Enterococci: A journey of a successful pathogen

Enterococci: A journey of a successful pathogen ISSN: 2394-0026 (P)Original Research Article ISSN: 2394-0034 (O)Enterococci: A journey of a successful pathogen Archana Rao K1, Deepa S2*, Venkatesha D3 1Department of Microbiology, Mysore Medical College and Research Institute, Karnataka, India2Assistant Professor, Department of Microbiology, Mysore Medical College and Research Institute, Karnataka, India3Professor and Head, Department of Microbiology, Mysore Medical College and Research Institute, Karnataka, India *Corresponding author email: [email protected] to cite this article: Archana Rao K, Deepa S, Venkatesha D. Enterococci: A journey of a successfulpathogen. IAIM, 2014; 1(4): 49-57. Available online at www.iaimjournal.comReceived on: 26-11-2014 Accepted on: 02-12-2014AbstractIntroduction: A dynamic homeostasis is maintained between the host and native bacteria of thegastrointestinal tract in humans, but migration of bacteria from the gut to other organs can lead todisease or death. Enterococci, traditionally viewed as commensal bacteria are now acknowledged tobe organisms capable of causing life-threatening infections in humans, especially in the nosocomialenvironment. The existence of Enterococci in such a dual role is facilitated by its intrinsic andacquired resistance to virtually all antibiotics currently in use.Objective: The present pilot study was taken up to compare the multidrug resistance prevalence incommensal Enterococci and pathogenic Enterococci.Material and methods: A total of 50 commensal Enterococci isolated from stool samples and 50clinical samples yielding Enterococci were taken for the study. Antibiotic susceptibility testing wasdone using Kirby Bauer’s disk diffusion method. Minimum inhibitory concentration of Vancomycinwas tested by using E- strip.Results: Among 50 commensal Enterococci, majority showed resistance to Ampicillin 50 (100%),Erythromycin 38 (76%), Clindamycin 30 (60%), higher level of resistance to high level Gentamycin 14(28%), Linezolid 6 (12%), vancomycin 3 (6%). 23 (46%) isolates showed multi drug resistance(resistance to ≥ 3 categories of antibiotics). Among 50 clinical isolates, majority showed resistance toAmpicillin 50 (100%), Clindamycin 46 (92%), Tetracycline 46 (92%), Erythromycin 41 (82%), Linezolidresistance was seen in 8 (16%) and Vancomycin resistance in 5 (10%) clinical isolates. 48 (96%)showed multi drug resistance.Conclusion: Boundary line between pathogenic and commensal Enterococci is blurred due toexchange of resistant traits. Regular screening of enterococcal isolates for resistance detection shouldInternational Archives of Integrated Medicine, Vol. 1, Issue. 4, December, 2014. Page 49Copy right © 2014, IAIM, All Rights Reserved.

