High-level Gentamicin Resistance Research Articles

Analysis of the phenotypic and genotypic antimicrobial resistance profiles of clinically significant enterococci isolated in the Provincial Specialist Hospital in Lublin, Poland

Abstract The increasing significance of enterococci as healthcare-associated pathogens can be linked to their limited susceptibility to antibiotics. In this study, phenotypic and genotypic resistance profiles of 35 [n=18 E. faecium (Efm); n=17 E. faecalis (Efs)] invasive isolates cultured from hospitalized patients were analysed. Phenotypic identification was verified by the multiplex PCR targeting the 16S rDNA and the ddl genes encoding for the Efs and Efm – specific ligases. Antimicrobial susceptibility was determined using the disc diffusion method and E-tests. The high-level streptomycin resistance (HLSR), high-level gentamicin resistance (HLGR) and glycopeptide resistance was verified by amplification of the ant(6)-Ia, aac(6’)-Ie-aph(2’’)-Ia, as well as vanA and vanB genes, respectively. More than 70% of all isolates were cultured from patients in the Intensive Care and Internal Medicine Units. Blood was the predominant (77%) site of isolation. All Efm isolates were resistant to ampicillin, imipenem, and norfloxacin; 17 isolates demonstrated high-level aminoglycoside resistance (HLAR), including 27.7% with HLSR, 38.8% with HLGR and 27.7% with both phenotypes. HLAR was also common in Efs (HLSR>70%, HLGR>50%), followed by norfloxacin (64.7%) and ampicillin (11.7%) resistance. The ant(6)-Ia and aac(6’)-Ie-aph(2’’)-Ia genes were detected in >90% of the HLSR and HLGR isolates, respectively. Glycopeptide resistance was detected in 4 (22.2%) Efm isolates and mediated by the vanA gene. 19 (54.3%) isolates were multidrug resistant, including 17 (89.5%) Efm. All isolates were susceptible to linezolid. The study constitutes a contribution to the analysis of enterococcal antimicrobial resistance in Polish hospitals. The monitoring of enterococcal prevalence and antimicrobial resistance is crucial to control and prevent infections.

Antibiotic resistance of Enterococcus species: 3-year data

Aim: The aim of this study is to investigate the prevalence of Enterococcus species and to evaluate susceptibilities to antimicrobial agents in a state (secondary) hospital.
 Material and Methods: A total of 1676 enterococci strains (490 E.faecium, 1146 E.faecalis, 10 E.casseliflavus/E.gallinarum and 30 other Enterococcus species) isolated from cultures obtained from January 2017 to December 2019 in XXX Hospital were included. Blood cultures were incubated in automated device (Render Biotech Co.Ltd., PRC). Other cultures were incubated with conventional methods. Grown colonies were identified by PhoenixTM 100 automated system (Becton Dickinson, USA). Identifications that need confirmation or strains identified to genus level were further evaluated with conventional techniques. Antimicrobial susceptibility testing were performed by same system, Kirby-Bauer disc diffusion and gradient strip method according to EUCAST guidelines.
 Results: 43.1%, 27.1%, 14.7% and 15.1% of enterococci were isolated from urine, blood/sterile body fluids, wound/abscess and other samples. Majority of the strains were ciprofloxacin (72.0%) and levofloxacin (74.1%) resistant, and more than 40% showed ampicillin and high-level gentamicin resistance. Glycopeptide resistance was relatively high (5.4%), especially when considering E.faecium (12.1%). There was not any tigecycline and linezolid resistance. 
 Conclusions: Antimicrobial resistance is a serious and growing public health problem affecting all countries, which is not just a topic of medicine, but multiple sectors such as commercial companies, food industry, veterinarians, etc. High percentages of resistance strongly indicate to get a local action, which should be followed by national and global one.

Antimicrobial resistance of <i>Enterococcus faecium</i> and <i>Enterococcus faecalis</i>, isolated from blood culture of patients with hematological malignancies during different study periods

