Aseptic containment isolators are safer and more aseptic alternative to biological safety cabinets: A Review.

Closed containment isolators are safer and more aseptic alternative to biological safety cabinets: A Review

 

                                          Dr. Dolores Ascon and Michael H. Bellm

 

Abstract

Compounding Aseptic Isolator (CAI) and Compounding Aseptic Containment Isolator (CACI) are alternative containment cabinets to Biological Safety Cabinets (BSCs) to be used in scientific laboratories. These close isolators provide a better physical barrier to protect the health of laboratory workers, maintain the sterility of experimental materials, and prevent the contamination of the environment. Closed containment cabinets are safer to use in research laboratories to provide a clean work environment, prevent exposure of laboratory personnel, prevent aerosol contamination, avoid pathogenic microorganisms to escape or enter the cabinet, prevent cross-contamination of experiments, and protect the environment.

 

Key words

Compounding aseptic isolators, biological safety cabinets, pathogens, laboratory safety.

 

Introduction

The recent death of a laboratory technician after being infected with Neisseria meningitides raised concerns about laboratory containment equipment to prevent exposure of research workers to pathogenic microorganisms and other hazardous materials (Vitals 2012). Laboratory workers are exposed to a variety of pathogenic microorganisms that may put them at risk of infections, contaminate the environment, and contaminate research materials (Kimman et al 2008). The insertion of Biological Safety Cabinets (BSCs) in laboratories had significantly declined Laboratory-associated infections (LAIs) in occupational workers (Osborne 1999). However, several studies show that the contamination of laboratory workers with infectious microorganisms and other hazardous biological materials is still prevalent when working in BSCs. A survey of UK laboratories between 1994 and 1995 focuses on the gastrointestinal infections acquired by scientific workers; mainly females, young staff, microbiologist, scientific and technical staff (walker 1999). Sinh et al 2009 found that laboratory workers are mostly contaminated with pathogenic microorganisms Brucella, Shigella, Salmonella, Micobacterium tuberculosis, Neisseria meningitides, and bloodborne pathogens Hepatitis B virus, Hepatitis C and HIV. These studies indicate that the contamination of laboratory workers with LAIs can be linked to the use of BSCs with front opening because they insert their hands, arms and objects in the chamber  disturbing the airflow and causing the microorganisms to escape (Barbeito 1976) (Macher and First 1984). 

 

An alternative to BSCs are the compounding isolators that are commonly used to handle compounding sterile drug preparations while protecting the handler from hazardous drugs. The Compounding Aseptic Isolator (CAI) and the Compounding Aseptic Containment Isolator (CACI), know as gloveboxes, are enclosed cabinets that provide workers protection and prevent contamination of the compounding products. Several studies have shown the safety of these isolators by preventing exposure of the handlers to hazardous drugs like the antineoplastic drugs (drugs to treat cancer) and other hazardous drugs that can cause skin rashes, infertility, miscarriages, birth defects leukaemia and cancers (Niosh) (Mason 2005). The study of Crauste-Manciet (2005) corroborates the safety of compounding aseptic isolator (CAI) when working with cytotoxic drugs (Turci 2003). Biological safety cabinets are also used to handle antineoplastic drugs, however many studies show contamination in the room preparation areas, and the administrative areas with these types of drugs (Connor 1999) (Yoshida 2009) (Maeda 2010). The advantage to use compounding isolators like CACIs is guaranty by the closed system and the air that is released through an air exhaust system in the atmosphere in order to prevent inhalation or contact with toxic chemicals, (Larrouturou 1992, Cazin 1999). Taken all together, these studies suggest that closed compounding aseptic isolators provide a high level of safety compared with BCSs, and better protect scientific personal, prevent contamination of experimental materials, and avoid the release of pathogens into work and administrative areas. The purpose of the literature review is to determine the pros and cons of BSCs and compounding aseptic isolators as means of containment barriers to protect laboratory workers, prevent product contamination, and protect the environment. 

 

Biological safety cabinets 

Biological safety cabinets are containment devices that are routinely used for a wide variety of applications in scientific laboratories for the handling of pathogen microorganisms including bacteria, viruses, parasites, prions, fungi, human or animal tissues or cells containing infectious organisms, recombinant DNA, transgenic animals, transgenic plants, human gene transfer/studies, genetically modified microorganisms (GMOs) among others (Macher and First 1984, Osborn 1999, Kimman 2008). Wedum developed the laminar flow biological safety cabinets to safely handle hazardous biological agents and to protect laboratory workers from aerosols which is the primary route for transmitting of infectious agents. The first BSC was a modification of a hood or chemical dry box that was equipped with a UV light to disinfect the interior of the cabinet and a bacterial filter (Reitman 1953, Wedum 1956). In general the BSCs have three primary requirements: “personal protection”, to protect the handler to inhale infections agents, “product protection” to protect the product from contamination from the environment, and to prevent “cross-contamination” of test materials in the cabinet (Huang). There are three classes of BSCs, class I, class II, and class III, the last two use high efficiency particulate air (HEPA) filters in the exhaust and supply system that remove microscopic contaminants from the air (CDC, BMBL) (Kruse 1991). According to laboratory biosafety level, the BSC Class I is suitable for work with low to moderate risk biological biohazards, BSC Class II serves to work with low, moderate and high risk microorganisms, and BSC Class III provides the highest level of safety to handle high risk infectious agents (Table 1 and Table 2). BSCs combine the efficiencies of laminar air flow and high efficiency particulate air (HEPA) filters to give protection to laboratory personnel and the environment from exposure to biohazards (Kruse). 

