Sterility testing isolators

Fig. 23.2 Isolators used for sterility testing. The operator works within the hood which is suspended inside the cubicle the hydrogen peroxide generator which is used to sterilize the isolators is shown in the left foreground. (Courtesy of SmithKline Beecham Pharmaceuticals.)...

There are no smoking guns, establishing linkage between sterility test failure isolates, media fill contaminants and environmental isolates is extremely difficult. 

Sterility testing requires a strict control of microbial contamination challenge from outside the controlled environment, but not of the particulate contamination liberated by the process itself. Hence, a positive-pressure isolator in a controlled environment, using... 

Fig. 1 Flexible-film isolator with half-suit used for sterility testing. (Diagram courtesy of La Calhene.)...

Many isolator applications at the clinical trial scale of manufacturing are based on the same scale of technology used for sterility testing. The aseptic dispensing of pharmaceutical products in hospital pharmacies is also carried out on this scale. Such manufacturing is not carried out on a continuous basis, but in relatively small batches that can be transferred from the isolator with the help of one of the more secure transfer systems. In this type of application, one isolator is being used to dispense a variety of products or several isolators are used for separate tasks. 

In industry, the LFCB is used to conduct small batch sterile filling operations, in the general manipulation and isolation of non-hazardous materials, and in quality assurance/quality control (QA/QC) sterility testing. 

There have been major technological advances in two areas that mitigate some of the limitations of the sterility test. They are the use of isolation chambers for performing the test and the development of new technologies to provide rapid—approaching real time—sterility tests. 

Isolation systems are now a reality in the sterility testing suite and aseptic manufacturing area. The use of properly designed and validated isolators for sterility testing can drastically reduce the chance of obtaining a false-positive result. Moreover, the use of isolators for testing should virtually eliminate the human error factor from the equation of possible failure causes. Isolators, their installation, validation, and use have been discussed at length elsewhere. 

The second supplement to USP 24-NF 19 includes a chapter (<1208>) entitled, Sterility Testing—Validation of Isolator Systems. This new chapter provides guidance for the validation of isolator systems for use in sterility testing of compendial articles. 

The space requirements and the equipment necessary for designing a culture maintenance lab vary so widely, from simple laminar flow hoods to air locked sterile rooms, that only each company can specify the details. The number of rooms and work areas depend upon the number of types of cultures maintained, as well as the variety of techniques for mutation, isolation and testing. Therefore, lab space and equipment might include ... 

Some ISO (see Sect. 35.7.2) standards are appropriate as well, such as EN 14175 Fume cupboards. PIC/S (see Sect. 35.5.5) documents may be helpful such as on Isolators used for aseptic processing and sterility testing (PI 014-3). 

AmB formulations were dispersed in phosphate-buffered saline (PBS) at different concentrations (0.1 lOOpg/mL) and incubated for five minutes at 37°C. Freshly isolated human erythrocytes were then added to a final hematocrit of 2% and incubated at the same temperature for 30 minutes. After centrifugation, the supernatant was removed and the RBC pellet was lysed with sterile water. The hemoglobin remaining in the pellet was estimated from its absorption at 560 nm recorded with a spectrophotometer. The percentage hemolysis was calculated from the difference between the hemoglobin remaining in the test samples and the control incubated with PBS alone. 

Another group of blood tests involves bacteriological techniques. Blood and bone marrow samples are obtained under aseptic precautions and introduced into a variety of artificial culture media, with subsequent isolation and identification of the specific microorganism responsible for the illness. Relative susceptibility of the specific strain of bacteria to the available chemotherapeutic and antibiotic agents may then be determined and the effectiveness of such agents in sterilizing the blood-stream can be determined by further blood cultures. 

---