Properties of Bacteria, Bacterial Infections, Anti-biotic Resistance

What are the general characteristics of a prokaryote cell?

• Simpler structure, typically smaller, no distinct nucleus, no membrane-bound organelles

How are prokaryotes similar to eukaryotes?

Both prokaryotes and eukaryotes have cell membranes, chromosomes, cytosol, bound by a plasma membrane, and ribosomes

Eukaryotes

• Has nucleus surrounded by membrane, has distinct organelles surrounded by membranes

What are the three common shapes of bacteria?

• Bacilli: single or in chains, ex, E. Coli

• Cocci: not usually motile, chains and clusters, ex, Streptococci and Staphylococci

• Spirilli: usually motile, spirals, ex, Lyme disease

What layers make up the bacterial envelope?

• Cytoplasmic membrane

• Membrane cell wall

• Capsule

• Slime

• Flagella

• Pili 

What organelles are typically found inside bacteria?

• Nucleoid

• Ribosomes

• Granules 

• Endospore 

What is the bacterial capsule made of?  

• Made of polysaccharide layer that lies outside the cell envelope

• Helps protect bacteria from pathogens and dessication 

What is the bacteria cell wall made of?

• Made of peptidoglycans

• Rough and rigid in structure 

What layer will be thick in a gram positive cell?

Peptidoglycans

Where are the pili found? 

• Found on the surface of bacterial cells 

• Attach to host cell tissue

What are the functions of the pili?

• Bacterial conjugation (sex pili)

• Colonization antigens (virulence)

• Can adhere to RBC’s

What are endospores.

• Endospores are tough, dormant, non-reproductive structures formed by certain bacteria to survive extreme conditions

What do endospores do?

• Protects cells against harsh environments 

• Produced under stress

How does bacterial DNA recombine? (3 processes)

• Transformation

• Transduction

• Conjugation

DNA recombination: transformation

• Uptake of naked foreign DNA from environment 

• Cell can recognize related DNA, incorporate it into genome 

DNA recombination: transduction

• Phages carry genes from one bacteria to another 

  • Lytic cycle, some bacterial DNA in phage head, recombines with new host DNA (cross-over)

DNA recombination: conjugation

• Direct transfer of DNA between bacteria

• Formation of mating bridge

• F DNA factor needed to donate DNA

F Plasmid

• Plays key role in bacterial conjugation 

• Transfers single strand of DNA to mate

• Each mate replicates plasmid strand 

What is an HFr cell?

• Hfr - high frequency recombination

• F factor (plasmid) incorporated into genome 

Mating bridge 

• Single strand of DNA transferred (only partial)

• Replication and recombination (cross-over, left over degraded)

What do transposons do?

• Code for transposase PLUS other genes

• Cut and paste new genes in new location 

• Copy and paste 

What do operons do?

• Control production of mRNA which makes proteins or enzymes 

What factors determine the virulence of a bacteria?

• Adherence, persistence, invasion, toxigenicity 

What are the stages of bacterial infection?

• Transmission: from external source via portal of entry

• Invasion of primary host defenses: ex, skim or stomach acid

• Adherence to mucous membranes: usually by bacterial pili

• Colonization: growth of the bacteria at the site of adherence 

• Disease: symptoms caused by toxin production or invasion accompanied by inflammation 

What factors determine adherence?

• Pili allow the bacteria to attach to host cell (most common)

• Glycocalyx (allows attachment) 

• Formation of capsules (prevents phagocytosis)

• Presence of spikes 

How do exotoxins and endotoxins differ?

• Exotoxins: By gram + and gram - bacteria 

• Endotoxins: Part of the cell wall, in gram + bacteria only 

How do antibiotics work?

• Target bacterial cell wall/membrane or organelles/ DNA

• Do not work on viruses 

What are three examples of normal human flora?

• Staphylococcus

• S. Aureus

• Lactobacillus 

What is the advantage to having human flora?

• Can synthesize and secrete vitamins

• Aid in digestion 

• Prevent colonization by pathogens 

• Produce substances that hurt or kill non-indigenous bacteria 

What are some classes of pathogenic bacteria?

• Cocci (staphylococcus, streptococcus)

• Bacilli (e-coli, salmonella)

• Vibrios (gram - rods, in fresh and salt water, cholera)

• Spirilla (untreated water, uncooked meat, treponema: syphilis, borrelia burgdorferi: lyme disease)

• Spirochetes (treponema pallidum: syphilis, borrelia burgdorferi: lyme disease)

How do vibrios move and where do they normally live?

• They move using a single polar flagellum

• Found in fresh and salt water 

How is cholera transmitted?   Where does it affect the host?   What are the symptoms?

• Transmitted through contaminated water

• Attacks microvilli of the gut brush border and secretes enterotoxins 

  • result in prolonged hypersecretion of water and electrolytes

• Symptoms: diarrhea, profound dehydration, shock, acidosis

How is typhoid transmitted?   Where does it affect the host?   What are the symptoms?

