Reviews the definition, risk factors, types, sources, causes, and modes of transmission of healthcare-associated infections and the preventive measures that can be applied to minimize the risks.

2. • Nosocomial comes from the Greek words “nosus”
which means disease and “komeion” which
means to take care of.
• A nosocomial infection is an infection that occurs
or originates in a hospital or a health care setting,
and whose development and spread is favored by
hospital environment such as an infection
acquired during a hospital stay or visit.
• Also defined as an infection not present and
without evidence of incubation at the time of
admission to a healthcare setting.

3. • Nosocomial infections are also known as
hospital-acquired infections (HAI).
• As health care increasingly expands beyond
hospitals into outpatient settings, nursing homes,
long-term care facilities, and even home care, the
more appropriate term has become healthcare-
associated infections (also healthcare-acquired
infections), Replacing older ones such as
nosocomial, hospital-acquired or hospital-onset
infections.

4. • Most infections that become clinically evident
after 48 hours of hospitalization are considered
hospital-acquired.
• Infections that occur after the patient is
discharged from the hospital can be considered
healthcare-associated if the organisms were
acquired during the hospital stay.

5. • In the United States, the Centers for Disease
Control and Prevention (CDC) estimate that
roughly 2 million hospital-associated infections
occur each year.
• They affect 5% to 10% of hospitalized patients.
• They cause approximately 90.000 deaths.
• They add $45 billion to the total US healthcare
bill each year.

6. • A prevalence survey conducted under the
auspices of WHO in 55 hospitals of 14 countries
representing 4 WHO Regions (Europe, Eastern
Mediterranean, South-East Asia and Western
Pacific) showed that:
 An average of 8.7% of hospital patients had nosocomial
infections.
 At any time, over 1.4 million people world-wide suffer
from infectious complications acquired in hospital.

7. • The overall increase in the duration of
hospitalization for patients with surgical wound
infections was 8.2 days, ranging from 3 days for
gynaecology to 9.9 for general surgery and 19.8
for orthopaedic surgery.

8. • Nosocomial infections are important contributors
to morbidity and mortality.
• They will become even more important public
health problems with increasing human and
economic impact because of:
 Crowded hospital conditions.
 More frequent impaired immunity (age, illness, treatments).
 More than 70 % of bacteria that cause hospital-acquired
infections are resistant to at least one of the drugs most
commonly used in treatment.
 Emerging pathogens.

9. • Nosocomial infections are the result of three
factors occurring in tandem:
1. High prevalence of pathogens.
2. Large numbers of compromised hosts.
3. Efficient mechanisms of transmission from
patient to patient (chain of transmission).

10. • Hospitals house large numbers of people whose
immune systems are often in a weakened state.
• Medical staff move from patient to patient,
providing a way for pathogens to spread.
• Many medical procedures bypass the body's
natural protective barriers.

11. • The most common sites affected by
nosocomial infections are:
 urinary tract.
 surgical wounds.
 respiratory tract .
 skin (especially burns).
 blood (bacteremia).
 gastrointestinal tract.
 central nervous system.

12. • Overall poor health: advanced age, premature
birth, and concurrent conditions (e.g. chronic
obstructive pulmonary disease COPD, diabetes).
• Compromised immunity: Immunodeficiency,
immunosuppressive therapy, irradiation,
undernourishment etc..

13. • Antimicrobial agents
 Antimicrobial chemotherapy disturbs normal
microbial flora populations eliminating the
competition for pathogens.
 Antibiotics also exert selective pressure which favors
the emergence of resistant strains in hospital
environments.

14. • Surgery: breaches natural barriers to infection
providing microbes with access to sensitive
unprotected tissues and organs.
• Invasive devices: such as intubation tubes,
catheters, surgical drains, and tracheostomy
tubes all bypass the body’s natural lines of
defense.

15. • Contact transmission.
• Droplet transmission.
• Airborne transmission.
• Common vehicle transmission.
• Vector borne transmission.

