NOSOCOMIAL INFECTIONNOSOCOMIAL INFECTION

Nosocomial diseaseNosocomial disease

a hospital acquired diseasea hospital acquired diseaseUp to 15% of hospitalized patients Up to 15% of hospitalized patients

get a nosocomial infection. (WHO get a nosocomial infection. (WHO 2002 ; 8,7%)2002 ; 8,7%)

Most nosocomial infections are Most nosocomial infections are caused by caused by opportunistic pathogens opportunistic pathogens that are typically considered to be that are typically considered to be Normal Flora.Normal Flora.

Centers for Disease ControlCenters for Disease Control Atlanta, defined :Atlanta, defined :

Nosocomial Infection as a localized Nosocomial Infection as a localized infection or one that is widely spread infection or one that is widely spread throughout the body that results throughout the body that results from an adverse reaction to an from an adverse reaction to an infectious microorganism or toxin infectious microorganism or toxin that was not present at the time of that was not present at the time of admission to the hospital admission to the hospital

whowho

An infection acquired in hospital by a patient who was admitted for a reason other than that infection

An infection occurring in a patient in a hospital or other health care facility in whom the infection was not present or incubating at the time of admission

Nosocomial infectionsNosocomial infections

Infections are considered nosocomial Infections are considered nosocomial if they first appear 48 hours or more if they first appear 48 hours or more after hospital admission. after hospital admission.

The most common nosocomial The most common nosocomial infections are of the infections are of the urinary tract, , and various and various pneumonias..

• Usually related to a procedure or treatment used to treat the patient

Transmission of infection within Transmission of infection within a hospital requires three a hospital requires three

elementselementsa source of infecting a source of infecting microorganisms a susceptible a susceptible hosta means of transmission for the a means of transmission for the

microorganism.microorganism.

Factors contributing to Factors contributing to nosocomial infectionsnosocomial infections

hosthost

People are as a reservoir or source of People are as a reservoir or source of microorganisms, as the transmitter of , as the transmitter of microorganisms and as a receptor for microorganisms and as a receptor for microorganisms microorganisms

Infections coming from another person in Infections coming from another person in the hospital (cross-infection), from an the hospital (cross-infection), from an inanimate object recently contaminated by inanimate object recently contaminated by a human source (environmental infection) a human source (environmental infection) or may be caused by a patient’s own flora or may be caused by a patient’s own flora (endogenous infection). (endogenous infection).

sourcessources

Human sources may be patients, Human sources may be patients, personnel, visitors, persons with acute personnel, visitors, persons with acute disease, persons in the incubation period disease, persons in the incubation period of a disease, persons who are colonized by of a disease, persons who are colonized by an infectious agent but have no apparent an infectious agent but have no apparent disease, or persons who are disease, or persons who are chronic carriers of an infectious agent. carriers of an infectious agent.

Environmental objects that have become Environmental objects that have become contaminated, including equipment and contaminated, including equipment and medicationsmedications. .

Types of nosocomial Types of nosocomial infectionsinfections

Why nosocomial infections are Why nosocomial infections are so common: so common:

Hospitals house large numbers of people Hospitals house large numbers of people who are sick and whose who are sick and whose immune systems are often in a weakened state. are often in a weakened state.

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

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

routine use of anti-microbial agents in routine use of anti-microbial agents in hospitals creates the emergence of hospitals creates the emergence of resistant strains resistant strains

etiologyetiology

The most common microbiological The most common microbiological cause of nosocomial infection is cause of nosocomial infection is bacteria. bacteria.

Gram-negative bacteria, Gram-negative bacteria, E.coliE.coli, , Proteus mirabilisProteus mirabilis and other members and other members of the family Enterobacteriacaea are of the family Enterobacteriacaea are predominant. These bacteria are predominant. These bacteria are residents of the intestinal tract, spread residents of the intestinal tract, spread via fecal via fecal contaminationcontamination of people, of people, instruments or other surfaces. Other instruments or other surfaces. Other Gram-negative : Gram-negative : PseudomonasPseudomonas and and AcinetobacterAcinetobacter

etiologyetiology

Gram-positive bacteria, especially Gram-positive bacteria, especially Staphylococcus Staphylococcus coagulase negative, coagulase negative, frequently cause infections of frequently cause infections of wounds. This bacterium is part of the wounds. This bacterium is part of the normal flora on the surface of the normal flora on the surface of the skin, and so can readily gain access skin, and so can readily gain access to a wound or surgical incision to a wound or surgical incision

BacteriaBacteria

Commensal bacteria found in the found in the normal flora of healthy humans, have a of healthy humans, have a significant protective role by preventing significant protective role by preventing colonization by by pathogenic microorganisms. .

