ICL 2.12: Corynebacterium & Actinomycetes Flashcards
what is the microbiology of corynebacterium?
gram +, pleomorphic
irregular shaped rods
do NOT form spores
non-motile
what are the characteristics of corynebacterium diphtheria?
highly toxic
noninvasive
damage from microbial products
is corynebacteria aerobic or anaerobic?
aerobic
or facultative anaerobe
what is the corynebacteria cell wall made of?
cell wall contains short-chain mycolic acids
but it’s not considered a true acid fast
how do corynebacteria grow?
grow in clumps
look like chinese letters
many contain metachromatic granules = inorganic polyphosphates that act as energy storage sites
they stain different from primary dye
what parts of the body do corynebacteria colonize?
normally colonize the skin, upper respiratory tract, GI tract, and urogenital tract
what are the 4 biotypes that C. diphtheriae is divided into?
- gravis
- mitis
- intermedium
- belfanti
which C. diphtheriae biotypes are often associated with diphtheria?
- gravis
- mitis
intermedium and belfanti are rarely associated with diphtheria
C. diphtheriae vingette
an unvaccinated 63-year-old man developed a sore throat on a week-long trip in Haiti
2 days after he returned home to Pennsylvania, he visited a local hospital with complaints of a sore throat and difficulties in swallowing; treated with antibiotics
patient returned two days later with chills, sweating, difficulty swallowing and breathing, nausea, and vomiting
he had diminished breath sounds in the left lung, and radiographs confirmed pulmonary infiltrates, as well as enlargement of the epiglottis
he went to the ICU and was treated with azithromycin, ceftriaxone, nafcillin, and steroids
over the next 4 days became hypotensive with a low-grade fever but cultures were negative for C. diphtheriae
by the eighth day of illness, a chest radiograph showed infiltrates in the right and left lung bases
white exudate consistent with C. diphtheriae pseudomembrane was observed over the supraglottic structures but cultures at this time remained negative for C. diphtheriae,
however, PCR testing for the exotoxin gene was positive
despite aggressive therapy, the patient continued to deteriorate, and on the 17th day of hospitalization developed cardiac complications and died
what race is inspired by a bacteria?
Iditarod Trail Sled Dog race!!
in 1925, 20 teams of mushers on dog sleds covered 674 miles in 6 days (127.5h) to prevent a diphtheria epidemic in alaska
that’s why there’s a statue of Balto in NY Central Park
which species can C. diphtheriae infect?
C. diphtheriae is a human specific pathogen
Immune individuals can serve as asymptomatic carriers
how is C. diphtheriae transmitted?
person-to-person transmission occurs through oral or respiratory droplets, close physical contact, and rarely by fomites
which populations are most likely to get respiratory diphtheria?
primarily a pediatric disease
however, in areas with high immunization rates, most cases are seen in the elderly population
which populations are most likely to get cutaneous diphtheria?
common in tropical countries
contact with discharge from skin lesions may play an important role in transmission of infection in these environments
which countries have endemic diphtheria?
- Africa
- South America
- Asia/South Pacific
- Middle East
- Europe
what’s the incubation period of diphtheria?
2-5 days
nasal diphtheria can be asymptomatic or mild
what is respiratory diphtheria?
gradual onset
characterized by mild fever (rarely >101° F), sore throat, difficulty in swallowing, malaise, loss of appetite, and hoarseness
which sites of the body are effected by respiratory diphtheria?
- mucous membrane of the upper respiratory tract = nose, pharynx, tonsils, larynx, and trachea
- skin = cutaneous diphtheria
- rarely, mucous membranes at other sites = eye, ear, vulva
what’s the hallmark of respiratory diphtheria?
the presence of a membrane over the mucous membrane of the tonsils, pharynx, larynx, or nares, and can extend into the trachea
that appears within 2–3 days of illness
membrane is firm, fleshy, grey, and adherent – bleeds following attempts to remove or dislodge
local complications such as life-threatening or fatal airway obstruction can result from extension of the membrane or dislodgement of a piece of the membrane into the larynx or trachea
what happens during severe respiratory diphtheria?
cervical lymphadenopathy and soft-tissue swelling in the neck give rise to a “bull-neck” appearance and obstructs airway
literally looks like a giant fat neck that is connected to the chin
what are some of the systemic complications associated with respiratory diphtheria?
