indoors into a health care facility by any of a number of vehicles (e.g. people, air currents, water, construction materials and equipment), the attendant microorganisms can proliferate in various indoor ecological niches and

 

¾ Chloroxylenol

¾ Terpineol

¾ Triclosan

¾ Isopropyl alcohol

¾ Cetrimide.

Skin Preparatives

Long before the discovery of bacteria and the introduction

of antiseptic surgery, a variety of substances had been

Sterilization 37

used to prevent infections. Pasteur’s initiation of the

science of bacteriology was probably the foundation of the

development and use of skin antisepsis. Joseph Lister an

academic surgeon who was greatly influenced by Pasteur’s

works and bacteria causing infection causing infection

ventured into ‘antiseptic surgery’. His solution was to apply

some chemical substance ‘in such a manner that not

only would the microbes already present be destroyed,

but also the germ killing substance would act as a barrier

between the wound outside source of infection’. Lister hit

on the idea of using carbolic acid, which was first used on

compound fractures. Later, the method was refined by use

of different concentrations of carbolic acid and extended

to instruments, ligatures and even room air.

Among surgical patients, surgical side infections (SSIs)

were the most common nosocomial infection accounting

for 38% of all such infections. When surgical patients with

nosocomial SSI died, 77% of the deaths were reported to

be related to the infection, and the majority (93%) were

serious infections involving the organs or spaces accessed

during the surgery. Microbial contamination of the

surgical site is a necessary precursor of SSI. Quantitatively

it has been shown that if a surgical site is contaminated

with > 105

 microorganism per gram of tissue, the risk of

SSI is markedly increased. For most SSIs, the source of

pathogens is the endogenous flora of the patient’s skin,

mucous membranes or hollow viscera. When mucous

membranes or skin is incised, the exposed tissues are

at risk of contamination with endogenous flora. These

microorganisms are usually aerobic gram-positive cocci

(e.g. staphylococci) but may also include fecal flora (e.g.

anaerobic bacteria and gram-negative aerobes). The

flora may also change as per the site of the incision of the

type of organ exposed during surgery. An important SSI

prevention measure would include techniques directed

at reducing microbial flora by localized skin prepping

(at the surgical site). Before the skin preparation of a

patient is initiated, the skin should be free from gross

contamination (i.e. dirt, soil or any other debris). The

patient’s skin is prepared by applying an antiseptic in

concentric circles, beginning in the area of the proposed

incision. This procedure is a vital step in removing all

transient microorganisms and ensuring an extremely sub

minimal population of resident flora (Table 2.1).

Since the days of Lister, antiseptic development

has been in a state of flux. Despite this, SSIs remain a

substantial cause of morbidity and mortality among

hospitalized patients. Thus, to reduce the risk of SSI, a

systematic but realistic approach must be applied with the

awareness that this risk is influenced by characteristics of

the patient, operation, personnel and hospital.

Environment and Surfaces

The health care environment contains a diverse

population of microorganisms, but only a few are

significant pathogens for susceptible humans. Microorganisms are present in great numbers in moist organic

environments, but some can also persist in dry conditions.

Although, pathogenic microorganisms can be detected

in air and water and on fomites, assessing their role in

causing infection and disease is difficult. The surface

and environment therefore would be considered

one of a number of potential reservoirs for the pathogen

but not the ‘de facto’ source of exposure. An understanding

of how infection occurs after exposure based on the

principles of the “chain of infection”, is important in

evaluating the contribution of the environment to health

care associated diseases.

Chain of infection components comprises of (a)

adequate number of pathogenic microorganisms,

(b) pathogenic microorganisms of sufficient virulence,

(c) a susceptible host, (d) an appropriate mode of

transmission or transferal of the microorganism in sufficient

numbers from the source to host, (e) the correct portal or

entry into the host. The presence of the susceptible host is

one of these components that underscore the importance

of healthcare environment and opportunistic pathogens

on fomites and in air and water. All of the components of

the ‘chain’ must be operational for the infection to occur.

A variety of airborne infections in susceptible hosts

can result from exposure to clinically significant microorganisms that are released into the air when environmental

reservoirs (i.e. soil, water, dust and decaying organic

TABLE 2.1: Summary of CDC recommendations

1. Preoperative:

Preparation of the patient

Hand/forearm antisepsis

Management of infected/colonized surgical personnel (Anti

-microbial prophylaxis)

2. Intraoperative:

Ventilation

Cleaning and disinfection of environmental surfaces

Microbiologic sampling

Sterilization of surgical instruments

Surgical attire and drape

Asepsis and surgical technique

3. Postoperative incision care

4. Surveillance

Source: CDC guidelines for prevention of SSI, 1999.

38 Concise Book of Medical Laboratory Technology: Methods and Interpretations matter) are disturbed. Once these materials are brought

indoors into a health care facility by any of a number of

vehicles (e.g. people, air currents, water, construction

materials and equipment), the attendant microorganisms

can proliferate in various indoor ecological niches and

if subsequently disbursed into the air, serve as a source

for airborne health care associated infections. It can be

observed that the infection cycle then is completed very

quickly resulting in extensive infections.

As a result of advances in medical technology and

therapies (e.g. cytotoxic chemotherapy and transplanta -