Control of Microbial Growth-1 PDF

Chapter-7: Control of Microbial Growth-1  EXPECTED LEARNING OUTCOME- 1 1. U s i n g terminology, principles of a the n d preservation. pasteurizatio on, appropriate describe steri...

Chapter-7: Control of Microbial Growth-1  EXPECTED LEARNING OUTCOME- 1 1. U s i n g terminology, principles of a the n d preservation. pasteurizatio on, appropriate describe sterilization, decontaminati the disinfectio sanitizatio n, n, n, 2. C o m p a r e and co n tr a s t the methods used to control microbial g r o w t h in daily life, healthcare settings, m i c r o b i o l o g y laboratories, f o o d a n d food production facilities, water treatm ent facilities, a n d other industries. 3. Explain w h y the t y p e a n d n u m b e r of microbes, environmen tal conditions, risk for infection, a n d c o m p o s i t i o n of the item infl uence the selection of an  MICROBIAL CONTROL In certain situations, microbial control is a necessity. For instance, our food system requires sanitary conditions and hospitals require sterilization techniques. Here we see the options available for various levels of microbial control n British physician Joseph Lister ( 1 8 2 7 – 1 9 1 2 ) “saved more lives by the introduction of his system than all the wars of the 19th century together had sacrificed.” –British Medical Journal  A GLIMPSE OF HISTORY Lister was very Impressed with Pasteur’s work, he wondered if ‘minute organisms’ might be responsible for infections He revolutionized surgery: introduced methods to prevent infection of wounds 1. A p p l i e d carbolic a ci d (p h e n o l ) directly o n t o d a m a g e d t i s s u e s , w h e r e it p r e v e n t e d infections 2. I m p r o v e d m e t h o d s further b y sterilizing i n s t r u m e n t s a n d m a i n t a i n i n g clean o p e r a t i n g 5  A GLIMPSE OF HISTORY Until late 1 9 t h patients undergoing century, even risk of developing minor surgeries were at great fatal infections because Physicians did not know their hands could pass diseases from one patient to the next Did not understand airborne microbes could infect open wounds Modern use strict o hospitals procedures t avoid microbial contamination Most surgeries performed with relative s afety 6  Decontamin Fill in the terms in the table ati on below Term Definition The destruction or removal of all Sa nitized microbes through physical or chemical Sterilization means P reser va tio Substantially reduced microbial n population that meets accepted health standards Pasteurizati on Brief heating to reduce number of spoilage organisms, destroy pathogens Disinfectant A chemical that destroys many, but not all microbes. Process of delaying spoilage of foods and other perishable products A process to reduce pathogens to levels considered safe to handle Fill in the terms in the table below Term Definition The destruction or removal of all Sterilization microbes through physical or Decontaminati chemical means o n Sa nitized Substantially reduced microbial Sterilization Sanitized population that meets accepted P reser va tion health standards Pasteurization Brief heating to reduce number Disinfectant Pasteurizatio of spoilage organisms, destroy n pathogens A chemical that destroys Disinfectant many, but not all microbes. Process of delaying spoilage of Preservatio foods and other perishable n products To reduce pathogens to Decontaminati on levels considered safe to handle  1-A P P R O A C H E S T O CONTROL Situational consideratio ns : Microbial control methods depend upon situation and level of control 1  APPROACHES TO CONTROL D a i l y Life Washing and scrubbing with soaps and detergents achieves routine control Soap aids in mechanical removal of organisms Beneficial skin microbiota reside deeper on underlying layers of skin, hair follicles Not adversely affected by regular use Hand washing with soap and water most important step in s t o p p i n g s p r e a d of m a n y infectious 1 diseases  APPROACHES TO CONTROL Hospitals Minimizing microbial population very important Danger of healthcare-associated infections (HAIs)-Nosocomial infections Patients more susceptible to infection May undergo invasive procedures (surgery) Pathogens more likely found in hospital setting Feces, urine, respiratory droplets, bodily secretions Instruments must be sterilized to avoid introducing infection to deep