• Transmitted through fecal-oral route, close contact with patients or carriers, contaminated food or water, flies and cockroaches

• Primarily affects the small intestine

• Symptoms: slow rising fever, abdominal pain and myalgia, distention, hepatomegaly, fatigue, headache, constipation (early), diarrhea (later), red spots may appear

How is conjunctivitis transmitted?   Where does it affect the host?   What are the symptoms?

• Spread through direct contact with eye secretions: ex, towel, brushes, pillow case, hands, makeup

• Affects the eye 

• Symptoms: redness, swelling, pus-like discharge

What are the two common bacteria seen with conjunctivitis?

• Staphylococcus aureus

• Streptococcus pneumoniae

How is necrotizing fasciitis transmitted?   Where does it affect the host?   What are the symptoms?

• Transmitted through puncture wounds, cuts, scrapes, insect bites, surgery

• Affects the fascia (CT)

• Massive inflammation, fever, chills, nausea, pain, necrosis of tissue

How is leprosy transmitted?   Where does it affect the host?   What are the symptoms?

• Transmitted through prolonged, close contact with an infected person, typically by respiratory droplets

• Causes damage to skin and peripheral nerves 

  • Loss of sensation in the affected patch, muscle weakness

• Symptoms: skin lesions and deformities (cooler places of the body: eyes, nose, earlobes, hands, feet, testicles)

How is pertussis transmitted (whooping cough)?   Where does it affect the host?   What are the symptoms?

• Transmitted through contact via aerosolized droplets from an infected person 

• Affects the respiratory track 

• Symptoms: inspiratory whoop like cough, followed by vomiting, minimal to no fever 

Lobar pneumonia

• Streptococcus pneumoniae

• Treat with antibiotics

• Localized pattern

Bronchopneumonia

• Can be bacterial

• Or obstruction of bronchi

• Due to gastric aspiration 

• Diffuse pattern within the lobe

Interstitial

• Chronic inflammation 

• Not true infection 

• Diffuse pattern and bilateral 

How is tuberculosis transmitted?   Where does it affect the host?   What are the symptoms?

• Transmitted through airborne respiratory droplets

• Inflammation in soft tissues in lungs that may cause caseous lesions 

• Symptoms: persistent cough, coughing up blood, fever, chest pain, fatigue

Why are UTI’s more common in women?  

• Shorter urethra

• Closer to rectum 

• Vagina and pregnancy

How is syphilis transmitted?   Where does it affect the host?   What are the symptoms?

• Transmitted through direct contact with syphilis sore, ex, skin to skin, sex, birth

• Affects skin, genitals, mouth, rectum, blood stream

• Symptoms: 

  • Primary: painless chancres at infection site

  • Secondary: chancres heal, rashes start, muscle aches, fever, sore throat, fatigue

  • Latent: can last years

Tertiary: effects the brain, nervous system, eyes, heart, liver, bones, life threatening

How is plague transmitted?   Where does it affect the host?   What are the symptoms?

• Transmitted though airborne or fleas (bacterium Yersina pestis)

• Affects lymph nodes, blood stream, lungs

• Enlarged lymph nodes, high fever and fatigue, severe headaches, muscle aches, nausea, vomiting

What are the modes of action for anti-biotics?

• Affecting the cell membrane structure

  • Cell wall synthesis inhibitors

  • Cell membrane disruptors 

• Affecting cell function 

  • Synthesis inhibitors: proteins, RNA, folate

• DNA gyrase inhibitor 

  • DNA can not unwind to replicate 

What is the mode of action for penicillin?   Tetracyclines?

• Penicillin: prevent bacteria from making cell walls

• Tetracyclines: inhibits protein synthesis 

How do bacteria resist antibiotics?

• Inactivate enzymes

• Efflux pump

• Block entry

• Target modifiers

• Enzyme bypass 

What are the main causes of anti-biotic resistance?

• Antibiotic modification 

• Denied access

• Pumping out the antibiotic faster than it gets in 

• Altered target site

• Production of alternative target

What occurs when you do not complete a round of antibiotics?

• Remaining bacteria that hasn't been killed off survive and multiply, developing resistance 

Why are antibiotics not effective on viruses?

• Antibiotics attack bacterial infections not viral infections

• Viruses do not have cell structures due to using host cells which antibiotics need to target

Why is dosing and the timing of doses important for antibiotics?

• Strong enough dosage to kill all bacteria to prevent resistance 

• Constant timely distribution of antibiotics for constant, sustained exposure

What are the main pathogens displaying antibiotic resistance?

• MSRA, VRE, C-Difficile, CRE

What is MRSA?    What infections are seen?

• MRSA: Methicillin-resistant Staphylococcus aureus

• Resistant to methicillin, ampicillin, erythromycin, tetracycline

• Mainly treated with vancomycin

• Vancomycin-resistant strains have already appeared

• Commonly found on the skin

• minor infections (pimples, boils)

• serious infections (pneumonia, wound sepsis)
  
  

What is VRE?   Where do most cases occur?

• Vancomycin resistant enterococci

• Found in the gut it can spread to cause UTI, sepsis, wound infections, infections in catheters and IV lines

• Most cases occur in long term care residents 

What is C Difficile?   What are the symptoms?

• Hospital born super bug that leads to diarrhea and complications in the colon 

• Fever, nausea, abdominal pain, watery diarrhea