4.2 slides - gram negatives

Vocabulary flashcards covering key Gram-negative pathogens, structures, and concepts from the lecture.

Endotoxin (Lipid A)

Toxic portion of Gram-negative LPS that overstimulates macrophages, causing fever, shock, and possible DIC. - majority of gram negatives have this - toxin - can cause super antigen effects, exaggerated inflammatory response - also causes an overstimulation of macrophages with production of various cytokines

All gram negatives have a…

virulence factor (endotoxin), therefore are dangerous

gram - spirals

treponema

borrelia

leptospira

gram - cocci

neisseria

gram - rod, curve

vibrio

campylobacter

helicobacter

gram - rod, straight, aerobic

pseudomonas

gram - rod, straight, facultative

enteric (many) (GI tract organisms)

gram - rod, straight, anaerobic

bacteroides

gram - rod, straight, other, respiratory

bordetella

haemophilus

legionella

gram - rod, straight, other, zoonoses (diseases you can catch from animals)

yersinia

pasteurella

brucella

francisella

streptobacillus

gram - rod, straight, other, GU

H. Ducreyi

gram - : Neisseria, cocci

Pathogenic, two types:

N. meningitidis

N. gonorrhoeae

Both are delicate and fastidious, coffee bean shaped in pairs, pyogenic

Neisseria meningitidis

Capsulated Gram-negative diplococcus; droplet-borne cause of meningitis, especially in close-living groups. well known cause of bacterial meningitis

- Capsule protects cells during phagocytosis

- Present as normal microbiota in 40% of population - throat area

- Transmitted by droplets, close contact - Infection of meninges, sore throat, high fever, headache, stiff neck, vomiting, convulsions; rapid course.

- Epidemiology: people living in close contact; military recruits

currently vaccinated; also many college students.

Neisseria gonorrhoeae

Gram-negative diplococcus STI; uses capsule, fimbriae, and neutrophilfimbriael; no long-term immunity. cause of gonorrhea, STI

- Virulence factors: capsule, fimbriae, survival in neutrophils

- Males: painful purluent discharge from urethra - Females: often asymptomatic; otherwise, urethritis, PID,

infections anywhere sexual contact occurs, arthritis.

- Eye infection of newborns

- No long term immunity!!

Enterobacteriaceae - gram neagtive rods

Large family of facultative Gram-negative rods in soil, water, GI tracts; includes coliforms and non-coliforms. - Facultatively anaerobic; found in soil, water, and GI tracts some strictly pathogens, others opportunists

• Generally divided into:

• Coliforms (ferment lactose)

• Non-coliforms

Virulence factors - Endotoxin, capsules, fibriae, exotoxins, others.

Enteric bacteria identified by biochemical tests

-Selective/differential media, etc.

-Strains identified by serological techniques •

• Use of antibodies to identify particular antigenic molecules on cell surfaces

• O antigen: repeating sugar group on LPS

• H antigen: flagellar protein

• K antigen: capsule antigen around cell.

• Example: E. coli 0157:H7 describes particular serotype which happens to also produce a dangerous exotoxin (Shiga toxin-inhibits protein synthesis).

E. coli - hey i thought e. coli was a “good guy”

• Most strains common to Gl tract, not harmful there... however, it is:

• One of the most common causes of diarrhea

• The most common cause of urinary tract infections!! (not in the proper place!!)

Many strains possess plasmids that code for additional virulence factors (le, Shiga toxin) which cause disease

• E. coli O157:H7: common in cows, deer, swine. In humans will cause hemolytic uremia syndrome, destroys bowel, damages kidneys.

O Antigen

Repeating sugar portion of LPS used in serotyping Enterobacteriaceae.

H Antigen

Flagellar protein antigen of motile enteric bacteria.

K Antigen

Capsular polysaccharide antigen surrounding some enteric bacteria.

Escherichia coli O157:H7

Shiga-toxin–producing cattle-associated strain causing hemorrhagic colitis and hemolytic uremic syndrome.

