Mycoplasma Urea Plasma -06-07 Med

Cell Wall-Deficient Bacteria

Cell Wall-Deficient Bacteria • Mycoplasma pneumoniae • Urealpsama urealyticum • Mycoplasma hominis

Objectives

• To know the general characteristics of Mycoplasma and how they are differ from other bacterial species. • To know the clinical diseases caused by Mycoplasma pneumoniae, Mycoplasma hominis and Mycoplasma urealyticum • To know the possible roles of Mycoplasma hominis and Mycoplasma urealyticum in infections of low birth-weight and high –risk neonates • To know the diagnostic methods for Mycoplasma pneumoniae infection • Aware about selective media for detection of mycoplasma.

Pathogenic Mycoplasama and Ureaplasama Species of Human Organism

Site

Prevalence

Disease

M. pneumoniae

Upper & lower RT

common

Primary typical pneumoniae

M. hominis

GUT

common

Postpartum fever, PID

U. urealyticum

GUT

Very common

Nongonococcal urethritis

MYCOPLASMA GENERAL CHARACTERISTICS

• The smallest free-living organism (0.3 u dia) • Have no cell wall o Insensitive to penicillins & cephalosporins o NOT stained by Gram-staining

• Cytoplasmic membrane contains cholesterol • Slow growth on specialized artificial culture media like New York City (NYC) agar media (a week) • Typical “fried-egg” appearance of colonies (seen by microscope)

MYCOPLASMA PNEUMONIAE • Not part of the normal flora, therefore its isolation is always significant and pathognomonic MAIN DISEASE • •

Primary atypical pneumonia Common in late summer and early autumn

PATHOGENESIS & EPIDEMIOLOGY • •

Droplet infection Organism adhere to respiratory epithelium

• • •

~10% of infected individuals develop pneumonia 5-10% of community acquired pneumonia Common in children & young adults

o Inhibit ciliary motion o Damage epithelium

PRIMARY ATYPICAL PNEUMONIA CLINICAL FEATURES • Infecting dose is very low with long incubation period 315 days • Age between 5-15 years • Sore throat, Cough with small amount of whitish • fever & headache Non-purulent sputum • Opacities on chest X-Rays IMMUNITY • Auto IgM Abs are produced against type O RBCs • Agglutinate RBCs at 4oC but not at 37oC : are called “cold agglutinins” Treatment

Erythromycin, tetracycline

Mycoplasma hominis and Ureaplasma urealyticum • Differentiated from mycoplasma due to urease enzyme production • Opportunistic pathogens • Both associated with infection in the urogenital tract • Frequently isolated from asymptomatic individuals, making interpretation of positive cultures difficult. • Produce “fried egg” colonies As M. pneumonia both M. hominin and U. plasama • grow on specialized medium New York city agar

Diseases

• Non-gonococcal, non-chlamydial uretheritis in men • Post-partum fever in women • Transmitted by sexual contact

MYCOPLASMA & UREPLASMA LAB DIAGNOSIS •

Culture : “Fried egg” colonies on specialized medium

Diagnosis is usually serologic • A fourfold rise of the serum titer in the acute and convalescent sera indicate M. pneumoniae • Using complement fixation, a titer of 1:128 or higher – indicates recent infection • Cold agglutinins are nonspecific but helpful TREATMENT • Tetracycline OR • Spectinomycin or • Quinolones

Case study A 14 year old young male developed gradually increasing fever and cough with small amount of whitish sputum which was non-purulent. After 3 days, fever was high grade with difficulty in breathing. On chest X-rays the lung fields showed pneumonic lesions. Gram-stained & ZN sputum smears were not diagnostic. On routine culture of sputum there was no growth. However after a week of incubation on specialized media there were fried-egg colonies by microscopic examination.

Questions 1.

What is the likely diagnosis?

2. What is the identity of the organism? 3. What serological test will help for confirmation of diagnosis? 4. What is the antibiotic of choice for this organism?

Case study A premature infant in the neonatal intensive care unit, who weighed 0.75 kg at birth, developed signs of meningitis and lumber puncture (LP) is performed. White blood cell count of the cerebrospinal fluid (CSF) was negative. The Gram stain was reported as no organisms seen, and routine culture at 3 days was no growth. The infant was still symptomatic at this time, and the pediatric physician after consultation with the microbiology laboratory, ordered additional cultures of the original CSF, which had been placed in the 370C incubator. An organism was recovered by the laboratory

Learning assessment questions • From what source did the infant described in the case study acquire the infection? • Was the infant infected during passage through the birth canal or in utero? • Would routine prenatal culture of the mother have yielded this organism? • Why was the Gram stain negative? • On what medium does this organism produce very tiny colonies? • What special procedure must be observed on specimens suspected of Mycoplasma? Why? • What current seriological assays are available to demonstrate M. pneumoniae antibodies? • How are Mycoplasma infections treated?