Nosocomial infections• Infections appearing in conection with in both: in and out patients‘ stay in hospital.

• They are also known as a hospital-acquired infection.

• They may occur either during or after hospitalization (48 hours or more after hospital admission or within 30 days after discharge).

• Rresult of treatment in a hospital or hospital-like setting, but secondary to the patient´s original condition.

• One third of n.i. are considered preventable.

A ratio of 5 to 19% hospitalized patients are infected, and up to 30% in intensive care units.

The patients must stay in the hospital 4-5 additional days.

In the USA (1995) - one hospital patient in ten acquires n.i.; - 2 million patients a year; - 88 000 deaths a year.

• In France, the prevalence of n. i. differs from 6.87%, to 7.5%[3] (some patients are infected twice) :

- urinary tract infections: 40%; - infection of the skin and mucous membrane: 10.8%; - infections of surgery site: 10.3%; - pneumopathy: 10%.

Prevalence of nosocomial infections in CR: 1 – 2% reported cases, 4 – 7% by target monitoring,but: in intensive care units: 18%, in urology dep.: 10 – 40%.

From epidemiolotical point of view NI can be devided into two groups: - nonspecific

- specific for health institution. 

Nonspecific n.i. – infections common among the normal population (respiratory diseases, children exanthematic diseases, alimentary infections, etc.)

- they follow a current regional epidemiological situation - they do not need specific preventive arrangements.

Specific nosocomial infections resulting from diagnostical or therapeutical procedures (eg.

inoculation or implantation the agens into host organism).

* due to lack of personal hygiene of staff,* wrong therapeutic technique,* unsuitable working and building arrangement

Outside the hospital environment the conditions of spreading of those are missing.

 

Nosocomial infections may come from - exogenic (like cross-infection or environmental

infection) or- endogenic sources.  Cross-infection – coming from another person in the

hospital. Environmental infection – from inanimate object recently

contaminated by a human source.

Endogenous n.i.:• decreased defence mechanisms as an occasional result of

contemporary treatment or illness.

• penetration of normally non–pathogenic organisms into the susceptible tissues: blood, peritoneal cavity, cerebrospinal fluid, joints‘ cavities, etc.

  Many medical procedures bypass the body´s natural protective barriers.

Pathological agents – important nosocomial pathogens:

Bacteria (most common nosocomial pathogens):Commensal bacteria found in the normal flora of healthy people.

These have a significant protective role by preventing colonization by pathogenic microorganisms. Some commensal bacteria may cause infection if the natural host is compromised. Staphylococcus epidermidis (cause of i.v. infections), Escherichia coli (cause of urinary infections).

Pathogenic bacteria – they have greater virulence, and cause infections (sporadic or epidemic) regardless of host status.

Gram – positive: Staphylococus aureus – cutaneous bacteria that colonize the skin, nose and throat of patients and hospital staff. They cause a wide variety of lung, bone, heart and bloodstream infections and are frequently resistant to antibiotics.

In hospitals commonly 40-50% of S. aureus isolates are MRSA.

Streptococci: Streptococcus beta-hemolyticus, Strept. Pyogenes.Anaerobic Gram-positive rods (e.g. Clostridium) cause

gangrene.Gram–negative bacteria:Enterobacteriaceae (e.g. E. coli, Proteus, Klebsiella,

Enterobacter, Serratia marcescens) may colonize sites when the host defences are compromised. They may also be highly antibiotic resistant.

Pseudomonas spp. Are often isolated in water and damp areas. They may colonize the digestive tract of hospitalized patients.

Legionella species may cause pneumonia (sporadic or endemic) through inhalation of aerosols containing contaminated water (air conditioning, showers, therapeutic aerosols).

Viruses:There is the possibility of nosocomial transmission of

hapatitis B and C viruses (transfusions, dialysis, injections, endoscopy), respiratory syncytial virus (RSV), rotavirus, and enteroviruses (transmitted by hand-to-mouth contact and via the fecal-oral route). Other viruses such as cytomegalovirus , HIV, Ebola, influenza viruses, herpes simplex virus, and varicella-zoster virus, may also be transmitted.

Parasites and Fungi:Many of tham are opportunistic organisms and cause

infections during extended antibiotic treatment and severe immunosuppression (Candida albigans, Aspergillus spp., Cryptococcus neoformans, Cryptosporidium, Pneumocystis carini, Toxoplasma pneumoniae).

Sarcoptes scabies (scabies) is an ectoparasite – outbreaks in health care facilities.

Transmission of infection within a hospital requires three

elements: a source of infecting microorganisms, a susceptible host, and a means of transmission for the microorganism

SourceHuman sources: patients, medical staff, visitors

Human sources may include - persons with acute disease, - persons in the incubation period of a disease, - persons who are colonized by infectious agent but have no

apparent disease, or - persons who are chronic carriers of an infectious agent.

