MICROBIO EXAM 3 CH 11: Host microbe interactions

interactions between organisms 

• if organisms of 2 species interact with each other, there can be these outcomes (forms of symbiosis)

  • both benefit

  • one benefits, other isn’t affected

  • one benefits, one is harmed

  • one is harmed, other is not affected 

symbiosis: mutualism

• both benefit (+/+)

• ex. bees get nectar from a plant, plant gets a way to spread pollen

  • bacteria in gut that help you break down your food

symbiosis: commensalism

• one species benefits, other not affected

• ex. burrs that get stuck in sheep’s wool get dispersed elsewhere

  • sheep does not mind, plant benefits

symbiosis: parasitism and predation 

• parasitism 

  • one organism benefits, other is hamred

  • pathogens causing disease

    • viruses take over cellular function, frequently killing the cell

• predation

  • predator eat prey

symbiosis: amensalism

• one is harmed, one doesn’t benefit

• ex. large pine trees shed needles on the ground and those needles decompose the soil is acidified so grass can’t grow in that soil

the nature of a relationship can change

• some organisms that are beneficial or harmless can become harmful

  • opportunistic pathogens

    • commensal gut bacteria can become pathogenic

    • ex. staphylococcus aureus usually non-harmful but given right conditions → severe skin infections

    • ex. C difficile exists at low levels in large intestine

      • if normal gut flora is reduced, C difficile can grow excessively, leading to a chronic infection

• conditions that can provide opportunities

  • compromised immune system

  • malnutrition

  • excessive antibioitic treatment

microbiology and humans

• human body is mostly non-human

  • more bacterial cells than human cells

    • more viruses than bacterial cells

• microbes are everywhere

  • On the skin

    • 10 4 -10 6 CFU/cm2

      • Varies by surface

  • In the nose

    • 10 4 CFU/nasal swab

  • In the lungs

    • 10 4 CFU/ml

  • In the urogenital tract

    • 10 6 -10 8 CFU/ml

• microbes in digestive tract

• microbes differ by location on the body, age, and from person to person, geography, dietary lifestyle, antibioitic use, health

toxic shock syndrome

• cause: staphylococcus aureus

• how/mechanism: opportunistic pathogen

  • produce set of toxins that cause massive immune reaction

  • toxins → bloodstream

  • can occur through wounds getting infected

• symptoms: fever, vomiting, rash, rapid blood pressure loss, loss of skin, FATAL (5% of cases)

• virulence factors

  • beta-lactamase

    • make it resistant to penicillin antibiotics

  • toxic shock syndrome toxin

    • cause immune reaction

• treatments

  • prevention of organ failure 

    • antibiotics (are not beta-lactams)

      • challenging b/c of abx resistance genes 

      • MRSA is resistant to methicillin

      • VRSA is resistant to vancomycin 

pharyngitis

• cause: streptococcus pyogenes

  • anaerobic hemolytic gram + bacterium -→ scarlet fever, rheumatic fever, and pharyngitis (strep throat)

• how/mechanism

• symptoms

  • swollen lymph nodes, inflammation of back of pharynx, pus-filled abscesses covering the tonsils 

• virulence factors

  • capsule that contains hyaluronic acid 

    • camouflage against immune system 

  • M-protein (membrane protein)

    • protects bacterial cell from being targeted by immune cells 

• treatments

  • long-term antibiotics

  • anti-inflammatories

botulism

• cause: clostridium botulinum

  • rod shaped, gram +, spore forming, obligate anerobe found in soil

  • ingestion of the toxin rather than live cells in adults

  • children: ingestion of spores

• how/mechanism

  • produce toxin that acts as muscle relaxant → paralysis

• symptoms

  • blurred vision, dizziness, dry mouth

• virulence factors

  • most toxic proteins

    • binds to ends of muscle-controlling neurons → stops neuron from transmitting message to muscle -→ paralysis

  • endospore

• small doses of toxin can be directly injected into specific muscles for desirable effect (Botulinum toxin = botox)

• treatments

  • repeated washing of intestinal tract to remove clostridium

  • antibodies to neutralize toxin

  • antibiotics in infant infections

• may be permanenet or last for years

pseudomembranous colitis (AKA c-diff)