Objective: to determine antimicrobial resistance of Enterococcus faecium and Enterococcus faecalis isolated from blood culture of hematological patients during different study periods.Materials and methods. Antimicrobial susceptibility of Enterococcus spp., collected as part of the multicenter study was tested by the broth microdilution method (USA Clinical and Laboratory Standards Institute (CLSI), 2018), to daptomycin by Etest (bioMeriéux, France). High-level gentamicin resistance (HLGR) and high-level streptomycin resistance (HLSR) was performed by the agar dilution method (CLSI (Oxoid, UK), 2018).Results. The susceptibility of 366 E. faecium (157 in 2002-2009 and 209 in 2010-2017) and 86 E. faecalis (44 in 20022009 and 42 in 2010-2017) was studied. In the second study period (2010-2017) the rise of vancomycin-resistant E. faecium (VREF) increased from 8.3 % to 23.4 % (p = 0.0001), and two linezolid-resistant (LREF) were identified. All VREF and LREF remained susceptible to daptomycin and tigecycline. The rate of susceptible to tetracycline E. faecium remained the same (73.9 and 74.6 %), and an increase in susceptibility to chloramphenicol (74.5 and 82.3 %) was observed. Susceptibility of E. faecium to tetracycline was detected with almost the same rate and in a part of isolates, the increase of susceptibility to chloramphenicol was registered during the analyzed periods. The rise of E. faecium susceptible to HLGR and HLSR has increased significantly in 2010-2017 compared to 2002-2009. Erythromycin, levofloxacin, ampicillin and penicillin had the least activity against E. faecium (less than 5 %).All E. faecalis were susceptible to tigecycline, linezolid, and teicoplanin. Only one of E. faecalis had intermediate resistance to vancomycin. High susceptibility to ampicillin in E. faecalis remained unchanged (97.7 and 97.6 %, respectively). In the second period of the study the rise of susceptible E. faecalis decreased significantly to penicillin (from 97.7 % to 76.2 %), to levofloxacin (from 59.1 % to 31 %), to HLSR (from 52.3 % до 31 %), and to HLGR (from 47.7 % to 26.2 %), remained unchanged to chloramphenicol (52.3 % and 50 %) and was minimal to erythromycin and tetracycline.Conclusion. The study demonstrated higher rates of antibiotic resistance among E. faecium, which consisted of an increase in VREF and the appearance of linezolid-resistant strains. High susceptibility to ampicillin remained in E. faecalis, but there was an increase in resistance to penicillin and aminoglycosides.

Emergence of aac(6')-Ie-aph(2'')-Ia-positive enterococci with non-high-level gentamicin resistance mediated by IS1216V: adaptation to decreased aminoglycoside usage in Taiwan.

To explore the mechanisms mediating the different levels of gentamicin resistance in enterococci. Susceptibility testing with gentamicin and PCR of resistance determinants were performed in 149 enterococcal isolates. Genetic relatedness was characterized by MLST and PFGE analysis. Sequences of the aac(6')-Ie-aph(2'')-Ia gene and its surrounding environment were determined by Illumina sequencing. Stability assays of gentamicin resistance were carried out to evaluate the probability of loss of the high-level gentamicin resistance (HLGR) phenotype. A total of 17 (11.4%) aac(6')-Ie-aph(2'')-Ia-positive enterococcal isolates (2 Enterococcus faecalis and 15 Enterococcus faecium) with non-HLGR phenotype were found. MLST analysis revealed that the 2 E. faecalis belonged to ST116 and ST618, while all the 15 E. faecium belonged to clonal complex 17. Sequence analysis demonstrated that IS1216V was inserted into the 5'-end of aac(6')-Ie-aph(2'')-Ia, leading to loss of HLGR phenotype. Three IS1216V insertion types were found, and type II and III were frequently found in E. faecium. Interestingly, a total of 38 aac(6')-Ie-aph(2'')-Ia-positive E. faecium with HLGR phenotype also had type II or type III IS1216V insertion. Sequencing of the aac(6')-Ie-aph(2'')-Ia-positive HLGR E. faecium E37 revealed that an intact aac(6')-Ie-aph(2'')-Ia was located adjacent to IS1216V-disrupted aac(6')-Ie-aph(2'')-Ia. In a non-antibiotic environment, E37 tended to lose HLGR phenotype with a probability of 1.57 × 10-4, which was largely attributed to homologous recombination between the intact and disrupted aac(6')-Ie-aph(2'')-Ia. This is first study to elucidate that the E. faecium is capable of changing its HLGR phenotype, which may contribute to adaptation to hospital environments with decreased usage of gentamicin.

High-level Gentamicin Resistance among Clinical Isolates of Enterococci in Iran: a Systematic Review and Meta-analysis.

