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Microbiology

13.4 Testing the Effectiveness of Antiseptics and Disinfectants

Microbiology 13.4 Testing the Effectiveness of Antiseptics and Disinfectants
  1. Preface
  2. 1 An Invisible World
    1. Introduction
    2. 1.1 What Our Ancestors Knew
    3. 1.2 A Systematic Approach
    4. 1.3 Types of Microorganisms
    5. Summary
    6. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  3. 2 How We See the Invisible World
    1. Introduction
    2. 2.1 The Properties of Light
    3. 2.2 Peering Into the Invisible World
    4. 2.3 Instruments of Microscopy
    5. 2.4 Staining Microscopic Specimens
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  4. 3 The Cell
    1. Introduction
    2. 3.1 Spontaneous Generation
    3. 3.2 Foundations of Modern Cell Theory
    4. 3.3 Unique Characteristics of Prokaryotic Cells
    5. 3.4 Unique Characteristics of Eukaryotic Cells
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. True/False
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  5. 4 Prokaryotic Diversity
    1. Introduction
    2. 4.1 Prokaryote Habitats, Relationships, and Microbiomes
    3. 4.2 Proteobacteria
    4. 4.3 Nonproteobacteria Gram-Negative Bacteria and Phototrophic Bacteria
    5. 4.4 Gram-Positive Bacteria
    6. 4.5 Deeply Branching Bacteria
    7. 4.6 Archaea
    8. Summary
    9. Review Questions
      1. Multiple Choice
      2. True/False
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  6. 5 The Eukaryotes of Microbiology
    1. Introduction
    2. 5.1 Unicellular Eukaryotic Parasites
    3. 5.2 Parasitic Helminths
    4. 5.3 Fungi
    5. 5.4 Algae
    6. 5.5 Lichens
    7. Summary
    8. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  7. 6 Acellular Pathogens
    1. Introduction
    2. 6.1 Viruses
    3. 6.2 The Viral Life Cycle
    4. 6.3 Isolation, Culture, and Identification of Viruses
    5. 6.4 Viroids, Virusoids, and Prions
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. True/False
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  8. 7 Microbial Biochemistry
    1. Introduction
    2. 7.1 Organic Molecules
    3. 7.2 Carbohydrates
    4. 7.3 Lipids
    5. 7.4 Proteins
    6. 7.5 Using Biochemistry to Identify Microorganisms
    7. Summary
    8. Review Questions
      1. Multiple Choice
      2. True/False
      3. Matching
      4. Fill in the Blank
      5. Short Answer
      6. Critical Thinking
  9. 8 Microbial Metabolism
    1. Introduction
    2. 8.1 Energy, Matter, and Enzymes
    3. 8.2 Catabolism of Carbohydrates
    4. 8.3 Cellular Respiration
    5. 8.4 Fermentation
    6. 8.5 Catabolism of Lipids and Proteins
    7. 8.6 Photosynthesis
    8. 8.7 Biogeochemical Cycles
    9. Summary
    10. Review Questions
      1. Multiple Choice
      2. True/False
      3. Matching
      4. Fill in the Blank
      5. Short Answer
      6. Critical Thinking
  10. 9 Microbial Growth
    1. Introduction
    2. 9.1 How Microbes Grow
    3. 9.2 Oxygen Requirements for Microbial Growth
    4. 9.3 The Effects of pH on Microbial Growth
    5. 9.4 Temperature and Microbial Growth
    6. 9.5 Other Environmental Conditions that Affect Growth
    7. 9.6 Media Used for Bacterial Growth
    8. Summary
    9. Review Questions
      1. Multiple Choice
      2. Matching
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  11. 10 Biochemistry of the Genome
    1. Introduction
    2. 10.1 Using Microbiology to Discover the Secrets of Life
    3. 10.2 Structure and Function of DNA
    4. 10.3 Structure and Function of RNA
    5. 10.4 Structure and Function of Cellular Genomes
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. True/False
