Mycoplasma, Rickettsia, and Chlamydia (2023) PDF

Mary Petzke, [email protected]. Mycoplasma, Rickettsia and Chlamydia §Smallest free-living bacteria: 0.1 µm (100 nanometers)once believed to be viruses§Among the smallest genomes: 500-800 Kbp(500-650 genes)§PleiomorphiccocciForm branched myceloidstructuresmyces= fungus-like§Slow growth:divi...

Mary Petzke, [email protected]. Mycoplasma, Rickettsia and Chlamydia §Smallest free-living bacteria: 0.1 µm (100 nanometers)once believed to be viruses§Among the smallest genomes: 500-800 Kbp(500-650 genes)§PleiomorphiccocciForm branched myceloidstructuresmyces= fungus-like§Slow growth:division time of 1-16 hrsMycoplasmataceae: physiology Typical bacteriumRed blood cellMycoplasma Mycoplasmataceae: cellular structureNO CELL WALL!!!•Resistant to antibiotics that interfere with peptidoglycan synthesis (penicillins, cephalosporins, vancomycin)•Does not Gram-stain well (“ghosts” = unstained areas)The only bacteriato have a cell membrane that contains sterols, such as cholesterolØCulture medium needs to be supplemented with source of sterols(remember the “fried egg” colonies!) Atypical respiratory pathogens: M. pneumoniae, Chlamydophila pneumoniae,Legionella pneumophila§Strict human pathogen§Tr a n s m i s s i o n :inhalation of respiratory droplets§A major respiratory pathogen in the U.S.: •2 million pneumonia cases/year (100,000 hospitalizations) •Frequent cause of community acquired pneumonia§Infections occur year-round(non-seasonal)§Primarily infects5 to 15 year age group,but all ages are susceptible!Mycoplasma pneumoniae: epidemiology M. pneumoniae: pathogenesis1) Adheres to ciliated epithelial cellsof respiratory tractP1 adhesinin attachment structure binds to sialoglycoproteinreceptors at the base of cilia2) Epithelial cells depolarize/M. pneumoniae can invade bloodstreamUpper airway clearance compromisedby loss of ciliated cells = coughing3) Immune cells migrate to site of infection: M. M. pneumoniae surface lipoprotein is a superantigenCytokine production (TNF-a, IL-1, IL-6) Bacterial clearance/inflammationAttachment structureCilium M. pneumoniae: clinical manifestationsØMost exposures result in asymptomatic carriage§2-3 week incubation period, then:•low-grade fever, malaise, headache, acute pharyngitis•tracheobronchitis(most common)§Symptoms worsen over next few days as bronchial passages become infiltratedwith lymphocytes and plasma cells•atypical or “walking” pneumoniacan develop•possible complications: autoimmune hemolytic anemia, skin rashMIRM: Mycoplasma-induced rash and mucositisin 30% of M. pneumoniae infections M. pneumoniae: atypical pneumoniaAtypical or “walking” pneumonia:a type of pneumonia caused by certain bacteria, including M. pneumoniae,Chlamydophilapneumoniaeand Legionella pneumophila§Usuallymilder form of pneumoniawith less acute symptomsrash(esp. with M. pneumoniae) But, can be SEVERE!§Clinical exam may not be exceptional §Chest X-ray often reveals patchy bronchopneumonia§Can persist for longer than 2 weeks, or even months§Respiratory illness plus rash = consider M. pneumoniae §Diagnosis•Serology: IgM titers to P1 antigen; presence of cold agglutinins = antibodies that bind red blood cells at colder temperatures •Nucleic acid amplification tests: throat swab and sputum rapid and sensitive Mycoplasma infections: diagnosis and control§Tr e a t m e n tAll Mycoplasmaand Ureaplasmaare resistantto peptidoglycan inhibitors (penicillins, cephalosporins, vancomycin = no cell wall)!