Bacteria Flashcards
Bacterial infection clinical features
- neutrophilia with left shift
- pyogenic, encapsulated bacterial infections: B-cell deficiency
anaerobic bacteria
anaerobes Can’t Breathe Fresh Air:
C - Clostridium
B - Bacteriodes
F - Fusobacterium
A - Actinomyces israelii
these bacteria lack catalase and/or superoxide dismutase, making them susceptible to oxidative damage
obligate intracellular bacteria
stay inside when it’s Really Chilly and Cold
R - Rickettsia
Ch - Chlamydia
Co - Coxiella
encapsulated bacteria
Please SHiNE my SKiS
P - Pseudomonas
S - Streptococcus pneumoniae
Hi - Haemophilus influenzae
N - Neisseria meningitidis
E - Escherichia coli
S - Salmonella
K - Klebsiella pneumoniae
S - group B Strep
capsules serve as an antiphagocytic virulence factor
Extended-spectrum beta-lactamase-producing bacteria (ESBL)
particularly gram-negative bacteria (e.g., Enterobacteriaceae such as Klebsiella spp., Escherichia coli)
Staph aureus lab classification
gram positive cocci
catalase +
coagulase +
mannitol-salt agar plate: golden yellow
Staph aureus virulence factors
coagulase: clumping factor that binds to fibrinogen
- parting of red sea
protein A: binds to IgG, protects from opsonization and phagocytosis
- A on Moses staff
exfoliative toxins A & B: causes scalded skin syndrome
- bald man with red skin
enterotoxins: cause food poisoning, rapid onset/termination
- nauseous woman on running camel with meats and creams
Toxic Shock Syndrome toxin (TSST-1): superantigen, binds to MHC II and t-cell receptor ==> release of cytokines, leakage of endothelia
- superman cape
staph aureus is found in…
nasopharynx mainly, also skin
staph aureus exotoxin-mediated diseases
gastroenteritis (food poisoning): acute symptoms result from intoxication; pre-formed toxin that is found in food
Toxic Shock syndrome: localized growth of S. aureus and release of toxin into blood
- patients with nasal packing or superabsorbent tampons
scalded skin syndrome (Ritter’s disease in newborns): result of exfoliatin toxin
impetigo: superficial infection of epidermis; localized SSSS (fluid-filled blisters)
folliculitis: infection around hair follicle
furuncles: boils; large collection of necrotic tissue
bacteriemia: bacteria in blood
acute endocarditis: S. aureus in blood adheres to heart tissues; aggressive form of endocarditis that leads to high mortality
- Strep viridans is 2nd major cause of endocarditis (sub-acute)
osteomyelitis: bone infection with severe pain and fever
septic arthiritis: invasion of the joint
Staph epidermis lab classification
gram positive cocci
catalase +
coagulase -
does NOT ferment mannitol
Staph epidermis important facts
- found on skin
- production of slime layer/biofilms enables colonization of catheters, shunts, artificial valves, artificial joints, etc.