      3. Matching
      4. Fill in the Blank
      5. Short Answer
      6. Critical Thinking
  12. 11 Mechanisms of Microbial Genetics
    1. Introduction
    2. 11.1 The Functions of Genetic Material
    3. 11.2 DNA Replication
    4. 11.3 RNA Transcription
    5. 11.4 Protein Synthesis (Translation)
    6. 11.5 Mutations
    7. 11.6 How Asexual Prokaryotes Achieve Genetic Diversity
    8. 11.7 Gene Regulation: Operon Theory
    9. Summary
    10. Review Questions
      1. Multiple Choice
      2. True/False
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  13. 12 Modern Applications of Microbial Genetics
    1. Introduction
    2. 12.1 Microbes and the Tools of Genetic Engineering
    3. 12.2 Visualizing and Characterizing DNA, RNA, and Protein
    4. 12.3 Whole Genome Methods and Pharmaceutical Applications of Genetic Engineering
    5. 12.4 Gene Therapy
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. True/False
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  14. 13 Control of Microbial Growth
    1. Introduction
    2. 13.1 Controlling Microbial Growth
    3. 13.2 Using Physical Methods to Control Microorganisms
    4. 13.3 Using Chemicals to Control Microorganisms
    5. 13.4 Testing the Effectiveness of Antiseptics and Disinfectants
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. True/False
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  15. 14 Antimicrobial Drugs
    1. Introduction
    2. 14.1 History of Chemotherapy and Antimicrobial Discovery
    3. 14.2 Fundamentals of Antimicrobial Chemotherapy
    4. 14.3 Mechanisms of Antibacterial Drugs
    5. 14.4 Mechanisms of Other Antimicrobial Drugs
    6. 14.5 Drug Resistance
    7. 14.6 Testing the Effectiveness of Antimicrobials
    8. 14.7 Current Strategies for Antimicrobial Discovery
    9. Summary
    10. Review Questions
      1. Multiple Choice
      2. True/False
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  16. 15 Microbial Mechanisms of Pathogenicity
    1. Introduction
    2. 15.1 Characteristics of Infectious Disease
    3. 15.2 How Pathogens Cause Disease
    4. 15.3 Virulence Factors of Bacterial and Viral Pathogens
    5. 15.4 Virulence Factors of Eukaryotic Pathogens
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  17. 16 Disease and Epidemiology
    1. Introduction
    2. 16.1 The Language of Epidemiologists
    3. 16.2 Tracking Infectious Diseases
    4. 16.3 Modes of Disease Transmission
    5. 16.4 Global Public Health
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. Matching
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  18. 17 Innate Nonspecific Host Defenses
    1. Introduction
    2. 17.1 Physical Defenses
    3. 17.2 Chemical Defenses
    4. 17.3 Cellular Defenses
    5. 17.4 Pathogen Recognition and Phagocytosis
    6. 17.5 Inflammation and Fever
    7. Summary
    8. Review Questions
      1. Multiple Choice
      2. Matching
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  19. 18 Adaptive Specific Host Defenses
    1. Introduction
    2. 18.1 Overview of Specific Adaptive Immunity
    3. 18.2 Major Histocompatibility Complexes and Antigen-Presenting Cells
    4. 18.3 T Lymphocytes and Cellular Immunity
    5. 18.4 B Lymphocytes and Humoral Immunity
    6. 18.5 Vaccines
    7. Summary
    8. Review Questions
      1. Multiple Choice
      2. Matching
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  20. 19 Diseases of the Immune System
    1. Introduction
    2. 19.1 Hypersensitivities
    3. 19.2 Autoimmune Disorders
    4. 19.3 Organ Transplantation and Rejection
    5. 19.4 Immunodeficiency
    6. 19.5 Cancer Immunobiology and Immunotherapy
    7. Summary
