Pathogens That Involve The Skin

PATHOGENS THAT INVOLVE THE SKIN

BACTERIAL INFECTIONS OF THE SKIN A. Staphyloccocus aureus Characteristics: - Gram (+) cocci in clusters - catalase and coagulase positive - non-motile, non spore forming - facultative anaerobe - Toxins and enzymes

TOXINS AND ENZYMES: 1. Coagulase - coagulates (clot) fibrin - inhibits phagocytosis 2. Leucocidin - destroys phagocytic leucocytes 3. Exfoliative toxin (Exfoliatin) - sloughs off the epidermis - responsible for the Staphylococcal Scalded Skin Syndrome (SSS)

TOXINS AND ENZYMES: 4. Enterotoxin - heat stable -causes food poisoning  vomiting, diarrhea 5. Toxic Shock Syndrome toxin (TSST-1) - exotoxin - responsible for toxic shock syndrome 6. Hyaluronidase - destroy tissues - breaks down proteoglycans in connective tissue 7. Staphylokinase - dissolves the clot

Diseases: 2. Folliculitis 3. Sty or Hordeolum 4. Furuncle (boil) 5. Carbuncle (coalescence of boils) 6. Staphylococcal Scalded skin Syndrome 7. Toxic Shock Syndrome 7. Staphylococcal Enteritis 8. Staphylococcal Pneumonia - less common

• Reservoir: Humans • Transmission: 1. Nasal Carriers (20-30%) - autoinfection 2. Direct Contact with a person having purulent lesions or a carrier 3. Hands of healthcare workers (hospital) • Incubation Period: - Variable but usually between 4 to 10 days • Diagnosis: - culture -Identification of the organism

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Treatment: 1. Penicillinase-resistant Penicillin 2. Cephalosporin 3. Clindamycin 4. Vancomycin • Prevention and Control 1. Good personal hygiene - Handwashing - Antibacterial soap - Avoid common use of toilet articles 2. Contact Precaution 3. Antibiotic ointment and solution

B. Streptococcus pyogenes  Group A Strep (GAS) / Strep A • Characteristics - Gram (+) cocci in chains - Group A-Beta hemolytic - non-motile, non-spore forming - facultative anaerobe • Classification of Streptococci - Lancefield-CHO - Group A- beta hemolytic streptococci - Streptococci pyogenes - Causes: strep throat, impetigo, scarlet fever

• Group B- beta hemolytic streptococci - Streptococcus agalactiae - Causes: decubitus ulcer, neonatal infection • Group D- alpha hemolytic streptococci - Enterococci - Causes: SBE, UTI • Streptococcus viridans - alpha hemolytic strep - Causes: dental caries, infectious endocarditis • Streptococcus pneumoniae - alpha hemolytic strep - Causes: pneumonia, meningitis, sinusitis, otitis media

• Toxins (Produced by Strep. Pyogenes) 1. Erythrogenic Toxin - cause Scarlet Fever 2. Toxic Shock Syndrome Toxin • Diseases 1. Scarlet Fever - widespread, pink red rash in the abdomen, sides of chest and skinfolds. 2. Erysipelas (St. Anthony’s Fire) - red hot eruptions 3. Necrotizing Fascitis 4. Impetigo - reddish spots  vesicles  yellow- brown, honey-colored crust

• Incubation period: 1 to 3 days • Reservoir: Human • Transmission: -person to person via large respiratory droplets -direct contact with patients or carriers • Diagnosis: - culture - Identification of the organism • Treatment: 1. Penicillin 4. Cephalosporin 2. Amoxicillin 5. Clindamycin 3. Erythromycin • Prevention - contact and droplet precaution - isolation until treated

C. Pseudomonas aeruginosa • Characteristics: - Gram (-) motile bacillus - Non-spore forming, obligate aerobe - produce a blue-green pigment (pyocyanin) - opportunistic infection - Toxins: cytotoxin necrotoxin neurotoxin - Diseases: a. Otitis externa b. Infection of burn wounds c. Opportunistic respiratory infection

- Reservoir: -widespread in nature (soil, plants, animals, humans) - Transmission - Hands of personnel - Fomites - Treatment - Penicillin - Quinolone - Cephalosphorin - Carbapenems - Aminoglycoside - Prevention -Aseptic treatment of wounds and burns - Proper disposal of dressings - Care in sterilization of catheters

D. Leptospira sp. Characteristics: Spirochete Highly motile, with hood ends and flagella Manifestations: - Mild fever - Calf tenderness, conjunctival suffusion - Jaundice, renal failure Reservoir: Rodents Transmission: - Direct contact with urine, blood or tissue from an infected animal - Exposure to a contaminated environment like Flood waters  skin abrasion and mucous membranes.