- Novobiocin sensitive
- often seen in blood culture contaminations
- can cause bloodstream infections (sepsis)
plumber with belly button out, fixing slimy pipes
Staph saprophyticus lab classification
gram positive cocci
catalase +
coagulase -
does NOT ferment mannitol
staph saprophyticus important facts
- 2nd most common cause of UTIs in young, sexually active women
- Novobiocin resistant
sexy young woman with belly button covered
Strep pyogenes (Group A Strep) lab classification
gram positive cocci (pairs or chains)
catalase -
beta hemolytic, Lancefield group A
- red lightbulb
encapsulated, hyaluronic acid capsule
- Hot Apple pie in glass capsule
bacitracin sensitive
- basset hound
L-pyrrolidonyl arylamidase (PYR) sensitive
treat with Penicillin G
- baker holding pencil
Strep pyogenes (GAS) virulance factors
M protein: antiphagocytic factor, Class I associated with rheumatic fever <- antibodies against M protein cross-react with heart cells
- mitral pope hat with M on it
hyaluronic acid capsule: interferes with phagocytosis
- Hot Apple pie in glass capsule
Streptolysin S & O: hemolysins that make pores in host cell membranes
pyrogenic exotoxins: phage-encoded superantigens, cross-link MHC class II to T-cell receptors ==> cytokine storm ==> toxic shock like syndrome
- baker with superman cape
Strep pyogenes (GAS) pyogenic/supperative (pus-producing) diseases
pharyngitis: white spots on back of throat, gray furry tongue, swollen uvula
- red handkerchief around baker’s throat
impetigo/pyoderma: superficial skin infection, blisters
- honey crusted pie
erysipelas: infection of dermis, sharply demarcated edge
- red mittens on baker
cellulitis: deeper dermal infection, not sharply demarcated
necrotizing fascitis: flesh-eating disease, often accompanied by Streptococcal toxic shock syndrome (STSS) due to pyrogenic exotoxins
- burnt gingerbread man
- superman cape with bolt
sepsis
Strep pyogenes (GAS) toxin-mediated diseases
scarlet fever: diffuse erythematous rash beginning on chest and spreading to extremities, strawberry tongue
- baker eating strawberry, red gingerman
Streptococcal toxic shock syndrome (STSS): phage-encoded superantigens, cross-link MHC class II to T-cell receptors ==> cytokine storm ==> toxic shock like syndrome
- superman cape with bolt
Strep pyogenes (GAS) sequelae diseases
acute rheumatic fever/rheumatic fever (ARF/RF): following pharyngeal infection ONLY, antibodies raised against M-protein cross-react with heart tissue; own cells look like they have M-proteins (molecular mimicry)
- mitral hat on baker with M on it
- JONES cupcakes for symptoms: Joints, Nodules, Erythema marginatum, Sydenhams chorea
acute glomerulonephritis (AGN): follows pharyngeal and skin infections; type III hypersensitivity in glomeruli due to antibody-antigen complexes
Strep agalactiae (Group B Strep) lab classification
gram positive cocci (pairs or chains)
catalase -
beta hemolytic, Lancefield group B
- red lightbulbs in space
produces CAMP factor, which enlarges zone of hemolysis when plated with S. aureus
- camping tents
- arrow
bacitracin resistant
- basset hound with capsule/helmet
penicillin sensitive
- pencils for landing legs on spaceship (penicillin given to moms intrapartum at least 4hr before delivery to prevent GBS)
polysaccharide capsule
Strep agalactiae (GBS) diseases
largest cause of neonatal meningitis, sepsis, pneumonia
- GBS colonizes lower GI tract and genitourinary tract
- colonized mothers at risk for post-partum disease
- mothers screened at 35wk
- colonization can occur in utero, at birth, or during first few weeks of life
- neurologic complications are common
baby wearing meningitis helmet, in red suit (sepsis), coughing; baby coming out of tunnel (vaginal canal)
Strep pneumoniae lab classification
gram positive cocci (lancet shaped diplococci)
- double lance
catalase -
alpha hemolytic
