UNIT 1

Introduction to Microbiology with special reference to medical microbiology

Definition, History, and Relationship of microorganism to man.

Safety guidelines in a microbiology laboratory. Universal precautions.

Bio-safety cabinets: principle, types of bio-safety cabinets and their applications.

Definitions

• 1. Microbiology: Microbiology is the study of microorganisms such as bacteria, viruses, fungi, protozoa, and algae.

• 2. Microorganism: Microorganisms are also known as microbes. Microorganisms are tiny living organisms that are not visible to the naked eye. They include bacteria, viruses, fungi, archaea, and protozoa.

• 3. Pathogens: Pathogens are microorganisms that can cause disease in their host. They include bacteria, viruses, fungi, and parasites. These agents enter the host's body and multiply within the host to cause diseases.

• 4. Commensals: Commensals are organisms that live in close association with another species, benefiting from the relationship without harming the host. This type of interaction is known as commensalism. In this relationship, the commensals may gain food, shelter, or transportation, while the host remains unaffected.

• 5. Symbiosis: Symbiosis is a biological relationship between two different organisms that live closely together. This relationship can be mutualistic (both benefits), commensalism (one benefits and the other is neither helped nor harmed), or parasitic (one benefits at the expense of the other).

• a.Mutualistic: "Mutualistic" is a type of symbiotic relationship between two different organisms where both partners benefit from the association. For eg. certain bacteria in the human gut help in digestion. These bacteria receive nutrients and a place to survive.

• b.Commensalistic: "Commensalistic" is a type of symbiotic relationship between two organisms where one benefits and the other is neither helped nor harmed. Bacteria on human skin. Here the bacteria may gain nutrients or a suitable environment without affecting the host.

• c.Parasitic: "Parasitic" is a type of symbiotic relationship between two organisms where one benefits, and the other is harmed. Parasitic microorganisms are called Parasites. Parasites cause harm to the host.

• 6. Opportunists: "opportunists" are opportunistic pathogens. Opportunistic pathogens live in a healthy host. They cause infections when the host's immune system is weakened.

• 7. Host: In microbiology, a "host" is an organism that provides space and nutrients for another organism. The host supports the growth, survival, and reproduction of the microorganism. These microorganisms may be beneficial or harmful to the host.

• 8. Protista: Unicellular microorganisms are classified under the Kingdom Protista such as protozoa, algae, and slime molds.

• 9. Prokaryotic: Microorganisms without a nucleus and membrane-bound organelles are called prokaryotic. These organisms have genetic material in the form of a single circular DNA molecule. Prokaryotes include bacteria and archaea.

• 10. Eukaryotic: Microorganism cells containing a distinct nucleus and other membrane-bound organelles are called eukaryotic. eg. are plants, animals, fungi, and protists, Eukaryotic cells are generally larger and more structurally complex compared to prokaryotic cells.

• 11. Viruses: Viruses are microscopic infectious agents that can only multiply inside the living cells of organisms. They consist of genetic material (either DNA or RNA) surrounded by a protein coat called a capsid. They remain as living microorganisms inside living cells and act as nonliving outside living cells. They infect animals, plants, fungi, bacteria, and archaea.

• 12. Bacteriology: Bacteriology is the branch of microbiology that deals with the study of bacteria. Bacteriologists study various aspects of bacteria to understand their roles in health, disease, environmental processes, and industrial applications.

• 13. Mycology: Mycology is the study of fungi. Mycologists study various aspects of fungi to understand their beneficial and harmful effects on humans and other organisms, and their applications in fields such as medicine, agriculture, and industry.

• 14. Parasitology: Parasitology is the branch of biology that focuses on the study of parasites. Parasites are organisms that live in or on another organism (called the host) and get nutrients from the host.

• 15. Phycology: "Phycology" is the scientific study of algae.

• 16. Virology: Virology is the scientific study of viruses.

History

1. Antiquity to 17th Century:

   • In ancient times, scholars like Hippocrates and Aristotle mention microorganisms.

   • Antonie van Leeuwenhoek's invention of the microscope in the 17th century allowed for the first visual observations of bacteria and protozoa.

2. 18th Century:

   • Francesco Redi's experiments in the 17th and 18th centuries helped disprove the idea that life arises from non-living matter.