Enterococci: A journey of a successful pathogen ISSN: 2394-0026 (P) ISSN: 2394-0034 (O)be implemented. It is very important to consider infection control measures, screening of health careworkers, surveillance cultures which can control spread of multidrug resistant Enterococci.Key wordsAntibiotic resistance, Commensal Enterococci, Multi drug resistance, Linezolid resistance, Vancomycinresistance.Introduction to invade extra intestinal regions and cause infections [6]. With this background, the presentUntil recently bowel commensals including pilot study was taken up to compare theEnterococci were perceived as bacteria with no multidrug resistance prevalence in commensalharm. For long time, commensal Enterococci Enterococci and pathogenic Enterococci.were frequently ignored when isolated in clinicallaboratory. But recently Enterococci have Material and methodsattracted much attention due to its capability ofcausing variety of infections, especially in The present study was conducted in thehospitalized patients and higher resistance to Department of Microbiology, Mysore Medicalvarious antibiotics has led to understanding the College and Research Institute, Mysore. Thisimportance of identification of Enterococcus [1]. study was cross sectional prospective studyEnterococci have evolved over the past century which included 50 isolates of Enterococci fromfrom being an intestinal commensal organism of stool samples of the patients who attended thelittle clinical significance to becoming the second outpatient departments in our hospital andmost common nosocomial pathogen associated other 50 isolates of Enterococci from variouswith significant morbidity and mortality [2]. clinical samples such as burn wound swabs, ascitic fluids, surgical and non-surgical wounds,Enterococci are frequently used as positive umbilical stumps, abdominal drain fluids,resistance indicator bacteria, because of their synovial fluids and Foley's catheters followed byhigh prevalence in the feces of healthy subsequent urine specimens of the samepopulation and their ability to harbor several patient, (except stool specimens) obtained inresistance determinants [3]. Administration of the Microbiology Department were processedantimicrobial agents affects both targeted for the isolation of Enterococci.pathogenic organisms as well as non-targetcommensals. Thus frequent antimicrobial use Enterococcal isolates were identified accordingcreates a pool of resistant commensal bacteria. to the standard protocols. Antibiogram wasThis contributes to the general increase and done using Kirby Bauer’s disk diffusion test asdissemination of bacterial resistance worldwide per latest Clinical and Laboratory Standardsand can be a source of resistance genes for Institute (CLSI) guidelines. The drug of differentpathogens [4]. groups tested were Ampicillin (10 mcg), Amoxycalv (30 mcg), Erythromycin (15 mcg),Until recently commensal Enterococci Clindamycin (2 mcg), Ciprofloxacin (5 mcg),represented an underappreciated means of Tigecycline (15 mcg), high level Gentamycin (120assessing resistance [5]. But the ability of the mcg), Cotrimaxozole (25 mcg), Tetracycline (30organism to acquire newer traits makes it virulent mcg), Linezolid (15 mcg) and Vancomycin (30International Archives of Integrated Medicine, Vol. 1, Issue. 4, December, 2014. Page 50Copy right © 2014, IAIM, All Rights Reserved.

Enterococci: A journey of a successful pathogen ISSN: 2394-0026 (P) ISSN: 2394-0034 (O)mcg). The isolates which showed resistance to variety of drugs is a major cause of failure ofthree or more than three prototype of drugs treatment of infections worldwide and a seriouswere considered as multi drug resistant concern to animal and public health.Enterococci [7]. The minimum inhibitoryconcentration levels of Vancomycin were In our study, commensal Enterococci havedetermined by E strip as per latest CLSI [8]. shown maximum resistance to Ampicillin 50 (100%), followed by Erythromycin 38 (76%),Results Clindamycin 30 (60%). Another study on commensal Enterococci has reported 100%Total of 100 samples were processed. 