Antibiotic Resistance: How it Happens and Strategies to Decrease the Spread of Resistance

Welcome and Overview

This session will discuss antibiotic resistance and how it develops, existing threats from antibiotic resistant organisms, the opportunities that exist for improving the judicious use of antibiotics, and strategies and resources to decrease the development of antibiotic resistance and prevent the spread of antibiotic resistant bacteria in long-term care organizations.

This session is one of a series of six sessions for nursing homes to support implementation of principles and practices of antibiotic stewarship and prevention and management of C. difficile infections.


  • Describe what is meant by antibiotic resistance.
  • Explain how antibiotic resistance develops.
  • Define key antibiotic resistant organisms in healthcare.
  • Employ strategies to decrease the development and spread of antibiotic resistance.

 How can you use this session?

This session focuses on antibiotic resistance in the nursing home setting. The material is intended to be useful for guiding individual practice and as an educational resource for staff involved in the care of nursing home residents. Nursing home leaders can review the content in this session and decide which components would be helpful to staff in their facility. The components can be shared and discussed during staff education sessions, or they can be accessed by staff online at any time.

Depending on which components you choose to review and/​or share and discuss with staff, this session may take 30-90 minutes.


Here is an outline of what is in this session. You can click on the hyperlinks to go directly to a section or scroll down below the outline to see all section content.

What is antibiotic resistance?Review short narrative
Why do bacteria become resistant to antibiotics?Review short narrative
How do bacteria become resistant to antibiotics?Review short narrative and graphic
How much of a problem is antibiotic resistance?Review short narrativeAccess CDC information on top 18 drug resistant threats in the USDiscussion question on urgent or serious resistant organisms you have seen in your facility
Are antibiotic resistant infections a problem in nursing homes?Review short narrative
How can your labs help you to identify resistant bacteria?Review short narrativeAccess the resource About Antibiograms (Antimicrobial Susceptibilities of Selected Pathogens)Access AHRQ's Concise Antibiogram Toolkit
How can you prevent the development and spread of antibiotic resistance?Review short narrativeAccess SHEA/APIC Guideline: Infection Prevention and Control in the Long-Term Care FacilityLink to Antibiotic Stewardship sessionLink to four-part series recorded webinar Take Action to Prevent and Manage Multidrug-resistant Organisms and C. difficile in the Nursing Home in the Clostridium difficile Part Two session
ActivityDiscussion questions to discuss with your laboratory to gain situational awareness of antibiotic resistance in your organization
Take Home MessagesReview short narrative
Optional Tools and ResourcesAccess additional tools and resources

 What is antibiotic resistance? 

Antibiotic resistance is the ability of a bacteria to change so that antibiotics can’t kill it or stop it from reproducing. In other words, the bacteria become ​"resistant" and continue to multiply in the presence of therapeutic levels of an antibiotic. Antibiotic resistance is a naturally occurring phenomenon; bacteria naturally evolve in order to survive. However, this process can be accelerated or made worse by misuse of antibiotics.

 Why do bacteria become resistant to antibiotics? 

Because bacteria are living organisms, they contain specific DNA. Bacteria do not start out sensitive to all antibiotics and then become resistant to them. Rather, certain types of bacteria have what is called innate resistance to certain types of antibiotics. This innate resistance is naturally part of the bacteria genetic make-up or part of the DNA. This is why some antibiotics are not expected to work on certain types of infections.

However, bacteria can also acquire genes that allow them to become resistant to antibiotics which they were once sensitive to. This is called becoming resistant through acquisition. The bacteria can acquire resistance genes from other bacteria and add the resistance genes to its DNA in order to increase its chance of survival.

There are different ways that bacteria can resist the effects of antibiotics:

  • Bacteria can produce proteins. Generally, these proteins are enzymes that destroy antibiotics. These enzymes can chew up antibiotics in one or more drug classes with related structures. For example, the extended-spectrum beta-lactamases (ESBLs) are enzymes which destroy penicillins and cephalosporins. 
  • Bacteria can change their cellular structure to either block the binding site of the antibiotic or disrupt the function of the antibiotic. For example, methicillin resistance occurs through a change in the cell wall of staph bacteria, which prevents binding.
  • Finally, bacteria can reduce their exposure to antibiotics, either by pumping the antibiotics out of their cellular space or by creating barriers in their cell wall and cell membranes so the drugs can’t get in. For example, efflux pumps contribute to carbapenem resistance in Pseudomonas.

 How do bacteria become resistant to antibiotics? 

Anytime an antibiotic is used, bacteria that can resist that antibiotic have a greater chance of survival than those that are susceptible to the antibiotic. Resistant strains of bacteria have a survival advantage. So, simply using antibiotics, even judicious use, can increase the risk of the spread of antibiotic resistance. However, judicious use can have an important impact on slowing this process and limiting the spread of resistance. Therefore, antibiotics should only be used to manage serious bacterial infections, and with the right dose, duration, and route of administration.

Click here to see a graphic from the CDC showing how antibiotic resistance happens (click on the graphic to download and print it).

 How much of a problem is antibiotic resistance? 

