Obligate Intracellular and Nonculturable Agents
Obligate Intracellular and Nonculturable Agents • • • • •
Chlamydia Calymmatobacterium granulomatous Rickettsia Coxiella, and Bartonella
Objectives
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To know the major diseases associated with each species of Chlamydia and their clinical presentation
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To know the mode of transmission for Chlamydia Rickettsia, Coxiella, and Bartonella.
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To know the appropriate cultures for detection of C. trachomatis.
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Clinical Diagnosis of the Chlamydiam, Rickettsia, Coxiella, and Bartonella
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To know the serological investigation
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Antimicrobial therapy
CHLAMYDIA •Obligate intracellular bacteria • Have ribosomes like bacteria • Are metabolically deficient Morphology • Small rounded organism, multiply by binary fission • Cell wall consists of inner & outer membranes. • Elementary body (EB) has an outer membrane similar to that of many Gram-negative bacteria. •The most prominent part of this membrane is Major Outer Membrane Protein (MOMP). •The MOMP is a transmembrane protein that contain species-specific epitope that can be known by monoclonal antibodies
CHLAMYDIA Important Species • C. trachomatis • C. pneumoniae • C. psittaci
Cultural Characters Grow in: • Tissue culture (McCoy cells) • Yolk sac of chicken embryo
Reproduction Cycle of Chlamydia Human Cell Extracellular Infectious Elementary Bodies (EB)
Development to Reticulate Bodies (RB) Attachment & Phagocytosis of EB
Release of EB
Multiplication stops Continued multiplication & and reorganization of RB into EB. Development of a large Cytoplasmic inclusion
Multiplication of RB by binary fission
CHLAMYDIA PATHOGENESIS • Infect epithelial cells of mucous membranes & lungs Virulence is due to: • Resistance to phagocytic killing • Heat-labile toxin • Competition with host cell for nutrients • Host’s immune response as inflammation & tissue destruction
CHLAMYDIA TRACHOAMATIS • 15 serotypes (A-L) Transmission Through close personal contact like: • Sexual • Passage through birth canal • Finger to eye OR fomite to eye (Trachoma)
CHLAMYDIA TRACHOAMATIS DISEASES 1. Trachoma • Trachoma is a chronic follicular inflammation of the eye lid and increased vascularization of the corneal conjunctiva followed by scarring of eye lids and cornea • Caused by serotypes A, B, Ba & C • One of the leading causes of blindness in developing countries with dry & hot weather
CHLAMYDIA TRACHOAMATIS DISEASES 2. Genital Tract Infections (Serotypes D-K) o Non-gonococcal urethritis in men • A common disease • Mucopurrulent urethral discharge • May progress to epidydmitis & orchitis o Cervicitis & Vaginitis • Salpingitis (5-30%) • Mucopurrulent vaginal discharge o Pelvic Inflammatory Disease (PID) • May lead to secondary infertility
CHLAMYDIA TRACHOAMATIS DISEASES 3. Neonatal Infections (Caused by serotypes D-K) • Acquired from mother’s birth canal o Inclusion Conjunctivitis
• Profuse mucopurrulent discharge 7-12 days after birth
o Pneumonia
4. Lymphogranuloma Venereum (LGV)
• Caused by serotypes L1, L2 & L3 • A STD with lesions on genitalia & LNs (buboes)
5. Reiter’s Disease
• An autoimmune disease caused by Abs formed against C. trachomatis which cross react with Ags on cells of urethra & joints
CHLAMYDIA TRACHOAMATIS LAB DIAGNOSIS Specimens from urethra, conjunctiva, sputum & cervix 3. Microscopy Chlamydial “cytoplasmic inclusions” are detected by: • Giemsa staining • Immunofluorescence
7. Cell Culture : McCoy cell line 8. Nonculture • Enzyme immunoassay • Amplified Nucleic acid probes/amplification 11.Sero-diagnosis (antibody detection) very limited and problematic TREATMENT • Tetracycline in adults • Erythromycin/Azithromycin in children
CHLAMYDIA PNEUMONIAE • A cause of walking pneunoniae • Also known as TWAR (TW – Taiwan & AR – acute respiratory) • Cause atypical pneumonia like Mycoplasma pneumoniae • Infection with C. pneumoniae has been established as a risk factor for Guillain-Barre syndrome. Treatment • Tetracycline in adults • Erythromycin/Azithromycin in children
CHLAMYDIA PSITTACI • A zoonotic respiratory disease • Natural reservoir : birds Transmitted through inhalation of : • Respiratory secretions & • Dust from feces of infected birds • Common in poultry workers Disease : Pneumonia (Psittacosis), (ornithosis) ( parrot fever) Diagnosis • Isolation of organism from sputum by tissue culture • Complement fixation test to detect specific Abs Treatment • Tetracycline in adults • Erythromycin/Azithromycin in children
Epidemiologic association between chlamydial species, strain, and diseases Species Serovars Modes of Diseases transmission (Strains) C. Trachomatis
A,B,Ba, C
Hand to eye, fomites, flies
Trachoma
C. trachomatis
B, Ba, D-K
Sexual, hand to eye
Inclusion conjunctivitis, genital infection
C. trachomatis
L1, L2, L3
Sexual
Lymphogranuloma venereum LGV
C. psittaci
Many
Aerosal