Enterococci have been considered as one of the most common causes of nosocomial infections. The spread of antibiotic resistance has posed a serious challenge to treating the enterococcal infections. High-level aminoglycosides resistance leads to failure in the synergistic combination therapy.This study aimed to estimate the prevalence of high-level gentamicin resistance (HLGR) among clinical isolates of enterococci in Iran.Systematic literature search was conducted in the Web of Science, PubMed, Scopus and Google Scholar electronic databases from ar-ticles which were published from April 2000 to September 2018. Literature search yielded 918 studies. Eligible studies were selected ac-cording to the defined inclusion and exclusion criteria. Statistical heterogeneity was estimated by Q statistic and the I2 index. The Begg's rank correlation test and Egger's weighted regression tests were used to evaluate possible publication bias.Nineteen studies were included in this review. According to the meta-analysis results, the prevalence of HLGR among Enterococcus spp. was 49.4% (95% CI: 42.2%-56.6%). It was estimated 44.3% (95% CI: 38.1%-50.8%) and 66.3% (95% CI: 51.4%-78.6%) for E. faecalis and E. faecium, respectively.Since notable rate of HLGR in enterococci was seen in this analysis, improving the implementation of all aspects of the infection control programmes is required. Accurate and regular monitoring of infection control procedures are necessary for reducing the dissemination of such infections.

Phenotypic Characterisation, Virulence Determination and Antimicrobial Resistance Pattern of Enterococcus Species Isolated from Clinical Specimen in a Tertiary Care Hospital in Kolkata

Introduction: Enterococci are usually normal human commensal of gastrointestinal tract predominantly. They are considered as an important nosocomial pathogen now a day due to its intrinsic as well as increasing acquired antibiotic resistance resulting in a great threat to modern Medicine. Aim: To determine prevalence of Enterococci isolated from clinical specimens with special reference to its virulence and antibiogram conventionally. Materials and Methods: A cross-sectional observational study was conducted over a period of two years (January 2019 to December 2020) with 326 Enterococci, isolated from various clinical specimens received by Department of Microbiology. Enterococci isolated from stool samples were excluded. They were identified and speciated conventionally as per standard laboratory protocol. Gelatinase, haemolysin and biofilm formation was determined for each isolate. Their antibiogram was also determined by disc diffusion methods over Blood agar followed by Minimum Inhibitory Concentration (MIC) testing (as per Clinical and Laboratory Standards Institute (CLSI) guideline). All statistical analysis was done by Chi-square test using Software Statistical Package for the Social Sciences (SPSS) version 22.0. Results: Among the total 4516 samples collected, growth of Enterococci was noted in 7.22% cases. Out of them, E. faecalis (84.05%) out numbered E. faecium. Urine was the most predominant (55.22%) sample. 73.93% isolates produced biofilm whereas 18.40% produced haemolysin and 19.94% produced gelatinase. Most of the isolates were susceptible to vancomycin (94.79%) and linezolid (98.77%). High level gentamicin resistance was seen in 54.6% cases. Ciprofloxacin was the most resistant antibiotic. Vancomycin Resistance Enterococcus (VRE) was detected in 5.21% cases only, out of which Van A type was detected phenotypically in most cases. Conclusion: The high rate of resistance to high-level gentamicin could fail treatment of gentamicin in combination with penicillin group of antibiotics. In clinical samples, the emergence of VRE strains makes treatment options more challenging.

Antimicrobial Resistance in Enterococcus faecalis and Enterococcus faecium Bacteria Isolated from Bloodstream Infections: A Single-Center Evaluation

Objective: Enterococci are an important cause of healthcare-related bloodstream infections. The present study aimed to contribute to form empirical treatment models that can be used in the treatment of Enterococcus faecalis and Enterococcus faecium bacteria isolated from bloodstream infections in our hospital by reviewing their resistance status against antibiotics, requently used in the treatment of these bacteria. Methods: In our study, the resistance status of E. faecalis and E. faecium bacteria isolated from bloodstream infections in Sivas Cumhuriyet University, Health Services Practice and Research Hospital between January 2015 and June 2020 against ampicillin, amoxicillin, clavulanic acid, high-level gentamicin, linezolid, teicoplanin, and vancomycin was examined retrospectively. The diagnosis of healthcare-related bloodstream infections was made using the diagnostic criteria of “Centers for Diseases Control and Prevention (CDC).” Results: A total of 227 enterococcal isolates were evaluated within the scope of our study between the specified dates. The percentage of patients with Enterococcus bacteria isolated in their blood cultures were 44.5% male, and 55.5% female. Of the isolates, 60.8% were identified as E. faecalis and 39.2%as E. faecium. High-level gentamicin resistance was found to be 25.3% in E. faecalis isolates, and no resistance was found against vancomycin, teicoplanin, and linezolid. In E. faecium isolates, while the highest resistance was observed against amoxicillin-clavulanic acid and ampicillin with 87.6%, vancomycin resistance was determined to be 3.3%. No resistance to linezolid was identified. Conclusions: Enterococci cause life-threatening infections and there are some difficulties in the treatment. Especially since E. faecium has higher resistance against antibiotics, the agents to be chosen in the treatment of infections caused by these bacteria are limited. Therefore, the current local resistance data will be useful in developing rapid and appropriate treatment models, especially in cases when empirical treatment is required. We think that our study will contribute to the literature in this regard.

