Gram Negative Bacteria

O antigen

Carbohydrate portion of an LPS that our immune system recognizes

Lipid A

Endotoxin that is released into the blood stream and causes fever, vasodilation, inflammation, shock, and disseminated intravascular coagulation in a gram negative bacteria

Disseminated Intravascular Coagulation (DIC)

Blood clotting in our blood vessels that causes damage to those with a small diameter. Blood clotting factors are used up in this process, meaning there are less blood clotting factors available in our body, disrupting normal blood clotting

Neisseria

The only gram negative group that almost always cause diseases. Has Polysaccharide capsule, fimbriae, and lipid A. They are diplococci that also contain oxidase

Neisseria gonorrhoeae

Causes gonorrhea and occurs the most in adolescents. Cases, have declined over the past decades and women are more likely to contract this during sexual encounters. Can survive in leukocytes and use it to move to other tissues of the body

Fimbriae and Capsule

Found in Neisseria gonorrhoeae that attaches to the mucus membranes of urogenital and digestive tracts

Protease

An enzyme found in Neisseria gonorrhoeae that destroys the IgA antibody which means it destroys the antibody in our mucus membranes

Gonorrhea in Men

Rapid inflammation causes painful urination and pus filled discharge. Can make its way up into the prostate or epididymis and cause tissue damage or male infertility

Gonorrhea in women

Very often it is asymptomatic, when symptoms are present it resembles a UTI or vaginal yeast infection. Can also trigger Pelvic Inflammatory Disease, Proctitis, Pharyngitis, Gingivitis, Endocarditis, or join inflammation.

If pregnant, can transmit this to the baby during birth by infection of the conjuctiva or respiratory tract

Pelvic Inflammatory Disease

Inflammation of the Uterus

Proctitis

Inflammation of the rectum

Pharyngitis

Inflammation of the pharynx

Gingivitis

Inflammation of the gums

Diagnosis of Neisseria gonorrhoeae

Gram negative diplococci in pus samples from an inflamed penis. Asymptomatic causes (women mostly) identified by testing kits with genetic probes (like the strep throat kit)

Treatment of Neisseria gonorrhoeae

Resistant to most common antibiotics such as penicillin and tetracycline. Cephalosporin is delivered intramuscularly. There is no long term immunity to this pathogen because of many strains

Neisseria meningitidis

Similar to Neisseria gonorrhoeae in that is survives phagocytosis inside the leukocyte. Can be part of normal microbiota in the upper respiratory tract, they are an opportunistic pathogen. Transmitted primarily by respiratory droplets

Blebbing

Shedding of the outer membrane and releasing Lipid A. This is found in Neisseria meningitidis

Meningitis

Acute swelling of the protective membranes that cover the brain and spinal cord. Can cause death within 6 hours of symptoms

Meningococcal meningitis

Associated with Neisseria meningitidis and features fever, stiff neck, sore throat, and vomiting

Meningococcal Septicemia

Associated with Neisseria meningitidis and occus when lipid A is released into the blood causing organ damage and petechiae

Petechiae

Can be a sign of a Neisseria meningitidis infection. Features a red lesion in the skin, many cells can die in a region causing large black lesions

Diagnosis of Neisseria meningitidis

Diagnosed by presence of gram negative diplococci in cerebrospinal fluid, can be detected in a media culture as they oxidase maltose

Treatment of Neisseria meningitidis

100% fatal if left untreated. Uses semisynthetic cephalosporin like ceftriaxone or cefotaxime

Entero

Means GI or gastrointestinal

Enterobacteriaceae

Intestinal residential microbiota, opportunistic pathogens. Found in water, soil, and rotting vegetables. Are all bacillus or coccobacillus and do not have the oxidase enzyme but can ferment glucose. Some members are motile and contain peritrichous flagella

Hemolysins

Toxin of Enterobacteriaceae that destroys red blood cells

Siderophores

Molecule released by Enterobacteriaceae that sequesters free iron effectively and takes in all the iron in your blood immediately

Pathogenicity of Enterobacteriaceae

Have hemolysis, fimbriae with adhesion proteins, capsules, siderophores, enzymes that break down antibiotics, and lipid A

