During the mid-1800s, Louis Pasteur led the medical profession in the discovery of microbes as a cause of disease and introduced the principles of aseptic technique with the suggestion that ‘instead of fighting bacteria, would it not just be better not to introduce them?’ After the discovery of antibiotics in 1945, this focus on prevention measures seemingly lapsed due to the apparent ease in which infections could be treated, but with the emergence of antibiotic resistance in the late 20th and early 21st centuries and no new antibiotics on the horizon, infection prevention is at the forefront once again (Verwilghen and Singh, 2015).
In parallel to the human healthcare profession, multidrug resistant bacterial infections are an important problem within veterinary medicine. Currently, the major organisms of concern include meticillin-resistant Staphylococcus pseudintermedius (MRSP), meticillin-resistant Staphylococcus aureus (MRSA), extended-spectrum β-lactamase (ESBL) Escherichia coli, enterococci and Pseudomonas aeruginosa (Guardabassi and Prescott, 2015). The close relationship between pets and owners has also raised concerns regarding interspecies transmission of resistant bacteria. Antibiotic-resistant strains of bacteria isolated from small animals often are indistinguishable from strains isolated from people caring for these animals; O'Mahony et al (2005) identified that the most frequently occurring pattern of MRSA in veterinary sources was the same as the most prevalent strain identified in the human population. Responsible antibiotic use in both fields is therefore important to help preserve the efficacy of antibiotics for humans and animals alike.
Veterinary hospitals can serve both as a point of origin and as a reservoir for multi-drug resistant organisms (MDROs). Hospitalised patients that may be highly susceptible to infections are subjected to an environment where infectious agents are continuously under heavy antibiotic pressure and failure of infection control practices can thus result in cross-infection and outbreaks of nosocomial infections with MDROs (Damani and Emmerson, 2003).
Antibiotic resistance
Mechanisms for antibiotic resistance may be categorised as intrinsic resistance or acquired resistance (Umber and Bender, 2009). Some bacteria are inherently resistant to certain antibiotics due to structural or functional characteristics that mean the drug cannot penetrate the cell or the bacteria lack the required target sites (Wilson, 2006). This is caused by naturally occurring genes within the organism's DNA and is known as intrinsic resistance.
Initial emergence of acquired resistance among a bacterial population is random, arising by mutations of genetic material (errors as DNA is copied in bacterial replication) (Department of Health, 2013). Genes that encode for resistance determinants are then transferred between organisms via plasmids, bacteriophages, transposons, and other mobile genetic material (Umber and Bender, 2009).
The organism may acquire the ability to destroy the antibiotic by hydrolysis or modification, mutate its target site so that it is no longer recognised by the antibacterial agent or increase the activity of bacterial efflux pumps which actively transports certain antibiotics back out of the cell (Blair et al, 2015).
Resistance can occur through several mechanisms including:
Pathogens associated with nosocomial infections have been found to accumulate factors conferring antibiotic resistance, suggesting an adaptation to the hospital environment (Walther et al, 2017).
Exposure to antibiotics favours survival of organisms carrying the resistance genes so that antibiotics exert selection pressure that allows these genes to spread within the population. This selection pressure is exerted on both pathogenic and commensal bacteria, and organisms that may not have been the intended target of antibiotic treatment may acquire resistance (Wilson, 2006).
Why is antibiotic resistance a problem?
Infections caused by MDROs result in prolonged illness, high treatment costs, increased risk of death and longer periods of infectivity due to treatment failures (WHO, 2011). Veterinary hospitals affected by outbreaks of infections associated with MDROs may be implicated economically by reduced revenue resulting from measures required to control the infection such as ward closures, restricted patient admissions, decontamination and intensive surveillance procedures. Development of new antibiotic agents has been slow over the past few decades, with no new class found since 1987. Those that have been produced, are reserved for human use, making the need to preserve the efficacy of veterinary antibiotic products all the more crucial (Guardabassi and Prescott, 2015).
Antibiotic guardianship
While veterinary nurses have no prescribing power, they can play a vital role in promoting the responsible use of antibiotics. Registered veterinary nurses (RVNs) are well placed to ensure appropriate delivery of antimicrobials, educate owners about antibiotic usage, and implement infection control practices to minimise the need for antibiotics. Among other professionals in the medical, veterinary and farming sectors, RVNs are invited to pledge to become ‘antibiotic guardians’ as part of a ‘keep antibiotics working’ campaign led by Public Health England. This campaign aims to promote responsible antibiotic usage among animals and humans alike and encourages focus on good biosecurity and husbandry practices as opposed to reliance on antimicrobial drugs. Suggested pledges for members of the veterinary profession are shown in Box 1.
