MicroPara Week 4 – Spirochetes, Miscellaneous Bacteria, Rickettsiae/Chlamydia, Mycology & Virology

Vocabulary flashcards cover key pathogens, diseases, structures, diagnostics, and treatments from Week 4 Microbiology lectures to aid exam review.

Spirochete

Gram-negative, helically coiled, motile bacterium that moves via axial filaments and may be facultatively anaerobic or aerobic

Axial filament

Most distinctive property of spirochetes, responsible for motility

Pathogenic Spirochetes

1. TREPONEMA

● T. pallidum subsp. pallidum

● T. pallidum subsp. pertenue

2. BORRELIA

● B. recurrentis

● B. burgdorferi

3. LEPTOSPIRA INTERROGAN

Spirals Characteristics

Gram negative

Motile, slender, rigid organism

Amphitrichous flagella

Microaerophilic

Pathogenic Spirals

Camplyobacter Jejuni and Spirillum Minus

Characterisitcs of Trepanoma

Microscopy: Thin, spiral organisms with 3 axial

filaments

Difficult to stain

Transverse fission

Best demonstrated in darkfield microscopy

Treponema pallidum subsp. pallidum

The causative agent of syphilis

Microaerophilic

It is killed rapidly at 42 °C

Remains viable in whole blood or plasma for at

least 24 hours

It can cross the placenta and an intact mucous

membrane, and spread throughout the body

Generation time: 30 hours

Syphilis

Also known as the French Disease, Italian Disease, The Great Pox, or the “The Great Imitator”

Transmission of Syphilis

Sexual contact, vertical

transmission, skin contact with active lesion,

transfusion of fresh blood, injuries from

contaminated needle stick

Symptoms of Syphilis

Chancre, fever, sore throat, headache,

rashes, and gummas of the skin

Primary syphilis

It is characterized by the appearance of

hunterian or hard chancre, which is an

infectious primary lesion that is painless and

usually seen on the genitalia

It develops 10 to 90 days after infection

No systemic signs or symptoms are evident

in this stage

Stage 1: Painless sores form on genitals,

rectum, or mouth

Secondary syphilis

It develops 2 to 10 weeks after primary

syphilis

Systemic involvement with the following

manifestations: Fever, sore throat,

headache, generalized lymphadenopathy,

skin rashes involving the palms and soles,

and mucosal lesions

Stage 2: Painless sore heals, and skin rash

forms

Latent syphilis

It is the period in which the disease is

subclinical but not necessarily dormant

It occurs within more than a year of infection

In this stage, diagnosis can be made only by

a serologic test

Tertiary syphilis

It is the tissue-destructive phase

It may develop 3 to 10 years following the

last evidence of secondary syphilis

Complications: Neurosyphilis,

Cardiovascular abnormalities, eye disease,

and granulomatous-like lesions (gummas)

Congenital syphilis

Placentally transmitted form of Syphilis, resulting in possible fetus abortion, still birth, baby born with syphiis

Dark-field microscopy

Definitive method to visualize live spirochetes in lesion exudate

Nontreponemal test

Serologic assay detecting reagin antibodies (e.g., VDRL, RPR) used to monitor therapy

Treponemal test

Specific serology for anti-treponemal antibodies (e.g., FTA-ABS, TPPA)

Rapid Plasma Reagin (RPR)

Card flocculation nontreponemal test for syphilis screening

VDRL test

Venereal Disease Research Laboratory slide test for reagin antibodies

FTA-ABS

Fluorescent treponemal antibody-absorption confirmatory test for syphilis

Treponema pallidum subsp. pertenue

Spirochete agent of yaws (frambesia tropica)

Yaws

Chronic tropical disease with skin, bone and cartilage lesions caused by T. pertenue

Primary Yaws

● Characterized by a wart like thickening of the

epidermis, which becomes fibrous, cracks open,

bleeds easily, and discharges a serous fluid

● This lesion typically develops 9-90 days (average of

21 days) after infection

● It can be accompanied by swollen lymph nodes

near the lesion

Secondary Yaws

● Characterized by a multiple raised yellow skin

lesions appear on various parts of the body

● These lesions can be papular (raised, solid bumps)

or ulcerative (open sores)