    8. Review Questions
      1. Multiple Choice
      2. Matching
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  21. 20 Laboratory Analysis of the Immune Response
    1. Introduction
    2. 20.1 Polyclonal and Monoclonal Antibody Production
    3. 20.2 Detecting Antigen-Antibody Complexes
    4. 20.3 Agglutination Assays
    5. 20.4 EIAs and ELISAs
    6. 20.5 Fluorescent Antibody Techniques
    7. Summary
    8. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  22. 21 Skin and Eye Infections
    1. Introduction
    2. 21.1 Anatomy and Normal Microbiota of the Skin and Eyes
    3. 21.2 Bacterial Infections of the Skin and Eyes
    4. 21.3 Viral Infections of the Skin and Eyes
    5. 21.4 Mycoses of the Skin
    6. 21.5 Protozoan and Helminthic Infections of the Skin and Eyes
    7. Summary
    8. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  23. 22 Respiratory System Infections
    1. Introduction
    2. 22.1 Anatomy and Normal Microbiota of the Respiratory Tract
    3. 22.2 Bacterial Infections of the Respiratory Tract
    4. 22.3 Viral Infections of the Respiratory Tract
    5. 22.4 Respiratory Mycoses
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  24. 23 Urogenital System Infections
    1. Introduction
    2. 23.1 Anatomy and Normal Microbiota of the Urogenital Tract
    3. 23.2 Bacterial Infections of the Urinary System
    4. 23.3 Bacterial Infections of the Reproductive System
    5. 23.4 Viral Infections of the Reproductive System
    6. 23.5 Fungal Infections of the Reproductive System
    7. 23.6 Protozoan Infections of the Urogenital System
    8. Summary
    9. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  25. 24 Digestive System Infections
    1. Introduction
    2. 24.1 Anatomy and Normal Microbiota of the Digestive System
    3. 24.2 Microbial Diseases of the Mouth and Oral Cavity
    4. 24.3 Bacterial Infections of the Gastrointestinal Tract
    5. 24.4 Viral Infections of the Gastrointestinal Tract
    6. 24.5 Protozoan Infections of the Gastrointestinal Tract
    7. 24.6 Helminthic Infections of the Gastrointestinal Tract
    8. Summary
    9. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  26. 25 Circulatory and Lymphatic System Infections
    1. Introduction
    2. 25.1 Anatomy of the Circulatory and Lymphatic Systems
    3. 25.2 Bacterial Infections of the Circulatory and Lymphatic Systems
    4. 25.3 Viral Infections of the Circulatory and Lymphatic Systems
    5. 25.4 Parasitic Infections of the Circulatory and Lymphatic Systems
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  27. 26 Nervous System Infections
    1. Introduction
    2. 26.1 Anatomy of the Nervous System
    3. 26.2 Bacterial Diseases of the Nervous System
    4. 26.3 Acellular Diseases of the Nervous System
    5. 26.4 Fungal and Parasitic Diseases of the Nervous System
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. Matching
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  28. A | Fundamentals of Physics and Chemistry Important to Microbiology
  29. B | Mathematical Basics
  30. C | Metabolic Pathways
  31. D | Taxonomy of Clinically Relevant Microorganisms
  32. E | Glossary
  33. Answer Key
    1. Chapter 1
    2. Chapter 2
    3. Chapter 3
    4. Chapter 4
    5. Chapter 5
    6. Chapter 6
    7. Chapter 7
    8. Chapter 8
    9. Chapter 9
    10. Chapter 10
    11. Chapter 11
    12. Chapter 12
    13. Chapter 13
    14. Chapter 14
    15. Chapter 15
    16. Chapter 16
    17. Chapter 17
    18. Chapter 18
    19. Chapter 19
    20. Chapter 20
    21. Chapter 21
    22. Chapter 22
    23. Chapter 23
    24. Chapter 24
    25. Chapter 25
    26. Chapter 26
  34. Index