- alpha knight tournament
polysaccharide capsule is main virulence factor
- armor
IgA protease is another virulence factor
bile soluble
- mud on horse’s legs
optochin sensitive
- knight’s chin is exposed
Strep pneumoniae diseases
pneumonia: bacteria multiply in alveolar spaces
otitis media: middle ear infections in young children
meningitis: young children and adults
bacteremia: bacteria in blood; endocarditis may occur
Strep pneumoniae treatment and vaccines
GBS is sensitive to penicillin, but start with broad spectrum antibiotic until GBS diagnosis confirmed
polysaccharide vaccines (PSV) + conjugate vaccines (PCV) available, both now replaced by PCV20
Strep viridans lab classification
gram positive cocci
catalase -
alpha hemolytic
optochin resistant
- jester’s mask covers chin
bile resistant
- jester’s shoes on donkey
Strep viridans important facts
- commensal species found in oral cavity (also GI/GU tracts)
- dental caries
- dental manipulations can send bacteria into bloodstream ==> repeated buildup ==> sub-acute endocarditis
optochin resistant:
“viridans strep live in the mouth because they are not afraid of-the-chin”
Enterococcus lab classification
E. faecalis and E. faecium
gram positive cocci
catalase -
gamma hemolytic
grow in 6.5% NaCl and bile
- resist the 6.5% N.CA sign
- jester’s boots
resistant to most antibiotics, including vancomycin (source of vancomycin resistance in S. aureus)
- protestors resisting arrest, resisting getting put into van
Enterococcus diseases
one of the most common nosocomial (hospital origin) infections
- UTIs
- wound infections
- endocarditis
- bacteremia and sepsis following IV catheters
Streptococcus bovis (Group D Strep)
non-Enterococcal Group D Strep, AKA Strep gallolyticus
- gamma hemolysis (no hemolysis)
- grows in bile, but NOT 6.5% NaCl
- colonizes gut
- colon cancer patients: bacteremia, sub-acute endocarditis
“Bovis in the blood = cancer in the colon”
Bacillus anthracis classification
- gram positive rod, spore-forming; “boxcar” like chains
- only bacteria with polypeptide capsule (buff Vikings), made of D-glutamate
- toxin has 3 protein subunits: Protective Antigen (PA), Edema Factor (EF), Lethal Factor (LF)
PA: needed for binding and cell entry
EF: mimics adenylate cyclase ==> increased cAMP
LF: protease that inhibits cell-signaling ==> apoptosis
Bacillus anthracis: inhaled, cutaneous, GI transmission
bioterrorism or wool-sorting disease (from animal contact)
Inhaled:
- clinical manifestations: fever, chills, sweats, GI symptoms, headache, malaise, NO CORYZA (runny nose)
- widened mediastinum
Cutaneous:
- eschar: dry, dark dead skin
GI:
- nausea, vomiting, fevers 1-5 days after eating infected meat
Viking standing in middle of burnt fire
Bacillus anthracis treatment
doxycycline, fluoroquinolone (ciprofloxacin), amoxicillin
flower and bicycle wheel on Viking ship
Bacillus cereus
- gram-positive rod
- spore-forming, motile
- heat-stable enterotoxin (cereulide): nausea and vomiting within hours of eating (reheated rice)
- heat-labile enterotoxin: diarrhea, symptoms arrive a little later (6-8hr)
Viking eating rice and throwing up
Clostridium classification
- gram positive rod
- spore-forming
- obligate anaerobe
Clostridium tetani
- nervous system disorder characterized by muscle spasms due to blocking of inhibitory transmitter release (continuous stimulation)
- glycine-producing Renshaw cells preferentially targeted
- lockjaw (rismus): intense, painful spasms of masseter muscles
- opisthotonus: spasm of spinal extensors
Clostridium tetani treatment and vaccines
- halt toxin production, neutralize unbound toxin, airway protection, control muscle spasms
- antimicrobials play minor role
- active immunity through vaccination only: 3 doses of tetanus and diphtheria toxoid immediately upon diagnosis
Clostridium botulinum
anaerobic heat-resistant spores: germinate in canned foods
