Mycoplasma infection�and�Cell wall defective Bacteria
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
drjonahp@yahoo.com
Introduction
Mycoplasma organisms are a small size bacteria. The name refers to the to the plasticity of bacterial cells resembling fungal elements. They have a unique, deformable cell membrane that contains sterols, which are not present in either bacteria or viruses.
They are usually associated with mucosa where they reside extracellularly in the respiratory and urogenital tracts and rarely penetrate the sub mucosa, except in the case of immune suppression or instrumentation, when they may invade the bloodstream and disseminate to numerous organs and tissues.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Introduction
Mycoplasma species are the smallest free-living organisms and are unique among prokaryotes in that they lack a cell wall.
This feature is largely responsible for their biologic properties, namely lack of a Gram stain reaction and non-susceptibility to many commonly prescribed antimicrobial agents, including beta lactams.
There are four species are of clinical importance; Mycoplasma pneumoniae, Mycoplasma hominis, Mycoplasma genitalium, and Ureaplasma Urealyticum species.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Medical importance of Mycoplasma
They form part of the normal flora of mouth, urinary tract as well as the female genital tract.
They cause atypical pneumonia transmitted by infected respiratory secretions.
They cause generally asymptomatic infection or serious pneumonitis.
They lead to complications in neurologic, hemolytic anaemia, in skin lesions, and occasionally they also cause arthritis.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Medical importance of Mycoplasma
They cause up to 10% of uterine tube infections (salpingitis and tubo-ovarian abscesses).
They lead to post abortal or post partum fever (10%).
They cause non-gonococcal urethritis, and lung disease in premature Low Birth Weights.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Microbiology
The family Mycoplasmataceae – require cholesterol or other sterols as an essential growth factor.
Prokaryotic microbes of the size 150-250 nm. They lack a cell wall but have sterol-containing cell membrane. They have fastidious growth requirements. Gives a fried-egg or mulberry like colonies appearance on agar medium.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Mycoplasma
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Microbiology 2
Mycoplasma can be cultured on liquid or solid medium and grows optimally at 35 to 37°c, growth is slow and takes 1-3 weeks. Medium of growth should be enriched with 20% horse or human serum. The colonies are fried egg like in appearance.
The surface antigens are glycolipids and proteins.
Glycolipids are identified by complement fixation.
Protein antigens are detected by ELISA method.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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How they differ from other Bacteria
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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How they differ from Viruses
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Pathogenesis
Adhesin localizes at tips of the cells and binds to sialic acid residues on host epithelial cells, infect and colonize mucous membrane; mycoplasma do not invade other tissues.
Tip organelle contains large amounts of P1 adhesin and other tip adhesins necessary for adherence to respiratory epithelium.
The mechanism of cellular damage is unknown but, ciliostasis destroy cilia and ciliated epithelial cells; breakdown clearance activity, leading to LRT infection and persistent cough.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Pathogenesis 2
Their lack of a cell wall most probably facilitates a close contact between Mycoplasma and its host cell and guarantees the exchange of compounds, which support the growth of the bacterium. As a consequence of this bacterial surface-parasitism, the host cell is severely damaged.
The exchange of toxic metabolic compounds is discussed as a possible cause of cell damage, however, at this stage not a single toxic compound has been identified as a causative agent of cell damage.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Clinical presentation
Mycoplasma are found most often on the surfaces of mucous membranes where they cause chronic inflammatory diseases of the respiratory system, urogenital tract and joints.
The most common human illnesses caused by Mycoplasma are due to infection with M pneumoniae, which is responsible for 10-20% of all community acquired pneumonias.
Presents as aches and pains, fever (usually 102°F), cough (usually non-productive), sore throat (nonexudative pharyngitis), headache/myalgias, chills but not rigors, nasal congestion with coryza, earache and general malaise.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Clinical presentation 2
Patients with sickle cell disease or related hemoglobinopathies are at increased risk for severe M pneumoniae infections and may develop large pleural effusions and marked respiratory distress.
Since in the USA sickle cell disease and other related hemoglobinopathies are most common among African Americans, severe complications of mycoplasma infections also occur most frequently in this group of patients.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Epidemiology
The disease is spread worldwide and found in all age groups.
Transmission and spread is associated with close contact with infected persons by droplet transfer of nasopharyngeal secretions.
