{"id":40049,"date":"2021-09-30T11:46:48","date_gmt":"2021-09-30T11:46:48","guid":{"rendered":"https:\/\/biomedpharmajournal.org\/?p=40049"},"modified":"2021-10-11T07:22:37","modified_gmt":"2021-10-11T07:22:37","slug":"a-study-on-high-and-low-level-drug-resistance-pattern-among-clinical-isolates-of-enterococci","status":"publish","type":"post","link":"https:\/\/biomedpharmajournal.org\/staging\/vol14no3\/a-study-on-high-and-low-level-drug-resistance-pattern-among-clinical-isolates-of-enterococci\/","title":{"rendered":"A Study on High and Low level Drug Resistance Pattern Among Clinical Isolates of Enterococci"},"content":{"rendered":"

\u00a0Introduction<\/strong><\/p>\n

The genus Enterococci\u00a0 have exhibited the potential to harbour and transfer drug resistant genes and have become an important pathogen in clinical settings. In\u00a0 Enterococci, lower affinity of\u00a0 Penicillin Binding Proteins (PBP\u2019s) are responsible for decreased susceptibility to\u00a0Penicillin\u2019s. The Minimum Inhibitory concentration (MIC) of penicillin\u00a0 for Enterococci\u00a0 are higher than \u00a0that \u00a0for Streptococci and \u00a0inhibition of PBP\u2019s does not result in bactericidal activity in Enterococci 1<\/sup>.<\/p>\n

Enterococci<\/em> display low to moderate\u00a0 level resistance to aminoglycosides due to slow uptake or permeability of these agents. All Enterococci<\/em> have innate low level resistance to aminoglycosides with minimal inhibitory concentration ranging from 4 \u00b5g\/ml to as high as\u00a0256 \u00b5g\/ml. High level resistance to Gentamicin is associated with bifunctional enzyme possessing acetylase (6\u2019<\/sup>) and phosphotransferase (2\u2019<\/sup>) activities conferring resistance to all aminoglycosides except Streptomycin 2<\/sup>. Enterococci<\/em> also exhibits acquired resistance via\u00a0mutations in existing DNA or through acquisition of new DNA and high level resistance are usually due to the transferable plasmid mediated production of aminoglycoside inactivating enzymes 3<\/sup>.<\/p>\n

Beta lactamase \u00a0producing Enterococci<\/em> exhibits inducible and constitutive low level resistance 4<\/sup>.\u00a0 In clinical isolates of E. faecium<\/em>, \u03b2 lactamase resistance is associated with mutations or overproduction of PBP5 with Ampicillin MIC of >256 mg\/L in some strains.\u00a0Isolates of E. faecium<\/em> with MIC of Ampicillin \u226464 mg\/L may respond to high dose Ampicillin therapy 5<\/sup>.<\/p>\n

Quinolone resistance occurs by mutation in the quinolone resistance determining regions of the genes that encodes gyrase and topoisomerase IV and have been observed in clinical \u00a0isolates of Enterococci. These mutations prevent efficient binding of the antibiotics to the\u00a0enzymes which enable DNA replication to continue despite the presence of antibiotics. The second mechanism contributes to quinolone resistance are Multidrug resistance efflux pumps (MDRs) on bacterial chromosomes. Inactivation of homolog of quinolone resistance (Qnr)\u00a0identified in E. faecalis <\/em>resulted in modest decrease in resistance to quinolones and over expression of gene results in increased resistance 6<\/sup>.<\/p>\n

The most common form of acquired resistance to macrolides is production of an enzyme (erm B gene) that methylates a specific adenine in the 23 S rRNA of the 50S ribosomal subunit there by reducing the binding affinity of this drug for the ribosome, which also reduces the\u00a0binding of Lincosamide and Streptogramin to the ribosome. An efflux pump encoded by transferrable mefA gene is known to pump macrolides out of the cell and confers low level resistance in Enterococci. 7<\/sup><\/p>\n

Linezolid has been reported to cure VRE endocarditis and other serious intravascular infections, bacteremia, UTI and skin and soft tissue infections 8<\/sup>. Tigecycline displays broad spectrum of activity and potency against Staphylococcus<\/em>, Streptococci<\/em> and Enterococci<\/em> with\u00a0MIC 90 <\/sub>value of \u2264 12\u00b5g\/ml.Tigecycline may play a role in combination therapy with bactericidal agents such as Vancomycin, Gentamicin, Rifampicin or Daptomycin. Combinations of Daptomycin (8 mg\/kg) plus Ampicillin plus Gentamicin and Daptomycin\u00a0plus Gentamicin plus Rifampicin have been reported to be successful in cases of Vancomycin resistant endocarditis 9<\/sup>.<\/p>\n

