antibiograma ro
DESCRIPTION
microbiologyTRANSCRIPT
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Antibiograma
DEFINITIE• testarea sensibilitatii unei tulpini bacteriene izolate dintr-un produs patologic fata de diverse antibiotice. • se caracterizeaza:
– capacitatea acestora de a opri dezvoltarea microbiana – da informatii pentru selectarea celui sau celor mai active antibiotice fata de microorganismul testat.
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Antibiograma• Introducerea unui antibiotic in terapie este o mare responsabilitate medicala, cerind respectarea unor conditii bine determinate:
Antibiograma1. Antibiograma se face:
1. dupa stabilirea diagnosticului etiologic, 1. prin izolarea in cultura pura 2. prin identificarea agentului patogen.
In cazuri de extrema urgenta, se poate administra un antibiotic (inainte de efectuarea antibiogramei) dar numai dupa recoltarea produselor patologice.
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2. Tratamentul se realizeaza:1. in functie de rezultatele date de antibiograma, 2. alegand antibioticul cel mai eficace,
1. fata de care bacteria izolata are cea mai mare sensibilitate.
3. Antibiograma trebuie repetata 1. tratamentul cu antibiotice este de durata mai lunga;1. agentul patogen poate sa cistige rezistenta fata de antibioticul utilizat.
Apoi in cursul tratamentului datorita dezechilibrului din populatiile microbiocenozelor, poate sa se produca o infectie supraadaugata cu o bacterie din aceste microbiocenoze.
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• Principiul antibiogramei consta in capacitatea antibioticelor de a impiedica multiplicarea bacteriana, fenomen cunoscut ca efect bacteriostatic.• Unele antibiotice au in anumite concentratii si proprietatea de a omori bacteriile: efect bactericid.
Antibiograma• !!! Orice boala bacteriana va fi tratata numai dupa efectuarea antibiogramei
• Metode:»Dilutiilor »Difuzimetrica»E-test
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Metoda dilutiilor• Dilutii de antibiotic intr-un mediu de cultura favorabil dezvoltarii bacteriilor• Cantitati egale din cultura bacteriana testata• Incubare
– 24h, 370 C
Citire si interpretareMediu de cultura
clar, limpede = fara dezvoltare bacterianatulbure = dezvoltare bacteriana
Se stabileste CMICMI = concentratia minima inhibitorieCea mai mica concentratie de antibiotic care opreste dezvoltarea bacteriana
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METODA DILUTIEI IN TUBURI• Medii de cultura lichide• Acelasi volum de bulion• Dilutii ale unui AB • Volume egale de suspensie cu microorganism de testat• Tub de control cu antibiotic, • incubare peste noapte
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Interpretation• 1. concentratia AB mai mica decat MIC (mg/L)=> lichid turbid=> cresterea bact.nu este impiedicata de catre AB • 2. concentratia = sau mai mare decat MIC => lichidul este clar => cresterea este oprita de catre AB• CMI!!!!
Metoda difuzimetricaKirby-BauerScop• Alegerea celui mai eficient antibiotic Medii de cultura solide (placi Petri)Mueller-Hinton
AB depuse pe placa insamantata difuzeaza in mediul de cultura
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Insamantare in panza
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Tehnica de lucru• Se insamanteaza cultura bacteriana (se prepara in prealabil in mediu lichid de o anumita densitate)• Se insamanteaza “in panza”• Pe suprafata placii se depun AB (rondele/ microcomprimate)• Incubare pentru 24h
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Citire si interpretare• Cu o rigla se masoara diametrul zonei de inhibitie a dezvoltarii bacteriene (exprimat in mm)• Se compara cu datele din tabelele standard• Rezultatele se exprima:
»Sensibil (S)» Intermediar sensibil (IS)»Rezistent (R)
E-TEST• Medii de cultura solide
– Mueller-Hinton• Benzi impregnate cu AB• !!! Citire: locul in care zona de inhibitie intalneste banda = CMI
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• Medii cu sange- pt. streptococi• Lowenstein-Jensen- pt. bacilul TBC• Pt anaerobi
• !!Se pot studia efectele asocierilor de antibiotice