Learning Objectives

  • Describe why the phenol coefficient is used
  • Compare and contrast the disk-diffusion, use-dilution, and in-use methods for testing the effectiveness of antiseptics, disinfectants, and sterilants

The effectiveness of various chemical disinfectants is reflected in the terms used to describe them. Chemical disinfectants are grouped by the power of their activity, with each category reflecting the types of microbes and viruses its component disinfectants are effective against. High-level germicides have the ability to kill vegetative cells, fungi, viruses, and endospores, leading to sterilization, with extended use. Intermediate-level germicides, as their name suggests, are less effective against endospores and certain viruses, and low-level germicides kill only vegetative cells and certain enveloped viruses, and are ineffective against endospores.

However, several environmental conditions influence the potency of an antimicrobial agent and its effectiveness. For example, length of exposure is particularly important, with longer exposure increasing efficacy. Similarly, the concentration of the chemical agent is also important, with higher concentrations being more effective than lower ones. Temperature, pH, and other factors can also affect the potency of a disinfecting agent.

One method to determine the effectiveness of a chemical agent includes swabbing surfaces before and after use to confirm whether a sterile field was maintained during use. Additional tests are described in the sections that follow. These tests allow for the maintenance of appropriate disinfection protocols in clinical settings, controlling microbial growth to protect patients, health-care workers, and the community.

Phenol Coefficient

The effectiveness of a disinfectant or antiseptic can be determined in a number of ways. Historically, a chemical agent’s effectiveness was often compared with that of phenol, the first chemical agent used by Joseph Lister. In 1903, British chemists Samuel Rideal (1863–1929) and J. T. Ainslie Walker (1868–1930) established a protocol to compare the effectiveness of a variety of chemicals with that of phenol, using as their test organisms Staphylococcus aureus (a gram-positive bacterium) and Salmonella enterica serovar Typhi (a gram-negative bacterium). They exposed the test bacteria to the antimicrobial chemical solutions diluted in water for 7.5 minutes. They then calculated a phenol coefficient for each chemical for each of the two bacteria tested. A phenol coefficient of 1.0 means that the chemical agent has about the same level of effectiveness as phenol. A chemical agent with a phenol coefficient of less than 1.0 is less effective than phenol. An example is formalin, with phenol coefficients of 0.3 (S. aureus) and 0.7 (S. enterica serovar Typhi). A chemical agent with a phenol coefficient greater than 1.0 is more effective than phenol, such as chloramine, with phenol coefficients of 133 and 100, respectively. Although the phenol coefficient was once a useful measure of effectiveness, it is no longer commonly used because the conditions and organisms used were arbitrarily chosen.

Check Your Understanding

  • What are the differences between the three levels of disinfectant effectiveness?

Disk-Diffusion Method

The disk-diffusion method involves applying different chemicals to separate, sterile filter paper disks (Figure 13.31). The disks are then placed on an agar plate that has been inoculated with the targeted bacterium and the chemicals diffuse out of the disks into the agar where the bacteria have been inoculated. As the “lawn” of bacteria grows, zones of inhibition of microbial growth are observed as clear areas around the disks. Although there are other factors that contribute to the sizes of zones of inhibition (e.g., whether the agent is water soluble and able to diffuse in the agar), larger zones typically correlate to increased inhibition effectiveness of the chemical agent. The diameter across each zone is measured in millimeters.

A) A drawing of a plate covered in bacteria. On the plate are 5 small antimicrobial disks with clear areas around them. The clear areas are zones of inhibition where bacteria do not grow. The size of the zone can be measured with a ruler or calipers to determine the effectiveness of the antibiotic. B) A photograph showing plates with antimicrobial disks with zones of inhibition.
Figure 13.31 A disk-diffusion assay is used to determine the effectiveness of chemical agents against a particular microbe. (a) A plate is inoculated with various antimicrobial discs. The zone of inhibition around each disc indicates how effective that antimicrobial is against the particular species being tested. (b) On these plates, four antimicrobial agents are tested for efficacy in killing Pseudomonas aeruginosa (left) and Staphylococcus aureus (right). These antimicrobials are much more effective at killing S. aureus, as indicated by the size of the zones of inhibition. (credit b: modification of work by American Society for Microbiology)

Check Your Understanding

  • When comparing the activities of two disinfectants against the same microbe, using the disk-diffusion assay, and assuming both are water soluble and can easily diffuse in the agar, would a more effective disinfectant have a larger zone of inhibition or a smaller one?