16. • Contact transmission is the most important and
frequent mode of transmission of nosocomial
infections.
• It is divided into two subgroups: direct contact
and indirect contact.

17. • Direct contact transmission:
 Involves direct contact between body surfaces
which physically transfers microorganisms from
an infected or colonized person (doctor, nurse,
co-patient, etc..) to a susceptible host, during
patient care activities (e.g. feeding).
 Direct contact transmission can occur between
patients.

18. • Indirect-contact transmission:
 Involves contact between a susceptible host and
a contaminated intermediate object.
 Such objects include contaminated instruments,
needles, or dressings, or contaminated gloves
that are not changed between patients.

19. • Droplet transmission:
 Occurs when droplets generated by coughing,
sneezing, talking, or during certain procedures
such as bronchoscopy are propelled through the
air and deposited on a susceptible host.

20. • Airborne transmission:
 Occurs by the dissemination of small droplet
nuclei or evaporated droplets that contain
microorganisms that remain suspended in the air
for a long time.
 Microbes can also be carried by dust particles.
 In this mode of transmission organisms can be
dispersed by air currents in different directions
and long distances (e.g. other rooms, wards etc..)

21. • Common vehicle transmission:
 The mode of transmission of infectious
pathogens from a source that is common to all
the cases of a specific disease, by means of a
medium, or "vehicle," such as water, food, air, or
the blood supply used by a transfusion service to
a number of people.

22. • Vector transmission:
 Occurs when an insect, arthropod, or rodent is
the source of infection.

23. • The source of the infecting organism may be:
 Exogenous: from another patient or a
member of the hospital staff, or from the
inanimate environment in the hospital.
 Endogenous: from the patient’s own flora
which may have acquired new
characteristics from other organisms in the
hospital environment.

24. • A large number of microorganisms are
responsible for hospital infection.
• In fact any microbe may have the ability to
cause an infection in the hospitalized patient.
• Healthcare-associated infections can be caused
by bacterial, viral, fungal, and even parasitic
agents.

25. • The causative microorganisms may be broadly
classified into the following categories:
1. “Conventional” pathogens that could cause
disease in healthy persons in the absence of any
specific immunity to them.

26. 2. “conditional” pathogens that could cause disease
(other than simple localized infections) only in
persons with lowered resistance to infection or
when implanted directly into tissue or normally
sterile area.

27. 3. “Opportunistic” pathogens that could cause severe
disease only in patients with greatly diminished
resistance to infection.
• These distinctions are not clear cut and the
grading of individual pathogens can be
challenged.

28. • According to the United States National Nosocomial
Infections Surveillance (NNIS) System data, the five
most commonly reported pathogens are:
 Escherichia coli (13·7%).
 Staphylococcus aureus (11·2%).
 Enterococci (10·7%).
 Pseudomonas aeruginosa (10·1%).
 Coagulase-negative staphylococci (9·7%).

29. • Urinary tract infection: E. coli, enterococci, and P.
aeruginosa.
• Surgical wound infection: S. aureus, enterococci
and coagulase-negative staphylococci.
• Bloodstream: coagulase-negative staphylococci, S.
aureus, enterococci, E. coli, and Candida spp.
• Lower respiratory tract infection: S. aureus. P.
aeruginosa and Enterobacter spp.

30. • Among patients in the intensive care unit (ICU)
the commonest pathogens were:
 P. aeruginosa (12·4%).
 S. aureus (12·3%).
 coagulase-negative staphylococci (10·2%).
 Candida spp. (10·1%).
 Enterobacter spp. and enterococci (8·6% each).

31. • There is the possibility of nosocomial
transmission of many viruses, including:
 The hepatitis B and C viruses (transfusions, dialysis,
injections, endoscopy).
 Respiratory syncytial virus (RSV), rotavirus, and
enteroviruses (transmitted by hand-to-mouth contact
and via the faecal-oral route).
 Other viruses such as cytomegalovirus, HIV, Ebola,
influenza viruses, herpes simplex virus, and varicella-
zoster virus, may also be transmitted.

