聽聽聽聽聽聽聽聽聽聽聽聽ANTIBIOTICS—MICROBIAL聽ASSAYS(抗生素的微生物检测)聽
The聽activity聽(potency)聽of聽antibiotics聽may聽be聽demonstrated聽under聽suitable聽
conditions聽by聽their聽inhibitory聽effect聽on聽microorganisms.聽A聽reduction聽in聽
antimicrobial聽activity聽also聽will聽reveal聽subtle聽changes聽not聽demonstrable聽by聽
chemical聽methods.聽Accordingly,聽microbial聽or聽biological聽assays聽remain聽generally聽
the聽standard聽for聽resolving聽doubt聽with聽respect聽to聽possible聽loss聽of聽activity.聽This
聽chapter聽summarizes聽these聽procedures聽for聽the聽antibiotics聽recognized聽in聽this聽
Pharmacopeia聽for聽which聽microbiological聽assay聽remains聽the聽definitive聽method.
聽聽Two聽general聽methods聽are聽employed,聽the聽cylinder-plate聽or聽“plate”聽assay（“板”
法）and聽the聽turbidimetric聽or聽“tube”聽assay（“管”法）.聽The聽first聽depends聽upon聽
diffusion聽of聽the聽antibiotic聽from聽a聽vertical聽cylinder聽through聽a聽solidified聽agar聽
layer聽in聽a聽petri聽dish聽or聽plate聽to聽an聽extent聽such聽that聽growth聽of聽the聽added聽
microorganism聽is聽prevented聽entirely聽in聽a聽circular聽area聽or聽“zone”聽around聽the聽
cylinder聽containing聽a聽solution聽of聽the聽antibiotic.聽The聽turbidimetric聽method聽
depends聽upon聽the聽inhibition聽of聽growth聽of聽a聽microbial聽culture聽in聽a聽uniform聽
solution聽of聽the聽antibiotic聽in聽a聽fluid聽medium聽that聽is聽favorable聽to聽its聽rapid聽
growth聽in聽the聽absence聽of聽the聽antibiotic.
聽聽聽聽聽聽聽聽聽聽聽APPARATUS聽（仪器）
All聽equipment聽is聽to聽be聽thoroughly聽cleaned聽before聽and聽after聽each聽use.聽
Glassware（玻璃仪器）for聽holding聽and聽transferring聽test聽organisms聽is聽sterilized
聽by聽dry聽heat聽or聽by聽steam.
聽聽聽聽聽聽聽聽聽聽Temperature聽Control聽（温度控制）
Thermostatic聽control聽is聽required聽in聽several聽stages聽of聽a聽microbial聽assay,聽when聽
culturing聽a聽microorganism聽and聽preparing聽its聽inoculum,聽and聽during聽incubation聽in聽
plate聽and聽tube聽assays.聽Maintain聽the聽temperature聽of聽assay聽plates聽at聽±0.5聽聽of聽the聽
temperature聽selected.聽Closer聽control聽of聽the聽temperature聽(±0.1聽聽of聽the聽selected聽
temperature)聽is聽imperative聽during聽incubation聽in聽a聽tube聽assay,聽and聽may聽be聽
achieved聽in聽either聽circulated聽air聽or聽water,聽the聽greater聽heat聽capacity聽of聽water聽
lending聽it聽some聽advantage聽over聽circulating聽air.聽
聽聽聽聽聽聽聽聽聽聽聽聽Spectrophotometer（分光光度计）
Measuring聽transmittance聽within聽a聽fairly聽narrow聽frequency聽band聽requires聽a聽
suitable聽spectrophotometer聽in聽which聽the聽wavelength聽of聽the聽light聽source聽can聽be聽
varied聽or聽restricted聽by聽the聽use聽of聽a聽580-nm聽filter聽or聽a聽530-nm聽filter聽for聽
reading聽the聽absorbance聽in聽a聽tube聽assay.聽For聽the聽latter聽purpose,聽the聽instrument聽
may聽be聽arranged聽to聽accept聽the聽tube聽in聽which聽incubation聽takes聽place聽(see聽
Turbidimetric聽Assay聽Receptacles),聽to聽accept聽a聽modified聽cell聽fitted聽with聽a聽drain聽
that聽facilitates聽rapid聽change聽of聽content,聽or聽preferably,聽fixed聽with聽a聽
flow-through聽cell聽for聽a聽continuous聽flow-through聽analysis;聽set聽the聽instrument聽at聽
zero聽absorbance聽with聽clear,聽uninoculated聽broth聽prepared聽as聽specified聽for聽the
聽particular聽antibiotic,聽including聽the聽same聽amount聽of聽test聽solution聽and聽
formaldehyde聽as聽found聽in聽each聽sample.
