- Mycoplasma and Ureaplasma

- Rickettsia

Mycoplasma and Ureaplasma

Family: Mycoplasmataceae

• Genus: Mycoplasma

– Species: M. pneumoniae

– Species: M. hominis

– Species: M. genitalium

• Genus: Ureaplasma

– Species: U. urealyticum

Morphology and Physiology

• Smallest free-living bacteria (0.2 - 0.8 µm)

– Require complex media for growth, PPL4.

• Facultative anaerobes

– Except M. pneumoniae - strict aerobe

• Lack a cell wall?

• Part of Normal flora

• Cytoplasmic and cell membrane rich in

cholesterol and GLYCOLIPIDS

• P1 antigen? Binds to RBCs I antigen

• Fried egg” colonies

“Fried Egg” Colonies of Mycoplasmas

Pathogenesis - Mycoplasma

• Adherence

– P1 pili (M. pneumoniae)

– Movement of cilia ceases

– Clearance mechanism stops

resulting in cough

– glycolipids

• Glycolipids: Brain cells cross

antigenicity

Organism Disease

M. pneumoniae Upper respiratory tract disease,tracheobronchitis, atypicalpneumonia, (chronic asthma??)

M. hominis Pyleonephritis, pelvicinflammatory disease,postpartum fever

M. genitalium Nongonococcal urethritis

U. urealyticum Nongonococcal urethritis,(pneumonia and chronic lungdisease in premature infants??)

Diseases Caused by Mycoplasma

N.B. Other organisms infect humans but their disease association is not known.

Mycoplasma pneumoniae

• Tracheobronchitis

• Atypical pneumonia (walking pneumonia)

Epidemiology - M. pneumoniae

• Occurs worldwide

• No seasonal

variation

– Proportionally

higher in summer

and fall

Clinical Syndrome - M. pneumoniae

• Incubation - 2-3 weeks

• Fever, headache and malaise

• Persistent non-productive cough

• Respiratory symptoms

– Radiological signs precede symptoms

• Slow resolution

• Rarely fatal

Laboratory Diagnosis - M. pneumoniae

• Microscopy

– Difficult to stain

– Can help eliminate other organisms

• Culture (definitive diagnosis)

• May take 2-3 weeks

• Serology

• PCR

Treatment and Prevention

M. pneumoniae

• Treatment

– Tetracycline or erythromycin

• Newer fluoroquinolones

– Can’t use cell wall synthesis inhibitors

• Prevention

– Avoid close contact

– No vaccine

Rickettsia and Orientia

• Small obligate intracellular parasites

• Once considered to be viruses

• Gram-negative bacteria

– Stain poorly with Gram stain (Giemsa)

• Reservoirs - animals, insects and humans

• Arthropod vectors

Disease Organism Vector Reservoir

Rocky Mountain R. rickettsii Tick Ticks, rodents

spotted fever

Scrub typhus O. tsutsugamushi Mite Mites, rodents

Epidemic typhus R. prowazekii Louse Humans,

squirrel

fleas,

Murine typhus R. thypi Flea Rodents

Rickettsia and Orientia

N.B. Orientia was formerly Rickettsia

Replication of Rickettsia and Orientia

• Infect endothelial in small blood vessels - Induced phagocytosis

• Lysis of phagosome and entry into cytoplasm - Phospholipase

• Replication

• Release

Spotted Fever Group

Rickettsia rickettsii

• spotted fever

Vector – Tick قرادFluorescent Ab staining

Clinical Syndrome - Rocky

Mountain Spotted Fever

• Incubation period - 2 to 12 days

• Abrupt onset fever, chills, headache and myalgia

• Rash appears 2 -3 days later in most (90%) patients

– Begins on hands and feet and spreads to trunk (centripetal

spread)

– Palms and soles common

– Maculopapular but can become petechial or hemorrhagic

Rash of Rocky Mountain Spotted Fever

Clinical Syndrome - Rocky

Mountain Spotted Fever

• Complications from widespread vasculitis

– Gastrointestinal, respiratory, seizures, coma, renal failure

– Most common when rash does not appear

• Mortality in untreated cases - 20%

• Incubation period - 2 to 12 days

• Abrupt onset fever, chills headache and myalgia

• Rash appears 2 -3 days later in most (90%) patients

– Begins on hands and feet and spreads to trunk (centripetal

spread)

– Palms and soles common

– Maculopapular but can become petechial or hemorrhagic

Laboratory Diagnosis - R. rickettsii

• Initial diagnosis - clinical grounds

• Fluorescent Ab test for Ag in punch biopsy

- reference labs

• PCR based tests - reference labs

• Serology

– Indirect fluorescent Ab test for Ab

– Latex agglutination test for Ab

Treatment, Prevention and Control

R. rickettsii

• Tetracycline

– Prompt treatment reduces morbidity and

mortality

• No vaccine

• Prevention of tick bites (protective clothing,

insect repellents)

• Prompt removal of ticks

• Can’t control the reservoir

Typhus Group

Rickettsia prowazekii

• Epidemic typhus

• Brill-Zinsser disease

Fluorescent-Ab staining Vector - Louse

From: G. Wistreich, Microbiology

Perspectives, Prentice Hall

Clinical Syndrome - Epidemic typhus

• Incubation period approximately 1 week

• Sudden onset of fever, chills, headache and myalgia

• After 1 week rash

– Maculopapular progressing to petechial or hemorrhagic

– First on trunk and spreads to extremities (centrifugal

spread)

• Complications

– Myocarditis, stupor, delirium (Greek “typhos” = smoke)

• Recovery may take months

• Mortality rate can be high (60-70%)

Laboratory Diagnosis - R. prowazekii

• Isolation possible but dangerous

• Serology

Treatment, prevention and Control

R. prowazekii

• Tetracycline

Rickettsia typhi

• Murine or endemic typhus

Epidemiology - R. typhiMurine or endemic typhus

• Occurs worldwide

• Vector - rat flea برغوث

– Bacteria in feces

• Reservoir - rats

– No transovarian transmission

– Normal cycle - rat to flea to rat

• Humans accidentally infected

Flea

Clinical Syndrome- Murine Typhus

• Incubation period 1 - 2 weeks

• Sudden onset of fever, chills, headache and

myalgia

• Rash in most cases

– Begins on trunk and spreads to extremities

(centrifugal spread)

• Mild disease - resolves even if untreated

Laboratory Diagnosis - R. typhi

• Serology

– Indirect fluorescent antibody test

– Treatment: doxycycline

END