Mycoplasma and Cell Mycoplasma and Cell wall defective bacteriawall defective bacteria

Dr Sabrina MoyoDr Sabrina MoyoDepartment of Microbiology and Department of Microbiology and

ImmunologyImmunology

MycoplasmaMycoplasmaSmallest viable form in cell free Smallest viable form in cell free

media can pass pore of 200nm- media can pass pore of 200nm- 450nm450nm

Due to their smallest size, originally Due to their smallest size, originally thought to be viruses, but differ inthought to be viruses, but differ in

i)Division by binary fissioni)Division by binary fission Ii)Growth on artificial cell free mediaIi)Growth on artificial cell free media Iii)Contain both RNA and DNAIii)Contain both RNA and DNA

ClassificationClassification At least 15 spp are thouhgt to of human At least 15 spp are thouhgt to of human

origin, but four spp are of medical origin, but four spp are of medical importanceimportance

M.pneumoniae- pnuemoina M.pneumoniae- pnuemoina M.hominis- M.hominis- postpartum fever and uterine postpartum fever and uterine

tube infectionstube infections Ureaplasma Ureaplasma urealyticum-non gonococcal urealyticum-non gonococcal

urethritis and lung disease in premature urethritis and lung disease in premature infants of LBWinfants of LBW

M.genitalium- M.genitalium- urethral infectionsurethral infections

General characterisitcsGeneral characterisitcs Smallest organisms that can be free living Smallest organisms that can be free living

125-250nm in size125-250nm in size Highly pleumorphic because of lack of rigid Highly pleumorphic because of lack of rigid

cell wallcell wall Completely resistant to penicillin because Completely resistant to penicillin because

of lack of cell wallof lack of cell wall Can reproduce in cell free media, on agar Can reproduce in cell free media, on agar

produce colonies of fried egg appearanceproduce colonies of fried egg appearance Have affinity for mammalian cell membraneHave affinity for mammalian cell membrane

General characterisitcsGeneral characterisitcs Gram –ve , stain poorly with bacteria stain, Gram –ve , stain poorly with bacteria stain,

but stain well with Giemsabut stain well with Giemsa Bounded by triplle-layered unit membrane Bounded by triplle-layered unit membrane

that contain sterolthat contain sterol Cannot be studied by usual bacteriologic Cannot be studied by usual bacteriologic

methods because of the small size of their methods because of the small size of their colonies and delicacy due to lack of rigid colonies and delicacy due to lack of rigid cell wallcell wall

Growht require addition of serum or Growht require addition of serum or cholestrol to the medium to produce sterolscholestrol to the medium to produce sterols

Culture and growth Culture and growth characteristicscharacteristics

They are facultative anaerobes except They are facultative anaerobes except for M.pneumoniae strict aerobefor M.pneumoniae strict aerobe

Use glucose as energy sourceUse glucose as energy sourceGrowth require sterol supllied by animal Growth require sterol supllied by animal

serum, Ureaplasma reqiure ureaserum, Ureaplasma reqiure ureaMay strains grow in heart infusion May strains grow in heart infusion

peptone broth with 2% agar pH 7.8 and peptone broth with 2% agar pH 7.8 and animal serum or 30% ascitic acid addedanimal serum or 30% ascitic acid added

Culture and growth Culture and growth characteristicscharacteristics

Grows better on HGrows better on H22 and N and N2 2 with 10% COwith 10% CO22most grow at 37most grow at 3700C Grow slowly C Grow slowly

generation time 1-6 hrsgeneration time 1-6 hrsAfter 2-6 days of incubation produce After 2-6 days of incubation produce

small colonies that have freid- egg small colonies that have freid- egg appearanceappearance

M.pnuemoniae colonies do not have a M.pnuemoniae colonies do not have a thin halo; mullberry-shapedthin halo; mullberry-shaped

PathogenesisPathogenesisPathogenic Mycoplasma have polar Pathogenic Mycoplasma have polar

tips structures-mediate adherence to tips structures-mediate adherence to host cellshost cells

Direct cytotoxicity through generation Direct cytotoxicity through generation of hydrogen peroxide and superoxide of hydrogen peroxide and superoxide radicalsradicals

