Overview of Rickettsiae, Chlamydiae, and Mycoplasma
This lecture covers the identification, chemical tests, differentiation, symptoms, diagnosis, and treatment of Rickettsiae, Chlamydiae, and Mycoplasma. It explores the similarities and differences between Rickettsiae and Chlamydiae, as well as their characteristics, growth requirements, and examples. The taxonomy of Rickettsia is discussed, including the species within the Ricketsiaceae family. Additionally, it compares Rickettsiae and Chlamydiae with bacteria and viruses in terms of size, reproduction, sensitivity to antibiotics, and metabolic functions.
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Objectives By the end of this lecture the student must be: A) Identify the genus Rickettsiae, Chlamydiae, and Mycoplasma B) B) describe the chemical tests for this genus C) Differentiate between different sps. D) List and match the symptoms, diagnosis and treatment for different sps.
Rickettsiae and Chlamydiae Similarity between Rickettsiae & Chlamydiae Rickettsiae are similar to Chlamydia in that Both are obligate intracellular energy parasites Share with viruses Both are similar in size as large viruses Both grow in living media (yolk sac of chick embryo) They have both DNAand RNA They have ribosomes Share with bacteria Both are replicate by binary fission Both are sensitive to antibacterial agents 2
Rickettsiae and Chlamydiae Rickettsiae are different to Chlamydia in that Require arthropod vector (except for Q fever) Replicates freely in cytoplasm while Chlamydia replicates in endosomes Ricketsia has tropism for endothelial cell that line blood vessels while Chlamydia like columnar epithelium 3
RICKETTSlACEAE Small Gram-negative coccobacilli (0.3-0.5 ~m in length) that stain poorly spore forming Cell membrane is similar to that of Gram-negative bacteria; contains LPS and peptidoglycan Obligate intracellular parasites, require growth cofactors (e.g., acetyl-CoA, NAD, ATP) provided by the cell Will not grow on artificial media Example Coxiella burnetii cause Q-fever
Comparison of Chlamydiae & Rickettsiae with Bacteria & Viruses Bacteria Chlamydia & Rickettsia Viruses Size (nm) 300-3000 350 15-350 Obligatory intracellular No Yes Yes Nucleic acids DNA OR RNA DNA & RNA DNA & RNA Reproduction Fission Complex cycle with fission Synthesis & assembly Antibacterial sensitivity Yes Yes No Ribosomes Yes Yes No Metabolic enzymes Yes Yes No Energy production Yes No No 5
Rickettsiae Taxonomy of Rickettsia Family: Ricketsiaceae Genus: Rickettsia, Coxiella, Bartonella Species 1. Rickettsia prowazekii (epidemic typhus) 2. Rickettsia typhi (endemic typhus) 3. Rickettsia rickettsii (spotted fever) 4. Bartonella quintana (trench fever) 5. Bartonella henselae (cat scratch fever) 6. Coxiella burnetii (Q fever) 6
Rickettsiae Gram-negative, coccobacilli, non-motile Best stained by Giemsa or Machiavello stains Small (0.3-0.5 x 1-2 m) prokaryotic cells Contain both RNA & DNA & Multiply by binary fission Obligate intracellular energy Except Bartonella quintana They grow in tissue culture or yolk sac Except B. quintana: grow on blood agar under 5%CO2 All Rickettsial diseases are zoonotic Except Epidemic typhus and Trench fever 7
Rickettsiae Transmitted through arthropod vector from reservoir Arthropods serves as both vector and reservoir Except C. burnetii does not transmitted through vector Cause skin rash, fever, headache & malaise ESCHAR, black ulcer developed at site of inoculation Except C. burnetii cause pneumonia, slow fever & hepatitis Rickettsiae are susceptible to antiseptics, dryness & heat Coxiella resist pasteurization at 600C for 30 m Rickettsiae are sensitive to chloramphenicol & doxycycline8
Pathogenic Mechanism Virulence factors Endotoxin, Phospholipase A, slime layer Bites or faeces of arthropod Mechanism Local lymph or micro blood vessels (1st bacteremia) Endothelial cells, micro blood vessels in whole body (2nd bacteremia) Fever, rash, headache, etc Targets: Endothelial cells, micro blood vessels 9
Rickettsial Diseases: 1-Typhus Group Epidemic Typhus Organism Rickettsia prowazekii Reservoir Human and flying squirrels Vector Lice borne Transmission Infected louse feces rubbed into broken skin Inc. period 8 days Distribution Worldwide Endemic Typhus Rickettsia typhi Rats and small rodent Flea borne Infected rubbed into broken skin 7-14 days worldwide flea feces Clinical Sudden onset of fever & headache Rashes which spares the palms, soles and face Delirium/ stupor Gangrene of hands or feet Gradual onset of Fever, Headache, Rash 10
