesh waste contributes in emergence and spread of aminoglycoside-resistant bacteria

Aminoglycosides are one of the categories of antibiotics most frequently used in treating several cattle diseases at the Central Cattle Breeding and Dairy Farm (CCBDF), Savar,Dhaka,Bangladesh. Untreated veterinary clinical healthcare waste (VCHW) of diseased cattle at CCBDF which directly disposed to surrounding may contribute to the antibiotic resistant bacteria pollution (ARB) pollution. The investigation analyses the role of VCHW of CCBDF in spreading ARB. Here we studied:1) veterinary clinical data and antibiotics treatment history;2) total and resistant bacteria counts in fecal samples of healthy and diseased cattles as well as VCHW of CCBDF;and 3) finally, data analysis to estimate the burden of VCHW of CCBDF in the pollution of environment with aminoglycoside antibiotics resistant bacteria. The results conclusively demonstrate the spread of 3 different aminoglycoside antibiotics, namely genta- mycin, kanamycin and streptomycin resistant bacte- ria in the surrounding environment alarmingly with high significant value (p < 0.01 - 0.05). This study re- veals the risks to the cattle as well as public health posed by the random VCHW disposal at the CCBDF, Bangladesh.

Safety in Surgery:Evaluation of Safety and Efficiency in Use of Aminoglycosides in Acute Appendicitis

Background: Aminoglycosides are used as empirical antibiotic treatment of intraabdominal infections which are caused by Gram negative bacteria and for which the treatment of choice is surgery. Aminoglycosides maintain good efficacy against these bacteria and reduce the need for prescribing fluoroquinolone, cephalosporin and carbapenem antibiotics which contribute to the development of resistant bacterial strains. In recent years, several clinical trials and international guidelines have advised against the use of aminoglycosides owing largely to doubts about their effectiveness and to the concern for their known nephrotoxicity and ototoxicity. Aim: In our study, we aimed to prove whether aminoglycosides are appropriate agents in the treatment of acute appendicitis. Methods: Retrospectively, patients with acute appendicitis we included in the trial. Demographic characteristics, comorbidities, clinical signs and symptoms, the type of antibiotic and surgical treatment were analyzed. The effect of independent variables on the occurrence of complications was calculated using Student’s T-test and Fisher’s precise test. The effect of aminoglycosides on the loss of kidney function was determined by means of a linear regression method. Results: 300 patients proved acute appendicitis were included in the study. Univariate statistical analysis showed that the risk factors for postoperative complications in treating acute appendicitis were: age over 76 years (p Conclusion: Aminoglycoside antibiotics are a safe and effective treatment of acute appendicitis;our not published data are positive of AGs use in acute cholecystitis and left colon diverticulitis which requires surgery. If used for a limited time period, they do not increase the risk for kidney injury and remain a stable low level of all over complications.

Glycodiversification of gentamicins through in vivo glycosyltransferase swapping enabled the creation of novel hybrid aminoglycoside antibiotics with potent activity and low ototoxicity

Aminoglycosides(AGs)are a class of antibiotics with a broad spectrum of activity.However,their use is limited by safety concerns associated with nephrotoxicity and ototoxicity,as well as drug resistance.To address these issues,semi-synthetic approaches for modifying natural AGs have generated new generations of AGs,however,with limited types of modification due to significant challenges in synthesis.This study explores a novel approach that harness the bacterial biosynthetic machinery of gentamicins and kanamycins to create hybrid AGs.This was achieved by glycodiversification of gentamicins via swapping the glycosyltransferase(GT)in their producer with the GT from kanamycins biosynthetic pathway and resulted in the creation of a series of novel AGs,therefore referred to as genkamicins(GKs).The manipulation of the hybrid biosynthetic pathway enabled the targeted accumulation of different GK species and the isolation and characterization of six GK components.These compounds display retained antimicrobial activity against a panel of World Health Organization(WHO)critical priority pathogens,and GK-C2a,in particular,demonstrates low ototoxicity compared to clinical drugs in zebrafish embryos.This study provides a new strategy for diversifying the structure of AGs and a potential avenue for developing less toxic AG drugs to combat infectious diseases.

