Nosocomial infections

Diseases from within hospital doors

Infections acquired by a patient while he is admitted in a hospital or while using the services in a healthcare institution e.g diagnostic services such as laboratory investigations, preventive services, vaccination, et cetera are referred as 'nosocomial infections' (a term derived from 'nosos' the Greek word for 'disease') or 'Iatrogenic infections'. Initially, the term nosocomial infections was used to describe the infection acquired in the hospitals only, but later it was realised that patients who have utilised the services of a healthcare institution were also found to develop certain nosocomial infections. Nosocomial infections causes major problems in healthcare facilities, resulting in prolonged hospital stay and substantial morbidity and mortality.

History

Modern understanding of nosocomial infection pre-dates the infancy of microbiology as a discipline and the entire concept of infection control is grounded in the work of Ignaz Semmelweis, who in the 1840's demonstrated the importance of hand hygiene for controlling transmission of infection in hospitals. In the Vienna General Hospital his investigations led him to conclude that medical students were carrying "cadaveric material" from the dissection classrooms on their hands and that it was this material that led to the deadly puerperal infections of women following delivery. After considerable struggle with the Viennese medical establishment, he insisted on a strict protocol of hand washing in chlorine water after dissection and before moving to the delivery ward. The effect was a dramatic reduction in the mortality rate.

Despite such dramatic results, infection control efforts remained neglected for almost a century. In 1976, the Joint Commission on Accreditation of Healthcare Organisations (JCAHO) published accreditation standards for infection control, creating the impetus and need for hospitals to provide essential support for infection control programs. In 1985, the Centres for Disease Control and Prevention (CDC) published a study report on the Efficacy of Nosocomial Infection Control, in which role of four key infection control components (hospital epidemiologist, clinical microbiologist for every 250 beds, active surveillance mechanisms, and ongoing control efforts) was emphasised, and following implementation of these measures nosocomial infection rates were reduced by one third.

The Problem

About one patient in ten of those who come in contact with hospital and health care settings acquires nosocomial infection. In United States, the nosocomial infection rate is about 5 to 6 hospital-acquired infections for every 100 admissions. As of 1995, the health care cost of nosocomial infections was huge ($4.5 billion) and has contributed to more than 88,000 deaths (one death every 6 minutes) and these numbers have grown with each passing year. No statistical data is available about India; due to lack of health care data notification and linkage system.

It is believed that the majority, perhaps as much as 80% of nosocomial infections are caused by the microbial flora that patients bring with them upon admission to the hospital. This "stay-at-home" flora appears to be opportunistic to the new environment and is able to take advantage of new routes of transmission that medical procedures offer.

Other nosocomial infections (perhaps 10% to 20%), develop following contamination with microbial organisms found within the hospital environment, often via the hands, instruments of Health Care Workers (HCWs) or contact with contaminated hospital materials. Examples of this include transfer of Staphylococcus aureus or Streptococcus pneumoniae from one patient to another via the hands of HCWs. Handwashing with antiseptics, use of disinfectants on inanimate objects and environmental surfaces have been shown to decrease the spread of potential pathogens to patients. Finally, person-to-person spread of infections in the health care setting can occur via direct contact, droplet, airborne, fecal-oral, and blood-borne routes.

Risk Factors

A number of risk factors have been linked with the development of nosocomial infections, especially the antibiotic-resistant micro-organisms. Perhaps the most important is prior treatment with broad-spectrum antibiotics, which has been shown to suppress symbiotic intestinal normal microbial flora. The presence of a persistent focus of infection (i.e. abscess, or large wound) is another important risk factor. An extended stay in hospital is also a risk factor for acquisition of antibiotic-resistant pathogenic infection. Individuals may also have multiple risk factors and are accordingly at very high risk for nosocomial infection. These risk factors overlap, but may be considered broadly as underlying host defects (i.e. immunosuppression, old age), and mechanical predispositions (being bedridden, invasive medical devices like intravascular catheters).

The most important contributing factor for increase in occurrence of nosocomial infection rates is that many HCWs fail to follow basic infection control procedures such as hand washing between patient contacts and in ICUs, emergency rooms and pre-& postoperative asepsis is often overlooked in the rush of crisis care. During daily activity, HCWs progressively accumulate micro-organisms on their hands from direct patient contact or contact with contaminated environmental surfaces and devices. The commensal resident flora colonises skin layers and resident flora generally has lower pathogenic potential than transient flora and is considered important for colonisation resistance, preventing colonisation with other, potentially more pathogenic, micro-organisms. Transient flora colonises the superficial skin layers for short periods and is usually acquired by contact with a patient or contaminated environmental surfaces and devices. These micro-organisms are easily removed by mechanical means such as hand washing.

Hand washing refers to the application of a plain (non-antimicrobial) or antiseptic (antimicrobial) soap, mechanical friction generated by rubbing the hands together for 1 minute (covering all surfaces of the hands and fingers), rinsing with water, and drying thoroughly with a disposable towel (which is then used to turn off the faucet). The cleaning activity is attributed to detergent properties, which result in mechanical removal of dirt (soil and organic substances) and loosely adherent flora (most transient flora and a small portion of the resident flora) from the hands.

