细菌性角膜溃疡的医院流行病学，诱因和微生物诊断

细菌性角膜溃疡的医院流行病学，诱因和微生物诊断首席医学网2009年04月14日18:30:21Tuesday中华临床医师杂志征稿内科临床新进展研讨班重症与血流动力学大会血液净化技术学习班医学类核心期刊征稿第六届世界中医药大会2009世界高血压大会第四届中国国际白血病急危重病护理交流会IOF亚洲骨质疏松班2009年中国药学大会医学影像学术交流会结直肠肛门外科会议口腔正畸学术会议征稿广东研究生学术论坛

作者：AshokKumarNarsani,ShafiMuhammadJatoi,MaheshKumarLohana,SyedAsherDabir,SiddiqaGul,MahtabAlamKhanzada作者单位：巴基斯坦海德拉巴,Liaquat大学眼科医院眼科

【摘要】　　目的：确定细菌性角膜溃疡的发病诱因，临床和微生物特性。方法：本研究涉及300例（300眼）临床上疑似微生物感染的角膜溃疡患者。通过病史回顾和裂隙灯检查获得病例资料。采用标准技术完成角膜刮片检查。取部分刮片样本加入100g/L的氢氧化钾液后，以及采用革兰氏和吉姆萨染色，再直接在显微镜下观察是否存在真菌、细菌和棘阿米巴。另一部分刮片样本直接接种在血琼脂、麦康基琼脂、巧克力琼脂和萨布罗琼脂表面。通过角膜刮片检查，细菌性角膜溃疡被确诊为化脓性角膜溃疡浸润和表层上皮细胞缺失伴细菌感染。对患者应用抗菌治疗。结果：在随访期间，因丢失而被排除的有60个病例。在剩下的240人中，被确诊为细菌性角膜溃疡的156人（65%），大多数为男性（102眼），年龄分布14～74岁。角膜溃疡位于角膜中央的96人（61.5%），位于外周的60人（38.5%）。溃疡深度<1/3角膜厚度的82人（52.6%）。前房炎症为：Tyndall现象和浮游细胞1+～2+64人。角膜涂片中分离出细菌的有125人（80%），其中69%为革兰氏阳性，39%为革兰氏阴性。革兰氏阴性菌感染患者伴有重症前房炎症（P=0.003）并且深度>2/3角膜厚度（P=0.001）。分离得到的最常见致病微生物为金黄色葡萄球菌。治疗后40%的患者视力恢复到入院时的水平甚至更好，其余60%的患者预后差。结论：细菌性角膜溃疡是一种严重的眼部感染性疾病，对眼部存在视力威胁，在治疗上仍具挑战性。快速分离细菌和眼部抗生素的应用是治疗此类疾病的关键。

【关键词】细菌性角膜炎；植物性外伤；微生物

Abstract　　AIM:Todeterminethepredisposingfactors,clinicalandmicrobialcharacteristicsofbacterialcornealulcer.　　METHODS:Threehundredpatients（300eyes）ofclinicallysuspectedmicrobialcornealulcerwereincludedinthestudy.Datawascollectedthroughhistoryandslitlampexamination.Usingstandardtechniques,cornealscrapingwasperformed.Aportionofeachscrapingwasexaminedbydirectmicroscopyforthepresenceofbacteria,fungiandacanthamoebabyusing100g/LpotassiumhydroxideandalsobyGramandstaining.Anotherportionwasinoculateddirectlyonthesurfaceofsolidmediasuchasbloodagar,MacConkeyagar,chocolateagarandSabouraud'sagar.Abacterialcornealulcerwasdefinedasasuppurativecornealinfiltrateandoverlyingepithelialdefectassociatedwithpresenceofbacteriaoncornealscrapingexaminationandcuredwithantibacterialtherapy.　　RESULTS:Ofthe300patients,sixtywerelostinfollowup,theywereexcludedfromstudy.Oftheremaining240,bacterialcornealulcerwasidentifiedin156（65.0%）patients.Theageofpatientsrangedfrom14to74（meanageof48）years.Majorityofthemweremale（102）.Corneallocalizationoftheulcerswasdistributedascentralin96（61.5%）patientsandperipheralin60（38.5%）patients.Ulcerdepthin82（52.6%）patientswaslessthan1/3ofcornealthickness.In64（41.0%）patients,anteriorchamberinflammationwas1+to2+Tyndalleffectwith1+to2+cellspresent.Bacteriawereisolatedin125（80.0%）patientsfromthecornealsmears.SixtyninepercentofisolatedbacteriawereGramspositive,and39%wereGrams'negative.Gramnegativebacteriawereassociatedwithsevereanteriorchamberinflammation（P=0.003）anddepthmorethan2/3ofcornea（P=0.001）.ThemostfrequentorganismisolatedwasStaphylococcusaureus.Fortypercentofpatientshadgoodvisualoutcomewithvisualacuitysameorbetterthanthelevelatadmission.Amongtheothers60%patients,finaloutcomewaspoor.　　CONCLUSION:Bacterialcornealulcerisaseriousocularinfectiousdiseasethatremainsatherapeuticchallengeandvisionthreateningocularcondition.Rapidisolationofbacteriaandtreatmentwithintensiveocularantibioticsrepresentdecisivestepsinthemanagementofsuchpathologies.　　KEYWORDS:bacterialkeratitis;agriculturetrauma;organism