One of the major concerns that physicians face during treatment of Enterococcal infection is the probability of developing resistance during therapy, which may lead to therapeutic failures and contributes to patient mortality. Monitoring the resistance pattern of clinical isolates of Enterococci<\/em> is a useful tool to obtain information on the prevalence of multidrug resistant isolates and thereby limiting the spread of bacterial resistance.<\/p>\n

Aim and Objectives<\/strong><\/p>\n

To determine the Minimum Inhibitory Concentration of various antibiotics \u00a0against Enterococci\u00a0 by Vitek 2 automated system.<\/p>\n

To detect High Level Gentamicin Resistance among Enterococci by various phenotypic methods.<\/p>\n

To correlate phenotypic and genotypic characteristics of Enterococci<\/em> with low level and high level drug resistance.<\/p>\n

Materials and Methods<\/strong><\/p>\n

A total of\u00a0 774\u00a0 isolates of\u00a0 Enterococci obtained from various clinical samples \u00a0<\/em>were subjected to antimicrobial susceptibility testing on Muller Hinton Agar \u00a0by Kirby-Bauer disk diffusion method and the plates were incubated for 16-18 hrs at 370<\/sup>C.The diameter of the\u00a0zone of inhibition was measured and zone size interpreted according to CLSI standards 10<\/sup><\/p>\n

The antibiotic disks used were Penicillin (10 U), Amoxicillin Clavulanic acid (20\/10\u03bcg),<\/p>\n

Erythromycin (15\u03bcg), High Level Gentamicin (120 \u03bcg), Linezolid (30\u03bcg), Teicoplanin (30 \u03bcg), Ciprofloxacin (5\u03bcg), Levofloxacin (5 \u03bcg) and Nitrofurantoin (300\u03bcg) .Zones of inhibition were measured and recorded and the organism was interpreted as sensitive or\u00a0resistant as per the recommendations from CLSI guidelines using Enterococcus faecalis<\/em> ATCC 29212 as control. Screening for \u00a0\u00a0isolates resistant to\u00a0 Vancomycin and High Level Gentamicin was done on Brain Heart Infusion agar containing 6\u00b5g\/ml of vancomycin and\u00a0500 \u00b5g\/ml of Gentamicin respectively. Inoculum of 10 \u03bcL of 0.5 McFarland\u2019s was spot inoculated. Presence of more than 1 colony was interpreted as a resistant strain. 11<\/sup> Multiplex PCR was performed to detect the \u00a0presence of vancomycin resistance genes., vanA and van B\u00a0using the following primers (Sigma Aldrich, USA).12<\/sup><\/p>\n

Gene: VanA (732 bp)<\/p>\n

Primer: F (+) – GGGAAAACGACAATTGC (position: 176\u2013192)<\/p>\n

R (-) – GTACAATGCGGCCGTTA (position : 907\u2013891)<\/p>\n

Gene: VanB (647 bp)<\/p>\n

Primer: F (+) – ACGGAATGGGAAGCCGA (position: 169\u2013185)<\/p>\n

R (-) \u2013 TGCACCCGATTTCGTTC (position: 815\u2013799)<\/p>\n

Minimum Inhibitory Concentration for Gentamicin\u00a0 was determined by agar dilution method\u00a0 and Epsilometer test. Agar dilution was performed by on Brain heart infusion agar by using\u00a0 500 \u03bcg , 1000 \u03bcg\u00a0 and 2000 \u03bcg of Gentamicin. To detect Gentamicin resistance by E test,MIC\u00a0strips coated with Gentamicin in a concentration gradient of 0.064-1024 \u03bcg\/ml was used\u00a0 . MIC was read when the ellipse intersects MIC scale on the strip.11<\/sup><\/p>\n

Turbidometrically controlled bacterial pure growths were suspended into sterile physiological saline and this suspension was used to fill Vitek 2 Compact system and antimicrobial susceptibility testing cards.13<\/sup> For biochemical identification\u00a0 of isolates in Vitek system, the\u00a0following parameters were used: Growth in 6.5 % NaCl, \u03b2- glucuronidase, Trehalose, Arginine dihydrolase, D-sorbitol, Urease, Raffinose, D-galactose, D-mannitol, Sucrose, \u03b2-galactosidase, Salicin, L-pyrrolidonyl arylamidase, D-xylose, D-maltose, Methyl- \u03b2-D-glycopyranoside, D-ribose, \u03b1-glucosidase, \u03b1- mannosidase, Phosphatase etc. 14<\/sup><\/p>\n

Minimum inhibitory concentrations for the following antibiotics were tested: Penicillin, Erythromycin, Vancomycin, Teicoplanin, Ciprofloxacin, Levofloxacin, Tigecycline, Nitrofurantoin, Linezolid and Daptomycin.<\/p>\n

Results<\/strong><\/p>\n

Out of 774 samples studied ,\u00a0 726 (93.80 %)\u00a0 isolates were Enterococcus faecalis,<\/em> followed by Enterococcus faecium<\/em>, 33 (4.26 %), Enterococcus avium<\/em>, 12 (1.55 %) and Enterococcus durans<\/em>, 3 (0.39 %).<\/p>\n