32. Source Bacteria Viruses Fungi
Air Gram-positive cocci Varicella zoster Aspergillus
(originating from skin) (chickenpox)
Tuberculosis Influenza

33. Source Bacteria Viruses Fungi
Water •Gram-negative bacteria : Molluscum Aspergillus
(tap Pseudomonas aeruginosa contagiosum
and Aeromonas hydrophilia Exophiala
bath) Burkholderia cepacia Human jeanselmei
Stenotrophomonas maltophilia papillomavirus
Serratia marcescens (bath water)
Flavobacterium
meningosepticum Noroviruses
Acinetobacter calcoaceticus
Legionella pneumophila
•Mycobacteria:
Mycobacterium xenopi
Mycobacterium chelonae
Mycobacterium avium-
intracellularae

34. Source Bacteria Viruses Fungi
Food Salmonella species Rotavirus
Staphylococcus aureus
Clostridium perfringens Caliciviruses
Clostridium botulinum
Bacilluscereus and other
aerobic spore-forming bacilli
Escherichia coli
Campylobacter jejuni
Yersinia enterocolitica
Vibrio parahaemolyticus
Vibrio cholerae
Aeromonas hydrophilia
Streptococcus species
Listeria monocytogenes

35. Methods of prevention of nosocomial infection (and
breaking the chain of transmission ) include:
• Observance of aseptic technique.
• Frequent hand washing especially between
patients.
• Careful handling, cleaning, and disinfection of
equipment.
• Where possible, use of single-use disposable
items.
• Patient isolation.

36. Methods of prevention of nosocomial infection
(continued):
• Avoidance where possible of medical procedures
that can lead with high probability to nosocomial
infection.
• Various institutional methods such as air
filtration within the hospital (Architectural
Design).
• General awareness that prevention of nosocomial
infection requires constant personal surveillance.
• Active oversight within the hospital.

37. • Proper hand washing is the single most important
measure for the Prevention of nosocomial infections.
• Yet, compliance among healthcare workers is
suboptimal ranging from 16% to 81%.
• This is due to a variety of reasons, including:
 Lack of appropriate accessible equipment
 High staff-to-patient ratios
 Allergies to hand washing products.
 Insufficient knowledge of staff about risks and procedures.
 Too long a duration recommended for washing.

38. • Caps and dedicated shoes are required for
operating rooms and aseptic units.
• Masks protect staff against airborne pathogens
and must be used when working in the operating
room, to care for immunocompromised patients,
to puncture body cavities or perform procedures
such as bronchoscopy.
Patients with air-borne pathogens wear masks
when outside their isolation room.

39. • Sterile gloves for surgery, care for immuno-
compromised patients, and invasive procedures.
• Non-sterile gloves should be worn for all patient
contacts where hands are likely to be
contaminated.
• Hands must be washed when gloves are removed
or changed.
• Disposable gloves should not be reused.
• Latex or polyvinyl-chloride are the materials
most frequently used for gloves.
• Quality and duration of use vary considerably
from one glove type to another.

40. According to the WHO guidelines on infection
control, four areas of a healthcare facility are
defined:
• Administrative sections considered as low-risk
areas.
• Regular patient wards as moderate-risk areas.
• Intensive care units, burn units, or isolation units as
high-risk areas.
• Operating rooms as very high-risk areas.
WHO and others have recommended that traffic flow
should be limited in higher risk areas.

41. The microbiologist is responsible for:
• Handling patient and staff specimens to
maximize the likelihood of a microbiological
diagnosis.
• Developing guidelines for appropriate collection,
transport, and handling of specimens.
• Ensuring laboratory practices meet appropriate
standards.
• Ensuring safe laboratory practice to prevent
infections in staff.

42. • Performing antimicrobial susceptibility testing
following internationally recognized methods,
and providing summary reports of prevalence of
resistance.
• Monitoring sterilization, disinfection and the
environment where necessary.
• Timely communication of results to the Infection
Control Committee or the hygiene officer.
• Epidemiological typing of hospital
microorganisms when necessary.