　　INTRODUCTION

　　Microbialkeratitisisaseriousocularinfectiousdiseasethatcanleadtosignificantvisionlossandophthalmicmorbidity[1].Bacteriasarethemostcommoninfectiveorganismsresponsibleforthismorbidity.Theseverityofcornealinfectiondependsontheunderlyingconditionofthecorneaandpathogenecityoftheinfectingbacteria[2].Itisrareintheabsenceofpredisposingfactors,andhencemostcommonlyassociatedwithoculartraumaorocularsurfacedisease.Howevertheincreasingprevalentwiththeuseofcontactlensesinthegeneralcommunityhasresultedwellestablishedassociationbetweenkeratitisandcontactlens[3].

　　Thespectrumofbacterialkeratitiscanalsobeinfluencedbygeographicandclimaticfactors.Manydifferencesinkeratitisprofilehavebeennotedbetweenpopulationslivinginruralorinurbanareasinwestern,orindevelopingcountries[4].Grampositivebacterialspeciesaremorefrequentlyrecoveredintemperatezones,andGramnegativespeciesintropicclimates.Untreated,infectivekeratitismayleadtoopacificationand,ultimately,toperforationofthecornea.Theassociatedmorbidityistheresultofseveralfactorsandisdirectlyaffectedbydifficultiesinpatientsmanagementbecauseofalackofdiagnosticfacilitiesandappropriatetreatment.Specifictreatmentrequirespromptandaccurateidentificationofcausativemicroorganisms[5].Thisstudyisanefforttoanalyzetheepidemiologicfeatures,predisposingfactorsandthemaincausativeorganismsforbacterialcornealulcerinthispartofAsiatoprovideausefulguideforthepracticingophthalmologists.ThistwoyearsQuasiexperimentalstudy（fromApril2006toMarch2008）ofbacterialcornealulcerwasconductedatLiaquatUniversityEyeHospital,Hyderabad,aTertiaryReferralCenterinSouthernPakistan.

　　MATERIALSANDMETHODS

　　SubjectsPatientsabove15yearsofagepresentingwithsuspectedcornealulcerationandhavingsymptomsofpain,redness,watering,photophobiaanddecreasedvisionwereregisteredforthestudy.Patientswrittenconsentwasobtainedandastandardizedproformawasusedtorecordthedata.Detailedhistoryandexaminationofthepatientswastakenregardingdemographicfeatures,timeofonsetofsymptoms,predisposingfactorsincludingcornealinjuries（agriculture,nonagriculture,foreignbodies）,contactlenswear,keratopathies（duetopreviousherpeticinfection,cornealdystrophyorsurgicalprocedure,asinbullouskeratopathy）,dryeyesyndrome,eyelidabnormalities（blephritis,entropion,ectropion,lagophthalmos,andothers）.VisualacuitywasmeasuredwithSnellenchart.Allpatientsunderwentthroughslitlampexaminationtolocatethesite,sizeanddepthofulcer.Anteriorchamberinflammation,whenpresent,wasscored,accordingtoHoaganandassociates,a0+to4+forTyndalleffectandcells.