Use-Dilution Test

Other methods are also used for measuring the effectiveness of a chemical agent in clinical settings. The use-dilution test is commonly used to determine a chemical’s disinfection effectiveness on an inanimate surface. For this test, a cylinder of stainless steel is dipped in a culture of the targeted microorganism and then dried. The cylinder is then dipped in solutions of disinfectant at various concentrations for a specified amount of time. Finally, the cylinder is transferred to a new test tube containing fresh sterile medium that does not contain disinfectant, and this test tube is incubated. Bacterial survival is demonstrated by the presence of turbidity in the medium, whereas killing of the target organism on the cylinder by the disinfectant will produce no turbidity.

The Association of Official Agricultural Chemists International (AOAC), a nonprofit group that establishes many protocol standards, has determined that a minimum of 59 of 60 replicates must show no growth in such a test to achieve a passing result, and the results must be repeatable from different batches of disinfectant and when performed on different days. Disinfectant manufacturers perform use-dilution tests to validate the efficacy claims for their products, as designated by the EPA.

Check Your Understanding

  • Is the use-dilution test performed in a clinical setting? Why?

In-Use Test

An in-use test can determine whether an actively used solution of disinfectant in a clinical setting is microbially contaminated (Figure 13.32). A 1-mL sample of the used disinfectant is diluted into 9 mL of sterile broth medium that also contains a compound to inactivate the disinfectant. Ten drops, totaling approximately 0.2 mL of this mixture, are then inoculated onto each of two agar plates. One plate is incubated at 37 °C for 3 days and the other is incubated at room temperature for 7 days. The plates are monitored for growth of microbial colonies. Growth of five or more colonies on either plate suggests that viable microbial cells existed in the disinfectant solution and that it is contaminated. Such in-use tests monitor the effectiveness of disinfectants in the clinical setting.

A diagram showing a flask with used disinfectant. 1 ml is moved to a 9 ml sterile broth with disinfectant inactivator. Plate 10 drops (0.2 ml) onto each of 2 plates. One is incubated at 37 degrees C for 3 days, the other is incubated at room temperature for 7 days. The growth of 5 or more colonies on either plate indicates contamination of disinfectant solution.
Figure 13.32 Used disinfectant solutions in a clinical setting can be checked with the in-use test for contamination with microbes.

Check Your Understanding

  • What does a positive in-use test indicate?

Clinical Focus

Resolution

Despite antibiotic treatment, Roberta’s symptoms worsened. She developed pyelonephritis, a severe kidney infection, and was rehospitalized in the intensive care unit (ICU). Her condition continued to deteriorate, and she developed symptoms of septic shock. At this point, her physician ordered a culture from her urine to determine the exact cause of her infection, as well as a drug sensitivity test to determine what antibiotics would be effective against the causative bacterium. The results of this test indicated resistance to a wide range of antibiotics, including the carbapenems, a class of antibiotics that are used as the last resort for many types of bacterial infections. This was an alarming outcome, suggesting that Roberta’s infection was caused by a so-called superbug: a bacterial strain that has developed resistance to the majority of commonly used antibiotics. In this case, the causative agent belonged to the carbapenem-resistant Enterobacteriaceae (CRE), a drug-resistant family of bacteria normally found in the digestive system (Figure 13.33). When CRE is introduced to other body systems, as might occur through improperly cleaned surgical instruments, catheters, or endoscopes, aggressive infections can occur.

CRE infections are notoriously difficult to treat, with a 40%–50% fatality rate. To treat her kidney infection and septic shock, Roberta was treated with dialysis, intravenous fluids, and medications to maintain blood pressure and prevent blood clotting. She was also started on aggressive treatment with intravenous administration of a new drug called tigecycline, which has been successful in treating infections caused by drug-resistant bacteria.