- myocarditis
- polyneuropathies
often result from absorption of diphtheria toxin from the infection site and its subsequent dissemination to other organs away from the initial area of infection
*cutaneous and nasal diphtheria are localized and rarely associated with systemic toxicity
describe the diphtheria toxin
it’s the major virulence factor of C. diphteriae
diphtheria toxin is a binary toxin = classic A-B exotoxin that’s activated during secretion to form A-B proteins that remain attached via disulfide bonds
what does the B subunit of the diphtheria toxin do?
B subunit binds heparin-binding epidermal growth factor on local host cells
translocation (T) unit promotes insertion and internalization, then form pore to cytosol
what does the A subunit of the diphtheria toxin do?
the A (catalytic) subunit acts to inactivate elongation factor 2 (EF-2)
it terminates all protein synthesis and eventually kills tissue
a single molecule can inactivate all EF-2 in a cell
it’s irreversible once entering the cell
what are the effects of the diphtheria toxin on the body?
the diphtheria toxin is absorbed into the mucus membrane and can cause destruction of epithelium and inflammation
the necrotic epithelium becomes embedded with fibrin and red/white cells which results in grayish pseudomembrane that is the hallmark of diphtheria
C. diphtheriae can then invade and establish in the epithelial layers
here, it continues to produce toxin that is readily absorbed and travel to distant tissues
this can lead to damage of cardiac, nervous tissue, kidney, liver and adrenals – damage/hemmorrhage of these tissues can lead to death
what encodes the diphtheria toxin?
the diphtheria toxin is encoded by a lysogenic bacteriophage
bacteriophage = a virus that parasitizes a bacterium by infecting it and reproducing inside it
only strains infected by this phage can produce toxin and cause diphtheria
how do diagnose diphtheria?
initial treatment of diphtheria should be instituted based on clinical diagnosis rather than laboratory tests, since need to act quickly
so you base the initial treatment on epidemiologic and clinical clues like if they’re non-vaccinated and/or have visited endemic areas
even though C. diphtheriae has some characteristic growth and morphology features, they are not reliable for diagnosis
what media does diphtheria grow on?
- selective media include cysteine-tellurite blood agar = CTBA or Tinsdale; best to diagnose
- colistin-nalidixic agar = CNA; allows growth, but not diagnostic
Tellurite inhibits most respiratory tract and Gram-negative bacteria
C. diphtheriae reduce tellurite to form gray-black color on agar
what test is used to detect diphtheria toxin?
most important assay is for production of
diphtheria toxin or possess phage
- Elek test was used historically to detect toxin – see precipitate formed when toxin binds to antitoxin
PCR tests for presence of tox gene – Get false positive if toxin not expressed
how do you treat diphtheria?
the most important treatment for diphtheria is early administration of antitoxin – it’s most effective when administered within 3 days of disease development
but it can’t neutralize toxin that has already entered host cells
Equine diphtheria antitoxin (DAT) is the mainstay of treatment!! but you have to perform sensitivity test before administering horse serum to prevent serum sickness
you also need to make sure airway is clear since pseudomembrane can extend into the nasopharnyx or down the larnyx and swelling of lymphatics in neck can also occlude breathing
why do you give antibiotics during diphtheria infection? which antibiotic do you give?
- prevent further exotoxin production
- prevent carrier status
penicillin or erythromycin is DOC
is there a vaccine for diphtheria?
yup
there’s an extremely effective and safe vaccine is available for preventing diphtheria
what is the immunization schedule for diphtheria?
it’s actually a diphtheria and tetanus toxoids and accellular pertusis vaccine = DTaP
4 doses needed initially and then another final dose around 4-6 years old
what two types of diphtheria vaccines are there?