•Erythromycin, doxycycline, newer fluoroquinolones§Prevention•No vaccines or chemoprophylaxis•Immunity to re-infection is not lifelong Rickettsia§Small, Gram-negative bacilli§Very small genomes (1-1.5 million bases)§Obligate intracellular pathogensmultiply by binary fission in cytosol§Animal reservoirs = zoonotic infections§Transmitted by arthropod biteTick, louse, or flea Rickettsial diseasesA) Rocky mountain spotted fever(Rickettsia rickettsii)“Tick typhus”: Tick vector, rodent reservoirFever/severe headacheSkin rash: wrists and ankles to trunk and palms of hand/soles of feetCentral nervous system affected, circulatory collapse20% mortality rate if untreatedHard-shelled tick B) Epidemic typhus (Rickettsia prowazekii) “louse typhus”: louse vector, humansare primary host•Spread in feces of body louse•Risk factors: crowded, unsanitary conditions•Symptoms can be similar to RMSF or milder•Up to 60% mortality without antibiotic treatment•3 million deaths during World War I (“trench fever”)RickettsialdiseasesHuman body louse C) Endemic typhus (Rickettsia typhi) “murine (mouse) typhus”: Flea vector, rodent reservoirMild symptoms, resolves within 3 weeks“backwards rash” (relative to tick typhus): trunk to limbsScratching flea feces into bite woundRickettsialdiseasesMouseFlea Rickettsial diseases: management§NO laboratory tests available for early diagnosis (before antibody development): PCR tests under development§Treatment: doxycyclineis drug of choice §Prevention: prompt removal of ticks§Hygiene: avoid lice, rodents, fleas Playing doctor is a game you don't want to lose. Know the rules. www.giantmicrobes.com §Small, Gram-negative rods §Genome: very small, ~ 1000 Kbp§Non-motile§Obligate anaerobes §Obligate intracellular pathogens: “energy parasites”= use host cell ATP§Unique developmental cycle: elementaryandreticulate formsØNo peptidoglycansin cell wall!Cannot treat with beta-lactamsChlamydiaceae Chlamydiaceae: taxonomyGenus Chlamydia (“cloak”)§Biovar:strains within a species that have different physiological and/or biochemicalcharacteristics•Chlamydia trachomatis: biovarstrachomaand LGV•Chlamydia pneumoniae: biovarTWAR•Chlamydia psittaci: many biovars!§Serovar:like a serogroup—strains within a biovarthat have different antigenicproperties •Determined by the structure of the major outer membrane protein(MOMP)ØDifferent serovarscause different diseases Medically important ChlamydiaceaeSpeciesBiovarsSerovarsDiseasesChlamydia trachomatis(human to human)Inclusion bodies contain glycogen = stain with iodinetrachomaLGVA, B, Ba, CD-KL1, L2, L2a, L2b, L3Ocular trachomaUrogenital infections,adult inclusion conjunctivitis infant conjunctivitis, pneumonia Lymphogranuloma venereum, ocular LGVChlamydia pneumoniae(human to human)TWARRespiratory tract infections: bronchitis, bronchiolitis, sinusitisAtypical pneumoniaNeonatal/infant pneumoniaChlamydia psittaci(bird to human)Many!Psittacosis(respiratory illness which can disseminate to liver and spleen = fatal in 5% of cases) Chlamydiaceae: elementary bodies•Size: small, 300-400 nanometers•Cell wall: rigid and tough, has cysteine-rich P-layer(no peptidoglycans)•Resistant to harsh environment•Metabolically inactive•Infectious!§Elementary body (EB)= analogous to a sporeA Chlamydia trachomatiselementary body (EB) entering a HeLa cell §Reticulate body (RB): Intracellular•Size: larger than EB = 0.8-1 micron; forms an inclusionin the host cellC. trachomatisinclusions contain glycogen, stain with iodine•Low resistance properties: susceptible to osmotic pressure •Cell envelope: fragile, no cross-linked proteins, pleomorphic•Metabolically active = REPLICATES•Non-infectiousChlamydiaceae: reticulate bodies NucleusXElementary bodyPhagocytosis Phagosome EB reorganizes(EB)attaches toof EB occurs does NOT fuse into reticulate bodycell surface with lysosome (RB)in phagosomeAdapted from: http://pathmicro.med.sc.edu/mayer/chl-life.jpgChlamydiaceae: growth cycle48-72 hrs post-infection= 100-500 progeny/ inclusion bodyC. trachomatis, C. pneumoniaeReverse endocytosisLysis of inclusion bodies and cellsC. psittaciNucleusNucleusNucleusNucleusNucleusLysosomeLysosomeBoth