- robots made of cans
neurotoxin: most potent known bacterial toxin ==> neuroparalytic syndrome affecting peripheral nervous system only (cannot cross blood-brain barrier), descending paralysis as toxin blocks release of ACh from vesicles (stimulation blocked)
- robots struggling to keep upright
after ingesting raw honey, babies lack gut flora that can outcompete C. botulinum ==> floppy baby syndrome
- robot pouring honey all over baby robot
iatrogenic (within healthcare setting) botulsim: unlicensed Botox
Clostridium botulinum treatment
- prompt intubation with mechanical ventilation
- antitoxin: equine serum heptavalent botulism antitoxin or human-derived botulism immune globulin
Clostridium perfringens
found in soil
- knocked over dirt
alpha-toxin: phospholipase (lecithinase) that breaks down tissue and cell membranes ==> myonecrosis (gas gangrene: gas produced under tissue and has cracking sound on palpation)
- gas leaking out of motorcycle
- alpha flag
exotoxin: heat-resistant spores in food reproduce in gut ==> release exotoxin ==> slow onset diarrheal illness
- slow sign
IV penicillin G
- woman holding pencil
“perfringens perforates a gangrenous leg”
Corynebacterium classification
gram positive rod
Corynebacterium diphtheriae classification
- gram-positive, non-spore forming
- club-shaped bacteria
- mycolic acid on cell wall
- NOT acid fast
- cystine-tellurite agar (lipid supplemented)
Corynebacterium diphtheria pathogenesis
diphtheria toxin: inhibits protein synthesis via ADP-ribosylation of elongation factor (EF-2) ==> cell death
- man playing accordian wearing bow tie
pseudomembrane: fibrinous exudate found in oral pharynx that contains dead tissue, inflammatory cells, bacteria
- kids eating grey cotton candy wrapped in plastic wrap
airway obstruction, lymphopathy: thickening of the neck
- thick bull’s neck
myocarditis: arrhythmias, heart block; lethal
- heart-shaped cape
peripheral and cranial neuropathies: damaged myelin sheaths; top-down symptoms that usually resolve
- sausage-eating man
Corynebacterium diphtheria treatment and vaccines
treatment: penicillin
- score keeper with pencil
natural infection doesn’t result in protective immunity; recovered patients still need vaccine (DTaP, toxoid vaccine)
Listeria classification
- gram positive rod
- only gram(+) to produce lipopolysaccharide (LPS) endotoxin <- fat Santa
- non-branching
- individual rods or short chains
- motile at cold temperatures: tumbling motility
- intracellularly, uses actin polymerization to spread from cell to cell (rocket tails) without having to go outside cells
Listeria monocytonegenes pathogenesis
transmitted in food, even refrigerated food like milk and cheese
- Santa eating milk and cheese
high risk: neonates, elderly, pregnancy, those with severe defects in cell-mediated immunity
- pregnant mom and baby
health adults: febrile diarrhea
immunocompromised/elderly: bacteremia with or without CNS infection
pregnant women: can result in spontaneous abortion
neonates: meningitis
Actinomyces classification
- gram positive rods
- branching filaments (tree branches)
- obligate anaerobes
- NOT acid fast
- part of normal oral flora (also GI, GU tracts)
Actinomyces israelli
infection associated with dental caries/extractions or gingival disease ==> cervical facies atinomyces infection
- soldier with bandage around head
does NOT respect anatomic borders, so can form sinus tracts (channel from source to skin)
- drain with water
yellow sulfur granules composed of bacteria, tissue debris, neutrophils
- yellow rocks on ground
treatment: penicillin, erythromycin, clindamycin
- solder writing with pencil
Nocardia classification
- gram positive rod
- branching filaments
- cell wall has mycolic acid (similar to Mycobacteria, but a lot less)
- weakly acid fast staining (Ziehl-Neelsen stain + carbol fuchsin), decolorized by hydrochloric acid