Some commensal bacteria may cause Some commensal bacteria may cause infection if the natural host is compromised. infection if the natural host is compromised. For ex, For ex, Staphylococcus epidermidis causes causes IV line infection, line infection, Escherichia coli (E. coli) are (E. coli) are the most common cause of urinary infection. the most common cause of urinary infection.

Pathogenic bacteria have greater have greater virulence, and cause infections regardless of host , and cause infections regardless of host status. For example:status. For example:

Anaerobic Gram-positive rods (e.g. rods (e.g. Clostridium) cause ) cause gangrene. .

Gram-positive bacteria: Gram-positive bacteria: Staphylococcus aureus (bacteria that (bacteria that colonize the skin and nose of patients colonize the skin and nose of patients and hospital staff) cause a wide variety and hospital staff) cause a wide variety of lung, bone, heart and bloodstream of lung, bone, heart and bloodstream infections and are frequently resistant to infections and are frequently resistant to antibioticsantibiotics

Gram-negative bacteria: bacteria: Enterobacteriaceae (e.g. (e.g. E. coli, , Proteus, , Klebsiella, , Enterobacter, , Serratia marcescens) may also be highly ) may also be highly antibiotic resistant. antibiotic resistant.

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

other bacteria are a unique risk in hospitals. other bacteria are a unique risk in hospitals. Legionella species may cause species may cause pneumonia through inhalation of through inhalation of aerosols containing containing contaminated water (air conditioning, showers, contaminated water (air conditioning, showers, therapeutic aerosols).therapeutic aerosols).

Viruses Viruses

Including the Including the hepatitis B and C viruses ( B and C viruses (transfusions, , dialysis, , injections, , endoscopy))

respiratory syncytial virus (RSV), (RSV), rotavirus, , and and enteroviruses (transmitted by hand-to- (transmitted by hand-to-mouth contact and via the fecal-oral route) mouth contact and via the fecal-oral route)

Other viruses such as Other viruses such as cytomegalovirus (CMV), (CMV), HIV, , Ebola, , influenza viruses, viruses, herpes simplex virus, and , and varicella-zoster virus, may also be , may also be transmitted.transmitted.

Parasites and Fungi Parasites and Fungi Giardia lamblia are transmitted easily are transmitted easily fungi and and parasites are are opportunistic organisms and organisms and

cause infections during extended antibiotic cause infections during extended antibiotic treatment and severe treatment and severe immunosuppression ( (Candida albicans, , Aspergillus spp., spp., Cryptococcus neoformans, , Cryptosporidium), cause ), cause of systemic infections among of systemic infections among immunocompromised patients. patients.

Environmental contamination by airborne organisms Environmental contamination by airborne organisms such as such as Aspergillus spp. which originate in dust and spp. which originate in dust and soil, especially during hospital construction. soil, especially during hospital construction.

SarcoptesSarcoptes scabies (scabies) is an (scabies) is an ectoparasite which has repeatedly caused outbreaks in health which has repeatedly caused outbreaks in health care facilities.care facilities.

Predisposition to infectionPredisposition to infection

People in hospitals are usually in a People in hospitals are usually in a poor state of healthpoor state of health, impairing , impairing their defence against bacteriatheir defence against bacteria

Acute diseaseAcute disease can greatly increase can greatly increase the risk of infection – the risk of infection – burns and and trauma cause the loss of skin, an cause the loss of skin, an important barrier against infection. important barrier against infection.

Predisposition to infectionPredisposition to infectionInvasive devicesInvasive devices, for instance , for instance intubation

tubes, tubes, catheters, surgical drains and , surgical drains and tracheostomy tubes bypass the body’s tubes bypass the body’s natural lines of defence against natural lines of defence against pathogens. .

immunosuppression and and antacid treatment treatment undermine the body’s defences, while undermine the body’s defences, while antimicrobial therapy (removing therapy (removing competitive competitive flora and only leaving resistant and only leaving resistant organisms)organisms)

recurrent recurrent blood transfusions, , parenteral nutrition have all been identified have all been identified as risk factors. as risk factors.

