117:, there will be an area around the disk where the bacteria have not grown enough to be visible. This is called a zone of inhibition. The susceptibility of the bacterial isolate to each antibiotic can then be semi-quantified by comparing the size of these zones of inhibition to databases of information on known antibiotic-susceptible, moderately susceptible and resistant bacteria. In this way, it is possible to identify the most appropriate antibiotic for treating a patient's infection. Although the disk diffusion test cannot be used to differentiate bacteriostatic and bactericidal activity, it is less cumbersome than other susceptibility test methods such as
333:
268:, excess liquid is removed from the swab by gently pressing or rotating it against the inside of the tube. The swab is then streaked across a Mueller–Hinton agar plate to form a bacterial lawn. To obtain uniform growth, the agar plate is streaked with the swab in one direction, rotated 120° and streaked again, rotated another 120° and streaked again. Using an antibiotic disk dispenser, disks containing specific antibiotics are then applied to the plate. This must be done within 15 minutes of inoculation. Flame-sterilized forceps are used to gently press each disk onto the agar and ensure it is attached. Plates are then
47:
305:
321:
38:
196:
The concentration of these constituents will be highest next to the disk and will decrease as the distance from the disk increases. If the antibiotic or extract is effective against bacteria at a certain concentration, no colonies will grow where the concentration in the agar is greater than or equal to the effective concentration. This is the zone of inhibition. In general, larger zones of inhibition correlate with lower
293:
are plotted as linear dimensions or squares of distances as a function of the natural logarithm of antibiotic concentration in the disks. The MIC is determined from the zero intercept of a linear regression fit through the data. The intercept itself is the logarithm of the MIC. The slope of the regression line is related to the diffusion coefficient of that particular antibiotic in the agar.
209:
100:
labs, the assay is used to screen biological material (e.g. plant extracts, bacterial fermentation broths) and drug candidates for antibacterial activity. When bioprospecting, the assay can be performed with paired strains of bacteria to achieve dereplication and provisionally identify antibacterial
195:
A pure bacterial culture is suspended in saline, its turbidity is standardized, and it is swabbed uniformly across an agar plate. An antibiotic- or extract-impregnated filter paper disk is then placed on the surface of the agar. The disk constituent(s) diffuse from the filter paper into the agar.
292:
Disks containing increasing antibiotic concentrations are placed on a seeded bacterial lawn on the agar surface and plates are incubated. Zone sizes are measured from the edge of the disk to the end of the clear zone. Interpretation is more complicated in mixed susceptibility populations. These
142:
etc.). Zone of inhibition sizes can be used for the purpose of dereplication though. This is achieved by testing each extract against paired strains of bacteria (e.g. streptomycin-susceptible and -resistant strains to identify streptomycin-containing extracts). Paired strains (e.g. wild type and
124:
In drug discovery labs, the disk diffusion test is performed slightly differently than in diagnostic labs. In this setting, it is not the bacterial strain that must be characterized, but a test extract (e.g. a plant or microbial extract). The agar plate is therefore inoculated with a bacterial
41:
In diagnostic laboratories, the disk diffusion test is used to determine the susceptibility of clinical isolates of bacteria to different antibiotics. An effective antibiotic will produce a large zone of inhibition (disk C), while an ineffective antibiotic may not affect bacterial growth at all
95:
laboratories. In diagnostic labs, the assay is used to determine the susceptibility of bacteria isolated from a patient's infection to clinically approved antibiotics. This allows physicians to prescribe the most appropriate antibiotic treatment. In drug discovery labs, especially
50:
In drug discovery laboratories, the disk diffusion test is used to screen natural product extracts for antibacterial activity. Extracts with antibacterial activity, for example the petroleum ether, chloroform, ethanol and acetone extracts above, will produce a zone of
133:
strain), and disks containing the test extract are applied to the surface. Zone of inhibition sizes cannot be used as a semi-quantitative measure of antibacterial potency because different extracts contain molecules with different diffusion characteristics (different
332:
108:
In diagnostic laboratories, the test is performed by inoculating the surface of an agar plate with bacteria isolated from a patient's infection. Antibiotic-containing paper disks are then applied to the agar and the plate is incubated. If an antibiotic
221:
All aspects of the Kirby–Bauer procedure are standardized to ensure consistent and accurate results. Because of this, a laboratory must adhere to these standards. The media used in Kirby–Bauer testing must be
814:
Kshirsagar MM, Dodamani AS, Vishwakarma P, Mali G, Khobragadec VR, Deokar RN (November 2020). "Comparative assessment of antibacterial efficacy of commercially available different dental gels: An in-vitro study".