The prevalence and distribution of aminoglycoside resistance genes

Choosing the appropriate antibiotics to treat bacterial infections has grown more challenging as a result of the emergence of antibiotic-resistant bacteria.Aminoglycosides,as broad-spectrum antibiotics,are increasingly being used clinically;however,for most effective employment of aminoglycosides,a comprehensive understanding of aminoglycoside resistance genes’prevalence and dissemination is required.Therefore,to better understand the global resistance status of aminoglycoside antibiotics and the prevalence of antibiotic-resistance genes(ARGs)in various bacterial species,this systematic review gathered relevant data from multiple studies.Two primary resistance mechanisms-aminoglycoside enzymatic modification and 16S rRNA methylation-were assessed,and the prevalence of the corresponding ARGs was described.The coexistence of aminoglycoside ARGs with other ARGs was also demonstrated,as was the relationship between aminoglycoside ARGs and resistant phenotypes.The lack of effective therapeutic agents to combat resistant pathogens presents a real threat to public health.The combination of aminoglycosides with other antibiotics may provide a novel treatment strategy.

Molecular Docking Studies on Streptomycin Antileishmanial Activity

Resistance to pentavalent antimonial drugs and the lack of vaccines make it urgent to find novel therapeutic options to treat Leishmaniasis, a tropical disease caused by the Leishmania protozoan parasite. The study reported here is to investigate if Streptomycin, an aminoglycoside, and Amphotericin B, the second-line treatment drug, exhibit antileishmanial activity through a similar mechanism. By using MOE (Molecular Operating Environment), we performed molecular docking studies on these drugs binding to a range of targets including ribosome targets in Leishmania and H. sapiens. Our study shows that the two drugs do not bind to the same pockets in Leishmania targets but to the same pockets in the human ribosome, with some differences in interactions. Moreover, our 2D maps indicated that Amphotericin B binds to the A-site in the human cytoplasmic ribosome, whereas streptomycin does not.

Synthesis of a series of guanidine substituted derivatives of aminoglycosides

A novel method to prepare guanidine substituted aminoglycoside derivatives was developed.Free guanidine reacted with Cbz-protected aminoglycosides to produce guanidinylcarbonyl substituted derivatives.A methoxycarbonyl-protected intermediate was isolated,and the mechanism of guanidinylcarbonyl modification was proposed.With this method,six per- or part-guanidylcarbonyl substituted aminoglycosides were successfully obtained in good yields.Their in vitro antibacterial activities were essayed.

Convenient synthesis of urea-linked hydroxyl-alkylamine derivatives of aminoglycosides

A series of urea-linked hydroxyl-alkylamine derivatives of aminoglycosides have been obtained by modification of neamine （1）, kanamycin （2） and ribostamycin （3） at 1, 6＇ and 3 N-sites, respectively, through selective cyclization and nucleophilic ring-opening of cyclic carbamates. All the products showed no noticeable activity in the antibiotic test in vitro. The result suggests that the urea-linked hydroxyl-alkylamine derivatives of aminoglycosides may not be suitable structures for the enhancement of antibiotic activity.

Genetic basis of high level aminoglycoside resistance in Acinetobacter baumannii from Beijing,China

The objective of this study was to investigate the genetic basis of high level aminoglycoside resistance in Acinetobacter baumannii clinical isolates from Beijing,China.173 A.baumannii clinical isolates from hospitals in Beijing from 2006 to 2009 were first subjected to high level aminoglycoside resistance(HLAR,MIC to gentamicin and amikacin>512 mg/mL)phenotype selection by broth microdilution method.The strains were then subjected to genetic basis analysis by PCR detection of the aminoglycoside modifying enzyme genes(aac(3)-Ⅰ,aac(3)-Ⅱc,aac(60)-Ⅰb,aac(60)-Ⅱ,aph(4)-Ⅰa,aph(30)-Ⅰ,aph(30)-Ⅱb,aph(30)-Ⅲa,aph(30)-Ⅵa,aph(2″)-Ⅰb,aph(2″)-Ⅰc,aph(2″)-Ⅰd,ant(2″)-Ⅰa,ant(3″)-Ⅰand ant(40)-Ⅰa)and the 16S rRNA methylase genes(armA,rmtB and rmtC).Correlation analysis between the presence of aminoglycoside resistance gene and HLAR phenotype were performed by SPSS.Totally 102(58.96%)HLAR isolates were selected.The HLAR rates for year 2006,2007,2008 and 2009 were 52.63%,65.22%,51.11%and 70.83%,respectively.Five modifying enzyme genes(aac(3)-Ⅰ,detection rate of 65.69%;aac(60)-Ⅰb,detection rate of 45.10%;aph(30)-Ⅰ,detection rate of 47.06%;aph(30)-Ⅱb,detection rate of 0.98%;ant(3″)-Ⅰ,detection rate of 95.10%)and one methylase gene(armA,detection rate of 98.04%)were detected in the 102 A.baumannii with aac(3)-Ⅰ+aac(60)-Ⅰ+þant(3″)-Ⅰ+armA(detection rate of 25.49%),aac(3)-Ⅰ+aph(30)-Ⅰ+ant(3″)-Ⅰ+armA(detection rate of 21.57%)and ant(3″)-Ⅰ+armA(detection rate of 12.75%)being the most prevalent gene profiles.The values of chi-square tests showed correlation of armA,ant(3″)-Ⅰ,aac(3)-Ⅰ,aph(30)-Ⅰand aac(60)-Ⅰb with HLAR.armA had significant correlation(contingency coefficient 0.685)and good contingency with HLAR(kappa 0.940).The high rates of HLAR may cause a serious problem for combination therapy of aminoglycoside with β-lactams against A.baumannii infections.As armA was reported to be able to cause high level aminoglycoside resistance to most of the clinical important aminoglycosides(gentamicin,amikacin,tobramycin,etc),the function of aminoglycoside modifying enzyme gene(s)in A.baumannii carrying armA deserves further investigation.