　　Aftertheinstillationoflocalanesthetic5g/Lproparacainehydrochloride,cornealscrappingwasobtainedasepticallywithasterileNo.15surgicalbladefromthebaseandedgesofeachulcer.Aportionofeachscrappingwasexaminedmicroscopicallyforthepresenceofbacteria,fungioracanthamoebabyusingGramstaining,100g/Lpotassiumhydroxide（KOH）andGiemsastainingmethods.Anotherportionwasinoculatedontobloodagar,chocolateagar,MacConkeyagar,Sarboraudsagar,brainheartinfusionbrothrespectively,inCshapedstreaksandculturedforthepotentialgrowthof,bacteria,fungioracanthamoeba.Sarboraudsagarslantswereincubatedat28℃whileothersat37℃.Allmediawereculturedforaperiodofsevendaysandobserveddaily.Isolatedbacteriaweretestedbychemicalreactionforidentification.Furtherthebacteriaweretestedfortheirresistanceagainstthefollowingocularantibiotics:cefuraxime,cefazolin,moxifloxacin,gentamycin,tobramycin,ceftazidime,norfloxacin,ofloxacin,levofloxacin,gatifloxacin.TheresistancetoantibioticswasevaluatedwiththestandarddiscdiffusionmethodaccordingtothemodifiedtestrecommendedbytheNCCLS.

　　TreatmentProtocolNinetyfive（61%）patientsweretreatedasanoutpatientsdepartmentbasisand61（39%）patientswerehospitalizedfortreatment.Thedecisiontoadmitpatientsanduseoffortifiedantibioticswereinfluencedbytheseverityofthecornealulcerandpatientscompliance.Thestandardfortifiedtherapyconsistedoftopicalcefuraxime50g/Landfortifiedtobramycin9g/L,whereascommerciallyavailableantibioticsusedweretopicalfluoroquinolones（Moxifloxacin）.Theantibioticeyedrops,administeredalternatelyeveryfifteenminutesduringthefirst4hourstheneveryhourforthenext48hours.Later,dropswereprogressivelytaperedaccordingtotheclinicalresponse.Bottlesoffortifiedantibioticsdropswerefreshlypreparedandcefuraxime,waschangedevery72hours.Thisstandardtreatmentprotocolwasstartedforeverypatientandmodifiedonpatientsresponseandthebacterialsusceptibility.

　　StatisticalAnalysisUnivariateanalysiswasusedtoevaluatethepossibleassociationbetweenbacterialtype,clinicalcharacteristics,riskfactorsandclinicaloutcomes.DatawasanalyzedonSPSSversion10.0.

　　RESULTS

　　GeneralSituationThreehundredpatients（300eyes）wereenrolledwithacornealinfiltrationthatwasclinicallycompatiblewiththediagnosisofbacterialcornealulcerduringthetwoyearsstudyperiod.Ofthese60patientswerelostinfollowup,excludedfromstudy.Oftheremaining240cases,bacterialcornealulcerwasidentifiedin156（65.0%）patients.Amongthese,60（38.5%）patientswereexaminedfirsttimeintheoutpatientsdepartment,whereas96（61.5%）werepreviouslytreatedbygeneralpractitionersandophthalmologistsandwerealreadybeingtreatedwithtopicalantibiotics,corticosteroidsandantifungaleyedrops.Theageofpatientsrangedfrom14to74（meanageof48）years.Majorityofthemweremale102（65.4%）withmaletofemaleratioof1.9∶1（Table1）.Onehundredandtwo（69.2%）patientsbelongedtoruraland48（30.0%）werefromurbanpopulation.Traumawithvegetativematerialwasbyfarthemostcommonriskfactor;thiswasencounteredin46（29.5%）patients.Historyofnonvegetativetraumain16（10.3%）patients（Table2）.In18（11.5%）patients,ocularsurfacedisorderwasobserved,thekeratitiswasinducedbyforeignbodyin24（15.4%）patients.Eleven（7.1%）patientswereaffectedbycontactlenses.Keratopathies（includingherpetic,bullousandpostoperativekeratopathies）werepresentedin17（11.0%）patients.Blephritiswasnotedin8（5.1%）patients.While16（10.3%）patientshadnosignificantpriorhistory.

　　Corneallocalizationoftheulcerswasdistributedasin96（61.5%）patientscentralandin60（38.5%）peripheral.Thediameterofthecornealulcerationwasof12mmin24（15.4%）,34mmin78（50.0%）,56mmin24（15.4%）,78mmin26（16.7%）patients,4（2.6%）patientshadentirecornealinvolvement.Ulcerationdepthwaslessthan1/3conrealthicknessin82（52.6%）,between1/3to2/3in60（38.5%）patientsandover2/3in14（9.0%）patients（Table3）.

