Opath1 - Block 2 - Bacterial Infections

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List of bacterial infections

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- Staphylococcus
- Group A, beta-hemolytic streptococcus (GAS, streptococcus pyogenes)
- Mycobacteria
- Treponema
- Bartonella
- Actinomyces
- Mixed

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Staphylococcus can cause...

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Impetigo

Front 3

Is staph part of the normal flora on the skin?

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Yes

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Definition of Impetigo

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- superficial infection of skin caused by Staph aureus and/or Strep pyogenes
- areas of superficial breaks of skin
- mostly children, and adults with systemic conditions
- starts out as vesicles. Later, develops into large bullae or ulcerated/crusted. Can look like secondary herpes or angular cheilitis.

Front 5

Dx and Tx of Impetigo

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Dx: Clinical presentation and history. Pattern corresponds to breaks/scratches in skin.

Tx: Prevention and topical antibiotics (heals by itself in most cases).

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MRSA

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- community-acquired methicillin resistant Staphylococcus aureus.
- if you treat a pt with MRSA, the pt's condition might get worse.

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Streptococcus pyogenes causes...

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- pharyngitis/tonsillitis
- Scarlet fever

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Pharyngitis/tonsillitis

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- infections in the throat
- caused by respiratory droplets or oral secretions
- caused by virus or bacteria

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Pharyngitis/tonsillitis caused by virus

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- majority of pharyngitis/tonsillitis is caused by virus.
- self limiting
- no tx needed

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Pharyngitis/tonsillitis caused by bacteria

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- caused by GAS
- "Strep throat"
- 10-30% of pharyngitis/tonsillitis
- children (5-15 yo) and their parents
- sore throat, redness, cervical lymphadenopathy, fever, etc.
- NO VESICLES

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Lab studies for Strep Throat

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- Rapid direct antigen test (5-10 min)
- Culture (gold standard! 1-2 days)

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Tx for Strep Throat

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- antibiotics prevents development of complications

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Scarlet fever

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- GAS can produce ERYTHROGENIC TOXIN, which attacks small vessels.
- Pts that have no antitoxin antibody will develop high fever
- mostly in children
- Exanthem and Enanthem
- Lab studies: Rapid direct antigen test, culture, etc.
- Tx: Antibiotics

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Exanthem

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- seen in scarlet fever
- Skin: widespread rash and petechiae
- fades in a week and is followed by desquamation

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Enanthem

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- Oral cavity: pharyngitis/tonsillitis, may have soft palate petechiae
- Tongue: hyperplastic, erythematous fungiform papillae against a white background initially (white strawberry tongue) or a red background (red strawberry tongue) later.

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Complications of Streptococcus

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- Autoimmune diseases - glomerulonephritis and rheumatic fever.
-Glomerulonephritis - antibody against M protein cross-reacts with antigens in host tissue (i.e. in kidney). Damages many other tissues.
- Rheumatic fever - pts that have a positive famile history of RF must get a post-therapeutic lab testing after streptococcus infection.

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Mycobacteria causes....

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- Tuberculosis (mycobacterium tuberculosis)
- Leprosy (mycobacterium leprae)

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Mycobacterium tuberculosis

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- high lipid content in its "cell wall." Thus it is resistant to killing by phagocytosis, inhibits penetration of antimicrobial agents, and resists drying and is able to remain viable in dried sputum.
- Drug-resistant strains
- Tx: combination of antibiotics

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Some facts about tuberculosis

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- A communicable chronic granulomatous (often caseating) disease.
- Elderly, the poor, patients with AIDS and immune-compromised patients
- HIV has become the single most important risk factor for the development of tuberculosis
- TB is the leading cause of death among HIV infected people

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Tuberculosis pathogenesis

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- Not based on any inherent toxicity
- The destructive tissue response is based on
induction of a hypersensitivity reaction
- proliferative and destructive granulomatous tissue reaction (tubercles) and central necrosis (caseous)
- Classification: primary or secondary

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Primary tuberculosis

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- This form develops in non-sensitized individuals
- Begins in the lung by inhaling the microorganisms
- Hypersensitivity develops during the second week
- PPD skin test +

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More about tuberculosis

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- 95% of primary tuberculosis are arrested (Self-limiting).
- The tubercle is walled-off by connective tissue and may become calcified.
- Not communicable, even the microorganism may still be alive.
- A tiny fibrocalcific nodule may be seen.
- Such persons are infected but do not have active disease
cannot transmit organisms to others.

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Secondary tuberculosis

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- the infection may be reactivated later when immune response is low OR the pt can be re-infected.

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Progressive primary tuberculosis

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- high in HIV positive pts with high immunosuppression
- continuous development of primary tuberculosis without interruption
- proceed to conditions normally seen only in secondary tuberculosis

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Tuberculosis - appearance

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- Oral lesions: uncommon. Majority from contaminated sputum. Seen in some pts with systemic tuberculosis (progressive primary or secondary).
- Soft Tissue: chronic non-healing ulcer or swelling (granulation tissue like). Looks like squamous cell carcinoma, which is the MOST common reason for ulcer.
- Jaw bones: osteomyelitis
- CANNOT tell TB clinically. Need biopsy!

