ICL 2.3: Mycoplasma & Ureaplasma Flashcards
what bacteria classification are mycoplasma and ureaplasma?
they don’t have a cell wall!
so they can’t be classified as gram +/- or have a shape
what are the major species of mycoplasma?
- genitalium
- hominis
- pneumoniae
what are the major species of ureaplasma?
- urealyticum
how big are mycoplasma?
smallest known free-living organisms
one of the smallest genomes of self-replicating organisms
2 – 3× the size of a medium-sized virus like adenovirus but half the size of e. coli
do mycoplasma have a cell wall?
NO
they are bacteria with no peptidoglycan cell wall
**this means they won’t gram stain!!!
instead they have a triple cell membrane
what is the cell membrane of mycoplasma made of?
mycoplasma doesn’t have PG cell wall
instead they have triple cell membrane and no cell wall
the cell membrane contains sterols, including cholesterol
***it’s the only bacterial membrane that contains cholesterol!!!
do gram positive bacteria have a cell wall?
yes
they have 1 cell membrane plus a thick cell wall made of peptidoglycan
do gram negative bacteria have a cell wall?
yes
they have 2 cell membrane layers plus a thin cell wall made of peptidoglycan
where are mycoplasma most commonly found?
- plants
- animals
- insects
what are the two important genuses in the mycoplasmataceae family?
- mycoplasma
2. ureaplasma
which mycoplasmataceae species cause human disease?
- mycoplasma pneumoniae
- mycoplasma genitalium
- mycoplasma hominis
- ureaplasma urealyticum
- mycoplasma fermentans, mycoplasma penetrans
what is the disease and site associated with mycoplasma pneumoniae?
site = respiratory tract
disease:
1. primary atypical pneumonia
- tracheobronchitis
- pharyngitis
what is the disease and site associated with mycoplasma genitalium?
site = genitourinary tract
disease:
1. urethritis
- cervicitis
- endometritis
what is the disease and site associated with mycoplasma hominis?
site: 1. genitourinary tract
2. oropharynx
disease:
1. pelvic inflammatory disease
- neonatal infections
what is the disease and site associated with ureaplasma urealyticum?
site = genitourinary tract
disease:
1. urethritis
- neonatal infections
what is the disease and site associated with mycoplasma fermentans, mycoplasma penetrans?
site = genitourinary tract
disease = possible HIV cofactor
are mycoplasmidae aerobic or anaerobic?
fastidious aerobic bacteria
what do mycoplasmidae need for growth?
- exogenous lipids
- sterols
- vitamins
- AA
**special media (SP4) with serum is needed to grow them in a lab; isolation isn’t commonly performed
how can you grow mycoplasmidae in a lab?
identification/diagnosis often fails because they’re very difficult to grow
it takes 2 − 6 weeks before colonies are visible
how can you see mycoplasmidae?
they’re really hard to grow in the lab
instead they’re viewed by dissecting microscope
collonies have “freid egg” appearance
how long does it take to start seeing symptoms of mycoplasma infections?
prolonged (1-3 wk) asymptomatic colonization is typical
how does m. pneumoniae cause infections? what’s the pathology?
- M. pneumoniae attaches to the ciliated respiratory epithelial cells
there are unique attachment structures at one end of the mycoplasma called P1 adhesin
P1 adhesin binds to TLR2 on respiratory epithelial cells at the base of the cilia
- after attachment, ciliary movement is stopped
- mycoplasma secrete H2O2 and O2-
- CARDS toxin is released
- cilia desquamate and RBCs lyse
lack of cilia leads to impaired airway clearance
this leads to a vigourous host immune response with lymphocytes, antibody production and cutokines –> *immune response correlates with disease severity
what is P1 adhesin?
it’s a unique attachment structure at one end of the mycoplasma that binds to TLR2 on respiratory epithelial cells
P1 adhesin can undergo antigenic variation!
what is CARDS toxin?
it’s released by mycoplasma pneumoniae
it causes epithelial cell death in the respiratory tract
how is mycoplasma pneumoniae transmitted?