- catalase positive
- exogenous flora found in soil
cowboys playing cards
Nocardia asteroides pathology
risk factor: defects in cell-mediated immunity (transplant, HIV/AIDS, underlying lung disease)
- cowboy leaning on cane
clinical symptoms:
cavitary lung lesions (cough, SOB); pneumonia
- bullet hitting cowboy’s chest and denting the star
brain abscess (headache, fever, focal neurologic deficits)
- bullet shooting a hole through his hat
cutaneous indurated (hard) lesions and inflammation <- immunocompromised people can get cutaneous disease alone following trauma
- cowprint on cowboy with redness
Nocardia treatment
trimethoprim-sulfamethoxazole
- eggs on the counter: treat with sulfonamides
prolonged therapy: 12mo
almost all gram-negative bacteria have what endotoxin on their cell membranes
lipopolysaccharide (LPS)
Neisseria spp. classification
gram-negative diplococci, often intracellular
- red theme
- double handcuffs
aerobic, oxidase positive
- blue ring
carbohydrate utilization pattern:
N. meningitidis = glucose(+) and maltose(+)
N. gonnorrhoeae = glucose(+) and maltose(-)
- “MeninGococci ferment Maltose and Glucose”
grows on chocolate agar, inhibited on blood agar
- detective holding chocolate bar
Thayer-Martin agar: selective agar with vancomycin, polymixin, nystatin
- Vice city Private Nvestigator (VPN)
Noir series
Neisseria meningitidis
- encapsulated; capsule is primary virulence factor
- primarily colonizes nasopharynx
- easily spread in areas with a lot of people via respiratory droplets
- 10% mortality even in healthy patients
- risk factors: complement deficiency (MAC deficiency), asplenia (lack of spleen, sickle cell disease), history of respiratory tract infections, preterm birth
- wide range of illness: transient fever, pneumonia, meningitis, meningococcemia, septic shock, disseminated intravascular coagulation (DIC)
Meningococcal meningitis: headache, nuchal rigidity, photophobia, petechial rash, hemorrhage on mucous membranes of soft palate/conjunctiva
Shock & DIC: tachycardia, hypotension, cold extremeties, adrenal infarction, bleeding occurring from skin/mucous membranes/GI tract/respiratory tract
college dorm murder scene
Neisseria meningitidis treatment
Drug of choice is ceftriaxone, can also use IV penicillin G
- firefighter with 3 axes
patients placed in droplet isolation, continued for 24hr after antibiotics
close contacts will need rifampin
- police with rifle holding back crowd
There IS a vaccine for N. meningitidis
mortality is still high despite treatment
Neisseria gonorrheae
- not encapsulated
- gonococcal infection can be localized (urethritis), localized invasive (pelvic inflammatory disease), or systemic (disseminated gonococcal infection)
- pelvic inflammatory disease: inflammatory diseases of upper female genital tract (endometritis, salpingitis, etc)
- diganose with PCR/NAT
Treatment: ceftriaxone
- statue with 3 axes
Chlamydia classification
3 species pathogenic to humans:
1) Chlamydia trachomatis
2) Chlamydophila psittaci
3) Chlamydophila pneumoniae
- obligate intracellular organisms (unable to make their own ATP)
- lack peptidoglycan layer, lacks muramic acid
- cannot grow on artificial media so PCR/NAT is needed for diagnosis
- 2 developmental phases: elementary body (infectious form), reticulate body (replicative, non-infectious form)
Elementary body: “Enfectious and Enters cell via Endocytosis, transforms into reticulate body”; extracellular
Reticulate body: “Replicates in cell by fission; Reorganizes into elementary bodies”; intracellular
Chlamydia trachomatis biovars (biologic variants)
Trachoma biovars
- A, B, Ba, C serovar
- D-K serovar: Urogenital tract disease (urethritis)
LGV biovars
- L1, L2, L3 serovar: lymphogranuloma venereum
affects mucous membranes: urethra, endocervix, endometrium fallopian tubes, anorectum, respiratory tract, conjunctivae