Antibiotic resistance is one of the most important public health threats that we face today. According to the CDC, each year in the United States, at least two million people become infected with bacteria that are resistant to antibiotics, and at least 23,000 people die each year as a direct result of these infections. The CDC states that these estimates are based on conservative assumptions and are likely minimum estimates. They are the best approximations that can be derived from currently available data.

The CDC has shared information on the top 18 drug-resistant threats to the United States. These threats were categorized based on level of concern: urgent, serious, and concerning.

Urgent healthcare threats include: 

  • C. difficile and
  • Carbapenen-resistant Enterobacteriaceae (CRE).

Serious healthcare threats include: 

  • methicillin-resistant Staphylococcus aureus,
  • vancomycin-resistant Enterococcus,
  • extended spectrum B-lactamase producing Enterobacteriaceae, and
  • multidrug-resistant Pseudomonas and Acinetobacter.

Discussion question: Which of the urgent or serious resistant organisms have you seen in your facility?

NOTE: There are two sessions that focus on C. difficile in this six part series.

 Are antibiotic resistant infections a problem in nursing homes?

Multi-drug resistant organisms (MDROs) are causes of infection and colonization in long-term care residents. Examples include:

  • methicillin-resistant Staphylococcus aureus (MRSA),
  • vancomycin-resistant Enterococci spp. (VRE),
  • drug-resistant Streptococcus pneumoniae, and
  • multidrug-resistant gram-negative bacteria (e.g., Pseudomonas aeruginosa, Acinetobacter spp and extended-spectrum B-lactamase (ESBL)-producing Enterobacteriaceae).

Nursing home residents are at increased risk for colonization and infection with resistant organisms (colonization refers to bacteria being in or on the body, but not making you sick). Residents are at an increased risk because of:

  • increased exposure to antibiotics;
  • increased exposure to invasive devices;
  • resident factors such as: 
    • chronic illness,
    • age, and
    • changes in the immune system; and
  • facility factors such as: 
    • close living conditions with others and transfers between acute and long-term care settings (each transfer provides an opportunity for germs to spread between facilities), and
    • inadequate staff hand hygiene.

If you are not using antibiotics judiciously, you can be promoting the development of resistant strains in your facility. That is why tracking on what antibiotics are being used for what reasons, and using antibiograms (discussed in the next section) to track on resistance and susceptibility patterns helps you to know if you are developing resistance to specific antibiotics in your facility.

People that have multi-drug resistant organisms and are being admitted to your facility from hospitals present you with a challenge, as now you need to keep other residents and staff from being infected, in an environment that provides care in a home like setting.

Prescribing practices help us to prevent the development of resistant organisms in each facility. Preventing the development and spread of antibiotic resistant organisms is not only about prescribing. It is also about infection control.

Poor infection prevention and control practices contribute to further emergence and spread of antibacterial resistance.

 How can your labs help you to identify resistant bacteria?

First, let’s review how the lab identifies bacteria. There are a couple different ways that can be done.

First, microbiology labs grow the bacteria. Laboratory personnel plate a sample of the specimen received directly onto culture plates and then incubate them. When bacteria start to grow, the system will flag or the technicians will notice organisms growing on the plate. They will use growth patterns, gram stains and other biochemical testing to say what exactly the bacterial isolate is that’s growing on the plates.

There are ways to streamline that process through use of selected culture media and an example of that is CHROMagar. These culture medias are designed to react with certain features of bacteria, and they are a faster way to visually identify what is growing.

A different technology and something that’s gaining a lot of use in labs is using DNA to identify bacteria. There are molecular diagnostic tests which take fragments of the DNA or RNA of bacteria and based on those fragments, identify what the organisms are. This technology is called nucleic acid amplification or sometimes is referred to as specific amplification method, polymerase chain reaction (PCR). This is a new technology, and still a very expensive system, so many clinical labs don’t necessarily have this in place yet.

Next, let’s review how the lab identifies the susceptibility patterns for organisms identified. 

In other words, how does the lab identify which antibiotics would be effective in killing the bacteria. In order to do that, the lab tests the growth of these organisms in the presence of different antibiotics, and that’s how they determine which antibiotics inhibit growth and which don’t. They define the susceptibility using something called the minimum inhibitory concentration. That’s the lowest amount of the drug needed to stop growth of the bacteria.

A lot of labs now use systems that are automated to help speed up and streamline the process for identification and susceptibility testing and these automated systems can combine the growth and susceptibility into one platform, which means you get the answers much quicker. Some trade names of these systems include: Microscan, Walkaway, VITEK 2, Phoenix, and Sensititre. 

Laboratories should have procedures to notify you when Carbapenem resistant bacteria are identified. It is important to understand whether and how the lab identifies carbapenamases – enzymes created by bacteria that make the bacteria resistant to the very powerful broad spectrum Carbapenem antibiotics – and how they would flag an organism that shows up in their lab as a Carbapenem resistant organism. The lab should notify you when a Carbapenem resistant bacteria is identified because that is critically important in terms of your clinical management of a resident as well as for your infection prevention program. Carbapenem resistance results in infections which cannot be treated with current antibiotics.

Finally, labs can create antibiograms.

