Applied Microbiology chapter 24, 25, 29.3

The Skin Microflora

- 1 million per square centimeter - Skin surface is dry • Generally discouraging microbial growth • High microbial activities related to - Sweat gland (apocrine) - Sebaceous gland

Adherence Structures: Capsules

- A pathogen must gain access to host tissues and multiply - Bacteria and viruses that initiate infection by attachment • Often adhere specifically to epithelial cells through macromolecular interactions on the surfaces of the pathogen and the host cell

Large intestine (colon)

- Absorption of bile acids, Vitamin B12 - pH 7 - Absorbs water, vitamins and minerals from gut content

Vector borne transmission

- Avoid area with high insect activity during warm season

Indirect physical contact

- By touching contaminated soil or surface or by sharing objects (cups, dishes, utensils, double dipping) - Pathogens survive longer period time outside of host body - Viral gastroenteritis (stomach flu), fungal infections,MRSA (methicillin-resistant Staphylococcus aureus),dental caries, etc.

Inflammatory Bowel Disease (IBD) - (Disorders Attributed to the Gut Microbiota)

- Chronic inflammation of the gut and disruption of homeostasis (dysbiosis) .- Antibiotic use increases the risk of developing IBD. - Once developed, IBD may be transmissible between family members. - Individuals with IBD have lower gut microbiome diversity.

The human gastrointestinal (GI) tract

- Consists of stomach, small intestine, and large intestine - Responsible for digestion of food, absorption of nutrients, and production of nutrients by the indigenous microbial flora - Contains 10^13 to 10^14 microbial cells (10 trillion - 100 trillion)

Respiratory route transmission

- Cover your mouth with your elbow when sneezing - reduce the disperse of droplets

Currently integrated projects to answer basic questions about the human microbiome

- Do individuals share a core human microbiome? - Is there a correlation between the composition of microbiota colonizing a body site and host genotype? - Do differences in the human microbiome correlate with differences in human health? - Are differences in the relative abundance of specific bacterial populations important to either health or disease?

Compromised Host

- Host with one or more defensive mechanisms are not fully functional - Susceptible to infectious diseases

metabolism and the host's obesity

- Individuals may have mostly Firmicutes, mostly Bacteriodetes, or a mix of the two. - This may regulate ...

Hospital borne transmission (nosocomial diseases)

- Infectious disease transmitted via hospital staff - CDC estimates: 1.7 million cases and 99,000 death per year - MRSA, pneumonia, tuberculosis, urinary tract infection, gastroenteritis, flu, and many more

Vector-borne transmission

- Mainly via insect vector (insect bites); mosquito, sand-fly, tick, lice - Viral encephalitis (including West Nile fever, Dengue fever), Malaria, Rocky Mountain spotted fever, etc.

The Role of the Gut Microbiota in Obesity: Mouse Models

- Normal mice have 40 percent more fat than germ-free mice with the same diet. When germ-free mice were given normal mouse microbiota, they started gaining weight.

Animal borne transmission (Zoonosis)

- Pathogens capable of infecting both human and animals - Rabies, Anthrax, vCJD, Avian flu, Swine flu, Ebola, plague, Salmonella, Shigella, parasitic worms

Direct physical contact (including sexual contact)

- Pathogens survive only short period of time outside ofhost body - By touching an infected person or secretions - AIDS, Genital warts, Gonorrhea, Hepatitis B, Syphilis, Herpes, Leprosy, dental caries, Mono, etc.