The term "hand antisepsis" indicates hand hygiene with an antiseptic agent, either washing the hands with an antimicrobial soap or using an alcohol-based hand rub. In contrast to hand washing, the objective of this procedure is a more effective and rapid reduction of skin flora by killing, not mechanically removing micro-organisms (all transient flora and most resident flora). Therefore, the alcohol hand-rub procedure should not be confused with hand washing and vigorous friction, rinsing with water, and drying with a towel are unnecessary. Instead, the technique consists of rubbing alcohol onto both hands until it completely evaporates, usually requiring 15 to 30 seconds. Most dispensers deliver 1.5 to 2.0 mL of alcohol per application; therefore, 2 applications are usually necessary to completely cover both hands.

A second contributing factor is the overuse of antimicrobials. Increased concern about infections in the 1970's to 1980's led to the increased use of antibiotics. For example, widespread use of cephalosporin antibiotics is often cited as a cause for the emergence of Enterococci as nosocomial pathogens. At the same time, methicillin resistant Staphylococcus aureus (MRSA), also in response to extensive use of cephalosporin antibiotics, became a major nosocomial threat. This led to the overuse of vancomycin, partly in response to concerns about MRSA and for treatment of vascular catheter associated infections by organisms such as the resistant coagulase-negative Staphylococci. Now medical institutions are faced with a resident flora of "super-bugs", resistant to the most potent antimicrobials.

A third contributing factor is the hospital environmental dust and suspended particulate matter, which contain many pathogenic fungal spores, toxic molds leading to severe nosocomial fungal infections and illness due to other pathogens, such as Legionella pneumophilia.

Seeking Solutions

Every attempt must be made to control risk factors for nosocomial infections and include utilizing proper handwashing by HCWs, improving sterilisation and disinfection procedures, and minimising the use of indwelling vascular catheters and urinary tract drainage devices. Reducing of the number of micro-organisms present on the patient's body surface with disinfectant preparations has also been found to be helpful.

Standard Operating Procedures (SOPs)

In order to minimise and/or eliminate nosocomial infections it is important to formulate Standard Operating Procedures (SOPs) for the health care institution. It has been advocated that, reusable medical devices or patient care equipment that enters normally sterile tissue and the vascular system must be sterilised before each reuse. (Sterilisation in this context means the use of physical or chemical procedures to destroy all microbial life, including highly resistant bacterial endospores)

Sterilisation

The common sterilising procedures used in hospitals are steam autoclaving and use of ethylene oxide gas or dry heat. There are also a variety of chemical sterilants that have been used for purposes of reprocessing reusable heat-sensitive medical devices. These chemicals are rarely used for sterilisation, but appear to be effective for high-level disinfection of medical devices that come into contact with mucous membranes during use (e.g., flexible fiberoptic endoscopes). Laparoscopic or arthroscopic telescopes should be subjected to a sterilisation procedure before each reuse. Heat stable accessories to the endoscopic set (e.g., trocars, operative instruments) should be sterilised by heat-based methods (e.g., steam autoclave or dry heat oven).

Disinfection

When sterilisation is not indicated, disinfection should be achieved. Disinfection means the use of a chemical procedure to eliminate virtually all recognised pathogenic micro-organisms, but not necessarily all microbial forms (e.g., bacterial endospores or prions) on hands of HCWs and inanimate objects.

There are three levels of disinfection. High-level disinfection kills all organisms, except bacterial spores, which should be treated with a chemical germicide. Intermediate-level disinfection kills mycobacterium, most viruses and bacteria. Low-level disinfection kills some viruses and bacteria. Heat-stable reusable medical devices that enter the blood stream or enter normally sterile tissue should always be reprocessed using heat-based methods of sterilisation (e.g., autoclave or dry heat oven).

Any reusable devices or items that touch mucous membranes (e.g., reusable flexible endoscopes, endotracheal tubes, anaesthesia breathing circuits, respiratory therapy equipment) should receive high-level disinfection between patients. Items that do not ordinarily touch the patient or touch only intact skin (blood pressure cuffs, crutches, bedboards) are not usually involved in infection transmission, and generally do not necessitate disinfection between uses on different patients. Consequently, depending on the particular piece of equipment or item, washing with a detergent or low-level disinfectant may be sufficient when decontamination is needed, but if these items are grossly soiled with blood or other body fluids, then they should be cleaned and disinfected using a low level agent.

Prevention

Infection control is very cost-effective and approximately one third of nosocomial infections are preventable. Prevention begins by identifying those who have risk factors for nosocomial infections. Proper handwashing by HCWs, proper use of gloves, and careful attention to protecting devices (e.g., endotracheal tubes) from contamination are crucial in decreasing microbial contamination of the patient. Local skin care and use of topical antiseptics are very important with wounds or indwelling catheters of any type. Antiseptics have been effective in preventing infections via both preoperative skin preparation of invasive procedure sites and postoperative care of surgical sites. Preventative measures are best tailored to the patient's acute and chronic disorders and should be employed comprehensively and consistently.