   • Studies of fermentation by scientists like Louis Pasteur contribute to our understanding of microbial processes.

3. 19th Century:

   • Louis Pasteur's experiments proved the germ theory of disease. He demonstrated that microorganisms are responsible for fermentation and disease transmission.

   • Robert Koch developed techniques to isolate and cultivate pure cultures of bacteria, He established Koch's postulates to prove that specific microbes cause specific diseases.

4. 20th Century:

   • The discovery of antibiotics like penicillin by Alexander Fleming in 1928 provides effective treatments for bacterial infections.

   • Advances in virology led to the identification and study of viruses, their structure, replication, and role in diseases.

   • The development of techniques such as polymerase chain reaction (PCR) and DNA sequencing transformed microbiology, for the identification and characterization of microorganisms.

5. 21st Century:

   • Microbiology evolves with the start of metagenomics. It studies microbes in their natural environments without the need for culturing.

   • The field has expanded into areas such as microbial ecology, industrial microbiology, and biotechnology, food production, environmental effect.

Relationship of microorganism to man.

• The relationship between microorganisms and humans is complex. Microorganisms (microbes) impact various aspects of our lives such as health, industry, and the environment.

• 1. Human Health: Microorganisms influence the human health. Some microbes cause diseases, many are beneficial and essential for our well-being. For eg. Our digestive system depends on bacteria (gut microbiota) to help digestion, produce vitamins, etc.

• 2. Disease: Certain microbes are pathogens. They cause illnesses. It may be mild infections or serious diseases. Understanding microbial pathogens helps to prevent and treat diseases.

• 3. Biotechnology: Microbes are part of biotechnological processes. They are used in the production of antibiotics, vaccines, and various therapeutic proteins. Biotechnology controls microbes to produce enzymes, biofuels, and biodegradable plastics.

• 4. Environmental Impact: Microorganisms are used for nutrient cycling and decomposition in ecosystems. They break down organic matter and release nutrients that support plant growth. Some microbes also degrade pollutants to clean up contaminated environments.

• 5. Food Production: Microbes are used in food fermentation processes, such as in the production of yogurt, cheese, and bread. They help in flavor development and preservation. They enhance the quality and safety of food products.

• 6. Research and Discovery: Microbes are a source of new compounds and enzymes that are used in medicine, agriculture, and industry. Researchers study microbes to invent new bioactive substances and understand fundamental biological processes.

Dr. Pramila Singh

Safety guidelines in a microbiology laboratory. Universal precautions

Safety guidelines in microbiology laboratories are required to protect personnel, the environment, and to prevent the spread of infection. The following are safety guidelines to be followed in the microbiology laboratories.

• 1. Personal protective equipment (PPE): Wear proper PPE to protect eyes, skin, and clothes from microorganisms. PPE includes a laboratory coat, gloves, and safety goggles or face shields.

• 2. Hand hygiene: Wash hands thoroughly before entering the laboratory, after handling microorganisms, and before leaving the microbiology laboratory. Use proper soap and water or hand sanitizers to prevent the spread of microorganisms.

• 3. Laboratory Design and Layout: The design of the laboratory should have a proper ventilation system. I prevent the accumulation of airborne contamination inside the laboratory. Its design should prevent cross-contamination.

• 4. Work area preparation: Disinfect work area surfaces and equipment before and after use. This prevents contamination and the spread of infection.

• 5. Labeling and storage: Label all containers properly with the name of the microorganism, date, and person working. Store cultures, samples, and reagents at the proper temperature.

• 6. Aseptic techniques: Use aseptic techniques to handle microorganisms and prevent contamination.

• 7. Handling biohazardous materials: Infectious materials are considered biohazardous materials. Proper biological safety cabinets or fume hoods are used if working with aerosol-producing procedures.

• 8. Disposal of materials: Contaminated materials such as used cultures, pipettes, gloves, etc are biohazards. Dispose of them observing laboratory rules and regulations.

• 9. Emergency Procedures: Be familiar with emergency procedures, an emergency exists, eyewash solution, safety shower, fire extinguisher, etc.

• 10. Training and education: Ensure training of all personnel on laboratory safety.