Study on prevalence of Vancomycin Resistant Enterococcus and high level Gentamicin resistance among Enterococcus isolates in a Pediatric tertiary care hospital

Vancomycin resistance and high level aminoglycoside resistance in Enterococci has limited its treatment, as Enterococci are susceptible to only narrow spectrum of antibiotics. VRE is known to cause hospital acquired infections. This study was aimed to determine prevalence of vancomycin resistance and HLG resistance among Enterococci in a Pediatric hospital. 310 spp was isolated between Jan 2018- May 2020 from pediatric patients from various samples. Among them 206 (66.5%) isolates were , 104 (33.5%) isolates were spp including . Most of the isolates were from urine (68%). High Level Gentamicin (HLG) resistance was seen in 69% of the isolates. Vancomycin resistance (VRE) was seen in 29 (9.4%) isolates. HLG resistance among VRE was 79% (23/29), all of them were sensitive to Linezolid. 17 of the VRE isolates were from urine sample and 15 (88%) of these isolates were sensitive to Nitrofurantoin. 90% (26/29) of the VRE isolates were isolated from nosocomial infections. 58% of VRE isolates were

Clinical and molecular epidemiology of vancomycin-resistant Enterococcus faecium bacteremia from an Indian tertiary hospital.

Wedetermined the clinical and molecular epidemiology of emerging nosocomial vancomycin-resistant Enterococcus faecium (VREfm)-causing serious bloodstream infections (BSIs) and the correlations between antibiotic resistance and virulence determinantsamong isolates. Allisolates were confirmed by molecular methods (16SrRNA and E. faecium ddl genes) and tested for disk diffusion. PCRwas used to detect aac(6')-aph(2″), vanA and vanB resistance genes, and asa1, cylA, ace, esp, gelE and hyl virulence genes. VREfm and high-level gentamicin-resistant (HLGR) representative isolates were selected to characterize by pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). Of 173 isolates, 73(42.2%), 146(84.4%), and 0(0.0%) were vanA-containing VREfm, aac(6')-aph(2″)-positive HLGR, and vanB-positive. Independent predictors of VREfm infection were hematological malignancies (P = 0.001) and previous hospitalizations (P = 0.007). Observed mortality rate was 34.7%. Independent predictors of BSI-related mortality were endotracheal intubations (P < 0.001), gastrointestinal diseases (P = 0.002), and pulmonary disease (P < 0.001). All VREfm were resistant to vancomycin, teicoplanin, ciprofloxacin, and erythromycin. The esp, hyl, ace, asa1, cylA, and gelE genes were detected at 55.9, 22.5, 2.9, 2.3, 1.7, and 1.2%, respectively. The esp gene was significantly associated with VREfm compared toVSEfm (P = 0.001). PFGE analysis revealed 23 clones, with 7 major clones. The MLST analysis revealed the following five sequence types: ST80, ST17, ST117, ST132, and ST280, all belonging to CC17. The emergence and expansion of VREfm CC17 with limited antibiotic options in our hospital present a serious public health menace and represent challenges to infection control.

High-level resistance to aminoglycosides and ampicillin among clinical isolates of Enterococcus species in an Iranian referral hospital.

Background and Objectives:Nowadays, high-level aminoglycosides and ampicillin resistant Enterococcus species are among the most common causes of nosocomial infections. The present study was conducted to determine the prevalence of high-level resistance to aminoglycosides and ampicillin among clinical isolates of Enterococcus species in Ardabil, Iran.Materials and Methods:In this cross–sectional study, a total of 111 Enterococcus species were collected from different clinical specimens between 2013 and 2015. Enterococcus species were identified using standard phenotypic and genotypic methods. BHI agar screen and agar dilution methods were used for detection of high-level gentamicin and streptomycin resistance (HLGR and HLSR) and minimal inhibitory concentration (MIC) of ampicillin, respectively.Results:Of 111 clinical isolates, 59 (53.2%) and 25 (22.5%) isolates were E. faecalis and E. faecium, respectively, based on the PCR results. Totally, 60.3% and 56.7% of isolates were HLGR and HLSR, respectively, as well as 51.35% were HLGR plus HLSR. Among HLGR isolates, 36 (61.01%), 18 (72%) and 13 (48.14%) were E. faecium, E. faecalis and non-faecalis non-faecium species, respectively. Among HLSR isolates, 33 (55.93%), 16 (64%) and 14 (51.85%) were E. faecalis, E. faecium and non-faecalis non-faecium species, respectively. All HLGR isolates contained aac(6′)Ie-aph(2″)Ia gene. Overall, the prevalence of high-level ampicillin resistance among Enterococcus species was 17.1%. For E. faecalis, E. faecium and non-faecalis non-faecium species, ampicillin resistance rates were as follows: 11 (40.74%), 7 (28%) and 1 (1.69%), respectively. For aminoglycoside antibiotics, the resistance rate was significantly higher in E. faecium isolates and for ampicillin it was higher in E. faecalis isolates.Conclusion:The frequency of high-level aminoglycoside resistant enterococcal isolates in our hospital was high and significant ampicillin resistance was noticed. This would require routine testing of enterococcal isolates for HLAR and ampicillin susceptibility.

