CONS In Blood Culture: Contaminants Or Pathogens? - IJCMAS

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Int.J.Curr.Microbiol.App.Sci (2015) Special Issue-1: 88-94ISSN: 2319-7706 Special Issue-1 (2015) pp. 88-94http://www.ijcmas.comOriginal Research ArticleCONS in blood culture: contaminants or pathogens?Fatima Khan*, Samia Kirmani, Naushaba Siddiqui, Asfia Sultan,Hiba Sami, Md. Mahtab, Meher Rizvi, Abida Khatoon, Indu Shukla and Haris M KhanDepartment of Microbiology, Jawaharlal Nehru Medical College,Aligarh Muslim University, Aligarh, U.P., India*Corresponding ,ContaminantsCONS isolated from blood culture are usually contaminants but are also asignificant cause of bacteremia. False positive blood culture leads to additionallaboratory tests, unnecessary antibiotic use and longer hospitalization of patientsthat increases the patients care costs. This study was done to assess the role ofCONS in blood culture in relation to clinical profile and laboratory indices ofpatients showing blood culture positivity. This study was conducted in theDepartment of Microbiology, JNMCH, Aligarh over a period of 4 months. Allsamples submitted to Enteric lab for blood culture were screened. All isolates wereidentified by standard biochemical techniques and antimicrobial sensitivity wasdetermined by Kirby Bauer disc diffusion method as per CLSI guidelines. Clinicalhistory was taken based on preformed Proforma in all samples tested positive forCONS. A total of 1532 samples were obtained in 4 months for blood culture ofwhich 208 (13.6%) showed growth on culture. CONS were isolated in 23 (11.1%)and S. aureus in 11.6%. CONS were considered true pathogens of blood streaminfections in only 8 patients (34.78%). In vast majority (65.2%), they wereconsidered mere contaminants. Oxacillin resistance was noted in 7 out of 8 positiveisolates while among the 15 contaminants, 13 were oxacillin resistant. All isolateswere uniformly sensitive to vancomycin. CONS are important isolates in bloodculture but they can be contaminants also. Therefore differentiation of CONS intopathogenic and contaminants is important. Careful evaluation should be donebefore instituting therapy to avoid unnecessary use of antibiotics.Introductionuseful in directing appropriate antimicrobialtherapy (Van der Heijden et al., 2011).Contamination of blood cultures with skinora, however, poses a substantial problemin the evaluation and management ofpatients.BecauseCoagulase-negativeBlood stream infections range from selflimiting infections to life threatening sepsisthat requires rapid and aggressiveantimicrobial treatment (Gohel et al., 2014).Blood cultures are necessary to establish thediagnosis of bloodstream infections and are88

Int.J.Curr.Microbiol.App.Sci (2015) Special Issue-1: 88-94Staphylococci (CONS) are the predominantmembers of the skin flora, they commonlycontaminate blood cultures (Berwaldt et al.,1996). CONS have long been regarded asnon-pathogenic but their important role aspathogens and their increasing incidencehave been recognized and studied in recentyears. CONS are by far the most commoncause of bacteremia related to indwellingdevices (Garcia et al., 2004). Most of theseinfections are hospital-acquired, and studiesover the past several years suggest that theyare often caused by strains that aretransmitted among hospitalized patients(Huebner and Goldmann, 1990). Otherimportant infections due to CONS includecentral nervous system shunt infections,native or prosthetic valve endocarditis,urinary tract infections, catheter associatedperitonitis, cerebrospinal fluid shuntinfections in neonates, especially when theyare premature and endophthalmitis. They arealso common opportunistic pathogens inpatients who are immunocompromised(Archer and Climo, 2005). Intravenoustreatment of systemic infections is usuallyrequired because CONS have becomeincreasingly resistant to multiple antibiotics.CONS isolated from blood culture areusually contaminants but are also asignificant cause of bacteremia. CONS stillremain the most common contaminants inblood cultures although there is a relativeincrease of CONS infections includingbloodstream infections in recent years(Souvenir et al., 1998).and how often are they mere blood culturecontaminants? False positive blood cultureleads to additional laboratory tests,unnecessary antibiotic use and longerhospitalization of patients that increases thepatients care costs. This study was done toassess the role of Coagulase NegativeStaphylococcus species in blood streaminfections.Material and MethodsThis study was conducted in the Departmentof Microbiology, JNMCH, Aligarh over aperiod of 4 months from June 2014 toSeptember 2014. Samples were collectedusing strict aseptic precautions andinoculated immediately in BHI broth andwere plated on 5 10% sheep blood agar andteepol lactose agar after 24 and 48 hours ofincubation. The negative result wasfollowed-up by examining the broth dailyand doing a final subculture at seventh day.All isolates were identified by standardbiochemical techniques (Collee et al., 2006).Antimicrobial sensitivity was determined byKirby Bauer disc diffusion method as perCLSI guidelines (2014) for the followingantimicrobials: amikacin (30µg), oxacillin(1µg), clindamycin (2µg), azithromycin(15µg), gentamicin (10µg), ofloxacin (30µg) and vancomycin ical parameters and patientcharacteristics were analyzed on the basis ofa predesigned questionnaire in 23 patientswho had pure growth of Coagulase NegativeStaphylococci in their blood cultures.Essential criteria for classification of CONSas true pathogens included (presence ofthree)Because of their low virulence, they may notevoke sufficient inflammatory response andthus a number of patients with n may not have typical clinicalmanifestations and laboratory indices ofinfection. How often the coagulase negativestaphylococci isolated from blood culturesare true pathogens of bloodstream infections1. Fever 100 C2. TLC 120003. Septic appearance89

