Status of high level aminoglycoside resistantEnterococcus faeciumandEnterococcus faecalisin a rural hospital of central India

Antibiogram of Urinary Enterococcus Isolates from a Tertiary Care Hospital

PURPOSE

Urinary tract infection (UTI) is one of the serious infections caused by the bacteria Enterococci. Vancomycin-Resistant Enterococci (VRE) is a persevering clinical problem globally. This study aims to detect high-level aminoglycoside and vancomycin resistance in uropathogenic Enterococcus spp.

METHODOLOGY

A total of 75 clinically relevant Enterococcus spp. grown from urine samples, were collected following convenience non-random sampling method. Identified by standard biochemical tests and susceptibility to antibiotics was studied by Kirby Bauer's disc diffusion method. The MIC of vancomycin was detected by agar dilution test. Van A, and Van B genes in VREs were detected by PCR.

RESULTS

Among 75 Enterococcal isolates, 43 (57.3%) were E. faecalis, 12 (16%) were E. faecium, 6 (8%) of each were E. pseudoavium and E. casseliflavus, 5(6.66%) were E. dispar and 3 (4%) were E. durans. E. faecalis (n=19) and E. faecium (n=3) were resistant to High Level Streptomycin (HLS). E. faecalis (n=21) and E. faecium (n=6) were resistant to High Level Gentamicin (HLG). 4 (9.3%) E. faecalis were vancomycin-resistant, out of which 3 were of Van A, and one was both Van A and Van B genotype.

CONCLUSION

Isolation of high level aminoglycoside resistant (HLAR) Enterococci is a challenge for the treating physician because aminoglycoside cannot be used in combination with glycopeptide or ampicillin for such isolates. The occurrence of HLAR, Van A, and Van B VRE genotypes is a cause of concern as they may transfer drug resistance genes to other bacterial isolates, thus leading to limited therapeutic options.

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.

Genetic characterization of high-level aminoglycoside-resistant Enterococcus faecalis and Enterococcus faecium isolated from retail chicken meat

Retail chicken meat can play a role in the transfer of drug resistance to humans through the handling or ingestion of improperly cooked meat contaminated with resistant enterococci. In fact, high-level aminoglycoside-resistance (HLAR) in enterococci identified in human cases. Therefore, the prevalence and genetic characterization of HLAR in enterococci in retail chicken meat were investigated in this study. Of the 345 enterococci strains, 29 (8.7%) showed HLAR. All HLAR in enterococci carried at least 1 of 2 aminoglycoside-modifying enzyme genes, aac(6')Ie-aph(2″)-Ia and ant(6)-Ia. Among the 13 isolates that carried aac(6')Ie-aph(2″)-Ia, 3 had pattern A, with IS256 at both ends, and the other 10 had pattern D, without IS256 at both ends. All HLAR in enterococci also showed multidrug resistance. Among the 24 erythromycin-resistant enterococci, 19 (79.2%) harbored the ermB gene, and one (4.2%) harbored both the ermB and ermA genes. A total of 21 enterococci were tetracycline-resistant and harbored one or more of the following tetracycline resistance genes tet(M), tet(L), and tet(O). The Int-Tn gene was detected in one isolate (3.4%) carrying the tet(M) and ermB genes. All 4 chloramphenicol-resistant isolates carried either the phenicol resistance gene cfr alone (one isolate), both cfr and fexA (one isolate), or both fexA and optrA (2 isolates). Four efflux pump genes, efr(A), efr(B), emeA, and lsa, were detected in all HLAR in Enterococcus faecalis isolates. These results improve our understanding of the transmission dynamics of HLAR in enterococci from non-hospital sources to humans.

Species, antibiotic susceptibility profiles and van gene frequencies among enterococci isolated from patients at Mulago National Referral Hospital in Kampala, Uganda

Background

The increase in drug resistance to affordable antibiotics used to treat Gram positive bacterial infections has complicated the management of enterococcal infections. Resistance to vancomycin, one of the most powerful antibiotics, is of utmost concern as both intrinsic and acquired forms of resistance do occur in enterococci. This cross-sectional study aimed to determine the species, antibiotic susceptibility profiles and vanA/vanB gene frequencies among enterococci isolated from patients at Mulago Hospital in Kampala, Uganda.

Methods

Between November 2011 and October 2012, stool, urine, sputum and blood samples, as well as vaginal, endocervical, pus, ear and urethra swabs from 3229 patients were processed for isolation of bacteria, yielding 162 enterococci of which 115 were available for analysis (one isolate per specimen/patient). Species-level confirmation and susceptibility testing were determined with the Phoenix™ AST/ID Automated System, while vanA/vanB gene carriage was determined by PCR.