Rickettsial Diseases:2- Spotted fever Group Rocky Mountain Spotted Fever Causative agent Rickettsia rickettsii Reservoir Dogs, rabbits, & wild rodents Vector Tick borne Transmission Wild and dog ticks bite Geographic distribution Mediterranean Sea Spotted Fever Rickettsia conorii Rodent Tick borne Tick bite Southern Europe, Africa, Middle East Fever Severe Headache Rash USA Clinical Fever Conjunctival redness Sever headache Rash on wrests, ankles, soles, palms initially and becomes more generalized later 11
Rickettsial Diseases: 3. Trench Fever Also called Five-day fever Causative agent:Bartonella quintana Reservoir: Human only Vector: Body human louse Transmission: Via feces of infected body lice being scratched into the skin Geographic distribution: Temperate regions and high elevations in the tropics, including South America Clinical Fever, Headache and Back pain It lasts for 5 days and recurs at 5 day intervals 12
Rickettsial Diseases: 4- Q Fever Coxiella burnetii is the causative agent of Q fever. Q from Query Geographic distribution: Worldwide Clinical: Fever, Headache, Viral-like pneumonia, No Rash Complication of Q fever are Hepatitis and Endocarditis It cangrow at pH 4.5 within phagolysosomes Coxiella burnetii is unique to the Rickettsiae Why??? Because like Gram-positive spore formers This endospore confers properties to the bacteria that differ from other Rickettsiae: This make the organism resistance to heat and drying Also extracellular existence 13
Q Fever Q fever is zoonotic and occupational disease Reservoir: Cattle, sheep and goats Non-arthropod vector transmission due to Coxiella burnetii grows in Ticks and Cattle The spores remain viable in; Dried tick feces deposited in cattle hide and Dried cow placentas following the birthing So Pneumonia occurred via inhalation of Spores via Airborne transmission of spore from hide or dried placenta or Via consumption of spore contaminated unpasteurized milk 14
Laboratory diagnosis Specimen: Blood and/or autopsy (Tissue) Staining Gram stain: gram negative coocobacilli (poorly stain) Giemsa stain: purple Isolation: difficult and dangerous The organism can be inoculated into tissue culture and grown over 4-7 days but this is very hazardous to personnel Serodiagnosis 1. Complement Fixation test (CFT) Complement Complement Ag-Ab Ag + Ab No lysis Ag-Ab Indicator system RBCs-anti-RBCs If the complement is free Indicator system RBCs-anti-RBCs Ag-Ab Lysis + 15
Laboratory diagnosis Indirect Immuno-fluorescence reaction (IIFR) Rckettsial antigen + Patient s serumn Ag-Ab complex Add anti-antibody (Fluorescence) Ab-F Result in Ag-Ab-Ab-F which detected under fluorescence microscope The use of immunofluorescent antibodies to examine a biopsy can be diagnostic 3. Weil-Fleix Reaction Some Rickettsia share antigenic characteristics with non-motile Proteus vulgaris strain P. vulgaris strains that share these common antigens are designated OX-2, OX- 19, OX-K This is done by mixing patient s serum (Antibody) and P. vulgaris strains (Antigen) Agglutination means positive test Results are shown in the Table 2. 16
Weil-Fleix Reaction Disease Weil-Fleix OX-19 OX-2 OX-K - Rocky Mountain spotted fever Mediterranean Sea fever + + + + - Rickettsial pox - - - - - Epidemic typhus Endemic typhus + + - - Trench fever - - - Q fever - - - 17
Control Sanitary: Arthropod and rodent control Immunological: No vaccines are currently available Chemotherapeutic: Tetracycline or chloramphenicol are drugs of choice 18
Chlamydiae Chlamydia is extremely tiny Gram-negative cocci bacteria, non-motile Have rigid cell wall Have outer membrane & Cytoplasmic membrane Lacking PDG and muramic acid Basophilic because stained blue by Giemsa stain Elementary bodies stain purple Reticulate body stain blue Inclusion body stain dark purple All share common complement fixing antigen 19
Special Growth developmental Cycle Elementary body Infects host epithelial cell Taken by endocytosis Reticulate body Formed 1-2 hr latter Larger than EB Divided by Binary fission Inclusion body Aggregates of small particles Formed within 24-48 hrs Host cell rupture releasing EB Infects again new host cell 20