Companion psittacine birds as reservoir of gentamicin and vancomycin-resistant Enterococcus spp.

ABSTRACT: Enterococcus are recognized worldwide as significant nosocomial agents that have been continuously envolving to adapt to different niches and acquire resistance to several antibiotic classes. Vancomycin and gentamicin-resistant strains of E. faecalis and E. faecium have been associated with nosocomial human infections. Some epidemiological studies suggest the participation of pets as reservoirs of vancomycin and gentamicin-resistant Enterococcus strains. However, the role of companion birds as reservoirs of these strains has been poorly studied. In this study, 126 psittacine birds were evaluated and 26.9% carried Enterococcus spp., including the species E. faecalis, E. faecium, E. hirae, E. phoeniculicola, E. gallinarum and E. casseliflavus. The antibiotic resistance profile showed four high-level gentamicin-resistance (HLGR) strains. In addition, two strains presented intermediate levels of vancomycin resistance. Resistant strains were isolated from fecal and oropharynx samples of sick and clinically healthy birds, suggesting that psittacine birds may act as reservoirs of HLGR Enterococcus spp. However, sick birds appear to be more implicated in the enterococci transmission than healthy birds.

Clonal dissemination of high-level gentamicin-resistant isolates of Enterococcus faecalis within auniversity hospital in southeastern Iran.

Combination of acell wall-active antibiotic with an aminoglycoside confers a synergistic effect in the treatment of some severe enterococcal infections. Unfortunately, with the emergence of enterococci with high-level resistance to aminoglycosides, particularly to gentamicin, the efficacy of the synergistic combinations has decreased. In this study, high-level gentamicin-resistant (HLGR) isolates of enterococci and the diversity of the genes encoding aminoglycoside-modifying enzymes (AMEs) as well as putative clonal dissemination of HLGR isolates were investigated in auniversity hospital in southeastern Iran. The minimum inhibitory concentration of gentamicin was determined and HLGR isolates were investigated for AME genes. Genetic similarity between isolates was analyzed using repetitive extragenic palindromic (rep)-Polymerase Chain Reaction (PCR) assay. Of 150 Enterococcus isolates, 62isolates including Enterococcus faecalis (n = 46) and E.faecium (n = 16) were identified as HLGR. The most prevalent AME genes in both species were as follows: aph(3')-IIIa (n = 44), aac(6')-Ie-aph(2')-Ia (n = 36), and ant(4')-Ia (n = 15). The rep-PCR analysis showed clonality among E.faecalis isolates, so that 27isolates were grouped in seven clusters representing similarity greater than 95%. No link between AME determinants and clusters was found. Clonal spread of HLGR isolates of E.faecalis was found within our hospital. More rigorous recommendations are required to avoid dissemination of such resistant microorganisms in the hospital setting.

Detection of antibiotic resistance profiles and aminoglycoside-modifying enzyme (AME) genes in high-level aminoglycoside-resistant (HLAR) enterococci isolated from raw milk and traditional cheeses in Turkey.

