Nosocomial infections or Hospital infections

 

NOSOCOMIAL INFECTIONS OR HOSPITAL INFECTIONS

The hospital is ideal environment for the transmission of pathogens, because patients with similar diseases and susceptibilities are present in an enclosed community. Patients share contact with many health care workers each day. In this setting, the ward, health care workers become colonized by organisms adapted to the special environment. New susceptible patients are frequently added to the population and are at risk of colonization and infection.

Respiratory tract, urinary and wound infections are common in all hospital patients. srii mail aslams & merli.

Conditions promote hospital infection

1.      Chronic chest disease, obstructed urinary outflow or previous immune suppression.

2.      Need for invasive devices ( intravenous cannulae, urinary catheters etc)

3.      Effect of surgery

4.      Effect of antibiotic treatment

5.      Effect of immunosuppressive treatment

6.      Exposure to healthcare workers and other patients who may carry or transmit pathogens.

7.      Exposure to pathogens in the environment, especially bedding and food.

Examples for hospital infection

1.      Intravenous infection

2.      Urinary catheter - related infection

3.      Surgery related infection

Control of infection in hospitals

Appropriate organization and effective management protocols are essential to the control of hospital infection.

Few control measures are

1.      Sterilization and Disinfection

2.      . Proper hospital waste disposal

3.      Public awareness

4.      Education and training to hospital staff.

COLLECTION OF SPECIMENS

Laboratory procedure is to identity causative agent for patient illness. Laboratory identification start from specimen collection, handling, transportation and examination like microscopy, staining, biochemical tests etc.

Body fluids, secretions and biopsy material can all be examined to detect pathogens, antigen or products or the immune response to them. Samples from the environment, e.g. water, food or soil, may also be examined. Some sample must be examined at a particular time; for example malaria parasites are best sought at the peak of fever and a short time afterwards, whereas blood for bacterial culture should be taken as the fever begins to rise. Special precautions must be taken to ensure survival of the pathogen and exclude contaminants, e.g. cleaning the perineum before collection of a midstream specimen of urine. Anaerobic species may die if exposed to atmospheric oxygen and survive better in samples of pus, rather than in swab specimens. Every sample or specimen collection has to be done with proper care because if the quality of specimen collected is poor, the result obtained will be unreliable.

REACTION OF BODY TO INFECTION

The infected tissue often serves as an innocent bystander and immunopathology results. This can occur in acute and chronic infections. Overstimulation of cytokine production and complement activation by endotoxins can cause tissue injury in the absence of immune response. Continuously generated antigens released from persisting viable microbes will subsequently elicit humoral antibodies and cell mediated immunity resulting in chronic immunopathology. Certain poorly degradable antigens (e.g. pneumococcal polysaccharide and group A streptococcal cell walls) can maintain immunopathology even in the absence of persistence of live agents. Other bacterial antigens can cross react with host tissues antigens causing the development of autoimmunity (e.g. the M protein of Spyogenes  cross reacts with mammalian myosin). Thus immune response can persist even after the infection and microbial antigens are eliminated.

MECHANISM OF RESISTANCE

Some of the resistance of immune system to infection is

Extracellular parasites - antibodies cause lysis of the organism and/ or their opsonization by phagocytes at which point they are rapidly killed.

Intracellular parasites - they are primarily killed by cell mediated immunity.

Exotoxins - exotoxins can be neutralized by antitoxins. These can be elicited using toxoid vaccines ( toxoids are antigenic but not toxic). This occurs during vaccination against diphtheria.

Certain organisms produce IgA proteases ( H. influenzae, S. pneumoniae, N. gonorrhoeae and N. meningitidis ) this helps survival on external surfaces.

UNIVERSAL PRECAUTIONS AND LABORATORY SAFETY

1.      Specimen may contain hazardous pathogens and must be handled with care.

2.      General precaution is employed to reduce the risk of transmitting blood-borne pathogens.

3.      Personal protective measures has to be taken in collecting and examining specimens.