- DTaP
2. Tdap
what is the DTap vaccine?
combined vaccine against diphtheria, tetanus, and pertussis – pertussis component is acellular
children receive 4 doses at normal or “catch-up” schedule
the acellular vaccine is safer to administer and there’s fewer side-effects, such as local pain and redness, and/or fever
what’s the Tdap vaccine?
acronym for the collective vaccines preventing tetanus, diphtheris, and pertussus in adolescents and adults
differ from the childhood DTaP vaccines in that the concentration of diphtheria and pertussis toxoid has been reduced (lowercase d and p)
it’s the booster for “adolescents” and “adults” of all ages who have already received the initial vaccine series – given every 10 years
can be given more frequently in certain situations like a pertussis outbreak or if in the catch up program
FLASHCARD: microbiology, pathology, epidemiology, clinical, diagnosis, treatment of corynebacterium diphtheria
MICROBIOLOGY: Gram + pleomorphic rods, facultative anaerobe, non-motile, short-chain mycolic acid in cell wall, grow in clumps (Chinese letters), contain metachromatic granules
PATHOLOGY: Causes diphtheria. Start in nasal cavity. Gradual onset. Production of binary toxin encoded by bacteriophage that terminates protein synthesis and kills cells. Toxin causes formation of pseudomembrane in throat-associated tissues. Dead tissue provides environment for bacteria to grow and release more toxin, and may block breathing. Initial illness is mild with sore throat, but progresses to severe as toxin affects heart, nervous tissue, kidney, liver, and adrenals.
EPIDEMIOLOGY: Can live in throat without causing disease. Even vaccinated can be carrier, since antibodies are against toxin, not actual bacteria. Most cases seen in countries with poor vaccine coverage, but visitors can pick up and carry back to affect unvaccinated in developed countries.
CLINICAL: Initial illness is mild with sore throat. See formation of pseudomembrane in throat tissues 2-3 days after symptoms start, which can block breathing, but also a site for bacterial growth. As toxin spreads, see severe symptoms heart, nervous tissue, kidney, liver, and adrenals. Often fatal.
DIAGNOSIS: Initial treatment is quickly initiated based on clinical symptoms and epidemiology. Bacteria growth on cysteine-tellurite blood agar (CTBA or Tinsdale) is selective and best to diagnose. CAN agar allows growth, but not diagnostic. Can perform Elek test to detect toxin or use PCR to identify the presence of the toxin gene (but not proved toxin is being produced).
TREATMENT: Most important is early administration of antitoxin to neutralize effects. Also, must assess pseudomembrane to prevent patient choking. DTaP vaccine is very effective. Penicillin or erythromycin is DOC
what are the other corynebacterium species other than corynebacterium diphtheria?
- C. jeikeium
- C. urealyticum
- C. amycolatum
- C. ulcerans
- C. pseudotuberculosis
what is C. jeikeium?
opportunistic in immunocompromised patients – uncommon in healthy people
seen on skin of hospitalized patients (40%) regardless of immune status
VERY RESISTANT to antibiotics
what is C. urealyticum?
uncommon in healthy people
strong urease producer
forms struvite calculi or renal stones
risk factors = immunosuppression, genitourinary disorders, urologic procedure, antibiotic therapy
resistant to most antibiotics
what is C. amycolatum?
found on the skin but not oropharynx
opportunistic pathogen
most commonly isolated Corynebacterium in clinical specimens but often misidentified
resistant to many antibiotics
what is C. ulcerans?
can carry the diphtheria gene
disease indistinguishable from diphtheria
what is C. C. pseudotuberculosis?
can carry the diphtheria gene
rare cause of infection
what are arcanobacterium?
irregularly shaped gram + rods
both colonizer and pathogen
what diseases are associated with arcanobacterium?