The aim of this study was isolation and identification of the high-level aminoglycoside-resistant (HLAR) enterococci in raw milk and dairy products and to analyze their antibiotic resistance and the presence of aminoglycoside-modifying enzyme (AME) genes. A total of 59 HLAR enterococci were isolated from raw milk and traditional cheese samples. Thirty-nine of the 59 HLAR enterococci were isolated on streptomycin-containing agar medium, while the other 20 HLAR strains were isolated on gentamicin containing agar medium. The 59 HLAR enterococci were identified as 26 E. faecalis (44.07%), 18 E. faecium (30.51%), 13 E. durans (22.03%), and two E. gallinarum (3.39%) by species-specific PCR. Disk diffusion tests showed that teicoplanin were the most effective antibiotics used in this study, while 89.83% of isolates were found to be resistant to tetracycline. High rates of multiple antibiotic resistance were detected in HLAR isolates. Minimum inhibitory concentration (MIC) values of HLAR enterococci against streptomycin and gentamicin were found in the range of 64 to > 4096 µg/mL. Forty-seven (79.66%) of the 59 HLAR enterococci were found to be both high-level streptomycin-resistant (HLSR) and high-level gentamicin-resistant (HLGR) by MIC tests. However, no correlation was found between the results of the disk diffusion and MIC tests for gentamicin and streptomycin in some HLAR strains. The aph(3')-IIIa (94.92%) was found to be most prevalent AME gene followed by ant(4')-Ia (45.76%), ant(6')-Ia (20.34%) and aph(2'')-Ic (10.17%). None of the isolates contained the aac(6')-Ie-aph(2'')-Ia, aph(2'')-Ib or aph(2'')-Id genes. None of the AME-encoding genes were identified in E. durans RG20.1, E. faecalis RG22.4, or RG26.1. In conclusion, HLAR enterococci strains isolated in this study may act as reservoirs in the dissemination of antibiotic resistance genes.

Is there any association between antibiotic resistance and virulence genes in Enterococcus isolates?

Objective: In this study, we aim to determine the frequency of antibiotic resistance and five virulence genes in Enterococcus species and the relationship between antibiotic resistance and virulence genes.&#x0D; Material and Methods: A total of 86 Enterococcus strains isolated from inpatients between 2015 and 2016 were included. Identification and antibiotic susceptibilities of strains were determined using a BD Phoenix fully automated system. The presence of virulence-associated genes (esp, gel E, asa1, hyl, and cyl) were investigated by using PCR method.&#x0D; Results: Of the 86 Enterococcus strains, 53 (61.6%) and 33 (38.4%) were Enterococcus faecium and Enterococcus faecalis, respectively. Vancomycin and high-level gentamicin resistance (HLGR) in E. faecalis strains were 0.6% and 60.6%, respectively. Furthermore, 52 of the 53 E. faecium strains were both vancomycin-resistant and HLGR. The frequency of esp, gel E, asa1, cyl, and hyl was 91.9%, 60.5%, 54.7%, 43%, and 26.7%, respectively. The asa 1, cyl, and gel E genes were detected at high frequencies in vancomycin-susceptible and non-HLGR strains, whereas hyl gene was detected at high frequencies in vancomycin-resistant and HLGR strains.&#x0D; Conclusion: Virulence genes were more frequent in vancomycin-susceptible and non-HLGR Enterococcus strains than in the resistant strains. Although infections caused by multidrug-resistant strains are difficult to treat, it should be considered that susceptible strains have more virulence genes. This may reduce the in vivo efficacy of drugs and lead to treatment failures. Therefore, in addition to the in vitro susceptibilities of drugs, clinical efficacy should be monitored.

Detection of high level aminoglycoside resistance genes among clinical isolates of Enterococcus species

BackgroundEnterococci are intrinsically resistant to clinically achievable concentrations of aminoglycosides. However, high-level resistance to aminoglycosides (HLAR) is primarily due to the acquisition of genes encoding aminoglycoside-modifying enzymes (AMEs). Aminoglycosides along with cell wall inhibitors are given clinically for treating enterococcal infections. The current study was conducted to investigate the rate of HLAR and to determine aminoglycoside resistance encoding genes profile in enterococcal isolates from different clinical specimens.ResultsFrom 120 Enterococcus species, 50 (41.7%) enterococcal isolates were proven to have HLAR, 78% (39/50) have high-level gentamicin resistance (HLGR), and 74% (37/50) were high-level streptomycin-resistant (HLSR). HLGR isolates carried aminoglycoside modifying gene aac (6′)-Ie-aph (2′)-Ia in 26/39 (66.7%) of isolates, whereas 32/37 (86.5%) of HLSR carried aph (3′)-IIIa gene and were observed in E. faecalis, E. faecium, E. gallinarum, and E. casseliflavus. The aph (2′)-Ib, aph (2′)-Ic, and aph (2′)-Id that encode HLGR could not be detected.ConclusionsThe high detection rate of HLAR among the studied Enterococcus species and the coexistence of HLGR and HLSR strains provide crucial insights to the necessity of routine testing for HLAR in the microbiology lab. The main AME genes among HLGR and HLSR enterococci were aac (6′)-Ie-aph (2″)-Ia and aph (3′)-IIIa, respectively.