Results

Species-level identification revealed 72 isolates of E. faecalis, 20 E. gallinarum/casseliflavus, 5 E. faecium, 4 E. raffinosus and 2 isolates each for E. hirae and E. durans. Ten isolates could not be identified to species level. Antibiotic resistance was generally low especially to ampicillin, quinolones, nitrofurantoin, glycopeptides and linezolid, but high for erythromycin and tetracycline. Equally, vanA and vanB gene frequencies were low (i.e. 15.8 and 7.9%, respectively) and detected only in E. casseliflavus/gallinarum species that are intrinsically resistant to vancomycin. Vancomycin resistant isolates of E. faecalis and E. faecium were not detected.

Conclusions

Enterococcus species are frequent in clinical specimens at Mulago Hospital but they are highly susceptible to common antibiotics especially ampicillin. While vancomycin resistant enterococcal (VRE) isolates of E. faecium and E. faecalis are rare in the hospital and frequency of multidrug resistance is low, non-faecium and non-faecalis VRE isolates (i.e. E. gallinarum/casseliflavus) are frequent, some with VanA/VanB (high-level) vancomycin resistance. Therefore, species-level identification of enterococci is necessary in resource limited settings to guide infection control and treatment of enterococcal infections.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4136-7) contains supplementary material, which is available to authorized users.

Linezolid and Vancomycin Resistant Enterococci: A Therapeutic Problem

INTRODUCTION

Enterococci are recognized as opportunistic pathogens, as well as commensals in both humans and animals. They are an important cause of nosocomial infections, difficult to treat, as the organism have intrinsic and acquired resistance to many antibiotics.

AIM

To isolate and identify clinically relevant Enterococcus up to species level from all the clinical samples processed in the microbiology laboratory and also to study their resistance pattern.

MATERIALS AND METHODS

A prospective study was carried out for a period of one year from May 2014 to April 2015 at the Department of Microbiology, Subharti Medical College, Meerut, Uttar Pradesh, India. A total of 200 isolates of Enterococcus species from 15342 clinical samples obtained from IPD/OPD patients irrespective of age, having suspicion of bacterial infection were processed in the microbiology laboratory. Identification was done with standard biochemical methods. Antibiotic susceptibility testing was done on Muller Hilton agar plate by Kirby Bauer disc diffusion method. High-Level Gentamycin Resistance (HLGR) and High-Level Streptomycin Resistance (HLSR) were further confirmed by Agar dilution method and Broth microdilution method. Vancomycin and linezolid resistance was further confirmed by Agar dilution method and MIC was calculated by using VITEK 2, Biomerieux. All methodology was followed as per Clinical and Laboratory Standards Institute (CLSI) M100-S 24, 2014 guidelines.

RESULTS

E. faecalis (n=169, 84.5%) was the predominant species isolated, followed by E. faecium (n=27, 13.5%) and E. casseliflavus (n=4, 2%). A total of 25 (12.5%) isolates were HLGR, 13 (6.5%) isolates were HLSR and 62 (31%) isolates were HLGR+HLSR. Vancomycin resistance was found in 14 (7%) isolates of which 11 (78.5%) were Van A and 3 (21.4%) were Van B, detected phenotypically as per relative MIC of vancomycin and teicoplanin. Linezolid resistance was seen in 4 (2%) of isolates which were vancomycin as well as high-level gentamycin and high-level streptomycin resistant.

CONCLUSION

Isolation of Enterococcus species resistant to most of the higher antibiotics like vancomycin and linezolid, with high prevalence of High-Level Aminoglycoside Resistance (HLAR), from hospitalized patients is a major concern as such isolates have limited or no therapeutic option.

The prevalence of aminoglycoside-modifying enzyme and virulence genes among enterococci with high-level aminoglycoside resistance in Inner Mongolia, China

This study highlights the prevalence of aminoglycoside-modifying enzyme genes and virulence determinants among clinical enterococci with high-level aminoglycoside resistance in Inner Mongolia, China. Screening for high-level aminoglycoside resistance against 117 enterococcal clinical isolates was performed using the agar-screening method. Out of the 117 enterococcal isolates, 46 were selected for further detection and determination of the distribution of aminoglycoside-modifying enzyme-encoding genes and virulence determinants using polymerase chain reaction -based methods. Enterococcus faecium and Enterococcus faecalis were identified as the species of greatest clinical importance. The aac(6′)-Ie-aph(2″)-Ia and ant(6′)-Ia genes were found to be the most common aminoglycoside-modifying enzyme genes among high-level gentamicin resistance and high-level streptomycin resistance isolates, respectively. Moreover, gelE was the most common virulence gene among high-level aminoglycoside resistance isolates. Compared to Enterococcus faecium, Enterococcus faecalis harbored multiple virulence determinants. The results further indicated no correlation between aminoglycoside-modifying enzyme gene profiles and the distribution of virulence genes among the enterococcal isolates with high-level gentamicin resistance or high-level streptomycin resistance evaluated in our study.

