Hospital Infection / Nosocomial Infection / Post operative wound infection / Surgical site Infection

Def –Infection developing in hospitalised patients, neither present nor incubating at the time of admission. These developing infections may become evident during their stay in hospital or after discharge.

Sources-Typically exogenous usually acquired from hospital ecosystem. Includes sources such as health care workers (HCW), patients, food, water, air. They could be iatrogenic or opportunistic.

Factors Contributing-
1. Impaired defence mechanism of patients. Due to disease or due to therapy
2. Hospital environment is unusually laden with pathogens
3. Invasive procedures are performed in the hospital
4. Hospital resident bacteria are usually multi resistant to antibiotics
5. Newer medical procedures like transplantation, implants, radiotherapy etc enhance the chances of infection.

Microbes commonly implicated -
1. Strept. pyogenes – common till 1940s. Very rare now. Spreads to other patients fast.
2. Staph. aureus – Phage type 80/81 was common from 1950-70. Now multi drug resistant phage group III “hospital Staph” is very common.
3. Staph. epidermidis normally considered non-pathogenic, can become pathogenic in special situations like valve replacement/ other prosthesis
4. Group D streptococci –
5. GNBs like E. coli, Klebsiella, Enterobacter, Proteus, Serratia account for the largest %age of infections
6. Salmonella particularly S. typhimurium
7. Ps. aeruginosa and other pseudomonads – intrinsic antibiotic resistance, can grow even in presence of some disinfectants
8. C. tetani –
9. Viruses – HBV, HCV, HIV- thru’ blood transfusions
Viral diarrheas Influenza Herpes Arena
Chicken pox CMV Entero
10. Fungi – Candida, Aspergillus, Mucor
11. Protozoa – Entamoeba histolytica, Pneumocystis carinii, Toxoplasma gondii.

Common types of hospital infection –
1. Wound inf. (post Op) – GNBs, Staph. aureus, Str. epidermidis, Str. pyogenes, Clostridia
2. UTI – Due to indwelling catheter/procedures. Mainly GNBs, Gp D Streptococci
3. Respiratory Infections – Due to aspiration in unconscious patients or due to instrumentation Staph. aureus, GNBs.
4. Bacterimia & Septicemia – Due to infected IV cannulae, phlebitis due to stasis, heart valve implants (Staph epidermidis)

Diagnosis- Routine bacteriology exams like smear, culture, identification & AST.
To check source – Sampling of HCWs patients, inanimate objects, water, air, food etc.
Typing methods for epidemiolgy – Antibiogram, Biotyping, Bacteriocine typing, Phage typing.

Control methods-• Surveillance &Treatment of carriers – must be an ongoing process.
• Sterilisation, disinfecting procedures of hospital to be checked
• Setting up infection control committee
• Formulation & implementation of antibiotic policy
Sir William Osler – ‘Soap, water & plenty of commonsense’ is the best disinfectant’.