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Short Communication
Ide ntification and me dical importance
of coagulase -ne gative staphylococci spe cie s
University Hospital of Ribeirão Preto (HCFMRP-USP), São Paulo, Brazil
Elaine Cristina Manini Minto Cristiane Barelli Roberto Martinez Ana Lúcia da Costa DariniINTRODUCTION
Sta p hylo c o c c us e p id e rmid is a nd o the r c o a g ula se -ne g a tive sta p hy lo c o c c i (C N S) represent the majo r co mpo nents o f the micro flo ra o f huma n skin a nd muc o sa e . The se micro o rg anisms are co mmo nly iso lated in clinical micro bio lo g y labo rato ries and are prevalent in b lo o d c ulture s a nd intra va sc ula r c a the te rs. Altho ug h in medical practice they are co nsidered to be co ntaminants o f specimens co llected fro m patients, CN S have been acquiring increasing impo rtance in the etio lo g y o f ho spital infectio ns.1 This fact pro bably results fro m the larg e number o f d e b ilita te d a nd immuno sup p re sse d ho spitalized patients, and also fro m the larg e-scale emplo yment o f invasive pro cedures.2 An additio nal pro blem is the resistance o f CN S to multip le a ntimic ro b ia l a g e nts, w hic h va rie s acco rding to species. 1 ,3
Bo th micro bio lo g ists and the medical team have difficulty in disting uishing the true ag ents o f infectio n amo ng iso lated CN S. The system o f species identificatio n, the test o f sensitivity to antimicro bial ag ents and the standardizatio n o f c linic a l-mic ro b io lo g ic a l c rite ria p e rmit the detectio n o f individual cases o f infectio n and o f o utbreaks o f ho spital infectio n caused by CN S.4 ,5
ABSTRACT
A to tal o f 1 2 6 co ag ulase-neg ative staphylo co cci strains (CN S) were iso lated fro m blo o d samples and fro m the intraveno us catheters and cerebro spinal fluid o f 1 0 3 patients admitted to the University Ho spital o f Ribeirão Preto . Staphylo co ccus epidermidis (6 8 .2 %), S.
haemo lyticus (1 1 .1 %) and S. ho minis (3 .2 %) were the mo st frequent species. The last two CN S sho wed g reater resistance to antimicro bial ag ents than S. epidermidis. CN S were the ag ents o f infectio n in 1 0 .7 % o f the patients and the ag ents o f intraveno us catheter co lo nizatio n in 1 8 .4 % o f the cases.
Keyw ords: Co ag ulase-neg ative staphylo co cci. Septicemia. Bacteremia. Ho spital infectio n.
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The o bjective o f the present study was to identify at the species level the CN S iso lated fro m no rma lly no n-c o lo niz e d b o d y fluid s a nd to determine their susc eptib ility to a ntimic ro b ia l ag ents. The micro bio lo g ical data were co rrelated with the clinical data in an attempt to determine the ro le o f CN S in the clinical co ntext.
METHODS
W e evaluated CN S iso lated fro m blo o d c ulture s, intra va sc ula r c a the te rs a nd cerebro spinal fluid (CSF). The materials were c o lle c te d b e twe e n Ma rc h 1 9 9 5 a nd Aug ust 1 9 9 6 fro m patients admitted to the University Ho spital, Faculty o f Medicine o f Ribeirão Preto , University o f São Paulo .
Bacteria iso lated fro m these materials were id e ntifie d a s Sta p hylo c o c c us b y c la ssic a l micro bio lo g ical tests. The differentiatio n o f CN S species was perfo rmed using a tube test fo r free co ag ulase and a slide test fo r bo und co ag ulase (Difco , USA). API 2 0 Staph and ID 3 2 Staph g alleries (Bio Mérieux, France) were also used to id e ntify C N S sp e c ie s, using the fo llo w ing additio nal tests in so me cases: PYR (pyrro lido nyl arylamidase, Difco , USA), o xidase and tests o f resistance to po lymixin and no vo bio cin (Difco , USA).6 Q ua lity c o ntro l wa s pe rfo rme d using standard CN S strains (ATCC, USA). The test o f susceptibility to antimicro bial ag ents was carried o ut by the disk diffusio n metho d (Ceco n, Brazil) o n Müeller-Hinto n ag ar plates.6
The medical reco rds o f the patients were reviewed retro spectively. CN S were co nsidered
to be the cause o f infectio n when the fo llo wing criteria were satisfied: 1 ) patient with fever and o the r a lte ra tio ns sug g e stive o f infe c tio n, 2 ) iso latio n o f CN S fro m two o r mo re cultures o f the same o r o f different clinical specimens which had been co llected separately during the same episo de o f infectio n, and 3 ) no iso latio n o f o ther micro o rg anisms.