- Pharyngitis (similar to Streptococcus)
- Wound infections (polymicrobic)
- Endocarditis, septicemia
how do you treat arcanobacterium treatment?
penicillin or erythromycin
what is brevibacterium?
skin colonizer
cheeselike odor in culture
causes malodorous feet in colonized people
septicemia, osteomyelitis, foreign body infections
labs = rod-shaped when young, coccoid when old
how do you treat bevibacterium infections?
resistant to beta lactams, clindamycin, ciprofloxacin
DOC = vancomycin, tetracycline, gentamicin
where in the body does rothia mucilaginosa colonize?
oropharynx and URT
what is the microbiology of rothia mucilaginosa?
gram positive coccoid
grows in clusters!
what is the pathology of rothia mucilaginosa?
very mucoid and sticky
adheres well to damaged heart valves and causes endocarditis
major cause of bacteremia, endophthalmitis, catheter-related infections, CNS infections, pneumonia, peritonitis, and septicemia
what type of antibiotics work well against rothia mucilaginosa?
unpredictable activity against antibiotics
susceptibility testing is necessary for effective treatment
what is the microbiology of tropheryma whippelii?
gram positive rods
difficult to gram stain
which bacteria is the causitive agent of whipple disease?
tropheryma whippelii
which cells does tropheryma whippelii infect?
infects macrophages and persist in host tissues
can not be grown outside of host cells!!
there are “foamy” macrophages that infiltrate many tissues
which population is susceptible to whipple disease?
men
48-54 years old
caucasian
what is whipple disease?
initially seen as GI disorder or arthritis = malabsorption, weight loss, diarrhea, joint pain
deposits of fatty acids in intestine and mesenteric lymphatic tissue
can also affect bone/joint disorders, neurological manifestations, and CV involvement
can also cause disease in other tissues like heart, lung, brain, joint, eye
what is the cause of the disease in whipple disease?
disease is caused by disordered immune response to persistent bacteria
there is increased incidence in certain MHC haplotypes
what is the prognosis for whipple disease?
untreated patients have a poor prognosis
it’s almost universally fatal after 1 year unless receive the correct diagnosis and therapy
how do you diagnose whipple disease?
diagnosis is usually by intestinal biopsy
- PAS-positive macrophage inclusions (not good indicator)
- IHC staining of bacteria in tissues
- PCR confirmation of T. whippelii DNA is best!
how do you treat whipple disease?
2 weeks ceftriaxone
1 year + oral trimethoprim-sulfamethoxazole
however, you often see relapses
what is the microbiology of propionibacterium?
small non-motile grampositive rods
grow in short chains or clumps
anaerobic
they ferment carbohydrates to make propionic acid
where is propionibacterium found on the body?
commonly found on skin, eyes, ear, oropharynx, and female genital tract
often seen as contaminants in blood cultures
what are the two most common isolated species of propionibacterium?
- P. acnes - acne vulgaris
2. P. propionicum = opportunistic infections
what is P. propionicum?
associated with endodontic abscesses and lacrimal canaliculitis (tear duct)
what is P. acnes?
acne vulgaris is a common skin disease
most common in adolescents on the face and upper neck
it’s associated with increase in male sex hormones but it’s seen in both males and females
it’s literally super gross cystic looking acne….
what is the pathology of P. acnes?
P. acnes can infect and block the sebaceous follicles
the bacteria thrive in this less aerobic conditions
there’s increased sebum and androgen production which causes leukocytes to migrate into the area and create an inflammatory lesion – this can lead to scaring
how do you manage the acne caused by P. acnes?
- acne is best managed by topical antibiotics in severe cases = erythromycin, clindimycin, tetracyclines
but we’re seeing increased antibiotic resistance so….
