Prevalence Of High-level Aminoglycoside Resistance Research Articles

Prevalence of High Level Gentamicin Resistance among the Clinical Isolates of Enterococci Species

Enterococci infections, have drawn attention of clinicians due to rapid increase in high level aminoglycoside resistance (HLAR). This resistance predicts failure of β-lactam antibiotic and aminoglycoside combination, which is the current treatment of choice for serious enterococci infections. This led us to investigate about the prevalence of HLAR enterococci in our hospital setting in Shimoga, Karnataka. All the clinical samples received at Microbiology laboratory, McGan hospital, Shivamogga between June 2016 and December 2016 was considered for the study. Enterococci were identified and further speciated by following conventional method. Antibiotic susceptibility pattern of all the isolates was determined according to CLSI guidelines. High level gentamicin resistance was detected by disc diffusion method using 120µg gentamicin disc. A total of 64 Enterococci species were isolated from the clinical specimens. On speciation, Enterococcus faecalis (E. faecalis) accounted for 72% (46) of the total isolates, 24%(16) of the isolates were Enterococcus faecium (E. faecium)and 4% (2) isolates were Enterococcus durans (E. durans). High level gentamicin resistance was noted in 42% (27) among the total isolates. E. faecium was found to be more resistant compared to E. faecalis. E. durans was a sensitive strain. Our study reconfirms the high prevalence of HLAR in the clinical setting. The study stresses on the need for regular screening of HLAR in all Enterococci infections and revise the battery of drugs for its treatment according to the report.

Linezolid and Vancomycin Resistant Enterococci: A Therapeutic Problem.

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. 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. 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. 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. 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.

Prevalence and comparison of high-level aminoglycoside resistance in vancomycin-sensitive and vancomycin resistant enterococcus at a tertiary care hospital in Rohillkhand region

Introduction: Enterococci, originally commensals of gastrointestinal tract, have now become important nosocomial pathogens. The serious infections caused by Enterococci were empirically treated with bactericidal combination of beta lactam drugs and aminoglycoside neither of which are effective alone [1]. But the presence of high level aminoglycoside resistance (HLAR) makes this treatment ineffective. The emergence of VRE (Vancomycin Resistant Enterococcus) strains also resistant to ampicillin and HLAR has made the treatment further difficult. The spread of such strains in a health care environment has to be constrained and so the present study was carried out to highlight the occurrence of HLAR strains and VRE strains in our hospital .The frequency of association of HLAR with VSE (Vancomycin sensitive Enterococci) and VRE (Vancomycin resistant Enterococci) and any significant difference between the two was also studied. Methods: A total of 100 Enterococci were isolated from 6272 clinical specimen during a study period of 1 year. These strains were speciated on the basis of biochemical tests. Antimicrobial susceptibility test was performed by Kirby baeur disc diffusion method. High level Aminoglycoside resistance was tested by two methods 1) 150μg gentamicin and 200 μg streptomycin disc 2) Agar screening method. Similarly, strains resistant to Vancomycin by disc diffusion method were subjected to confirmatory test by determining their MIC by Agar dilution. Results: A total of 100 Enterococci were isolated during a study period of one year. The prevalence of HLAR was found to be 49%.The prevalence of VRE was found to be 12%.VRE strains also possessing resistance to High strength Gentamycin and or streptomycin was 8%.The frequency of association of HLAR in VRE was 1.5 times higher as compared to VSE. Conclusion: The prevalence of High level gentamicin and high level streptomycin resistance amongst Enterococcal isolates in our institute was high. More enterococcal strains were found to be resistant to both gentamicin and streptomycin than to gentamicin or streptomycin alone. The HLAR rate in VRE was 1.5 times higher than in VSE.

High-level aminoglycoside resistance in Enterococcus faecalis and Enterococcus faecium causing invasive infection: Twelve-year surveillance in the Minami Ibaraki Area.

We examined prevalence of high-level aminoglycoside resistance (HLAR) in Enterococcus faecalis and Enterococcus faecium causing invasive infection in the Minami Ibaraki Area. Ten strains of both species each, recovered from the blood or the cerebrospinal fluid between 2003 and 2014, were randomly selected every year. High-level resistance to gentamicin (HLR-GM) and streptomycin (HLR-SM) was detected in 34% (41 of 120 strains) and 18% (21) of E.faecalis and 9% (11) and 39% (48) of E.faecium, respectively. In comparisons of the proportions among three four-year periods, HLR-SM among E.faecium was significantly lower in the 2011-2014 period. All strains with HLR-GM were positive for the aac(6')-Ie-aph(2″)-Ia gene. The ant(6')-Ia gene was detected in all with HLR-SM except for one E.faecalis strain. The present study showed that prevalence of HLR-GM among E.faecalis and E.faecium causing invasive infection in this area was nearly equivalent to that described in previous studies in Japan and that proportions of strains with HLAR did not vary during the study period except for that of HLR-SM among E.faecium.

