ch11 bacteria (gram negative)

Chapter 11 Bacteria

Intro: Domain Bacteria

  • one circular
  • no organelles
  • peptidoglycan (bacteria)
  • reproduce by binary fission

Gram Negative Bacteria

Rickettsia rickettsii

  • Obligate intracellular bacteria
    • 1 of 2 bacteria that are obligate intracellular
    • in order to cultivate it, we need tissue culture
  • Spotted fevers (Rocky Mountain Spotted Fever) aka RMSF
    • vector is dog tick
    • location: found in Pennsylvania, one of the leading tick-borne disease (before Lyme disease)
    • signs and symptoms
      • measles-like spotted rash, unique bc on palms and soles too; fever
      • muscle pain, can cause death
    • diagnosis
      • cell culture (takes a while)
      • serology
        • direct: look for antigen (microbe)
          • Rickettsia rickettsiae bacteria
        • indirect: look for antibody (immune response)
    • treatment
      • antibiotic: tetracycline

Neisseria

  • Gram negative diplococci
    • have flattened side (like a coffee bean) ☕
  • fastidious - enriched culture media
  • capnophiles - increased CO$^2$
  • Neisseria gonorrhoeae
    • urethral gram stain is diagnostic
    • gonorrhea (STI)
      • females are asymptomatic, can still cause complications
      • 2nd most common STI
        • #1 is chlamydia
    • Signs and Symptoms
      • males - urethral pus containing discharge (use as sample)
      • fever
      • inflammation
      • presence of WBCs
      • may have anal / throat infection
      • gonococcal arthritis (joint pain)
      • pelvic inflammatory disease (for females)
        • scarred fallopian tubes, infertility, ectopic pregnancy
    • Diagnosis
      • Culture media: Thayer Martin Agar
        • use CO$^2$ generator
      • ELISA
      • DNA probes
      • PCR - urine sample
        • test for nucleic acid
        • PCR is also used for COVID (nasal swab)
      • watch out for patient being co-infected (more than 1 STI), causes more complications
    • Treatment: antibiotics
      • resistance has recently increased
        • plasmids → pili
      • correct antibiotic = cured
      • however can get gonorrhea multiple times
        • most diseases have an immune response that protects from a second disease
      • herpes - viral
        • can have for life
    • Transmission:
      • STI
      • perinatal (ophthalmic neonatorum)
        • mother transmits through vaginal birth
        • leading cause of blindness of newborns
        • give silver nitrate or antibiotic eye drops to newborns to treat
    • Prevention
      • condom, abstinence
  • Neisseria meningitis
    • most lethal neisseria
    • Causes meningococcal meningitis
      • bc gram negative, can cause endotoxic shock
    • Transmission: respiratory droplets
      • talking, sharing drink, sharing lipstick
      • fomite (i.e. lipstick)
    • Signs and Symptoms
      • fever
      • severe headache
      • stiff neck
      • flu-like symptoms (lethargy)
      • inflammation
      • rash
      • may have purple fingers; result of endotoxic shock
        • lead to amputation or death
      • nausea, vomiting, dizziness
    • Diagnosis
      • rapid latex agglutination for capsular antigen
      • gram stain and culture
      • PCR test
      • serotype B is most common in US
        • capsular
        • A, B, C…
    • Treatment: antibiotics, prophylactic (guard from close contact & transmission)
      • penicillin, cephalosporins
        • sometimes patient has penicillin allergy
      • vaccine

Bordetella

  • gram negative rod to coccobacilli
    • mostly rod-like
  • B. pertussis causes whooping cough / pertussis
  • concern of young children
    • because they have small tracheas
  • Virulence factors
    • capsules
      • defense mechanisms to prevent phagocytosis
    • exotoxins
      • tracheal cytotoxin
        • ciliated cells (escalator) in lungs are affected, leading to build up of mucus and coughing (gasping for air, inspiration with coughing)
  • Pertussis: 3 stages
    • Catarrhal stage: like common cold
      • 1-2 weeks
    • Paroxysmal stage: violent coughing sieges, mucus accumulation, cyanosis
      • can last 1-6 weeks
    • Convalescence stage
      • couple weeks to months
  • may cause
    • seizures, convulsions
    • brain damage
    • death
  • treatment: antibiotic
    • erythromycin
  • diagnosis
    • nasopharyngeal swab (not sputum) onto Bordet Gengou agar, serology, PCR
    • some viral infections can mimic a whooping cough so must test
  • immunofluorescence
    • serology (antigen-antibody)
    • add fluorescent dye to antibody, antibody attaches to organism, shine UV light on it
  • transmission: respiratory droplets
  • prevention
    • acellular or inactivated whole agent vaccine
    • pertussis vaccine
      • does not last a lifetime