                   Table 1. Laboratory biosafety levels and containment equipment.

 

                    Biosafety Level 

 

   Containment equipment

 

Biosafety level 1  - BSL 1

  • No pathogenic microorganism.

  • Standard microbiological practice.

  • Open bench top.

  • No special containment required.

 

Biosafety level 1  - BSL 2

  • Moderate-risk microorganisms

  • Trained staff to handle pathogenic agents.

  • Access restricted to the lab.

 

Biosafety level 1  - BSL 3

  • Indigenous or exotic agents that may cause serious disease.

  • Specific training to handle pathogenic and potential lethal microorganisms.

  • Work supervised by principal investigator.

 

Biosafety level 1  - BSL 3

  • Extremely pathogenic life-threatening or fatal disease.

  • Lab staff have specific and thorough training 

 

No containment equipment required.

 

 

 

 

BSC Class I

BSC Class II

 

 

 

BSC Class I

BSC Class II

 

 

 

 

BSC Class III

BSC Class I and BSC Class II can be used with full body positive pressure suit.

 

 

* Centers for Disease Control and Prevention. 2009 Biosafety in Microbiological and Biomedical Laboratories (BMBL) 5th edition.

 

 

 

 

         Table 2. Types of biological safety cabinets and aseptic compounding isolators.

 

      Biological Safety Cabinets (BSC)*

              Levels of protection

 

Aseptic compounding isolators

 

    

BSC Class I  

  • Provide personnel and environmental protection.

  • Low to moderate risk biological agents and biohazards.

  • HEPA filter in exhaust system to protect the environment.

  • Can be used to enclose equipment with potential to generate aerosols.

  • Negative pressure.

 

BSC Class II 

  • Provide personnel, product, and environmental protection.

  • Low to moderate risk biological agent.

  • Four types A1, A2, B1, B2.

  • HEPA filter to trap infectious agents.

  • Negative pressure.

 

BSC Class III

  • High risk biological agent 

  • High level of personal protection.

  • Totally enclosed.

  • HEPA filter to trap infectious agents.

  • Negative pressure.

 

 

Compounding Aseptic Isolators (CAI)

  • Compounding sterile preparations.

  • Totally enclosed aseptic system.

  • Worker protection.

  • Positive air pressure.

  • HEPA filters.

  • Prepare no-hazardous drug compounding.

  • Provide ISO 3 classification.

 

Compounding Aseptic Containment Isolators (CACI)

  • Compounding sterile preparations.

  • Totally enclosed aseptic system.

  • Worker protection.

  • Negative pressure.

  • HEPA filters.

  • Prepare hazardous drug compounding.

  • Provide ISO 5 classification.

 

 

* Centers for Disease Control and Prevention. 2009 Biosafety in Microbiological and Biomedical Laboratories (BMBL) 5th edition.

 

 

 

 

Compounding barrier isolators 

 

During the last 20 years barrier isolators have been developed to protect the health of workers and maintain the sterility of products in the pharmaceutical compounding practice (Tillett 1999). Compounding aseptic isolators are closed cabinets that are used for compounding pharmaceutical ingredients or preparations. The Compounding Aseptic Isolator (CAI) and the Compounding Aseptic Containment Isolator (CACI) are superior work systems when compared to BSCs (mainly class I and II) because they offer safer containment barriers similar to the class III BSCs (Table 1). These isolators are specifically designed for compounding microbial and pharmaceutical materials, and maintain aseptic compounding environment within the isolator throughout the compounding and material transfer processes. Air exchange into the isolator from the surrounding environment occurs only after the air has passed through an HEPA filter (CETA). The aseptic isolators provides a higher level of protection for workers as well as a clean, safe and aseptic environment that is superior to any open front clean air equipment like class I or II BSCs.

 

