Nosocomial Infections and Zoonoses

Chapter 12 Nosocomial Infections and Zoonoses



Shelley C. Rankin, PhD



Key Points



• Nosocomial (hospital acquired) infection is defined as any infection that is neither present nor incubating when a patient is admitted to a hospital.

• Risk factors for nosocomial infection in the intensive care unit (ICU) include severity of underlying illness, prolonged length of stay, mechanical ventilation, and indwelling devices.

• Multiple antibiotic resistance is common among nosocomial pathogens.

• Methicillin-resistant Staphylococcus aureus is an emerging disease in dogs and cats.

• Zoonosis is a disease that can be transmitted from animals to humans. A more technical definition is a disease that normally exists in animals but that can infect humans.

• The reservoirs of nosocomial pathogens include people, animals, fomites, air currents, water and food sources, insects, and rodents, and it has long been known that the spread of pathogens in hospitals occurs primarily via the hands of personnel.

• Establishment of nosocomial infection control committees must become a priority in veterinary hospitals.


INTRODUCTION


In human health care settings, nosocomial infection is defined as any infection that is neither present nor incubating when a patient is admitted to a hospital. In 1988, the Centers for Disease Control and Prevention proposed more specific definitions, and it is now generally accepted that infections are considered to be nosocomial if they develop at least 48 hours after hospital admission without proven prior incubation.1 In addition, if infections occur up to 3 days after discharge or within 30 days of a surgical procedure, they are attributed to the admitting hospital.1 These definitionsare largely accepted in human health care and, although they may require refinement in veterinary medicine, they stand unchallenged.


It is well recognized that hospitalization of sick animals can lead to an increased risk of infection, and various policies have been proposed to reduce the risk of nosocomial infection in veterinary medicine.2,3 In addition to patient care concerns, many nosocomial pathogens are well recognized as zoonotic agents, so infection control policies should address the issue of animal to human transmission.2



NOSOCOMIAL INFECTIONS IN DOGS AND CATS


One of the first published reports of nosocomial infection in a veterinary hospital described Klebsiella infection in dogs and one cat in the ICU at the New York State College of Veterinary Medicine in 1978.4 Since that time there have been a few well-characterized studies, but many of these have centered on large animal facilities with various Salmonella enterica serotypes as the causative organisms.5-7 Specific reports of nosocomial infection in dogs and cats remain limited.5 Since 1978, organisms such as Serratia marcescens, Salmonella spp, Clostridium perfringens, Acinetobacter baumannii, Escherichia coli, and Clostridium difficile have been implicated as causes of nosocomial infection in dogs and cats.5,8-12 The bacteria responsible for nosocomial infection in ICUs originate either from the patient’s own endogenous flora or from exogenous sources. Nosocomial infections derived from endogenous flora may occur in patients receiving chemotherapy, glucocorticoid therapy, or antibiotic therapy. In contrast to endogenous infections, exogenous infections are more likely to be preventable by standard or specific precautions devised to reduce the overall rate of transmission.13 A review of nosocomial infections in veterinary medicine provides data on the prevalence of urinary tract infections, surgical site infections, bloodstream infections, pneumonia, and diarrhea.14



RISK FACTORS


Although ill defined in veterinary medicine, independent risk factors for nosocomial infection acquisition in the critically ill patient can be extrapolated from human studies. Prolonged length of hospital stay, mechanical ventilation, and indwelling devices, such as intravascular or urinary catheters and nasogastric or endotracheal tubes, are well-recognized risk factors.1 Many intrinsic, patient-related factors have also been identified and include patient demographics (e.g., age, gender), comorbidities, and severity of underlying illness, which is the most widely reported risk factor. Patient-specific risk factors are related to general health and immune status, respiratory status, neurologic status, and fluid status. A significant risk factor in the ICU is trauma, especially when associated with open fractures. Several less well-acknowledged factors have also been suggested as contributing factors. Among them, understaffing and overcrowding in the ICU have been well documented as causes of cross-transmission of nosocomial infections.1



MULTIPLE ANTIBIOTIC-RESISTANT NOSOCOMIAL PATHOGENS


In an excellent review of the problem of antimicrobial drug use and resistance in veterinary medicine, Prescott and colleagues state that, “Despite a possible wealth of data in filing cabinets in veterinary clinical microbiology laboratories around the world, there have been virtually no systematic investigations of changes in antimicrobial drug resistance in bacteria isolated from companion animals over time, using standard methodologies for assessing resistance.”15 The situation has changed little since that statement was made in 2002.


Although it is often speculated that organisms isolated from nosocomial infection outbreaks in veterinary patients now have an increasingly broad spectrum of antimicrobial resistance, there are no active nosocomial infection surveillance systems in this field. Much of the antibiotic resistance data are derived from “local” surveillance, and a lack of standardization results in data that are incomparable from one setting to another.16 In terms of the impact of multidrug-resistant (MDR) bacteria with regard to nosocomial infection, the data that have been published agree that resistant bacteria can reduce the effectiveness of management.15


Data on trends in resistance patterns among nosocomial pathogens from veterinary sources are few, but the wealth of surveillance data from human health care systems can often be used as a predictor of what to expect from nosocomial pathogens in veterinary patients.17-19 Local surveillance of antibiotic resistance in animal isolates is preferred, but in the absence of such data, extrapolation from human surveillance data is encouraged.


Bacterial resistance to β-lactam antibiotics and the β-lactamase inhibitors is becoming increasingly common and threatens to reduce the clinical spectrum of these drugs. In particular, organisms that produce extended-spectrum β-lactamases (ESBLs) and plasmid-mediated AmpC enzymes are posing unique challenges in clinical situations. Although the prevalence of ESBLs is not known, it is thought to be increasing, and in many parts of the world 10% to 40% of strains of E. coli and K. pneumoniae produce such enzymes. Novel β-lactamases are also becoming especially important among diverse gram-negative pathogens such as Pseudomonas aeruginosa, S. enterica serotype typhimurium, Proteus mirabilis, and A. baumannii.20 The source of these novel enzymes is unknown, but their presence on plasmids and ready transferability among pathogens of different genera are of concern. Organisms that produce ESBLs are found commonly in those areas of the hospital environment where antibiotic use is frequent and the patient’s condition is critical, and these resistant organisms cause increased morbidity and mortality.20

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Sep 10, 2016 | Posted by in SMALL ANIMAL | Comments Off on Nosocomial Infections and Zoonoses

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