Out of 30 Vancomycin resistant isolates obtained by agar screen method from 774 samples, resistant phenotype was detected in 18 isolates by Vitek 2 automated system.15 out of\u00a0 18 \u00a0isolates showed the presence of \u00a0vancomycin resistant genes by multiplex PCR.<\/p>\n

10 (90.91 %) isolates out of 11 E. faecalis <\/em>with van A gene showed high level resistance to Penicillin (16-64 \u00b5g\/ml), 8 (72.73 %) out of 11 isolates showed high level resistance to Gentamicin (512-1024 \u00b5g\/ml), 6 (54.55 %) , out of 11 isolates were resistant to \u03b2 lactams due<\/p>\n

to the modification of Penicillin binding proteins [Table 1]. One (9.09 %) out of 11 isolates were resistant to Linezolid, 10 (90.91 %) isolates showed resistance (\u2265 8\u00b5g\/ml) and one isolate showed intermediate resistance (2 \u00b5g\/ml) to Ciprofloxacin.<\/p>\n

Nine (81.82 %) isolates showed resistance (\u2265 8\u00b5g\/ml) and 2 (18.18 %) showed intermediate resistance (4 \u00b5g\/ml)\u00a0 to Levofloxacin, 9 (81.82 %) isolates showed resistance (\u22658\u00b5g\/ml) and 2 (18.18 %) showed intermediate resistance (1-4 \u00b5g\/ml)\u00a0 to Erythromycin. 6\/11 (54.55 %) showed resistance and \u00a02 (18.18 %) were with intermediate resistance to Nitrofurantoin.<\/p>\n

One isolate of E. faecalis <\/em>from urine with van B gene showed high level resistance to Penicillin (32 \u00b5g\/ml), Linezolid (\u2265 8\u00b5g\/ml), high level resistance to Gentamicin (1024 \u00b5g\/ml), Fluoroquinolones (\u2265 8\u00b5g\/ml) and Macrolides (\u2265 8\u00b5g\/ml). One E.faecium<\/em> isolate with van A\u00a0gene showed susceptibility to Penicillin with high level resistance to Gentamicin (1024 \u00b5g\/ml). One E. faecalis <\/em>isolate from pus\u00a0 with both van A and van B gene showed high level resistance to Penicillin (32 \u00b5g\/ml), Linezolid (\u2265 8 \u00b5g\/ml), high level resistance to Gentamicin\u00a0(1024 \u00b5g\/ml),Fluoroquinolone(\u2265 8\u00b5g\/ml) and\u00a0 intermediate\u00a0 resistance to macrolides(4 \u00b5g\/ml).<\/p>\n

Table 1: Resistance profile of Vancomycin resistant Enterococci<\/em><\/strong><\/p>\n\n\n\n\n\n\n\n\n\n
Sample<\/strong><\/td>\nIsolates<\/strong><\/p>\n

(n=15)<\/strong><\/td>\n

Genotypes<\/strong><\/td>\nResistance profile (MIC)<\/strong><\/td>\n<\/tr>\n
Penicillin<\/strong><\/td>\nHLG<\/strong><\/td>\n\u03b2 lactams<\/strong><\/td>\n<\/tr>\n
Urine<\/td>\nE. faecalis<\/em><\/p>\n

(11 isolates )<\/td>\n

vanA<\/td>\n8-64 (R)<\/p>\n

11 (100 %)<\/td>\n

512-1024<\/p>\n

8 (72.73 %)<\/td>\n

Positive<\/p>\n

6 (54.55 %)<\/td>\n<\/tr>\n

Pus<\/td>\nE. faecalis<\/em><\/td>\nvanA & vanB<\/td>\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 32 (R)<\/td>\n1024 (R)<\/td>\n <\/p>\n

–<\/td>\n<\/tr>\n

Urine<\/td>\nE. faecalis<\/em><\/p>\n

(1 isolate )<\/td>\n

vanB<\/td>\n32 (R)<\/td>\n1024 (R)<\/td>\n–<\/td>\n<\/tr>\n
Urine<\/td>\nE. faecium<\/em><\/td>\nvanA<\/td>\n2 (S)<\/td>\n1024 (R)<\/td>\n <\/p>\n

–<\/td>\n<\/tr>\n

Urine<\/td>\nE. durans<\/em><\/td>\nvanA<\/td>\n16 (R)<\/td>\n1024 (R)<\/td>\n <\/p>\n

–<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

No significant association was found between Vancomycin resistant\u00a0 genotypes of Enterococci<\/em>\u00a0 and \u00a0their high and low\u00a0 levels of resistance to Penicillin, Gentamicin and \u03b2 lactams (p value >0.05) [Table:2, 3 and 4].<\/p>\n

