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This series of self-study lessons on Central Service topics was developed by the International Association of Healthcare Central Service Materiel Management (IAHCSMM). The lessons are administered by Purdue University’s Continuing Education Division.

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Lesson Plan CRCST 403
Microbiology and Infection Control

The relationship between microbiology and infection control is a marriage made in the laboratory. A knowledge of one and not the other leads to a broken foundation unable to support the practice of Central Service (CS)as we know it. Information stemming from these two disciplines allows healthcare facilities in the United States to offer patient services that are unequalled anywhere else in the world. As our knowledge deepens, however, we are learning that an over-zealous desire to eliminate diseases caused by microbes has sometimes, instead, developed strains of "super microbes." Many of these"super microbes" have evolved into drug-resistant organisms that we cannot control. Technicians' willingness and ability to learn more about the basics of microbiology, and to apply this knowledge as they do their jobs, will enable CS professionals to serve their healthcare facilities and patients at the highest-possible level.

Objective 1: Explain how a basic understanding of microbiology is crucial toa Central
Service technician.

Each part of a Central Service technician's job—including every aspect of cleaning, disinfecting, packaging, sterilizing, storing, and distributing—is linked to microbiology. We know that microbes are invisible to the naked eye and that, in this case, what we cannot see can, indeed, harm us and our patients. There is an old saying that admonishes us to, "Know thine enemy." To protect ourselves and our patients, we need to understand that our "enemy" (microbes) can cause disease and even death. Knowing this, technicians consistently use carefully developed cleaning techniques designed to eliminate most of the microbes found in healthcare environments.

Disinfection and sterilization practices are designed to destroy resistant organisms that are extremely difficult to control. Packaging materials and methods of storage and distribution apply our knowledge of microbiology and infection control to help assure that microbes cannot contaminate sterilized items. CS staff know that the use of appropriate personal protective equipment (PPE) can help prevent exposing themselves to microbes. Some aspect of basic microbiology affects technicians every minute they spend at work and in every decision they make as they perform their daily jobs.

Objective 2: Describe how knowledge ofmicrobes can affect infection control.

Microbes have particular sizes, shapes, and living "habits" that help microbiologists to identify them by name. Their basic shapes areround, rod, and spiral, which are referred to as, respectively, cocci, bacilli, and spirilla.

The "habits" that help to reveal each microbe's identity include:

• the preferred temperature at which the ybest grow and reproduce
• their ability (or lack of ability) to accept dyes as stains
• their need, or lack of need for free oxygen.
• their style or technique of reproduction
• specific pattern(s) of growth
• speed of growth or reproduction
• locations where they are typically found

Central Service staff have learned that many microorganisms are not harmful to humans and some, in fact, are beneficial. (Consider, for example, those used to disperseoil slicks in oceans, those used in drug production, and others that synthesize vitamins in the human body's digestive tract.) Some microbes that do not harm humans in certain parts of the body do cause harm if they are inother parts. For example, Escherichia coli (E. coli)is normally found in a human's intestines where they do not cause disease but, when these organisms enter one's bladder, they cause a serious infection.

Objective 3: Define morphologyand itsimportance to infection control.

Understanding the usual locations and "habits" of microbes helps us identify and avoid disease and infection. Unfortunately, microorganisms can be difficult to identify, and that is where morphology becomes helpful. The term, morphology, refers to the segment of microbiology that identifies the form andstructure of an organism or any of its parts.

For example, when a patient has aninfection, an evidence sample (culture) is sent to the microbiology lab for analysis. Accurate identification is essential to taking appropriate control measures to prevent further spread of infection. A microbiologist can perform many types of examinations to discover the "habits" of the microbe under study. The science of morphology guides this discovery process. After the microbe is identified, infection control efforts can begin. For example, if the microbiologist reports that tuberculosisbacillus (TB) has been identified, the patientis put on respiratory isolation and prescribed drugs to treat the TB infection.The study of microbial morphology enables us to stay healthy. It teaches us to refrigerate specific foods at certain temperatures, to cook meats to specific temperatures, to wear a mask in certain situations, and to always use protective eyewear, gowns, and other PPE in other instances. Morphology has led to the cleaning, disinfecting, and sterilizing techniques we use in our Central Service departments. "Knowing the enemy" truly does help to prevent and control infections.

Objective 4: Explain how infection control principles influence basic cleaning and disinfecting processes.