NOTE—Either聽absorbance聽or聽transmittance聽measurement聽may聽be聽used聽for聽preparing
聽inocula.
聽聽聽聽聽聽聽聽Cylinder-Plate聽Assay聽Receptacles（板法）聽
For聽assay聽plates,聽use聽glass聽or聽plastic聽petri聽dishes聽(approximately聽20聽×聽100聽mm)
聽having聽covers聽of聽suitable聽material.聽For聽assay聽cylinders,聽use聽stainless聽steel聽or
聽porcelain聽cylinders聽with聽the聽following聽dimensions,聽each聽dimension聽having聽a聽
tolerance聽of聽±0.1聽mm:聽outside聽diameter聽8聽mm;聽inside聽diameter聽6聽mm;聽and聽length
聽10聽mm.聽Carefully聽clean聽cylinders聽to聽remove聽all聽residues.聽An聽occasional聽acid聽
bath,聽e.g.,聽with聽about聽2聽N聽nitric聽acid聽or聽with聽chromic聽acid聽(see聽Cleaning聽Glass聽
Apparatus聽á1051帽)聽is聽needed.
聽聽聽聽聽聽聽Turbidimetric聽Assay聽Receptacles（管法）聽
For聽assay聽tubes,聽use聽glass聽or聽plastic聽test聽tubes,聽e.g.,聽16聽×聽125聽mm聽or聽18聽×
聽150聽mm聽that聽are聽relatively聽uniform聽in聽length,聽diameter,聽and聽thickness聽and聽
substantially聽free聽from聽surface聽blemishes聽and聽scratches.聽Tubes聽that聽are聽to聽be聽
placed聽in聽the聽spectrophotometer聽are聽matched聽and聽are聽without聽scratches聽or聽
blemishes.聽Cleanse聽thoroughly聽to聽remove聽all聽antibiotic聽residues聽and聽traces聽of聽
cleaning聽solution,聽and聽sterilize聽tubes聽that聽have聽been聽used聽previously,聽before聽
subsequent聽use.聽
聽聽聽聽聽聽聽聽MEDIA（培养基）聽AND聽DILUENTS（稀释剂）
聽聽聽Media
The聽media聽required聽for聽the聽preparation聽of聽test聽organism聽inocula聽are聽made聽from聽
the聽ingredients聽listed聽herein.聽Minor聽modifications聽of聽the聽individual聽
ingredients,聽or聽reconstituted聽dehydrated聽media,聽may聽be聽substituted,聽provided聽the
聽resulting聽media聽possess聽equal聽or聽better聽growth-promoting聽properties聽and聽give聽a聽
similar聽standard聽curve聽response.
Dissolve聽the聽ingredients聽in聽water聽to聽make聽1聽L,聽and聽adjust聽the聽solutions聽with聽
either聽1聽N聽sodium聽hydroxide聽or聽1聽N聽hydrochloric聽acid聽as聽required,聽so聽that聽after聽
steam聽sterilization聽the聽pH聽is聽as聽specified.
聽聽聽
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