High-level aminoglycoside resistance and distribution of aminoglycoside resistance genes among Enterococcus spp. clinical isolates in Tehran, Iran.

Enterococci have gained attention during the past decade as important nosocomial pathogens. Their increasing prevalence has been paralleled by the occurrence of multidrug-resistant and high-level aminoglycoside-resistant strains. This study isolated Enterococcus spp. from hospital samples and determined their antibiotic resistance profile, focusing on aminoglycosides, and associated resistance mechanisms. A total of 195 enterococci from hospital samples in Tehran were studied. Isolates were identified by biochemical reactions. Antimicrobial resistance was determined by disk diffusion. The vancomycin MIC for vancomycin-resistant isolates was determined by agar dilution. Detection of aminoglycoside resistance genes and intI1 and intI2 gene was performed by PCR. The majority of isolates were Enterococcus faecalis (65.1%), followed by Enterococcus faecium (31.8%), Enterococcus gallinarum (2.6%) and Enterococcus solitarius (0.5%). According to antibiogram results, 42.1% of isolates were high-level gentamicin-resistant (HLGR) and 40.5% were high-level streptomycin-resistant (HLSR). There was a high prevalence of aac(6')-Ie-aph(2")-Ia (96.3%) among HLGR isolates. ant(6)-Ia and aadA were identified in 93.7% and 64.6% of HLSR isolates, respectively. aph(2'')-Ic was detected in 7 isolates (3.6%) and aph(2'')-Ib in only 4 isolates (2.1%); no isolates harboured aph(2'')-Id, intI1 or intI2. Multidrug resistance was higher among HLGR and HLSR isolates compared with non-HLGR and non-HLSR isolates, which may result in limited treatment options. More than 50% of isolates were susceptible to aminoglycosides, thus correct identification in clinical laboratories and administration of these antibiotics can result in decreased used of antibiotics such as vancomycin and linezolid and help to reduce the emergence of resistance to these drugs.

Antibiotic Susceptibility Patterns, Biofilm Formation and esp Gene among Clinical Enterococci: Is There Any Association?

Enterococci are commonly found in humans, animals and environments. Their highly adaptive mechanisms are related to several virulent determinants and their ability to resist antibiotics. Data on the relationship between the esp gene, biofilm formation and antibiotic susceptibility profiles may differ between countries. This cross-sectional study was conducted to determine the proportion of esp gene and biofilm formation among Enterococcus faecalis and Enterococcus faecium clinical isolates. We also investigated the possible association between the esp gene with antibiotic susceptibility patterns and biofilm formation. The isolates were collected from clinical samples and identified using biochemical tests and 16SRNA. Antibiotic susceptibility patterns and a biofilm assay were conducted according to the established guidelines. Molecular detection by PCR was used to identify the esp gene using established primers. In total, 52 and 28 of E. faecalis and E. faecium were identified, respectively. E. faecium exhibited higher resistance rates compared to E. faecalis as follows: piperacillin/tazobactam (100% versus 1.9%), ampicillin (92.8% versus 1.9%), high-level gentamicin resistance (HLGR) (89.3% versus 25.0%) and penicillin (82.1% versus 7.7%). E. faecium produced more biofilms than E. faecalis (59.3% versus 49.0%). E. faecium acquired the esp gene more frequently than E. faecalis (78.6% versus 46.2%). Interestingly, the associations between ampicillin and tazobactam/piperacillin resistance with the esp gene were statistically significant (X2 = 4.581, p = 0.027; and X2 = 6.276, p = 0.012, respectively). Our results demonstrate that E. faecium exhibits high rates of antimicrobial resistance, esp gene acquisition and biofilm formation. These peculiar traits of E. faecium may have implications for the management of enterococcal infections in hospitals. Thus, concerted efforts by all parties in establishing appropriate treatment and effective control measures are warranted in future.

High Prevalence of the aac(6')-Ie-aph(2'')-Ia Gene in Hospital Isolates of Enterococcus faecalis Co-Resistant to Gentamicin and Penicillin.

