Test system for the determination of the presence of an antibiotic in a fluid

Abstract

Provided is a test system, a test method and a test kit based on a test medium comprising Bromothymol Blue or a structurally related indicator.

1 . Test system for the determination of the presence of an antibiotic in a fluid comprising a test medium comprising a microorganism, at least one substance that provides a solid state and an indicator suitable for the detection of penicillin G, characterized in that said indicator is a compound having the general formula:  
     
       
         
         
             
             
         
       
       wherein R 1 , R 2 , R 3  and R 4  are independently of each other alkyl, halogen or hydrogen,  
       X=C or S, n=1 if X═C and n=0, 1 or 2 if X═S, and R 5  and R 6  are independently of each other:  
       
         
           
           
               
               
           
         
       
       wherein R 7 , R 8  and R 9  are, independently of each other alkyl, branched alkyl, hydrogen or halogen and R 10  is alkyl or branched alkyl, or salts thereof.  
     
   
   
       2 . Test system according to  claim 1  wherein R 10  is methyl.  
   
   
       3 . Test system according to  claim 2  wherein said indicator is Bromothymol Blue.  
   
   
       4 . Method for the determination of the presence of an antibiotic in a fluid comprising the steps of: 
 a) contacting a sample of said fluid with a test medium comprising a micro-organism, at least one substance that provides a solid state and an indicator;    (b) incubating the microorganism for a period of time to grow the microorganism in case no antibiotic is present in the fluid sample; and    (C) detecting growth or inhibition of growth of the microorganism with the indicator, characterized in that said test system is a test system according to  claim 1 .    
   
   
       5 . Method according to  claim 4  wherein the antibiotic to be determined is a β-lactam antibiotic.  
   
   
       6 . Method according to  claim 4  wherein the fluid in which antibiotics are to be determined is a fluid obtainable from an animal or human body.  
   
   
       7 . Method according to  claim 4  wherein the ratio of the volume of said fluid to the volume of test medium exceeds 0.68:1.  
   
   
       8 . A method according to  claim 4 , wherein the ratio of the volume of liquid sample to the volume of test medium exceeds 20:27 (0.74:1) (v/v), 25:27 (0.93:1) (v/v) or 2:1 (v/v).  
   
   
       9 . A method according to  claim 4 , wherein the volume of liquid sample is greater than the volume of test medium.  
   
   
       10 . Kit suitable for the determination of an antibiotic in a fluid comprising a container partially filled with a test medium comprising a microorganism, a gelling agent and an indicator, characterized in that said indicator is a compound with the general formula (I).  
   
   
       11 . Kit according to  claim 8  further comprising nutrients suitable for allowing the microorganism to grow.  
   
   
       12 . Kit according to  claim 10 , further comprising a thermostatic device, with the aid of which test samples can be kept at a pre-set temperature.  
   
   
       13 . Kit according to  claim 10 , further comprising a data carrier loaded with a computer program suitable for instructing a computer to analyze digital data obtained from a sample-reading device.  
   
   
       14 . Use of a compound having the general formula (I) as indicator in a test system for an antibiotic.  
   
   
       15 . Use according to  claim 14  wherein the antibiotic is a β-lactam antibiotic.