Burkholderia

  • nosocomial infections
    • hospital associated infection (HAI)
    • not properly disinfected equipment
  • Burkholderia cepacia
    • motile, aerobic gram negative rod, endotoxin
    • respiratory pathogen in cystic fibrosis or pneumonia patients
    • resistant to disinfectants / antibiotics
      • biofilm in respiratory tract
    • signs and symptoms: coughing, fever
    • diagnosis: gram stain

Pseudomonas aeruginosa

  • characteristics
    • gram negative bacilli
    • opportunistic
      • needs few nutrients to grow
      • found in odd places like in disinfectants
      • immunocompromised are at most risk
    • polar flagella
    • nosocomial infections (HAI)
  • diagnosis
    • can be grown on TSA, not picky, can grow anywhere
      • has green pigment
      • fruity odor 🏳️‍🌈
    • macconkey agar
      • non-lactose fermenter
      • differential: CHO, lactose
  • transmission
    • post-burn infection
      • place patient in water bath
      • water can have pseudomonas aeruginosa
    • patients on ventilators
      • respiratory equipment can be contaminated
      • causes lung infection, pneumonia
    • foley catheters, causes UTI
    • post surgical incision sites
    • in swimming water
      • infects ear (swimmer’s ear)
  • treatment: antibiotics

Legionella pneumophila

  • causes Legionnaires disease (serious type of pneumonia)
    • aka legionellosis
  • found in streams, warm-water pipes, cooling tower
    • decorative fountains
  • outbreak in 1976 Bellevue Stratford Hotel
    • in New York
    • immunocompromised people are affected
  • transmission
    • cannot spread from person to person, infected by aerosolized contaminated water
    • “airborne”
  • diagnosis
    • culture
      • buffered charcoal yeast extract agar
    • FA tests (direct serology, PCR)
    • DNA probes
  • treatment: erythromycin (antibiotic)

Vibrio

  • Cholera
    • signs and symptoms
      • severe fluid loss from profuse diarrhea
        • can lose up to 3-5 gallons of fluid
        • “rice-water” stools (clearish white liquid with pieces of floaty intestinal epithelium)
      • no fever
      • “tenting” in pinched skin (sign of severe dehydration)
    • exotoxin
  • characteristics
    • motile, comma-shaped bacilli
    • halophile
  • diagnosis: culture media with increased salt concentration
  • transmission
    • found in coastal water (common when traveling)
    • fecal, oral = contaminated food
    • largest outbreak in Haiti
      • also in areas with civil unrest, developing countries
  • prevention
    • adequate water treatment
    • properly cooked food
    • hand washing, hygiene
    • make sure open wounds are clean
  • treatment: fluid & electrolyte replacement
    • antibiotics can help

Enteric bacteria

  • characteristics
    • gram negative straight rods
    • facultative anaerobic
    • ferment glucose and other carbohydrates
    • motile (peritrichous flagella)
  • 2 categories: normal flora / disease, pathogens
    • Normal flora / disease - can cause infectious disease if in the wrong place
  • can include many bacterias
    • certain strains of e. coli, salmonella, campylobacter, shigella, clostridium, listeria

Escherichia coli

  • this can be abbreviated to E. coli
  • grows on EMB / MAC agar
    • lactose fermenter - key hint of ID
  • indole positive
    • catabolism of tryptophan
    • red layer at top of tube
  • most common cause of UTI
    • 85% of UTIs
    • bladder infection = cystitis
      • can progress into kidneys and bloodstream
      • kidney infection can cause back pain
    • treatment: UTI
    • prevention: natural cranberry juice? (not ocean spray brand)
  • Gastroenteritis
    • traveler’s diarrhea
    • enterohemorrhagic (EHEC)
      • E. coli O157:H7
        • this strain produces exotoxin that damages kidneys (Hemolytic Uremic Syndrome / HUS)
        • kidney failure = dialysis
    • can be exposed through contaminated water (ice cubes, when brush teeth), and raw milk
  • Neonatal meningitis
    • mother has UTI spread to infant thru vaginal birth
    • infant aspirates e. coli
  • decubiti - in nursing home when person is bedridden and develops pressure sores from laying in one position too long
    • lying in feces causes e. coli infection

