Introduction

• Hospital-associated, or nosocomial, infections are infections that occur in response to hospitalization.
• Hospital-associated infections (HAIs) may be endogenous or exogenous.
• They may develop from the endogenous flora of the patients or from exogenous microorganisms acquired from the environment or other animals or personnel during hospitalization.
• Infections are considered as hospital-associated if they first appear 48 hours or more after hospital admission or within 30 days after discharge. This cutoff is somewhat subjective, but it is widely used in human and veterinary medicine to determine the source of infections once hospitalized.
• Not all infections that develop during hospitalization are hospital-associated. Some dogs maybe incubating community-associated infections, which are expressed after admission.
• Generally, infections that occur within 48 h of admission to a hospital are considered community-associated, however it is possible that some hospital-associated infections could develop within this timeframe and that some community-associated infections could take longer to develop.
• Similarly, not all hospital-associated infections are noticed during hospitalization. Dogs can be infected while in hospital but not develop clinical signs of infection until after discharge. Typically, infections that occur within a certain period of time (~30 days) of discharge from hospital are considered hospital-associated/community-onset infections.
• Hospital-associated infections are of particular concern because the patients immunity may be compromised by underlying disease, drugs, surgery, invasive supportive care, malnutrition or stress.
• Dogs can be exposed to a variety of infectious agents in veterinary hospitals including those from contaminated environments, veterinary personnel or other infected animals.
• Hospital-associated infections are an inherent risk of hospitalization. Development of a hospital-associated infection does not necessarily indicate a poor quality veterinary clinic. A certain percentage of hospital-associated infections are considered non-preventable and would occur despite the best infection control program. Infection control programs are designed to reduce the preventable fraction of hospital-associated infections.
• Organisms endemic to the hospital environment often show multiple drug resistances Resistant bacterial infections and may lead to outbreaks of infection. Examples include multi drug resistant E.coli Escherichia coli , Clostridium difficile Clostridium difficile and methicillin-resistant Staphylococcus aureus (MRSA) Methicillin-resistant Staphylococcus aureus MRSA infection and methicillin-resistant Staphylococcus pseudintermedius (MRSP) Meticillin-resistant Staphylococcus pseudintermedius.
• Hospitals for all species, contain individuals of varying levels of susceptibility and animals are often crowded together in a situation in which they are likely to encounter agents of infectious disease.
• For details of biosecurity and infection control procedures used in small animal hospitals, see Biosecurity and Infection control Biosecurity and infection control.
• Hospital-based human epidemics of staphylococcal infections, including multi-resistant strains, have been reported since the 1950s and encouraged the development of hospital infection control policies.
• Hospital-associated infections are an important cause of morbidity and mortality in humans. As medical advances in human medicine lead to increased survival from serious diseases, there still remains those that are immunocompromized and with increasing numbers of hospital visits, hospital-associated infections become a greater risk.
• Similarly, advances in small animal medicine have resulted in more invasive procedures, such as intravenous and urinary catheters, advanced surgical procedures, an increase in duration of hospitalization, an increase in intensive care practices, and the increased use of antimicrobial drugs Therapeutics: antimicrobial drug , all of which inherently increase the risk of hospital-associated infection.
• Many different organisms have been implicated in hospital-associated infections of dogs. Some are thought to be intrinsically pathogenic, such that a certain number of animals exposed to the pathogen will develop clinical signs, eg Salmonella spp Salmonella spp , which can exist in a small number of carrier animals but can cause clinical illness in a proportion of the population, particularly in stressed animals.
• Other organisms that might be considered normal resident flora on the skin, in the upper respiratory tract, or in the gastrointestinal tract can become pathogens that is if they gain access to normally sterile parts of the body, if they become a dominant organism (as in bacterial overgrowth), or if they are resistant to antimicrobial drugs.
• Common nosocomial infections in the veterinary hospital include urinary tract infections, surgical wound infections and infectious diarrhea.
• Although the control of infectious diseases in small animal hospitals was initially focused on contagious infectious diseases, such as canine parvovirus Parvovirus disease associated with CPV-1 , more recently control of zoonotic infectious diseases such as MRSA have taken precedent.
• Some hospital-associated infections are highly contagious, often brought in by infected dogs, and appear as epidemics, eg canine parvovirus and Kennel cough (Bordetella bronchiseptica) Acute infectious tracheobronchitis.
• Others are caused by agents already present in dogs and veterinary personnel and which can contaminate the hospital environment, eg MRSA and C. difficile and MRSP. However, the zoonotic risk of the latter is relatively low.
• Many of the problems found in small animal hospitals are similar to, and have similar risk factors to those widely reported in human hospitals, such as nosocomial infections involving MRSA, C. difficile and extended spectrum beta lactamase (ESBL) producing bacteria such as E.coli.
• ESBLs are enzymes produced by gram negative bacteria that have developed resistance to antibiotics, such as cephalosporins and through genetically linked resistance mechanisms they are often resistant to other antibacterials including quinilones and aminoglycosides.

