NURS 218 MICROBIOLOGY IN NURSING Control and Treatment

NURS 218 MICROBIOLOGY IN NURSING Control and Treatment Microbial Infections

Learning Objectives At the end of the 2 hour evocative discussion, the students will be able to: • Define the different terminologies related to the control of microbial growth • Differentiate the various actions of microbial control agents • Identify methods (physical and chemical) used to control microbial growth • Understand the existence of antibiotics and its role in microbial control • Identify the significance of antibiotic resistance and safety in ensuring proper control of microbial growth • Distinguish common microbial disease of the skin and the eye.

Outline • Control of Microbial Growth • Terminologies • Actions of Microbial Control Agents • Physical Methods of Microbial Control • Chemical Methods of Microbial Control • Antibiotics • Antibiotic Resistance • Antibiotic safety • Microbial Infections • • Bacterial Disease of the Skin Viral Disease of the Skin Fungal diseases of the Skin Parasitic Infestation • Microbial Disease of the Eye

INTRODUCTION • Scientific control of microbial growth began when the work of the scientists led to the belief that microbes were a possible cause of diseases. • This was used Dr. Semmelweis and Dr. Lister to develop the first microbial control practices for medical surgery for prevention of microbial contamination of surgical wounds. • This included: • Handwashing with microbe-killing chloride of lime • Using the techniques of aseptic surgery • Over the last century, scientists continue to develop a variety of physical methods and chemical agents to control microbial growth

I. CONTROL OF MICROBIAL GROWTH • The control of microbial growth can prevent infections and food spoilage. • Terminologies: • Sterilization • Is the process of removing or destroying all microbial life on an object. • Commercial Sterilization • Is heat treatment of canned foods to destroy C. botulinum endospores • Disinfection • Is the process of reducing or inhibiting microbial growth on a nonliving surface • Antisepsis • Is the process of reducing or inhibiting microorganisms on living tissue • Sepsis • Indicates bacterial contamination • Asepsis • The absence of significant contamination.

Treatments that cause outright death of microbes: • Biocide or germicide – kills microorganisms except endospores • Fungicide – kills fungi • Virucide – inactivates viruses

Actions of Microbial Control Agents 1. Alteration of Membrane Permeability • Plasma membrane located inside the cell wall actively regulates the passage of nutrients into the cell and the elimination of wastes from the cell • Certain chemical control damages the lipids or proteins of the plasma membrane which causes cellular contents to leak and interfere with cell growth. • This process alters permeability.

2. Damage to Proteins and Nucleic Acids • thought of as “little bags of enzymes” are primarily protein (vital for cellular activities) • Nucleic Acids are carriers of the cell’s genetic information • Certain microbial control agents damage cellular proteins resulting to denaturation of the protein. • Damage to the nucleic acids results to no cell replication.

Physical Methods of Microbial Control • Heat • Frequently used to kill microorganisms by denaturing enzymes • Heat methods: • Moist heat sterilization – kills by denaturing( process of destroying the characteristic properties of proteins or other biological macromolecule) enzymes • Boiling – kills many vegetative cells (actively growing cells of bacterium) and viruses within 10 minutes • Autoclaving (steam under pressure) – is the most effective method of moist heat sterilization where the steam must directly contact the material to be sterilized • Pasteurization - done by using a high temperature for a short time ( 72 degrees celcius for 15 seconds) to destroy pathogens without altering the flavor of food • Dry heat sterilization – kills by oxidation; includes direct flaming, incineration, and hot-air sterilization.