transmitted person-to-person via respiratory droplets
*1-3 week interval between diseases in individuals; 20% are asymptomatic
which populations are at risk for m. pneumoniae infections?
it’s transmitted person-to-person via respiratory droplets so infection spreads among families and closed populations
- military
- colleges*
- hospitals
- religious communities
what time of the year are m. pneumoniae infections common?
year round disease, but peak incidence in fall and winter
there are epidemics every 4-8 years; we don’t know why but maybe it’s because of P1 variation?
what is walking pneumonia?
caused by m. pneumoniae
aka atypical pneumonia
it’s pneumonia that fails to respond to penicillin/β-lactams and not easily isolated
what’s the most common cause of pneumonia in young adults?
m. pneumoniae
recent studies suggest that the highest rates of mycoplasma-induced pneumonia is in 15-20 yr olds and elderly (>60 yr old)
what is the incubation period of m. pneumoniae?
1-3 weeks
what are the symptoms m. pneumoniae infection?
after 1- 3 week incubation period, there is gradual onset of low-grade fever, malaise, headache, dry cough, little sputum
cough is severe, often painful, but non-productive
chills present but rigors are rare
sometimes patients are anemic
what would the PE of a an m. pneumoniae infection show?
PE often unremarkable
but chest X-ray reveals interstitial infiltrates, typically in lower lobe
microphage and neutrophil infiltrates with hemolysis!
do mycoplasma infections stimulate antibody production?
yes
Ab develop early in disease (7 - 10 days after infection) and persist for months
what are the types of antibodies generated during a m. pneumoniae infection?
- anti-mycoplasma antibodies
protective immunity generally develops after infection but immunity is not long lasting
- autoantibodies
during an m. pneumoniae infection there are IgM antibodies which binds to RBC surface antigen I causing agglutination and lysis at cold temperaturs = hemolytic anemia
there is also cold agglutinin antibody in 60% of patients
what is the Cold agglutinin test?
done to test for m. pneumoniae infections
- take 1 cc of blood in a glass tube with an anticoagulant (citrate) and place on ice for 3 minutes
- RBCs agglutinate on the sides of the tube due to IgM antibodies at 4 °C
it looks grainy
- rewarm the tube to 37°C and the agglutination disappears
the issue is that this test is positive in only 50% of mycoplasma infections
plus this result could also occur during influenza and adenovirus infections
what are the extrapulmonary complications involved with m. pneumoniae infections?
mycoplasma induces autoantibodies against important things in your body like RBCs etc.
- rash
- nonspecific myalgia and arthralgia
- CNS complications
- Raynaud’s phenomenon
- cardiac abnormalities
- Guillain-Barre syndrome
- asthma association
- COPD association
mycoplasma induces autoantibodies against what?
- RBCs
- Myosin
- Keratin
- Fibrinogen
- CNS components
- Kidney
- Smooth muscle
- Lung
how do m. pneumoniae cause rash?
damage to microvasculature and dermal layers
*Erythema multiforme (mild)
Stevens-Johnson syndrome (severe)
sometimes referred to as target lesions
rash happens in 25% of patients
what types of CNS complications does m. pneumoniae cause?
encephalitis most common in older adults and children
antibodies against myelin detected in 100% of M. pneumoniae patients with CNS complications
other CNS complications including cerebellar syndrome (ataxia), meningitis, confusion, cranial nerve palsies, etc.
0.1% of all patients; 6-7% of hospitalized patients
what is Raynaud’s phenomenon?
transient, reversible vasospasm of digit blood vessels upon exposure to cold
which cardiac abnormalities can be caused by m. pneumoniae?
1-8% of patients
- pericarditis
- myocarditis
- conduction defects
- heart failure
how is m. pneumonia associated with asthma?
bacteria is blieved to over-stimulate immune system
in what patient population are m. pneumoniae infections more severe?
disease is more severe in patients with hemoglobinopathies
ex. digital necrosis in sickle cell patients
how do diagnose m. pneumoniae infections?
- clinical findings
- serology
- cold agglutinin test (not very specific)
- culture of sputum (hard to obtain)
- antigen detection (P1 adhesin)
- PCR/DNA probes (not widely available)
what are the clinical findings of m. pneumoniae infections?