Proteus mirabilis

  • part of normal flora in intestines
  • extremely motile
  • diagnosis
    • BAP and TSA
      • put colony in center of plate
      • swarming colony
        • film on plate
    • urease test
      • hot pink = urease +
      • urea → ammonia, ^pH
  • transmission: endogenous
  • causes UTI, but no intestinal infection
  • decubitus (pressure ulcer / bed sore)
    • pus, fever

Salmonella enterica

  • Gastroenteritis (Salmonellosis)
    • Symptoms: diarrhea, vomiting, abdominal cramp, low grade fever
      • not diagnostic because it can be viral or other bacteria
    • Transmission: fecal-oral route (food)
      • poultry
      • reptiles (especially turtles)
        • little turtle infect da kid
      • hedgehogs
      • fish
      • duckling
    • Diagnosis: stool culture; signs and symptoms begin 12-36 hours after eating
      • takes ~1 mil organisms to cause this illness
    • Treatment: self limiting
      • no antibiotic treatment needed, just rehydration
    • Prevention:
      • don’t eat raw eggs or meat
      • cook da egg

Haemophilus influenzae

  • found in upper respiratory tract
  • Characteristics
    • fastidious (enriched media) and capnophile
      • Chocolate agar in CO2
      • X (heme) and V (NAD) factors for growth
        • disks with factors placed in TSA plate
        • growth area around the disk
    • does not cause the flu
      • they named it influenzae because they used to think this caused the flu
    • Gram negative coccobacilli to rod
      • pleomorphic
  • Causes epiglottitis, bronchitis, conjunctivitis, otitis media
    • bronchitis - pneumonia
      • found in alcoholics
    • pink eye - non life threatening
      • usually this is a viral infection but can be caused by this too
    • otitis media = middle ear infection
      • toddler
      • migration from respiratory infection
      • can be difficult to treat with antibiotics
  • Encapsulate H. influenzae type B causes epiglottitis and meningitis
    • can be life threatening to toddlers
    • causes suffocation
  • Don’t see very much because of vaccine
  • Transmission: respiratory droplets (coughing)
  • Treatment: antibiotics

Camplyobacter jejuni

  • gram negative curved bacilli (seagull)
  • one polar flagellum
  • common cause of gastroenteritis in US
    • Camplyobacteriosis
  • grows on CAMPY agar
    • low O2 (microaerophilic)
    • 42 C (slightly above body temp to eliminate other bacteria)
  • Transmission: fecal-oral
    • raw milk
    • poultry
    • meats
    • apple cider
  • Treatment: erthryomycin or quinolones
    • more likely to treat with antibiotics than salmonellosis
    • rehydration

Helicobacter pylori

  • suggested cause of ulcers
    • dude drank a culture and did kochs postulates on himself to prove microbial cause
  • enzyme urease is able to break down ammonia to urea
    • buffering effect, allows it to grow in stomach mucosa
  • stomach (peptic) ulcers signs and symptoms
    • bleeding in stomach
      • does not cause red bloody stools like intestinal bleeding, causes dark stools
    • abdominal pain
  • Transmission: Helicobacter is ubiquitous
    • can be caused by eating food (ingestion)
      • can’t be solved by stop eating food 😞
  • Diagnosis: gastric biopsy, (indirect) serology, urea breath test
  • Treatment: Bismuth subsalicylate (pepto bismol) and several antibiotics
    • heavy metals also can help

Chlamydia

  • numba one bacterial STI
  • obligate intracellular bacteria
    • second other bacteria
    • Chlamydia life cycle
      • elementary bodies form reticulate body
  • signs and symptoms: pain, watery urethral discharge
    • females are often asymptomatic
  • Diagnosis: cell culture, immunofluorescence (direct serology), PCR test from urine sample
    • cell culture is costly to maintain, not preferrable
  • Transmission: sexual, perinatal
    • infants can get eye, lung infections at time of delivery
    • if female not appropriately treated, leads to PID (pelvic inflammation)
  • Treatment: tetracycline