- another option is benzoyl peroxide which increases skin turnover and helps clear pores (doesn’t generate resistance)
- hormonal treatments can also be effective
on what media do propionibacteria grow?
they grow on most media
prefer low oxygen
takes 2-5 days to grow
what is the microbiology of actinomycetes?
aka nocardia
gram +
more on the side of nontoxic, invasive and damage from the immune system
what are actinomycetes?
a group of Gram-positive bacteria with filamentous growth patterns
Individual members of this group can be referred to as an “actinomycete”
These bacteria can include the genera Nocardia, Actinomyces, Streptomyces, etc.
what are actinomyces?
an individual genus within the “actinomycetes” group
is distinct from Nocardia and Streptomyces
what are the two types of actinomycetes?
- aerobic gram + filamentous rods = nocardia
2. anaerobic gram + filamentous rods = actinomyces
what are the characterisitcs of the actinomycetes aerobic gram + filamentous rods?
produce medium-chain mycolic acids in cell wall
partially acid-fast
beading pattern in Gram stain
ex. nocardia
what are the characterisitcs of the actinomycetes anaerobic gram + filamentous rods?
do NOT contain mycolic acids in cell wall
are NOT acid-fast
gram stain is uniform
ex. actinomyces
what is the important distinction between actinomyces subspecies and nocardia subspecies of actinomycetes?
- nocardia = aerobic gram + filamentous rods
nocardia spp. are typically found in the external environment like soils, water, dust or vegetation; not usually found on human skin
infections are usually EXOGENOUS
- actinomyces = anaerobic gram + filamentous rods
actinomyces spp. are normally found in mucous membranes of healthy individuals – especially common in URT
infections are usually ENDOGENOUS = a disease arising from an infectious agent already present in the body but previously asymptomatic
are nocardia aerobic or anaerobic?
all are aerobic gram-positive rods!!
filamentous growth – resemble fungal hyphae but has bacterial cell wall components
beaded gram staining (literally looks like beads)
what’s the cell wall structure of nocardia?
short mycolic acids and other waxes
stains weakly acid-fast which distinguishes it from actinomyces which are NOT acid fast and stain uniformly
in what lab media does nocardia grow?
grows on most lab media
takes 3-5 days
colonies range from white to orange
are nocardia infections exogenous or endogenous?
exogenous! aka come from the environment
which diseases can nocardia infections cause?
- pulmonary disease
- brain abscess
- primary cutaneous infections after trauma
- subcutaneous infections
what type of pulmonary disease does nocardia cause?
usually in immunocompromised patients or patients with existing lung disease
can spread hematogenously from lungs to infect other tissues (brain and skin)
how can nocardia infections cause brain abscess?
happens in 30% of patients with Nocardia infection
common in patients with T cell deficiencies like AIDS
can present initially as chronic meningitis
what are the subcutaneous infections that can result from nocardia infections?
mycetoma (feet)
cellulitis
what is mycetoma?
a subcutaneous infection that can result from nocardia infections
it’s a chronic subcutaneous infection often caused by anaerobic actinomycetes or fungi but can also be seen with nocardia
actinomycetes more common than fungi
usually in the food or lower leg
this is different from actinomycosis which is uaully in the cervical-facial, thoracic and pelvic sites
looks like super messed up warts on feet
what is the pathogenesis of nocardia?
once infection is established, can be quite invasive
the bacteria can avoid phagocyte killing by:
- producing cord factor = prevents phagosome-lysosome fusion
- prevent acidification of phagolysosome
- protected from toxic oxygen metabolites = catalase and superoxide dismutase
- avoid acid phosphatase-mediated killing by using host enzymes as nutrient source
how do you diagnose nocardia infections?
- staining of sputum, abscess, or CSF samples is the best and fastest method
filamentous cells will stain gram + but spotty
they will also stain weakly acid-fast (*actinomyces do NOT stain acid-fast)
ID at species level requires PCR analyses
on what media will nocardia grow?
will grow on most laboratory media
you’ll see raised and white-orange colonies
takes 3-5 days to grow
how do you treat nocardia infection?
antibiotic treatment should be 6 weeks or more for disseminated disease
treat local infection with trimethoprime-sulfamethoxazole
treat disseminated infections with combined drugs = Amikacin and a carbapenem (e.g. Imipenem)
what is the microbiology of actinomyces?
