NewBiphasic Culture System forIsolation ofMycobacteria from BloodofPatients withAcquired ImmuneDeficiency Syndrome

摘要: A new biphasic mediumconsisting ofa7H11agarslant andbrain heart infusion broth liquid phasehasbeen usedforthepast10months attheUniversity ofCalifornia atLosAngeles forisolation ofMycobacterium avium complex fromblood. In12patients whosebloodcultures were grown on thismeditlm, themediantimefor isolation ofM.aviumcomplex was 7days(range 6to15days) compared with21to27days afungal medium and28to38days onroutine blood culture medium. Thesystem hasprovided areliable andrapid way toobtain morphology andrapididentification ofcolonies produced frombloodsamples ofpatients withacquired immunedeficiency syndrome, who areathighrisk forM.aviumcomplex mycobacteremia. Routine bloodcultures areprobably themostimportant single typeofspecimen submitted to themicrobiology laboratory forexamination (6). Promptisolation andaccurateidentification oftheetiological agentsofsepticemia remains oneofthemostpressing functions ofthelaboratory. Although cultures arecommonly usedfortheisolation ofbacteria andfungi, they areseldom ofmycobacteria. a variety ofmediaareavailable forthedetection ofbacteremia (1,3,9,10,17,20)and fungemia (2,16), onlyrecently havesystemsbeenevaluated fortheisolation ofmycobacteria fromblood(7,14).Requests forbloodcultures formycobacteria made because acid-fast bacteria grow slowly andmycobacteremia israre(15). Patients syndrome (AIDS), whooften develop Kaposi's sarcoma,Pneumocystiscarinii pneumonia, andotheropportunistic infections, often alsodevelop disseminated Mycobacteriuim aviuhm complex(MAC)infections before death (5,8,18). Because ofthe highincidence ofdisseminated MAC infection (23), we have designed andtested bloodculture systemforrapid isolationofmycobacteria No efficient systemfor mycobacterial hasbeenavailable (11, 13), butrecently lysis centrifugation technique hasbeenusedtoisolate mycobacteria (7). Thisreport describes our experience witha mediumthat provides rapid andreliable means ofisolating fromthe bloodofpatients withAIDS. Thesolid phaseofthenew systemconsists modified 7H11oleic acidalbumin agar(4,12), andtheliquid phaseisbrain (BHI)broth. Forthepreparationofthesolid phase, 25.0g of7H10agarbase(Difco Laboratories, Detroit, Mich.) mixedwith1.0gofcasein hydrolysate (Sigma Chemical Co.,St.Louis, Mo.), 5.0mlof glycerol (Mallinckrodt Works,St.Louis, and1.0g ofBacto-Agar (Difco) in1 liter ofdistilled water. Themixture melted, dispensed in70to75-mlportions intoflat bloodbottles, andautoclaved at15lb/in2 for15min. Aftersterilization, 5.0ml ofsterile OADC enrichment aseptically addedtoeachbottle. Theresulting solution mixedandallowed tosolidify as slants. Thebrothphaseconsisted of37.0g ofBHI broth(Difco)