Obligate Intracellular and Nonculturable Agents

Obligate Intracellular and Nonculturable Agents

• Chlamydia• Calymmatobacterium granulomatous• Rickettsia • Coxiella, and • Bartonella

Objectives

• To know the major diseases associated with each species of Chlamydia and their clinical presentation

• To know the mode of transmission for Chlamydia Rickettsia, Coxiella, and Bartonella.

• To know the appropriate cultures for detection of C. trachomatis.

• Clinical Diagnosis of the Chlamydiam, Rickettsia, Coxiella, and Bartonella

• To know the serological investigation

• 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

Important Species• C. trachomatis• C. pneumoniae• C. psittaci

Cultural CharactersGrow in:

• Tissue culture (McCoy cells)• Yolk sac of chicken embryo

CHLAMYDIA

Reproduction Cycle of Chlamydia

Attachment & Phagocytosis of EB

Continued multiplication & and reorganization of RB into EB.Development of a large Cytoplasmic inclusion

Release of EB

Extracellular InfectiousElementary Bodies (EB)

Development toReticulate Bodies (RB)

Multiplication of RB by binary fission

Multiplication stops

Human Cell

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

• 15 serotypes (A-L)

TransmissionThrough close personal contact like:• Sexual

• Passage through birth canal

• Finger to eye OR fomite to eye (Trachoma)

CHLAMYDIA TRACHOAMATIS

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 & orchitiso Cervicitis & Vaginitis• Salpingitis (5-30%)• Mucopurrulent vaginal dischargeo 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 canalo Inclusion Conjunctivitis

• Profuse mucopurrulent discharge 7-12 days after birtho 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 DIAGNOSISSpecimens from urethra, conjunctiva, sputum & cervix1. Microscopy Chlamydial “cytoplasmic inclusions” are detected by: • Giemsa staining• Immunofluorescence2. Cell Culture : McCoy cell line3. Nonculture • Enzyme immunoassay • Amplified Nucleic acid probes/amplification4. Sero-diagnosis (antibody detection) very limited

and problematic

TREATMENT• Tetracycline in adults• Erythromycin/Azithromycin in children

• 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 PNEUMONIAE

CHLAMYDIA PSITTACI

• A zoonotic respiratory disease• Natural reservoir : birdsTransmitted through inhalation of :• Respiratory secretions & • Dust from feces of infected birds• Common in poultry workersDisease : Pneumonia (Psittacosis), (ornithosis) ( parrot

fever)Diagnosis• Isolation of organism from sputum by tissue culture• Complement fixation test to detect specific AbsTreatment• Tetracycline in adults• Erythromycin/Azithromycin in children

Species Serovars

(Strains)

Modes of transmission

Diseases

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 Lymphogranul-oma venereum

LGV

C. psittaci Many Aerosal Psittacosis

C. pneumoniae TWAR Human to human Respiratory infection

Epidemiologic association between chlamydial species, strain, and diseases

Calymmatobacterium granulomatous

Causes GRANULOMA INGUINALE• Capsulated short Gram-negative rod• A STD with higher incidence in homosexualsClinical 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 enlargeTreatment : 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

Disease Organism Vector1. Rocky mountain R. rickttsii Ticks

Spotted fever

2. Epidemic typhus R. prowazeki Lice

3. Q fever C. burnetti None

(cattles, sheeps)

RICKETTSIA & COXIELLA : DISEASES

Clinical Features• History of arthropod vector bite• Acute onset of fever, myalgias, headache• Skin rashes due to vasculitis

Pathogenesis

• Rickettsiae infect the vascular endothelium and the primary lesion is vasculitis in which rickettsiae multiply in the endothelial lining the blood vessels

Bacteria infect vascular

endothelium

Enter cells by endocytosis

Multiply

within cell

Host cell lysisRelease of

rickettsia

Infection of

other cells

Vasculitis &Thrombosis

Blockade of small blood vessels & skin rashes

PATHOGENICITY 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.

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 7-10 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

Lab Diagnosis

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

• 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 assaysSerology is the most convenient and commonly used diagnostic tool Treatment of choice is tetracycline

Coxiella burnetii

• Serology• PCR • Tissue culture• Treatment

o Tetracyclineo Chloramphenicol

RICKETTSIA & COXIELLA : LAB DIAGNOSIS

Bartonella

Bartonella quintana: causes trench fever• History of louse contact, patient present

with fever, head ache relapsing fever and rash.

• Associated with alcoholismBartonella 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?