766:
Lonsway DR, Elrod MG, Kendrick N, Tiller R, Sullivan MM, Edwards JR, Blaney DD, Karlsson M (April 2020). "Correlation between Etest and reference broth microdilution for antimicrobial susceptibility testing of
212:
Standard Kirby–Bauer testing: White disks containing antibiotics shown on an agar plate of bacteria. Circular zones of poor bacterial growth surround some disks, indicating susceptibility to the antibiotic.
200:(MICs) of antibiotic or extract for that bacterial strain. An exception to this is when molecules of the antibiotic or extract are large or hydrophobic because these diffuse through the agar slowly.
900:
163:
on bacterial growth. However, the method has been developed, refined and standardized by many scientists and scientific organizations over the years including George F. Reddish,
284:
methods used in hospital diagnostic laboratories, and the well diffusion, cylinder diffusion and bioautography methods used in drug discovery and development laboratories.
400:
893:
304:
184:
176:
320:
591:"Bioprospecting for antibacterial drugs: a multidisciplinary perspective on natural product source material, bioassay selection and avoidable pitfalls"
886:
507:
Bauer AW, Perry DM, Kirby WM (August 1959). "Single-disk antibiotic-sensitivity testing of staphylococci: An analysis of technique and results".
1379:
130:
42:(disk A). Antibiotics to which a bacterial isolate is partially susceptible will produce an intermediate size zone of inhibition (disk B).
1193:
180:
1432:
1347:
197:
118:
545:
Bauer AW, Kirby WM, Sherris JC, Turck M (April 1966). "Antibiotic susceptibility testing by a standardized single disk method".
1255:
1029:
359:
272:
overnight, usually at a temperature of 35 °C. Plates must be incubated within 15 minutes of applying antibiotic disks.
230:
level of the agar must be between 7.2 and 7.4. Bacterial inoculum is prepared by diluting a broth culture to match a 0.5
1250:
1213:
1198:
258:
345:
1245:
1138:
639:
Singh SB, Young K, Miesel L (August 2011). "Screening strategies for discovery of antibacterial natural products".
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1294:
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28:
1284:
1051:
943:
918:
1083:
223:
46:
1208:
1203:
1183:
1163:
1133:
280:
Several variations of the disk diffusion method have been developed including the Oxford penicillin cup and
80:
1319:
1218:
923:
265:
1327:
1240:
1276:
910:
589:
Cushnie TP, Cushnie B, EcheverrĂa J, Fowsantear W, Thammawat S, Dodgson JL, Law S, Clow SM (June 2020).
1143:
969:
687:
Wheat PF (July 2001). "History and development of antimicrobial susceptibility testing methodology".
110:
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1046:
340:
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231:
156:
102:
1411:
1058:
840:
796:
727:"Principles of assessing bacterial susceptibility to antibiotics using the agar diffusion method"
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1005:
832:
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465:
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17:
1406:
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447:
1178:
1078:
1068:
948:
168:
520:
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at only 4 mm deep, poured into either 100 mm or 150 mm Petri dishes. The
147:
overexpressing strains) can also be used to identify antibacterial mechanism of action.
37:
1158:
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974:
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164:
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126:
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92:
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1103:
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622:
251:
114:
1153:
1098:
1073:
254:
84:
668:
1391:
1108:
344:. Each disk is labelled with the antibiotic it contains (e.g. AMC30, 30 ÎĽg
261:
859:"Analysis of bacterial sensitivity to antibiotics by the agar diffusion method"
700:
606:
558:
1367:
1063:
139:
88:
1289:
1148:
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708:
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614:
528:
784:
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469:
451:
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1173:
1113:
1090:
743:
726:
1384:
938:
652:
1223:
160:
34:
Microbiology assay used in diagnostic and drug discovery laboratories
590:
401:"Antimicrobial susceptibility testing: EUCAST disk diffusion method"
208:
1337:
1299:
1168:
369:
281:
207:
45:
36:
858:
882:
491:(Semester project). The Pharmaceutical College Barpali, India.
227:
167:, James G. Vincent, Alfred W. Bauer, William M.M. Kirby,
326:
A close-up look at the results of an agar diffusion test
436:"Comparison of antibiotic discs from different sources"
1360:
1318:
1274:
1124:
1039:
1028:
998:
957:
931:
917:
234:, which is equivalent to approximately 150 million
179:, the Swedish Reference Group for Antibiotics, the
720:
718:
682:
680:
678:
634:
632:
584:
582:
580:
578:
576:
502:
500:
498:
185:British Society for Antimicrobial Chemotherapy
894:
725:Bonev, B; Hooper, J; Parisot, J (June 2008).
