How to Deal with Infections
World Small Animal Veterinary Association World Congress Proceedings, 2014
Mirinda van Schoor, BVSc, BVSc (Hons), MMedVet (Medicine)
Onderstepoort Veterinary Academic Hospital, Onderstepoort, South Africa

In veterinary practice, patients can present with infections as the primary disease, or they could acquire infections during hospitalization. These hospital acquired infections are called nosocomial infections (NIs). In humans, 5–10% of patients develop NIs during their stay in hospital.1 In veterinary medicine, 82% of teaching hospitals reported outbreaks of NIs with 45% of hospitals reporting more than one outbreak in a 5 year period.1 The most common NIs include urinary tract infections, pneumonia, surgical site infections and blood stream infections. Most of these patients will need management as prescribed for patients at risk of or suffering from the systemic inflammatory response syndrome, which can be found elsewhere in the literature.2 The veterinary technician or nurse needs to know how to identify, manage and prevent NIs to decrease morbidity and to ensure optimal chances of survival for each patient.

Catheter-associated urinary tract infections (CAUTIs) are the most common NIs seen and can occur in 10–38% of hospitalized canine patients.1 It seems to make sense that CAUTIs would be more common when an open urine collection system is used; however, it was shown that even with closed collection systems the incidence of bacterial infections can reach 52% of cases.1 It was proven that CAUTIs were not more common in cases where open rather than closed collection systems were used.1 Where strict hygiene protocols were adhered to during placement and management of urinary catheters and where duration of catheterization was as short as possible, closed and open systems were equal as far as CAUTIs were concerned.1 CAUTIs occur due to the fact that placement of urinary catheters interferes with normal defence mechanisms (which usually prevent bacterial colonization) as well as development of biofilms consisting of clusters of microorganisms and extracellular matrix that adhere to the surfaces of catheters.1 CAUTIs are diagnosed based on culture of a urine sample collected via sterile cystocentesis.1 Antibiotic use must be based on results of an antibiogram in all cases of NIs, as many antibiotic-resistant bacteria have evolved.3,4 The urinary catheter has to be removed1 because of the biofilm that will protect the bacteria from antibiotic activity and act as a reservoir for continued bacterial growth. Because of the risk of CAUTIs, urinary catheterization must be avoided unless it is absolutely necessary, such as in cases where urine output needs to be monitored accurately or where anatomic or functional obstruction of urine outflow is present.1 The catheter is left in place only for as long as it is absolutely required, and sterile placement and management is of utmost importance.1,4 The collection system needs to be kept below the level of the patient to prevent retrograde flow of urine. Because urine within the collection system is deemed contaminated, the system should not be flushed.

Hospital-acquired pneumonia (HAP) develops more than 48 hours after admission to hospital1 and is more common in ventilator patients. HAP usually results from aspiration of pathogens. The use of gastric ulcer prophylaxis lead to increased colonization of the oropharynx with gram-negative bacteria and increase the risk of HAP in humans.5 A study in dogs with HAP revealed that half the patients were receiving H2 blockers as ulcer prophylaxis, so it may be possible that this risk factor occurs in small animal patients as well.

The use of endotracheal tubes and feeding tubes increases the risk of HAP by acting as physical portals for introduction of microorganisms to the lower respiratory tract.1 Disorders that affect the functioning of the larynx and oesophagus also increase the risk of HAP. Patients with decreased neurological function, patients receiving heavy sedation, and patients with a history of anaesthesia are predisposed to aspiration and HAP.1 Diagnosis is based on clinical signs, radiographic changes and culture of samples collected from the lower respiratory tract via broncho-alveolar lavage.1

Surgical site infections (SSIs) can complicate management of small animal patients and increase hospital stay and mortality. SSIs are largely influenced by the duration of the surgery. In humans, SSIs nearly double with every hour spent in surgery.1 Pathogens originate from the patient's own endogenous skin micro-flora, mucus membranes or hollow organs. In veterinary patients, males seem to be at higher risk for SSIs, and patients with concurrent endocrine diseases are also more likely to develop SSIs.1 Prophylactic antibiotics are commonly used in surgical patients.1,4 It is important to limit their use to the immediate perioperative period. If animals received prolonged prophylactic antibiotics, they had an increased rate of infection.1 Treatment with antibiotics is based on culture and antibiogram of a sample collected during definitive surgical treatment of the SSI. Surgery enables removal of necrotic tissue and reduces the microorganism load.1 Preventing SSIs is achieved by clipping the surgical site after induction of anaesthesia. It was shown that prepping the area the night before surgery caused colonisation of the damaged epithelial surface with bacteria, increasing the rate of SSIs.1 Maintaining a sterile operating environment and keeping surgical times as short as possible will also help prevent SSIs.