• Filtration • Is the passage of a liquid or gas through a filter with pores small enough to retain microbes • Kills microorganisms by coagulating proteins (denaturation) caused by a breakage of the hydrogen bonds • Low Temperature • Effectiveness depends on microorganisms and intensity of application • 0 -7 degrees Celsius – most microorganisms do not reproduce at ordinary refrigerator • Subzero temperature – many microbes survive (but do not grow); this is used to store foods

• High Pressure • Denatures proteins in vegetative cells • Dessication • Certain microorganisms cannot grow but can remain viable in the absence of water • Viruses and endospores can resist dessication

• Osmotic Pressure • Uses high concentration of salts and sugars to preserve food • Salts and sugars in high concentration creates a hypertonic environment that causes the water to leave the microbial cells • Radiation • Effects depends on wavelength, intensity and duration • Ionizing radiation – has high degree of penetration • Ultraviolet radiation – has low degree of penetration • Microwaves – kills microbes indirectly as materials get hot

Chemical Methods of Control of Microbial Growth • Chemical Agents • Antiseptics • Used on living tissue • Disinfectants • Used on inanimate objects • Types: Phenol and Phenolics - exert their action by injuring plasma membranes • Bisphenols – derivatives of phenols; e. g. p. Hiso. Hex ( used for surgical and hospital microbial control procedures; triclosan ( an ingredient in antibacterial soaps • Biguanides – damage plasma membranes of vegetative cells •

• Halogens – particularly iodine and chlorine are affective antimicrobial agents • Alcohols – effectively kill bacteria and fungi but not endospores and nonenveloped virus; most commonly used is ethanol and isopropanolol • Heavy metals and compounds – silver, mercury and copper in small amounts have the ability to exert antimicrobial activities • Surface active Agents – can decrease surface tension among molecules of a liquid; include: • soaps and detergents ( have limited germicidal action but assist in removing microorganisms) • Acid – anionic sanitizers – very important in cleaning food processing facilities • Chemical food preservatives – frequently added to foods to retard spoilage

Antibiotics • Discovered by Dr. Fleming while looking at a mold that inhibited the growth of a bacterium and later named the mold as Penicillium chrysogenum • Thus, penicillin is an antibiotic produced by fungus. • Antibiotics are critical in treating bacterial infections • A few antibiotics are produced by endospore-forming bacteria such as Baccilus. • They are discovered through identifying and growing colonies of antibiotic producing organisms.

Antibiotic resistance • A phenomenon in which merely effective medications have less and less impact on bacteria • Results from years of overuse and misuse of antibiotics • Mechanisms of Resistance • Enzymatic Destruction or Inactivation of the drug • Affects antibiotics that are natural products such as penicillin • Prevention of Penetration to the target site within the microbe • Gram negative bacteria are more resistant to antibiotics due to the nature of their cell wall, restricting absorption of many molecules to movements through the porins membranes • Porins is a class of proteins whose molecules can form channels (large enough to allow the passage of small ions and molecules) through cellular membranes.

• Alteration of the Drug’s Target site • Several antibiotics utilize a mode of action that inhibits protein synthesis at target site, minor modifications on this site neutralize the effect of antibiotics • Rapid Efflux (Ejection) of the antibiotic • Certain protein in plasma membranes of gramnegative bacteria acts as a pump that expel antibiotics that prevent them from reaching an effective concentration

Antibiotic Safety • The risk ( side effects) versus the benefit (curing an infection) must be evaluated before antibiotics are used. • A pregnant woman should take only those antibiotics that are classified as presenting no evidence of risk to the fetus • It is always wise to consult a doctor prior to taking any antibiotics.

II. Microbial Infections

BACTERIAL DISEASE OF THE SKIN • Staphylococcal Skin Infections • Staphylococci – are spherical gram-positive bacteria that form irregular clusters like grapes • Coagulase-negative strains are very common in the skin • S. aureus is the most pathogenic of the staphylococci • Is a permanent resident of the nasal passages; thus it is transported from there to the skin where it enters the natural openings like the hair follicles

• Example: • Folliculitis - often occur as pimples • Sty – infected follicle of an eyelash • Furuncle (boil) - a type of abscess ( a localized region of pus surrounded by inflamed tissue. • Carbuncle – extensive damage, hard, round deep inflammation of tissue under the skin • Can survive for months on surfaces • An infection of the S. aureus stimulates vigorous inflammatory response

