Nosocomial Infections

APPLIED MICROBIOLOGY Nosocomial Infections By virtue of definition Nosocomial infections are the infections which develop during hospitalization and were not incubating or present at the time of admission to the hospital. The source of causative infecting organism may be exogenous-from another patient or a member of hospital staff or from the inanimate environment in the hospital. It may be endogenous from the patient's own flora which at the time of infection may invade the patient's tissues spontaneously or be introduced into them by surgical operation, instrumental manipulations and nursing procedures The source of causative infecting organism may be exogenous-from another patient or a member of hospital staff or from the inanimate environment in the hospital. It may be endogenous- from the patient's own flora which at the time of infection may invade the patient's tissues spontaneously or be introduced into them by surgical operation, instrumental manipulations and nursing procedures.

Predisposing Factors for Nosocomial infections: • • • • •

Hospital environment is heavily laden with a variety of pathogens. Organisms present in air, dust, antiseptic lotion, water and food or may spread from shedding from the patients. Hospital microbial flora is usually multi-drug resistant. Patients have impaired defence mechanism due to: Disease therapy and investigations in the hospital. Instrumentation in hospitals may introduce infection. Blood, blood products and intravenous fluids may transmit many infections. Accidental inoculation of infectious material

Modes of Spread: Various modes of spread of Nosocomial infections are: a. Airborne b. Infection by contact c. Infections acquired from food. d. Infections associated with water. e. From hospital equipment f. Infections by inoculation.

Common Types of Hospital Infections Include: a. b. c. d. e. f.

Wound infections Urinary tract infections Respiratory infections Skin infections Bacteraemia and septicaemia Gastrointestinal infections.

Organisms causing nosocomial infections: Gram-positive:

Gram-negative:

Staphylococcus aureus Streptococcus pyogenes Staphylococcus epidermidis Streptococcus pneumoniae Clostridium difficile Clostridium perfringens Clostridium tetani

Klebsiella Serratia Enterobacter Proteus Pseudomonas Legionella Escherichia coli Citrobacter

Viruses: Hepatitis B Hepatitis C Hepatitis D HIV Herpes viruses Cytomegalovirus Influenza virus Enteroviruses SARS Co V

Fungi: Aspergillus Candida albicans Parasites: Toxoplasma gondii Entamoeba histolytica Pneumocystis jiroveci (earlier known as P. carinii)

Role of microbiology laboratory in prevention and control of Nosocomial infections include: a. Working with other hospital personnel in infection control activities b. Accurately identifying organisms responsible for nosocomial infection c. Timely reporting of laboratory data relevant to infection control d. Supporting investigation of specific hospital infection e. Conducting studies of hospital personnel or environment.

Diagnosis of Hospital Infection: Aetiological diagnosis is made by routine diagnostic procedures depending upon the suspected

pathogens. Outbreak situation should be dealt with as rapidly as possible. Investigations of an outbreak of nosocomial infection may require isolation and identification of isolates not only in specimens from patients but also in those taken from personnel who might be colonized with the outbreak strain and from environmental objects implicated by epidemiological investigation. The cultures may have to be made from blood products, transfusion fluids, and intravascular therapy equipment, from tubes, containers, surfaces, disinfectants, antiseptics, cultures from floor and equipment and water, ice and other food articles. Use of selective media may be made to reduce the workload in the laboratory. Nosocomial pathogens isolated should be stored for future reference. Environmental or employee surveys are not recommended. Monitoring of sterilization and periodical sampling of disinfected equipment is recommended. Carriers (e.g. typhoid carriers) should be detected and suitably treated.

Prevention of nosocomial infections • • • • • • •

Hand washing Intelligent use of instrumentation Limitation of use of antibiotics Prophylactic antibiotics in specific situations for short periods Limitations of transfusions Barrier precautions Surveillance Frequent change of intravenous lines

Blood Transfusion associated Infections are caused by: Parasites: Plasmodium vivax, P. falciparum P. malariae, P. ovale Toxoplasma gondii Trypanosoma cruzi Wuchereria bancrofti Brugia malayi, Loa loa Leishmania donovani, B. microti

Bacteria: Treponema pallidum, Brucella abortus, Proteus species Esch. Coli, Klebsiella species Micrococcus, Enterobacter Salmonella cholerasuis, Pseudomonas species, Staph. Epidermidis, R. rickettsii

Viruses: Hepatitis B virus, Hepatitis C virus Hepatitis D virus, HIV 1 and 2 HTLV I & II, Hepatitis A virus Cytomegalovirus, Epstein-Barr virus Parvovirus, Ebola virus, Lassa virus,Yellow fever virus Dengue virus

Fungi: Aspergillus Penicillium Hormodendrum