Int.J.Curr.Microbiol.App.Sci (2015) Special Issue-1: 88-944. Systolic BP 905. 48 hours of hospital admission6. Presence of any of the risk factors(long-termintravascularcatheterization, immunosuppressedpatients with central lines, peritonealdialysis or hemodialysis patients, andpatients with extensive postsurgicalinfections with CONS (Souvenir etal., 1998).Acinetobacterspecies19(9.1%),Citrobacter species 15(7.2%) (Figure 1).CONS were isolated in 23 (10.6%) cases.CONS are frequently isolated from bloodcultures and are emerging as importantnosocomial pathogen. Most of the patients(95.7%) in whom CONS were isolated wereof paediatric age group. CONS was isolatedin 4.5% of cases in study by Gohel et al.,(2014) and among 4% cases by van derHeijden et al. (2011). Reported isolation ofCONS was 20.16% (Arora and Devi, 2007);33% (Akpaka et al., 2006); 42% (Karlowskyet al., 2004) and 16.5% (Roy et al., 2002).Colonization of body surfaces by CONS andpoorvenepuncturetechniquesmaycontribute to the high prevalence of CONSin blood cultures.Result and DiscussionBlood culture is a routine procedure forinvestigating the cause of fever or suspectedinfection in the majority of hospitalizedpatients. Isolation of a true pathogen fromblood culture is important. For a clinicalmicrobiologist, interpretation of thesignificance of isolated CONS from bloodcultureiscomplex.Gram-positiveorganisms predominate among contaminantsand tend to be multidrug resistant, withmany being susceptible only to vancomycin.In patients predisposed to nosocomial oriatrogenic infection, empiric use ofvancomycin following reports of grampositive cocci in blood cultures is common.Out of 23 patients with CONS isolates intheir blood culture, 15 (65.2%) were malesand remaining 34.8 % were females. Vander Heijden et al. (2011) found 56% of thepatients were males.Ascertaining the clinical significance of anisolate of CONS from blood culture isdifficult. CONS were considered truepathogens of blood stream infections in only8 patients (34.78%) on the basis of criteriadiscussed above. In vast majority (65.2%),they were considered mere contaminants(Figure 2). Bodonaik and Moonah (2006)reported 73.3% CONS isolates in the studyas blood culture contaminants.In the present study, blood culture positivitywas seen in 208 of 1532 (13.6%) caseswhich is quite similar to Gohel et al.,(2014); China and Gupta, (2013); Garg et al.(2007) and Mehta et al. (2005). HoweverKamga et al., (2011); Kavitha et al., (2010)and Roy et al., (2002) noted higher bloodculture positivity in their studies. Lowincidence in our study may be because oursis a tertiary care hospital. Most patients arereferred from nearby villages and hadalready taken treatment before they come tothe hospital.Among the 8 patients considered to haveCONS as true pathogens in their bloodculture fever was present in 7 (87.5%),septic appearance in 5 (62.5%) and raisedTLC in 4 (50%) (Figure 3). Seven out of 8significant CONS isolates were hospitalacquired (Figure 3).The most frequent pathogen isolated fromblood was Klebsiella species 90 (43.3%)followed by S. aureus 24 (11.6%).Pseudomonas species in 20 (9.2%),Oxacillin resistance was noted in 7 out of 8positive isolates while among the 15contaminants, 13 were oxacillin resistant90