• Streptococcal Skin Infections • Gram-positive spherical bacteria which secretes toxins and enzymes • Most common human pathogens is group A. streptococci (GAS) • Example: necrotizing fasciitis – destroys tissue as rapidly as a surgeon can remove it. • Infections by Pseudomonads • Aerobic gram-negative rods that are widespread in soil and water • Capable of surviving in any moist environments • Resistant to many antibiotics and disinfectants • Example: Pseudomonads dermatitis – self-limiting rash of about 2 weeks duration, often associated with swimming pools and pool-type saunas and hot tubs. • Otitis externa or swimmer’s ear – painful infection of the external ear canal leading to the eardrum

• Acne • most common skin disease in humans • classification: • Comedonal (mild) acne – usually treated with topical agents • Inflammatory (moderate) acne – usually treated with antibiotics • Nodular cystic (severe) acne – treated effectively by isotretinoin

Viral Diseases of the Skin • Systemic and transmitted by respiratory and other routes • Warts ( papillomas) • benign skin growths • transmitted by contact from one person to another • Smallpox ( Variola) • transmitted by the respiratory route which infect many internal organs before moving into the bloodstreams • infecting the skin and producing more recognizable symptoms • those who recover retained disfiguring scars

• Chickenpox (Varicella) and Shingles (Herpes Zoster) • a relatively mild disease usually contacted in childhood • is a result of an initial infection with herpesvirus varicella-zoster • acquired when the virus enters the respiratory system and the infection localizes in skin cells after about 2 weeks • Measles (Rubeola) • extremely contagious viral disease spread by the respiratory route • MMR vaccine has almost eliminated this disease in the U. S. • Rubella (German Measles) • much milder viral disease and often goes undetected • Usual symptoms are macular rash of small red spots and a light fever.

• Fungal disease of the Skin and Nails • Tinea capitis – ringworm of the scalp; infection tends to expand circularly usually transmitted by fomites (objects or materials which are likely to carry infection, such as clothes, utensils, and furniture. ) • Tinea pedis – ringworm of the feet or athlete’s foot; moisture in such areas favors fungal infection • Tinea unguium – ringworm of the fingernails or toenails

• Parasitic Infestation of the skin • Scabies • Involves intense local itching caused by tiny mite Sarcoptes scabei burrowing under the skin to lay its eggs. • Transmitted by intimate contact, most often seen in family members, nursing home residents and teenagers • Pediculosis (Lice) • Infestations by lice • Caused by Pediculus humanus capitis, lice requires blood and feed several times a day; eggs are attached to the hairshaft close to the scalp

MICROBIAL DISEASE OF THE EYE • Inflammation of the Eye Membranes: • Conjunctivitis • Is an inflammation of the conjunctiva • Most common bacterial cause is Haemophilus influenza • Can be transmitted by improperly disinfected contact lenses

• Bacterial Diseases of the Eye: • Ophthalmia neonatorum • Caused by the transmission of the Neisseria gonorrhea from an infected mother to an infant during its passage through the birth canal • All newborns are treated with an antibiotic to prevent this infection. • Inclusion Conjunctivitis (chlamydial conjunctivitis) • Infection of the conjunctiva caused by Chlamydia trachomatis • Transmitted to infants during birth but tends to resolve spontaneously in a few weeks or months but may lead to scarring of the cornea • Can be transmitted to unchlorinated swimming water; tetracycline as an ophthalmic ointment is an effective treatment • Trachoma • Serious eye infection and probably the greatest single cause of blindness by an infectious disease • Caused by serotypes of Chlamydia Trachomatis • Transmitted largely by hand contact or by sharing such personal objects as towels.

• References: • Engelkirk, P. G. , Engelkirk, J. D. (2015). Burton’s Microbiology for the Health Sciences 10 th Ed. Wolters Kluwer Health, Philadelphia, USA. • Tortora, G. J. , Funke, B. F. (2015). Microbiology: An Introduction. Pearson Publication. ISBN-13: 978 -0321929150. ISBN-10: 0321929152. • Tortora, G. J. , Funke, B. R. , and Case, C. L. (2013) Microbiology: An introduction. 11 th ed. Pearson publishers NY.