It is a very important infection in military personel.
Even the persons who recovers from an infection will harbor the pathogens for 2 or more months.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Pneumonia
Pneumonia caused by mycoplasma is also called atypical pneumonia, walking pneumonia, or community acquired pneumonia.
Mycoplasma pneumonia is most often seen in children and young people. Up to 15 % of all cases of pneumonia in patients younger than 40 years are caused by Mycoplasma pneumoniae. Most mycoplasma infections are manifested clinically as bronchitis and/or pharyngitis. Pneumonia develops in between 3 and 10% of the patients.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Pneumonia 2
Mycoplasma pneumoniae infections lead to clinically apparent disease involving the upper respiratory tract.
In 5-10% of patients (with the rate depending on age), the infection progresses to tracheobronchitis or pneumonia and is usually self-limited. Pleural effusion (usually small) occurs in 5-20% of patients.
Mycoplasmas have also been implicated in the pathogenesis of asthma, leading to acute and chronic wheezing in some individuals.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Ureaplasma infection
Some strains of mycoplasma are frequently isolated from the urogenital tract of human beings and animals. They are also called T strains or T forms of mycoplasma.
They are peculiar in that they hydrolyze urea, which is essential growth factor in addition to Cholesterol.
They have been reclassified as Ureaplasma urealyticum.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Ureaplasma infection
Ureaplasma urealyticum is part of the normal genital flora of both men and women. It is found in about 70% of sexually active humans.
It had also been described to be associated with a number of diseases in humans, including non-specific urethritis (NSU), infertility, chorioamnionitis, stillbirth, premature birth and in the perinatal period, pneumonia, bronchopulmonary displasia and meningitis.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Ureaplasma infection
Urethritis
Pyelonephritis
Pelvic inflammatory disease
Endometritis or chorioamnionitis
Infectious arthritis
Surgical wound infections
Neonatal pneumonia
Neonatal meningitis
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Ureaplasma infection
Evidence indicates that U. urealyticum is a cause of septicaemia, meningitis, and pneumonia in newborn infants, particularly those born prematurely.
There is strong but not definitive evidence that Ureaplasma infection of the lower respiratory tract can lead to development of chronic lung disease in very low birth-weight infants.
Although risk factors for colonization of the lower genitourinary tract have been identified.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Diagnoses
For isolation, swabs from throat or respiratory secretions are inoculated.
Material from urethra, cervical, vaginal or centrifuged deposit of urine is added to separate vials with liquid mycoplasma medium containing phenol red and 0.1% glucose, arginine or urea.
Phylogeny rapid identification of urogenital mycoplasma based on amplification of part of 165rRNA gene by PCR is available for clinical use.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Diagnoses 2
Cold Agglutination test is associated with macroglobulin antibodies that agglutinate human O-group RBC at low temperatures.
Streptococcal MG test
Immunofluorescence
Hemagglutination inhibition test.
Complement fixation test are less sensitive.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Treatment
• Mycoplasma pneumoniae: erythromycin, tetracycline
• Ureaplasma urealyticum: use erythromycin, (resistant to tetracycline)
• Mycoplasma hominis: (resistant to both erythromycin and tetracycline), use clindamycin.
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Other Cell wall defective bacteria
These are mutant bacteria with defective cell walls also known as L-forms. They are a result of; a) Spontaneous mutation or, b) Effects of chemicals on bacteria or, c) Effect of enzymes (lysozymes) on bacteria.
If a gram-positive bacteria cell is attacked and the cell wall is destroyed completely what remains is known as a Protoplast. If the attacked gram-positive cell’s wall is not completely destroyed and the outer membrane remains, it is known as a Spheroplast.
These forms are not genetically related to Mycoplasmas
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Other Cell wall defective bacteria 2
Some are stable and can replicate as non rigid cell and produce colonies on solid media cell.
Others are unstable and revert to parental form when cultured in media free of inhibitor of cell wall.
They do not have sterols on their cell membrane and can form cell wall under appropriate conditions.
With about 15-30% gelatin or 2.5% agar in growth media there is enhanced reversion of L-forms to parental forms. Inhibitors of protein synthesis inhibits reversion of L-forms
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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Thank you for listening
Any questions???
Dr. Jonah Y. Peter (BM BCh, MSc, FMCPath, MRCPath)
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