tissues 1  APPROACHES TO CONTROL Microbiology Laboratories Routinely work with microbial cultures using rigorous methods of control Must eliminate microbial contamination to both experimental samples and environment Careful treatment both before (sterile media) and after (sterilize cultures, waste) Aseptic techniques used to prevent contamination of samples, self, laboratory B i o s a f e t y levels r a n g e f rom B S L - 1 ( m i c r o b e s n o t k n o w n to c a u s e disease) to B S L - 4 (lethal p a t h o g e n s for which n o vaccine or tr ea t m en t ex ists) 1 Biosafety levels range from BSL-1 (microbes not known to cause disease) to BSL-4 (lethal pathogens for which no vaccine or treatment exists)  APPROACHES TO CONTROL Food and Food Production Facilities Perishables retain quality longer when contaminating microbes destroyed, removed, inhibited Heat treatment most common and reliable mechanism Can alter flavor, appearance of products Irradiation approved to treat certain foods Chemical additives can prevent spoilage FDA (ADFCA in the Abu Dhabi) regulates because of risk of toxicity Facilities must keep surfaces clean and relatively free of microbes Pharmaceuticals, cosmetics, deodorants must not carry microbial contamination 1  APPROACHES TO CONTROL Water Treatment Facilities Ensure drinking water free of pathogens Chlorine traditionally used to disinfect water Water Treatment Can react with naturally occurring Plant UAE chemicals Form disinfection by-products (DBPs) Some DBPs linked to long-term health risks Some organisms resistant to chemical disinfectants Cryptosporidium parvum (causes diarrhea) Regulations require facilities to minimize DBPs and C. parvum in treated water 1 2-SESLeElCecTtIiOonN complicated O F A N A N TI M IC R O B IA L o f effe ct iv e p ro ce d u re i s Ideal method does not exist PROCEDURE Each has drawbacks and procedural parameters Choice d e p e n d s on numerous factors ? ? ? ? ? ? ? 1 1. Type of microbes 2. Number of microbes 3. Environmental conditions 4. Risk of infection 5. Composition of infected item  SELECTION OF AN ANTIMICROBIAL PROCEDURE 1. Type of M i c r o o r g a n i s m : some are highly resistant microbes Mycobacterium Pseudomonas Non-enveloped species: waxy cell species: resistant to viruses: lack walls makes resistant and can actually lipid envelope; to many chemical grow in some more resistant treatments disinfectants to disinfecta nt s Infectious b u r s a l d i s e a s e vir Bacterial endospores: Protozoan cysts and most resistant, only oocysts: resistant to extreme heat or chemical disinfectants; excreted in treatment destroys them feces; causes diarrheal if ingested Clost ri di um 1 bot ul i num  2. Number of Microorganisms Time for heat, chemicals to kill affected by population size Fraction of population dies during given time interval Large population = more time Removing organisms by washing reduces time Decimal reduction time (the time required for disinfectant to kill 90% of the bacteria) (D value): meaning how long it would take to reduce the bacterial population by 90% Microbial death curves have been developed for many agents and are used in numerous industries 2  SELECTION OF AN ANTIMICROBIAL PROCEDURE 3. Environmental Conditions Exampl Dirt, grease, body fluids e can interfere with heat penetration, action of chemicals Important to thoroughly clean Microorganisms in biofilm are more resistant pH, temperature can influence effectiveness 2 4. R i s k for Medical instruments categorized according to risk for Infection infectious transmitting Semicritical agents instruments contact mucous membranes Critical but do not penetrate N o n - critical items come body tissues instruments in contact Must be free of contact unbroken viruses and skin only Low risk with body vegetative bacteria of transmission tissues Must Countertops, be sterile Few endospores blocked by mucous stethoscopes, Include membranes pressure blood needles scalpel Includes endoscopes cuffs and s and endotracheal tubes 2  SELECTION OF AN ANTIMICROBIAL PROCEDURE 5. Composition of Item Some sterilisation and disinfection methods inappropriate for certain items Heat inappropriate for plastics and other sensitive items Irradiation provides alternative, but damages some types of plastic Moist heat, liquid chemical disinfectants cannot be used to treat moisture-sensitive material 2