Table 2: Relation between van genotypes and high and low level Penicillin resistance.<\/strong><\/p>\n\n\n\n\n\n
Isolate<\/strong><\/td>\nGenotype<\/strong><\/td>\nLow Level Resistance \u22648\u00b5g<\/strong><\/td>\nHigh Level Resistance<\/strong><\/p>\n

\u00a0(16-64 \u00b5g)<\/strong><\/td>\n<\/tr>\n

E. faecalis <\/em><\/strong>(11)<\/strong><\/td>\nvanA<\/td>\n1(9.09)<\/td>\n10 (90.9)<\/td>\n<\/tr>\n
E. faecium <\/em><\/strong>(1)<\/strong><\/td>\nvanA<\/td>\n0 (0.00)<\/td>\n0 (0.00)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Table 3: Relation between van genotypes and high and low level Gentamicin resistance.<\/strong><\/p>\n\n\n\n\n\n
Isolate<\/strong><\/td>\nGenotype<\/strong><\/td>\nLow Level Resistance<\/strong><\/p>\n

\u00a0(64-512 \u00b5g)<\/strong><\/td>\n

High Level Resistance<\/strong><\/p>\n

\u00a0(512-1024\u00b5g)<\/strong><\/td>\n<\/tr>\n

E. faecalis <\/em><\/strong>(11)<\/strong><\/td>\nvanA<\/td>\n0 (0.00)<\/td>\n8 (72.73)<\/td>\n<\/tr>\n
E. faecium <\/em><\/strong>(1)<\/strong><\/td>\nvanA<\/td>\n0 (0.00)<\/td>\n1 (100)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Table 4: Relation between van genotypes and high and low level resistance to \u03b2 lactams<\/strong><\/p>\n\n\n\n\n\n
Isolate<\/strong><\/td>\nGenotype<\/strong><\/td>\nLow Level Resistance<\/strong><\/p>\n

\u00a0(<\/strong>Penicillin Binding Protein modification)<\/td>\n

High Level Resistance \u00a0(<\/strong>\u03b2 lactamase)<\/td>\n<\/tr>\n
E. faecalis <\/em><\/strong>(11)<\/strong><\/td>\nvanA<\/td>\n6 (54.55)<\/td>\n0 (0.00)<\/td>\n<\/tr>\n
E. faecium <\/em><\/strong>(1)<\/strong><\/td>\nvanA<\/td>\n0 (0.00)<\/td>\n0 (0.00)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Discussion<\/strong><\/p>\n

Enterococci possess remarkable ability to acquire antibiotic resistance determinants. The ability of these organisms to colonise the gastrointestinal tract\u00a0 of\u00a0 hospitalised\u00a0 patients for\u00a0 prolonged\u00a0 period\u00a0 is a crucial factor\u00a0 that influences\u00a0 the development of drug\u00a0 resistance. With the increased use of Vancomycin and wide spectrum antibiotics in the health care setting, these organism have been identified as common etiology of nosocomial infection .<\/p>\n

Enterococci<\/em> exhibit decreased susceptibility to Penicillins and Ampicillins as a result of expression of low level Penicillin Binding Proteins (PBPs). Isolates of Enterococci<\/em> susceptible to Penicillin are predictably susceptible to Ampicillin, Amoxicillin, Ampicillin-\u00a0Sulbactam, Amoxycillin-Clavulanate, Piperacillin and Piperacillin-Tazobactam for non \u03b2<\/p>\n

lactamase producing Enterococci<\/em>. Isolates of Enterococci <\/em>susceptible to Ampicillin cannot be assumed to be susceptible to Penicillin 10<\/sup>.In the present \u00a0study, 82.17 % isolates were resistant to Penicillin by disk diffusion method. About.19.90 % (154\/774) isolates were with\u00a0 MIC\u00a0range of 16-64 \u00b5g. In a similar study from Delhi, S Jain et al., 2011 have reported 100 % isolates resistant to Penicillin by disk diffusion method 15<\/sup>. In the present study, out of E. faecium<\/em> isolates, 33.33 % showed MIC of \u2265 16 \u00b5g and 19.42 % of E. faecalis<\/em> were resistant\u00a0to Penicillin with MIC \u2265 16 \u00b5g. In a study from Chandigarh by V Gupta et al., 2007, 14 % isolates were with MIC of > 16 \u00b5g\/ml for Penicillin 16<\/sup>. In a study reported by Triveda , 2016 from South India, <\/strong>Penicillin resistance was found to be higher among E. faecium<\/em> (64.51 %)\u00a0isolates compared to E. faecalis<\/em> (48.45 %) 17<\/sup>. In the present study no significant difference in resistance to Penicillin was found between E. faecalis<\/em> and E. faecium<\/em> isolates (p value >0.05).<\/p>\n