Animal borne transmission

- Proper vaccination of your pet - Don't come close to animals acting strange • Pack animal roaming alone • Nocturnal animal roaming daylight

Exotoxins

- Proteins released from the pathogen cell as it grows - Mostly A(active domain) -B(binding domain) toxins - Three categories

Fecal-oral route transmission

- Put the lid back on before flushing toilet - Frequent hand-wash - Proper food preparation and cooking - Avoid swimming in unclorinated water during warm season

Infection

- Situation in which a microbe is established and growing in a host, whether or not the host is harmed - 2 fate of infection • Effectively cleared by host defense system: no disease • Host immune response fail: infectious disease

Endotoxin

- The lipopolysaccharide portion of the cell envelope ofcertain gram-negative Bacteria - Cause damage via hypersensitivity reactions

Virulence

- The quantitative measure of pathogenicity - LD50 (lethal dose, 50%): amount of pathogens required to kill 50% of infected

Fecal-Oral route

- Transmitted indirectly: by consumption ofcontaminated food or water with fecal matter - Mostly pathogens infecting gastrointestinal tract - Cholera, Hepatitis A, Polio, Rotavirus, Salmonella, Shigella, parasitic worms, etc.

Future Benefits of Knowing the Human Microbiome

- development of biomarkers for predicting predisposition to diseases - designing targeted therapies - personalized drug therapies and probiotics

Colonization

- is the growth of microorganisms after they've gained access to host tissues. • The process begins at birth. - Typically starts with mucous membranes, or tightly packed epithelial cells coated in mucus, a thick liquid secretion of glycoproteins

Stomach

- secretion of acid (HCL) - Digestion of macromolecules - pH 2

Fecal transplantation

A medical procedure in which gut microbiota, via fecal matter, are transferred from a donor to a host.

upper respiratory tract

A restricted group of organisms colonizes - E.g., staphylococci, streptococci, diphtheroid bacilli, and gram-negative cocci

Toxicity

Ability of an organism to cause disease by means of a preformed toxin that inhibits host cell function or kills host cells • Toxins can travel to sites within host not inhabited by pathogen

multiply and cause disease.

Altered conditions can cause potential pathogens in the urethra (such as Escherichia coli and Proteus mirabilis) to

dental caries

As dental plaque accumulates, the microbes produce high concentrations of acid that results in decalcification of the tooth enamel

anaerobic bacteria

As plaque continues to develop, ________ _______ species begin to grow

Opportunistic Pathogen

Causes disease only in the absence of normal host resistance

• Environmental factors (e.g., weather) • Host factors (e.g., age, personal hygiene) • Important to maintain microbial population low

Composition of skin microflora is influenced by

Disease

Damage or injury to the host that impairs host function

(dental plaque)

Extensive growth of oral microbes, especially streptococci, results in a thick bacterial layer ___________ followed by calcification

surface layers

Foreign microorganism comes into the host via

birth

Humans are colonized by microbes at

Functions and Products of Intestinal Flora

Intestinal microbes carry out a variety of essential metabolic reactions that produce various compounds • The type and amount produced is influenced by the composition of the intestinal flora and the diet • Compounds produced include - vitamins B12 and K - gas

Firmicutes

Mice that are genetically obese have different microbiota than normal mice. Obese mice have more...

Normal Microbial Flora

Microbes usually found associated with human body tissue

Pathogens

Microbial parasites

benign

Most microbes are - Which means these microbes are not true pathogens - A few contribute directly to human health and even fewer pose direct threats to health

Virulence Factors

Produced by pathogens for their successful colonization - Helps invasion - Helps evasion - Attachment device, enzymes, toxins • Also called disease causing factors

Pathogenicity

The ability of a parasite to inflict damage on the host - Many pathogens use a combination of toxins, invasiveness, and other virulence factors to enhance

colonizing it

The acidity of the stomach and the duodenum of the small intestine (~pH 2) prevents many organisms from

Attenuation

The decrease or loss of virulence

Streptococcus sobrinus and S. mutans

The lactic acid bacteria __________ ________ ___ _ _____ are common agents in dental caries

Firmicutes, Bacteroidetes, and Proteobacteria

The vast majority (~98 percent) of all human gut phylotypes fall into one of three major bacterial phyla:

IBD and other disorders related to dysbiosis

Use of antibiotics during the first few months of life increases the risk of developing

- Animals provide a favorable environment for the growth of many microbes - Each cells are complete package of nutrients

Why infection occurs?

Bacterial adherence

_________ can be facilitated by - Extracellular macromolecules that are not covalently attached to the bacterial cell surface • E.g., slime layer, capsule - Fimbriae and pili

microbiome

a functional collection of different microbes in a particular environmental system (e.g., the human microbiome).