Your laboratory can provide you with a summary snapshot of antibiotic resistant patterns across all of the organisms (cultures from residents) in your building. This is called an antibiogram which is a summary of the bugs that are frequently identified in culture and the susceptibility to some of the common antibiotics that are used to treat those infections. Typically, on the antibiogram, the organisms are listed down the left column, first listing the gram negative organisms, and then the gram positive organisms. Then across each row, the number of organisms tested is listed, along with the percent of tested organisms that were susceptible to each antibiotic tested. This is a yearly summary and it allows you to trend resistance patterns over time. It also is a tool for clinicians and pharmacist to use to select the best empiric antibiotic treatment when microbiology culture and susceptibility results are pending.

Access the resource titled About Antibiograms (Antimicrobial Susceptibilities of Selected Pathogens) from the Minnesota Department of Health.

Access AHRQ's Concise Antibiogram Toolkit.

 How can you prevent the development and spread of antibiotic resistance?

You cannot prevent the development of all resistance, as it is a naturally occurring phenomenon. Your real job is to slow development and reduce the spread of antibiotic resistant bacteria.

Effective diagnosis and treatment, including the judicious use of antibiotics, is a key part of preventing antibiotic resistance. Refer to the session Antibiotic Stewardship for strategies to support the judicious use of antibiotics.

Another key component to prevent further emergence and spread of antibacterial resistance is through infection prevention and control practices.

While much broader than the spread of antibiotic resistance, read SHEA/APIC Guideline: Infection Prevention and Control in the Long-Term Care Facility.

The guideline from SHEA and APIC describes the elements of a Long-Term Care Facility Infection Control Program, including infection control activities such as establishing and implementing routine infection control policies and procedures and infection identification. Also included are identification, investigation, and control of outbreaks such as organism-specific infection control policies and procedures, disease reporting, antibiotic stewardship, monitoring of patient care practices, facility management issues, product evaluation, resident health programs, and employee health programs.

Key examples provided by SHEA and APIC of infection control and prevention activities include hand hygiene, standard precautions, organism-specific isolation, employee education, developing case definitions of infections, reviewing antibiotic use, and facility maintenance and cleaning and sanitation procedures.

Also see the four-part webinar series in the session Clostridium difficile Part Two: Strategies to Prevent, Track, and Monitor C. difficilethat discusses how MDROs and C. difficile emerge and spread and actions that caregivers can take to minimize their spread.


Discussion questions: To gain situational awareness of antibiotic resistance in your organization, discuss the following questions with your laboratory:

  1. How many fluroquinolone resistant organisms have been detected in your residents' urine cultures in the past six months?
  2. How many methicillin resistant stahpyloccous organisms have been detected in your residents' cultures in the past six months?
  3. How does the lab identify carbapenemases and how do they or can they notify you when carbapenem resistant organisms have been detected in your cultures?

 Take Home Messages

  • Antibiotic resistance is a growing problem across all healthcare settings. This is happening on our watch – and it is our problem to address as well.
  • The fewer antibiotics we use (avoiding abuse or misuse), the slower antibiotic resistance will be to develop, and the result will be that we will have antibiotics available to us when we need them.
  • Infection control is a key component to prevent emergence and spread of antibacterial resistance. Understanding how MDROs and C. difficile emerge and spread can focus infection prevention at the bedside.

The Minnesota Department of Health

These education modules were developed for nurses and for nursing assistants on antibiotic use and antibiotic resistance:

What Do We Do When Antibiotics Don’t Work Anymore? by Maryn McKenna (16:59)

Watch this TED Talk with Maryn McKenna, public health journalist.

Preventing the Spread of Carbapenem-resistant Enterobacteriaceae in LTCFs

Watch this recorded webinar presented by Dr. Nimalie Stone, a medical officer at the Centers for Disease Control and Prevention (CDC) (1:00:29). This webinar is presented by the Lake Superior Quality Innovation Network.

Presentation objectives:

  • Review the importance of carbapenem-resistant Enterobacteriaceae (CRE).
  • Describe the strategies outlined in the CDC’s CRE Tool-kit to detect and prevent CRE.
  • Discuss approaches that LTCFs can take to implement CRE prevention activities.

For the presentation slides: PDF

The Basics of Antibiotic Resistance: Focus on Carbapenem-Resistant Enterobacteriaceae (CRE)

For more information on CRE, watch this recorded webinar presented by Dr. Nimalie Stone, a medical officer at the Centers for Disease Control and Prevention (CDC) (56:54). This webinar is presented by the Lake Superior Quality Innovation Network.

Presentation objectives:

  • Review common bacteria identified in nursing homes and antibiotics used to treat them.
  • Describe mechanisms for antibiotic resistance to develop in bacteria including carbapenem-resistance.
  • Discuss ways your laboratory can provide information about antibiotic resistance to your facility.

For the presentation slides: PDF

Environmental Hygiene: Best Practices to Use When Cleaning and Disinfecting Patient Rooms

This video, available in English and Spanish, is intended to compliment the infection prevention education program in healthcare organizations. It was developed by the Oregon Patient Safety Commission and the Oregon Healthcare-Associated Infection Program at the Oregon Health Authority.