1. NURS 218 MICROBIOLOGY IN NURSING
Control and Treatment
Microbial Infections

2. 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.

3. Outline Control of Microbial Growth Microbial Infections
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

4. 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

5. 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.

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

7. Actions of Microbial Control Agents
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.

8. 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.

9. 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.

10. Filtration Low Temperature
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

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

12. Osmotic Pressure Radiation
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

13. 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. pHisoHex ( used for surgical and hospital microbial control procedures; triclosan ( an ingredient in antibacterial soaps
Biguanides – damage plasma membranes of vegetative cells

14. 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

15. 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.

16. 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.

17. 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 gram- negative bacteria acts as a pump that expel antibiotics that prevent them from reaching an effective concentration

18. 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.

19. II. Microbial Infections

20. 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

21. 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

22. 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

23. 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

24. 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

25. Rubella (German Measles)
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.

26. Tinea unguium – ringworm of the fingernails or toenails
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

27. 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

28. 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

29. 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.

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