• Incubation period: 2 to 26 days • Diagnosis: - Isolation from blood, CSF, Urine - Microscopic Agglutination Test (MAT) • Treatment - Penicillin -Ampicillin -Amoxicillin - Erythromycin • Prevention and Control – Chemoprophylaxis: Doxycycline 200mg once a week – Avoidance of exposure to urine and tissues from infected animals – Rodent control

E. Clostridium tetani

• Characteristics: - Gram (+), anaerobic, spore-former bacillus - Produce Tetanospasmin • Disease: Tetanus - muscle spasm - lock jaw - risus sardonicus -respiratory muscle paralysis • Reservoir: Soil • Transmission: Spore introduced through the wounds • Incubation Period: 3 to 21 days • Diagnosis: Clinical findings and isolation of organism

• Treatment: - Penicillin  to eradicate vegetative cells - Metronidazole  to eradicate vegetative cells - Antitoxin • Prevention and Control - proper wound management - active immunization  tetanus toxoid with booster every 10 years

F. Mycobacterium leprae

• Characteristics: - acid fast, aerobic bacillus • Disease: leprosy (Hansen’s disease) - 2 forms: 1. Neural, tuberculoid form - lesions on skin and peripheral nerves with loss of sensation 2. Cutaneous, Lepromatous form - progressive disfiguring nodules in skin, invades throughout the body • Reservoir: Humans

• Transmission: uncertain - may gain entrance through respiratory tract or broken skin • Incubation Period: 9 months to 20 years • Diagnosis: AFB in skin smears/biopsies • Treatment: Dapsone Clofazimine Prevention and Control: - BCG 80% effective - No isolation needed

G. Borrelia burgdorferi

• Characteristics: - Gram (-) loosely coiled spirochete • Disease: LYME DISEASE - Early distinctive, red skin lesion with central clearing - Systemic manifestation - neurologic and cardiac abnormalities • Reservoir: ticks, rodents, deer • Transmission: tick bite • Incubation period: 3 to 33 days after tick bite

• Diagnosis: - Observation of characteristic lesions - Special medium: Barbour-Stoenner-Kelly (BSK) medium • Treatment: – Doxycycline – Amoxicillin – Cefuroxime Prevention and Control: – Avoid tick-infested areas – Wear light clothing with long pants, long sleeves – Use tick repellant (DEET)

H. Bacillus anthrax

• Characteristics: - Gram (+) spore forming, bacillus • Reservoirs - anthrax-infected animals - present in soil, animal hair, wool, animal skins and hides • Mode of Transmission - Entry of Endospores through: - breaks in skin - inhalation of spores - ingestion of bacteria in contaminated meat

• Disease: 1. Cutaneous anthrax (95%) - Depressed, painless blackened lesions (eschars) - caused by necrotoxin 2. Inhalation or Pulmonary Anthrax (Woolsorter’s Disease) - Fever, myalgia, non-productive cough respiratory distress death 3. Gastrointestinal Anthrax - Rare, fatal - Vomiting, abdominal pain, bloody diarrhea • Diagnosis: -Isolation of B. anthracis -Immunodiagnostic procedures • Treatment: Penicillin • Prevention: Vaccine

I. Bartonella henselae  Characteristics: – Gram (-) motile bacillus – Present in saliva deposited in cat’s fur and claws

 Disease: Cat Scratch Disease - small red raised spot crusty sore - Regional lymphadenopathy, fever, rash, malaise - Benign, self-limiting (resolves spontaneously in 2-4 months)

 Reservoir: Domestic cats  Transmission:

• Incubation period: 3-5 days • Diagnosis: - positive skin test - Identification on skin biopsy (WarthinStarry silver stain) • Treatment: Rifampicin Cotrimoxazole Ciprofloxacin Azithromycin

II. VIRUSES A. HUMAN PAPILLOMA VIRUS (HPV) Characteristics: non enveloped, DNA Virus Disease: Warts Reservoir: Humans Transmission: Direct contact Incubation Period: 1 to 20 years (usually 2 to 3 months) Diagnosis: Hx and PE Treatment: may resolve spontaneously Cryosurgery (liquid nitrogen) laser therapy, salicylic acid antiviral therapy