• cause: clostridium difficile 

  • gram-positive, spore forming rod

  • GI tract

• how/mechanism

  • becomes pathogen following broad spectrum antibiotics treatment

    • normal gut microbiome dies off, c-diff survives and reproduces rapidly

• symptoms

  • leads to colitis, inflammation and possible ncerosis of the colon walls → internal bleeding and possibly death, especially in elder patients

• virulence factors

  • produces toxins and enzymes that cause hemorrhagic death of the intestinal walls

  • spores are resistant to antibiotics such as cephalosporin and penicillin

• treatments

  • stronger antibiotics such as vancomycin or metronidazole kill vegetative cells 

  • repopulation of the GI tract with healthy community of microbes 

    • fecal transplants from healthy colons are effective against recurring infection

tuberculosis

• cause: mycobacterium tuberculosis

  • gram-positve, acid-fast, aerobic bacillus

• how/mechanism

• symptoms

  • persistent productive cough, frequently with blood in the sputum 

  • fever, weakness, and more 

  • lungs are affected but more organs can be affected

• virulence factors

  • low virulence (people can be carriers but rate of tuberculosis is low)

  • mycolic acid (makes cells acid-fast)

    • protects cell from the immune system

      • won’t be digested in the lysosome

    • protects from dehydration

      • cells can survive outside the body for months

• treatments

  • long-term antibiotics WHICH ONES?

whooping cough

• cause: bordetella pertussis

  • non-motile, aerobic, gram-negative coccobacillus

• how/mechanism

• symptoms

  • cold-like to persistent deep cough

  • frequently 40-50 coughing spels every day have consequences

    • difficulty breathing

    • broken ribs

    • exhaustion

    • vomiting

• virulence factors

  • pertussis toxin

    • specific adhesin to help attach to host cell

  • 2 toxins that increase mucus production in tracheal cells

  • tracheal cytotoxin prevents cilia from moving so mucus stays in place and bacteria replicate

• treatments

  • treat individual symptoms

  • immune system can kill the bacteria

  • prevention

    • vaccination

• mainly in infants

• known as pertussis

syphilis 

• cause: treponema pallidum 

  • thin gram-negative spirochete, obligate parasite

  • spiral shape helps it attach to epithelial cells → multiplies rapidly and penetrates into capillaries

• congenital syphilis

  • infected individuals who become pregnants may transmit it to their embryos

• how/mechanism

  • sexually transfmitted infection that has 3 stages

  • primary syphilis

    • a chancre (type of ulcer) forms at the site of infection

      • painless

      • goes away on its own in 3-6 wks but infection is still present

  • secondary syphilis

    • 3 wks to 6 months post-infection 

    • body rash, fever, headaches, sore throat

    • many go away on its own 

    • complications can occur in the bones, joints, liver, eyes and brain 

  • after 2ndary syphilis, 30% of infections can enter a latency that can last for years and decades

    • infected and can transmit it but no symptoms 

  • tertiary syphilis

    • benign tumors AKA gummas form in the liver, skin, bone, and cartilage

    • painful but not fatal

    • impair function

    • neurosyphilis

      • infection of nervous sytem

      • blood vessels in the brain, cranial nerves, and dorsal root of spinal cord

      • symptoms

        • severe headaches

        • convulsions

        • blindness

          • argyll-robertson pupil

          • dementia

• symptoms

• virulence factors

• treatments

  • antibiotics 

    • ciprofloxacin

    • before, mercury and arsenic were used

  • prevention

    • contact avoidance (condoms) as well as treatment of infected before sexual contact

gonorrhea

• cause: neisseria gonorrheae

  • gram-negative aerobic diplococcus

• sexually transmitted disease with different symptoms in men and women

  • males

    • painful urination, pus, and infertility (rare)

  • women

    • 50% asymptomatic

    • 50% mistaken for bladder infection

    • bacteria cannot attach to vaginal cells, so it attaches to cells farther up the genital tract

      • cervix, uterus, fallopian tube → pelvic inflammatory disease

• virulence factors

  • fimbriae attach to host cell

  • capsule

  • enzymes destroy host antibodies

  • constantly-changing surface proteins 

    • host doesn’t develop long-term immunity 

• treatment

  • antibiotics 

    • cephalosporins 

• challenge: resistant strains are arising AKA super gonorrhoea

enteric diseases

• cause: enteric bacteria 

  • ex. escherichia coli, salmonella, and yersinia

    • subgroup called coliforms 

      • facultatively anaerobic, gram-negative rods that don’t form endospores and can ferment lactose 

