106:, 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
322:
257:, 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
36:
294:
310:
27:
185:
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
282:
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.
198:
89:
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
184:
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.
281:
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
131:
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
113:
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
30:
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
84:
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
39:
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
122:
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
321:
97:
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
210:
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
803:
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".
755:
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
201:
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.
189:(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.
889:
152:
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,
273:
methods used in hospital diagnostic laboratories, and the well diffusion, cylinder diffusion and bioautography methods used in drug discovery and development laboratories.
389:
882:
293:
173:
165:
309:
580:"Bioprospecting for antibacterial drugs: a multidisciplinary perspective on natural product source material, bioassay selection and avoidable pitfalls"
875:
496:
Bauer AW, Perry DM, Kirby WM (August 1959). "Single-disk antibiotic-sensitivity testing of staphylococci: An analysis of technique and results".
1368:
119:
31:(disk A). Antibiotics to which a bacterial isolate is partially susceptible will produce an intermediate size zone of inhibition (disk B).
1182:
169:
1421:
1336:
186:
107:
534:
Bauer AW, Kirby WM, Sherris JC, Turck M (April 1966). "Antibiotic susceptibility testing by a standardized single disk method".
1244:
1018:
348:
261:
overnight, usually at a temperature of 35 °C. Plates must be incubated within 15 minutes of applying antibiotic disks.
219:
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
1239:
1202:
1187:
247:
334:
1234:
1127:
628:
Singh SB, Young K, Miesel L (August 2011). "Screening strategies for discovery of antibacterial natural products".
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1283:
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17:
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1040:
932:
907:
1072:
212:
35:
1197:
1192:
1172:
1152:
1122:
269:
Several variations of the disk diffusion method have been developed including the Oxford penicillin cup and
69:
1308:
1207:
912:
254:
1316:
1229:
1265:
899:
578:
Cushnie TP, Cushnie B, EcheverrĂa J, Fowsantear W, Thammawat S, Dodgson JL, Law S, Clow SM (June 2020).
1132:
958:
676:
Wheat PF (July 2001). "History and development of antimicrobial susceptibility testing methodology".
99:
999:
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1035:
329:
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258:
220:
145:
91:
1400:
1047:
829:
785:
716:"Principles of assessing bacterial susceptibility to antibiotics using the agar diffusion method"
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994:
821:
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645:
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436:
1167:
1067:
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509:
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at only 4 mm deep, poured into either 100 mm or 150 mm Petri dishes. The
136:
overexpressing strains) can also be used to identify antibacterial mechanism of action.
26:
1147:
968:
963:
224:
153:
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115:
86:
81:
867:
817:
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953:
833:
789:
611:
240:
103:
1142:
1087:
1062:
243:
73:
657:
1380:
1097:
333:. Each disk is labelled with the antibiotic it contains (e.g. AMC30, 30 ÎĽg
250:
848:"Analysis of bacterial sensitivity to antibiotics by the agar diffusion method"
689:
595:
547:
1356:
1052:
128:
77:
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1137:
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741:
697:
649:
603:
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773:
555:
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1254:
1162:
1102:
1079:
732:
715:
1373:
927:
641:
1212:
149:
23:
Microbiology assay used in diagnostic and drug discovery laboratories
579:
390:"Antimicrobial susceptibility testing: EUCAST disk diffusion method"
197:
1326:
1288:
1157:
358:
270:
196:
34:
25:
847:
871:
480:(Semester project). The Pharmaceutical College Barpali, India.
216:
156:, James G. Vincent, Alfred W. Bauer, William M.M. Kirby,
315:
A close-up look at the results of an agar diffusion test
425:"Comparison of antibiotic discs from different sources"
1349:
1307:
1263:
1113:
1028:
1017:
987:
946:
920:
906:
223:, which is equivalent to approximately 150 million
168:, the Swedish Reference Group for Antibiotics, the
709:
707:
671:
669:
667:
623:
621:
573:
571:
569:
567:
565:
491:
489:
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174:British Society for Antimicrobial Chemotherapy
883:
714:Bonev, B; Hooper, J; Parisot, J (June 2008).