Lactobacillus acidophilus

a resident organism in the vagina, ferments the glycogen, producing lactic acid

Clostridium difficile

a spore-former and generally antibiotic resistant - _________ _____ infections are associated with antibiotic use - A newer therapy for _______ ______ is a fecal transplant

Invasiveness

ability of a pathogen to grow in host tissue at densities that inhibit host function -Can cause damage without producing a toxin

The lower respiratory tract

acks microflora in healthy individuals (sterile)

Age

an important factor for determining susceptibility to infectious diseases - Very young and very old individuals are more susceptible

10^13 (10 - 100 trillion)

approximately __________ microbes in the human microbiome living in complex communities.

Septicemia

bloodborne systemic infection - may lead to massive inflammation, septic shock, and death

Neurotoxins (exotoxin)

botox, tetanus toxin - interfere with neurological signaling

Certain genetic conditions

can compromise a host

Stress

can predispose a healthy individual to disease

Enterotoxins (exotoxin)

cause diarrhea

Bacteria

colonize tooth surfaces by first attaching to acidic glycoproteins deposited there by saliva

teeth

consists of a mineral matrix(enamel) surrounding living tissue (dentin and pulp)

Saliva

contains antimicrobial enzymes - But high concentrations of nutrients near surfaces in the mouth promote localized microbial growth

Methanogen

converts hydrogen to methane

Oral antibiotics

decrease ALL microbes in the human gut (both target and non-target)

Small intestine

duodenum, jejunum, ileum - Continued digestion - absorption of monosaccharides, amino acids, fatty acids, water - pH 4-5

Degradative enzymes

enhance virulence by breaking down or altering host tissue to provide access to nutrients

E. coli and P. mirabilis

frequently cause urinary tract infections in women.

Skin

generally a dry, acid environment that does not readily support the growth of most microbes

Cytolytic toxins (exotoxin)

hemolysin is an example - work by degrading cytoplasmic membrane integrity, causing cell lysis and death

The microbial populations

in the distinct anatomical areas of the GI tract are influenced by diet and the physical conditions in each section

Mucus membrane

infections frequently begin at sites in the animal's mucous membranes

H2

inhibits fermentation

The Oral cavity

is a complex, heterogeneous microbial habitat

vagina of the adult female

is weakly acidic and contains significant amounts of glycogen

Lactic acid

maintains a local acidic environment

microbiota

o describe all the microbes in a microhabitat (e.g., skin microbiota)

Diet

plays a role in host susceptibility to infection

Evasive enzyme

protect the pathogen by interfering with normal host defense mechanisms • E.g., coagulase

Highly virulent pathogens

show little difference in the number of cells required to kill 100% of the population as compared to 50% of population

Upper respiratory tract system

sinuses, nasopharynx, pharynx, oral cavity, larynx

All

sites on a human that contain microorganisms are part of a microbiome.

Different microhabitats

support different microbes, so the skin will have very different microbes than the mouth.

vulnerable spots of skin

sweat glands and surrounding area are readily colonized by gram-positive bacteria and other normal flora of the skin

Adherence

the enhanced ability of microbesto attach to host tissues. It is necessary, but not sufficient, to start disease.

Bacteremia

the presence of bacteria in the bloodstream

lower respiratory tract system

trachea, bronchi, lungs

The bladder

typically sterile in both males and females

VFAs

volatile fatty acids (short chain fatty acids)

Respiratory route (airborne diseases)

• Inhalation of aerosolized droplets • bacterial meningitis, chickenpox, common cold, influenza, Mumps, strep throat, Tuberculosis, Measles, Rubella, Whooping cough

Physical barriers (Host resistance to Infection)

• Protective epithelial layers • Body temperature (constant at around 37oC)

Chemical barriers (Host resistance to Infection)

• Skin acidity • Stomach acidity • Rapid pH change through GI tract

Natural host resistance (Host resistance to Infection)

• Tissue specificity • Immune system • Normal flora