The main goal of infection control is to break the "chain of infection," (see Figure1.)¹ Think of the chain of infection as a chain with six links that must all be presentand intact for the spread of an infectious disease to occur. Our goal is to break one or more links in the chain. The links are:

• An infectious agent: a microbe. Ways to eliminate the microbe include rapid identification by culture (as in our discussion of morphology, above) and prompt treatment of the infection. Other tactics that eliminate the microorganisms include the avoidance of cross-contamination and the physical removal of contaminated substances by consistently cleaning and following proper disinfection and sterilization procedures.
• A reservoir: a "hangout" where the microbe can survive. The most common reservoirs associated with hospital-acquired infections are patients, healthcare workers, healthcare equipment, and the environment.
• A portal of exit: a way for microbes toget out of the "hangout." Portals of exitcommonly associated with humanreservoirs include the respiratory, genitourinary, and gastrointestinaltracts; the skin and mucous membranes; blood; and through theplacenta (from mother to baby).
• A mode of transmission: the transportation method that microbesuse to get from the old "hangout" to thenew "hangout." The four major modesof transmission are by (a) direct contactwith the source, indirect contactthrough an intermediate object, anddroplet contact; (b) common vehicle(when infectious agents are in a "vehicle" such as food, blood or water); (c) airborne; and (d) vector-borne (suchas by insects or from their bites).
• A portal of entry: a way for microbesto get into the new "hangout." Portals of entry associated with a human hostinclude the respiratory, genitourinary, and gastrointestinal tracts; through the skin or mucous membranes; transplacental (from fetus to mother); and parenteral (by blood through needle punctures).
• A susceptible host: a new "hangout" for the microbes. A suitable host is a person who is unable to resist infection by the infectious agent. Factors affecting the host's susceptibility to and the severity of an infection include age, gender, ethnicity, disease history or underlying disease, nutritional status, compromised immune status,
  and trauma.

CS technicians must consistently use basic principles to break the chain of infection and prevent the spread of infection. "Knowing the enemy" and its morphology (habits of the microbes) are important concerns that impact the selection of the appropriate control method. Central Service staff must destroyas many microbes as possible when they use disinfection processes. Reducing the levels of microbes helps ensure the effectiveness of the chosen sterilization method. Reservoirs are eliminated when technicians properly rinse and dry items,and when they clean and disinfect the sinks and tools used to process items.

The microbes' portal of exit is probably the most difficult link in the chain of infection to control. Everyone would have to stop breathing, coughing, sneezing, and moving to effectively break this link. Practical tactics that can be used include the use of facial tissues, hand hygiene, wound dressings, control of secretions and excretions, proper trash and waste disposal, and the correct use of PPE.

Controlling the host is the next biggest challenge. The best we can do is keep the host strong and healthy. A healthy diet, good hygiene, proper skin care, and adequate rest helps one's internal immunesystem to fight intruding microbes. The second line of defense is to always use PPE appropriately because doing so helps to break the portal of entry link in the infection control chain.

The mode of transmission uses morphology information to correctly identify the microbes. Once identified, we will know where it likes to live and how it is transported from one host to another. As we learn this, roadblocks can be established. The use of Standard Precautions and Isolation Techniques help prevent transmission. Remember that one's hands provide a very mobile transport vehicle. Strict compliance with PPE requirements and the consistent use of proper hand-washing techniques are among the most effective available roadblocks to the transport of microbes.

Objective 5: Review the Spaulding Classification System and its impact on sterile
processing activities.

The Spaulding Classification System is another tool that can guide our infection control efforts. This system outlines disinfection and sterilization needs for items based upon their risk factors and the potential for microbe (microbial) transmission. Criticalitems must be sterilefor use. These include surgical instruments,needles, and catheters that enter the vascular system. Semi-Critical itemsrequire high level disinfection methods.These include gastrointestinal and gastrourinary endoscopes and laryngoscopes. Non-Critical items such asblood pressure cuffs, electrocardiogram(EKG) wires, and thermometers need intermediate-level disinfection. TheSpaulding Classification System helpstechnicians select cleaning and disinfectionprocedures appropriate for the item beingprocessed. This system demonstratesmicrobiology and infection control knowledge in action.

Objective 6: Discuss the impact of globalization on infection control activities.

Infection control practices are affected by globalization (a big word that translates into, "It's a small world after all!"). Our world seems to be getting smaller because we are able to move around it more easily and quickly than ever before. More people are willing and able to travel great distances. The bad news is that microbes like to hitch rides into new frontiers along with us. Healthcare professionals have been forced to learn more about microbiology, to learn who the new microbial enemies are, and to discover what must be done to control the spread of the infections that they cause.

Most of today's CS employees have lived through the discovery of the human immunodeficiency virus (HIV) and its aftermath, and know how to protect themselves and others. They've seen the discovery of Hepatitis C, D, and E. In addition, diseases such as polio, TB, and malaria, that were considered conquered years ago, are re-emerging in the United States. Globalization has demonstrated dramatically that infectious diseases suchas Severe Acute Respiratory Syndrome (SARS) can move quickly from China into Canada and then into the United States. We are fortunate to have the U.S. government's Centers for Disease Control (CDC) keeping watch for disease outbreaks and alerting us about the need to adjust our infection control practices. Central Service employees are, indeed, at the healthcare industry's front line in infection
control activities.

Reference

1 IAHCSMM Central Service Technical Manual, Seventh Edition, 2007, Chapter 4, pages 59-76.

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