Chapter 5/Microbiology Joe Pistack MS/ED

Disease Disease-failure of the body to function normally. A leading cause of disease in humans is invasion of the body by pathogens. Pathogen-disease-producing microorganism. Disease

Infection-invasion of the body by a pathogen and the symptoms that develop in response to this invasion. Localized infection-restricted to a small area of the body. Systemic infection-widespread infection throughout the body, usually spread by the blood. Infection

Microorganisms (Microbes) Bacteria-single-cell organisms found everywhere. Normal flora-organisms that normally and harmoniously live in or on the human body without causing disease. Prevents the overgrowth of other organisms, keeps them under control. Microorganisms (Microbes)

Bacteria Bacteria make up the largest group of pathogens. Successful invasion of pathogens can cause damage in two ways: (1)-entering and growing in the human cell. (2)-secreting toxins that damage the cells. Bacteria

Classification of Bacteria Bacteria are classified into three groups based on shape: (1)coccus (round) (2)bacillus (rod-shaped) (3)curved rod Rickettsiae and chlamydiae are also classified as bacteria, although they differ in several ways from cocci, bacilli, and curved rods. Classification of Bacteria

Cocci Cocci-round cells arranged in patterns. Diplococci-cocci arranged in pairs. Staphylococci-look like bunches of grapes and are arranged in clusters. Cocci- responsible for many diseases such as gonorrhea, meningitis and pneumonia. Cocci

Bacilli Bacilli-long and slender and shaped like a cigar. Diseases caused by bacilli include tetanus, diphtheria, and tuberculosis. Bacilli

Curved Rods Curved rods- include: vibrio spirillum spirochete Cholera is caused by the vibrio. Tightly coiled spirilla are called spirochetes and are the cause of syphilis. Curved Rods

Many bacteria form spores, they allow the bacteria to survive in a dormant state during extreme conditions or when exposed to disinfectants. When the conditions improve, the spores will wake from their dormant state and resume activity. Ex. Clostridium botulinum, causes a deadly form of food poisoning. The spores that cause this disease can withstand several hours of boiling water. Bacteria

Rickettsia and chlamydia are classified as bacteria, they are smaller than most bacteria and must reproduce within the living cells of a host. Called parasites, because they require a living host. Rickettsia are often carried by fleas, ticks and body lice. Bacteria

Chlamydiae are smaller than rickettsiae and cause several diseases. Chlamydia trachomatis is responsible for one of the most prevalent sexually transmitted diseases in the US today. Chlemydial infection is also responsible for trachoma, a serious eye infection that is the leading cause of blindness in the world. Bacteria

Viruses Virus-smallest infectious agent. Viruses are parasites, they can only reproduce within the living cells of a host. Ex. of viral diseases, measles, mumps, influenza, poliomyelitis and AIDS. Most upper respiratory infections are viral and are not responsive to antibiotics. Viruses

Virus

Fungus Fungus-plantlike organism, grows best in dark, damp, places. Mycotic infections-pathogenic fungal infections. Usually localized. Ex. of fungal infections include athlete’s foot, ringworm, thrush, and vaginitis. Fungus

Athlete’s Foot Fungal infection that causes redness, itching, burning. Mildly contageous. Passed by direct contact such as walking in locker rooms or around pools. Rx. Topical antifungal lotion. Athlete’s Foot

Ringworm Skin infection caused by a fungus. The fungus grows outwards from the center. Skin becomes itchy, red, raised scales that may blister and ooze. Rx. Antifungal lotions or pills. Ringworm

Protozoa Protozoa-single-cell, animal-like microbes. Found in soil and most bodies of water. The parasites are ingested in contaminated water and food and cause diarrhea. Protozoa

Helminths-multicellular animals that are parasitic and pathogenic to humans. Microscopic examination of body samples is required to identify the worm. The worms are classified as round-worms and flat-worms. Parasitic Worms

Pinworm is a type of roundworm that is common in children. The pinworm lives in the intestinal tract but deposits their eggs on the outer perianal area. The deposition of the eggs causes itching, (pruritis). Parasitic Worms

The child may scratch the anal area and transfer the eggs to the mouth. The eggs are swallowed and newly hatched pinworms grow into adulthood in the intestine. This transfer of eggs is called the fecal- oral route. Parasitic Worms