C. trachomatis

  • trachoma
    • can be from poor sanitation (developing countries)
      • touching eyes / face (not sexually transmitted)
    • leading cause of blindness
  • STI
    • disease has signs and symptoms, these can be asymptomatic
  • urethritis

C. pneumoniae

  • atypical (mild) pneumonia
  • in older adults

Spirochetes

  • axial filaments and sheath
  • cannot gram stain (closely related to gram negatives)
    • silver stain

Treponema pallidum

  • causes Syphilis
  • signs and symptoms
    • genital lesions, chancre (painless ulcer)
  • diagnosis: darkfield microscopy (not preferred), blood test, indirect serology (RPR, FTA-ABS)
  • Transmission: sexual, congenital
    • congenital - in the womb
  • Treatment: penicillin
    • only primary and secondary stages can be treated with antibiotic
  • Stages of syphilis
    • Primary (chancre)
      • go away in a couple weeks
      • local infection
    • Secondary (rash)
      • flu-like symptoms
      • rash all over body, palms, soles of feet
      • systemic infection
    • Latent
    • Tertiary (gumma)
      • after many years
      • cardiovascular system - weakened blood vessel walls (aneurysm)
        • not seen often in US
      • neurological - seizures, dementia
      • tissue damage = gumma
        • on back of arm
        • improper immune function

Borrelia burgdorferi

  • causes Lyme disease
  • vector - deer ticks
    • takes 36-48 hrs to transmit disease
    • must get tick off ASAP
      • use forceps or credit card to slide underneath
  • Stages of Lyme disease
    • bulls eye rash (target symbol)
    • flu-like symptoms
    • meningitis (severe headache, stiff neck, fever)
    • irregular heartbeat
    • bell’s palsy (facial nerve)
    • arthritis (late stage)
  • Diagnosis: serology
  • Treatment: doxycycline
  • Prevention: wear long sleeves and stuff (but its hot so uhh)

Bacteroides

  • obligate anaerobe
    • reduced media (anaerobic jar)
  • gram negative bacilli in mouth and large intestine
  • cause deep tissue infection
  • transmission: endogenous
    • perforated bowels after vehicle accident
  • signs and symptoms: pus, pain, fever, putrid odor
  • diagnosis: aspirate sample(?) no swab bc organism will die
  • treatment: antibiotics, drain pus

Fusobacteria

  • Anaerobic gram negative bacilli
  • found in mouth
  • associated with dental diseases
  • “pointed ends” (spindle shape)
  • can also be found in other places for example
    • patient lose teeth from fist fight, bacteria can spread to lacerated hand that punched, can cause serious infection and amputation
  • transmission: endogenous
  • signs and symptoms: redness swelling pus fever
  • diagnosis: anaerobic jar
  • treatment: drain pus, antibiotic

