Page 34 - MNU-PM502- Pharmaeutical Microbiology Theoritical Book

Pharm D- Clinical Pharmacy Program Third Level Pharmaceutical Microbiology& Antimicrobials (PM 502)

Most lethal at wavelength of 260 nm that can be produced by mercury vapor
lamps.

This is the wavelength most actively absorbed by DNA.

• UV radiation causes the formation of thymine

dimers on DNA.

• This dimerization inhibits DNA replication, which
may lead to death of the organism

• Low penetration power.
• poor penetrability of normal packaging materials

• Can not penetrate dirt, glass, metal and plastic
• unsuitable for sterilization of pharmaceutical dosage forms

• used for
- Air Disinfection - Water Disinfection -Food Disinfection
- Surface Disinfection (Hospitals: operating rooms, Patient rooms)

Operators present in an irradiated room should wear appropriate protective
clothing and eye shields

B- Ionizing Radiation (Gamma irradiation)

X-ray and gamma rays are the commonly used
ionizing radiation for sterilization. Ionizing radiation

causes DNA damage (direct action: breakage,
indirect: free radicals) leading to death of

microorganisms.

Gamma irradiation

• The most popular form of radiation sterilization

• derived from a cobalt-60 source which has a half-life of 5.27 years.

• Penetrate deeply but would essentially.

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