Klebsiella pneumoniae - oppurtunistic enteric (straight rods) - facultative

Opportunistic capsulated rod causing pneumonia and wound infections; common in hospitals.- various opportunistic infections including wound infections, pneumonia

- Capsule is major virulence factor

(Found normally in the mouth, skin, and intestines, Fecal contamination a problem, especially in hospital patients. Some resistance to ABX - antibiotics)

Proteus species - oppurtunistic enterics - straight rods

Highly motile urease-producing rods causing UTIs and kidney stone formation. - changes shape and flagella between liquid and solid media; common cause of urinary tract infections

- Produces urease

(Found in soil, feces. Can be treated with ABX- antibiotics)

Enterobacter aerogenes - oppurtunistic enterics - straight rods

Coliform found in GI tract and environment; causes wound and nosocomial infections. - Coliform; Gl tract and

environmental - wound infection

Salmonella enterica - pathogenic enterics - straight rods

Poultry- and reptile-associated pathogen causing food-borne gastroenteritis after high-dose ingestion.- species so closely related that they are really all S. enterica. But medically, species epithets still used: S. typhi and others. Divided serologically.

- Present on eggs, poultry, on animals such as reptiles

- Large dose results in food poisoning; diarrhea, fever, etc.

- Cells phagocytized by intestinal lining cells, kill cells causing symptoms, may pass through into blood.

(• Reservoir is humans. • ABX useful. • Surgery to remove gall bladder. • Vaccine developed.)

Salmonella typhi - pathogenic enterics - straight rods

Human-only serovar causing typhoid fever; gall bladder reservoir; vaccine available. - typhoid fever. Spread

through body

• Gall bladder as reservoir; Typhoid Mary

• Importance of clean water and sewage treatment.

Shigella sonnei - pathogenic enterics - straight rods

Most common Shigella species in U.S.; low infectious dose diarrheal pathogen spread by the 5 F’s. - especially S. sonnei (most common) and S. dysenteriae (most serious); cause shigellosis.

- Food, flies, fingers, feces, fomites: very small infectious dose, personal hygiene important in prevention.

- Infection of intestinal lining damaged, cells pass directly from cell to cell; cramps, diarrhea, bloody stools.

- S. dysenteriae (destruction of the intestinal lining, blood losses) produces shiga toxin which inhibits protein synthesis, increases damage.

- Most serious problem with diarrheal diseases in general is dehydration

Shigella dysenteriae

Most severe Shigella; produces Shiga toxin leading to bloody dysentery. - most serious problem with diarrheal diseases in general is dehydration

Shiga Toxin

AB exotoxin that halts protein synthesis, produced by S. dysenteriae and some E. coli.

Yersinia pestis - pathogenic enterics - straight rods - zoonotic

Plague agent; flea-borne zoonosis producing buboes, septicemia, or pneumonic disease. sp: Y. pestis is cause of plague, other species cause food-borne infections - the medieval plague !!!!!!

• Plague: 3 cycles: spread - sylvan (woods from animals), urban (cities), and human (human to human, pneumonic - coughed up)

- endemic in sylvan cycle; mixing of woodland and urban rodents brings urban cycle, fleas jump from dying

rats to humans.

- Infection leads to large swollen lymph nodes: buboes

• Bubonic plague, with high fever.

• Septicemic plague: with DIC, bruising (The "black death")

• Raises mortality from 75% to near 100%

• Pneumonic: coughed out and spread human to human

• 100% mortality

Pasteurella multocida- small gram negatives - zoonotic

Fastidious rod from animal mouths; causes cellulitis and lymphadenitis after bites. - Common in animals; significant disease present in commercial and domestic poultry flocks, people get it via bites, scratches - chicken scratches common!!

- Inflammation, swollen nodes near site if infection - localized infections

Streptobacillus moniliformis - gram (-) pleomorphic, filamentous rod - streptobacillus - zoonotic

Filamentous rod causing rat-bite fever with rash, arthritis, and possible fatality. - is the usual cause

of rat-bite fever. - carried in saliva of rats!!

• Incidence is highest in urban areas with poor sanitation. Also, occupational contact with rodents such as pet shop employees or laboratory workers or through pet ownership.

• The disease typically presents with chills and fever accompanied by headache, vomiting, and muscle pain. A rash and arthritis develop 2-4 days after the initial onset.

• Can also cause pneumonitis, endocarditis or meningitis.

• Often misdiagnosed and classified as a fever of unknown origin (FUO).

• If untreated, death will occur in approximately 10% of cases.