Pet owners and farmers are also encouraged to become antibiotic guardians by pledging to follow veterinary advice and respect their veterinary surgeon's decision if antibiotics are not considered necessary.
Appropriate delivery of antibiotics
Careful selection and appropriate use of antibiotics are vital steps in combating development of MDROs. Therapy should be targeted at maximising clinical efficacy and minimising selection of resistant organisms (Clarke, 2006). Where possible, in vitro sensitivity testing and pharmacokinetic data should be used to guide drug choice, favouring narrow-spectrum agents where possible, and antibiotics should not be administered until a bacterial infection is confirmed, except when severe sepsis is suspected and therapy cannot be delayed (Stull and Weese, 2015).
Decision making when prescribing antibiotics must be multi-factored. The clinician should weigh up the benefits and risks, taking into account the risks of suppression of normal flora, development of resistance in normal flora as well as pathogenic bacteria and achievable antibiotic concentration at the specified site of infection based on the required minimum inhibitory concentration (WHO, 2011).
RVNs are often responsible for ensuring timely and accurate administration of antibiotics to hospitalised patients and should have a good understanding of the correct dose, route of administration, potential side effects and drug–food interactions that may affect drug absorption and influence timing of administration in relation to feeding (Welling, 1996).
It is often a RVN who dispenses medications to pet owners. It is important to ensure that the owner understands how and when to administer antibiotics correctly and is well informed about the need to complete the prescribed course and avoid missed doses. Owners frequently misinterpret the improvement of their pet's symptoms as a cue to stop giving antibiotics or their decreasing worry as their pet appears to return to health means that medication administration becomes overlooked. RVNs must emphasise the problems associated with incomplete antibiotic therapy to increase owner compliance.
Managing owner expectations
Owners often expect a quick, cheap fix for their pet's condition. Cost implications and time constraints are common factors in clinical decision making, and under pressure from the client and a busy waiting room, the cheapest, easiest treatment may appear to be administration of a short course of a broad spectrum antibiotic. A discussion must be had with the owner to educate them about antibiotic resistance and the effects of administering the wrong antibiotics.
An important approach to combating antibiotic resistance which VNs can play a vital part in is educating owners on how maintaining a holistic approach to pet health will prevent the need for antibiotics and hospital stays, particularly with respect to good nutrition to promote an effective immune system, vaccination against all preventable diseases (including kennel cough), parasite control, general hygiene principles and neutering to prevent conditions such as pyometra and transmission of diseases such as feline immunodeficiency virus (FIV).
The responsibility of antibiotic guardianship is not limited to preventing the spread of resistant bacteria within the hospital. While patients with MDROs should be discharged from the hospital as soon as possible, it is important to ensure that isolation and necessary infection prevention measures are continued at home. Fact sheets and verbal consultations are important tools in informing owners of the necessary precautions to minimise the spread of resistant bacteria into the wider community. Owners should be instructed to minimise contact of the infected patient with other animals (particularly if they utilise dog walking services, kennel facilities etc.) until treatment is completed and to ensure good hygiene practices such as hand washing etc. after handling their pet. Owners must be also aware of the potential risks to themselves and other family members, particularly those who may be immunocompromised, and should be advised to seek medical advice if they have any concerns (Umber and Bender, 2009).
Biosecurity
The probability of a patient developing a nosocomial MDRO infection depends on many factors including the virulence of the agent, the susceptibility of the patient to that particular organism, the amount and route of exposure, the performance of invasive procedures, and prior antibiotic therapy. MDROs may originate from the patient themselves, whereby a change in their normal bacterial flora has allowed resistant bacteria to flourish, or the organism may have been transferred to the patient through contact with fomites (e.g. stethoscopes, food bowls and other devices), veterinary staff (specifically via the hands) and surfaces that can harbour resistant bacteria (Umber and Bender, 2009).
Development, maintenance and review of practice infection control policies often falls to VNs. Effective infection prevention measures significantly reduce the risks of nosocomial infections and infection control policies in the veterinary setting should be tailored to the individual practice, reflecting the pathogen risks, facility and staff characteristics and the patient population. Practices should have clear written guidelines to ensure consistency and policy compliance across the hospital (Stull and Weese, 2015). These should be carefully planned to ensure that hospital layout and facilities are utilised in the best way possible and that cleaning schedules appropriately reflect the traffic and usage levels and function of different areas of the practice and equipment.