Cell lysis-by antigen antibody Cell lysis-by antigen antibody reactions/ chemotaxis and action of reactions/ chemotaxis and action of mononuclear celllsmononuclear cellls

Medical importanceMedical importance Part of normal flora of mouth, Part of normal flora of mouth,

genitourinary tract especially femalesgenitourinary tract especially females i) atypical pneumoniai) atypical pneumoniaIncubation period 1-3 wksIncubation period 1-3 wksM.pneumoniae- transmitted by infected M.pneumoniae- transmitted by infected

respiratory secretionsrespiratory secretionsGenerally mild disease, asypmtomatic Generally mild disease, asypmtomatic

infection-serious pneumonitisinfection-serious pneumonitisComplications-neorologic, hemolytic Complications-neorologic, hemolytic

anaemia, skin lesionsanaemia, skin lesions

Medical importanceMedical importance ii) uterine tube infections(salpingitis and ii) uterine tube infections(salpingitis and

tubo-ovarian abscesses) 10%tubo-ovarian abscesses) 10% post abortal or post partum fever(10%)post abortal or post partum fever(10%)Occasionally arthritisOccasionally arthritisCan be caused by M.hominisCan be caused by M.hominis iii)non gonococcal urethritis,and lung iii)non gonococcal urethritis,and lung

disease in premature LBWdisease in premature LBWCan be caused by Can be caused by U.urealyticum U.urealyticum or or

M.genitaliumM.genitalium

DiagnosisDiagnosisSpecimen include, blood, Specimen include, blood,

sputum ,urethral exudatessputum ,urethral exudatesDirect staining is of limited useDirect staining is of limited useCultureCultureCF, titer of 1:64 support diagnosisCF, titer of 1:64 support diagnosisimmunflorescenceimmunflorescence

Susceptibilty to chemical Susceptibilty to chemical physical agents and antibioticsphysical agents and antibiotics

Lack of cell wall make organisms Lack of cell wall make organisms susceptible to most disinfectants and susceptible to most disinfectants and antisepticsantiseptics

Killed when held at 56oC for 30 minutesKilled when held at 56oC for 30 minutes Sensitive to antimicrobials that inhibit Sensitive to antimicrobials that inhibit

protein synthesis e.g tetracyline, protein synthesis e.g tetracyline, erythromicin,chloramphenicalerythromicin,chloramphenical

Resitant to antimicrobials acting on cell wall Resitant to antimicrobials acting on cell wall e.g penicillines, cephalosporins and e.g penicillines, cephalosporins and vancomycinvancomycin

Cell wall- defective bacteriaCell wall- defective bacteria Mutant bacteria with defective cell walls Mutant bacteria with defective cell walls L-formsL-forms Result from Result from i) Spontaneous mutation or i) Spontaneous mutation or Ii) from effects of chemicalsIi) from effects of chemicals Iii) Enzymes (lysozymes)Iii) Enzymes (lysozymes) If they attack gram positive it destroy the cell wall and If they attack gram positive it destroy the cell wall and

result to result to ProtoplastProtoplast If they attack gram positive cell wall is not completely If they attack gram positive cell wall is not completely

destroyed outer membrane remain form destroyed outer membrane remain form SpheroplastSpheroplast Not genetically related to mycoplasmasNot genetically related to mycoplasmas

Cell wall- defective bacteriaCell wall- defective bacteriaSome are stable and can replicate as non rigid Some are stable and can replicate as non rigid

cell and produce colonies on solid mediacell and produce colonies on solid mediaOthers are unstable and revert to parental Others are unstable and revert to parental

form when cultured in media free of inhibitor form when cultured in media free of inhibitor of cell wallof cell wall

Do not have sterols on their cell membraneDo not have sterols on their cell membraneCan form cell wall under appropriate Can form cell wall under appropriate

conditionsconditions15-30% gelatin or 2.5% agar in growth media 15-30% gelatin or 2.5% agar in growth media

enhance reversion of L-forms to parental formenhance reversion of L-forms to parental form Inhibitors of protein synthesis inhibits Inhibitors of protein synthesis inhibits

reversion of L-formsreversion of L-forms