challenge to health care professionals and manufactures alike. Numerous disinfectants are available in the market; glutaraldehyde continues to be the most commonly used disinfectant owing to its effectiveness and broad range of

 

tion medicine), more patients are becoming immunocompromised in the course of treatment and are therefore

at an increased risk of acquiring health care associated

opportunistic infections. Trends in health care delivery

(e.g. early discharge of patients from acute care facilities)

also change the distribution of patient populations and

increase the number of immunocompromised patients in

non-acute care hospitals.

The environment is often overlooked as a passive player

in hospital acquired infections owing to the emphasis laid

on other more risky modes of transmission. However, with

the ever-changing face of modern medicine disrupting the

existing environmental stability could open a Pandora’s

box of dangerous environmentally linked infections.

A couple of such cases observed in the recent years

(a) transmission of infections caused by Mycobacterium

tuberculosis, Varicella Zoster Virus (VZV), and Measles

facilitated by inappropriate air-handling systems in health

care facilities; (b) disease outbreaks caused by Aspergillus

species, Mucoraceae, and Penicillium species associated

with the absence of environmental controls during periods

of health care facility associated construction; (c) infections

and/or colonization of patients and staff with vancomycin

resistant. Enterococcus faecium [VRE] and Clostridium

difficile acquired indirectly from contact with microorganisms present on environmental surfaces in health

care facilities; and (d) outbreaks of pseudoepidemics

of Legionellae, Pseudomonas aeruginosa, and the nontuberculous mycobacteria (NTM) linked to water and

aqueous solution in health care facilities.

In many instances, it is still difficult to decide on the

appropriate method of decontamination even after taking

into consideration the nature and risk involved. However,

it is useful to remember that the risk of transmitting

infection from a surface that has been thoroughly

cleaned and disinfected is very small. Thorough cleaning

removes potential bacterial nutrients (organic matter)

as well as a significant load of bacteria. Studies have

shown prior cleaning achieves approximately a 4-log

reduction of microorganisms. Disinfection achieves a

99.9% reduction if performed using the right disinfectant

as per the standardized procedure. Disinfection of hard

surfaces is performed by combination of a cleaning and

disinfecting agent. Thus, it can be seen that cleaning is an

essential prelude effective disinfection and one should not

underplay the importance of either of the processes.

Various agents used are:

¾ Silver nitrate

¾ H2O2 (hydrogen peroxide)

¾ Benzalkonium chloride

¾ Isopropyl alcohol.

Instruments

Formal procedures for sterilization of instruments and

medical devices, liquids, and other materials used in

hospitals have developed over a century. The initiation

of these procedures began during a time when microorganisms were strongly implicated in the transmission

of infectious diseases and hence the need to use sterile

materials in surgery and other hospital related activities.

Although the concept of hospital infection control was in

its infancy, hospitals and medical-device industry began to

sterilize instruments and materials used to treat patients.

Earlier methods of sterilization used different forms

of heat such as dry heat, moist heat to sterilize medical

devices and instruments. The 50s marked the increased

use of heat sensitive devices and hence the need for low

temperature sterilization methods or liquid chemical

germicides.

Sterilization and disinfection are two terms, which are

often used interchangeably. However, sterilization is a

more absolute term, which implies complete elimination

or destruction of all forms of microbial life. Disinfection on

the other hand describes a process that eliminates many

or all pathogenic microorganisms, with the exception of

bacterial spores. The success of these processes is largely

dependent on the right method of choice, which often

became a difficult decision for health care professionals.

In 1968, Dr EH Spaulding devised a rational classification

scheme that could be used to decide whether a medical

instrument needs to be sterilized or disinfected. His

classification was extremely simple yet logical and has

been endorsed and adapted by the CDC, FDA and

numerous other reviewers and professional societies

today. The Spaulding classification revolved around the

central idea that medical devices or items need to be

categorized based on the risk of infection involved in their

use (Table 2.2 and 2.3).

Sterilization 39

Undoubtedly, the Spaulding classification is an oversimplification especially when applied to the new mantra

of modern medicine endoscopes.

Endoscopes are notorious to nosocomial infections.

Reports of nosocomial infections related only to

endoscopes state a wide variety of infections transmitted

by various scopy procedure like gastrointestinal endoscopies and bronchoscopy. The clinical spectrum of

these infections ranged from asymptomatic colonization

to death. Major reasons for transmission are inadequate

cleaning and improper selection of a disinfectant. Very

often the fear of the dreaded blood borne infectious

disease like HIV and HBV results in overlooking the

more challenging microorganisms. It thus, becomes

helpful to know the resistance pattern of some frequently

encountered microorganisms.

Prions Hard to kill

Spores

Mycobacteria

Non-enveloped viruses

Fungi

Bacteria

Enveloped viruses Easy to kill

As more and more heat labile instruments enter the

medical arena, foolproof disinfection of these instruments

owing to their heat sensitivity and complex structures is a

challenge to health care professionals and manufactures

alike. Numerous disinfectants are available in the market;

glutaraldehyde continues to be the most commonly used

disinfectant owing to its effectiveness and broad range of

material compatibility. Other chemicals like per acetic acid,

hydrogen peroxide and more recently orthophthaldehyde

are also used for high-level disinfection or cold sterilization.