Disinfection and Preservation PDF

# Disinfection and Preservation ## Dr Laura Urbano - F154 Hillside House - Email: [email protected] - Tel: 01707 281372 ## Learning Objectives - Describe main preservation techniques - Discuss factors affecting the efficiency of preservation processes - Assess the quality assurance of preserva...

# Disinfection and Preservation ## Dr Laura Urbano - F154 Hillside House - Email: [email protected] - Tel: 01707 281372 ## Learning Objectives - Describe main preservation techniques - Discuss factors affecting the efficiency of preservation processes - Assess the quality assurance of preservation processes ## Preservation ### From what? - Antimicrobial agents ## What is the difference between these chemical agents? - **Antiseptics:** Treat living tissues - Harmless enough to be applied to the skin and mucous membrane - Mercurials, Ag nitrate, iodine solution, alcohols, soaps - **Biocides:** General term for antimicrobial chemicals but it excludes antibiotics - **Disinfectants:** Treat inanimate objects (too toxic for human use) - E.g. Cl, hypochlorites, quaternary NH4 compounds. - **Preservatives:** Treat pharmaceuticals and cosmetics ## Disinfectant Choice ### The microbe/s - G-ve more resistant than G+ve to disinfectants and antiseptics - Bacteria in stationary-phase generally are more resistant than Log-phase - Mycobacteria, protozoan cysts and oocysts are very resistant to disinfectants and antiseptics - Non-enveloped viruses are generally more resistant than enveloped viruses to disinfectants and antiseptics - Pseudomonas can metabolize many chemicals ### The Agent ### The Environment - Water-containing nonsterile products and for multidose sterile products ### Static vs Cidal - Damage lipids & proteins, affect cytoplasmic membrane, leakage of cellular materials denature microbial enzymes, blocks metabolism. ## Disinfectant Choice ### Consider the microbe | Most Resistant | Least Resistant | |---|---| | Prions | Viruses with lipid envelopes | | Endospores of bacteria | | | Mycobacteria | | | Cysts of protozoa | | | Vegetative protozoa | | | Gram-negative bacteria | | | Fungi, including most fungal spore forms | | | Viruses without envelopes | | | Gram-positive bacteria | | ## Disinfectant Choice ### Agents Factors - Spectrum of activity - Contact time - Shelf life - Concentration or dose of agent - Dilution and inactivation - More is not always better ## Disinfectant Choice ### Agents Factors | Type of Agent | Gram +ve | Gram-ve | Mycobacteria | Spores | Lipid Viruses | Non-Lipid Viruses | |---|---|---|---|---|---|---| | Alcohol (70%) | ++ | ++ | + | - | ++ | | | Chlorhexidine | ++ | + | - | - | ++ | - | | Formaldehyde | ++ | ++ | (++) slow | (++) slow | (++) slow | (++) slow | | Gluteraldehyde | ++ | ++ | (++) slow | (++) slow | ++ | (++) slow | | Hypochlorites | ++ | ++ | + | ++ | ++ | ++ | | Iodophors | ++ | ++ | + | + | ++ | + | | Organo-mercurials | ++ | ++ | - | - | ++ | - | | Phenolics | ++ | (+) | + or - | - | ++ | - | | QACS | ++ | (+) | - | - | ++ | - | | Tego Compounds | ++ | (+) | - | - | ? | - | ## Theory of Preservation - Ensure contamination does not occur - Reduce the moisture content (Aw) - Lyophilisation, dry preparations - Remove or sequester nutrients - Keep to low levels, use EDTA - Extreme temperature/pH - Supplementation with antibacterial or preservative compounds - Use is limited by toxicity - Few new preservatives emerging - Synergy - Broader spectrum activity - Lower concentration to reduce toxicity ## Preservatives ### Phenolics - Examples include phenol, cresol, chloroxylenol, triclosan - Addition of chlorine and methyl groups eliminates the toxic corrosive properties and enhances/prolongs the antimicrobial activity - Active against vegetative bacteria and fungi - Inactivated by