Factors that favour the acquisition of antibiotic resistant infections include hospitalisation, use of invasive medical devices such as intravenous catheters or indwelling urinary catheters, surgical procedures and immunocompromise (Umber and Bender, 2009). Longer duration of hospitalisation increases opportunities for exposure and patients should be discharged as soon as they are deemed fit enough. The use of invasive devices provides a route of entry for microorganisms that circumvents the body's natural defence mechanisms. Invasive devices should be removed as soon as they are no longer required; leaving them in ‘just in case’ can have deleterious consequences. Immunocompromised patients are more susceptible to opportunistic infections and require additional precautions to protect them from bacteria in the environment.
The fundamental aim of infection prevention is to prevent the physical translocation of microbes between patients, staff and the environment (Anderson, 2015). Infection control measures can be broken down into three categories:
Hand hygiene is one of the most important measures in preventing the spread of MDRO infections. The goal is to reduce the transient superficial microbiota of the hands that may then be transferred to other surfaces or individuals. This may be accomplished by physically removing the microbes from the skin or by neutralising them with antimicrobial handrubs (Anderson, 2015).
Although poorly understood, it has been recognised that it may be possible for bacteria to acquire resistance to disinfectant agents via similar mechanisms to those pertaining to antibiotic resistance (Russell, 2002). It is therefore vital to ensure that the manufacturer's guidelines for dilution rates and contact times are followed to prevent selection for resistant strains of bacteria by inappropriate disinfection use.
Biosecurity protocols are required under the Royal College of Veterinary Surgeons (RCVS) Practice Standards scheme (RCVS, 2017) and most practices will have their policies documented and displayed within the practice. Stating what should be done and doing what is stated however do not always go hand in hand in a busy hospital and monitoring and enforcing compliance with practice policies is essential to make them worthwhile.
Surveillance of hospital associated infections
As a discipline, veterinary infection control is relatively new and there are very limited data on which to base infection control strategies (Burgess, 2015). Combined with the fact that each hospital will have its own specific infection prevention requirements based on geographic location, pathogen risks, patient population and the types of procedures carried out, this means that practices should use their own microbiologic data surveillance to monitor trends in resistance patterns and detect causes of nosocomial infections. Infection control policies should be reviewed regularly and effective surveillance will enable appropriate adjustments to be made where necessary.
Surveillance methods should include outcome-based methods, which document rates and potential contributing factors for adverse outcomes (such as surgical site or catheter site infections or outbreaks of diseases within a practice such as kennel cough etc.), process-based methods, which monitor practices such as antibiotic prescribing and adherence to infection control policies, and microbiologic data surveillance which observes trends that might suggest cross-contamination between patients (Burgess, 2015). The most feasible method of microbiologic data surveillance involves collating information from all culture and sensitivity reports and reviewing organisms with similar resistance profiles with respect to the date of sampling, proximity of patients and opportunities for cross-contamination.
Table 1 shows an example of data that might be collated as part of an outcome-based surveillance programme for surgical site infections.
| Date of culture | Patient name and number | Breed | Organism | Resistance to | Surgery | Surgical team | Date and time of surgery | Theatre no. | Duration of surgery | Duration of anaesthesia | Patient temperature range during anaesthesia | Kennel number | Perioperative/Postoperative antibiotics |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 01/01/2017 | Billy Smith 12345 (example) | JRT | Staphylococcus | Amoxycillin Gentamycin Marbofloxacin Fusidic acid | TPLO | Surgeon Assistant RVN | 01/06/2016 | 1 | 60 mins | 120 mins | 36.9 to 38.6°C | Surgery ward no. 4 | Cefuroxime 22mg/kg q2hours periop Cephalexin 20mg/kg BID 5 days postop |
Infection control teams are well established within human healthcare, but in veterinary practices staff generally take on the responsibility of overseeing infection control as a supplementary role, if any provision is made at all. Ideally, a designated person should be in charge of overseeing infection prevention efforts and surveillance and regular meetings should be held with stakeholders to facilitate discussion of findings and proposals for changes to infection control practices (Burgess, 2015).
Conclusion
Safeguarding the continued use of antibiotics in veterinary medicine and preventing outbreaks of MDRO infections within veterinary hospitals go hand in hand. A collaborative approach between veterinary surgeons and RVNs to ensure responsible antibiotic usage and proactive biosecurity practices is paramount to minimise the development of antibiotic resistance.