Infections acquired during a hospital stay are called nosocomial infections. Usually an infection is considered to be nosocomial if it arises >72 hours after admission, as earlier infections are usually presumed to have been acquired in the community. For patients who are only briefly admitted the infection may only become manifest after discharge.
Approximately 10% of patients admitted to a hospital in the United Kingdom acquire a nosocomial infection. Infections may be spread by droplet inhalation or direct hand contact from hospital staff or equipment. The patients most at risk are those at extremes of age, those with significant co-morbidity, the immunosuppressed and those with recent surgery. Risk factors also depend on the site, for example pneumonia is more common in patients who are ventilated, who are bedbound or who have had thoracic or abdominal surgery. Instrumentation such as urinary catherisation or central lines can introduce infections.
The commonest sites of nosocomial infections are
· urinary tract infections,
· respiratory tract infections,
· surgical site infections, bacteraemia,
· skin infections, e.g. of burns and
· gastrointestinal infections.
Nosocomial infections are most commonly bacterial, particularly Staph. aureus, Pseudomonas and Escherichia coli. Clostridium difficile is a common cause of diarrhoea in patients given broad-spectrum antibiotics. Viruses are also important, e.g. small round structured viruses (SRSV), which have caused outbreaks of diarrhoea in some hospitals, influenza and other respiratory infections can affect patients and staff alike (as dramatically highlighted by the outbreak of SARS in 2003). Fungi, particularlyCandida and Aspergillus, are also becoming more important.
Many of the pathogens that cause nosocomial infections have a high level of antibiotic resistance, which is a major cause of concern. Some examples include the following:
· Methicillin resistant Staph. aureus (MRSA) is resistant to flucloxacillin and most other commonly used anti Staphylococcal agents. It is treated by vancomycin orteicoplanin. Nasal colonisation and skin clearance is achieved by topical cream and antiseptic washes.
· Vancomycin resistant Enterococcus (VRE) is increasingly common.
· Vancomycin-intermediate/resistant Staph. aureus (VISA/VRSA) emerged with cases of VISA in the late 1990s and VRSA in 2002. It is still rare, but of concern. It is also called GISA (glycopeptide-intermediate SA) because vancomycin is a glycopeptide.
The principles are to avoid transmission by always washing hands after examining a patient, strict aseptic care of central lines and isolation of cases in a sideroom or even by ward. Certain patients are given prophylactic antibiotics, e.g. preoperatively, where possible indwelling urinary catheters or central lines should be avoided or the duration of use minimised. Early mobilisation and discharge also help to reduce the period of risk. Once patients are identified as having diarrhoea or being infected with resistant organisms they should be barrier nursed in a separate room. Staff and visitors should wear gloves, aprons and where appropriate masks whilst in the room, and disinfect their hands following the visit with alcohol gel. Patients at high risk because of neutropenia are also isolated and reverse barrier nursed to try to protect them from exposure to infections.
In addition, overuse of antibiotics particularly broad-spectrum antibiotics should be avoided. Where the development of resistance is likely, combination antibiotics are used.