High level resistance to \u03b2 lactam antibiotics are seen in E. faecium<\/em> due to the over production of low affinity Penicillin Binding Proteins (PBP\u2019s). A variety of point mutation in PBP has been described in E. faecalis<\/em> and E. faecium<\/em> 18<\/sup>. In our study, by vitek 2 automated system,\u00a0resistance to \u03b2 lactams due to modification of Penicillin Binding Proteins was detected in 40.70 % isolates. A similar study by S Sivasankari et al., 2013 have reported 72.70 % E. faecium<\/em> isolates resistant to Ampicillin compared to E. faecalis <\/em>(24.30 %) 19<\/sup> .In a North\u00a0Indian study, C S Aher et al., 2014 have reported 80.70 % Enterococci<\/em> isolates resistant to Ampicillin 20<\/sup><\/p>\n

The prevalence of Enterococci<\/em> with high level Gentamicin resistance are increasing and varies by geographical region and are generally resistant to all aminoglycosides with the\u00a0occasional exception of Streptomycin. Aminoglycoside Modifying Enzymes (AME\u2019s) are the most important mechanism mediating high level resistance. These enzymes confer high level resistance to more than one aminoglycoside. A single strain of Enterococci<\/em> may acquire\u00a0several AME\u2019s. Both E. faecalis<\/em> and E. faecium<\/em> may acquire 6\u2019- adenyl transferase which confer HLR to Streptomycin 3<\/sup>.\u00a0 By disk diffusion method, 53.49 % showed high level\u00a0Gentamicin resistance. In a \u00a0study from North India, D K Mendritta et al., 2008 have reported, 46 % isolates resistant to both high Level Gentamicin(HLG) and High Level\u00a0Streptomycin(HLS) by both disk diffusion and agar dilution method and combined resistance to both HLG and HLS was higher in E. faecium<\/em> compared to E. faecalis <\/em>21<\/sup>.In the present\u00a0study no significant difference in combined resistance to HLG and HLS was observed between E. faecalis <\/em>and E. faecium<\/em> (p value >0.05) where as HLGR was higher among E. faecium <\/em>isolates. In our study 15.89 % isolates showed high level resistance to Gentamicin\u00a0(2000 \u00b5g\/ml) by agar dilution method and 33.66 % isolates showed resistance to both Penicillin and High Level Gentamicin.<\/p>\n

By E test 18.22 % isolates showed MIC of 512 \u00b5g\/ml and 16.67 % were with MIC \u2265 1024 \u00b5g\/ml for Gentamicin. In the present study the results of Minimum Inhibitory Concentration for HLG were in concordance with disk diffusion method. A similar finding was reported in a\u00a0study by V P \u00a0\u00a0Prakash, 2005 22<\/sup>.In a South Indian study P Jyothi et al., 2014 have reported 40 % isolates from urine showed high level resistance to Gentamicin and Streptomycin by both disk diffusion and Enz MIC strip method 23<\/sup> .In a South Indian study by E Padmasini et al.,\u00a02014 among clinical isolates of Enterococci<\/em> \u00a0,42.7 % were HLGR (MIC \u2265 512 \u00b5g\/ml) by E test 24<\/sup>.In a study report by S Mittal et al., 2016, high level gentamicin resistance was more common among Enterococci<\/em> isolated from urine sample (41.50 %) compared to other clinical\u00a0samples and HLGR was found to be more common in VRE isolates compared to VSE 25<\/sup>where as our study showed no significant association between VRE and HLGR (p value >0.05).<\/p>\n

Quinolone resistance in Enterococci<\/em> is due to mutation in the quinolone resistance determining regions of the genes that encodes gyrase and topoisomerase IV enzymes. In the present study, 417 (57.44 %)\u00a0 E. faecalis <\/em>isolates were resistant to Ciprofloxacin (MIC \u2265 8\u00a0\u00b5g\/ml) and 414 (57.02 %) isolates to Levofloxacin (MIC \u2265 8 \u00b5g\/ml). About 57.23 % isolates of E. faecalis<\/em> were resistant to both Ciprofloxacin and Levofloxacin. 72.73 % E. faecium<\/em> isolates were resistant to the fluoroquinolones tested. Among the fluoroquinolone resistant\u00a0isolates, no significant difference was observed between E. faecalis <\/em>and E. faecium isolates<\/em> (p value >0.05). In a study from Tamilnadu S Sivasankari et al., 2013, 73.10 % E. faecalis<\/em> and\u00a081.80 % E. faecium<\/em> isolates were resistant to Ciprofloxacin by disk diffusion method 19<\/sup>. In a North Indian study, N Gangurde et al., 2014 have reported 80.5 % E. faecalis<\/em> and 86.2 % E.\u00a0<\/em>faecium<\/em> resistant to Ciprofloxacin 26<\/sup>.<\/p>\n