Felodipine enhances aminoglycosides efficacy against implant infections caused by methicillin-resistant Staphylococcus aureus,persisters and biofilms

Methicillin-resistant Staphylococcus aureus(MRSA),biofilms,and persisters are three major factors leading to recurrent and recalcitrant implant infections.Although antibiotics are still the primary treatment for chronic implant infections in clinical,only few drugs are effective in clearing persisters and formed biofilms.Here,felodipine,a dihydropyridine calcium channel blocker,was reported for the first time to have antibacterial effects against MRSA,biofilm,and persisters.Even after continuous exposure to sub-lethal concentrations of felodipine,bacteria are less likely to develop resistance.Besides,low doses of felodipine enhances the antibacterial activity of gentamicin by inhibiting the expression of protein associated with aminoglycoside resistance(aacA-aphD).Next,biofilm eradication test and persisters killing assay suggested felodipine has an excellent bactericidal effect against formed biofilms and persisters.Furthermore,the result of protein profiling,and quantitative metabonomics analysis indicated felodipine reduce MRSA virulence(agrABC),biofilm formation and TCA cycle.Then,molecular docking showed felodipine inhibit the growth of persisters by binding to the H pocket of ClpP protease,which could lead to substantial protein degradation.Furthermore,murine infection models suggested felodipine in combination with gentamicin alleviate bacterial burden and inflammatory response.In conclusion,low dose of felodipine might be a promising agent for biomaterial delivery to enhance aminoglycosides efficacy against implant infections caused by MRSA,biofilm,and persisters.

Characteristics of two transferable aminoglycoside resistance plasmids in Escherichia coli isolated from pig and chicken manure

Plasmid-mediated antibiotic resistance genes (ARGs) have recently become a more prominent concern in the global environment. However, the prevalence of aminoglycoside resistance plasmids in the livestock industry is under reported. In this study, two transferable aminoglycoside resistance plasmids, pRKZ3 and pKANJ7, isolated from pig and chicken manure, were characterized. Results showed that pRKZ3 (8236 bp) is a non-conjugative IncQ plasmid and contains genes encoding for plasmid replication and stabilization (repA, repB and repC), mobilization (mob), and antibiotic resistance (arr-3 and aacA). pKANJ7 (30142 bp) is a conjugative IncX plasmid which codes for a type IV secretion system (T4SS). Conjugative transfer experiments showed that the optimal mating time of pKANJ7 was 8 h under the starvation condition, but the number of tranconjugants increased with time under the nutrient condition. Statistical analysis indicated that the two plasmids had little impact on the growth of their hosts, but a relatively high level of fitness cost due to pKANJ7 was observed. We also found that the fitness cost of plasmids depended on their hosts. Compared with pKANJ7, the relative fitness cost index of pRKZ3 varied within a narrow range during the 10 days of competition. The low level of fitness cost of pRKZ3 might contribute to the persistence of the plasmid in the environment. Our study provides new information for understanding the characterizations of antibiotic resistance plasmids (ARPs) in manure sources and helps to clarify the transfer and persistence of ARPs in the environment following the application of manure.