50 isolates resistance to Ampicillin, Erythromycin. Sinceof Enterococci obtained from the stool samples Ampicillin is the drug of choice in the treatmentwere considered as commensal Enterococci. The of Enterococcal infections, the relatively highother 50 Enterococci from the clinical samples resistance of isolates in this study to Ampicillin iswere considered as pathogenic Enterococci. of great concern, especially in the case ofAmpicillin showed 50 (100%) resistance in both endocarditis treatment [9]. Though we have notcommensal and pathogen Enterococci. Majority studied the risk factors, previous exposure toof commensal Enterococci showed resistance to Ampicillin and urinary catheterization wereErythromycin 38 (76%), Clindamycin 30 (60%), found to be the major risk factors associatedand Ciprofloxacin 22 (44%) as per Graph - 1. with the emergence of Ampicillin resistanceCommensal Enterococci showed higher level of Enterococci. Bladder catheterization has beenresistance to high level Gentamycin 14 (28%), shown to increase urinary EnterococcalLinezolid 6 (12%), Vancomycin 3 (6%). colonization in patients with Ampicillin-resistant Enterococcal bacteremia and a gastrointestinalAmong pathogen Enterococci, majority showed origin of urinary colonization has been indicatedresistance to Clindamycin 46 (92%), Tetracycline by plasmid analysis [10]. The use of antibiotics,46 (92%), and Erythromycin 41 (82%) as per whether for prophylaxis or chemotherapy, doesGraph - 2. High level Gentamycin showed not only affect the pathogenic bacteria but alsoresistance in 16 (32%), Linezolid in 8 (16%) and the commensal bacteria. This maintains a poolVancomycin 5 (10%) of the isolates. Multi drug of resistant bacteria with a pool of resistanceresistance in commensal Enterococci was as per genes in the population which furtherTable - 1. Multi drug resistance in Pathogen contributes to the general increase andEnterococci was as per Table - 2. Comparison of dissemination of bacterial resistance and can beresistance pattern of various antibiotics in a source of resistance genes for pathogens [11,commensal and pathogenic Enterococci was as 12].per Graph - 3. Bacteremia due to Vancomycin resistantDiscussion Enterococci (VRE) is a significant complication in surgical patients and is associated with mortalityAntimicrobial agents are grossly misused in rates ranging from 33% to 68% [13]. Althoughmany developing countries including India the prevalence of VRE infections in India is muchleading to high selective pressure on lower than in the western world, it has beenmicroorganisms. Today, the emergence of increasing in the past one decade. In our studybacterial strains which display resistance to a of commensal Enterococci isolated from 50 fecal samples, 3 (6%) were found to be VancomycinInternational Archives of Integrated Medicine, Vol. 1, Issue. 4, December, 2014. Page 51Copy right © 2014, IAIM, All Rights Reserved.

Enterococci: A journey of a successful pathogen ISSN: 2394-0026 (P) ISSN: 2394-0034 (O)resistant. These finding mirrors, those of a study feed additives for growth enhancement indone by Vandana KE, where 3 (6.25%) were VRE animals may be associated with the emergence[14]. 5 (10%) were found to Vancomycin of VRE. Enterococci can reach human consumersresistant in pathogen Enterococci which is high via food chain [21]. In countries using avoparcin,compared to other reports from India. a glycopeptide antibiotic, as a growth promoter,Glycopeptide resistance among our isolates is Vancomycin-resistant Enterococci (VRE) arehigh, probably reflecting the increased use of commonly found in the commensal flora of foodVancomycin in our hospital over the past few animals, on meat from these animals and in theyears. This fact highlights the importance of commensal flora of healthy humans despite verystrict enforcement of antibiotic policies coupled limited use of Vancomycin in hospitals [22].with greater adherence to infection controlmeasures to prevent emergence and spread of The emergence of Linezolid resistantantibiotic resistant bacteria. Widespread use of Enterococci is a dangerous fact [23]. In ourvancomycin and extended-spectrum study, Linezolid resistance was 6 (12%) and 8Cephalosporin in hospitals likely contributed to (16%) in commensal and pathogen Enterococcithe emergence and dramatic increase of VRE respectively. Though Linezolid has been used inover the past 20 years [15]. clinical practice for a relatively short period of time, there are already several reports ofThe prevalence of VRE has dramatically Linezolid-resistant Enterococci, which is a matterincreased worldwide [16]. The National of concern. As Linezolid is the final resort,Nosocomial Infection Surveillance (NNIS) system sometimes even for VRE it is recommended toin the USA has revealed a significant increase in do a susceptibility testing of clinically significantthe percentage of invasive nosocomial gram-positive pathogens before startingEnterococcus strains displaying high-level Linezolid therapy so as to shorten the course ofvancomycin resistance [17]. To a larger or lesser Linezolid treatment [24].extent, non-microbiological factors such asantibiotic consumption (particular classes and in In our study, the multi drug resistance ingeneral); “colonization pressure”, commensal and pathogen Enterococci is 46%“understaffing”, compliance with hand hygiene and 96% respectively. The emergence of multi-and other infection control measures also drug