Limitations of biological safety cabinets

If used correctly, BSCs are capable of shielding workers from the inhalation and contamination of infectious microorganisms and prevent their spread into the laboratory. However, several studies show that infectious microorganisms can escape from the BSC infecting laboratory workers and the environment. Barbeito and Taylor 1968 investigated the safety of BSCs using 3 different closure conditions and 3 air velocities to determine how microorganisms can escape from the BSCs. They found that a human-infection-dose of microorganisms escaped when the glove panel was removed. In addition, the number of microorganisms that escaped increased with a decrease in air velocity, and an increase of the number of laboratory operations resulting in an increase in the number of organisms that escaped. Microorganisms were not detected when the glove panel was attached. Interestingly, when the glove panel was installed without gloves attached, no microorganisms escaped outside the cabinet. The conclusion of this work is that LAIs can be prevented by using closed BCS and with high air flow velocities. Similar results were found by Macher and First 1984 when they studied the effect of air flow rates and operator activity on containment of bacterial aerosols in a BSC Class II. They found that inflow air velocity of 0.50 m/s contained the aerosol better than airflow at 0.38 m/s. Furthermore, it was found that a 25-cm-high work opening was more protective than 20-cm-high opening, which is contrary to the thought that large openings can make microorganisms escape more easily. In addition, the activities of workers in the cabinet like hand and arms moving though the opening resulted in spores escaping outside the cabinet. Surprisingly, these authors also found that working in the rear of the cabinet was less safe than working in the front of the cabinet contrary to recommended practice. This study also showed that when the body of the worker when reaching the rear of the cabinet obstructed the inflow of air and created sufficient turbulence to cause cabinet air to spill out. Similar results were found by Rusnak 2004, who investigated the risk of occupational contamination and found that BSCs failed to prevent illness caused by agents with lower infective doses in high-risk research settings. 

 

Federal and state regulations provide standard guidelines for the safety of laboratory workers. However, it doesn’t prevent accidents do to poor laboratory habits especially among inexperienced laboratory workers. Also, it is not uncommon to observe reluctance or over confidence among researchers or technicians involved in routine laboratory work for several years leading to skipping of important laboratory safety procedures. Due to the construction of the BSCs (specifically Class I and II), it is possible to introduce errors by slightly deviating from the standard operating procedures (SOPs) of microbiological or tissue culture laboratory work. In other words, BSCs (specifically Class I and II) do provide the opportunity for introducing practices that may lead to contamination of research materials, other laboratory equipment and materials while posing possible serious health hazards for the workers (Rusnak, Macher and First). The front opening of BSCs Class I and II may contribute more easily to contamination, for example laboratory coats may not cover the full length of the individual worker’s hands even when wearing hand gloves. The exposed area of the skin not only threatens to contaminate the research materials but poses serious threat to the worker exposing their skin to infectious microorganisms. Therefore, the level of safety on BSCs depends highly on individual workers and their laboratory practices. Also, it depends on the proper use of BCSs and using the appropriate window level, limiting the movement of arms and hands to prevent turbulence which provokes hazardous materials to escape (Macher and First 1984).

 

Advantages of Compounding aseptic containment isolators as an alternative to BSC

In several countries BSCs are still being used for compounding sterile preparation products and antineoplastic drugs (Sessink 2011). However, contamination of this drug was detected in 75% of pharmacy samples and 65% of administration samples areas in cancer treatment areas (Connor 1999). A similar study conducted by Yoshida 2009 and Maeda 2010 found contamination in the entire preparation room contaminated with the drug when working in a BSC. Actually, compounding facilities are replacing BSCs with closed barrier isolators CAI and CACI cabinets because they are safer in preventing exposure of personal involved in drug preparation and product contamination. 

 

The BSCs class I and II pose a more user friendly cabinet compared to compounding isolators, especially when moving products in and out of a CACI which requires the use of a transfer chamber not available on BSCs. However, these few restrictions are not comparable to decontaminating a cabinet, losing several years of research work due to contamination, or the additional serious health hazards to the workers. Since CACI and CAI offer a completely closed working area, the chance of contamination to and from the cabinet reduces to a minimum level. Subsequently, the protection level of the worker increases significantly to prevent exposure to toxic drugs. There is also no chance of touching the bottom sash as hands are inserted inside the isolator through two specifically designed protective holes. This design has been proved to decrease significantly the accidental release of pathogenic microorganisms outside the cabinet (Barbeito and Taylor 1968). Several studies have shown the safety of isolators to prevent contamination of compounding workers to antineoplastic drugs and other hazardous drugs (Mason 2005; Crauste-Manciet 2005; Turci 2003). Peters GF 2007 studied the ability of 5 turbulent and unidirectional-airflow compounding aseptic isolators CAIs to control airborne contamination during compounding sterile preparations and they found that the four unidirectional-airflow CAIs comply with ISO class 5 cleanliness. However, the turbulent airflow CAI failed to achieve ISO class 5. 

 

        Table 3. Advantages and disadvantages of BSC and aseptic compounding isolators.

 

 

 

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Biological Safety Cabinets (BSC)

 

             

 

 

Aseptic compounding isolators

 

  • Use for scientific work.

  • Work low, moderate and high risk pathogens.

  • Build on laminar flow technology.

  • BSC Class I and Class II have front openings.

  • Risk escaping pathogens from front opening.

  • Air flow can be disturbed and cause contamination.

 

 

  • Use for pharmaceutical compounding. 

  • Work highly toxic drugs.

  • Glovebox enclosed cabinets

  • Remove operator from environment.

  • Accesses though transfer chambers.

 

 

Conclusions

 

Compounding isolators CAI and CACI can be used in research laboratories because they offer a more efficient containment of pathogenic microorganism, facilitates the safeguard of laboratory workers, prevents contamination of materials, and provide environmental protection. The advantage in using barrier isolators is that they are closed cabinets, are designed for laminar airflow when the worker reaches to the front or the back of the work area, protects the integrity of the process and protects the laboratory personnel all at the same time. 

 

References

 

 

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