529:
527:
418:
416:
414:
383:
381:
379:
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375:
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58:disc-diffusion antibiotic susceptibility test
8:
474:Antimicrobial properties of aerial part of
246:of a specific organism is collected with a
166:Clinical and Laboratory Standards Institute
1025:
917:
890:
876:
868:
62:disc-diffusion antibiotic sensitivity test
731:
448:
299:Agar diffusion was first used in 1889 by
20:, which is also often called a "KB test".
630:Expert Review of Anti-infective Therapy
369:
289:
536:American Journal of Clinical Pathology
720:Journal of Antimicrobial Chemotherapy
678:Journal of Antimicrobial Chemotherapy
7:
510:10.1001/archinte.1959.00270080034004
423:Brown DF, Kothari D (October 1975).
114:strain of known phenotype (often an
1183:Oxidative/fermentation glucose test
206:Agar plate and inoculum preparation
14:
1309:Antibiotic susceptibility testing
1116:biochemical and immunologic tests
818:10.2174/1574887115666201104155458
806:Reviews on Recent Clinical Trials
187:minimum inhibitory concentrations
144:Agar diffusion was first used by
1337:Minimum inhibitory concentration
1029:Manual testing: basic techniques
320:
308:
292:
148:in 1889 to study the effect of
100:stops the bacteria from growing
1245:Novobiocin susceptibility test
1235:Bacitracin susceptibility test
349:Antibiotic sensitivity testing
170:Deutsches Institut fĂĽr Normung
1:
1128:Amino acid decarboxylase test
498:Archives of Internal Medicine
429:Journal of Clinical Pathology
1240:Optochin susceptibility test
1203:Sulfide indole motility test
1188:Phenylalanine deaminase test
277:Oxford penicillin cup method
221:McFarland turbidity standard
160:, Hans Martin Ericsson, the
16:Not to be confused with the
335:amoxicillin/clavulanic acid
1438:
596:10.1007/s11095-020-02849-1
354:Double-disk diffusion test
231:Inoculation and incubation
15:
1284:Polymerase chain reaction
762:Microbial Drug Resistance
758:Burkholderia pseudomallei
162:World Health Organization
1274:Analytical profile index
690:10.1093/jac/48.suppl_1.1
548:10.1093/ajcp/45.4_ts.493
1422:Microbiology techniques
584:Pharmaceutical Research
388:EUCAST (January 2021).
1208:Triple sugar iron test
255:Gram negative bacteria
202:
54:Kirby–Bauer test
41:
32:
1266:point-of-care testing
947:Cultures by body site
900:clinical microbiology
774:10.1089/mdr.2019.0260
684:(Supplement 1): 1–4.
441:10.1136/jcp.28.10.779
200:
38:
29:
1225:Voges–Proskauer test
1133:Bile solubility test
988:Cultures by organism
921:Isolation techniques
476:Sesbania grandiflora
18:Kleihauer–Betke test
1332:McFarland standards
1322:Disk diffusion test
1317:Beta-lactamase test
1250:Lancefield grouping
1230:X and V factor test
1198:Salt tolerance test
1073:Ziehl–Neelsen stain
1036:Colonial morphology
330:Serratia marcescens
301:Martinus Beijerinck
213:Mueller–Hinton agar
146:Martinus Beijerinck
92:mechanism of action
50:agar diffusion test
48:(also known as the
46:disk diffusion test
1401:Inoculation needle
733:10.1093/jac/dkn090
590:(7): Article 125.
327:An antibiogram of
253:. In the case of
203:
104:kills the bacteria
42:
33:
1409:
1408:
1386:Biosafety cabinet
1345:
1344:
1193:Reverse CAMP test
1013:
1012:
995:Bacterial culture
852:agardiffusion.com
642:10.1586/eri.11.81
472:Sahu, BK (2013).