The most common form of acquired resistance to macrolides is production of enzymes that methylase a specific adenine in the 23S rRNA of 50 S ribosomal subunit which reduces binding affinity of macrolides to ribosomes .77.27 % isolates of E. faecalis<\/em> and 72.73 % E.\u00a0faecium isolate were resistant to Erythromycin (MIC \u2265 8\u00b5g\/ml) in this study. In the present study no statistically significant difference in Erythromycin resistance observed between E. faecalis <\/em>and E. faecium<\/em> (p value >0.05). Various Indian studies have reported Erythromycin\u00a0<\/em>resistance higher among E. faecium<\/em> compared to E. faecalis<\/em> 19<\/sup>, 26<\/sup>.<\/p>\n

Nitrofurantoin is active against E. faecium<\/em> and E. faecalis<\/em> and is effective in the treatment of VRE infection associated with urinary tract. A study conducted by G Zhanel et al., 2001 have\u00a0 reported that Nitrofurantoin is active against urinary isolates of E. faecalis<\/em> and E. faecium<\/em> 27<\/sup>.\u00a0In the present study from urinary isolates, 14.93 % E. faecalis<\/em> were resistant to Nitrofurantoin with MIC of 128 \u00b5g\/ml. The\u00a0 MIC for 1.81%\u00a0 isolates\u00a0 of E.\u00a0 faecalis<\/em>\u00a0 and 20.00 %\u00a0 E. faecium <\/em>\u00a0were\u00a0 256 \u00b5g\/ml and 128 \u00b5g\/ml respectively. About 2.07 % isolates showed\u00a0resistance to Nitrofurantoin in a study from Maharastra by S Bose et al., 2012 28<\/sup><\/p>\n

A similar study by D Atray et al., 2016 have reported 80 % urinary isolates susceptible to Nitrofurantoin 29<\/sup>.<\/p>\n

Linezolid resistance may be due to the presence of transferable plasmid borne cfr gene encoding methyl transferase or due to selective pressure imposed by antibiotic treatment.\u00a0Linezolid is used in the treatment of infections caused by resistant gram positive bacteria particularly Vancomycin – resistant Enterococcus faecalis<\/em>. Linezolid inhibits protein synthesis but at a different site from other agents that target the ribosome (Chloramphenicol,\u00a0Macrolides, Lincosamides, Streptogramin, Aminoglycosides, Tetracycline). As a result, existing mechanisms of resistance to these agents do not confer cross-resistance to Linezolid 30<\/sup>.\u00a0 Our study reports 1.16 % isolates resistant to Linezolid. In a North Indian study by G\u00a0Reena et al., 2013, 95 % isolates were susceptible to Linezolid 31<\/sup>. In \u00a0a \u00a0South \u00a0Indian \u00a0study , I Praharaj et al., 2013 \u00a0have reported isolates with 100 % \u00a0susceptibility \u00a0to \u00a0Linezolid 32<\/sup>. \u00a0In \u00a0a similar study by \u00a0K Archana Rao et al., 2014, \u00a012 %\u00a0 isolates \u00a0showed\u00a0 \u00a0resistance \u00a0to Linezolid 33<\/sup>.<\/p>\n

Tigecycline shows in vitro bacteriostatic activity against Vancomycin resistant Enterococci<\/em>. Tigecycline was found to be the most effective drug against Enterococci<\/em> in our study with\u00a0100 % susceptibility. Similar finding were reported from Indian studies 31, 32<\/sup><\/p>\n

As a result of mutation of chromosomal genes, Daptomycin resistance following therapy has been observed in clinical isolates of Enterococci<\/em>. Daptomycin synergy has been described in vitro with Ampicillin, Cephalosporins, Imipenem, Rifampin and Gentamicin 34<\/sup>. In our study,<\/p>\n

96.12 % isolates showed susceptibility to Daptomycin with MIC \u2264 4 \u00b5g\/ml.<\/p>\n

The overall antimicrobial pattern of the isolates showed significantly higher
\n(p value < 0.05) \u00a0percentage resistance to Penicillins, High level aminoglycosides, Macrolides, Fluoroquinolones and Linezolid among the clinical isolates\u00a0 of\u00a0 Enterococci.<\/p>\n

Conclusion<\/strong><\/p>\n

The present study reports significantly higher percentage resistance to Penicillins, High level aminoglycosides, Macrolides, Fluoroquinolones and Linezolid among the clinical isolates of Enterococci. The most effective drug against Vancomycin Resistant Enterococci<\/em> was found\u00a0to be Tigecycline. No significant association was found between Vancomycin resistant genotypes of Enterococci<\/em>\u00a0 and high and low\u00a0 levels of resistance to Penicillin, Gentamicin and \u03b2 lactams.<\/p>\n

Acknowledgement<\/strong><\/p>\n

We thank\u00a0 Dr. V .Anandi, Former Professor, Department of\u00a0 Microbiology, Vinayaka Mission\u2019s Medical College\u00a0 Karaikal,Tamil Nadu, for guiding us in our research work. We are grateful to Biogen Care Research Centre ,Chennai for the technical help and support.<\/p>\n