(ABX effective. Also, Haverhill Fever where the rats get into the food.)

Brucella species - gram negative coccobacilli - very short rods - zoonotic

Intracellular coccobacilli from livestock; produce undulant fever and foul-smelling sweat. - different species for each animal

- Infection from contact with livestock, fluids, incl dairy

- Undulant fever: fever that goes up and down

A zoonosis transmitted by ingesting contaminated food (such as unpasteurized milk products), direct contact with an infected animal, or inhalation of aerosols.

• Foul-smelling perspiration is considered a classical sign. Up to 60% of cases have joint complications.

• First, the bacterium does not bear classic virulence factors, such as capsules, secreted proteases, exotoxins, endotoxins, pili and/or fimbriae or virulence plasmids, and its lipopolysaccharide pathogenicity is not typical.

• Second, it exhibits a tendency to invade and persist in the human host through inhibition of programmed cell death

Bordetella pertussis - very short rods - zoonotic - respiratory

Coccobacillus of whooping cough; pertussis toxin disables phagocytes; prevented by DTaP vaccine.

B. pertussis, cause of whooping cough - Infects trachea, several

toxins.

- Disease in stages: incubation, catarrhal, paroxysmal

• Coughing and inhalation: whoop

- DPT (but also new acellular vaccine)

• Bordatella also has capsule, fimbria.

• Pertussis toxin affects cell signaling, and turns off phagocytes.

• Also in primates.

• ABX effective.

Haemophilus influenzae and H. ducreyi - haemophilus - influ(respir) decreyi(GU)

Capsulated coccobacillus causing pediatric meningitis, epiglottitis; controlled by Hib vaccine.

- H. influenzae: mostly respiratory infections, otitis (ear), meningitis, and epiglottitis (more prominent in kids) (doesnt cause the flu!!!)

- Capsule is major virulence factor; Hib vaccine protects

- H. ducreyi: STI, chancroid; visible and painful in men

Haemophilus ducreyi

Sexually transmitted coccobacillus causing painful chancroid ulcers.

Pseudomonas aeruginosa - pseudomonas - gram negative aerobic rod

Green-pigmented, disinfectant-resistant aerobe; major threat to burn and cystic fibrosis patients.

• Very common in environment, soil - free living

• Paeruginosa the most dangerous; opportunist

- Endotoxin, exotoxins, fimbriae, enzymes, capsule

- Capable of causing disease anywhere in body

- Two major problems: burn patients (so many open wounds, oppurtunists) and cystic fibrosis

• Cause of swimmer's ear (can also be fungal), hot tub infections, etc.

- Resistant to most disinfectants and antibiotics

Francisella tularensis - other gram negative rods, zoonotic, francisella

Intracellular rod of tularemia; zoonotic via ticks, rabbits, inhalation; causes fever and lymphadenopathy. - cause of tularemia

- Also called rabbit fever, tick fever, deerfly fever, etc.

- Most cases in SE USA

- Survives phagocytosis, lives intracellularly

- Present in many animals, transferred to humans by vector, ingestion, direct contact, inhalation

- Chills, fever, malaise, swollen nodes

Legionella pneumophila - other gram negative pleomorphic rods - legionella - respiratory

Aquatic intracellular rod growing in amoebae; causes Legionnaires’ disease pneumonia. - creates a lung infection!!

• Fastidious in culture, requires special media

• Very common in aquatic environments: (lives inside amoeba) - ponds, cooling towers, hot-water heaters, showers.

• Grows normally in amoebae, so also grows in phagocytes

• Most dangerous as opportunistic pneumonia, inhalation

• Mild form of disease: “Pontiac fever” - pontiac michigan

(have flagella and pili)

Bacteroides species - anaerobic gram negative rods

Dominant anaerobic rods of human gut; cause abscesses after trauma or surgery.

• Many different anaerobic bacteria live in parts of body, esp. GI tract (>99% anaerobes) but also in mouth, genito-urinary tract.

• Trauma to these areas leads to polymicrobic infections.

• In GI tract, a common bacterium is Bacteroides

• Opportunist, causes abscesses in GI, reproductive, wound infections

Leptospira species - gram negative spirochetes - spiral - produces hemolysins

Spirochetes in animal urine; biphasic disease ranging from flu-like illness to liver and kidney failure. transmitted by both wild and domestic animals. - urine as mode of transmission!!

