By Dr.Sujith S

SpeciesMycoplasma pneumoniaeMycoplasma hominisMycoplasma genitaliumUreaplasma urealyticum

PathogenesisPathogenic organisms for humans and

animals possess specialized tip organelles that mediate their interactions with host cells.

This host-adapted survival is achieved by i)surface parasitism of target cells

ii) the acquisition of essential biosynthetic precursors

iii) cell entry and intracellular survival.

Toll-like receptor 2 for binding of Mycoplasma and activation of inflammatory mediators, including cytokines.

M. pneumoniae grows under both aerobic and anaerobic conditions ,isolated on media supplemented with serum.

The organism most commonly exists in a filamentous form and has adherence proteins that attach to epithelial membranes with particular affinity for respiratory tract epithelium

An immune-mediated mechanism in infants and young children developing pneumonia.

In addition, the antibodies produced against the glycolipid antigens of M. pneumoniae may act as autoantibodies, since they crossreact with human red cells and brain cells.

EpidemiologyM. pneumoniae is transmitted from person-

to-person by infected respiratory droplets during close contact.

The incubation period after exposure averages three weeks .

Infection occurs most frequently during the fall and winter but may develop year-round

Mycoplasma pneumoniaeone of the most common causes of atypical pneumonia

Atypical pneumonia account for 7 to 20% of community-acquired pneumonia

The incidence may be higher in patients with milder disease that can be managed without hospitalization

Many infections due to M. pneumoniae are asymptomatic.

The signs and symptoms vary according to the stage of illness

Headache, malaise, and low grade fever. Chills are frequent.

Cough due to M. pneumoniae infection ranges from nonproductive to mildly productive, with sputum discoloration occurring late in the disease.

Wheezing may occurPharyngitis Rhinorrhea and Ear pain

Extrapulmonary manifestationsThese manifestations include HemolysisSkin rashJoint involvementSymptoms and signs indicative of

gastrointestinal tract, central nervous system, and heart disease..

HaemolysisAntibodies (IgM) I antigen on erythrocyte

membranes appear during the course ; produce a cold agglutinin response in about 60 % of patients .

Skin DiseaseDermatologic manifestations a mild

erythematous maculopapular / vesicular rash to the Stevens-Johnson syndrome.

16 % patients with Stevens-Johnson syndrome had evidence of mycoplasma infection.

Central Nervous SystemCNS involvement occurs most frequently in children,

with encephalitis as the most frequent manifestation. Other manifestations include aseptic meningitis,

peripheral neuropathy, transverse myelitis, cranial nerve palsies and cerebellar ataxia .

Acute transverse myelitis (ATM) and acute disseminated encephalomyelitis (ADEM) most severe complications .

59 percent of patients presenting with spinal cord involvement suffered permanent neurologic sequelae .

Other SystemsRheumatologic symptoms including tender

joints and muscles and polyarthritis. Arthritis is believed to result from immune-

mediated mechanismsM. pneumoniae has been isolated from

synovial fluid in some patients with polyarthritis.

Cardiac or renal involvement -unusual . Rhythm disturbances, congestive heart

failure, chest pain, and conduction abnormalities on the electrocardiogram.

Clinically significant glomerulonephritis is a rare complication that is presumed to be secondary to immune complex deposition

Chest X-RayBronchopneumoniaPlate-like atelectasisNodular infiltrationHilar adenopathyThe most common radiographic finding is the

peribronchial pneumonia pattern, which consists of a thickened bronchial shadow, streaks of interstitial infiltration, and areas of atelectasis; these changes have a predilection for the lower lobes.

Nodular infiltrates and hilar adenopathy less common, and result in a broader differential diagnosis, including tuberculosis, mycotic infections, and sarcoidosis

Lab DiagnosisSubclinical evidence of hemolytic anemia is

present in the majority of patients with pneumonia positive Coombs' test and elevated reticulocyte count.

Cold agglutinin titers are elevated in 50 percent of patients with mycoplasma disease, and the titer usually exceeds 1:128 in patients with pneumonia

With overt hemolysis, titers may be as high as 1:50,000.