Pinworms

Flatworms Tapeworm-form of flatworm. Acquired by eating poorly cooked contaminated food such as beef, fish, or pork. Tapeworms that live in the intestines may grow from 5ft. To 50ft. In length. Flatworms

Tapeworms Tapeworms attach to the intestines of the host. Once anchored to the intestinal wall the tapeworm absorbs nutrients through it’s skin. Symptoms include increased appetite, insomnia irritability. Rx. Medications. Tapeworms

Ectoparasites-arthropods with jointed legs and include insects and ticks. They live on the skin and mucous membrane. Cause itching and discomfort. Ex. lice, insects and ticks. Ectoparasites

Mosquitoes, biting flies, fleas, and ticks act as vectors of disease. Vector-object, living or non-living, that transfers a pathogen from one organism to another. The bite of the vector introduces pathogens into the host causing infection. Ectoparasites

Mosquito can carry the pathogens for malaria and encephalitis. The tick can carry the pathogen that causes Lyme disease and Rocky Mountain Spotted Fever. Ectoparasites

Laboratory Identification Methods of identifying pathogens: (1) Gram stain (2) Culture Gram stain-bacteria are classified according to staining characteristics. A dye is used to gram-stain the bacteria, gram-positive bacteria will stain purple or blue. Ex. streptococcus Laboratory Identification

Laboratory Identification Gram-negative-bacteria will not absorb the dye, it will pick up a pink or red stain. Ex. Escherichia coli Bacteria is either gram-positive or gram- negative, gram staining may be an important step in identification of organisms. Laboratory Identification

Laboratory Identification Acid-fast stain-the bacteria is first stained with a red dye and then washed with an acid. Many bacteria lose the red stain when washed with acid, but several others retain the red stain and are therefore called acid-fast. Ex. Mycobacterium tuberculosis (TB). Laboratory Identification

Gram stain

Laboratory Identification Culture-growth of pathogens in a culture medium. Ex. Wound drainage Culture and sensitivity-when the pathogen is cultured for susceptibility to various antibiotics. Antibiotic is placed in the same culture and stops the growth of the pathogen, it is assumed to be sensitive to the antibiotic. Laboratory Identification

Culture and Sensitivity

Modes of Transmission

Portal of Entry Portal of Entry- how pathogens enter the body. Portals of entry include: Respiratory tract GI tract GU tract Eyes Skin Portal of Entry

Portals of Entry Parenteral route- includes injuries that penetrate the skin or mucous membranes such as bites, cuts, or surgery. Break in the skin is an excellent way for pathogens to enter the body. Portals of Entry

Portals of Exit-the way that pathogens leave an infected body. Portals of exit include: Respiratory tract GI tract GU tract Eyes(tears) Breasts (milk) Portals of Exit

Most common exits are the respiratory and gastrointestinal tracts. Ex. Cold virus is sneezed or coughed into room air from the passages of the infected person. Salmonella is excreted in stool. Portals of Exit

By knowing the portal of exit we can set up procedures or take precautions to prevent the spread of disease. Preventing Infection

Preventing Infection Pathogens are spread : Person to person Environment to person Insects to person Most important procedure in the prevention the spread of disease is Handwashing! Preventing Infection

Person-to-Person Contact An infected person can spread germs by coughing or sneezing. When a person sneezes, the cold virus is sprayed into the room in droplets. The droplets are inhaled by co-workers. The virus is spread by droplet contact. Person-to-Person Contact

Person-to Person Contact A person with contaminated hands touches other objects in the office, ex. doorknobs, desktops, handshaking. Vector-an object, living or non-living, that transfers a pathogen from one organism to another. Fomite-nonliving vector. Person-to Person Contact

Person-to-Person Contact

Environment-to-Person Contact This mode includes contact with contaminated water, air, food, or soil. Ex. You can develop food poisoning if you eat food contaminated with E-coli. Environment-to-Person Contact

Animal-to-Person Contact Insects act as vectors to transmit disease. Ex. A mosquito bites a person with malaria, the malaria germ matures in the stomach of the insect. The insect then bites another person. Animal-to-Person Contact

Nosocomial Infections A hospital acquired infection- formerly known as nosocomial infection Most often transmitted from person to person by direct contact. Most frequently spread by professionals who Do Not Wash Their Hands! Nosocomial Infections

Prevent the Spread of Infection