　　Anteriorchamberinflammationwasabsentin42（26.9%）patients.A1+to2+Tyndalleffectwith1+to2+cellswaspresentin64（41%）patients,andsevereanteriorchamberinflammation（3+to4+Tyndalleffectandcells,withorwithouthypopyon）waspresentin50（32.1%）patients（Table3）.In125（80%）patients,bacteriawereisolatedfromthecornealsmears（Table4）.SixtyninepercentofisolatedbacteriawereGrampositive,mostofthem75（60%）werestaphylococcusaureus.Gramnegativebacteriawereisolatedin39（31%）patients.Mostofthemwerepseudomonasandyersina.InfectionwithGramnegativeorganismsassociatedwithsevereanteriorchamberinflammation（P=0.003）anddepthmorethan2/3ofcornea（P=0.001）.Allisolatedbacteriaweretestedoncurrentlyused10antibiotics.

　　Onehundredandfourteen（73.1%）patientsweretreatedaccordingtothestandardprotocolbyusingfortifiedantibioticdropsforGrampositiveandGramnegativeorganisms.Theremaining42（26.9%）patientswhodidnotstayathospitalandhadsmallinfiltrationwere,treatedbycommerciallyavailableantibioticfluoroquinolone（Moxifloxacin）.

　　Table1Demographicdataof156patientswithbacterialcornealulcern（略）

　　Table2Frequencyofriskfactorsinbacterialcornealulcern（略）

　　Table3Clinicalfeaturesofcornealulcer（略）

　　Table4Organismsisolatedinbacterialcornealulcers（略）

　　Figure1Preandposttreatmentvisualstatusofpatients（略）

　　ClinicalOutcomeVisualacuityonpresentationrangedfrom6/6tonolightperception.Meanvisualacuitywas2.67（SD1.01）.Fortypercentofpatientshadgoodvisualoutcomewithvisualacuitysameorbetterthanthelevelatadmission（Figure1）.Amongtheothers60%patientsfinaloutcomewaspoor.Complicationsofbacterialcornealulcerwerenotedin45（28.8%）patients.Amongthem,glaucomain11patients,endophthalmitisin3patients,anteriorstaphylomain3patientsandcornealperforation,descmetocele,cataracteachdevelopsin3（4.5%）patients.Whereasonehundredandeleven（71.2%）patientshadnoseverecomplications,exceptscaringatthesiteoflesion.Inourstudystatisticalanalysisrevealedthatpoorvisualoutcomewascorrelatedwithhistoryofocularsurfacedisease（P<0.01）,largesizeandcentrallocalizationsoftheulcer（P<0.01）,anddepthofinfiltratemorethan1/3cornealthickness（P<0.01）.

　　DISCUSSION

　　Cornealinfectionistheleadingcauseofocularmorbidityandblindnessworldwide.Inthepublishedreports,bacterialcornealulcerhasbeenfoundtobe13.0%to29.3%ofallcasesofulcerativecornealulcer[6].

　　Oftheremaining240patientswithinfectivekeratitisfromApril2006toMarch2008presentingatourdepartment,bacterialcornealulcerwasdiagnosedin156（65.0%）eyes.Althoughitisrareintheabsenceofapredisposingfactor.Mostofthecasesofmicrobialkeratitiswereassociatedwithoculartrauma.Inthisstudy86（55.0%）wereassociatedwithvarioustypesofocularinjuries.Vegetativetraumaaccounts46（29.5%）patients.Vajpayeeetalreported77.5%ofcasesofbacterialcornealulceroccurredbytraumainlowincomecountries,wherealargenumberofpopulationwereconcernedtoagriculture.Moreover,theclimateismildandhumid,andmalnutritioniscommon[7].Foreignbodyinducedcornealulcerwasthesecondmostcommon（24cases,15.38%）predisposingfactorinourstudy.Mostofthesepatientshadalsohistoryofforeignbodyremovalbyownorbyotherfamilymembersandfollowedbyselfmedications.

　　Ocularsurfacedisorderssuchasdryeyesyndromeandeyelidpathologiesandkeratopathiesaccounted17.3%ofcases.Bourcieretal[2]reported21%ofcasesofbacterialcornealulcerwerewithocularsurfacedisorder.Contactlensesremainedtheleastcommoncauseofbacterialcornealulcerinourstudy.IncontrastRadfordetalreportedcontactlenseshadgreatlyincreasedtheriskofbacterialkeratitiswhichwasestimatedtobe1015timeshigherwiththeuseofextendedweardisposablecontactlenses.Manyphysiopathologicaleffectsofcontactlenseswearhavebeenreported.Themostimportantofwhichisaninducedhypoxiaandhypercapiniaofthecornea.Inlinewithotherstudies[8,9]males（65.4%）werepredominantinourstudy.Theincreasedriskinmalesinourpopulationwasprobablyduetotheirmoreactiveinvolvementinoutdooractivities,whichsubsequentlyincreasedtheirvulnerabilitytothisblindingdisease.Thedurationfromtheonsetofsymptomstothepresentationatourdepartmentrangedfrom7to105（mean41）days.Thisdelaypresentationtotertiarycentermightbeduetothefactthatthepatientalreadyreceivedthetherapyfromtheirnearestophthalmologistsordoctorandwerereferredwhentheulcersdidnotrespond.Xieetal[7]reportedthefirstvisitof41.0%between16and30days.