Elevated Cold Agglutinin TitresInfectious Mononucleosis secondary to

Epstein Barr virus CytomegalovirusAdenovirus pneumoniaViral illness Lymphoma and Collagen vascular disorders

The white blood cell count (WBC) normal 75 to 90 percent of cases.

Thrombocytosis can occur acute phase response.

CSF-Lymphocytic pleocytosis, elevated protein, and normal glucose.

Isolation of M. pneumoniae in CSF - possible. A culture is more likely to be positive in

encephalitis rather than myelitis. PCR testing for Mycoplasma in the CSF can

also be performed.

TreatmentTreatment options for outpatient community-

acquired pneumonia are presented in the 2007 consensus IDSA/ATS guideline:

Macrolide antibiotics (azithromycin, clarithromycinor erythromycin) first line treatment .

Azithromycin (500 mg orally once daily, initially followed by 250 mg orally for 4 days) has become the most commonly used drug regimen.

Adjunctive TherapyFor hemolytic anemia, case reports indicate

some patients respond to warming, steroid therapy, possibly plasmapheresis.

For CNS disease, therapy with steroids, antiinflammatory drugs, diuretics, and plasma exchange ,used in addition to antibiotics.

M.HominisEpidemiology:M. hominis is part of the

normal genital flora of many sexually experienced men and women

Infants & childrren:Newborns are likely to become colonized during passage through the birth canal..

The organismMycoplasma are the smallest free-living bacteria.

M. hominis cannot be visualized by Gram stain.

M. Hominisproduces nonhemolytic colonies on sheep blood agar after three to five days of incubation.

M. hominis does not alter the appearance of blood culture media; therefore,routine blind subculturing onto blood is required for detection.

For optimizing the recovery of M. hominis, clinical specimens should be immediately inoculated onto culture media and not allowed to dry.

After plating, cultures should be promptly incubated or kept at 4ºC.

The best laboratory culture media is beef heart infusion broth (also known as pleuropneumonia-like organism) (PPLO) broth with fresh yeast extract and horse serum.

PCR is superior to traditional culture methods for detecting M. hominis in genital secretions.

Genitourinary infectionPyelonephritisPelvic inflammatory diseaseChorioamnionitisPostpartum and postabortal feverNongenitourinary infections that have been linked to M.

hominis include:SepticemiaWound infectionsCentral nervous infectionsJoint infectionsLower respiratory tract infectionsEndocarditis

Post partum & post abortal feverM. hominis causes approximately 10 percent

of all cases of postpartum and postabortal fever.

There was a fourfold rise in antibody titers in one-half of all women who had postabortal fever compared to only 2 of 53 controls who had abortion without fever.

PIDM. hominis was isolated from 4 of 50 fluid

samples taken directly from the fallopian tubes of women with salpingitis.

Significant rises in antibody titers to M. hominis occurred in 9 of 16 women with salpingitis who had positive lower genital tract cultures for M. hominis .

UTIM. hominis can frequently be recovered from

the lower genitourinary tract in men and women.

Chorioamnionitis M. hominis, along with Ureaplasma

urealyticum, is frequently found in the amniotic fluid of women with

i)preterm labor, ii) preterm premature rupture of

membranes iii) spontaneous labor at term iv) premature rupture of

membranes at term v) chorioamnionitis

CNSM. hominis infection has been associated with

non-functioning CNS shunts , brain abscess , subdural empyema, and meningitis.

M. hominis arthritis can occur in women after childbirth, in conjunction with congenital immune defects, such as hypogammaglobulinemia , in association with immunosuppression (eg, in solid organ transplant patients) or lymphoma , or following joint replacement surgery or trauma.

M. hominis arthritis is usually characterized by fever, leukocytosis, and a purulent joint effusion with large numbers of polymorphonuclear cells but a negative Gram stain.

Wound infectionsM. hominis has been associated with infected

pelvic hematoma , infected cesarean wounds, and sternal wound infections

TreatmentTetracycline is the treatment of choice

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