RBs and EBs RBsRB replicatesin inclusion reorganizedby binarybody to EBsfission Inclusion body in a lung cell(Chlamydophila psittaci)NucleusSecond inclusion body forming Chlamydia trachomatis: pathogenesis§Infects non-ciliated epithelial cells of eye, respiratory and urogenital tract•Biovar LGV also invades mononuclear phagocytes§Stimulates infiltration of polymorphonuclear cells (PMNs) and lymphocytes = inflammation•Lymphoid follicle formation and fibrosis§Pathogenesis due to destruction of epithelial cells and host inflammatory response (similar to Mycoplasma)Infection DOES NOT stimulate immunity:Re-infection = vigorous inflammatory response and additional tissue damage C. trachomatisinfections: overview§Biovar trachoma•Serovars A, B, Ba, COcular trachoma•Serovars D-KGenitourinary infectionsNeonatal conjunctivitisAdult inclusion conjunctivitisInfant pneumonia§Biovar LGV•Serovars L1, L2, L2a, L2b, L3Lymphogranuloma venereum (LGV)Ocular LGV(LGV)OcularOcular trachomaInclusion conjunctivitisOcular LGVGenitourinaryProctitisNongonococcal urethritisSalpingitisCervicitisLymphogranuloma venereum Infantpneumonia Ocular trachoma: epidemiologyC. trachomatisbiovar trachoma, serovars A, B, Ba, C(Trachoma = Gr. trakhus, or “rough”)§A leading cause of preventable blindness worldwide•~500 million people infected•7-20 million cases of blindness•endemic in North and sub-Saharan Africa, the Middle East, southern Asia, South America§Infections predominate in children, but incidence of blindness increases into adulthood§Transmission: eye-seeking flies, respiratory droplets, fecal contamination, hand-to-eye§Risk factors: poor sanitation and hygiene, crowded living conditions Ocular trachoma: global distributionWorld Health Organization Ocular trachoma: clinical manifestations2) Trachomatous trichiasisScarred and malformed eyelid turns inwardsContinual scraping of cornea by eyelashes3) Corneal opacityScarring, ulceration and vascularization in corneaOpacification of corneaIrreversible BLINDNESS1) Trachomatous scarringFollicular conjunctivitis with diffuse inflammationLymphocyte infiltrationScarringPhotos: World Health OrganizationLymphoid follicles (round, white, paler than surrounding tisue, at least 0.5 mm diameter) Nat Rev Microbiology; doi:10.1038/nrmicro1555Chlamydia: the leading bacterialSTD globallyChlamydia (Chlamydia trachomatis) = 92 millionGonorrhea (Neisseria gonorrhoeae) = 63 millionSyphilis (Tr e p o n e m a p a l l i d u m) = 12 millionCo-infection common ...and in the United States! C. trachomatis:urogenital infections§Males(~75% symptomatic)Mucopurulent urethritisA leading cause of nongonococcalurethritis (NGU)Complications: Epididymitis, sterility§Females(~25% symptomatic) Mucopurulent cervicitisDysuria/urethritisComplications: Inflammation/scarring of fallopian tubesPerihepatitisPelvic inflammatory disease (PID)*Most common cause of “silent” (asymptomatic) PID in USEctopic pregnancy, infertility Many infections go untreated due to lack of symptoms,especially in women (75% are asymptomatic)! Asymptomatic chlamydia infection is the MOST COMMON causeof the increasing number of tubal (ectopic) pregnancies and infertility problems in women in the USEctopic pregnancy is the leading cause of pregnancy-related deaths during the first trimester! Related C. trachomatisinfections§Adult inclusion conjunctivitis•Autoinoculationfrom urogenital infections•Mucopurulent discharge, corneal infiltrates§Neonatal/infant conjunctivitis•Acquired at birth by 15-40% of infants whose mothers have active genital infection•Mucopurulent discharge•Routine prophylaxis against N. gonorrhoeae (eyedrops) is NOT always effective! §Infantpneumonia (most common cause)•Acquired at birth in 10-20% of infants of infected mothers•Incubation period: 2-3 weeks•Rhinitis, distinctive staccato cough, no fever Lymphogranuloma venerium(LGV)Epidemiology:§U.S.