Medical Microbiology: Chlamydia, Mycoplasmas, Rickettsia (Week 9) PDF

Medical Microbiology Miscellaneous group (Chlamydia, Mycoplasmas, Rickettsia) Presented by Ass. Prof./ Sahar Mandour Department of Microbiology and Immunology Faculty of Pharmacy Deraya University  Character of mis...

Medical Microbiology Miscellaneous group (Chlamydia, Mycoplasmas, Rickettsia) Presented by Ass. Prof./ Sahar Mandour Department of Microbiology and Immunology Faculty of Pharmacy Deraya University  Character of miscellaneous group (Mycoplasma, Chlamydia, Rickettsia) [[ They have properties common to both bacteria and viruses. Viral character: 1. Smaller in size than typical bacteria such as Mycoplasma. 2. They are either obligate intracellular such as Chlamydia, Rickettsia or facultative intracellular such as Mycoplasma. 3. Wall-less form (Cell wall deficient bacteria) such as Mycoplasma. 4. Grow in tissue culture Chlamydia, Rickettsia 5. Not stained by Gram stain, pleomorphic such as Rickettsia, Mycoplasmas Bacterial characters: 1. Have DNA, RNA 2. Multiplication by binary fission. 3. Rigid cell wall similar to Gram -ve bacteria except Mycoplasma. 4. Have ribosomes. 5. Contain plasmid 6. Have its own metabolic active enzymes 7. Sensitive to antibiotics (by inhibition of protein synthesis).  (I). Mycoplasmas Atypical pneumonia, Genital infection General features: 1. They are the smallest free-living bacteria 0.1 μm (100 nm). 2. Wall-less organisms absence of a cell wall. 3. Consequently, it stain poorly with Gram stain, pleomorphic 4. Resist e.g. penicillin and cephalosporins. 5. It is the only bacterial membrane that packed with cholesterol, a sterol usually found in eukaryotic cell membranes e.g. fungal cells. 5. Commensal in oral cavity and genital tract. 6. Mycoplasmas can be grown in the on artificial media. 7. They have complex nutritional requirements including several lipids in their cytoplasmic membrane. 8. They grow slowly and require at least 1 week to form a visible colony (seen by microscope) as fried egg appearance.  Mycoplasma pneumoniae M. pneumoniae is the most common type of atypical pneumonia. Mode of transmission: by respiratory droplets. ▪ The organism is pleomorphic, which serve as the point of attachment to the respiratory epithelium. ▪ Stained by Giemsa stain. ▪ Facultative anaerobes, ▪ Growth on enriched media contain serum, sterol, nucleic acid. Grow better at 10% CO2. Virulence factor: 1- Protein P1 for adhesion. 2- M. pneumoniae not invade respiratory mucosa but inhibit ciliary motion and necrotizing the epithelium. 3- Produce hydrogen peroxide resulting in lysis to host cells. Clinical findings: cannot be isolated on routine media in the diagnostic lab. or that the disease does not resemble pneumococcal pneumonia. immunity to M. pneumoniae is incomplete, and second periods of disease can occur. Symptoms: The onset of is gradual, mild fever, usually beginning with a nonproductive or dry cough and sore throat. Small amounts of whitish, non-bloody sputum are produced. Fever, headache, malaise, and myalgia are pronounced. The disease resolves spontaneously in 10-14 days. Complication: During infection, autoantibodies are produced against red cells (0) at 4ᵒC (cold agglutinins) and brain, lung, and liver cells. These antibodies may be the source of the extrapulmonary manifestation of infection, such as ischemia, “cold agglutinin hemolytic anemia”. It is estimated that only 10% of all community acquired pneumonia. Laboratory diagnosis of Mycoplasma pneumoniae (Atypical pneumoniae): 1. Specimen: Sputum, throat swab 2. Microscopic examination: small, pleomorphic (with limited value). 3. Culture character: (contain cholesterol to support cyto. membrane) Diagnosis is usually not made by culturing sputum samples; it takes at least 1-3 week for microscopical colonies to appear on Mycoplasma media showing black depressed center (Fried egg like). microscopic colonies. Fried egg like colonies 4. Serological test: i- Cold agglutinin are IgM autoantibodies against type O red blood cells that agglutinate these cells at 4ᵒC but not at 37ᵒC. the test is nonspecific; false- positive, titer of 1/128 or higher is indicative of recent infection. (complication: hemolytic anemia, ischemia when exposure to cold environment) ii- Complement fixation test: confirmatory test using specific antibody.  (II). Chlamydia species Trachoma, Genital infection, psittacosis, pneumonia General Character of Chlamydia: Chlamydia formerly classified as virus (250-400 nm) and known as bedsonia. They have a variety of metabolic enzymes that can liberate CO2 from glucose; however, they lack the mechanism for the production of ATP; thus, they are obligate intracellular where the host cell supply the energy rich intermediate. Closely related to Gram-negative bacteria weakly stained with Gram stain, stained with Giemsa or Castaneda stain. Divide by binary fission. They posses DNA, RNA, and ribosomes, rigid cell wall but lacking muramic acid thus they resist the action of lysozyme and β-lactams. Growth cycle replication is by binary fission through the formation of: a) Elementary body: Small , inert, extracellular, infectious to the host cell. It is taken by endocytosis (similar to phagocytosis) into a vacuole. It has electron dense nucleoid. b) Reticulate body: Intracellular, large, metabolic active, replicating form. Formed one hour later, it is larger and devoid of electron dense nucleoid. Then it divides by binary fission within the vacuole forming. This replicative stage are seen only within host cells. C) Inclusion body: Aggregate of small particles formed within 24-48 hr. of infection within a membrane-bound vacuole which isolate the organism from the host cytoplasm, then rupture releasing elementary bodies that infects again new host cells. Pathogenesis: Transmission: ▪ It is the most common bacterial sexually transmitted diseases in humans ▪ and are the leading cause of infectious blindness worldwide. ▪ More common in women than man. ▪ Infection is usually chronic and the usually escape the intracellular destruction as it prevents the fusion of lysosomal granules to the phagosomes, also produces a heat labile protein toxin. ▪ Associated with law standard of living and poor personal hygiene.  (a). Chlamydia trachomatis 1). Ocular infection a)Trachoma: chronic keratoconjunctivitis (blinding eye disease): Eye infection caused by sero-types A, B, and C. It is endemic in Egypt. Transmitted by fingers, fomites, or flies eye to eye. 1. Characterized by conjunctivitis often mixed with bacteria, swelling of eyelid, lacrimation and mucopurulent discharge are characteristic. 2. Scaring of the eyelid 3. Pulls the eyelash into the eye followed by corneal opacity, blindness. 4. Chronic infection may result in scratching of the corneal ulceration and if not treated resulting in blindness over period of years Reiter's syndrome, also known as reactive arthritis, is the classic triad of (conjunctivitis, urethritis, and arthritis) occurring after an infection, particularly those in the urogenital or gastrointestinal tract. b). Inclusion conjunctivitis: caused by serotypes D-K. - Sexually transmitted disease usually infection is derived from mother during birth resulting in neonatal mucopurulent discharge without scar formation. - Auto infection for adults or swimming pool. Chlamydia trachomatis  2. Genital infection ▪ caused by serotypes D-K that are causes of sexually transmitted disease ▪ Usually, infection is derived from mother during birth resulting in neonatal mucopurulent discharge. ▪ In man cause non-gonococcal urethritis and\or epididymitis with purulent discharge revealing neutrophils without bacteria. ▪ In women cause urethritis, cervicitis and salpingitis (inflammation of fallopian tubes); which is often referred as pelvic inflammatory disease PID. ▪ Infection may accompany gonococcus, and persistence of symptoms after disappearance of gonococci by anti-gonococcal therapy indicates chlamydia. ▪ Non-gonococcal urethritis caused by C. trachomatis is said to occur more frequently in higher socioeconomic Groups, in contrast to gonorrhea, which is found predominately in lower socioeconomic groups. However, the 2 diseases commonly occur simultaneously in the same individual. ▪ PID: Pelvic inflammatory disease  3. Lymphogranuloma venereum (LGV) It is a sexually transmitted disease, more common in tropical regions. serotype L1,L2,L3. Symptoms: Primary stage: appearance of a small papule or vesicle on any part of the external genitalia or rectum. After 1-4 weeks. Healing within week. After 1-4 weeks from disappearance of papule. Spreading to lymphatic system and multiply in inguinal lymph nodes and enlarge. Secondary stage: Become painful, open fistula, discharge pus through multiple sinus tracts, if not treated: Tertiary stage: Healing of ulcer and scar formation. Obstruction of lymphatic vessels. Elephantiasis of genital organs. Infection leads to formation of antibodies and cell-mediated reactions but not to resistance to reinfection or elimination of organisms.  (b).Chlamydia psittaci Atypical pneumonia (psittacosis) ▪ Influenza like disease, with high mortality serotypes D-K ▪ The term atypical, means that a causative bacterium causing inflamed or swollen lung tissue only and not pus forming in alveoli, low grade fever and antibiotic resistant. Zoonotic disease transmitted by inhalation dust containing the dried feces of infected birds such as parrots, psittacosis, pigeon, ornithosis spread through nasolacrimal duct Infection is less common in adults. Laboratory diagnosis of: 1.Clinically 2.Specimen: conjunctival scrapping, eye discharge (Trachoma) Atypical pneumonia sputum, urethral discharge or pus in LGV. Stain: Giemsa stain to detect inclusion bodies (reticulate) blue in the cytoplasm. 2. Culture: Tissue cultures treated, Yolk sac inoculation 3. Skin test LGV only Fri test. 4. Serology: Ag detection ELISA, Immunofluorescent test 5. PCR Treatment: Drug of choice, erythromycin and tetracycline ointment. Prophylaxis of contacts.  (III). Rickettsiae Typhus, spotted fever, Q fever General character of Rickettsiae: ❑ All are small, obligate intracellular bacteria because they are unable to produce sufficient energy to replicate extracellular, resembling Gram- negative bacteria in cellular structure and division and lacks teichoic acid. ❑ All are pleomorphic (Cocci, rods or filamentous), found single or in pairs. ❑ Stained with Giemsa stain. ❑ All of them grow only in tissue culture or yolk sac of embryonated eggs. ❑ They contain various enzymes that could metabolize glucose intermediates. Transmitted through arthropod vector from animal or human reservoir except trench fever Coxiella burnetii (Q fever), which is transmitted by inhalation of aerosols, cattle milk, urine, and birth products. - Arthropods vector’s bite or feces (Ticks, Lice, Mites, Fleas) where the human body louse transmits the person to person. Disease: vasculitis (rash, oedema and hemorrhage) Typhus group rickettsiae usually grow in host cell cytoplasm. While spotted fever group rickettsiae usually grow in host cell nucleus. When a patient is bitten, the organism is ingested by the louse and multiplies in the gut epithelium. It is excreted in the feces of the louse during the act of biting the next person and auto-inoculated by the person while scratching the bite. All rickettsiae are transmitted to humans through arthropod vector from animal or human reservoir except Coxiella burnetii (Q fever), which is transmitted by inhalation of aerosols or cattle milk. Symptoms: ❖ All rickettsiae cause skin rash, fever, headache and malaise that may end in delirium and coma. Rash usually starts on hands and feet. Rash is due to hyperplasia and inflammation of vascular endothelium, disseminated intravascular coagulation (DIC), except Coxiella burnetii (Q fever), which cause atypical pneumonia and slow fever and hepatitis. ❖ All rickettsiae except Coxiella burnetii are very sensitive to antiseptics, dryness and heat. Coxiella survive dryness and resist pasteurization at 60 °C for 30 min. ❖ All rickettsiae are best treated by chloramphenicol or tetracycline; however, their growth is enhanced by sulfonamide and is inhibited by para- aminobenzoic acid (PABA). ❖ Rickettsiae spp. are classified on the basis of clinical features and immunological characters, and there is no cross immunity between different diseases. Laboratory diagnosis: 1) Weil-Felix reaction: -Heterophile agglutination. - Non-specific microagglutination reaction between serum of patient and proteus vulgaris strains (0X-2,0X-19 and 0X-K). - Reaction is due to sharing of O polysaccharide antigen in proteus and rickettsiae. 2). Complement fixation reaction: Using the specific rickettsial antigen. 3) Indirect immunofluorescence reaction: Using the specific rickettsial antigen.