Characteristics of elementary and reticulate bodies of Chlamydia ELEMENTARY BODY (EB) RETICULATE BODY (RB) Size 0.3 um (300 nm) RNA:DNA content = 1.1 Infectious Adapted for extracellular survival Hemagglutinin present Induces endocytosis Metabolically inactive Size 0.5 - 1.0 um (500-1000 nm) RNA:DNA content = 3.1 Not infectious Adapted for intracellular growth Hemagglutinin absent Does not induce endocytosis Metabolically active 21
Classification and Differentiation of Chlamydiae Subgroup A Subgroup B Mammalian parasites Compact inclusions Transmitted by contact Glycogen synthesized Folates synthesized (Sensitive) Sensitive to D-cycloserine Restricted host range Chlamydia trachomatis Infects non-ciliated epithelial cells (EYE and GENITAL) Bird parasites Diffuse inclusions Transmitted by inhalation Glycogen not synthesized Folates not synthesized (resistant) Resistant to D-cycloserine Broadening of host range Chlamydia psittaci Chlamydia pneumoniae Both infect LUNG columnar 22
SubgroupA: Chlamydia trachomatis Three biovars (biological variants): 1. Biovar Trachoma (15 Serologic types (A-K) A, B, Ba, C, D, Da, E, F, G, H, I ,Ia, J, Ja, K Serotypes A, B & C cause Trachoma Serotypes D-K cause inclusion conjunctivitis (Newborn), Non-Gonococcal Urethritis, Cervicitis, Infant pneumonia 2. Biovar lymphogranuloma venereum, LGV (4 serologic types) (L1, L2, L3,L4) 3. Biovar mouse Infects human non-ciliated columnar epithelial cells: Eye and Genitals Except Biovar mouse 23
a. Trachoma Severe form of chronic conjunctivitis Caused by C. trachomatis biovar Trachoma Serotypes A, B & C Transmission occurs by hand-to-hand transfer of infected secretions to eye by infected articles (Towels) Can be also transmitted by droplets, contaminated clothing, flies and by passage through an infected birth canal Infections occur most commonly in children Incubation period of 5 to 12 days 24
a. Trachoma Conjunctivitis, pink eye, Eye discharge, Swollen eyelids, Swelling of lymph nodes in front of the ears, corneal ulcer Producing scarring and deformity of the eyelids and corneal vascularization and opacities which may lead to blindness Blindness develops slowly over 10-15 years Occurs worldwide primarily in areas of poverty & overcrowding 500 million people are infected worldwide 7 - 9 million people are blind as a consequence 25
b. Inclusion conjunctivitis Collection of initial bodies in cytoplasm of conjunctival cells STD (Sexual Transmitted Disease) caused by C. trachomatis biovar Trachoma Serotypes D-K Infection derives from mother to neonates during birth Mucopurulent yellow discharge and swelling of eyelids Develops 5-14 days after birth Newborns are given Erythromycin eye drops prophylactically 26
c. Infant pneumonia Spread of Biovar Trachoma serotypes D-K through nasolacrimal duct Common in babies Develops between 4-11 weeks of life Initially, the baby develops upper respiratory symptoms followed by rapid breathing, cough and respiratory distress Diagnosed by presence of Chlamydial anti-IgM and/or demonstration of C. trachomatis in clinical specimen Treated with oral erythromycin 27
d. Urethritis (Male/Female) Caused by C. trachomatis Biovar Trachoma Serotypes D-K Urethritis One cause of Non-Gonococcal Urethritis (NGU) NGU are most common caused by C. trachomatis & U. urealyticum STD and Majority (>50%) asymptomatic Symptoms : mucoid or clear urethral discharge, dysuria Incubation period unknown (5-10 days in symptomatic infection) Clinically, no difference between NGU and gonococcal urethritis Urethritis usually occurs as mixed infections Empirical therapy for urethritis Single dose of ceftriaxon (against Gonococci) followed by days course of doxycycline or azithromycin (against NGU agents) 28
e. Cervicitis and Pelvic Inflammatory Disease (PID) Cervicitis Majority (70%-80%) are asymptomatic Local signs of infection, when present, include: Mucopurulent endocervical yellow discharge Edematous cervical ectopy with erythema and friability Infection can spread upwards to involve uterus, fallopian tubes (Salpingitis) and ovaries PID develops abnormal vaginal discharge or uterine bleeding, pain with sexual intercourse, nausea , vomiting and fever The most common symptom is lower abdominal pain Infection by both N. gonorrhoeae & C. trachomatis is called PID Treated by ceftriaxon followed by 14-days doxycycline 29