• Most common animals that spread the disease are rodents. Transmitted by animal urine or water containing animal urine coming into contact with breaks in the skin, the eyes, mouth, nose or vagina.

• Leptospirosis is a two-phase disease that begins with flu-like symptoms (fever, chills, myalgias, intense headache). First phase usually resolves (90%)

• If it progresses to the second phase expect liver damage, renal failure, meningitis, encephalitis

Treponema pallidum - gram negative spirochetes - trepenoma

Spirochete of syphilis; produces painless chancre, systemic rash, and possible tertiary gummas.

Spirochetes: little "corkscrew-like" things

• Have internal flagella in bundles called axial filaments; twist through liquid media

Treponema pallidum: cause of syphilis (an STI), other forms are nonvenereal like bejel, yaws, etc.

- Initial stages: chancre, hard, painless genital ulcer following long

incubation

- Ulcer disappears, spirochete spreads, causes systemic disease (rash, fever, etc)

- Either goes away, comes back, or tertiary syphilis in which gummas form; serious stage. gumma is a soft, non-cancerous growth resulting from the tertiary stage of syphilus. It is a form of granuloma.

Borrelia burgdorferi - gram negative spirochetes

Tick-borne spirochete causing Lyme disease with bull’s-eye rash, arthritis, and neurological signs.- cause of Lyme disease

- Reservoir in rodents, deer; spread by deertick

- Slow developing; fever, usually bulls-eye rash; arthritis and heart or CNS involvement.

(No LPS. • Antigen switch. • Secretes proteins that inhibit proper function of blood vessels, platelets, and cartilage.)

Borrelia recurrentis - gram negative spirochetes

Louse- or tick-borne agent of relapsing fever; evades immunity by antigenic variation. - cause of relapsing fever

- Human reservoir, spread by lice or ticks

- Causes fever which comes and goes

- Microbe switches antigens, makes comeback, then immune system catches up again.

Vibrio cholerae - gram negative curved rods - vibrio

Halophilic curved rod; cholera toxin triggers massive watery diarrhea treatable with ORT.

Vibrio:

• Like enteric; polar flagella

• Halotolerant to halophilic, grow in estuarine and marine environments

V. cholerae: cause of cholera - fecal-oral transmission kind of route - get into GI, defacate, get into water, spreads rapidly around a community

• Toxin-mediated severe diarrhea

• Salt, fluid leave intestinal cells, patient dies of dehydration.

• Oral rehydration therapy (ORT): water, salts, and glucose, now saving lives. - rehydration, modern treatments

• Causes pandemics that spread around the world

• Lack of adequate sewage treatment

Campylobacter jejuni - gram negative curved rod, campylobacter

Flagellated curved rod; leading cause of bacterial gastroenteritis from poultry and raw milk. -number one cause of bacterial gastroenteritis; zoonotic - food poisoning like

• More common than Salmonella and Shigella combined for food borne disease. - little less severe

• Most retail chickens are contaminated; improperly cooked chicken and contaminated milk are typical vehicles.

• Low infectious dose - doesnt take much to make you sick

(Flagella plus chemotaxis)

Helicobacter pylori - gram negative curved rods - helicobacter

Stomach-dwelling curved rod producing urease; causes gastritis, peptic ulcers, and is cancer-linked. - Cause of ulcers and gastritis

• 2005 Nobel Prize for Medicine or physiology to Barry Marshall and J Robin Warren

• Unusual because it can live in stomach

• Produces urease enzyme

• Released ammonia (base substance) neutralizes stomach acid, irritates stomach lining.

• Basis for radioactive urease test.

- Correlated with stomach cancer.

(Flagella and cytotoxin)

Urease

Enzyme converting urea to ammonia and CO₂; H. pylori uses it to neutralize stomach acid.

Oral Rehydration Therapy (ORT)

Life-saving mixture of water, salts, and glucose used to replace fluids lost in cholera and other diarrheas.

Buboes

Painful, enlarged lymph nodes characteristic of bubonic plague.

Disseminated Intravascular Coagulation (DIC)

Systemic clotting and bleeding disorder that may follow severe endotoxin exposure.

Axial Filament

Internal flagella bundle enabling spirochetes to corkscrew through viscous media.