540:
538:
429:
427:
425:
394:
392:
390:
388:
386:
384:
69:disc-diffusion antibiotic susceptibility test
8:
485:Antimicrobial properties of aerial part of
257:of a specific organism is collected with a
177:Clinical and Laboratory Standards Institute
1036:
928:
901:
887:
879:
73:disc-diffusion antibiotic sensitivity test
742:
459:
310:Agar diffusion was first used in 1889 by
31:, which is also often called a "KB test".
641:Expert Review of Anti-infective Therapy
380:
300:
547:American Journal of Clinical Pathology
731:Journal of Antimicrobial Chemotherapy
689:Journal of Antimicrobial Chemotherapy
7:
521:10.1001/archinte.1959.00270080034004
434:Brown DF, Kothari D (October 1975).
125:strain of known phenotype (often an
1194:Oxidative/fermentation glucose test
217:Agar plate and inoculum preparation
25:
1320:Antibiotic susceptibility testing
1127:biochemical and immunologic tests
829:10.2174/1574887115666201104155458
817:Reviews on Recent Clinical Trials
198:minimum inhibitory concentrations
155:Agar diffusion was first used by
1348:Minimum inhibitory concentration
1040:Manual testing: basic techniques
331:
319:
303:
159:in 1889 to study the effect of
111:stops the bacteria from growing
1256:Novobiocin susceptibility test
1246:Bacitracin susceptibility test
360:Antibiotic sensitivity testing
181:Deutsches Institut fĂĽr Normung
18:Kirby-Bauer antibiotic testing
1:
1139:Amino acid decarboxylase test
509:Archives of Internal Medicine
440:Journal of Clinical Pathology
1251:Optochin susceptibility test
1214:Sulfide indole motility test
1199:Phenylalanine deaminase test
288:Oxford penicillin cup method
232:McFarland turbidity standard
171:, Hans Martin Ericsson, the
27:Not to be confused with the
346:amoxicillin/clavulanic acid
1449:
607:10.1007/s11095-020-02849-1
365:Double-disk diffusion test
242:Inoculation and incubation
26:
1295:Polymerase chain reaction
773:Microbial Drug Resistance
769:Burkholderia pseudomallei
173:World Health Organization
1285:Analytical profile index
701:10.1093/jac/48.suppl_1.1
559:10.1093/ajcp/45.4_ts.493
1433:Microbiology techniques
595:Pharmaceutical Research
399:EUCAST (January 2021).
1219:Triple sugar iron test
266:Gram negative bacteria
213:
65:Kirby–Bauer test
52:
43:
1277:point-of-care testing
958:Cultures by body site
911:clinical microbiology
785:10.1089/mdr.2019.0260
695:(Supplement 1): 1–4.
452:10.1136/jcp.28.10.779
211:
49:
40:
1236:Voges–Proskauer test
1144:Bile solubility test
999:Cultures by organism
932:Isolation techniques
487:Sesbania grandiflora
29:Kleihauer–Betke test
1343:McFarland standards
1333:Disk diffusion test
1328:Beta-lactamase test
1261:Lancefield grouping
1241:X and V factor test
1209:Salt tolerance test
1084:Ziehl–Neelsen stain
1047:Colonial morphology
341:Serratia marcescens
312:Martinus Beijerinck
224:Mueller–Hinton agar
157:Martinus Beijerinck
103:mechanism of action
61:agar diffusion test
59:(also known as the
57:disk diffusion test
1412:Inoculation needle
744:10.1093/jac/dkn090
601:(7): Article 125.
338:An antibiogram of
264:. In the case of
214:
115:kills the bacteria
53:
44:
1420:
1419:
1397:Biosafety cabinet
1356:
1355:
1204:Reverse CAMP test
1024:
1023:
1006:Bacterial culture
863:agardiffusion.com
653:10.1586/eri.11.81
483:Sahu, BK (2013).