dilution and organic matter - Cause cell lysis and coagulation of cell contents - Examples: phenol used as 1% w/v in lotions, gargles, ear drops - Chlorocresol - bactericide in injections and o/w creams ## Preservatives ### Alcohols - Kills bacteria, no effect on endospores or viruses - Disrupts cytoplasmic membrane of bacteria and functioning of membrane proteins - Examples include - Phenylethanol - eye drops, contact lens solutions - Bronopol - shampoos - Benzyl alcohol - injections ## Preservatives ### Quaternary Ammonium Compounds - Cationic surface active compounds - Active at high dilutions and virtually non-toxic - Infer with cell permeability and cell lysis - Examples: Used in skin antiseptics, contact lens cleaning solution, eye drops and injections ## Preservatives ### Biguanides - Effect cell membrane causing leakage of intracellular components - Active against bacteria - Little activity against endospores and viruses - Examples: chlorhexidine, polyhexamethylene biguanide (PHMB) used in eye drops and contact lens solutions ## Preservative Efficacy Testing ### Table 5.1.3.-1. - Parenteral preparations, eye preparations, intrauterine preparations and intramammary preparations | Log Reduction | 6h | 24h | 7d | 14d | 28d | |---|---|---|---|---|---| | Bacteria (A) | 2 | 3 | NR | | | | Bacteria (B) | 1 | 3 | | | NI | | Fungi (A)| | 2 | | | NI | | Fungi (B) | | 1 | | | NI | **NR**: no recovery **NI**: no increase in number of viable micro-organisms compared to the previous reading ### Table 5.1.3.-2. - Ear preparations, nasal preparations, preparations for cutaneous application and preparations for inhalation | Log Reduction | 2d | 7d | 14d | 28d | |---|---|---|---|---| | Bacteria (A) | 2 | 3 | | NI | | Bacteria (B) | | 3 | | NI | | Fungi (A) | | | 2 | NI | | Fungi (B) | | |1 | NI | **NI**: no increase in number of viable micro-organisms compared to the previous reading ### Table 5.1.3.-3. - Oral preparations, oromucosal preparations and rectal preparations | Log Reduction | 14d | 28d | |---|---|---| | Bacteria | 3 | NI | | Fungi | 1 | NI | **NI**: no increase in number of viable micro-organisms compared to the previous reading. ## Consequences of Microbial Contamination - A formulation may be affected by microbial contaminants in different ways - Dependent on microorganisms present - Depends on properties and content of formulation - Some preservatives can be a ready source of nutrition for some microorganisms, especially if levels become depleted or if aromatic structure ## Essential Knowledge - Knowledge of agents available, mechanism of action, activity, uses and limitations - The disinfectant chosen should provide protection against likely contamination - Preservatives should not be added to mask deficiencies in manufacturing processes and should chosen specifically to provide correct protection and be integral to the formulation ## Learning Objectives - Describe main preservation techniques - Discuss factors affecting the efficiency of sterilisa preservation processes - Assess the quality assurance of preservation processes ## References and Additional Resources 1. Pharmaceutics: the design and manufacture of medicines / edited by Michael E. Aulton., 3rd edi, Churchill Livingstone, 2007. 2. Hugo and Russell's pharmaceutical microbiology edited by Stephen P. Denyer, Norman A. Hodges, Sean P. Gorman, 7th Ed., Blackwell Science, 2004 3. http://www.americanpharmaceuticalreview.com/Featured‐Articles/38886‐Antimicrobial‐Preservatives‐Part‐One‐Choosing‐a‐Preservative‐System/ 4. http://www.americanpharmaceuticalreview.com/Featured‐Articles/38885‐Antimicrobial‐Preservatives‐Part‐Two‐Choosing‐a‐Preservative/ 5. http://www.americanpharmaceuticalreview.com/Featured‐Articles/38874‐Antimicrobial‐Preservatives‐Part‐Three‐Challenges‐Facing‐Preservative‐