Normal Flora

Transient flora

Inhabit for a relatively short period of time

Anatomical distribution of normal flora

Determined by tissue specificity and will bind between host receptor and microorganisms ligand

What determines if normal flora resides

substrate availability, inhibitory factors, competition with other flora, and environmental condition

General characteristics of normal flora

Relatively stable in a complex ecosystem, dynamic interactions, and homeostasis is key for maintaining a good relationship with the host

Host-specific factors that contribute to NF

Nutrition, stress, gender, lifestyle, health, and age

Sterile anatomic sites that can be infected by NF

Blood/circulatory system, spinal fluid, synovial fluid, lower respiratory tract, uterus, and other internal organs

Effects of lactobacilli

Produces lactic acid and propionic acid to maintain a low pH

Normal flora stimulation of adaptive immune system

Induction of cross-reacting antibodies and isohemagluttinins

How NF prevents colonization of pathogens

Occupies receptor sites, competes for limited nutrients, and produces substances that inhibit or kill pathogens

Nosocomial infections

Infection that comes from hospital

• Shift from gram + → gram - in oropharynx

• Medications that slow peristalsis will increase gut flora leading to sepsis

• Immobility leads to stomach hypoacidity

• catheterization in urinary tract and intubation

Effects of antibiotic usage

Overgrowth of candida (infection of mouth and vagina) and Clostridioides difficile

Benefits of probiotics

GI problems (IBS/IBD), prevents side effects of antibiotic, helps cold and flu symptoms, helps colic babies, and eczema

Most common mixture of probiotics

Lactobacillus and Bifidobacterium

Problem group for probiotics

People with immunodeficiency

Concept of disease

Microbe causes disease when equilibrium is not achieved for when accidentally colonizing human

Frank pathogen

Always causes infection or disease when the appropriate host is exposed in the proper contest

Opportunistic pathogen

Only causes disease in a compromised host (ex NF and non-pathogens)

Pathogenesis

The evolution of a disease within a host, aka the house of infection

Virulence factors

Genetics, biochemical, or structural features that enable it to produce disease

Inapparent carriage vs convalescent carriage

Inapparent carriage: the individual doesn’t know they are carrying the disease but are still contagious → they NEVER had symptoms of the infection

Convalescent carriage: they have recovered from the infection but are still contagious

Infection definition

Further step of colonize and has the potential to result in disease but does not always directly translate into a disease state, it may or may not be apparent to the hose (asymptomatic)

Types of infections

Inapparent (asymptomatic)

Dormant: exists but not active (mono)

Pyogenic: pus producing

Location → localized or systemic

Primary infection

Clinically apparent invasion, causing local tissue injury

Seconday infection

Invasion subsequent to primary infection

Superinfection

Infection of top, as a result of or in addition to the primary one

Co-infection

2 infections that appear together, often interdependent but are always simultaneous (tuberculosis and HIV)

Mixed infection

2 or more microbes infecting the same tissue

Disease definition

Specific set of manifeston of damage due to host-pathogen interaction

Incubation period of disease

Time interval between initial infection and first appearance of signs and symptoms

Period of decline in disease

Signs and symptoms subside

Period of illness in disease

Disease is at its height and all disease signs and symptoms are apparent, death may occur at this time

Period of convalescence of disease

The body returns to its prediseased state and health is restored

Acute disease

Rapid, brief disease (hours/days)

Subacute disease

Between acute and chronic (days/weeks)

Chronic disease

Slow progress and prolonged duration (months and years)

Factors that affect virulence and pathogenic mechanism

Portal of entry, rose, adherence, rate of growth, avoidance of phagocytosis, or endotoxin vs exotoxin

Endotoxin

LPS so produced by gram negative only → pyrogenic, heat stable and no toxoid

Binds host CD14 and activates alternative complement pathway

Exotoxin

Polypeptide/proteins so produced by both gram neg and gram pos

Not pyrogenic, usually heat labile, and toxoids often possible

Sterilization

The absolute killing or removal of all microorganisms, including all bacterial spores on inanimate objects. But it does NOT destroy all microbial products.

-Cidal

Irreversible killer or killing

-Static

Growth is halted, when the agent is removed microorganisms can grow. The absence of growth does not mean it’s sterile!

Disinfectant

The killing of many but not all microorganisms. For adequate disinfectant, all vegetative pathogens must be killed and should only be used on inanimate objects.

High level disinfectant

Effective against most or all pathogens but not large number of spores

Intermediate level of disinfectant

Effective against mycobacteria and other negative bacteria, most viruses and fungi but not bacterial or fungal spores

Low level disinfectant

Most vegatative bacteria, enveloped viruses, and some fungi, but not mycobacteria or spores

Santitization

Clean and no pathogens, but not complete disinfectant and does not imply sterilization

Pasterurization

The use of heat at a temperature sufficient to kill important pathogens in liquids but at a temperature below that needed for absolute sterilization that might affect quality of the food or substance → not sterile, it is a disinfectant or preservation

Antispetic

Chemcials sued to kill microorganisms on the surface of skin and mucous membrane

Asepesis and aseptic technique

refers to techniques that prevent entry of living microorganisms/infectious agent into human, sterile solutions, cultures of mammalian cells

Decontamination

Procedure involving the destruction of removal of contaminants

Degree of killing microorganisms

Sterilization > disinfection > pasteurization > antiseptic = sanitization

Why is controlling the number of microorganisms critical

Infectious disease and contamination is determined by the number of microorganisms present and increased numbers dictate a more vigorous method

What is the most to least difficult microorganisms to kill

Bacterial spores, Protozoal oocysts, mycobacteria, non-enveloped viruses, and gram negative bacteria

Ideal application time for killing microorganisms

More application time is better

Ideal number of organisms for killing microorganisms

Fewer microorganisms is better

Concentration of the agent for killing microorganisms

If the concentration of the agent is increased, it will take less time to kill (alcohol is the only exception)

Ideal temperature for killing microorganisms

for every 10 degree C increase, the chemical activity doubles and killing time decreases

Critical item medical device

Must be sterilized because they ensure tissue or blood stream

Semi-critical item medical device

come into contact with broken skin, mucous membrane and require treatment with disinfectant that have high level of activity

Non-critical medical device

cleaned and treated with low-level disinfectants because they only come into contact with skin

Example of critical item medical device

Surgical instrument, urinary catheters, IV fluids

Example of semi-critical medical device

endoscope, reusable thermometer

Example of non-critical medical device

Bedrails and blood pressure cuffs