resistant Enterococci has lead to a scenarioinfluence the development of VRE [18]. which is almost as bad as the preantibiotic eraNosocomial outbreaks of vancomycin-resistant since many of these multi-drug resistant (MDR)Enterococci (VRE) are thought to occur when a strains have developed resistance to practicallypatient already carrying VRE in his/her bowel all available antibiotics [25].sheds VRE, which are then transmitted by healthcare workers or via the environment to other Community awareness of the issues involved inpatients. This model predicts that interventions antibiotic therapy is poor and this isbased on screening and isolation of VRE- compounded by over the counter drugcolonized patients, improved hand hygiene, and availability and self medication. Variousenhanced hospital cleaning will limit cross- contributing factors other than these includedtransmission [19]. Millions of dollars are spent like the combination of poverty and ignoranceeach year by health care systems trying to making the ground perfect for the developmentcontain antibiotic-resistant bacteria and prevent of resistance. Patient’s pressure, aggressivecross-transmission [20]. The use of antibiotics as marketing by pharmaceutical companies, lack ofInternational Archives of Integrated Medicine, Vol. 1, Issue. 4, December, 2014. Page 52Copy right © 2014, IAIM, All Rights Reserved.

Enterococci: A journey of a successful pathogen ISSN: 2394-0026 (P) ISSN: 2394-0034 (O)uniformity among the physicians to follow Conclusionantibiotic policy, causing the recurrence of thedisease also have added to the practice [26]. Boundary line between pathogenic andEffective control of multiple-drug resistant commensal Enterococci is blurred due toEnterococci will require better understanding of exchange of resistant traits. In our studythe interaction between Enterococci, the multidrug resistant traits are seen in bothhospital environment, and humans, prudent commensal and pathogenic Enterococci withantibiotic use and better contact isolation in various percentages. So it becomes necessary tohospitals and other patient care environments Screen-Isolate-Destroy Enterococci at various[27]. levels. At a minimum, a successful program forAntimicrobial resistance is a natural biological control of multidrug resistant Enterococciphenomenon that often results from antibiotic requires effective surveillance to identifypressure in humans, animals and the colonized and infected patients. Equallywidespread use of disinfectants in farm and important is renewed vigor in the search forhousehold chores. When it gets amplified many additional drugs, accompanied by the evolutiontimes, it results in serious public health concerns of new therapeutic paradigms less vulnerable toand long term shifts in resistance levels [22]. In the cycle of drug introduction and drugessence, the situation is alarming. This emerging resistance.threat has to be tackled at the initial phase itself, Referenceswhich could be done through active surveillanceof antimicrobial resistance in the community. 1. Desai PJ, Pandit D, Mathur M, Gogate A.Education of the professionals and public, Prevalence, identification andaccessibility of microbial investigation and its distribution of various species ofresults to the practitioners to rationalize the enterococci isolated from clinicalchoice of antimicrobial therapy is also required specimens with special reference toto combat this problem. urinary tract infection in catheterizedLast but not the least, co-ordination of the patients. Indian J Med Microbiol., 2001;surveillance of the antibiotic resistance in 19(3): 132-7.human and animal health sectors along with 2. Schouten MA, Hoogkamp-Korstanje JA,regulating the antibiotic use, restriction of Meis JF, Voss A. Prevalence ofantibiotic as growth promoters in animals vancomycin resistant Enterococci inshould be equally considered. Multi-drug Europe. Eur J Clin Microbiol Infect Dis,resistant Enterococci have become a serious 2000; 19: 816-22.threat to public health. Enterococci with raised 3. Byarugaba DK, Kisame R, Olet S. Multi-MIC to penicillin and high level resistance to drug resistance in commensal bacteriaamino glycosides are being reported. Although of food of animal origin in Uganda,the incidence of vancomycin resistance was low, African Journal of Microbiologyits presence is a cause of concern. It is important Research, 2011; 5(12): 1539-48.to maintain regular surveillance of antibiotic 4. Andremont A. Commensal flora maysusceptibilities so that changes in their pattern play a key role in spreading antibioticcan be detected early. resistance. ASM News, 2003; 69: 601-7.International Archives of Integrated Medicine, Vol. 1, Issue. 4, December, 2014. Page 53Copy right © 2014, IAIM, All Rights Reserved.