clinical manifestations due to direct destruction of cells during replication, post-inflammatory cytokine response
infection does not confer long-lasting immunity due to antigenic variation
Chlamydia trachomatis: lymphogranuloma venereum (LGV)
- caused by LGV serovars L1, L2, L3
- organisms gain access through small abrasions/lacerations
- primary lesion: small, painless vesicular lesion that ulcerates; lesion heals in 3-5 days
- second stage: 1-4wk after primary lesion; enlarged lymph nodes become painful buboes that can rupture and drain
Treatment: doxycycline (21 days)
- erythromycin in pregnant women
Chlamydia trachomatis: ocular trachoma
- caused by serovars A, B, Ba, C
- leading cause of preventable blindness, commonly occurs in children
- chronic/repeated infection ==> inflammation and follicle formation of entire conjuctiva (turning in of eyelids, scarring, ulceration, blood vessel formation in cornea) ==> blindness
Chlamydia trachomatis: urogenital tract disease
- most caused by serovars D-K
- most common STD reported in USA
- dual infection with Neisseria gonorrhea is common
- pelvic inflammatory disease, cervicitis, endometritis, urethritis
- reactive arthritis: triggered by urethritis, conjunctivitis, polyarthritis
Treatment: doxycycline (7 days)
- bicycle wheel as wheel of ship
Chlamydia psittaci
causes psittacocis (“parrot fever”) and atypical pneumonia
Chlamydia pneumoniae
causes atypical pneumonia
Haemophilus influenzae classification
gram-negative coccobacillus
- pink candy machine shaped like a bullet
chocolate agar: Factor V (NAD+) and X (hematin/hemin), which are found in hemolyzed blood
- chocolate shop, 5 and 10 cent signs
- “hemophilic” influenzae
- can also be grown with Staph aureus, which is beta hemolytic and promotes release of factor V
virulence factors:
capsular polysaccharide
IgA protease: cleaves mucosal IgA
Haemophilus influenzae diseases and treatment
epiglottis (H. influenzae type b)
- coughing child with red tongue
non-typeable (no capsule):
otitis media
- child sticking fingers in his ears
pneumonia
- child coughing + aerosol spray
Treatment: ceftriaxone and rifampin for close contacts
- coughing boy has 3 axes
- unaffected boy has rifle
Vaccine: capsular polysaccharide conjugated to a protein (only for type b)
Pseudomonas classification
- encapsulated gram-negative rod
- obligate aerobe
- oxidase positive (blue ring)
- non-lactose fermenting
- thrives in hot environments
- blue-green culture
- pyocyanin: blue-green pigment that acts as a virulence factor, helps with biofilm formation, generates ROS
- pyoveridine: blue-green pigment that is an iron-chelating molecule, acts as a virulence factor, helps with biofilm formation
- exotoxin A: inactivates elongation factor 2 (EF-2) ==> inhibition of protein synthesis ==> cell death (accordion player)
- endotoxin: fever and shock
- phospholipase C: helps degrade cell membranes
- cystic fibrosis
Pseudomonas infections
- nosocomial pneumonia and UTI: hospital infections (nurse coughing, chamber pot)
- bacteremia in hospitalized patients
- chronic pnuemonias in patients with cystic fibrosis
- skin infections: burn wound infections, hot tub folliculitis
Enterobacterales species
- Escherichia coli: UTIs
- Klebsiella spp.: pneumonia
Escherichia coli
- gram-negative
- fast lactose-fermenter
- MacConkey agar (contains lactose); E. coli grows pink
- green sheen on Eosin-methylene blue (EMB) agar <- stains for gram(-)
- facultative anaerobic, oxidase negative
- encapsulated
- P Fimbriae (aka P pili): adhere to urogenital epithelium
- K capsule: capsular polysaccharide that inhibits phagocytosis
- Lipid A and O-antigen of lipopolysaccharide (LPS) endotoxin: shock and fever
Klebsiella pneumoniae
- gram-negative
- fast lactose-fermenter
- grows pink on MacConkey agar; thick and mucoid
- natural flora of GI tract