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Tests for tuberculosis

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- Mantoux test (tuberculin test, PPD skin test)
- Culture - takes long time (3-6 weeks), gold standard, allows testing of drug specificity.
- Stain - acid fast stain. not specific.
- PCR amplication - quick and specific

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Mantoux test

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- intracutaneous injection of purified protein derivative
- delayed hypersensitivity reaction, peaks in 48 to 72 hours
- does not differentiate between infection and disease
- Not accurate on people that have been previously immunized

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Leprosy

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- A chronic granulomatous disease caused by Mycobacterium leprae
- Acquired in childhood or young adulthood
- Long incubation period (years to decades)
- Skin, mucous membrane of the upper respiratory tract and peripheral nerves are the major sites of involvement in all leprosy
- Classification:
Tuberculoid/Paucibacillary or
Lepromatous/Multibacillary.

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Paucibacillary leprosy

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- Patients with high immune response
- Lepromin test + (skin test to heat-killed bacteria)
- Oral lesion rare
- Localized disease: A small number of well-circumscribed, hypopigmented skin lesions.
- Nerve involvement lead to loss of sensation in the affected skin

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Paucibacillary leprosy - histology

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- granulomatous inflammation with well-formed granulomas
- a PAUCITY of organisms present, indicated by acid-fast stains.

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Multibacillary leprosy

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- Patients with reduced immune response.
- Lepromin test (-)
- Diffuse disease: Numerous, ill-defined, hypopigmented lesions, with time, become thickened and loss of skin appendages. Skin enlargement leads to facial distortion
- Nerve involvement spread to most of the body

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Multibacillary leprosy - histology

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- granulomatous inflammation with no well-formed granulomas
- Numerous bacteria in the tissue, identified by acid fast stains.

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Multibacillary leprosy - orofacial lesions

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- Soft tissue: Ulceration, necrosis and loss of tissue.
- Bone: bone erosion and perforation (palate).
- FACIES LEPROSA: resorption of the anterior nasal spine and the anterior maxillary alveolar ridge.

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Leprosy - Dx

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- based on skin characteristics with diminished sensation
- demonstrate the presence of M. leprae in tissue

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Leprosy - Tx

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- multidrug regimens for infection
- treat complication of nerve damage
- reconstruction of the damage

Front 36

Treponema pallidum causes....

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Syphilis

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Syphilis - basics

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- Transmission: sexual contact and mother to fetus
- 64% was among MSM, most increases in BM
- Oral sex and AIDS are main cause for the recent hike
- Presentation complicated by immunodeficiency status (AIDS)

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Primary syphilis

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- CHANCRE - highly infectious. Site of inoculation. Develop in days (3-90). Ulcer, lymphadenopathy. Most common extragenital site is oral cavity (lip is most common). Heal spontaneously 3-8 weeks.
- Dx: Serology (-). IF or dark-field microscopy (+).

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Secondary syphilis

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- If the primary lesion not treated, patients develop secondary syphilis 2-6 months after initial infection.
- MACULOPAPULAR RASH (skin), MUCOUS PATCH (mucosa), condyloma lata (skin & mucosa).
- heals spontaneously in 3-12 weeks.
- Dx: Serology (+). IF or dark-field microscopy (+).

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Tertiary syphilis

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- Now very rare, mostly seen in AIDS patients
- Significant cardiovascular and CNS damage
- GUMMAS - granulomatous inflammation, necrosis and ulceration, extensive tissue destruction
- involves many organs
- Oral: tongue and palate perforation

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Causes of palate perforation

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1. Cocaine use
2. Malignancy
3. Syphilis and/or Leprosy

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Congenital syphilis

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- Transplacental infection with Treponema pallidum during fetal development
- Abortion, stillbirth, death soon after delivery
- Developmental abnormalities
- Hutchinson’s triad

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Hutchinson's triad

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- Dental anomalies - Hutchinson's incisor and mulberry molar
- Deafness (CN 8)
- Blindness (interstitial keratosis)

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Bartonella infection - normal patients

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- Granulomatous inflammation
- CAT SCRATCH DISEASE
- NO tx necessary

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Bartonella infection - immunocompromised pts

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- angiogenesis
- BACILLARY ANGIOMATOSIS
- need antibiotic

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Cat Scratch Disease

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- transmitted from cat to human by a scratch
- benign, self-limiting infection
- scratch on face usually develops submandibular lymphadenopathy
- Dx: clinical history, bacteria in specimen, or positive titer. Culture is not possible.
- Tx: None. resolves in 4 months.

Front 47

Actinomyces

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- Gram + filamentous, anaerobic bacteria, 50% cervicofacial
- Actinomyces israelli is most common (part of normal flora)
- Enter tissue through an area of prior trauma
- Dx: histology + culture
- Tx: Surgical drainage/debridement and antibiotics

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Actinomycosis presentation

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- Usually present as an acute deep suppurative abscess with an associated draining sinus tract
- Colonies of actinomycotic organisms surrounded by neutrophils
- SULFUR GRANULES - yellowish flecks seen clinically representing colonies of actinomyces.

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Mixed bacterial infections

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- tonsillar concretions and tonsillolithiasis
- noma

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Tonsillar concretions and tonsillolithiasis

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- The convoluted crypts commonly are filled with desquamated keratin, foreign material, and 2nd colonized with bacteria (Actinomyces common)
- tonsillar concretions - a mass
- tonsillolithiasis - calcified. sometimes on radiographs, they are superimposed on the midportion of the mandibular ramus.
- most have no symptoms and no tx needed.
- removal may be necessary if there are symptoms.

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Noma

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- opportunistic infection caused by normal flora in immunodeficient patients (malnourished children and AIDS pts).
- begins as necrotizing ulcerative gingivitis, and extends to involve adjacent soft tissues
- extensive necrosis, destruction, and facial disfigurement
- 95% die if not treated
- Tx: correct the underlying disease, debridement, and antibiotics