all are anaerobic Gram-positive rods
filamentous growth that resembles fungal hyphae but has bacterial cell wall components
gram stain appears normal
what is the cell wall strucure of actinomyces?
cell wall structure LACKS mycolic acids
is NOT acid-fast which is what distinguishes it from nocardia
on what media does actinomyces grow?
growth on laboratory media requires anaerobic conditions
can take 2 weeks or more for growth
colonies appear white to yellowish and have domed irregular surface that resembles the top of a molar tooth (literally)
you DON’T really see hyphael growth which also differs it from nocardia
sulfur granules morphology is not normally seen in plate-cultured isolates
where in the body do actinomyces colonize?
organisms normally colonize humans
upper respiratory, GI, and female genital tract
NOT normally found on skin
what causes the infection caused by actinomyces?
infections caused by endogenous organisms
poor oral hygiene or dental procedures
aspiration into lungs
GI surgery or trauma to bowels
abdominal infection or IUD can lead to pelvic infection
lung infection can spread to CNS
which actinomyces species are responsible for most infections?
- A. naeslundii
- A. radingae
- A. turicensis
- A. israelii
what is the range of diseases caused by actinomyces?
- cervicofacial
- thoracic
- abdomen and pelvis
- cutaneous/subcutaneous infections can occur
- brain abscesses can occur, but rare
what cervicofacial disease can actinomyces cause?
most common (50-70% of cases)
history of dental manipulation or trauma to the mouth, poor oral hygiene, dental caries, or periodontal disease
acute pyogenic disease or slowly evolving painless process
“lumpy jaw” in humans and animals
what thoracic disease can actinomyces cause?
15-20% of cases
pulmonary infiltrate or mass that can spread to involve the pleura, pericardium, and chest wall
what abdomen and pelvis disease can actinomyces cause?
10-20% of cases
history of recent or remote bowel surgery, or ingestion/insertion foreign body carrying bacteria
presents as slow growing tumor
what is Farmer’s lung?
is the most common form of hypersensitivity pneumonitis – reactivity to Actinomyces are the major cause of Farmer’s lung
inflammation of lungs due to breathing in a foreign substance like dust, fungus, molds etc.
initial exposure causes sensitization and subsequent exposures produces hypersensitivty reaction = type III hypersensitivity response
sensitized persons have antigen-specific Abs and C3b deposition is observed
the reaction produces large neutrophil and lymphocyte influx and large amounts of inflammatory cytokines and prolonged inflammation
what are the 3 categories of Farmer’s lung?
- Acute disease occurs after large exposure. there’s an onset of fever, chills, non-productive cough, chest tightness, dyspnea, headache, and malaise
- subacute disease manifests as chronic cough, dyspnea, anorexia, & weight loss – is insidious in onset and may occur over weeks to months
- chronic disease results from extended exposure to the antigen –> can lead to irreversible lung damage, severe dyspnea and dramatic weight loss
which bacteria causes farmer’s lung?
actinomyces
how do you diagnose actinomyces infection?
laboratory confirmation of actinomycosis is often difficult because all sample types can be contaminated by normal flora
also organisms recovered from abscess can be sparse or concentrated in sulfur granules
“Sulfur granule” cluster of bacteria should be crushed, stained, and assessed microscopically
thin branching rods along granule periphery will stain Gram+ –> actinomyces do not stain acid fast!
ID at species level requires biochemical/PCR analyses
under what conditions do actinomyces grow?
they are fastidious and grow slowly under anaerobic conditions
takes 2 weeks or more to grow
you’ll see raised white-yellow colonies
how do you treat actinomyces infections?
pathogenic actinomyces are susceptible to penicillin
treat for 6 months to 1 year
should also drain abscess or surgically debride involved tissues
they are resistant to metronidazole, aminoglycosides, aztreonam, co-trimoxazole (TMP-SMX), penicillinase-resistant penicillins (eg, methicillin, nafcillin, oxacillin, cloxacillin), and cephalexin
