1. Infections
An understanding of commonly encountered micro-organisms is essential for good infection control practice. Micro-organisms that cause disease are referred to as pathogenic organisms. They may be classified as follows:
a. Bacteria are minute organisms about one-thousandth to five-thousandth of a millimetre in diameter. They are susceptible to a greater or lesser extent to antibiotics.
b. Viruses are much smaller than bacteria and although they may survive outside the body for a time they can only grow inside cells of the body. Viruses are not susceptible to antibiotics, but there are a few anti-viral drugs available which are active against a limited number of viruses.
c. Pathogenic Fungi can be either moulds or yeasts. For example, a mould which causes infections in humans is Trichophtyon rubrum which is one cause of ringworm and it may also infect nails. A common yeast infection is thrush caused by Candida albicans.
d. Protozoa are microscopic organisms, but larger than bacteria. Free-living and non-pathogenic protozoa include amoebae and paramecium. Examples of medical importance include: Giardia lamblia which can cause an enteritis (symptoms of diarrhoea).
e. Parasites Worms are not always microscopic in size but pathogenic worms do cause infection and some can spread from person to person. Examples include: threadworm and tapeworm, ectoparasites i.e. headlice and scabies.
f. Prions are infectious protein particles. Example: the prion causing (New) Variant Creutzfeldt-Jakob Disease (vCJD).
2. The Spread of Infection
a. Distinguishing Features
One feature that distinguishes infection from all other disease is that it can be spread, i.e. one person can ‘catch’ it from another or via a vector (e.g. crawling or flying insects). There are various means by which micro-organisms can be transferred from a reservoir to susceptible individuals.
b. Modes of Spread
The modes of spread of infection can be classified as:
i. Direct Contact
Direct spread of infection occurs when one person infects the next by direct person-to person contact (e.g. Chickenpox, Tuberculosis, sexually transmitted infections etc.).
ii. Indirect Contact
Indirect spread of infection is said to occur when an intermediate carrier is involved in the spread of pathogens e.g. fomite or vector.
c. Fomites
A fomite is defined as an object, which becomes contaminated with infected organisms and which subsequently transmits those organisms to another person. Examples of potential fomites are bedpans, urinals, thermometers, oxygen masks or practically any inanimate article.
d. Vectors
Crawling and flying insects are obvious examples of vectors and need to be controlled. Insect bites may cause infections such as malaria in areas where malaria carrying mosquitoes live.
e. Hands
The hands of health and social care workers are probably the most important vehicles of cross-infection. The hands of residents can also carry microbes to other body sites, equipment and staff.
f. Inhalation
Inhalation spread occurs when pathogens exhaled or discharged into the atmosphere by an infected person are inhaled by and infect another person. The common cold and influenza are often cited as examples, but it is likely that hands and fomites (inanimate objects) are also important in the spread of respiratory viruses.
g. Ingestion
Infection can occur when organisms capable of infecting the gastro-intestinal tract are ingested. When these organisms are excreted faecally by an infected person, faecal/oral spread is said to occur. Organisms may be carried on fomites, hands or in food and drink e.g. Hepatitis A, Salmonella, Campylobacter.
h. Inoculation
Inoculation infection can occur following a “sharps” injury when blood contaminated with, for example, Hepatitis B virus, is directly inoculated into the blood stream of the victim, thereby causing an infection. Human, animal and insect bites can also spread infection by the inoculation mode.
3. Principles for Hand Hygiene
The following section provides recommendations concerning hand
hygiene practice. The difficulty of designing and conducting ethical, randomised controlled trials in the field of hand hygiene, together with the lack of studies conducted in community and primary care means that recommendations in some areas of hand hygiene are predominantly based on expert opinion. Although the risk of healthcare associated infection (HAI) has been thought to be low in community and primary care settings, there is an absence of surveillance data to support this assumption.
In reducing the length of hospital stay, care previously delivered only in hospitals has progressively shifted to outpatient and home settings. In addition, healthcare practitioners are increasingly working across the boundaries of acute and community care and invasive procedures are performed in outpatient clinics, nursing home and home settings. These factors create the potential for patients to be at greater risk of acquiring a healthcare-associated infection outside the hospital setting.
The areas discussed include:
· assessment of the need to decontaminate hands;
· technique for hand decontamination;
· care to protect hands from the adverse effects of hand decontamination practice.
4. Why is hand decontamination crucial to the prevention of healthcare associated infection in the community?
Overviews of epidemiological evidence conclude that hand-mediated transmission is a major contributing factor in the current infection threats to hospital in-patients. These include both methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MRSA), and multi-resistant Gram-negative aerobes and enterococci. The transmission of microorganisms from one patient to another via the hands, or from hands that have become contaminated from the environment, can result in adverse outcomes. Primary exogenous infection is a direct clinical threat where microorganisms are introduced into susceptible sites, such as surgical wounds, intravascular cannulation sites, enteral feeding systems or catheter drainage systems. Secondary endogenous infection creates an indirect clinical threat where potential pathogens transmitted by the hands establish themselves as temporary or permanent colonisers of the patient and subsequently causes infection at susceptible sites.
5. Recommendations
Before regular hand decontamination begins, all wrist and ideally
hand jewellery should be removed. Cuts and abrasions must be
covered with waterproof dressings. Fingernails should be kept
short, clean and free from nail polish.
a. Technique
An effective handwashing technique involves three stages:
preparation, washing and rinsing, and drying.
i. Preparation requires wetting hands under tepid running water before applying liquid soap or an antimicrobial preparation.
ii. The handwash solution must come into contact with all of the surfaces of the hand. The hands must be rubbed together vigorously for a minimum of 10-15 seconds, paying particular attention to the tips of the fingers, the thumbs and the areas between the fingers.
iii. Hands should be rinsed thoroughly before drying with good quality paper towels.
b. Alcohol Rubs
When decontaminating hands using an alcohol handrub, hands should be free of dirt and organic material. The handrub solution must come into contact with all surfaces of the hand. The hands must be rubbed together vigorously, paying particular attention to the tips of the fingers, the thumbs and the areas between the fingers, until the solution has evaporated and the hands are dry.
c. Does hand decontamination damage skin?
Expert opinion suggests that skin damage is generally associated with the detergent base of the preparation and/or poor handwashing technique. The frequent use of hand preparation agents may cause damage to the skin and normal hand flora is altered which may result in increase carriage of pathogens responsible for healthcare associated infection. In addition, the irritant and drying effects of hand preparations have been identified as one of the reasons why healthcare practitioners fail to adhere to hand hygiene guidelines.
d. Handcare
An emollient hand cream should be applied regularly to protect skin from the drying effects of regular hand decontamination. If a particular soap, antimicrobial hand wash or alcohol product causes skin irritation an occupational health team should be consulted.
