Safety in Microbiology: Introduction, Route of Infection, Risk group of Organisms, Biosafety Cabinet and Keynotes

Safety in Microbiology: Introduction, Route of Infection, Risk group of Organisms, Biosafety Cabinet and Keynotes

Introduction of Safety in Microbiology

The knowledge of Safety in Microbiology is mandatory prior to work in a Microbiology laboratory/ research project to save yourself and your surroundings.  Many laboratory workers, researchers, and scientists have suffered illnesses following infection associated with the microbiological investigation of microorganisms or contact with infectious materials. Some of these infections have been fatal. In 1847, Jakob Kolletschka, a close friend of Dr. Ignaz Semmelweis, cut his finger while he’s doing an autopsy and he died of symptoms like those of puerperal fever.  Howard Taylor Ricketts, (born Feb. 9, 1871, Findlay, Ohio, U.S.—died May 3, 1910, Mexico City, Mex.), American pathologist who discovered the causative agent (Rickettsia) and mode of transmission of Rocky Mountain spotted fever and epidemic typhus (known in Mexico, where Ricketts worked for a time and died of typhus, as tabardillo). Dr. Carlo Urbani died while working on finding the cause of Severe Acute Respiratory Syndrome (SARS). Today we call this disease Urbani SARS. Not all the victims were directly involved in the microbiology laboratory in the investigation. Some were working in other laboratories, departments while some were visitors who visited the laboratory.

The most important key points are addressed for Safety in Microbiology are-

The laboratory personnel must keep in the mind. The following points are in order to prevent laboratory-associated infections. The routes by which infections require in the laboratory may be different from natural infection.
It is necessary to know the type of specimens and organisms likely to which may likely contain and while organisms are most hazardous so that precautions while working in the laboratory could be taken accordingly.
Most Hazardous techniques, if possible, should be replaced with safety techniques. Taken full precautions to be protected from such dangerous microbial agents.


Routes and sources of laboratory-associated infection are 

  • Skin
  • Eyes
  • Mouth
  • Respiratory tract
  • Needle prick
  • Cut

Outsides the laboratory: The general public may be infected if the organism is escaped during transportation of patients specimens to laboratory and/or microorganisms from the laboratory, laboratory to reference laboratory both within and outside the country. Another most important source of infection: if the general public comes in contact with infection waste, discarded or effluent materials from the laboratory due to failure of the laboratory to decontaminate such materials properly.

The risk group of Organisms for Safety in Microbiology


Microbial classification is based on their potential impact on humans and the environment is divided into Risk Groups.  WHO has classified  these microorganisms  as follows:

Risk Group 1 (RG1): They belong to the low individual and low community risk. These microorganisms are unlikely to cause disease. e.g. group of food spoilage bacteria, common molds, non-diarrheagenic E.coli and Yeasts.

Risk Group 2 (RG2): They belong to moderate individual risk, limited community risk. These microorganisms are unlikely to be a significant risk to the laboratory personnel or the environment, but exposure may cause infection. e.g. staphylococci, streptococci, enterobacteria (except Salmonella Typhi), clostridia, vibrios, adenoviruses, polioviruses, coxsackieviruses, hepatitis viruses, Toxoplasma, and Leishmania.

Risk Group 3 (RG3): They are high individual risk, limited/moderate community risk. These microorganisms usually cause serious disease and may present a significant risk to laboratory workers, but may only present a moderate risk of spreading amongst a community. e.g.Brucella, Mycobacterium tuberculosis, Salmonella Typhi, Francisella, Pasteurella pestis, many arboviruses, LCM (Lymphocytic choriomeningitis ) virus, rickettsiae, chlamydia, Coccidioides, Histoplasma, human immunodeficiency viruses (HIV), Blastomyces dermatitidis, Paracoccidioides brasiliensis, Penicillum marneffei.

Risk Group 4 (RG4): They belong to the high individual and high community risk. These microorganisms usually cause life-threatening diseases and may be readily transmissible. Effective treatments are not usually available. e.g.  e .g. Marburg, Ebola, Lyssa, CFD (Creutzfeldt-Jakob disease), Equine encephalitis viruses, SARS (Severe Acute Respiratory Syndrome) virus, and certain arbovirus and they are hemorrhagic fever viruses.