- capsular polysaccharide: thick capsule reflected in very mucoid colonies seen on agar
- can cause pneumonia
Mycobacteria species
- aerobic
- weakly gram-positive bacilli
- acid-fast (Ziehl-Neelsen stain)
- gold standard is culture: solid (Lowenstein Jensen agar) and liquid media, but takes 6-8wk to culture
- mycolic acid cell wall (hydrophobic, lipid rich)
- patient’s cell-mediated immunity is key to prognosis: TH1 response, activation of CD4+ T-cells, secretion of INF-y, macrophage/CD8+ cell response
Mycobacterium tuberculosis
virulence factors:
cord factor (trehalose dimycolate) and mycolic acid glycolipids elicit granuloma formation by increasing TNF-a (activates other alveolar macrophages) ==> CD4+ T-cells come help, forming collar around macrophages ==> sulfatides prevent phagolysosome fusion ==> ceseating granuloma formation
- cowboy lasso
inhalation of M. tuberculosis into lungs results in latent infection and disease onset many years later (reactivation)
- latent TB: infection without any symptoms = 90% of pts
- reactivation disease: cavitary lung lesion in upper portion of lung
clinical findings:
- fear, weight loss, anorexia, hemoptysis (coughing up blood), drenching night sweats
Mycobacterium tuberculosis treatment, hospital procedures
airborne isolation: N95 mask
- suspected TB: at lest 3 consecutive sputum specimens collected in 8-24hr intervals
PPD test: purified protein derivative skin test
- false negatives due to immunosuppressive drugs or immunocompromised pts
- false positives due to hx of BCG vaccine
Quantiferon TB Gold In-Tube test/Interferon Gamma Release Assay (IGRA): single blood test, no cross-reactivity with other Mycobacteria
- antigen provided in tube ==> pt’s antigen-presenting cells process antigen ==> APC presents to antigen specific T-cell ==> T-cell produces IFN-y
- detection based on IFN-y amounts
- only tests for latent TB infection, does NOT say if pt has active infection
Bacillus Calmette Guerin (BCG) vaccine:
- attenuated M. bovis
- used in countries where TB is endemic
Treatment:
4 drugs for 2 months, then 2 drugs for 4 months
- RIPE: Rifampin (RIF), Isoniazid (INH), Pyrazinamide (PZA), Ethambutol (EMB)
Mycobacterium leprae
- affects the skin, peripheral nerves, upper respiratory tract mucosa, eyes
- consider in patients with cutaneous lesions + enlarged nerves/sensory loss
- not very transmissible
- inhalation of M. leprae from respiratory drops
- armadillo/Mangabey monkey contact
- diagnosis: skin biopsy of skin lesion shows acid-fast bacilli (AFB); PCR
Spectrum of leprosy: influenced largely by patient’s immune status
- high cell mediated immunity = tuberculoid disease, paucibacillary leprosy (low AFB load), Th1 response
- low cell mediated immunity = lepromatous leprosy, multibacillary leprosy (high AFB load), Th2 response (inappropriate)
Mycobacterium avium complex (MAC)
M. avium + M. intracellulare
- asymptomatic colonization, leads to enlarged lymph nodes (lymphadenitis)
- disseminated disease in AIDS patients: most common mycobacterial disease in USA, diagnosis made with blood culture (CD4 < 50cells/mm3); chronic condition (diarrhea, fevers, anemia)
- AIDS-defining illness
- pulmonary disease in immunocompetent patients
Mycobacterium marinum
- tuberculosis-like symptoms in fish
- cutaneous lesions
major spirochetes
- Treponema pallidum (syphilis)
- Borrelia (Lyme disease)
- Leptospira (leptospirosis, Weil disease)
technically gram-negative, but very weak gram-negative stain and not truly considered gram-negative organisms
Borrelia
Lyme disease from hard ticks, ixodes
- early Lyme: bulls-eye skin lesion develops at tick bite, called Erythema Chronicum Migrans (ECM)
- late disease: neurologic signs (meningitis, Bell’s palsy), monoarticular arthritis, cardiac
Also causes relapsing fever from body louse or soft ticks; relapsing due to antigenic variation