Surveillance and monitoring of hospital-associated infections

Hospital-associated infections in small animal practice

Hospital-associated post-operative wound infections

Hospital-acquired urinary tract infections

Hospital-associated blood-stream infections

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Gibbs E P, Anderson T C (2010) Equine and canine influenza: a review of current events. Anim Health Res Rev 11 (1), 43-51 PubMed.
• Gibson J S, Morton J M, Cobbold R N et al (2010) Risk factors for multidrug-resistant Escherichia coli rectal colonization of dogs on admission to a veterinary hospital. Epidemiol Infect 139 (2), 197-205 PubMed.
• Gibson J S, Cobbold R N, Trott D J (2010) Characterization of multidrug-resistant Escherichia coli isolated from extraintestinal clinical infections in animals. J Med Microbiol 59 (Pt 5), 592-598 PubMed.
• Walther B, Wieler L H, Friedrich A W et al (2009) Staphylococcus aureus and MRSA colonization rates among personnel and dogs in a small animal hospital: association with nosocomial infections. Berl Munch Tierarztl Wochenschr 122 (5-6), 178-185 PubMed.
• Weese J S, Finley R, Reid-Smith R R et al (2009) Evaluation of Clostridium difficile in dogs and the household environment. Epidemiol Infect 138 (8), 1100-4 PubMed.
• Clooten J, Kruth S, Arroyo L et al (2008) Prevalence and risk factors for Clostridium difficile colonization in dogs and cats hospitalized in an intensive care unit. Vet Microbiol 129 (1-2), 209-214 PubMed.
• Gibson J S, Morton J M, Cobbold R N et al (2008) Multidrug-resistant E. coli and enterobacter extraintestinal infection in 37 dogs. J Vet Intern Med 22 (4), 844-850 PubMed.
• McLean C L, Ness M G (2008) Meticillin-resistant Staphylococcus aureus in a veterinary orthopaedic referral hospital: staff nasal colonisation and incidence of clinical cases. JSAP 49 (4), 170-177 PubMed.
• Lefebvre S L, Waltner-Toews D, Peregrine A S et al (2006) Prevalence of zoonotic agents in dogs visiting hospitalized people in Ontario: implications for infection control. J Hosp Infect 62 (4), 458-466 PubMed.
• Leonard F C, Abbott Y, Rossney A et al (2006) Methicillin-resistant Staphylococcus aureus isolated from a veterinary surgeon and five dogs in one practice. Vet Rec 158 (5), 155-159 PubMed.
• Ogeer-Gyles J, Mathews K, Weese J S et al (2006) Evaluation of catheter-associated urinary tract infections and multi-drug-resistant Escherichia coli isolates from the urine of dogs with indwelling urinary catheters. J Am Vet Med Assoc 229 (10), 1584-1590 PubMed.
• Ogeer-Gyles J, Mathews K A, Sears W et al (2006) Development of antimicrobial drug resistance in rectal Escherichia coli isolates from dogs hospitalized in an intensive care unit. J Am Vet Med Assoc 229 (5), 694-699 PubMed.
• Wright J G, Tengelsen L A, Smith K E et al (2005) Multidrug-resistant Salmonella Typhimurium in four animal facilities. Emerg Infect Dis 11 (8), 1235-1241 PubMed.
• Eugster S, Schawalder P, Gaschen F et al (2004) A prospective study of postoperative surgical site infections in dogs and cats. Vet Surg 33 (5), 542-550 PubMed.
• Johnson J A (2002) Nosocomial infections. Vet Clin North Am Small Anim Pract 32 (5), 1101-1126 PubMed.
• Sanchez S, McCrackin Stevenson M A, Hudson C R et al (2002) Characterization of Multidrug-Resistant Escherichia coli Isolates Associated with Nosocomial Infections in Dogs. J Clin Microbiol 40 (10), 3586-3595 PubMed.
• Bodey G P, Bolivar R, Fainstein V et al (1983) Infections caused by Pseudomonas aeruginosa. Rev Infect Dis 5 (2), 279-313 PubMed.

Other sources of information

• BSAVA practice guidelines - reducing the risk from MRSA and MRSP: http://www.bsava.com/Advice/MRSA/tabid/171/Default.aspx
• Nuttall T (2011) Meticillin-resistant staphylococci in companion animals: http://www.bsava.com/Advice/MRSA/Meticillinresistantstaphylococciinanimals/tabid/1469/Default.aspx