● Bone pain, especially at night, and swelling of the

joints may occur

● This stage can last for months, with periods of

active lesions followed by healing

Tertiary Yaws

● A late stage of the yaws infection

● It typically occurs 5 to 10 years after the initial

infection, in individuals who have not been treated

● It is characterized by destructive lesions affecting

the skin, bones, and cartilage

Treatment for Yaws

1. Azithromycin (single oral dose) at 30 mg/kg (maximum

2 gm) is the preferred choice in the WHO

2. Benzathine penicillin (single intramuscular dose) at

1.2 million units (adults) and 600,000 units (children)

Borrelia recurrentis

CHARACTERISTICS

● Gram-negative, corkscrew-shaped spirochetes

● Larger than Treponema species

VISUALIZATION

● Dark-field microscopy

● Wright or Giemsa stain

● Difficult to visualize using Gram stain

● Microaerophilic

Louse-borne spirochete that produces epidemic relapsing fever

Epidemic relapsing fever

Febrile illness with periodic relapses transmitted by body louse, due to B. recurrentis

Causative agent of B. reccurentis

Borrelia recurrentis

Vector of Epidemic Relapsing Fever

Body louse (Pediculus humanus)

Symptoms of B. recurrentis

High fever, Headache, Muscle and

joint pain, Nausea, Vomiting

Treatment for B. recurrentis

tetracyclines, doxycycline,

erythromycin, or procaine penicillin

Borrelia burgdorferi

Hard-tick-borne spirochete causing Lyme disease

Lyme disease

Multistage illness with erythema migrans, neurologic and arthritic manifestations

Vector of Lyme disease

Hard Tick (Ixodes)

Erythema migrans

Bull’s-eye skin lesion pathognomonic and hallmark of infection for early Lyme disease

First Stage

The presence of erythema migrans or red,

ringed-shaped lesion with a clear center or a

“bull’s eye like lesion” at the site of the tick

bite is diagnostic of lyme disease

Second Stage

It may start weeks to months after infection

○ There is dissemination of the organism to

other parts of the body

○ Signs and symptoms: Neurologic disorders

and nerve palsy

Third Stage

There is a presence of recurring chronic

arthritis (acrodermatitis chronica

atrophicans) that may continue for years

○ Infected individuals may also develop

demyelination of neurons with symptoms of

Alzheimer’s disease and multiple sclerosis

Microscopic Examination of Borrelia Burgdorferi species

● Leptospira species can be stained with Giemsa or

Wright stain

● Dark field microscopy can be used for the detection

of the organism in blood cultures after 2-3 weeks if

incubation

● Relapsing fever

○ Specimen of choice: Peripheral blood

○ Giemsa or Wright Stain: blue-colored

● Lyme disease

○ Specimen of choice: Blood, CSF, and biopsy

specimen

○ Warthin-Starry satin: Tissue section

○ Giemsa stain: Blood and CSF

Barbour-Stoenner-Kelly medium or

Chick embryo

Culture for Leptospira species

Polymerase Chain Reaction

Molecular test that test the presence of B. burgdorferi DNA in a sample.

LEPTOSPIRA

Leptospira interrogans

Hook-ended spirochete that causes leptospirosis, shed in animal urine

Weil syndrome

Icteric, severe leptospirosis with renal and hepatic failure

Anicteric leptospirosis

Common, milder form of leptospirosis often presenting with aseptic meningitis

Campylobacter jejuni

Curved Gram-negative rod causing bacterial gastroenteritis, often from poultry

Spirillum minus

Gram-negative spiral bacillus associated with rat-bite fever

Streptobacillary rat-bite fever

Fever-rash-arthritis syndrome following rodent bite; Spirillum minus or S. moniliformis

Bacillus anthracis

Large Gram-positive, spore-forming bacillus; etiologic agent of anthrax

Cutaneous anthrax

Form producing black eschar at skin inoculation site; most common, least lethal

Pulmonary anthrax

Inhalational ‘woolsorter’s’ disease leading to severe pneumonia and sepsis

Gastrointestinal anthrax

Anthrax acquired from eating infected meat; causes abdominal hemorrhage

Listeria monocytogenes

Motile, β-hemolytic Gram-positive rod causing listeriosis

Listeriosis

Severe food-borne infection affecting pregnant women, neonates and immunocompromised