Objectives: This study aimed to characterize the molecular mechanism of resistance to gentamicin among penicillin-resistant, ampicillin-susceptible Enterococcus faecalis (PRASEF) isolates by investigating the presence of the aac(6')-Ie-aph(2'')-Ia gene. The co-resistance to antimicrobials of other classes was also evaluated. Results: Among the 151 isolates evaluated, 70 were PRASEF and 81 were penicillin-susceptible and ampicillin-susceptible E. faecalis (PSASEF). No β-lactamase producing isolate was detected. Eighty-three (55.0%) and 35 (23.2%) out of the 151 E. faecalis isolates showed high-level gentamicin resistance (HLGR) and high-level streptomycin resistance (HLSR) phenotypes. However, a significantly higher rate of PRASEF (88.6%) showed HLGR phenotype in comparison with PSASEF (23.5%) (p < 0.01). Conversely, a significantly lower rate of PRASEF (14.3%) showing HLSR was observed in comparison with PSASEF (30.9%) (p = 0.02). The prevalence of isolates displaying multidrug resistance (MDR) phenotype was significantly higher (p < 0.01) in the group of PRASEF (81.4%) than in PSASEF (18.6%). The majority of PSASEF (61.9%) and PRASEF (90.3%) isolates showing HLGR phenotype was harboring the aac(6')-Ie-aph(2'')-Ia gene, which encodes a bifunctional enzyme that inactivates all aminoglycosides except streptomycin. Conclusion: The aac(6')-Ie-aph(2'')-Ia gene was prevalent among the Brazilian PRASEF isolates that usually exhibit co-resistance to gentamicin and to multiple other drugs.

Faecal carriage of high-level aminoglycoside-resistant and ampicillin-resistant Enterococcus species in healthy Iranian children.

High-level aminoglycoside, ampicillin and vancomycin resistance and virulence genes among enterococcal isolates collected from healthy middle-school children in Ardabil, Iran, during 2016 were investigated. Totally, 305 faecal specimens were collected. Isolates underwent antimicrobial susceptibility testing, virulence gene detection and molecular typing. Totally, 409 enterococcal isolates were collected, comprising Enterococcus faecium (235; 57.5%), Enterococcus faecalis (56; 13.7%) and other Enterococcus spp. (118; 28.9%). Overall, 71 (17.4%), 11 (2.7%) and 10 (2.4%) isolates were identified as high-level streptomycin-resistant (HLSR), high-level gentamicin-resistant (HLGR) and ampicillin-resistant (AR), respectively. Among HLSR isolates, 40 (56.3%), 5 (7.0%) and 26 (36.6%) were E. faecium, E. faecalis and other Enterococcus spp., respectively. Among HLGR isolates 4 (36.4%) and 7 (63.6%) and among AR isolates 7 (70.0%) and 3 (30.0%) were E. faecium and other Enterococcus spp., respectively. Accordingly, 21.6%, 3.6% and 3.3% of subjects were colonised with HLSR, HLGR and AR Enterococcus spp. Carriage of HLGR, HLSR and AR isolates was associated with prior antibiotic consumption (P≤0.05). Additionally, male sex and antacid consumption were associated with AR enterococcal carriage. Moreover, 69 (97.2%), 10 (90.9%) and 9 (90.0%) of HLSR, HLGR and AR isolates were multidrug-resistant, respectively. No vancomycin-resistant enterococci were detected. ERIC-PCR revealed high genetic diversity among isolates. gelE and asa1 were major virulence genes both in E. faecalis and E. faecium. Presence of gelE was associated with HLSR and HLGR phenotypes (P≤0.05). Community intestinal carriage of HLSR enterococci was high; however, carriage of HLGR and AR enterococci was low.

Antimicrobial resistance profile and characterisation of enterococcus species from various clinical samples in a Tertiary care hospital

Background: Enterococcus is one of the leading causes of nosocomial infections, with E faecalis and E faecium accounting up to 90-95% of clinical isolates. During recent years, the occurrence of other Enterococcal species from clinical samples increased with the properties of resistance to many antibiotics. Thus appropriate identification of Enterococci at species level is crucial for the management and prevention of these bacteria in hospital settings. Hence, this study was undertaken to highlight the incidence of multi drug resistant enterococcal species from various samples from human infections, in a tertiary care hospital. Methods: This work was conducted in our institution from January 2009 to December 2011. About 112 enterococcal isolates from various clinical specimens were included in the study. The isolates were identified by standard microbiological methods. Antimicrobial susceptibility testing was carried out by using Kirby-Bauer disc diffusion method. The prevalence of High level Gentamicin resistance was identified. Vancomycin resistance was assessed by E-test. Result: The commonest species identified was E faecalis (87.5%), followed by E faecium (8.9%). 14% of isolates produced beta haemolysis and gelatinase. 15% and 24% were the haemolytic and gelatinase producing enterococci. High level resistance was shown towards tetracycline, Amikacin, Cholramphenicol. Vancomycin resistance was identified in single isolate. Conclusion: There is achange in isolation pattern of enterococcal species. Besides, there is an increased rate of infection with multidrug resistant enterococci species, which necessitates frequent antimicrobial surveillance.