Conflicts of Interest<\/strong><\/p>\n

None<\/p>\n

Sources of funding<\/strong><\/p>\n

None<\/p>\n

References<\/strong><\/p>\n

    \n
  1. Murray BE . The life and times of Enterococcus<\/em>. Clin Microbiol Rev., 1990;3: 46-65.
    \nCrossRef<\/a><\/li>\n
  2. Hollenbeck BL, Rice LB . Intrinsic and acquired resistance mechanisms in Enterococcus<\/em>.Virulence journal., 2012; 3: 421-433.
    \n    CrossRef<\/a><\/li>\n
  3. Chow JW. Aminoglycoside resistance in Enterococci<\/em>. Clin Infect Dis., 2000; 31: 586-9.
    \n    CrossRef<\/a><\/li>\n
  4. Marothi YA,.Agnihotri H,.Dubey D. Enterococcal resistance \u2013An overview. Indian J Med Microbiol.,2005;23:214-93.
    \n    CrossRef<\/a><\/li>\n
  5. Arias CA, Contreras GA, Murray BE. Management of multidrug-resistant \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0enterococcal infections. Clin Microbiol Infect., 2010; 6 : 555\u2013562.
    \n    CrossRef<\/a><\/li>\n
  6. Arsene S, Leclercq R . Role of a qnr-Like Gene in the Intrinsic Resistance of Enterococcus faecalis <\/em>to Fluoroquinolones. Antimicrob Agents Chemother., 2007;51:3254\u2013325.<\/li>\n
  7. Garrido AM , Galvez A , Pulido RP .Antimicrobial resistance in Enterococci<\/em>. J Infect Dis Ther.,2014;2:1-7.
    \n    CrossRef<\/a><\/li>\n
  8. Smith PF, Birmingham MC, Noskin GA, Meagher AK, Forrest A, Rayner AR, et al<\/em> . Safety, efficacy and pharmacokinetics of linezolid for treatment of resistant Gram-positive infections in cancer patients with neutropenia. Ann Oncol., 2003; 14:795-801.
    \n    CrossRef<\/a><\/li>\n
  9. Hindler JA, Wong-Beringer A, Charlton CL, Miller SA, Kelesidis T, Carvalho M, et al<\/em> . In Vitro Activity of Daptomycin in Combination with \u03b2-Lactams, Gentamicin, Rifampin and Tigecycline against Daptomycin- Non susceptible Enterococci<\/em>. Antimicrob Agents Chemother., 2015;59: 4279-4287.<\/li>\n
  10. Clinical and Laboratory Standard Institute (CLSI). Performance standards for antimicrobial susceptibility testing 10th ed. Wayne USA. CLSI, 2015.<\/li>\n
  11. Clinical and Laboratory Standard Institute (CLSI). Performance standards for antimicrobial susceptibility testing 26th ed. Wayne USA. CLSI, 2016
    \n    CrossRef<\/a><\/li>\n
  12. Dutka-Malen S, Evers S., Courvalin P, \u201cDetection of glycopeptides resistance genotypes and identification to the species level of clinically relevant Enterococci<\/em> by PCR,\u201d J Clin Microbiol, 1995; 33 :24-27
    \n    CrossRef<\/a><\/li>\n
  13. Van Den Braak N, Goessens W , Van Belkum A , Verbrugh HA , Endtz HP. Accuracy of the VITEK 2 system to detect glycopeptides resistance in Enterococci<\/em>.J Clin Microbiol, 2001 ;39 : 351-353.
    \n    CrossRef<\/a><\/li>\n
  14. Facklam RR , Collins MD. Identification of enterococcal species isolated from human infections by a conventional test scheme.J Clin Microbiol, 1989; 27 :731-4.
    \n    CrossRef<\/a><\/li>\n
  15. Jain S, Kumar A, Kashyap B , Kaur IR . Clinico-epidemiological profile and high-level aminoglycoside resistance in enterococcal septicaemia from a tertiary care hospital in east Delhi. Int J Appl Basic Med Res., 2011;1: 80-83.<\/li>\n
  16. Gupta V, Singhla N. Speciation and Antimicrobial susceptibility pattern of Enterococci<\/em> from a tertiary care centre of North India. J Clin Diagn Res., 2007; 1 : 385-389.<\/li>\n
  17. Triveda. A study of\u00a0 Antimicrobial Resistance Pattern\u00a0 Of\u00a0 Multidrug -Resistant Enterococci<\/em> Isolated From Clinical Specimen. Int\u00a0 J\u00a0 Recent Sci Res., 2016; 7 : 12585-12588 .
    \n    CrossRef<\/a><\/li>\n
  18. Sauvage E, Keriff F, Fonze E, Herman R, Schoot B, Marquette JP, et al<\/em> . The 4 A 0 <\/sup>crystal structure of the penicillin \u2013resistant penicillin binding protein PBP 5 fm from Enterococcus<\/em> faecium<\/em> in complex with benzyl penicillin. Cell Mol Life Sci., 2002;59:1223-1232.