RESULTS
A to tal o f 1 2 6 CN S were iso lated fro m 1 0 3 patients, 7 9 .3 % fro m blo o d cultures, 1 8 .3 % fro m intraveno us catheters and 2 .4 % fro m CSF. API 2 0 Staph identified 8 6 species with precisio n, b ut ID 3 2 Sta p h a nd a d d itio na l te sts w e re necessary to identify 4 0 o ther strains. The species ide ntifie d sho we d the fo llo wing distrib utio n: 6 8 .2 % Staphylo co ccus epidermidis, 1 1 .1 % S. haemo lyticus, 3 .2 % S. ho minis, 2 .4 % S. caprae, 2 .4 % S. capitis, 1 .6 % S. chro mo g enes, 1 .6 % S. lug d une nsis a nd 0 . 8 % S. simula ns, S. sapro phyticus and S. sciuri. Three strains (2 .4 %) were identified by ID 3 2 Staph as S. aureus, altho ug h they were co ag ulase neg ative. Fo r 6 o ther CN S (4 .8 %) we did no t reach the precisio n req uired to identify the spec ies. Thus, it wa s po ssible to reco g nize 9 5 % o f the CN S with the c o mme rc ia l syste ms use d , w hic h a re a lso a c c e ssib le to sma ll c linic a l mic ro b io lo g y labo rato ries.
DISCUSSION
C N S a re the mic ro o rg a nisms mo st
Ta ble 1 - Percent sensitivity to a ntimicrobia l a gents by the disk diffusion method for the 3 species most frequently isola ted
Antimicro bial ag ents*
Species n# O X PN AP CF CXM CFO IPM VC TC EI CL CO TT GN TB AM PEP CIP STF S.epidermidis 86 42.2 7.2 9.6 63.8 64.9 57.8 54.2 100 100 79.5 85.4 51.8 79.5 54.2 41.0 90.2 69.1 72.2 30.5 S.haemolyticus 14 40.0 0.0 0.0 40.0 46.7 53.3 60.0 100 100 33.3 53.3 53.3 46.7 26.6 46.7 80.0 46.7 46.7 6.7 S.hominis 4 0.0 0.0 0.0 75.0 25.0 25.0 25.0 100 100 75.0 100 0.0 75.0 50.0 0.0 100 0.0 33.3 0.0 *:O X oxacillin; PN penicillin G; AP ampicillin; CF cepalothin; CXM cefuroxime; CFO cefoxithin; IPM imipenem; VC vancomycin; TC teicoplanin; EI -erythromycin; CL - clindamycin; CO - chloramphenicol; TT - tetracyclin; GN - gentamicin; TB - tobramycin; AM - amikacin; PEP - pefloxacin; CIP - ciproflocacin; SFT - trimetoprim-sulfamethoxazole. #: number of strains
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c o mmo nly iso la te d fro m b lo o d a nd the ir full id e ntific a tio n ha s b e e n re c o mme nd e d .5 , 6 S. epidermidis, S. haemo lyticus and S. ho minis were the species mo st o ften detected, as also o bserved in o the r stud ie s.4 , 5 O f the 8 6 stra ins o f S. epidermidis, 7 were causative agents o f infectio n, and the same o ccurred with 3 / 1 4 (2 1 .4 %) o f the S. ha e mo lytic us stra ins. The d iffe re nc e between these percentag es may sug g est that S. ha e mo lytic us is mo re p a tho g e nic tha n S. epidermidis.
Va nc o myc in a nd teic o pla nin sho wed in vitro a c tivity a g a inst 1 0 0 % o f the CN S. The perc enta g e o f susc eptib ility o f the three mo st c o mmo n sp e c ie s to a mika c in, c lind a myc in, te tra c yc lin a nd e rythro myc in w a s usua lly elevated, permitting the therapeutic use o f these drug s (Table 1 ). The CN S presented intermediate o r lo w se nsitivity to b -la c ta ms a nd o the r antibio tics, especially S. haemo lyticus and S. ho minis. Re sista nc e to multiple a ntimic ro b ia l ag ents is being no ted in ho spital strains o f CN S,3 with the predictio n o f future difficulties in the treatment o f infectio ns caused by S. epidermidis and S. haemo lyticus.
The 1 0 3 c a se s sho w e d the fo llo w ing distributio n acco rding to cause o f ho spitalizatio n: 1 7 (1 6 .5 %) premature newbo rn infants o r infants with o ther co mplicatio ns, 1 6 (1 5 .5 %) patients with AIDS, 1 4 (1 3 .6 %) cases o f bo ne marro w transplantatio n, 1 0 (9 .7 %) patients with cancer, 6 (5 .8 %) patients with multiple trauma, and 4 0 (3 8 .8 %) patients with vario us pro blems, including neuro lo g ical, cardiac and rheumatic diseases, and diabetes mellitus.