276:Alternate methods
248:aseptic technique
16:(Redirected from
1440:
1407:Inoculation loop
1305:Rapid strep test
1037:
929:
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896:
889:
880:
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871:
869:
855:
849:
848:
811:
805:
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763:
757:
756:
746:
722:
713:
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684:
673:
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636:
627:
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586:
571:
570:
542:
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140:hydrophilicities
21:
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1441:
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1437:
1423:
1422:
1421:
1416:
1352:
1314:
1270:
1179:Methyl red test
1126:
1125:Manual testing:
1120:
1079:India ink stain
1069:Acid-fast stain
1032:
1020:
994:
970:Genital culture
953:
949:Selective media
921:
913:
907:
877:
867:
865:
857:
856:
852:
813:
812:
808:
765:
764:
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737:(6): 1295–301.
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204:Standard method
193:
169:John C. Sherris
153:
136:molecular sizes
35:
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15:
12:
11:
5:
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1279:
1275:Automated and
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1211:
1206:
1201:
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1186:
1181:
1176:
1171:
1166:
1161:
1159:Coagulase test
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1136:
1130:
1128:
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1119:
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1117:
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1086:
1081:
1076:
1071:
1066:
1056:
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1054:
1043:
1041:
1034:
1030:Identification
1026:
1025:
1022:
1021:
1019:
1018:
1013:
1011:Fungal culture
1008:
1002:
1000:
996:
995:
993:
992:
987:
982:
980:Throat culture
977:
975:Sputum culture
972:
967:
961:
959:
955:
954:
952:
951:
946:
941:
935:
933:
926:
915:
914:
909:Techniques in
908:
906:
905:
898:
891:
883:
876:
875:
850:
823:(2): 206–211.
806:
779:(4): 311–318.
758:
714:
674:
647:(8): 589–613.
628:
572:
553:(4): 493–496.
534:
515:(2): 208–216.
494:
475:
446:(10): 779–83.
421:
408:www.eucast.org
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165:Norman Heatley
152:
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119:broth dilution
98:bioprospecting
93:drug discovery
87:assay used in
33:
24:
14:
13:
10:
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6:
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2:
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1380:Anaerobic jar
1378:
1374:
1373:Growth medium
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1339:
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1311:
1310:Monospot test
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1038:
1035:
1031:
1027:
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1016:Viral culture
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1009:
1007:
1004:
1003:
1001:
997:
991:
990:Wound culture
988:
986:
985:Urine culture
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981:
978:
976:
973:
971:
968:
966:
965:Blood culture
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945:
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90:
86:
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78:
74:
70:
66:
62:
58:
48:
39:
30:
19:
1332:
1184:Nitrite test
1154:Citrate test
1095:Rapid tests
1074:Giemsa stain
944:Streak plate
866:. Retrieved
862:
853:
820:
816:
809:
776:
772:
768:
761:
734:
730:
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688:
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439:
412:. Retrieved
407:
339:
297:Other images
291:
279:
245:
220:
194:
187:and others.
154:
123:
107:
85:microbiology
76:
72:
68:
64:
60:
56:
54:
1392:Durham tube
1224:Urease test
1033:and testing
51:inhibition.
1368:Agar plate
1164:DNAse test
1064:Gram stain
376:References
89:diagnostic
1402:Incubator
1361:Equipment
1290:MALDI-TOF
1189:ONPG test
1149:CAMP test
1052:Hemolysis
919:Isolation
868:March 16,
845:226257747
801:204029543
623:254932190
414:March 16,
270:incubated
191:Principle
1427:Category
1266:RPR test
1174:KOH test
1134:ALA test
1104:Catalase
1091:Wet prep
1059:Staining
837:33148158
793:31596673
753:18339637
709:11420332
661:21819327
615:32529587
529:13669774
410:. EUCAST
354:See also
238:per mL.
1385:Gas-pak
1099:Oxidase
939:Asepsis
924:culture
567:5325707
489:(Linn.)
470:1214010
259:sterile
255:culture
151:History
83:-based
81:culture
79:) is a
77:KB test
1109:Indole
843:
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669:986144
667:
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458:
246:Using
183:, the
175:, the
161:auxins
145:target
1338:Etest
1300:VITEK
1229:rapid
1169:IMViC
841:S2CID
797:S2CID
665:S2CID
619:S2CID
404:(PDF)
370:Etest
282:Etest
252:broth
236:cells
922:and
870:2021
833:PMID
789:PMID
749:PMID
705:PMID
657:PMID
611:PMID
563:PMID
525:PMID
466:PMID
416:2021
262:swab
131:NCTC
127:ATCC
91:and
75:and
55:The
1114:PYR
825:doi
781:doi
771:".
739:doi
697:doi
649:doi
603:doi
555:doi
517:doi
513:104
456:PMC
448:doi
129:or
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