= mostly men who have sex with men(MSM)Highly prevalentin tropical and sub-tropical regions (Asia, Africa and South America)Symptoms:(1-4 week incubation period)§Primary: Single, small lesion at site of infection (genitals, perianal) = painless, heals rapidly§Secondary: Invasion of regional lymph nodes (inguinal or perirectal)Systemic symptoms: fever, headache, myalgias Regional lymphadenopathy = formation of buboes§Tertiary:Ruptured buboes = draining fistulas Proctitis Blockage of lymphatics = genital elephantiasisOcular LGV can occur via autoinoculationBiovar LGV(replicates inside macrophages ) serovars L1, L2, L2a, L2b and L3 C. trachomatis: diagnosis§Culture Difficult--intracellular growth requirementsTissue (NOT discharge) must be obtained§Direct fluorescent antibody testFluorescent antibody used to detect chlamydial antigens in tissue§Nucleic acid amplification tests (PCR)Diagnostic test of choice for urogenital infectionsMOST sensitive (99%)Simultaneous diagnosis of N. gonorrhoeaeVaginal swabs, urine (men AND women) and urethral dischargeIodine-stained inclusions C. trachomatis: treatment and preventionTr e a t m e n tØPeptidoglycan inhibitors are INEFFECTIVE!•Doxycycline, azithromycin, erythromycinPrevention•No vaccine or chemoprophylaxis!•Patient education, safe sex practices and aggressive partner follow-up•Annual screening of all sexually active females <25 years old(CDC 2015 STD Treatment Guidelineshttp://www.cdc.gov/std/tg2015/chlamydia.htm) Chlamydia pneumoniae§Strictly human pathogen§Transmitted via respiratory secretions§Mostinfections asymptomatic or mild (cough)§More severe infections include:sinusitispharyngitisbronchitisatypical or “walking” pneumonia(usually in single lobe) C. pneumoniae: diagnosis and treatment§Diagnosis is difficult!•Atypical pneumoniacaused by C. pneumoniaeis indistinguishable from that caused by other bacteria (Mycoplasma pneumoniae, Legionella)•C. pneumoniaedoes not grow in most laboratory cell lines§Microimmunofluorescence test (MIF)is the only acceptable test for serodiagnosis •Acute infection: single IgM titer of > 1:16 or 4-fold increase in IgG titer§Treatment:•Macrolides, doxycycline, or levofloxacin §Caused byChlamydia psittaci§Zoonotic, occasionally infects humansØAnyspecies of birdscan be reservoir, but especially psittacinespecies (parrots, cockatiels, parakeets, macaws)§Acquisition via inhalation of dried excrement, urine, or respiratory secretions of infected birds§25-100 reported cases annually in U.S. (likely more: many cases are asymptomatic)•Most cases in ADULTS §Respiratory tract infections can lead to severe illnesspsittacus, “parrot”ornithos, “bird”Psittacosis (Ornithosis) Psittacosis/Ornithosis (C. psittaci)7-15 day incubation period 5% mortality rate 5% mortality rate Uncomplicated infection“flu-like” symptoms: nonproductive cough, rales, fever, headacheUsually full recovery in 2-3 weeksSevere infectionOrganisms spread to reticuloendothelial cells of liver and spleen, multiply and causefocal necrosisSecondary bacteremiato lungs:--Inflammation, edema, thickening of alveolar wall, necrosis, occasional hemorrhage--Mucous plugs develop in bronchioles = cyanosisCNSinvolvement can lead to coma and death C. psittaci:diagnosis and treatment§Diagnosis: A sudden onset of illness taking the form of influenza or atypical pneumonia in a person exposed to birds is suggestive Serology•Species-specific microimmunofluorescence(MIF) test•IgM titer ≥1:16 or a 4-fold increasein titer to at least 1:32§Treatment: Doxycycline or macrolides (erythromycin, azithromycin, clarithromycin)§Prevention:No vaccine available!Control of bird shipmentQuarantine and testing of imported birdsProphylactic tetracylines in bird feed Thank you!