F4 Spirochetes, Mycoplasma, Ricketssia, and Miscellaneous Bacteria

Spirochetes, Mycoplasma, Rickettsia, and Miscellaneous Bacteria

Spirochaetales

• Description: Difficult to gram stain due to their unique cellular structure, characterized by a helical shape. They are generally long and slender organisms that can thrive in anaerobic environments or in microaerophilic conditions where low oxygen levels are present.

• Families:

  • Leptospiraceae: Contains the genus Leptospira, noted for its pathogenic potential in humans.

  • Spirochaetaceae: This family includes genera such as Borrelia and Treponema, which are significant human pathogens.

Spirochetes

• Characteristics: Slender, flexuous, helically shaped, unicellular bacteria with measurements ranging from 0.1 - 0.5 μm in width and 5 - 20 μm in length.

• Motility: Achieved through unique structures known as periplasmic flagella, also termed endoflagella, which allow for increased flexibility and movement through viscous environments.

• Types:

  • Treponema: Characterized by tightly coiled structures with 6-10 spirals, making them difficult to visualize.

  • Borrelia: Noted for thicker coiling with 30-40 spirals, which can be seen in clinical specimens.

  • Leptospira: Exhibits thicker coiling with distinctive hooked ends (3-5 spirals), contributing to its pathogenicity.

Treponema

• Visualizing: Treponema species are notoriously difficult to visualize using standard bright field microscopy. However, they can be effectively seen using dark field microscopy, which enhances contrast.

• Pathogenic Species:

  • T. pallidum subsp. pallidum → Causes Venereal Syphilis (STD).

  • T. pallidum subsp. pertenue → Causes Yaws, which primarily affects the skin and bones, leading to ulcerative lesions.

  • T. pallidum subsp. endemicum → Directly linked to Endemic Syphilis or Bejel, affecting skin, bones, and mucous membranes.

  • T. carateum → Responsible for Pinta, which results in skin lesions that can progressively lead to complication if untreated.

• Discovery: First identified by Fritz Schaudin and Hoffmann in 1905, which marked a significant milestone in microbiological research.

• Characteristics of T. pallidum subsp. pallidum: This organism is an obligate intracellular pathogen, meaning it does not survive outside host cells and cannot be cultured in standard agar, only in rabbit epithelial cells.

Borrelia

• Identification: Borrelia is classified as a blood spirochete, diagnosed predominantly through the examination of peripheral blood smears. The microscopic characteristics are crucial for distinguishing Borrelia infections.

• Diseases:

  • Lyme Disease: An increasing global health concern linked with tick bites.

  • Relapsing Fever: Caused by various Borrelia species and characterized by recurrent episodes of fever.

Leptospira

• Methods of Diagnosis: Can be diagnosed through either culture methods or serological analysis (in vitro). Leptospira is associated with Weil’s Disease, also referred to as Infectious Jaundice, which can have severe clinical manifestations.

Syphilis

Overview

• Aliases: Known historically as Great Pox Disease, Antique Disease, Halian Disease, or French Disease.

• Often referred to as the “Great Imitator” due to its diverse symptoms that mimic those of many other conditions.

• Theories of Spread:

  • Pre-Columbian Theory: Suggests that syphilis existed in Europe before the arrival of Columbus.

  • Columbian Theory: Proposes that the disease originated in the Americas and disseminated to Europe following Columbus’s voyages.

Mode of Transmission

• Transmission Routes: Syphilis is primarily a sexually transmitted infection, but can also be transmitted transplacentally from a pregnant woman to her fetus, or in rare cases, through blood transfusions.

Incubation Period

• The incubation period for syphilis can range from 10 to 90 days, with an average of approximately 14-21 days, making early detection challenging.

Stages of Syphilis

• Primary Syphilis:

  • Presents with a painless chancre, generally at the site of infection, accompanied by regional lymphadenopathy. It is highly contagious during this stage.

  • Diagnosis is achieved through dark field microscopy and serologic testing, which typically becomes positive 1-3 weeks after the appearance of the chancre.

  • Healing usually occurs spontaneously within 3-6 weeks, even without treatment.

• Secondary Syphilis:

  • May occur if primary syphilis is untreated, with onset occurring 6 weeks to 6 months after the primary chancre.