    \n    CrossRef<\/a><\/li>\n
  19. Sivasankari S, Somasunder VM, Senthamarai S, Anitha C, Kumudhavathi MS, Kumar S, et al<\/em>., Detection of High Level Aminoglycosides Resistant Enterococci<\/em> In A Tertiary Care Hospital. IOSR\u00a0 Journal Of\u00a0\u00a0 Pharmacy and Biological Science. 2013; 8:53-57.<\/li>\n
  20. Aher CS . Vancomycin resistant Enterococci<\/em>: an emerging threat. Int J Curr Microbiol App Sci., 2014; 3:14-19.
    \n    CrossRef<\/a><\/li>\n
  21. Mendritta DK, Kaur H, Deotale V, Thamke DC, Narang R, Narang P. Status of High level Aminoglycoside resistant Enterococcus<\/em> faecium and Enterococcus faecalis<\/em> in a rural hospital of Central India. Indian J Med Microbiol., 2008; 26:369-71.
    \n    CrossRef<\/a><\/li>\n
  22. Prakash VP, Rao SR, Parija SC. Emergence of unusual species of Enterococci<\/em> causing infections, South India. BMC Infec\u00a0\u00a0 Dis., 2005 ;5:1-8.
    \n    CrossRef<\/a><\/li>\n
  23. Jyothi P , Metri BC, Peerapur BV . High Level Resistance to Aminoglycosides in Urinary Isolates of Enterococci<\/em>. Ann Med Health Sci Res., 2014; 4 :58.
    \n    CrossRef<\/a><\/li>\n
  24. Padmasini E, Padmaraj R ,.Srivani Ramesh S, High Level Aminoglycoside resistance and Distribution of Aminoglycoside Resistant genes among Clinical Isolates of Enterococcus<\/em> species in Chennai,India. The Scientific World Journal 2016: 1-5.
    \n    CrossRef<\/a><\/li>\n
  25. Mittal S, Singla P, \u00a0Deep A, \u00a0Bala K, Sikka R, Garg M, et al<\/em>. Vancomycin and High Level Aminoglycoside Resistance in Enterococcus<\/em> spp in a Tertiary Health Care Centre: A Therapeutic Concern. J Pathogens., 2016:1-5.
    \n    CrossRef<\/a><\/li>\n
  26. Gangurde N , Mane M, Phatale S. Prevalence of Multidrug Resistant Enterococci<\/em> in a Tertiary Care Hospital in India: A Growing Threat. Open J Microbiol., 2014; 4 :11-15.
    \n    CrossRef<\/a><\/li>\n
  27. Zhanel GG, Hoban DJ, Karlowsky JA. Nitrofurantoin is active against Vancomycin resistant Enterococci<\/em>. Antimicrob agents Chemother., 2001;45 :324-326.<\/li>\n
  28. Bose S, Ghosh AK , Barapatre R . Prevalence of Drug Resistance among Enterococcus<\/em> spp Isolated from a tertiary care Hospital. Int J Med Health Sci., 2012; 1 :38-44.
    \n    CrossRef<\/a><\/li>\n
  29. Atray D, Sharma A , Atray M. Prevalence of Enterococci<\/em> and its antibiotic resistance in various clinical samples at tertiary care hospital in Southern Rajasthan India. Int J Res Med Sci., 2016;4 :3413-3416.
    \n    CrossRef<\/a><\/li>\n
  30. Eliopoulos GM. Quinupristin \u2013 Dalfopristin and Linezolid: evidence and opinion. Clin Infect Dis., 2003 ;36:473-478.
    \n    CrossRef<\/a><\/li>\n
  31. Reena G, Sumanta C, Kumkum B, Sujata B. \u00a0Enterococcal Infections and its antimicrobial resistance with special reference to VRE and HLAR in a tertiary care hospital in Eastern India. IOSR\u00a0 Journal of Dental and Medical Sciences., 2014 ;13 \u00a0: 17-22.<\/li>\n
  32. Praharaj I, Sujatha S, Parija SC. Phenotypic and genotypic characterisation of Vancomycin resistant Enterococcus<\/em> isolates from clinical specimens. Indian J Med Res., 2013; 138:549-556.<\/li>\n
  33. Archana Rao K, Deepa \u00a0S , Venkatesha D. Enterococci<\/em> \u2013A journey of a successful pathogen.Int Arch Integ Med., 2014;1:49-57.<\/li>\n
  34. Smith JR, Barber KE , Raut A, Rybaka \u03b2-Lactams Enhance Daptomycin Activity against Vancomycin- Resistant Enterococcus faecalis <\/em>and Enterococcus<\/em> faecium<\/em> in In Vitro Pharmacokinetic\/Pharmacodynamic Models. Antimicrobial Agents and Chemotherapy., 2015,;59:2842-2848.
    \n    CrossRef<\/a><\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

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