B. VARICELLA ZOSTER VIRUS Characteristics: herpes virus, DNA virus Disease: Varicella and Herpes Zoster - maculopapular vesicle pustules crust = zoster (shingles) - painful vesicular lesions in a dermatomal distribution Reservoir: Humans Transmission: direct contact, droplet, airborne spread of vesicle fluids or secretions of the respiratory tract Incubation Period: 14 to 21 days - contagious from 1 to 2 days before onset of rash until all crops of vesicles have crusted. Treatment: wet compress, varicella zoster Ig (within 96 hrs of exposure) Prevention: live attenuated varicella virus vaccine

• C. RUBEOLA VIRUS Characteristics: Paramyxovirus, RNA virus Disease: Measles koplik spots, fever, coryza, cough, conjunctivitis maculopapular rash from face---arms and legs Reservoir: Humans Transmission: airborne by droplet spread direct contact with nasal or throat secretions Incubation Period: 7 to 14 days contagious 2 to 4 days before rash appears until 2 to 5 days after onset of rash Treatment: supportive Prevention and Control: live, attenuated measles vaccine—lasts for 15 years - airborne precautions

D. RUBELLA VIRUS Characteristics: Toga virus, RNA virus Disease: German Measles - 3 day measles - mild coryza, conjunctivitis, fever, maculopapular rash post-auricular lympahadenopathy Reservoir: Humans Transmission: droplet spread or direct contact with nasopharyngeal secretions Incubation period: 14 to 21 days - contagious shortly before rash appears and until symptoms disappear Treatment: Supportive Prevention and Control: Live, attenuated rubella vaccine droplet precautions

E. RABIES VIRUS Characteristics: Rhabdovirus, RNA virus, bullet shaped Disease: rabies - fatal, acute viral encephalitis - hydrophobia: painful contraction of pharyngeal muscles when swallowing liquids - hypersalivation, malaise, convulsion - death --- within 1 to 2 weeks once symptoms develop - Pathognomonic: Negri Bodies found in brain cells Reservoir: dogs, foxes, cats, bats Transmission: bite of rabid animal Incubation Period: variable but usually 3 to 8 weeks Diagnosis: Identify negri bodies Treatment: prompt and proper treatment of bite wounds human rabies immunoglobulin Prevention and Control: vaccinate all pets, avoid sick and aggressive animals, vaccinate high-risk persons, standard precautions

F. DENGUE VIRUS Characteristics: Flavivirus, RNA virus Disease: Dengue Fever/Break bone fever myalgia, fever, headache, rash Transmission: bite of a Aedes aegypti female mosquito Incubation period: 2 to 7 days Diagnosis: Hx and PE - fever, headache, retroorbital pain, rash, myalgia - petecchiae, (+) torniquet test - viral isolation, serology Treatment: supportive Prevention and Control: mosquito control

III. FUNGI

A. DERMATOPHYTES

Characteristics: infects skin, nails and hair -secrete keratinase-----digest keratin -Pathogen: Microsporum, Epidermophyton, Trichophyton Disease: Dermatophytoses - S/Sx: irritation, scaling, redness - tinea capitis --- scalp - tinea barbae --- beard area - tinea cruris --- groin (jock’s itch) - tinea corporis --- body (ringworm) - tinea pedis --- feet( athlete’s foot) - tinea ungium --- nails (onychomycosis) - tinea versicolor --- body

Reservoir: humans, animals, soil Transmission: direct, indirect contact with lesions - spore enter the skin breaks, moist areas Diagnosis: KOH smear - culture ---- Sabouraud Dextrose Agar Treatment: keep infected area clean and dry - antifungal: miconazole, clotrimazole, ketoconazole Prevention and Control: - maintain good hygienic practices - keep susceptible areas of the body clean and dry

B. CANDIDA ALBICANS Characteristics: common commensals of humans - found in mouth, stool, vagina - opportunistic pathogen Predisposing factors: -- Intrinsic factors: a. Cellular defect (immunodeficiency) b. Malignancies c. Age (elderly and young) d. AIDS -- Extrinsic factors: a. Wide use of broad spectrum antibiotics b. Immunosuppressive drugs c. Cytotoxic drugs, surgery

• Disease: oral thrush -- white plaques in the mouth cutaneous candidiasis -- redness and maceration of intertriginous area Genital candidiasis – pruritus and discharge, dysuria Diagnosis: organism in smear (KOH) Treatment: Antigungal drugs oral fluconazole (Diflucan)

NORMAL SKIN

QUIZ

1. 2. 3. 4. 5.

Rubella HPV TETANUS RABIES VARICELLA ZOSTER A—DNA B—RNA C– BOTH D– NONE

6. S. AUREUS 7. S. PYOGENES 8. P. AERUGINOSA 9. C. TETANI 10. M. LEPRAE A- GRAM (+) C- BOTH

B- GRAM (-) D- NONE