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Infection is a major cause of mortality and morbidity in patients
admitted to hospital. The most frequent types of infection are
urinary tract, respiratory, wound, skin and soft-tissue infections,
and septicaemia, which is often associated with vascular access.
Food is usually prepared centrally in the hospital kitchens. Patients
are at risk of food-borne infection if hygiene standards fall; this
route can transmit antibiotic-resistant organisms to immunocompromised
patients who are especially vulnerable.
Pathogens (e.g. multidrug-resistant tuberculosis, respiratory
viruses or bacteria) may be transmitted via theatre air supply
and air-conditioning systems. Badly maintained air-conditioning
systems may be a source of Legionella.
Any inanimate object may be contaminated with organisms and
act as a vehicle (fomite) for transmission. This is important for
doctors performing procedures on patients with instruments that
might be contaminated and transmit infection (e.g. MRSA on
The water supply in a hospital is a complex system, supplying
water to wash-hand basins and showers, central heating and airconditioning
systems. Legionella spp. may colonize the system in
redundant areas of pipework and cooling-tower systems are a
particular risk. When systems fail, organisms such as Legionella
can be transmitted by the air-conditioning system. To reduce this
risk, hot-water supplies should be maintained at a temperature
above 45°C and cold-water supplies below 20°C.
Hospital patients are susceptible to infection as a result of underlying
illness or treatment, for example patients with leukaemia or
those receiving cytotoxic chemotherapy. Age and immobility may
predispose to infection; ischaemia may make tissues more susceptible
to bacterial invasion.
This is the most frequent source of healthcare-associated bacteraemia.
The risk of infection from any intravenous device increases
with the length of time it remains in position. Having broken the
skin's integrity, it provides a route for invasion by skin organisms
such as Staphylococcus aureus, Staphylococcus epidermidis and
Signs of inflammation at the puncture
site may be the first evidence of infection. Cannula-related infection
can be complicated by septicaemia, endocarditis and metastatic
infections (e.g. osteomyelitis). The risk of sepsis can be
reduced by aseptic technique at insertion, as well as the choice of
device, for instance those without side ports and dead spaces.
Maintaining an adequate dressing and ensuring good staff hygiene
when they are working with the device are equally important. The
cannula site should be regularly inspected and this is particularly
important in unconscious patients. Peripheral lines should be resited
every 48 h; central and tunnelled lines should be changed
when there is evidence of infection.
Indwelling urinary catheters bypass the normal defences and
provide a route for ascending infection into the bladder. Risks can
be minimized by aseptic technique when the catheter is inserted
Intubation bypasses the defences of the respiratory tract. Postoperative
pain, immobility and the effects of anaesthesia predispose
to pneumonia by reducing coughing. Respiratory infections with
resistant Gram-negative organisms that originate from the hospital
environment may occur. Inhalation of oral contents is reduced
by raising the head of the bed in seriously ill patients.
Surgical patients often have other health problems that are unrelated
to their surgical complaint (e.g. asthma or diabetes mellitus),
which may predispose them to infection. Surgery is traumatic and
carries a risk of infection (e.g. especially wound infections).
Complications of the procedure may increase risks (e.g. postoperative
ischaemia). Operation length and complexity influence the
risk of infection, as does the skill of the surgeon: the less tissue
damage occurs at an operation, the lower the risk of infection. The
preoperative period should be short to reduce the risk of acquiring
resistant hospital organisms and elective surgery should be postponed
in patients with active infection (e.g. chest infections).
To minimize the risk of infection during an operation, theatres
are supplied with a filtered air supply. Staff movement during
procedures should be limited to reduce air disturbance. Changing
clothing reduces transmission of organisms from the wards.
Impervious materials reduce contamination from the skin of the
surgical team but are uncomfortable to wear. Some hospitals
provide ventilated air-conditioned suits for surgical teams performing
prosthetic joint surgery.
Antibiotic prophylaxis reduces postoperative infection rates. Antibiotics
should be bactericidal, have sufficient penetration for the
required site and be chosen on the basis of the operation type - see
below. There is no evidence that continuing prophylaxis beyond
48 h is beneficial.
' involving the skin or a normally sterile site (e.g. a joint).
Antibiotics are unnecessary unless a prosthetic device is inserted.
' where a viscus with a normal flora is breached.
Antibiotics such as metronidazole and a second-generation cephalosporin
for large-bowel surgery; a cephalosporin alone is satisfactory
in surgery of the upper gastrointestinal or biliary tracts where
anaerobes are rarely implicated.
' operations are those in which surgery is required to deal
with an already infected situation, such as drainage of an abscess
or repair of a perforated diverticulum. Parenteral antibiotics to
treat the likely infecting organisms should be prescribed.