• 11. Personal behavior: Avoid eating, drinking, applying cosmetics, and touching faces in the laboratory. This prevents accidental ingestion or exposure to pathogens.

• 12. Reporting incidents: Report accidents or exposure to a supervisor or any responsible person. This helps to take quick action and medical attention.

Biosafety Cabinet

Biosafety cabinets are specialized laboratory equipment to control the environment for working with hazardous microorganisms.

Biosafety cabinets Principle: Biosafety cabinets create a physical barrier to prevent the spread of hazardous materials and microorganisms. It protects the personnel from infection working inside the laboratory.

Biosafety cabinet works on the following principles: Biosafety cabinets use directed air flow, HEPA filtration, and physical barrier to provide a safe working space for the operator. It protects operators from bio-hazardous materials and infection. 

• 1. Protection: Biosafety cabinets protect both personnel and the environment. Biosafety cabinets have a HEPA filter system (High Efficiency Particulate Air). HEPA filter stops entry of airborne particles and microorganisms into Biosafety cabinets. This helps to prevent the entry of hazardous materials into the laboratory environment.

• 2. Airflow and ventilation: Biosafety cabinets have a controlled airflow pattern. Air from the laboratory enters Biosafety cabinets through a HEPA filter. Thus Biosafety cabinets shall be free from microorganisms. Air entering into Biosafety cabinets develops a positive pressure. This will not allow entry of microorganisms into Biosafety cabinets. Three-zone protections control airflow and ventilation.

  • Work zone: The operator works with materials in the work zone. The direction of airflow prevents contamination.

  • Contaminated zone: This area surrounds the work zone. It is in between the work zone and the external environment. Air from the contaminated zone enters into work zone through a HEPA filter.

  • Clean zone: This area is at the rear part of the biosafety cabinet. Filtered air from the biosafety cabinet enters the laboratory through ventilation.

• 3. Sealed work area: Biosafety cabinets allow to work inside it with a physical barrier to protect the operator from infection. The opening part of the biosafety cabinet has a transparent panel to close or open the biosafety cabinet.

• 4. Use PPE: The operator must wear PPE while working with the biosafety cabinet.

Types of bio-safety cabinets and their applications: There are mainly three types of bio-safety cabinets depending upon their airflow pattern.

• 1. Class I Biosafety cabinet: Airflow is directed from the laboratory into the biosafety cabinet. Then exhausted to the outside environment through a HEPA filter. This airflow pattern protects the operator but does not provide a sterile area inside the biosafety cabinet.

• Application: It is suitable to work with low to moderate-risk materials. Operator protection is the main concern. They are used to handle chemicals, powders, and nonvolatile toxic substances. They are not suitable for volatile or infectious materials that require a sterile environment.

• 2. Class II Biosafety cabinets: It is further divided into four subtypes based on the airflow pattern and other features.

  • · Type A1

  • Airflow: It has inward airflow. 70% of the air is for recirculation through a HEPA filter. 30% air exhausted to the outside cabinet.

  • Application/ Usage: It is suitable to handle low to moderate-risk materials and volatile chemicals. It protects both the operator and the environment.

  • · Type A2

  • Airflow: Similar to type A1. However, it maintains a higher level of protection by maintaining constant airflow velocity across the work surface.

  • Application/ Usage: It is commonly used in microbiology research, cell culture, and other applications that handle moderate-risk materials. It provides personnel, environmental, and sample protection.

  • Type B1

  • Airflow: It maintains constant inward flow. Approximately 70% of air recirculation is through a HEPA filter. 30% exhausted through the exhaust system.

  • Application: It is suitable for handling hazardous volatile chemicals and radioisotopes.

  • · Type B2

  • · Airflow: It maintains constant inward airflow. But all exhausted air is filtered through a HEPA filter and returned to the laboratory environment.

  • · Application: It is used for high-risk microbiological work. It provides personnel and environmental protection. It also maintains a sterile work environment.

• 3. Class III Biosafety cabinets:

• Airflow: It is enclosed and gas-tight. Air is exhausted through the HEPA filter from the cabinet. It has used gloves and a double-door pass-through system.

• Application: It is used for most hazardous operations. The operator works through the attached gloves system. It provides maximum protection to the operator.