Enterococci: A journey of a successful pathogen ISSN: 2394-0026 (P)5. Marshall MB, Ochieng D, Stuart L. ISSN: 2394-0034 (O) resistance and the carriage ofCommensals: Underappreciate resoviors tetracycline resistance genes withinof antibiotic resistance. Microbe., 2009; commensal Escherichia coli populations.4: 231-8. J. Appl. Microbiol., 2003; 94: 1087-97.6. Giridhara Upadhyaya PM, Ravikumar KL, 13. Fleenor-Ford A, Hayden MK, WeinsteinUmapathy BL. Review of virulence RA. Vancomycin-resistant Enterococci:factors of enterococcus: An emerging Implication for surgeons. Surgery, 1999;nosocomial pathogen. Indian J Med 125: 121-4.Microbiol., 2009; 27(4): 301-5. 14. Vandana KE, G Varghese, S Krishna, et al.7. Magiorakos AP, Srinivasan A, Carey RB, screening at admission for carrierCarmeli Y, Falagas ME, Giske CG, et al. prevalence of multi-drug resistantMultidrug-resistant, extensively drug- organisms in resource constrainedresistant and pandrug-resistant bacteria: settings. Journal of hospital infection,an international expert proposal for 2010; 76(2): 180-1.interim standard definitions for acquired 15. Donabedian SM, Perri MB, Abdujamilovaresistance. Clin Microbiol Infect., 2012; N, Gordoncillo MJ, Naqvi A, Reyes KC, et18(3): 268-81. al. Characterization of Vancomycin-8. Clinical and laboratory standards Resistant Enterococcus faecium Isolatedinstitute, performance standards for from Swine in Three Michigan Counties.antimicrobial susceptibility testing; J Clin Microbiol, 2010; 48: 41-56.twenty third informational supplement. 16. kalian R, Singh M, Agarwal J. vancomycinCLSI document M100-S23.Wayne, PA: resistant enterococci at a tertiary CareJanuary, 2014. hospital in northern india, International9. MM Salem-Bekhit, IMI Moussa, MM Journal of Pharma and Bio Sciences, Int JMuharram, FK Alanazy, HM Hefni. Pharm Bio Sci, 2013; 4(2): (B) 1090–94.Prevalence and antimicrobial resistance 17. Udo EE, Al-Sweih N, Phillips OA, Chughpattern of multidrug-resistant TD. Species prevalence and antibacterialEnterococci isolated from clinical resistance of Enterococci isolated inspecimens, 2012; 30(1): 44-51 Kuwait hospitals. J Med Microbiol, 2003;10. Fortún J, Coque TM, Martín-Dávila P, 52: 163-8.Moreno L, Cantón R, Loza E, Baquero F, 18. Werner G, Coque TM, Hammerum AM,Moreno S. Risk factors associated with Hope R, Hryniewicz W, Johnson A, et al.ampicillin resistance in patients with Emergence and spread of vancomycinbacteraemia caused by Enterococcus resistance among enterococci in Europe.faecium. J Antimicrob Chemother., Euro Surveill., 2008; 13(47).2002; 50(6): 1003-9. 19. Austin DJ, Bonten MJ, Weinstein RA,11. Abatih EN, Alban L, Ersboll AK, Lo Fo Slaughter S, Anderson RM. Vancomycin-Wong DM. Impact of antimicrobial resistant enterococci in intensive-careusage on the transmission dynamics of hospital settings: Transmissionantimicrobial resistant bacteria among dynamics, persistence, and the impactpigs. J. Theor. Biol., 2009; 256: 561-73. of infection control programs. Proc.12. Blake DP, Humphry RW, Scott KP, Natl. Acad. Sci. U.S.A., 1999; 96: 6908–Hillman K, Fenlon DR, Low JC. Influence 6913.of tetracycline exposure on tetracyclineInternational Archives of Integrated Medicine, Vol. 1, Issue. 4, December, 2014. Page 54Copy right © 2014, IAIM, All Rights Reserved.