  • Symptoms frequently include widespread skin rashes, lesions known as condylomata lata, and can disseminate to various organs.

  • Diagnosed using similar methods to primary syphilis, and this stage is considered the best for serological testing because of the high antibody titers.

• Latent Syphilis:

  • Characterized by an absence of clinical symptoms, although serological tests remain positive, indicating the presence of the infection.

Tertiary Syphilis and Congenital Syphilis

Tertiary Syphilis

• Develops 5 to 30 years after the initial infection, often leading to serious complications.

• Symptoms can include a variety of neurological abnormalities, paralysis, delusions, and gummas, which are painful, necrotizing ulcers affecting various body tissues.

• Diagnosis is typically made through serologic testing, with cerebrospinal fluid (CSF) analysis sometimes employed if high test positivity is indicated, confirming neurosyphilis.

Congenital Syphilis

• This form of syphilis is transmitted from an infected mother to her fetus during any stage of the mother's syphilis.

• Symptoms in newborns may range from bone malformations, skin rashes, acute meningitis, to characteristic dental anomalies known as Hutchinson’s teeth.

• Detection primarily relies on maternal serological testing, ensuring that the mother has had appropriate screening for syphilis prior to delivery, along with negative results on dark-field microscopy applied to newborn specimens.

Laboratory Diagnosis of Syphilis

• Microscopy Techniques: Dark field microscopy remains a gold standard for examining lesions associated with syphilis.

• Serological Tests: Include non-treponemal tests (used for screening purposes) and treponemal tests (which are confirmatory).

Treatment

• Drug of Choice: Benzathine Penicillin G is the standard treatment for all stages of syphilis.

• Alternative Treatments: Tetracycline and Doxycycline may be considered for patients allergic to penicillin.

• Adverse Reactions: Patients may experience Jarisch-Herxheimer Syndrome, which can occur post-treatment due to the rapid lysis of treponemes.

Treponema

Treponema pallidum subsp. pertenue

• Responsible for Yaws, a chronic, non-venereal disease affecting skin and bones, primarily through direct contact with infected open skin lesions.

Treponema pallidum subsp. endemicum

• Causes Bejel, a non-venereal form of syphilis endemic in some regions, typically presenting with mucosal lesions and other complications.

Treponema pallidum subsp. carateum

• Responsible for Pinta, characterized by ulcerative skin manifestations but without systemic dissemination.

Borrelia

Characteristics

• Borrelia’s appearance is distinctive, appearing loosely twisted and resembling a stretched spiral under the microscope.

• Mode of Transmission: Primarily via tick or louse bites, an important factor in controlling disease spread.

• Diagnosed using modified Kelly’s medium, specifically Barbour-Stoenner-Kelly medium, designed for culturing spirochetes.

Agents of Relapsing Fever

• Borrelia recurrentis: Causes Louse-borne relapsing fever, characterized by episodes of high fever, often triggered by the proliferation of bacteria in the bloodstream. The primary vector is the human louse.

• Borrelia hermsii and Borrelia parkerii: Responsible for tick-borne relapsing fever, using the Ornithodoros hermsii and Ornithodoros parkerii as their vectors respectively.

Lyme Disease (Borrelia burgdorferi)

• First identified in Lyme, Connecticut, this disease has gained significant attention due to its increasing incidence.

• Stages of Lyme Disease:

  • Stage One: Erythema chronicum migrans, often described as a target-shaped rash.

  • Stage Two: The disease disseminates, potentially damaging various organs, including the heart and nervous system.

  • Stage Three: A chronic stage featuring diverse neurological abnormalities, such as cognitive dysfunction.

Laboratory Diagnosis

• Immunoserological Tests: Western blot tests are regarded as the gold standard for Lyme disease diagnosis, alongside the use of modified Kelly’s medium contributing to accurate identification and treatment.

Leptospira and Mycoplasma

Leptospira

• Description: Leptospira is an aerobic bacterium, recognizable by its tightly twisted morphology, notable for potential indirect contamination through water or soil infected with their urine.

• Important Serovars:

  • Leptospira interrogans serovar icterohaemorrhagiae → Causes Weil’s syndrome, which can lead to severe kidney and liver damage.

• Additional serovars are associated with a range of febrile illnesses, complicating diagnosis.

