Bacteriology Microbiology

1. Infection Control

2. Patient may acquire infection before admission to the
hospital = Community acquired infection.
Patient may get infected inside the hospital =
Nosocomial infection.
It includes infections
not present nor incubating at admission,
infections that appear more than 48 hours after admission,
those acquired in the hospital but appear after discharge
also occupational infections among staff.
The risk of infection is always present.

3. INFECTION
• Definition: Injurious contamination of body or parts
of the body by bacteria, viruses, fungi, protozoa and
rickettsia or by the toxin that they may produce.
 Infection may be local or generalized and spread
throughout the body.
 Once the infectious agent enters the host it begins
to proliferate and reacts with the defense
mechanisms of the body producing infection
symptoms and signs: pain, swelling, redness,
functional disorders, rise in temperature and pulse
rate and leucocytosis.

4. Frequency of Nosocomial Infection
 Nosocomial infections occur worldwide.
 The incidence is about 5-8% of hospitalized
patients, 1/3 of which is preventable.
A high frequency of N.I. is evidence of poor
quality health service delivered.

5. Impact of Nosocomial Infections
They lead to functional disability and
emotional stress to the patient.
They lead to disabling conditions that reduce
the quality of life.
They are one of the leading causes of death.
The increased economic costs are high:
Increased length of hospital stay (SSI - 8.2
days), extra investigations, extra use of drugs
and extra health care by doctors and nurses.

6. Organisms causing N.I. can be transmitted to
the community through discharged patients,
staff and visitors. If organisms are multi-
resistant they may cause significant disease
in the community.

7. Nosocomial Infection Sites
Urinary tract infection: most common type of
N I (30-40% of reported cases), associated
with an indwelling urinary catheter or
instrumentation.
Lower respiratory and surgical wound
infections are the next ( each about 15%).
Less frequent include bacteraemia (5%),
intravenous site infection, gastrointestinal
tract and skin infections.

8. Criteria of Nosocomial Infections
Surgical site infection Any purulent discharge, abscess or
spreading cellulitis at the surgical
site during the month after operation
Urinary infection Positive urine culture (1 or 2
species) with at least 100000
bacteria/ml, with or without clinical
symptoms
Respiratory infection Respiratory symptoms with at least
2 signs: cough; purulent sputum;
new infiltrate on chest, appearing
during hospitalization
Vascular catheter
infection
Inflammation, lymphangitis or
purulent discharge at the insertion
site
Septicaemia Fever or rigours and at least one
positive blood culture

9. Factors Influencing N.I.
The microbial agent
Patient susceptibility
Environmental factors

10. Microbial Agent
Many sick people are treated in a closed area;
micro-organisms, frequent contact between
carriers & susceptible, contaminated waste,
equipment and supplies to be handled.
Developing of clinical disease depends on
organism s virulence, infective dose and
patient resistance

11.  Bacteria are the most common pathogens.
1. Commensal bacteria: found in normal flora of
healthy humans, prevent pathogenic bacterial
colonization eg skin, colon, vagina
2. Pathogenic bacteria: have great virulence and
cause infection as :
- Anaerobic gram +ve rods e.g Clostridium
causing gangrene.
- Gram +ve bacteria: Staph. aureus found on
skin &nose. - Beta -hemolytic Strep.
- Gram -ve bacteria as E.coli, Proteus, Klebsiella.
- legionella species.

12. Patient Susceptibility
Age: infants and old age have decreased
resistance to infection.
Immune status: Patients with chronic
diseases as malignancy, leukaemia,
diabetes mellitus, renal failure or AIDS
have increased susceptibility to infection.
Immunosuppressive drugs or irradiation

14. Environmental Factors
 Healthcare settings are environment
where both infected persons and persons
at high risk of infection congregate.
 Crowded conditions within hospital,
frequent transfers of patients between
units.
 Microbial flora may contaminate objects,
devices and materials which subsequently
contact susceptible body sites of patients.

15. Transmission
• Where do nosocomial infection come from?
 Endogenous infection: When normal
patient flora change to pathogenic bacteria
because of change of normal habitat, damage
of skin and inappropriate antibiotic use.
About 50% of N.I. Are caused by this way.
 Exogenous cross-infection: Mainly
through hands of healthcare workers, visitors,
patients.

16. Exogenous environmental infections:
several types of micro-organisms survive well in
the hospital environment (hospital flora):
* In water, damp areas and occasionally in
sterile products or disinfectants eg pseudomonas,
Acinetobacter, Mycobacterium.
* On items such as linen, equipment and supplies
* In food.
* In fine dust and droplet nuclei
Some procedures that save life may increase
risk of infection e.g urinary catheters, I.V.L
inhalation therapy, surgery.
Inappropriate use of antibiotics.

17. PROTECT YOURSELF
THROUGH IMMUNISATION
Immunisation
BCG
Hepatitis B
Tetanus
Rubella
Varicella
Influenza