Int.J.Curr.Microbiol.App.Sci (2015) Special Issue-1: 88-94(Figure 2). The majority (68.6%) of theCONS isolates were methicillin-resistant instudy by Rahman et al. (2013). The highlevels of resistance to methicillin andempirically applied anti-staphylococcalpenicillins and cephalosporins in CONS arewell documented (Ben Jemaa et al., 2004;Huang et al., 2003; Raad et al., 1998;Cercenado et al., 1996). Multidrugresistance was found among 6 (75%) out of8 significant isolates (Table 1). None of theisolate showed resistance to vancomycin inpresent study (Table 1). Similar findingswere found by Akpaka et al. (2006). Theheavy use of antibiotics like vancomycinmay select for multiple-resistant commensalorganisms such as methicillin resistant S.epidermidis (MRSE). Sensitivity againstcephalosporins is not done as per CLSIguidelines because oxacillin resistant strainsare also resistant to otherlactumantibiotics including cephalosporins.Table.1 Sensitivity pattern of 8 significant CONS mikacinGentamyc- RSRRRRRRRFigure.1 Microorganisms (n 208) isolated from blood culture91

Int.J.Curr.Microbiol.App.Sci (2015) Special Issue-1: 88-94Figure.2 Clinical significance of CONS isolated from blood cultures alongwith their sensitivity to oxacillinFigure.3 Essential criteria noted in significant CONS isolates (n 8)Amikacin and Gentamycin resistance wasfound among 3 (37.5%) significant isolateseach while Clindamycin and azithromycinresistance was found among 6 (75%)significant isolates.attributable to skin contamination. Thepractice of proper venepuncture and handwashing techniques by medical staff arerecommended to circumvent the difficulty ofinterpretingbloodcultures.Carefulevaluation should be done before institutingtherapy to avoid unnecessary use ofantibiotics.Blood culture contamination is problematic;it can lead to unnecessary and costlytreatment. CONS are important isolates inblood culture but they can be contaminantstoo. Therefore differentiation of CONS intopathogenic and contaminants is important.The high prevalence of CONS is mostlyAcknowledgementI wish to take this opportunity to thank myteachers, colleagues and friends for their92

Int.J.Curr.Microbiol.App.Sci (2015) Special Issue-1: 88-94constant support, encouragement and timelysuggestions apart from making the workfeasible for me.pathogens? West Indian Med. J., 55(3):174.Cercenado, E., García-Leoni, M.E., Díaz,M.D., Sanchez-Carrillo, C., Catalan, P.,Bernaldo de Quiros, J.C.L., et al. 1996.Emergence of teicoplanin-resistantcoagulase negative Staphylococci. J.Clin. Microbiol., 34: 1765 8.China, D., Gupta, V. 2013. Bacteriologicalprofile and antimicrobial susceptibilitypattern of blood isolates from a tertiarycare hospital in North India. Int. J.Pharm. Res. Biosci., 2(2): 24 35.Clinical and Laboratory Standards Institute,2014. Performance standards forantimicrobial susceptibility testing:Twentyfourthinformationalsupplement: Approved standards M100S24. Clinical and Laboratory StandardsInstitute, Baltimore, USA. 24.Collee, J.G., Fraser, A.G., Marmion, B.P.,Simmons, Mackey,A. 2006. McCartneypractical medical microbiology. In:Collee, J.G., Miles, R.S., Watt, B.,(Eds). Tests for the identifi cation ofBacteria, 14th edn. Elsevier, New Delhi,India. Pp. 131 49.Garcia, P., Benitez, R., Lam, M., Salinas,A.M., Wirth, H., Espinoza, C., et al.2004.Coagulase-negativeStaphylococci: clinical, microbiologicaland molecular features to predict truebacteraemia. J. Med. Microbiol., 53:67 72.Garg, A., Anupurba, S., Garg, J., Goyal,R.K., Sen, M.R. 2007. Bacteriologicalprofile and antimicrobial resistance ofblood culture isolates from a UniversityHospital. Indian Acad. Clin. Med.,8(2): 139 43.ReferencesAkpaka, P.E., Christian, N., Bodonaik, N.C.,Smikle, M.F. 2006. Epidemiology ofcoagulase-negativeStaphylococciisolated from clinical blood specimensat the University hospital of the WestIndies. West Indian Med. J., 55(3): 17072.Archer, G.L., Climo, M.W. 2005.Staphylococcus epidermidis and othercoagulase negative Staphylococci. In:Mandel, G.L., Bennett, J.E., Dolin R.(Eds.), Principles and practice ofinfectious diseases.Philadelphia.Elsevier Churchill Livingston. Pp.2352 62.Arora, U., Devi, P. 2007. Bacterial profileof blood stream infections and antibioticresistance pattern of isolates. JK. Sci.,9(4): 186 190.Ben Jemaa, Z., Mahjoub, F., Ben HajH mida, Y., Hammami, N., Ben Ayed,M., Hammami, A. 2004. e of clinical blood isolates inSfax-Tunisia (1993 1998). Pathol. Biol.(Paris)., 52: 82 8.Berwaldt, L.A., Geiss, M., Kao, C., Pfaller,M.A. 1996. The positive predictivevalue of isolating coagulase-negativeStaphylococci from blood cultures.Clin. Infect. Dis., 22: 14 20.Bodonaik, N.C., Moonah, S.2006.Coagulase negative Staphylococci frombloodculturescontaminantsor93