Safety Measures

  • Avoiding infection from spillages and breakage
  •  Avoiding infection from Centrifuge accidents
  •  Safe pipetting: Use micropipette if possible
  •  Safe use of inoculating loop and looping out
  •  Safe use of syringes and needles: Use disposable syringes
  •  Safe and careful shaking and homogenizing
  •  Safe and careful opening culture and ampoules
  •  Safe and careful pouring infectious materials
  •  No smoking, drinking, and eating in the laboratory
  • Use of apron, Gloves, and mask, and safety cabinet in the laboratory

Biological Safety Cabinet (BSC) for Safety in Microbiology

Microbiological safety cabinets:

Types of safety cabinets:

Class I and II: are used to work with risk groups I, II, and III

Class III: used to work with risk group IV


Disinfection and decontamination of laboratory waste for Safety in Microbiology

All specimens, cultures, and other materials that have been examined in the microbiology laboratory must be made noninfectious before being discarded or leaving the laboratory.

Laboratory waste that includes articles, which will be reused, should be disinfected by chemical or physical means.

Decontamination using chemical disinfectants for

These includes:

  • Clean phenolic compound ( 2.5%)
  • Hypocholric: 0.5-1%
  • Aldehyde: Formalin 10% (v/v), Glutaraldehyde ( undiluted)
  • Alcohol: 70-80 %

Note: Chemical disinfectants must be prepared in correct dilution

2. Decontamination by autoclaving: Normally 15 lbs pressure for 15 minutes.

3. Decontamination by incineration: Destruction of microorganisms with the use of incinerator.

Transportation  of infectious materials

  • Must be packed properly as per the international rule.
  • Packed in an upright position
  • Label properly by writing ” and ” Handle carefully”.
  • While sending the specimens, follow the international rule.

International regulation regarding the transport of specimens and infectious material can be obtained from the health authority of the respective country. Airlines people can also have rules and regulations regarding this (IATA guidelines)

Personal safety precautions for Safety in Microbiology

  • Personal hygiene
  • Protective clothing
  • Protective inoculators
  • Medical supervision
  • Regular health checkup
  • Periodical Training in safety precaution

Preventing Laboratory Acquired Infections for Safety in Microbiology


  • Workplace-acquired infections are not underestimated. Even though to cause infection and disease to occur, there must be an adequate number of microbial load to cause disease (infectious dose), and a route of entry to the body.
  • Mechanisms of transmission and what their infectious dose is can help to estimate the risk and avoid infection. Information about the microbes should be gathered prior to working with them. Good starting points for gathering safety information about human pathogens are Safety Data Sheets (SDSs) and the Agent Summary Statements in the most recent edition of the Biosafety in Microbiological and Biomedical Laboratories publication.
  • Microbes are transmitted through one or more of the following routes of exposure:
  1. Sharps injuries (needlesticks, cuts with contaminated broken glass, etc., also known as parenteral exposure).
  2. Inhalation of aerosols (microscopic solid or liquid particles small enough to remain dispersed and suspended in the air for long periods; about 5 µm or less in diameter)
  3. Ingestion
  4. Mucous membrane exposure (including the eyes, inside of the mouth and nose, and the genitals)


  • Using work practices that block routes of exposure can prevent workplace infection. Good microbiological techniques (GMT) must always be used in the laboratory:
  1. Eating, drinking, smoking, applying cosmetics, or storing food for human consumption in laboratories is strictly prohibited.
  2. Potentially contaminated hands should be kept away from the mouth, eyes, and non-intact skin.
  3. Hand washing should be preferred frequently, even after wearing gloves, and scrubbed vigorously with soap and water for a full 30 seconds. The physical removal of organisms from the skin is just as important as using a disinfectant.
  4. Working bench/ work surfaces and equipment must be decontaminated immediately after using biohazardous materials.
  5. Taking on appropriate personal protective equipment (PPE) blocks potential routes of exposure.

Keynotes on Safety in Microbiology

  • High-risk group organisms present a serious biosecurity risk. Regulatory approval may be required before use. Contact the Biosafety and Biosecurity Officer prior to working with any of such organisms.
  • Biosafety levels are classified into BSL-1, BSL-2, BSL-3, and BSL-4.  Biosafety level-4 (BSL-4) is being the highest (maximum) level of containment.
  • The number of biosafety cabinets (BSC) is up to 3.


Further Readings

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