Treatment: doxycycline
- treat if high clinical suspicion
spiraly wood shavings from arrow
Leptospira
- infection via urine-contaminated water and animal exposure (rodents, dogs, domestic/wild animals)
- severe headaches, flu-like illness, aseptic meningitis, scleral icterus (yellow sclera)
- Weil’s disease (severe disease): vascular collapse, thrombocytopenia, hemorrhage, liver/kidney failure
Treatment: penicillin or doxycycline
coiled ankle strap on surfboard; yellow sea (pee)
Treponema pallidum
Syphilis:
Primary syphilis:
- painless chancre
- diagnose with dark-field microscopy
Secondary syphilis:
- disseminated disease: fever, lymphadenopathy (swollen lymphs), maculopapular rash, condyloma lata (painless wart-like lesions on genitals)
- diagnose with nontrepenomal / treponemal tests
Tertiary syphilis:
- gummas (chronic granulomas of skin), aortitis, neurosyphilis
- diagnose with CSF examination (lumbar puncture)
Latent syphilis:
- no clinical symptoms
- diagnose with CSF examination
Congenital syphilis:
- early: hepatomegaly, nasal discharge (snuffles), skeletal abnormalities, rash, lymphadenopathy
- late: saddle nose, sensorineural hearing loss, Hutchinson’s teeth/incisors, mulberry molars, saber shins
Treatment: penicillin G
spiral galaxy at the Pallidum observatory
Treponema pallidum testing
Dark-field microscopy:
- only for primary syphilis dx
Non-treponemal (non-specific) testing:
- detects anti-cardiolipin antibodies
- used to monitor response to therapy
- can be falsely negative early or late in disease
- false positive with other conditions: (pregnancy, HIV, autoimmune disease, recent immunization, acute febrile illness)
- VDRL
- RPR
Treponemal (specific) testing:
- detect antibodies that specifically target T pallidum
- very specific, positive test remains for life
- TP-EIA
- FTA
- TP-PA
- MHA-TP
Major zoonotics
Rickettsial diseases:
- Rickettsia rickettsii (Rocky Mountain Spotted Fever)
- Rickettsia akari (pox) from mites
- Rickettsia typhi (typhus) from fleas
- Rickettsia prowazekii (typhus) from body lice
- Ehrlichia chaffeensis (ehrlichiosis)
- Anaplasma phagocytophilum (anaplasmosis)
- Coxiella burnetti (Q fever)
Other:
- Yersinia pestis (bubonic plague)
- Bartonella spp (cat-scratch disease)
- Bartonella quintana / B. henselae (regional lymphadenopathy)
- Francisella tularensis (tularemia)
Rikettsia rickettsi
Rocky Mountain spotted fever
- dog tick and wood tick
- fever, severe headache, myalgias, rashes on hands/wrists/feet that move to trunk
- severe: pulmonary and renal failure, cardiac and neurologic damage
- 10-25% fatality without treatment
Treatment: doxycycline
Anaplasmataceae diseases
Ehrlichia chaffeensis
- Lone star tick
- ehrlichiosis: YES rash, leukopenia, high fever, headache
- morulae (berry-like inclusions in cytoplasm) in monocytes
- Central-South USA
Anaplasma phagocytophilum
- Ixodes tick
- high fever, headache, NO rash
- morulae in granulocytes
Treatment: doxycycline
Coxiella burnetii
Q fever
- infected via aerosols from cattle/sheep amniotic fluids or contaminated milk
- replicates within vacuoles
- most cases are asymptomatic
- symptoms: mild, flu-like symptoms OR pneumonia
- Chronic Q fever: subacute endocarditis in those with underlying valvular heart disease or immunosuppression
Treatment: doxycycline
Yersinia pestis
Bubonic plague
- Western US with prairie dogs, squireels, rodents; transmitted through fleas
- fevers, headaches, myalgias, painful swollen lymph nodes (buboes)
- diagnosis: bacteria stain bipolar (safety pin appearance)
Bartonella spp
Bartonella quintana
- non-zoonotic pathogen
- transmitted by humans
Bartonella henselae
- zoonotic
- cat-scratch disease
- regional lymphadenopathy
Francisella tularensis
Tularemia
- rabbits, ticks
- ulceroglandular: fever, single ulcer with central eschar at site of tick bite
Treatment: streptomycin