Transmission5 main routes – contact, droplet, airborne, common vehicle,

and vectorborne.Same microorganism may be transmitted by more than one

rout.Contact transmission: a) direct-contact transmission – involves a direct body

surface-to-body surface contact and physical transfer of microorganisms between a susceptible host and an infected or colonized person (during various patient-care activities that require direct personal contact).

b) indirect-contact transmission involves contact of susceptible host with a contaminated instruments, needles, or dressings, or contaminated hands of hospital staff.

Droplet transmission during coughing, sneezing, and talking, and during

performance of certain procedures (suctioning, bronchoscopy)

on the host´s conjunctivae, nasal mucosa, or mouth.

Airborne transmission occurs by dissemination of either airborne droplet nuclei

* small particles (equal or smaller 5 μm) of evaporated droplets containing microorganisms that remain suspended in the air for long periods of time)

or

* dust particles containing the infectious agents. Such particles are dispread widely.

• Microorganisms transmitted by airborne transmission include Mycobacterium tuberculosis and the rubeola and varicella viruses.

Prevention of airborne transmission - special air handling

and ventilation.

Common vehicle transmission – by contaminated items such as food, water, medications, devices, equipment.

Vectorborne transmission occurs when vectors such as mosquitoes, flies or rats transmit microorganisms.

Predisposition to infection

Factors predisposing a patient to the infection can be divided into four areas:

1) Poor state of health due to - advanced age or premature birth, - immunocompromisation due to contemporary treatment eg. by corticosteroids, antibiotics, immunosupressive drugs, - bad nutritional status, - psychosomatic stress, - convalescence period.

2) Acute disease can increase the risk of infection – burns and trauma cause the loss of skin.

3) Invasive devices – intubation tubes, catheters, surgical drains and tracheostomy tubes.

4) A patient´s treatment

Preventive measures:

• proper means of disinfection and sterilisation (physical, chemical and biological tests),

• disposable instruments (cost/effectiveness!),

• separation or/and exclusion of suspect sources (patients, visitors),

• strict rules in handling the bedclothes, meals and hospital wastes,

• hospital committee for nosocomial infections – evidence, surveillance,

• omitting of washing the hands between the contact with two different patients.

Routine use of anti-microbial agents in hospitals creates selection pressure for the emergence of resistant strains.

Thorough hand washing and/or use of alcohol rubs by all medical personnel before each patient contact is one of the most effective ways to combat nosocomial infections.

More careful use of anti/microbial agents, such as antibiotics, is also considered vital.

Nosocomial infections are even more alarming in the 21st century as antibiotic resistance spreads.

Reasons why nosocomial infections are so common include:

• hospitals house large numbers of people who are sick and whose immune systems are often in a weakened state;

• increased use of outpatient treatment means that people who are in the hospital are sicker on average;

• medical staff move from patient to patient, providing a way for pathogens to spread;

• many medical procedures bypass the body's natural protective barriers.

Types of MRSA infections:CA-MRSA: community-acquired MRSA- commonly causes skin and soft tissue infections, frequently in

young and otherwise health individuals. The most affected population groups are those in a close person-to-

person contact environment and poor hygienic conditions: homeless people, prisoners, military personnel, athletes, and day care nurseries.

Young age, diabetics, immunocompromised individuals, eczema and similar skin disorders are additional risk factors.

HA-MRSA: hospital-aquired MRSA- usually causes bacteraemia and systemic infection in older and ill patients.The percentage of healthy individuals colonised by S. aureus is about

25-50 %, with higher numbers in risk groups such as diabetics, HIV-infected, patients on dialysis, patients with skin problems, immunocompromised patients (neutropenic), and the critically ill.

Prevention of MRSA:

• Primary – decontamination of surfaces, materials, clothes, equipment (keyboards, mobile phones), and hands.

• Secondary – screening

Helps to determine the prevalence and incidence, as well as guiding directed intervention.

• Tertiary preventive strategies include isolation and barrier observation. Beneficial effects of mouth protection, gowns and hair covers when entering a MRSA affected patient room.

Incorporated into hand hygiene guidelines is the avoidance of long-sleeved coats, and jewellery.

Hand hygiene compliance is worst during periods of high workload. These periods are associated with increased transmission of MRSA. In studies conducted on

compliance, results were disappointing, with averages below 50%.

Once colonized staff members have been detected, one method of decolonization is use of mupirocin.

Recommendation (Swedish strategy)

Aim is to prevent direct (from staff to patient) and indirect (from patient via

staff to other patient) transmission.

Rings, arm bracelets, and wrist watches are not allowed.

Nails should be kept short and nail extensions avoided.

Hands must be disinfected before patient contact, before gloving, after

patient contact, and after removing gloves.

Before admission of a new patient to an inpatient ward, samples for MRSA

screen are taken from any skin wounds or breaks (e.g. eczema), catheters,

ports, anterior nares, throat, and perineum.

On an outpatient basis, patients are screened for MRSA if an infection is

suspected to be staphylococcal in origin and in a patient with risk factors

(wounds, ports, catheters, contact with health care either as a patient or

professionally in the past 6 months, etc.).

Once a patient is MRSA culture positive, all staff must be screened. Staff with

wounds, skin lesions, or eczema, are suspended awaiting results.