f. Lymphogranuloma Venereum (LGV) STD Caused by C. trachomatis biovar lymphogranuloma venereum L1, L2, L3 serotypes Starts with painless papule or ulceration on the genitals that heal spontaneously The bacteria migrate to regional lymph nodes which enlarge over the next 2 months These nodes become increasingly tender and may break open and drain pus Fever, skin rash, nausea, and vomiting are often found 30
Lab diagnosis Specimen: Sputum, Conjunctival scrapping, urethral discharge or pus in LGV Satin: Giemsa s stain Culture Cell culture treated with cycloheximide Non-culture tests Nucleic Acid Amplification Tests (NAATs) Non-Nucleic Acid Amplification Tests (Non-NAATs) Serology (Complement Fixation Test) 31
Subgroup B: C. psittaci It infects > 130 species of birds It is the causative agent of; Psittacosis (parrots; parrot fever) or Ornithosis (Pigeons, chicken, ducks and turkey) Occupational disease for poultry workers Zoonotic disease (animal diseases) Infection occurred by inhalation of respiratory discharge, feather or contaminated fecal material of birds Occurs after 1-3 weeks after exposure Infection results in atypical pneumonia 32
Subgroup B: C. pneumoniae First recognized in 1983 as a respiratory pathogen, after isolation from a student with pharyngitis Pneumonia or bronchitis, gradual onset of cough with little or no fever. Less common presentations are pharyngitis, laryngitis, and sinusitis Person-to-person transmission by respiratory secretions All ages at risk but most common in school-age children 33
Mycoplasma & Ureplasma Smallest free-living organisms (150-250 nm) Pass through some bacterial filters Lack of a cell wall Three layer membranes Outer and inner: proteins and saccharide Middle: 1/3 cholesterol Multiple shapes: round, pear shaped & even filamentous Require complex media containing sterol Require sterols for growth and for membrane synthesis Grow slowly (3 weeks) by binary fission and produce "fried egg" or T strain (tiny strain) colonies on agar plates 34
Mycoplasma Mycoplasmas are spherical to filamentous cells with no cell walls. Not affected by Penicillin or other Cell wall acting antibiotics. The mycoplasmas are facultative anaerobes, except for M. pneumoniae, which is a strict aerobe. Thus, they can assume multiple shapes including round, pear shaped and even filamentous. The mycoplasmas grow slowly by binary fission and produce "fried egg" colonies on agar plates The mycoplasma all require sterols for growth and for membrane synthesis
Two genera that infect humans: Mycoplasma and Ureaplasma They belong to Mycoplasmataceae There are many species of mycoplasmas Only four are recognized as human pathogens; 1. Mycoplasma pneumoniae Upper respiratory tract disease, Tracheobronchitis, atypical pneumonia 2. Mycoplasma hominis Pyelonephritis, pelvic inflammatory disease, postpartum fever 3. Mycoplasma genitalium Nongonococcl urethritis (NGU) 4. Ureaplasma urealyticum NGU and may play a role in male fertility Isolation pathogen cultured in pH 6.0 media Requires 10% urea for growth 36
Pathogenesis Adherence factors Adherence proteins are one of the major virulence factors Adhesin localizes at tips of the cells and binds to sialic acid residues on host epithelial cells Toxic Metabolic Products Intimate association provides an environment in which toxic metabolic products accumulate and damage host tissues Products of metabolism : hydrogen peroxide and superoxide -- oxidize host lipids Inhibit host cell catalase Immunopathogenesis M. pneumoniae is a superantigen Activate macrophages and stimulate cytokine production and lymphocyte activation Host factors contribute to pathogenesis 37
M. pneumoniae Need 10-20% Serum to culture in pH 7.8-8.0 Pathogenesis: P1 protein, capsule and saccharide Spread by close contact via aerosolized droplets Incubation period: 1-3 weeks Cause tracheobronchitis, primary atypical pneumonia Fever, headache, sore throat and cough Initially cough is non-productive but occasionally paroxysmal Antibodies play a role in controlling infection, particularly IgA Delayed type hypersensitivity 38