265:Alternate methods
237:aseptic technique
1429:
1396:Inoculation loop
1294:Rapid strep test
1026:
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129:hydrophilicities
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1412:
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1410:
1405:
1341:
1303:
1259:
1168:Methyl red test
1115:
1114:Manual testing:
1109:
1068:India ink stain
1058:Acid-fast stain
1021:
1009:
983:
959:Genital culture
942:
938:Selective media
910:
902:
896:
866:
856:
854:
846:
845:
841:
802:
801:
797:
754:
753:
749:
726:(6): 1295–301.
713:
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193:Standard method
182:
158:John C. Sherris
142:
125:molecular sizes
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12:
11:
5:
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1264:Automated and
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1200:
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1155:
1150:
1148:Coagulase test
1145:
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1055:
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1032:
1030:
1023:
1019:Identification
1015:
1014:
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1010:
1008:
1007:
1002:
1000:Fungal culture
997:
991:
989:
985:
984:
982:
981:
976:
971:
969:Throat culture
966:
964:Sputum culture
961:
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950:
948:
944:
943:
941:
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935:
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915:
904:
903:
898:Techniques in
897:
895:
894:
887:
880:
872:
865:
864:
839:
812:(2): 206–211.
795:
768:(4): 311–318.
747:
703:
663:
636:(8): 589–613.
617:
561:
542:(4): 493–496.
523:
504:(2): 208–216.
483:
464:
435:(10): 779–83.
410:
397:www.eucast.org
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154:Norman Heatley
141:
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108:broth dilution
87:bioprospecting
82:drug discovery
76:assay used in
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13:
10:
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4:
3:
2:
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1369:Anaerobic jar
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1362:Growth medium
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1299:Monospot test
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1005:Viral culture
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979:Wound culture
977:
975:
974:Urine culture
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962:
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954:Blood culture
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63:
59:
55:
51:
47:
37:
28:
19:
1321:
1173:Nitrite test
1143:Citrate test
1084:Rapid tests
1063:Giemsa stain
933:Streak plate
855:. Retrieved
851:
842:
809:
805:
798:
765:
761:
757:
750:
723:
719:
681:
677:
633:
629:
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583:
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473:
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428:
401:. Retrieved
396:
328:
286:Other images
280:
268:
234:
209:
183:
176:and others.
143:
112:
96:
74:microbiology
65:
61:
57:
53:
49:
45:
43:
1381:Durham tube
1213:Urease test
1022:and testing
40:inhibition.
1357:Agar plate
1153:DNAse test
1053:Gram stain
365:References
78:diagnostic
1391:Incubator
1350:Equipment
1279:MALDI-TOF
1178:ONPG test
1138:CAMP test
1041:Hemolysis
908:Isolation
857:March 16,
834:226257747
790:204029543
612:254932190
403:March 16,
259:incubated
180:Principle
1416:Category
1255:RPR test
1163:KOH test
1123:ALA test
1093:Catalase
1080:Wet prep
1048:Staining
826:33148158
782:31596673
742:18339637
698:11420332
650:21819327
604:32529587
518:13669774
399:. EUCAST
343:See also
227:per mL.
1374:Gas-pak
1088:Oxidase
928:Asepsis
913:culture
556:5325707
478:(Linn.)
459:1214010
248:sterile
244:culture
140:History
72:-based
70:culture
68:) is a
66:KB test
1098:Indole
832:
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696:
658:986144
656:
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450:475859
447:
235:Using
172:, the
164:, the
150:auxins
134:target
1327:Etest
1289:VITEK
1218:rapid
1158:IMViC
830:S2CID
786:S2CID
654:S2CID
608:S2CID
393:(PDF)
359:Etest
271:Etest
241:broth
225:cells
911:and
859:2021
822:PMID
778:PMID
738:PMID
694:PMID
646:PMID
600:PMID
552:PMID
514:PMID
455:PMID
405:2021
251:swab
120:NCTC
116:ATCC
80:and
64:and
44:The
1103:PYR
814:doi
770:doi
760:".
728:doi
686:doi
638:doi
592:doi
544:doi
506:doi
502:104
445:PMC
437:doi
118:or
102:or
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