Eosin Methylene Blue

Selective for gram negative by having dyes and differential by the presence of lactose. Fermentation causes metallic green dyes to precipitate in colonies

MacConkey Media

Selective for gram negative by having bile salts and crystal violet and differential by the presence of lactose. pH indicator is neutral red and fermentation causes color change to wine pink

Coliform

A classification of Enterobacteriaceae that ferments lactose and is an opportunistic pathogen that is part of our residential microbiota

Non-Coliform

A classification of Enterobacteriaceae that does not ferment lactose and is an opportunistic pathogen that is part of our residential microbiota

E. coli

A coliform that has antigens O, H, and K, that are used to identify particular strains. Virulent strains have virulence plasmids with genes for fimbriae, adhesins, and enterotoxins

Gastroenteritis

Most common disease caused by E. coli and features diarrhea, cramps, nausea, and vomiting. Symptoms are usually caused by enterotoxins

E. coli Strain O157:H1

Causes severe GI and urinary tract infections. Produces a shiga like toxin that inhibits protein synthesis. Causes the disease Hemorrhagic colitis

Hemorrhagic colitis

Severe intestinal infection characterized by bloody diarrhea. Secretion system III proteins that bind to our cells, allowing them to attach and outcompete other bacteria in the region

Klebsiella

A coliform that normally infects the respiratory and GI tracts and is non motile. Has a well defined capsule that is extremely effective in evading phagocytosis

K. Pneumoniae

Strain of Klebsiella that is the most common pathogenic species of this genus. Causes pneumonia which is the destruction of the alveoli and overproduction of mucus/fluid

Serratia

A coliform that has a red/salmon pigment. Grows in catheters, saline solution, and other medical supplies

S. marcescens

Most common and medically relevant species of Serratia. Can cause life-threatening opportunistic respiratory and urinary infections in immunocompromised patients. It is frequently resistant to antimicrobial drugs from the presence of efflux pumps

Proteus

A non-coliform that can switch from being rod shaped with a few flagella to an elongated, peritrichous form. Can use the urease enzyme that breaks down urea into ammonia and carbon dioxide. The increased pH of urine causes ions to come out of solution and harden around bacteria cells, leading to kidney stone formation. May are resistant to antibiotics

Peritrichous

Swarming cell produces a concentric, wave like pattern when grown on agar plates

Proteus mirabilis

The most common species of proteus to cause urinary infections, seen from long term catheter use in health care facilities

Type III Secretion proteins

Inhibit phagocytosis, apoptosis, rearrange/disrupt the cytoskeleton

Salmonella

A truly pathogenic Enterobacteriaceae that is a motile, peritrichous bacilli. Lives in the intestines of birds, reptiles, and mammals. Most human infections due to consuming food contaminated with animal feces. Poultry and eggs are common sources of this.

Salmonellosis

Transmitted by food contaminated by animal waste. Occurs when salmonella infects our GI tract causing diarrhea, nausea, and vomiting. Uses type III Secretion systems to induce epithelial cells of the small intestine to engulf or endocytize them. Once inside epithelial cells, they rapidly multiply in the vesicle eventually rupturing and killing the epithelial cell. Symptoms are caused by death and loss of epithelial cells, once the bacterial cells are released into blood vessels bacteremia starts. Can infect the lining of the heart and joints when it becomes systemic

Treated with fluids/electrolytes

Typhoid Fever

Transmitted by food/water contaminated by human waste. After infecting intestinal cells, they are released into the blood stream where phagocytes engulf them but are unable to destroy the bacterial cells. Phagocytes transport them through the blood to the spleen and gallbladder

Symptoms consist of fever, muscle pain, and fatigue that gradually increases over time

Treated with antimicrobial drugs, vaccines provide temporary protection to travelers

Salmonella enterica

Bacteria that causes typhoid fever, can be carried by humans in the gall bladder. If carried in the gallbladder, it may be removed

FDA food regulations

What has typhoid fever cases decreased?

Factory farming

What has salmonellosis increased?

Bacteriophages

These are added to food products in Europe to kill salmonella but not yet approved to treat food products in the USA