Wednesday, July 27, 2011

Hospital – acquired Infection

Definition :
       It is infection acquired while staying in hospital. It meets the following criteria:-
-                     Not found on admission.
-                     Temporally associated with admission or a procedure at a health care facility .
-                      It was not incubating at admission and may be related to a previous procedure or admission to same or other health care – facility e.g HIV acquired from previous blood transfusion .
Routes of infection: -
1)                Self infection (auto genous infection) .
2)                Cross – infection.
3)                Environmental infection
      -Bed linen
       -Air .
      -Moist solutions may be contaminated                         Pseudomonas                                                                                                                       
Factors which promote hospital acquired infection: -
1)                Impaired general host defenses of the patient.
2)                Impaired local host defenses of the patient .e.g injury of skin barrier.
3)                Presence of hospital pathogen which are endemic.
Organisms causing Hospital acquired infection: -
In many hospital but also each hospital has specific endemic or epidemic strains of particular types of organism in certain areas .
In hospitals with large specific units e.g oncology , special care baby units opportunists organisms as well as the common pathogens are likely to cause problem
 Pathogens causing hospital acquired infections include
1)    Conventional pathogen e.g strepto-pyogenes .
2)    Conditional pathogen e.g Bacteroides .
3)    Opportunists pathogen e.g Pneumocystis carinii .
The most common organisms are staph. aureus and staph.epidermidis
-Gram Negative bacilli such as: -
 E.coli is the most frequent single bacterial species associated with hospital acquired infection .
Klebsiella , Proteus species and Pseudomonas are also common cause .
- Fungal and viral infection are only occasionally acquired in hospital .
- Protozoa are rare.
Laboratory diagnosis Of Hospital – acquired Infections :
-Samples collected from the patient includes Blood culture, sputum, tracheostomy wound swabs and other samples. Perform cultured before antibiotics therapies and judged accurately if the isolate is just contamination or already a true pathogen.
-Samples from the environment include all equipments in the ICU and from antiseptic solutions according to the place of environmental assay.
-Typing of the isolated organisms from both patients, environment and personnel by the following typing methods:
1)                Bio typing
2)                Sero typing
3)                Phage typing
4)                Bacteriocine typing
5)                DNA finger printing
2-Surgical wound Infection
1) The type of the wound is the most single factor associated with the development of wound infection . The major types of surgical wounds can be classified as follows : -
-Clean operation wounds in area not involve regions of gastrointestinal tract, respiratory tract or genitourinary tract. It is associated with very low rates of infection 2-5%.
- Contaminated operation Surgery that involves a site with known normal flora (apart from skin) e.g. operation on colon , gall bladder , mouth or vagina .
- Infected operation wounds , the operation site may be infected at time of surgery e.g. incision of an abscess .
2) Surgical team:
- Skill of surgeon
- Good aseptic techniques
- Carriage of staph. aureus .
3) Age and general condition of the patient .
4)    Persistence of local structural abnormal .
5)    Ward factors post operatively
Complication of wound Infections : -
-                     Delayed wound healing
-                     Failure of graft .
-                     Infections of bones , joints , peritoneal cavity .
-                     Septicemia
Types of hospital acquired wound infections include : -
-                     Ward infection
-                     Theatre infection
(How to differentiate ?)
Prevention of theatre infection : -
-                     Protective of  theatre clothing .
-                     Gloves for the hands after chlorhexidine antiseptic solution
-                     Movements of staff should be reduced to a minimum .
-                     Very clean theatre with good managing of the air direction around the operative table .
-                     Disinfect the skin of the patient and many use preoperative baths with hexachlorophene or chlorhexidine detergents .
Prevention of wards infections : -
-                     Isolation rooms for wards should be available for patients infected with MRSA or with severe wound infections especially in high risk surgery e.g. cardio thoracic orthopedic , neuro surgical units and ICU .
-                     Adequate non touch technique for dressing of the wound .
-                     Suitable bad spacing between patients (2.5m)to decrease air or dust spread .
-                     The patient should be admitted for the shortest time before the operation to decrease the chances of colonization or infection with hospital strains .
-                     Restrict the use of prophylactic antibiotics .
-                     Exclude patients with skin disease from the word .
-                     Exclude members of staff with boils , abscess or other infected skin lesions .
If an out breaks occur , how to control ?
-                     Be sure that it is cause by the same epidemic strain with similar antibiotic resistance pattern and phage type .
-                     Isolate the patient .
-                     The medical staff shown to be carrier should temporarily cease the work and use chlorhexidine on the affected area with all hygiene measure .
-                     Close the ward in severe cases .
-                     Use vancomycin for therapy .
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