Psittacosis
C. pneumoniae
TWAR
Human to human
Respiratory infection
Calymmatobacterium granulomatous Causes GRANULOMA INGUINALE • Capsulated short Gram-negative rod • A STD with higher incidence in homosexuals Clinical Features • Initially papules appear on external genitalia which ulcerate and extend widely – ulcer formation • Base of ulcer is “BEEFY”; spreads by contact so is known as “KISSING ulcers” • LN may enlarge Treatment : Tetracycline
RICKETTSIA • • • • •
Are obligate intracellular parasites Rapidly loss infectivity outside host cell Growth slow compared to bacteria Have animal reservoirs (zoonotic diseases) Humans are accidental host in most cases
Transmission • Maintained in arthropods like ticks, lice, fleas & mites • Usually transmitted to human by bite of vector Diseases • Spotted fever group: in North and South America, causes Rocky mountain spotted fever (RMSF) • Epidemic typhus group In Asia, Africa and causes epidemic typhus
RICKETTSIA & COXIELLA : DISEASES Disease
Organism
Vector
1. Rocky mountain R. rickttsii Spotted fever
Ticks
2. Epidemic typhus R. prowazeki
Lice
3. Q fever
C. burnetti
Clinical Features • History of arthropod vector bite • Acute onset of fever, myalgias, headache • Skin rashes due to vasculitis
None (cattles, sheeps)
Pathogenesis • Rickettsiae infect the vascular endothelium and the primary lesion is vasculitis in which rickettsiae multiply in the endothelial lining the blood vessels
PATHOGENICITY OF RICKETTSIA Bacteria infect vascular endothelium
Blockade of small blood vessels & skin rashes
Enter cells by endocytosis
Vasculitis & Thrombosis
Multiply within cell
Infection of other cells
Host cell lysis
Release of rickettsia
Clinical picture Early signs and symptoms • fever, nausea, vomiting, severe headache, muscle pain, lack of appetite. • The rash first appears 2-5 days • Most often it begins as small, flat, pink, non-itchy spots (macules) on the wrists, forearms, and ankles. These spots turn pale when pressure is applied and eventually become raised on the skin.
• Later Signs and Symptoms • Late (petechial) rash on palm and forearm • abdominal pain, joint pain, diarrhea.
Lab Diagnosis Indirect immunoflourescence assay (IFA) Other well assays including ELISA, latex agglutination.. •Most patients demonstrate increased IgM titers by the end of the first week of illness. • Diagnostic levels of IgG antibody generally do not appear until 710 days after the onset of illness. • IgG antibodies are more specific and reliable since other bacterial infections can also cause elevations in riskettsial IgM antibody titers. PCR which can detect DNA present in 5-10 rickettsiae in a sample, this procedure is more specific than antibody-based methods
IFA reaction of a positive human serum on Rickettsia rickettsii grown in chicken yolk sacs, 400X
Gimenez stain of tick hemolymph cells infected with R. rickettsii
Coxiella burnetii • • • • •
Causative agent of Q fever Zoonotic disease for cattle sheep and goats In infected animals organisms are shed in urine, faces, milk and birth product Human are infected by inhalation of the contaminated aerosols IP 2-4 weeks
Clinical manifestaions: • fever, • Atypical pneumoniae, • Hepatitis, • Endocarditis, bone and CNS infection Morphology • Coccobacilli • Stained poorly with Gram-staining • Growth on tissue cultures • Detected by using a direct immunofluorencet assays Serology is the most convenient and commonly used diagnostic tool Treatment of choice is tetracycline
RICKETTSIA & COXIELLA : LAB DIAGNOSIS • • • •
Serology PCR Tissue culture Treatment o Tetracycline o Chloramphenicol
Bartonella Bartonella quintana: causes trench fever • History of louse contact, patient present with fever, head ache relapsing fever and rash. • Associated with alcoholism Bartonella hensela: causes Cat Scratch Fever (CST) • Common in children • Persistent lymphadenitis is the usual finding • AID and other immunocompromised states are associated with more severe infections
Case study A 7-day-old newborn was brought by his grandmother to the emergency department of a large city hospital. He had been discharged 3 days after birth. On admission he had fever of 390C, loss of appetite, perfuse yellow discharge from the right eye, and general irritability. Past medical history revealed the mother to be a 17-year-old intravenous drug abuser with no prenatal care, who had a vaginal delivery in the parking lot of a local hospital. The eye discharge was cultured for a variety of organisms and was diagnosed.
Learning assessment questions • What organisms should be considered as a possible causes of neonatal conjunctivitis? • What stain should be performed on the discharge or conjunctival scraping for microscopy examination? • For the infant described in the case study, what other clinical conditions could be due to the causative organisms? • What are the more common sites of infection in newborns infected with this organism? • What STD is caused by C. trachomatis serotypes L1, L2, and L3? • Which chlamydia species is associate Guillain-Barre syndrome? • What is psittacosis? • How is this condition usually diagnosed?