Bloodstream infections (BSIs) could result from introduction of microorganisms via intravenous catheters.1 The risk of BSIs is greater with central venous catheters (CVC).1 BSIs are very serious infections with sometimes very high mortality rates (up to 25%). The biggest contributor to BSIs is prolonged duration of catheterization.1 Most BSIs that are associated with catheters develop within 4–5 days after catheter placement. Between 15 and 48% of critically ill dogs had bacterial colonization of their catheters. In veterinary patients, the bacteria isolated in cases of BSI are usually enteric or environmental contaminants.1. If a BSI is suspected, the catheter should be removed. Sterile technique should be used during removal, and the catheter tip should be sent for bacterial culture and antibiogram. Blood samples from central and peripheral veins should be collected aseptically and sent for bacterial culture. While awaiting culture and antibiogram results, the patient must be placed on broad-spectrum antibiotics. Unfortunately, antibiotic resistance against many antibiotics exist,3 and very careful antibiotic selection is essential, especially with BSIs.1 To prevent BSIs, it is important to use aseptic technique when placing intravenous catheters.1 Chlorhexidine solutions were found to be the most effective antiseptic solution to use as part of skin preparation prior to catheter placement.1 Alcohol and chlorhexidine may have synergistic effects against bacterial activity, making a mixture of these two solutions ideal to use in a hospital setting. Dressings at the catheter site must be replaced every 2 days to decrease bacterial colonization. Although human studies found that prolonged catheterization increased the risk of BSI, a study showed that changing the catheter every 3 days versus every 7 days made no difference in the bacterial colonization of the sites. In veterinary medicine, it was shown that catheters, even in peripheral veins, can be left in place for up to 10 days if strict aseptic catheter placement and meticulous catheter management and dressing changes are adhered to.1

Other measures that must be kept in mind when attempting to limit or eliminate nosocomial infections include things like maintaining a sterile consulting, hospital and operating environment. This topic forms part of a different lecture presented at this congress ("Maintaining a sterile operating environment" - Martin Kessler). Another important aspect is the correct use of antibiotics.3 This topic is addressed in a separate lecture during this congress ("The ABC of antibiotics" - Alain Carter). One of the most important measures that can be implemented in the fight against NIs is hand hygiene.1,4 The hands of health workers are often identified as the source of NIs. Clinicians, technicians and nurses touch patients as well as inanimate objects from where bacteria are transferred to the environment and to other patients. Even "clean" actions, such as taking a patient's pulse or blood pressure or moving a patient and taking them for a walk, may cause contamination of the hands. Hand washing removes visible dirt from the hands, and antiseptic soaps reduce the bacterial load on the hands, but the use of alcohol-based hand rubs has been shown to be superior in reducing the bacterial load on the skin.1 It is therefore accepted as the standard of care as far as hand hygiene is concerned. Paying attention to hand hygiene is important both before and after touching a patient, before handling any invasive device such as catheters, after contact with body fluids, wounds and mucus membranes, after contact with the environment, and after removing gloves.1 Unfortunately, less than 50% of small animal veterinarians wash their hands between patients. If we improve hand hygiene, we will be able to dramatically reduce NIs in our hospitals. Once a patient is discharged, it is important to ensure that the owner completes the course of the prescribed antibiotics in an attempt to decrease the number of antibiotic-resistant bacteria.3 Owners need to be briefed on the importance of correct antibiotic use and reasons for giving certain doses for certain periods of time. These measures will decrease the incidence of future NIs.

References

1.  Nakamura RK, Tompkins E. Nosocomial infections. Compend Contin Educ Vet. 2012;34(4):E1–E11.

2.  Randels A. Systemic inflammatory response syndrome. Vet Tech. 2013;February:E1–E6.

3.  Murphy M. Antibiotic resistance in veterinary medicine. VNJ. 2012;27(11):422–423.

4.  Johnson A. Nosocomial infections. Vet Clin North Am Small Anim Pract. 2002;32(5):1101–1126.

5.  Ruple-Czerniak A, Aceto HW, Bender JB, Paradis MR, Shaw SP, van Metre DC, et al. Using syndromic surveillance to estimate baseline rates for healthcare-associated infections in critical care units of small animal referral hospitals. J Vet Int Med. 2013;27:1392–1399.

  

Speaker Information
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Mirinda van Schoor, BVSc, BVSc (Hons), MMedVet (Medicine)
Onderstepoort Veterinary Academic Hospital
Onderstepoort, South Africa


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