　　Inthisstudy,themostcommonsignsonslitlampexaminationwereepithelialdefect,stromalinfiltrateandsuppurationpresentsineverycase,whileanteriorchamberreactionandhypopyonwasobservedin73%ofpatients.ThisisinaccordancewithanotherEuropeanstudy[2].Olderindividualsweremorefrequentlyaffectedinthisstudy,majority（61%）ofpatientswerefifthormoredecades.AgeprofileinourpatientsiscomparabletoSchaeferetalandCohenetalstudy.Ingeneralolderage,delayinreferral,topicalsteroidtreatment,pastocularsurgery,poorvisionatpresentation,largesizeofulcer[10],andcentralanddeepulcerareallmajorriskfactorsforeviscerationandenucleationinpatientswithbacterialcornealulcer.Thesituationinthisstudywasnottoodifferent.

　　Thesuccessrateofbacterialisolationwashighinthepresentstudy,with80%ofsmearpositiveonblood,chocolateandMacConkeyagar.WhileWaxmanetal[11]reported70%ofisolationoforganismonsamemedium.AswithmostpublishedstudiestherewasahighprevalenceofGrampositivebacteriawithstaphylococcusaureusaccountingfor75（60%）ofall125bacterialisolates.OurstudymatchtotheHyderabadstudy.Stephenetalreportedhigherincidenceofstreptococcuspneumonia（20%）inhisstudy.Jayaharetal[12]studyalsoreportedthesame.WhileMaskeetalreportedhigh（27%）incidenceofStaphylococcusepidermidisintheirstudy.Thusetiologyofthecornealulcersvariessignificantlyfromregiontoregion.

　　Thestandardtreatmentofbacterialcornealulcerinmajority114（73.1%）ofourpatientsconsistsoftopicalinstillationoffortifiedantibiotics（cefuraxime50g/Landfortifiedtobramycin9g/L）.Whichhasbeenthe"goldstandard"forthetherapyofbacterialcornealulcer[6].Howevertheuseoffortifiedantibioticswereassociatedwithcomplainofocularirritationorintenseconjunctivalreactionsduringdropinstillation.Thiswasduetothelocalcornealandconjunctivaltoxicitytothefortifieddrops.ThesameissuewasraisedbyCutarellietalin1991.Wealsotreated42（26.9%）patientsbyfluoroquinolones（Moxifloxacin）antibiotics.TheantibacterialactionresultsfrominhibitionoftopoisomeraseII（DNAgyrase）andtopoisomeraseIV.ThisisanewfourthgenerationfluoroquinolonewithabroadspectrumofactivityagainstGrampositive（includingmethicillinresistantStaphylococcusaureusandciprofloxacinresistantStaphylococusaureus）andGramnegativemicroorganisms.Inaddition,itpenetrateswellintheanteriorchamberandremainsfairlystableforatleast12hours[13].Thistreatmentwasadvisedtothosepatientswhodidnotstayathospitalandhadsmallinfiltration.

　　Visualprognosisafterbacterialcornealulcerdependsonthesize,locality,anddepthoftheulcersaswellasontheriskfactors,bacteriaisolated,ageandgeneralhealthofpatient.Inourstudypooroutcomeseeninpatientshavingchronicsurfaceoculardisorder,largesizeofulcers,involvingmorethan2/3ofdepthofthecorneaandpoorvisualacuityatpresentation.Patientpresentedverylateorpreviouslytreatedbytopicalsteroidshasalsopoorendresultinourstudy.　　Onlyfortypercentofpatientshadgoodvisualoutcomewithvisualacuitybetterthanthelevelatadmission.Amongtheothers60%patient,finaloutcomewassameorpoorthantimeofpresentation.

　　CONCLUSION

　　Bacterialcornealulcerisaseriousocularinfectiousdiseasethatremainsatherapeuticchallengeandvisionthreateningocularcondition.Rapidisolationofbacteriaandtreatmentwithintensiveocularantibioticsrepresentdecisivestepsinthemanagementofsuchpathologies.

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