Enterococci: A journey of a successful pathogen ISSN: 2394-0026 (P)20. Howden BP, Holt KE, Lam MM, Seemann ISSN: 2394-0034 (O) 24. Aukland C, Teare L, Cook F, KaufmannT, Ballard S, Coombs GW, Tong SY, ME, Warner M, Jones G, et al. linezolidGrayson ML, Johnson PD, Stinear TP. resistant Enterococci: Report of firstGenomic insights to control the isolats in the United Kingdom. Jemergence of vancomycin-resistant Antimicrob Chemother, 2002; 50: 743-6.enterococci. MBio., 2013; 4(4). 25. Praharaj I, Sujatha S, Parija SC,21. Van den Bogaard AE, Stobberingh EE. Phenotypic & genotypic characterizationEpidemiology of resistance to of vancomycin resistant Enterococcusantibiotics: Links between animals and isolates from clinical specimens. Indian Jhumans. Int J Antimicrob Agents., 2000; Med Res., 2013; 138(4): 549-56.14(4): 327-35. 26. Kapil A. The challenge of antibiotic22. Van den Bogaard AE, Stobberingh EE. resistance: Need to contemplate. IndianAntibiotic usage in animals: impact on J Med Res., 2005; 121(2): 83-91.bacterial resistance and public health. 27. Huycke MM, Sahm DF, Gilmore MS.Drugs, 1999; 58: 589-607. Multiple-drug resistant Enterococci: The23. Marra AR, Major Y, Edmond MB. Central nature of the problem and an agendavenous catheter colonization by for the future. Emerg Infect Dis., 1998;linezolid-resistant, vancomycin- 4(2): 239-49.susceptible Enterococcus faecalis. J ClinMicrobiol, 2006; 44: 1915-6.Graph - 1: Drug resistance in commensal Enterococci. Series1 120% 100% 80% 60% 40% 20% 0%International Archives of Integrated Medicine, Vol. 1, Issue. 4, December, 2014. Page 55Copy right © 2014, IAIM, All Rights Reserved.

Enterococci: A journey of a successful pathogen ISSN: 2394-0026 (P) ISSN: 2394-0034 (O)Graph - 2: Drug resistance in pathogen Enterococci. Series1 120% 100% 80% 60% 40% 20% 0%Graph - 3: Comparison of resistance pattern of various antibiotics in commensal and pathogenicEnterococci.120% COMMENSAL100% ENTEROCOCCI 80% PATHOGENIC 60% ENTEROCOCCI 40% 20% 0%International Archives of Integrated Medicine, Vol. 1, Issue. 4, December, 2014. Page 56Copy right © 2014, IAIM, All Rights Reserved.

Enterococci: A journey of a successful pathogen ISSN: 2394-0026 (P)Table – 1: Multi drug resistance in commensal Enterococci. ISSN: 2394-0034 (O)Number of isolates Multi drug resistance23 (46%) Resistance to ≥ 3 categories of antibiotics8(16%) Resistance to ≥ 4 categories of antibioticsTable - 2: Multi drug resistance in pathogen Enterococci.Number of isolates Multi drug resistance48(96%) Resistance to ≥ 3 categories38 (76%) Resistance to ≥ 4 categories24 (48%) Resistance to ≥ 5 categoriesSource of support: Nil Conflict of interest: None declared.International Archives of Integrated Medicine, Vol. 1, Issue. 4, December, 2014. Page 57Copy right © 2014, IAIM, All Rights Reserved.