Gram Positive Bacteria

Clostridium

  • obligate anaerobe
  • Clostridium botulinum
    • gram positive endospore forming bacilli
    • can be found in honey
    • causes Botulism
    • transmission
      • ingestion (extremely potent exotoxin)
      • neurotoxin blocks nerve impulse transmission
      • endospore → exotoxin
        • can be killed by commercial sterilization
      • most cases associated with home canning of green beans, corn, asparagus, potatoes
        • also some fermenting foods (unless acidic environment)
        • make sure no air pockets or bubbles (causes problems in autoclave)
        • pretty rare
      • infant botulism
        • most common cause
        • aka floppy baby syndrome (HELP)
    • signs and symptoms: flaccid paralysis, difficulty breathing, fatigue, blurred vision
      • no fever. why?
        • not an infection
      • can look similar to a stroke
      • can die in 10-15 days from respiratory failure
        • must treat asap bc recoverable
    • diagnosis
      • patient history (was there home canning?)
      • toxin assay on food / serum / stool
        • take sample from green beans, inject into mouse to see if it dies ☹️
    • treatment:
      • adults - antitoxin (antibodies)
      • infants - antitoxin and antibiotics (bc organism can overgrow their normal flora)
    • exotoxins can be also be used for botox
      • botox can be cosmetic, relieving migraines / headaches
      • do not get botox from questionable source
  • Clostridium perfringens
    • gram positive bacilli with endospores
    • found in contaminated soil
    • Gas Gangrene
    • transmission: penetrating / crushing wound
    • signs and symptoms:
      • discoloration of tissue, deep red skin, necrosis can cause dark purple / black color, pus spurting if u cut it, horrendous odor if progresses, crackling noise from build up of gas, severe pain, fever
      • can spread from foot to ankle, leg
      • exotoxin can cause kidney failure, shut down key organ systems
      • can be found in diabetics with no feeling in feet
      • abdominal if patient was shot / stabbed
    • diagnosis: gram stain
    • treatment: surgery, possible amputation, hyperbaric chamber,
      • less traditional: could use maggots to eat the dead tissue (help???)
  • Clostridium tetani
    • Tetanus (aka lock jaw)
      • neurotoxin (exotoxin exerts over-excitability)
    • transmission: step on rusty nail, penetrating / crushing wound, soil, burns, motorcycle / car accidents
      • can be seen in elderly who have not had updated vaccination
    • signs and symptoms: clenched jaw, paralysis, can break bones from force of contractions
    • prevention: vaccination with tetanus toxoid (DTP) and booster (dT)
      • first given at young age; every 10 yrs, recommended to get a booster
    • treatment: antitoxin or tetanus immune globulin, antibiotics, debridement
      • clean out wound
  • Clostridium difficile
    • aka C. diff or CDI
    • antibiotic associated diarrhea
      • mild diarrhea to colitis
      • patients with broad spectrum antibiotics can throw off balance of normal flora
      • exotoxin can damage mucosa of GI tract
      • commonly seen in healthcare settings
    • transmission:
      • part of normal flora but imbalance from antibiotics
      • hospital acquired infection (health provider contacts contaminated equipment)
      • cause is not antibiotics, it is caused by exotoxins produced by certain strains
    • signs and symptoms: abdominal pain, fever, liquid stool, damaged immune system
      • can be deadly, major problem in nursing homes, hospitals
    • diagnosis: toxin assay (feces)
    • treatment: antibiotics
      • non-traditional: fecal transplant

Bacillus anthracis

  • gram positive, endospore-forming facultative aerobic rod in soil
  • cause of Anthrax
  • transmission: zoonotic, can be aerosolized, from sheep wool
    • cutaneous, ingestion, pulmonary (breathe in, lung infection / pneumonia)
      • lung infection can be 99% fatal, can be 25% fatal in skin, 50% from ingestion
    • special case: biological terrorism
  • diagnosis: culture, serology, PCR
    • test atmosphere to detect anthrax
  • signs and symptoms
    • cutaneous: skin lesions, pustule, redness, soreness, fever, darkening of center over time (eschar)
    • pulmonary: acutely ill, bedridden, difficulty breathing
  • treatment: ciprofloxacin or doxycycline

Mycoplasma pneumoniae

  • wall-less, pleomorphic
  • causes primary atypical (walking) pneumonia
  • signs and symptoms: mild pneumonia
    • in teens and young adults
  • diagnosis: fried egg colony on media containing sterols
    • 0.1 - 0.24 micrometer (4x objective)
    • indirect serology
  • transmission: respiratory droplet
  • treatment: antibiotics

Learning Objectives

 

  • List at least six characteristics used to classify and identify bacteria according to Bergey’s.
  • **Give examples and characteristics of organisms in sections:  Spirochetes – Treponema pallidum, Borrelia burgdorferi; Helical/Vibriod – Vibrio cholera, Campylobacter jejuni, Helicobacter pylori; Aerobic GNR (Gram negative rods) – Pseudomonas aeruginosa, Legionella pneumophila; GNR – facultative – E. coli, Salmonella, S. typhi, Shigella, Proteus, Yersinia pestis; GNR – fastidious – Haemophilus influenzae, Bordetella pertussis; Gram Negative Diplococci – Neisseria gonorrhoeae, Neisseria meningitidis; Rickettsias and Chlamydias; Mycoplasmas; Gram positive rods (GPR) – Bacillus anthracis, Listeria monocytogenes, Corynebacterium diphtheriae, Mycobacterium tuberculosis, M. leprae; GPR – anaerobe – Clostridium; and Gram positive cocci – Micrococcus, Staphylococcus aureus, S. epidermidis, Streptococcus pyogenes, S. agalactiae, S.mutans (S. viridans), S. pneumoniae, and Enterococcus (to be covered during the course)