Int.J.Curr.Microbiol.App.Sci (2015) Special Issue-1: 88-94Gohel, K., Jojera, A., Soni, S., Gang, S.,Sabnis, R., Desai, M.2014.Bacteriological profile and drugresistance patterns of blood cultureisolates in a tertiary care nephrourologyteaching institute. Bio. Med. Res. Int.,Article ID: 153747, Pp. 1 5.Huang, S.Y., Tang, R.B., Chen, S.J., Chung,R.L.2003.CoagulasenegativeStaphylococcal bacteremia in criticallyill children: Risk factors andantimicrobialsusceptibility.J.Microbiol. Immun. Infect., 36: 51 5.Huebner,J., Goldmann,D.A.1999.Coagulase-negative Staphylococci: roleas pathogens. Ann. Rev. Med., 50: 22336.Kamga, H.L.F., Njunda, A.L., Nde, P.F.2011. Prevalence of septicemia andantibiotic sensitivity pattern of bacterialisolates at the University TeachingHospital, Yaoundae, Cameroon. Afr. J.Clin. Exp. Microbiol., 12(1): 2 8.Karlowsky, J.A., Jones, M.E., Draghi, D.C.,Hornsberry, C., Sahm, D.F., Volturo,G.A.2004.Prevalenceandantimicrobial susceptibilities of bacteriaisolated from blood cultures ofhospitalized patients in the UnitedStates in 2002. Ann. Clin. Microbiol.Antimicrobials, 3(7).Kavitha, P., Sevitha, B., Sunil, R. 2010.Bacteriological profile and antibiogramof blood culture isolates in a pediatriccare unit. J. Lab. Phys., 2: 85 88.Mehta, M., Dutta, P., Gupta, V. 2005.Antimicrobial susceptibility pattern ofblood isolates from a teaching hospitalin North India. Japan. J. Infect. Dis.,58(3): 174 176.Raad, I., Alrahwan, A., Roltson, K. 1998.Staphylococcus epidermidis: Emergingresistance and need for alternativeagents. Clin. Infect. Dis., 26: 1182 7.Rahman, Z.A., Hamzah, H., Hassan, A.,Osman, S., Noor, S.M. 2013. Thesignificance of coagulase-negativeStaphylococci bacteremia in a lowresource setting. J. Infect. Dev. Ctries.,7(6): 448 452.Roy, I., Jain, A., Kumar, M., Agarwal, S.K.2002.Bacteriologyofneonatalsepticemia in a tertiary care hospital ofNorthern India. Indian J. Med.Microbiol., 20: 156 159.Souvenir, D., Anderson, Jr. D.E., Palpant,S., Mroch, H., Askin, S., Anderson J etal. 1998. Blood cultures positive dobacteremia,andtherapy of patients. J. Clin. Microbiol.,36(7): 1923 1926.van der Heijden Y.F., Miller, G., Wright,P.W., Shepherd, B.E., Daniels, T.L.,Talbot, T.R. 2011. Clinical impact ofblood cultures contaminated withcoagulase-negative Staphylococci at anAcademic Medical Center. Infect.Control Hosp. Epidemiol., 32(6): 1 3.94

CONS were isolated in 23 (10.6%) cases. CONS are frequently isolated from blood cultures and are emerging as important nosocomial pathogen. Most of the patients (95.7%) in whom CONS were isolated were of paediatric age group. CONS was isolated in 4.5% of cases in study by Gohel et al., (2014) and among 4% cases by van der Heijden et al. (2011).

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