After several weeks in the ICU, Roberta recovered from her CRE infection. However, public health officials soon noticed that Roberta’s case was not isolated. Several patients who underwent similar procedures at the same hospital also developed CRE infections, some dying as a result. Ultimately, the source of the infection was traced to the duodenoscopes used in the procedures. Despite the hospital staff meticulously following manufacturer protocols for disinfection, bacteria, including CRE, remained within the instruments and were introduced to patients during procedures.

Micrograph of oval cells.
Figure 13.33 CRE is an extremely drug-resistant strain of bacteria that is typically associated with nosocomial infections. (credit: Centers for Disease Control and Prevention)

Go back to the previous Clinical Focus box.

Eye on Ethics

Who Is Responsible?

Carbapenem-resistant Enterobacteriaceae infections due to contaminated endoscopes have become a high-profile problem in recent years. Several CRE outbreaks have been traced to endoscopes, including a case at Ronald Reagan UCLA Medical Center in early 2015 in which 179 patients may have been exposed to a contaminated endoscope. Seven of the patients developed infections, and two later died. Several lawsuits have been filed against Olympus, the manufacturer of the endoscopes. Some claim that Olympus did not obtain FDA approval for design changes that may have led to contamination, and others claim that the manufacturer knowingly withheld information from hospitals concerning defects in the endoscopes.

Lawsuits like these raise difficult-to-answer questions about liability. Invasive procedures are inherently risky, but negative outcomes can be minimized by strict adherence to established protocols. Who is responsible, however, when negative outcomes occur due to flawed protocols or faulty equipment? Can hospitals or health-care workers be held liable if they have strictly followed a flawed procedure? Should manufacturers be held liable—and perhaps be driven out of business—if their lifesaving equipment fails or is found defective? What is the government’s role in ensuring that use and maintenance of medical equipment and protocols are fail-safe?

Protocols for cleaning or sterilizing medical equipment are often developed by government agencies like the FDA, and other groups, like the AOAC, a nonprofit scientific organization that establishes many protocols for standard use globally. These procedures and protocols are then adopted by medical device and equipment manufacturers. Ultimately, the end-users (hospitals and their staff) are responsible for following these procedures and can be held liable if a breach occurs and patients become ill from improperly cleaned equipment.

Unfortunately, protocols are not infallible, and sometimes it takes negative outcomes to reveal their flaws. In 2008, the FDA had approved a disinfection protocol for endoscopes, using glutaraldehyde (at a lower concentration when mixed with phenol), o-phthalaldehyde, hydrogen peroxide, peracetic acid, and a mix of hydrogen peroxide with peracetic acid. However, subsequent CRE outbreaks from endoscope use showed that this protocol alone was inadequate.

As a result of CRE outbreaks, hospitals, manufacturers, and the FDA are investigating solutions. Many hospitals are instituting more rigorous cleaning procedures than those mandated by the FDA. Manufacturers are looking for ways to redesign duodenoscopes to minimize hard-to-reach crevices where bacteria can escape disinfectants, and the FDA is updating its protocols. In February 2015, the FDA added new recommendations for careful hand cleaning of the duodenoscope elevator mechanism (the location where microbes are most likely to escape disinfection), and issued more careful documentation about quality control of disinfection protocols (Figure 13.34).

There is no guarantee that new procedures, protocols, or equipment will completely eliminate the risk for infection associated with endoscopes. Yet these devices are used successfully in 500,000–650,000 procedures annually in the United States, many of them lifesaving. At what point do the risks outweigh the benefits of these devices, and who should be held responsible when negative outcomes occur?

Diagram of a person with a duodenoscope inserted into their mouth – it travels through the esophagus and stomach to the duodenum. A photograph of the end of the scope shows a foreceps elevator in the lowered/closed and raised/open position.
Figure 13.34 The elevator mechanism in a duodenoscope contains crevices that are difficult to disinfect. Pathogens that survive disinfection protocols can be passed from one patient to another, causing serious infections. (credit “photos”: modification of work by Centers for Disease Control and Prevention)
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