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Batterjee Medical College Batterjee Medical College Spirochetes Dr. Manal El Said Head of Medical Microbiology Department Batterjee Medical College Treponema pallidum Diseases Syphilis Characteristics • Spirochetes. • Not seen on Gram-stained organism is too thin. • Not cultured in vitro. smear Habitat and Transmission • Habitat is the human genital tract. • Transmission is by sexual contact • from mother to fetus across the placenta. because Batterjee Medical College Treponema pallidum Pathogenesis • Organism multiplies at site of inoculation and then spreads widely via the bloodstream. • Many features of syphilis are attributed to blood vessel involvement causing vasculitis. • Primary (chancre) and secondary lesions heal spontaneously. • Tertiary lesions consist of gummas (granulomas) in bone, muscle, and skin, aortitis, or central nervous system inflammation. Batterjee Medical College Treponema pallidum • In primary syphilis, the Spirochetes multiply at the site of inoculation and a local, nontender ulcer (chancre) usually forms in 2 to 10 weeks. The ulcer heals spontaneously, but Spirochetes spread widely via the bloodstream (bacteremia) to many organs. • One to three months later, the lesions of secondary syphilis occur & appear as a maculopapular rash, on the palms and soles, or as moist papules on skin and mucous membranes . Moist lesions on the genitals are called condylomata lata. These lesions are rich in Spirochetes and are highly infectious, but they also heal spontaneously. Constitutional symptoms of secondary syphilis include lowgrade fever, malaise, anorexia, weight loss, headache, myalgias, and generalized lymphadenopathy. There may be internal organ involvement (meningitis, nephritis, hepatitis, etc). • Tertiary syphilis may show granulomas (gummas), especially of skin and bones. central nervous system involvement or cardiovascular lesions In tertiary lesions, treponemes are rarely seen. • T. pallidum also causes congenital syphilis. The organism is transmitted across the placenta, after the third month of pregnancy, and fetal infection can occur. Skin and bone lesions are common, as is hepatosplenomegaly. Unless the disease is treated promptly, stillbirth or multiple fetal abnormalities occur. Batterjee Medical College Treponema pallidum Laboratory Diagnosis • Seen by darkfield microscopy or immunofluorescence. • Serologic tests important: VDRL (or RPR) is nontreponemal (nonspecific) test used for screening; FTA-ABS is the most widely used specific test for Treponema pallidum. • Antigen in VDRL is beef heart cardiolipin; antigen in FTA-ABS is killed T. pallidum. • VDRL declines with treatment, whereas FTA-ABS remains positive for life. Batterjee Medical College Treponema pallidum Treatment • Penicillin is effective in the treatment of all stages of syphilis. • In primary & secondary syphilis, use benzathine penicillin G because T. pallidum grows slowly, so drug must be present for a long time. • There is no resistance. Prevention • Benzathine penicillin given to contacts. • No vaccine is available. Batterjee Medical College Borrelia burgdorferi Diseases Lyme disease Characteristics •Spirochetes. •Gram stain not useful. •Can be cultured in vitro, but not usually done. Batterjee Medical College Borrelia burgdorferi Habitat and Transmission • The main reservoir is the white-footed mouse. • Transmitted by the bite of ixodid ticks • Very small nymph stage of ixodid tick (deer tick) is most common vector. • Tick must feed for at least 24 hours to deliver an infectious dose of B. burgdorferi. ixodes tick Batterjee Medical College Borrelia burgdorferi Pathogenesis • Organism invades skin, causing a rash called erythema migrans. • It then spreads bloodstream via to the involve primarily the heart, joints, and central nervous system. characteristic red, ring shaped skin lesion with central clearing that first appears at site of tick bite Batterjee Medical College Borrelia burgdorferi Laboratory Diagnosis • Diagnosis made serologically, i.e., by detecting IgM antibody. • Confirm positive test with Western blot assay. Batterjee Medical College Borrelia burgdorferi Treatment Doxycycline for early stages; penicillin G for late stages. Prevention • Avoid tick bite. • Can give doxycycline or amoxicillin to people who are bitten by a tick in endemic areas. Batterjee Medical College Borrelia recurrentis • Causes relapsing fever. • Transmitted by human body louse. • It has rapid antigenic changes, which account for the relapsing nature of disease. • It is due to programmed rearrangements of bacterial DNA encoding surface proteins. Batterjee Medical College Leptospira interrogans Diseases Leptospirosis Characteristics • Spirochetes that can be seen on microscopy but not light microscopy. • Can be cultured in vitro. darkfield Habitat and Transmission • Habitat is wild and domestic animals. • Transmission is via animal urine. • In the United States, transmission is via dog, livestock and rat urine. Batterjee Medical College Leptospira interrogans Pathogenesis • Two phases: - initial bacteremic phase -subsequent immunopathologic meningitis. phase with Batterjee Medical College Leptospira interrogans Laboratory Diagnosis • Darkfield microscopy and culture in vitro