TransmissionTransmission

Direct-contact between a susceptible Direct-contact between a susceptible host and an infected person, such as host and an infected person, such as occurs when a person turns a patient, occurs when a person turns a patient, gives a patient a bath, or performs gives a patient a bath, or performs other other patient-carepatient-care activities that activities that require direct personal contact. require direct personal contact.

also can occur between two patients, also can occur between two patients, with one serving as the source of the with one serving as the source of the infectious microorganisms and the infectious microorganisms and the other as a susceptible host. other as a susceptible host.

TransmissionTransmission

Indirect-contact, involves contact Indirect-contact, involves contact of a susceptible host with a of a susceptible host with a contaminated intermediate contaminated intermediate object, usually inanimate, such object, usually inanimate, such as contaminated instruments, as contaminated instruments, needles, or contaminated hands needles, or contaminated hands that are not washed and gloves that are not washed and gloves that are not changed between that are not changed between patientspatients

Major routes of transmission and prevention of spread of nosocomial pathogens.

Droplet transmission Droplet transmission

is a form of contact transmission. Droplets is a form of contact transmission. Droplets are generated from the source person are generated from the source person primarily during coughing, sneezing, and primarily during coughing, sneezing, and talking, and procedures such as talking, and procedures such as suctioningsuctioning and bronchoscopy. and bronchoscopy.

Transmission occurs when droplets Transmission occurs when droplets containing microorganisms generated containing microorganisms generated from the infected person are propelled a from the infected person are propelled a short distance through the air and short distance through the air and deposited on the host's conjunctivae, deposited on the host's conjunctivae, nasal mucosa, or mouth.nasal mucosa, or mouth.

Airborne Transmission Airborne Transmission occurs by dissemination airborne droplet occurs by dissemination airborne droplet

nuclei (small-particle residue 5 µm or smaller) nuclei (small-particle residue 5 µm or smaller) of evaporated droplets containing of evaporated droplets containing microorganisms that remain suspended in the microorganisms that remain suspended in the air for long periods of time, or by dust air for long periods of time, or by dust particles containing the infectious agent. particles containing the infectious agent.

Microorganisms carried in this manner can be Microorganisms carried in this manner can be dispersed widely by air currents and may dispersed widely by air currents and may become inhaled by a susceptible host within become inhaled by a susceptible host within the same room or over a longer distance from the same room or over a longer distance from the source patient the source patient

Microorganisms transmitted by airborne Microorganisms transmitted by airborne transmission include M. tuberculosis, rubeola transmission include M. tuberculosis, rubeola and varicella viruses. and varicella viruses.

Other TransmissionOther Transmission

Common Vehicle Transmission Common Vehicle Transmission applies to microorganisms applies to microorganisms transmitted by contaminated items transmitted by contaminated items such as food, water, medications, such as food, water, medications, devices, and equipment. devices, and equipment.

Vectorborne Transmission occurs Vectorborne Transmission occurs when vectors such as mosquitoes, when vectors such as mosquitoes, flies, rats, and other vermin transmit flies, rats, and other vermin transmit microorganismsmicroorganisms

Which Nosocomial Infections Are Which Nosocomial Infections Are Emerging?Emerging?

Acquired antimicrobial resistance Acquired antimicrobial resistance VRE and MRSA are the major gram-positive VRE and MRSA are the major gram-positive

pathogens of concernpathogens of concern P. aeruginosa, Klebsiella, and Enterobacter have P. aeruginosa, Klebsiella, and Enterobacter have

chromosomal or plasmid-mediated beta-chromosomal or plasmid-mediated beta-lactamase enzymes are the major resistant gram-lactamase enzymes are the major resistant gram-negative pathogensnegative pathogens

The contribution of antibiotic resistance to The contribution of antibiotic resistance to excessive death rates in hospitals is difficult to excessive death rates in hospitals is difficult to evaluate, antimicrobial resistance contributes to evaluate, antimicrobial resistance contributes to nosocomial deaths.nosocomial deaths.

viral and fungal resistance could become viral and fungal resistance could become important because of the small number of important because of the small number of therapeutic optionstherapeutic options