Laboratory Diagnosis of Leptospira

• Culturing can be done using Fletcher’s or EMJH mediums, while dark field microscopy allows for detailed examination of the bacteria's unique structure.

Mycoplasma

• Uniquely atypical bacteria that lack a cell wall, rendering them inherently resistant to antibiotics that inhibit cell wall synthesis. Mycoplasma’s structural uniqueness contributes to its pathogenicity and treatment challenges.

• Mycoplasma pneumoniae: Known as a major cause of community-acquired pneumonia and is recognized for its ability to cause mild respiratory illness, often referred to as “walking pneumonia.”

Mycoplasma and Chlamydia

Mycoplasma hominis

• Known for producing large colonies resembling fried eggs, it is primarily associated with pelvic inflammatory disease, posing significant health risks in affected individuals.

Ureaplasma urealyticum

• An important urease-positive mycoplasma responsible for causing non-gonococcal urethritis (NGU), a common condition that poses challenges in diagnosis and management.

Chlamydia

• Previously known as Bedsonia, Chlamydia is now classified as Chlamydophila, which is an obligate intracellular organism requiring a host for growth.

Chlamydophila psittaci

• Causes psittacosis, primarily transmitted through inhalation of aerosols from infected birds, highlighting the importance of public health awareness in veterinary settings.

Chlamydophila pneumoniae

• Associated with mild respiratory infections, there is suspicion regarding its potential for human-to-human transmission, necessitating further research.

Chlamydia and Rickettsia

Chlamydia trachomatis

• Serotypes:

  • A, B, Ba, C: Cause trachoma, a leading infectious cause of blindness worldwide.

  • D, E, F, G, H, I, J, K: Commonly cause non-gonococcal urethritis and pelvic inflammatory disease, representing significant public health challenges.

  • L1, L2, L3: Associated with lymphogranuloma venereum (LGV), resulting in severe complications if untreated.

Rickettsia

• These bacteria are classified as gram-negative and exhibit obligate intracellular characteristics requiring arthropod vectors for transmission.

Laboratory Diagnosis of Rickettsia

• Cultured in tissue culture media, including chicken embryo, HeLa, or Vero cells, which is essential for proper identification.

• Serological tests, notably the Weil-Felix reaction, are used to detect rickettsial antibodies.

Miscellaneous Bacteria

• Gardnerella vaginalis: Identified as causative agent of bacterial vaginosis, often diagnosed by the presence of clue cells or a fishy odor noted during examinations.

• Calymmatobacterium granulomatis (formerly Klebsiella): Causes granuloma inguinale (Donovanosis), an infectious disease that can lead to significant tissue destruction if untreated.

• Ehrlichiosis: Diagnosed through examination of WBC morphology, highlighting the diverse pathogenic potential of bacterial infections.

More Miscellaneous Bacteria

• Actinobacillus actinomycetemcomitans: Affects oral health and can cause subacute bacterial endocarditis (SBE), notable for the unique star-like colony formation observed in cultures.

• Streptobacillus moniliformis: Associated with rat-bite fever, producing L-forms characterized by a string of beads appearance when cultured.

• Chromobacterium violaceum: An opportunistic pathogen from the environment causing water contamination, producing characteristic violet-colored colonies.

• Cardobacteroides hominis: Notably a cause of SBE, identifiable by tear-drop shaped colonies.

• Capnocytophaga spp.: This bacterium is part of normal oral flora yet is implicated in periodontal disease pathology.

More Bacteria

• Bartonella bacilliformis: Transmitted via sandfly bites, it causes Carrion’s disease and related conditions, highlighting the significance of vector control in disease mitigation.

• Legionella pneumophila: Short aerobic rods with specific growth requirements for cysteine and iron, responsible for Pontiac fever, cultured on specialized media.

• Listeria monocytogenes: Gram-positive motile rods associated with foodborne illnesses such as granulosomatosis, presenting substantial risk particularly in immunocompromised individuals.

• Erysipelothrix rhusiopathiae: Causative agent of erysipeloid, identifiable by characteristic brush-like morphological appearances under microscopic conditions.

Final Topic

• Tropheryma whipplei: Etiological agent of Whipple's disease; difficult to culture, diagnosed predominantly through cytogenetic analyses. Its unique characteristics include being a gram-positive actinomycete/bacilli, often identified using PAS-staining techniques for macrophage visualization.