Rapid increase in the prevalence of high-level aminoglycoside resistance among enterococci isolated from blood cultures during 1989–1991

At St Elizabeth Hospital Medical Center in Youngstown, Ohio, USA, the first blood culture isolate of Enterococcus faecalis with high-level gentamicin resistance (MIC > 2000 mg/L) was seen in 1985, and the prevalence of high-level gentamicin resistance among enterococci isolated from blood cultures during 1985-8 was 9%. During the period 1989-91, the prevalence of high-level gentamicin resistance among enterococci isolated from blood cultures increased to 35% (44 of 126 strains). Increases in the prevalence of high-level resistance to amikacin, tobramycin, netilmicin, kanamycin and streptomycin were also demonstrated. Ten of 44 strains (23%) with high-level gentamicin resistance did not exhibit high-level resistance to streptomycin. Of the 126 strains of enterococci, 52% had high-level resistance to at least one aminoglycoside.

Comparison of four methods for testing high-level aminoglycoside resistance in enterococci

In a prospective study the prevalence of high-level aminoglycoside resistance (MIC greater than or equal to 2,000 micrograms/ml) among 62 clinically significant enterococci was investigated. A total of 10(5) organisms were inoculated a) onto a plate containing 2,000 micrograms/ml of gentamicin or streptomycin; b) into a microtube for dilution MIC determinations for gentamicin, amikacin, tobramycin and streptomycin; and c) into a single tube containing 500 micrograms/ml of gentamicin, amikacin, tobramycin or streptomycin in supplemented Mueller-Hinton broth. In addition, tubes containing 500 micrograms/ml of gentamicin, amikacin, tobramycin or streptomycin were inoculated with five enterococcal colonies ("crude" method). For 45 of the 62 isolates, MICs of gentamicin, amikacin and tobramycin were less than or equal to 500 micrograms/ml, while 17 (27%) showed high-level resistance. The MICs of streptomycin were less than or equal to 500 micrograms/ml for 42 of 62 isolates, and greater than or equal to 2,000 micrograms/ml for 20 (32.3%). For 8 of the 17 (47%) isolates showing high-level gentamicin resistance, MICs of streptomycin were less than or equal to 500 micrograms/ml. There was complete agreement between the results of the plate method, the microtube dilution MIC and the tube inoculated with 10(5) CFU, but the crude method gave discordant results for two isolates. It is concluded that a tube containing 500 micrograms/ml of aminoglycoside is a simple, accurate and inexpensive method for determining high-level aminoglycoside resistance.

The prevalence of high-level aminoglycoside resistance among enterococci isolated from blood cultures during 1980–1988

Two hundred and eighty-one strains of enterococci isolated from blood cultures of 281 consecutive patients during 1980-1988 and 108 strains of enterococci isolated from miscellaneous clinical materials during 1988 were studied for high-level resistance (MIC greater than 2000 mg/l) to amikacin, kanamycin, streptomycin, gentamicin, tobramycin and netilmicin. Before 1985 there was no enterococcal strain with high-level resistance to amikacin, gentamicin, tobramycin or netilmicin, but 14% were resistant to kanamycin and 21% to streptomycin. For strains isolated from blood cultures during 1985-1988, the prevalence of high-level resistance was as follows: amikacin, less than 1%; kanamycin, 35%; streptomycin, 26%; gentamicin, 9%; tobramycin, 9%, netilmicin, 4%. Prevalence of high-level aminoglycoside resistance of enterococci isolated from miscellaneous sources during 1988 was higher (amikacin, 5%; kanamycin, 37%; streptomycin, 31%; gentamicin, 24%, tobramycin, 27%; netilmicin, 10%). Among strains isolated from blood cultures between 1980-1984, 24% (30 of 126 strains) and among 1985-1988 strains, 40% (62 of 155 strains) were resistant to at least one of the aminoglycosides tested. Similarly, among the miscellaneous strains, 40% (43 of 108 strains) had high-level resistance to at least one of the aminoglycosides tested.

Molecular epidemiology of nosocomial, multiply aminoglycoside resistant Enterococcus faecalis.

The prevalence of high-level aminoglycoside resistance among Enterococcus faecalis at the Memphis VA Medical Center was 23.6% (59 of 250 isolates) from October to December 1986. Hybridization to a probe cloned from Ent. faecalis pIP1800 for 6' acetyltransferase-2" phosphotransferase (AAC6'-APH2") was observed in 55 (93.2%) of the resistant isolates and was associated with gentamicin resistance. Hybridization to a probe cloned from Ent. faecalis pJH1 for 3', 5" phosphotransferase type III (APH3', 5" III) was observed in 28 (47.4%) and was associated with streptomycin resistance. Twenty-five of the 32 isolates which were resistant to both gentamicin and streptomycin hybridized to both probes. Cell mating in conjunction with hybridization indicated that the AAC6'-APH2" gene is transferred separately from that for APH3', 5" (III), and the streptomycin resistant gene is cotransferred with the latter. The gentamicin-streptomycin resistant isolates therefore contain genes from two Ent. faecalis plasmids, and resistance to these two antibiotics appears to transfer separately. The genetic homogeneity of these isolates suggests nosocomial transmission of enterococci.