Fever, malaise, headache, dry cough, little sputum, chest pain
X-ray: lower lobe, diffuse infiltrates, one lobe, hilar adenopathy
what is the serology test you can do to diagnose m. pneumoniae?
you’re looking to see if there are antibodies against bacterial antigens
titer increase
what are the three classes of antibiotics used to treat m. pneumoniae?
- macrolides*
- tetracyclines
- quinolones
you can’t use any antibiotics that target the cell wall
which macrolide drugs are used to treat m. pneumoniae?
erythromycin
azithromycin
which tetracycline drugs are used to treat m. pneumoniae?
doxycycline
which quinolone drugs are used to treat m. pneumoniae?
levofloxacin
how do you treat m. pneumoniae?
with either macrolides, tetracyclines or quinolines
penicillins and cephalosporins inactive
treat for 7-10 days
antibiotic resistance is uncommon but there is some macrolide resistance recently
treating with antibiotics shortens course of illness and reduces transmission to others
how are m. homins/genitalium and ureaplasma transmitted?
vertical transmission: colonization in humans begins with passage through infected vaginal canal at birth
colonization decreases beyond age 2 and increases again after puberty
colonization rate increases with the number of sex partners
they all cause diseases in the genitourinary tract
what are the symptoms of m. homins/genitalium and ureaplasma infections?
in neonates, affects lower respiratory tract and CNS
in adults, diseases include non-gonococcal urethritis, post-abortion/postpartum fever, cervicitis, endometritis, pelvic inflammatory disease (PID), pyelonephritis (rare)
what is PID?
PID = pelvic inflammatory disease
*M. hominis accounts for approx. 10% of PID cases
usually more than one organism involved (polymicrobic infection)
which bacteria is most often the cause of PID?
m. hominis
PID = pelvic inflammatory disease
what is postabortal/postpartum fever?
self-limiting episode of fever without sepsis 24 hours after delivery or abortion (spontaneous or therapeutic)
m. hominis is recovered from blood cultures in 10% of cases
which bacteria causes non-gonoccal and non-chlamydial urethritis?
ureaplasma accounts for approx. 20% of cases
M. genitalium accounts for rare urethritis cases
how do you diagnose m. homins/genitalium and ureaplasma infections?
- clinical presentation
2. culture from blood/urine
how do you treat m. homins/genitalium and ureaplasma infections?
Ureaplasma: Use erythromycin; resistant to tetracyclines
M. hominis: Use clindamycin; resistant to erythromycin and tetracyclines
which bacteria is responsible for this?
A 21-year-old female developed fever, headache, and a gradually progressive dry cough. Over the next 2 days, her cough worsened, producing small amounts of clear sputum.
History: Previously healthy. Her 19-year-old brother had similar symptoms 2 weeks earlier.
Physical exam: Slightly pale appearance, mild pharyngeal erythema, chest exam was normal (no rales)
Lab results: WBCs 8,600/µL
CXR: bilateral patchy infiltrates
m. pneumoniae!
FLASHCARD: micro, epidemiology, clinical features, diagnosis and treatment for m. pneumoniae
MICRO: gram-indeterminant; no PG; 3 membranes; smallest bacterium; difficult to grow in lab; media needs lipids/sterols; fried-egg appearance; P1 adhesin with antigen variation
EPIDEMIOLOGY: Respiratory pathogen; < 20 yrs old; atypical or walking pneumonia; 2-3 week incubation after close contact with 1°
Clinical: Gradual onset of low-grade fever, malaise, headache, dry cough, patchy infiltrates on CXR
Diagnosis: clinical findings and serology; cold agglutinin
Treatment: Erythromycin or doxycycline
FLASHCARD: clinical features and treatment for m. hominis/genitalium
M. hominis
Clinical: PID, neonatal infections (respiratory or CNS), postpartum or postabortal fever
Treatment: clindamycin (erythromycin resistant)
FLASHCARD: clinical features and treatment of ureaplasma
Clinical: non-gonococcal urethritis, intrapartum infections
Treatment: erythromycin