Proper Handwashing

Proper handwashing by HCWs is perhaps the greatest prevention of all. On skin, alcohols (e.g., 50% to 70% isopropyl alcohol) are effective against common micro-organisms involved in nosocomial infections. The antimicrobial activity of alcohols is based on protein denaturation and they have excellent and rapid (within seconds) germicidal activity against vegetative bacteria, fungi, and many viruses. For hand rubs, ethanol, isopropanol, and/or n-propanol are used. In general, alcohol rubs are approximately 100 times more effective against viruses than any form of hand washing. Transmission of viruses is of concern in a broad range of health care institutions, including paediatric wards, bone marrow transplantation units, and long-term care facilities. The virucidal activity of alcohol against enveloped viruses (such as influenza virus or human immunodeficiency virus) is good.

Alcohol Hand Sanitisers

Alcohol hand-rub technique is better than hand washing due to various benefits. At least 1 to 2 minutes are required for hand washing compared with 15 to 30 seconds for the alcohol hand-rub technique. In the intensive care unit, where as many as 40 opportunities for hand hygiene per hour of care occur, time constraint becomes the most important limiting factor. Multiple studies have shown that understaffing and increased workload is risk factor for health care-associated epidemics. In a mathematical model with 3 opportunities for hand hygiene per HCW per hour, 100% adherence would result in 1.3 hours of hand washing per shift (or 17% of total nursing time). Switching to alcohol hand disinfection would decrease the time necessary for hand hygiene to 0.3 hours (or 4% of total nursing time). In addition, HCWs can use the alcohol rub while walking to the next patient, saving additional time and human resources.

Washed hands can become recontaminated from faucets or by splashes from traps or sinks and Pseudomonas aeruginosa is commonly found in tap water. In addition, plain soaps may become contaminated during use, and waterborne bacteria from the plumbing system may be present in the tap water. In contrast, alcohol hand rubs eliminate the risk of hand contamination or microbial dispersal into the environment because alcohol kills rather than removes micro-organisms. Contamination of alcohol-based solutions with vegetative bacterial forms has not been reported and alcohol dispensers can be reused as long as they are not visibly soiled.

Intact skin on HCWs' hands helps to protect both them and their patients from acquiring or transmitting nosocomial pathogens. Health care workers with dermatitis are more likely to harbour S aureus and other pathogenic bacteria than those with healthy skin. Skin drying and irritation can be avoided by adding emollients to alcohol formulations. Moreover, alcohol hand rubs cause substantially less skin irritation and dryness than washing with soap. Hand washing removes lipids from the skin, whereas alcohol compounds only redistribute them. Allergies to alcohol are extremely rare.

The increasing use of alcohol for hand hygiene raises concern about the risk for emergence of resistant micro-organisms. Despite extensive use, there is no evidence that such resistance has emerged in vitro or in vivo, suggesting that the mechanism of action (protein denaturation) or the rapid killing effect may not allow the development of resistance. In addition, the rapid evaporation of alcohol prevents extended exposure of micro-organisms to sub inhibitory concentrations of alcohol, possibly reducing the risk of emergence of resistance.

Scientific evidence and ease of use support the use of alcohol-based hand rubs for hand hygiene during patient care. The alcohol hand-rub technique is microbiologically more effective, more accessible, and less likely to cause skin problems and saves time and human resources. As a consequence, alcohol hand rubs are associated with substantially better adherence to hand hygiene than hand washing. The use of alcohol-based hand rubs should replace hand washing as the standard for hand hygiene in health care settings in all situations in which the hands are not visibly soiled.

Other Chemicals

The other chemical agents have certain limitations as compared to alcohols. Chlorhexidine is less effective against gram-negative bacteria, only fair against fungi, and minimally active against Mycobacterium tuberculosis. Hexachlorophene has a slow onset of action, minimal gram-negative activity and the potential for absorption with resultant neurotoxicity has limited its use. Para-chloro-meta-xylenol is less effective in reducing skin flora and is neutralised by nonionic surfactants. Triclosan is a poor fungicide and may be irritating. Currently iodophors, are used for handwashing, surgical scrubs, and skin preparations, however allergic adverse events and reduction of antimicrobial activity in the presence of organic materials (e.g., blood or sputum) limit its usage.

Conclusion

HCWs are responsible for preventing and controlling nosocomial infections. By identifying patients at risk, proper handwashing by HCWs, improving sterilisation and disinfection can control and eliminate many of the common nosocomial infections. All HCWs play an essential roll in this effort including those that touch the skin of an individual patient, as well as those who sterilise, disinfect and store the materials. Together, HCWs can make a safer environment, one free from the diseases found within hospital doors!