High-level aminoglycoside resistance and virulence characteristics among Enterococci isolated from recreational beaches in Malaysia

We report the first study on the occurrence of high-level aminoglycoside-resistant (HLAR) Enterococci in coastal bathing waters and beach sand in Malaysia. None of the encountered isolates were resistant to high levels of gentamicin (500 μg/mL). However, high-level resistance to kanamycin (2,000 μg/mL) was observed in 14.2 % of tested isolates, the highest proportions observed being among beach sand isolates. High-level resistance to kanamycin was higher among Enterococcus faecalis and Enterococcus faecium than Enterococcus spp. Chi-square analysis showed no significant association between responses to tested antibiotics and the species allocation or source of isolation of all tested Enterococci. The species classification of encountered Enterococci resistance to vancomycin was highest among Enterococcus spp. (5.89 %) followed by E. faecium (4.785) and least among E. faecalis. A total of 160 isolates were also tested for virulence characteristics. On the whole, caseinase production was profoundly highest (15.01 %) while the least prevalent virulence characteristic observed among tested beach Enterococci was haemolysis of rabbit blood (3.65 %). A strong association was observed between the source of isolation and responses for each of caseinase (C = 0.47, V = 0.53) and slime (C = 0.50, V = 0.58) assays. Analysis of obtained spearman's coefficient showed a strong correlation between caseinase and each of the slime production (p = 0.04), gelatinase (p = 0.0035) and haemolytic activity on horse blood (p = 0.004), respectively. Suggestively, these are the main virulent characteristics of the studied beach Enterococci. Our findings suggest that recreational beaches may contribute to the dissemination of Enterococci with HLAR and virulence characteristics.

Enterococcal Bacteremia is Associated with Prolonged Stay in the Medical Intensive Care Unit

Background:

Although enterococci are relatively common nosocomial pathogens in surgical intensive care units (ICUs), their significance in blood cultures from patients in the medical ICU is unclear.

Materials and Methods:

In this retrospective study spanning 2 years, the clinical and microbiological characteristics of enterococcal bacteremia among medical ICU patients were evaluated.

Results:

Of 1325 admissions, 35 with enterococcal bacteremia accounted for 14.8% of positive blood cultures. They were significantly older (P=0.03) and had various co-morbidities. Most had vascular (96.9%) and urinary (85.3%) catheters, and 67.7% were mechanically ventilated. In addition to blood, enterococci were isolated from vascular catheters (8.6%) and other sites (20%), while no focus was identified in 77% of patients. Prior use of broad-spectrum antimicrobials was nearly universal. All isolates tested were sensitive to vancomycin and linezolid. Resistance to ampicillin and gentamicin were 44.7% and 52.6%, respectively. Compared with other medical ICU patients, patients with enterococcal bacteremia had a longer ICU stay (P<0.0001) and a trend toward higher ICU mortality (P=0.08).

Conclusions:

Enterococcal bacteremia is an important nosocomial infection in the medical ICU, with a predilection for older patients with multiple comorbidities. Its occurrence is associated with a significantly longer ICU stay and a trend to a higher mortality. The choice of antibiotics should be dictated by local susceptibility data.

Development of a colorimetric assay for rapid quantitative measurement of clavulanic acid in microbial samples

We developed a colorimetric assay to quantify clavulanic acid (CA) in culture broth of Streptomyces clavuligerus, to facilitate screening of a large number of S. clavuligerus mutants. The assay is based on a β-lactamase-catalyzed reaction, in which the yellow substrate nitrocefin (λ (max)=390 nm) is converted to a red product (λ (max)=486 nm). Since CA can irreversibly inhibit β-lactamase activity, the level of CA in a sample can be measured as a function of the A (390)/A (486) ratio in the assay mixture. The sensitivity and detection window of the assay were determined to be 50 μg L(-1) and 50 μg L(-1) to 10 mg L(-1), respectively. The reliability of the assay was confirmed by comparing assay results with those obtained by HPLC. The assay was used to screen a pool of 65 S. clavuligerus mutants and was reliable for identifying CA over-producing mutants. Therefore, the assay saves time and labor in large-scale mutant screening and evaluation tasks. The detection window and the reliability of this assay are markedly better than those of previously reported CA assays. This assay method is suitable for high throughput screening of microbial samples and allows direct visual observation of CA levels on agar plates.