      • associated with fecal contamination 

• virulence factors

  • capsules and fimbriae

  • toxins that lead to diarrhea

  • hemolysins

  • type-3 secretion systems (T3SS)

bubonic plague

• cause: yersinia pestis 

  • enteric bacterium

  • different strains have different severities

• symptoms

  • high fever and buboes (very swollen lymph nodes)

• if untreated, bacteremia (bacteria in blood), necrosis of tissue, and death can occur 

• transmitted by fleas on rodents 

• black death killed 1/3 of europe 

• squirrels in modern day 

• virulence factor

  • type-3 secretion system and its toxins 

    • secretion system creates a link between bacterium and host phagocyte (immune cell) 

    • toxin induces apoptosis (programmed cell death) in the immune cell, so it doesn’t attack the Y pestis cell 

• treatment

  • antibiotics, esp with early detection

  • prevention

    • control rodent populations 

hepatitis

• inflammatory condition of liver

  • liver functions to

    • store sugar and regulate blood

    • production of clotting agents

    • removal of toxins in body 

• symptoms 

  • jaundice 

    • accumulation of bilirubin (metabolic waste product) in the blood → yellowing of skin and eyes 

  • abdominal distress

  • bleeding into skin and internal organs 

  • chronic inflammation leading to cirrhosis 

• multiple causes 

  • hepatitis B virus

    • partially dsDNA and ssDNA genome

    • replicates with RNA intermediate 

    • infects liver cells, then is released by exocytosis

      • the cell doesn’t die so it continues to make more virions (billions)

    • viral replication releases a lot of incomplete viral particles

      • caspid proteins coated with surface antigens, but no genome

        • not infectious but recognized by the immune system → overwhelms the immune system 

• hepatitis B epidemiology 

  • transmission via bodily fluids 

  • infectious 

  • high viral load in infected individuals, infective dose is relatively low 

• treatment is harder than prevention 

  • vaccination is effective (95%)

disease in populations

• epidemiology

  • study of the frequency and distribution of disease and other health-related factors in a population

    • how frequent are outbreaks?

    • who is susceptible?

    • where does the disease come from?

  • multiple fields of biology, psychology, meterology, climatology

stages of disease

• infection

  • acquisition of pathogen, or its transition into pathogenicity

• incubation

  • time between infection and arrival of first symptoms

    • can be hours or years

• prodromal period

  • generalized, mild symptoms arise

  • gradual immune response 

• illness

  • symptoms are most evident 

  • where disease is usually identified 

• decline

  • when treatment or immune system work to combat the disease 

• convalescence

  • recovery from the disease

• can be infectious at any stage

where does disease come from?

• animal reservoirs

• human carriers

• nonliving reservoirs

animal reservoirs

• zoonotic diseases

  • diseases spread by animals

• transmission

  • eating infected animal

  • contact with animal waste

  • animal bites

  • biological vectors 

• control can be challenging 

  • if there are many animals

  • if the animals are wild 

    • aka tics

human reservoirs

• frequently asymptomatic

• may not require direct contact 

• contact with contaminated materials 

• nosocomial infections

  • arise when patient is hospitalized for something else → often opportunistic pathogens 

nonliving reservoirs

• water, food, soil

  • often contaminated by contact with infected individual 

• parasites such as giardia can be found in bodies of water where animals defecate

• tetanus and anthrax spores can be found in water

methods of transmission

• pathogens spread by people or by objects that people touch

  • direct contact: person to person

  • indirect contact: objects to person 

  • droplet transmission: cough/sneeze, usually less than 1 meter

  • vehicle transmission: pathogens are spread by some nonliving intermediate 

  • airborne transmission: droplets move more than 1 meter 

    • air conditioning, wind, sweeping, shaking out clothes 

  • waterborne transmission: contaminated water source 

    • fecal oral route

  • foodborne transmission: cotnamined food

    • fecal oral route

  • bodily fluid transmission 

    • fluids behind handled outside the body 

    • ex. blood transfusions 

  • vector transmission: spread of pathoen through intermediate animal 

    • insect carries disease, doesn’t cause it

  • biological vectors: pathogen reproduces within a vector, usually has a step in its life cycle that requires the vector 

    • mosquitos carrying malria, fleas carrying plague 

  • mechanical vectors: pathogen does not reproduce within vector but vector physically moves the pathogen

    • houseflies land on some contaminant and then land on your food