Tumbling motility

End-over-end movement of Listeria at room temperature in wet mounts

Legionella pneumophila

Fastidious aquatic Gram-negative rod causing Legionnaires’ disease

Legionnaires’ disease

Severe atypical pneumonia contracted from inhaling contaminated aerosols

Pontiac fever

Self-limited flu-like illness caused by Legionella exposure without pneumonia

Mycoplasma pneumoniae

Cell-wall-deficient bacterium causing primary atypical (‘walking’) pneumonia

Primary atypical pneumonia

Tracheobronchitis or mild pneumonia with dry cough, often in young adults

Rickettsia

Obligate intracellular, arthropod-borne bacteria causing vasculitic fevers

Spotted fever group

Rickettsiae (e.g., R. rickettsii) producing rash on palms/soles; tick-borne

Typhus group

Rickettsiae (R. prowazekii, R. typhi) transmitted by lice or fleas producing typhus

Rocky Mountain spotted fever

Most severe rickettsiosis caused by R. rickettsii

Epidemic typhus

Severe louse-borne fever with rash, due to R. prowazekii

Orientia tsutsugamushi

Agent of scrub typhus transmitted by chigger mites

Scrub typhus

Febrile illness with eschar, lymphadenopathy and maculopapular rash

Chlamydia trachomatis

Obligate intracellular bacterium causing trachoma, LGV and genital infections

Trachoma

Chronic conjunctivitis leading to blindness caused by C. trachomatis

Lymphogranuloma venereum (LGV)

Invasive STI with genital ulcer and painful lymphadenopathy due to C. trachomatis L-serovars

Elementary body

Infectious, extracellular, metabolically inert form of Chlamydia

Reticulate body

Intracellular, metabolically active replicative form of Chlamydia

Hypha

Tubular filament that composes mold mycelium

Septate hyphae

Hyphal filaments divided by cross-walls (septa)

Chitin

Acetylglucosamine polymer giving rigidity to fungal cell wall

Dimorphic fungi

Fungi existing as molds at 25 °C and yeasts at 37 °C

Tinea versicolor

Superficial infection with Malassezia causing hypopigmented macules

Tinea nigra

Brown-black macules on palms/soles due to Hortaea werneckii

White piedra

Soft white nodules on hair shafts caused by Trichosporon species

Black piedra

Hard black nodules on hair caused by Piedraia hortae

Mycetoma

Chronic subcutaneous granulomatous infection (‘Madura foot’) by fungi or actinomycetes

Chromoblastomycosis

Slowly progressive verrucous lesions with sclerotic bodies caused by dematiaceous fungi

Histoplasma capsulatum

Dimorphic fungus producing intracellular yeasts in macrophages

Histoplasmosis

Pulmonary and systemic mycosis acquired by inhaling Histoplasma spores

Candida albicans

Yeast forming pseudohyphae; common opportunistic pathogen

Candidiasis

Spectrum of mucocutaneous or systemic infections due to Candida

Cryptococcus neoformans

Encapsulated yeast causing meningitis, especially in AIDS

Cryptococcosis

Pulmonary or CNS disease from inhalation of Cryptococcus spores

Virion

Complete infectious viral particle outside a host cell

Capsid

Protein shell that encloses viral nucleic acid

Envelope (viral)

Lipid membrane with glycoproteins surrounding some viruses, fragile to detergents

Adenoviridae

Family of non-enveloped dsDNA viruses causing pharyngitis, conjunctivitis and pneumonia

Hepatitis B virus

Enveloped partly dsDNA hepadnavirus transmitted via blood and body fluids

Herpes simplex virus

HSV-1/2; enveloped dsDNA viruses establishing latency in sensory ganglia

Varicella-zoster virus

Herpesvirus causing chickenpox (primary) and shingles (reactivation)

Epstein–Barr virus

Herpesvirus infecting B cells; agent of infectious mononucleosis and Burkitt lymphoma

Cytomegalovirus

Herpesvirus causing congenital disease and infection in immunosuppressed patients

Human papillomavirus

Non-enveloped dsDNA virus; certain types (16,18) induce cervical cancer