are available but not usually done. • Diagnosis usually made by serologic testing for antibodies in patient's serum. Batterjee Medical College Leptospira interrogans Treatment •Penicillin G. •There is no significant antibiotic resistance. Prevention • Doxycycline effective for short-term exposure. • Vaccination of domestic livestock and pets. • Rat control. Batterjee Medical College Rickettsiae Dr. Manal El Said Head of Medical Microbiology Department Batterjee Medical College Rickettsia rickettsii Diseases Rocky Mountain spotted fever • Fever, severe headache, myalgias, & prostration. • Typical rash, which appears 2 to 6 days later, begins with macules that progress to petechiae. • Rash appears first on hands & feet & then moves inward to trunk. • In addition to headache, other profound central nervous system changes such as delirium & coma can occur. • Disseminated intravascular coagulation, edema & circulatory collapse may ensue in severe cases. Batterjee Medical College Rickettsia rickettsii Characteristics • Obligate intracellular parasites. • Not seen well on Gram-stained smear. • Antigens cross-react with OX strains of Proteus vulgaris (Weil-Felix reaction). Batterjee Medical College Rickettsia rickettsii Habitat and Transmission • Dermacentor (dog) ticks are both vector & main reservoir. • Transmission is via tick bite. • Dogs & rodents can be reservoirs. ixodes tick Pathogenesis • Organism invades endothelial lining of capillaries, causing vasculitis. • No toxins or virulence factors identified. Batterjee Medical College Rickettsia rickettsii Laboratory Diagnosis • Detecting antibody in serologic tests such as the ELISA test. • Weil-Felix test is no longer used. • Stain and culture rarely done. Treatment Tetracycline. Prevention • Protective clothing & prompt removal of ticks. • Tetracycline effective in exposed persons. • No vaccine is available Batterjee Medical College Rickettsia prowazekii Diseases Louse-borne epidemic typhus • Typhus begins with sudden onset of chills, fever, headache, and other influenzalike symptoms • Maculopapular rash begins on trunk & spreads peripherally. • Rash becomes petechial & spreads over entire body but spares face, palms, & soles. • Signs of severe meningoencephalitis, including delirium & coma • In untreated cases, death occurs from peripheral vascular collapse or from bacterial pneumonia. Batterjee Medical College Rickettsia prowazekii Characteristics Same as R. rickettsii. Habitat and Transmission • Humans are the reservoir, and transmission is via the bite of the human body louse. Batterjee Medical College Rickettsia prowazekii Pathogenesis No toxins or virulence factors known. Laboratory Diagnosis Serologic tests for antibody in patient's serum. Treatment A tetracycline, such as doxycycline. Prevention • A killed vaccine is used in the military but is not available for civilian use. Batterjee Medical College Coxiella burnetii Dr. Manal El Said Head of Medical Microbiology Department Batterjee Medical College Coxiella burnetii Diseases Q fever. • Main organ involved in Q fever is lungs. • It begins suddenly with fever, severe headache, cough, and other influenzalike symptoms. • Hepatitis is frequent enough that combination of pneumonia & hepatitis should suggest Q fever. • Rash is rare • Q fever is acute disease &recovery is expected even in absence of antibiotic therapy. • Chronic Q fever characterized by life-threatening endocarditis occurs. Batterjee Medical College Coxiella burnetii Characteristics • Obligate intracellular parasites. • Not seen well on Gram-stained smear. Habitat and Transmission • Habitat is domestic livestock. • Transmission is by inhalation of aerosols of urine, feces, amniotic fluid, or placental tissue. • The only rickettsia not transmitted to humans by an arthropod. Batterjee Medical College Coxiella burnetii Pathogenesis No toxins or virulence factors known. Laboratory Diagnosis • Diagnosis usually made by serologic tests. • Weil-Felix test is negative. • Stain and culture rarely done. Treatment Tetracycline. Prevention • Killed vaccine for persons in high-risk occupations Batterjee Medical College Mycoplasmas Dr. Manal El Said Head of Medical Microbiology Department Batterjee Medical College Mycoplasma pneumoniae Diseases "Atypical" pneumonia. Characteristics • Smallest free-living organisms. • Not seen on Gram-stained smear because they have no cell wall, so dyes are not retained. • The only bacteria with cholesterol in cell membrane. • Can be cultured in vitro. Batterjee Medical College Mycoplasma pneumoniae Habitat and Transmission • Habitat is the human respiratory tract. •Transmission is via respiratory droplets. Pathogenesis • No endotoxin because there is no cell wall. • Produces hydrogen peroxide, which may damage the respiratory tract. Batterjee Medical College Mycoplasma pneumoniae Laboratory Diagnosis • Gram stain not useful. • Can be cultured on special bacteriologic media but takes at least 10 days to grow, which is too long to be clinically useful. • Positive cold-agglutinin test is presumptive evidence. • Complement fixation test for antibodies to Mycoplasma pneumoniae is more specific. Batterjee Medical College Mycoplasma pneumoniae Treatment Erythromycin or tetracycline. Prevention No vaccine or drug is available