In 1 1 (1 0 . 7 % ) p a tie nts, C N S w e re co nsidered to be the agent o f infectio n, pro ducing septicemia in 4 cases, infectio n o f the central nervo us system in 2 and perito nitis in 1 . These pa tients with true CN S infec tio n ha d serio us diseases and had been previo usly submitted to inva sive p ro c e d ure s. A no the r g ro up o f 1 9 patients (1 8 .4 %) presented no infectio n but had b e e n imp la nte d w ith a ve no us c a the te r fo r pa re nte ra l nutritio n a nd/ o r a dministra tio n o f me d ic a tio ns fo r a lo ng p e rio d o f time . The iso la tio n o f C N S w a s a ttrib ute d to the
co lo nizatio n o f the implanted catheter since the same micro o rg anism had been iso lated fro m the blo o d o f patients during the preceding weeks, so me o f the m with multiple po sitive c ulture s. Ba c teremia a nd septic emia induc ed b y CN S ha ve b e e n re p o rte d to o c c ur in p re ma ture newbo rn infants and in patients with neo plasias o r submitted to surg eries o r parenteral nutritio n, and especially in intravascular catheters.2 , 3 In the third and larg est g ro up o f patients there was insufficient evidence to co nsider CN S to be the cause o f infectio n. These were cases o f transito ry b a c te re mia w ith no c o nse q ue nc e s o r o f co ntaminatio n during the co llectio n o f clinical specimens.
In co nclusio n, a sig nificant pro po rtio n o f the CN S iso lated in this tertiary care ho spital w a s the c a use o f ho sp ita l infe c tio n o r o f co lo niz atio n o f the intravascular catheter. The id e ntific a tio n o f the sp e c ie s a nd the te st o f susceptibility to antimicro bial ag ents co ntribute to the understanding o f the ro le o f CN S in the clinical co ntext.
REFERENCES
1. Klo ss WE, Banne rm an TL. Up d ate o n c linic al signific anc e o f
co agulase-negative staphylo co cci. Clin Micro bio l Rev 1994;7:117-40.
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AM, Gó n g o ra DVN. Sig n ific ân c ia c lín ic a, e p id e m io lo g ia e m ic ro b io lo gia d as b ac te re m ias p o r e s tafilo c o c o s c o agulas e -negativo s em Ho spital de Ensino . Rev Ass Med Brasil 1997;43:9-14.
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increasing clinical significance. J Pediatr 1990;116:497-507.
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value o f iso lating co agulase-negative staphylo co cci fro m b lo o d cultures. Clin Infect Dis 1996;22:14-20.
5. Weinstein MP, Mirrett S, van Pelt L, McKinno n M, Zimmer BL, Klo o s
W, Reller LB. Clinical impo rtance o f identifying co agulase-negative staphylo co cci iso lated fro m blo o d cultures: evaluatio n o f Micro Scan rap id an d d rie d o ve rn ig h t Gram - p o s itive p an e ls ve rs u s a co nventio nal reference metho d. J Clin Micro bio l 1998;36:2089-2092.
6. Klo o s WE, Bannerman TL. Staphylo co ccus and Micro co ccus. In:
Murray PR, Baro n EJ, Pfaller MA, Teno ver FC, Yo lken RH. Manual o f
Clinical Micro bio lo gy, 6th ed. ASM Press, Washingto n, 1995, 282-298.
Ela ine Cristina M a nini M into - Bio chemical Pharmacist
Cristia ne Ba relli - Po stg raduate student
Roberto M a rtinez - Asso ciate Pro fesso r, Departamento de Clínica Médica, Faculdade de Medicina de Ribeirão Preto , Universidade de São Paulo , Ribeirão Preto , SP, Brazil
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Sao Paulo Med J/Rev Paul Med 1999; 117(4):175-8.
RESUMO
Fo ram identificadas 1 2 6 amo stras de estafilo co co s co ag ulase neg ativo s (ECN ) iso lado s de amo stras de sang ue, catéter endo veno so e líquido cefalo rraquiano de 1 0 3 pacientes do Ho spital das Clínicas de Ribeirão Preto . Staphylo co ccus. epidermidis (6 8 ,2 %), S. haemo lyticus (1 1 ,1 %) e S. ho minis (3 ,2 %) fo ram as espécies mais freqüentes. As duas espécies de ECN mo straram maio r resistência ao s antimicro biano s do que S. epidermidis. ECN fo ram ag entes de infecção em 1 0 ,7 % do s pacientes e de co lo nização de catéter endo veno so s em 1 8 ,4 % do s caso s.
Ana Lúcia da Costa Da rini - Assistant Pro fesso r, Departamento de Análises Clínicas, To xico ló g icas e Bro mato ló g icas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto , Universidade de São Paulo
Sources of Funding: Research suppo rted by FAPESP nº 9 5 / 3 7 1 5 -0 , CN Pq nº 1 3 2 6 5 1 / 9 7 -1 and CAPES co nvênio DS 0 0 0 8 3 / 9 7 -6
Conflict of interest: N o t declared.
La st received: 1 0 February 1 9 9 9
Accepted: 4 March1 9 9 9
Address for correspondence:
Ana Lúcia da Co sta Darini, Faculdade de Ciências Farmacêuticas de Ribeirão Preto - USP
