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MicroBiology, Skin Diseases Caused by Microorganisms Pt2, Staphylococcus…
MicroBiology
Infectious Diseases
Infectious Diseases Affecting the Skin and Eyes
Defenses
Skin
Layers
Epidermis
Epithelial cell have keratin
3+ epithelial layers are below the stratum corneum
Surface of skin is keratinized
Dermis
Sebaceous glands
Fibroblasts, nerves, blood vessels, hair follicles, immune cells
Connective instead of epithelium
Defenses
Sebum
from sebaceous glands low Ph (Oily Sap)
Peptides
Sweat
High salt (Salt drops)
Keratined Surface (Yellow, Hardened Rocky Surface)
Eyes
Conjunctiva
secretes an oil- and mucus-containing fluid that protects the eye
Tears
: lysozyme and lactoferrin, a major protective feature
Corenea
5-6 layers of epithelial cells
Immune privledge
- Reduced innate immunity
Normal Biota
Eyes
Diverse in bacteria
Corynebacterium is dominant genus
Eye microbiome resembles that of the skin
Diphtheroids, Coagulase, negative staphylococci, micrococcus, nonhemolytic streptococci
Skin
Hundreds of species
Distribution variable in different regions
Large differences among individuals
An individual's own skin microbiota is stable over time
Diseases Caused by Microorganisms
Eyes
Conjunctavitis
Signs and symptoms:
a.Most bacterial infections produce a milky discharge
b.Viral infections produce a clear exudate
Causative agents and their transmission
Viral conjunctivitis: usually caused by adenoviruses
Both bacterial and viral conjunctivitis are highly contagious
Neonatal eye infection—Neisseria gonorrhoeae or Chlamydia trachomatis
Prevention and treatment:
Good hygiene, antibiotic treatment
Trachoma
1.Preventable form of blindness
2.Transmitted by contaminated fingers, fomites, fleas, hot dry climate
3.Mild discharge, pebbled appearance to inner upper eyelid
4.Early treatment is effective and prevents complications
Keratitis
1.Keratitis is a more serious eye infection than conjunctivitis
2.Herpes simplex virus type 1 (HSV-1) and HSV-2
3.Gritty feeling, conjunctivitis, sharp pain, sensitivity to light
4.Recent cases involving contact lens wearers; hygiene is critical; Acanthamoeba
River Blindness
1.Chronic parasitic helminth infection
2.Onchocerca volvulus—transmitted by small biting black flies
3.Larvae deposited into bite wound; microfilariae migrate to the eye
4.Damage to tissue is from Wolbachia bacteria living inside the worms
5.Ivermectin treatment; insecticide to kill flies
Skin
Impetigo:
Caused by Staphylococcus
aureus
a. Pathogenesis and virulence factors
i. Exfoliative toxins A and B: attacks protein that binds cells in skin
ii. Coagulase
pyogenes
a. Beta-hemolytic; cause of strep throat, scarlet fever
b. Pathogenesis and virulence factors
i. Adhesins: M protein, LTA, capsule
ii. Hyaluronidase
Transmission and epidemiology
a. Direct contact, through fomites and mechanical vectors
b. Primarily preschool children
Culture and diagnosis
Visual inspection of lesions
Identification as described for MRSA, biochemical testing
Treatment: antibiotic that will target either causative organism
Prevention: good hygiene
Cellulitis
1.Fast-spreading infection of the dermis and subcutaneous tissue
2.Signs and symptoms: pain, tenderness, swelling, and warmth; fever may occur
3.Causative organisms: S. aureus and S. pyogenes
4.Immunocompromised people and those with cardiac insufficiency are at high risk
5.Treatment is through oral or IV antibiotics
6.Surgical debridement in severe cases
MRSA and Soft Tissue Infections
a.
Highly virulent
, can be part of “normal” biota
b.Gram-positive coccus; sturdiest nonendospore formers
Signs and symptoms
Transmission and epidemiology
a. all kinds of surfaces
b.Persons keep infections covered
Pathogenesis and virulence factors
Coagulase, Hyaluronidase, Staphylokinase, DNase, Lipases
Culture and diagnosis
Diagnosis- Polymerase chain reaction, alt isolation of blood agar;
Treatment
drain pus; more than one antibiotic
Staphylococcal Scalded Skin Syndrome (SSSS)
1.Dermolytic condition caused by Staphylococcus aureus
2.Affects mostly newborns and babies
3.Systemic form of impetigo
4.Desquamation of the skin
5.Exfoliative toxins A and B cause bullous lesions, desquamation
6.Must be distinguished from toxic epidermal necrolysis (TEN)
Gas gangrene
caused by Clostridium perfringens (clostridial myonecrosis)
Prevention and treatment
Cleaning and surgical repair of wounds;Broad-spectrum antibiotics;Hyperbaric oxygen therapy
Transmission and epidemiology
Signs and symptoms
Anaerobic cellulitis - Damaged necrotic muscle tissue or myonecrosis
Toxins and gas
Pathogenesis and virulence factors
Vesicular or pustular rash diseases
reactivation of latent virus in ganglia
a.Causative agent: HHV-3, aks varicella-zoster virus
b.Pathogenesis and virulence factors - Enters respiratory tract >bloodstream >disseminates to skin
c. Transmission and epidemiology
d. Prevention -Live, attenuated vaccine ; Shingrix (adults 50+)
Signs and symptoms
macular, papular, vesicular, and pustular
Causative agent:
variola virus, an orthopoxvirus
Pathogenesis and virulence factors
i. Invades nasopharyngeal mucosa and multiplies in lymph nodes
ii. Lesion occurs at dermal level; scars remain
Treatment:
cidofovir
Signs and symptoms
ii. Macules and papules to itchy fluid-filled vesicles
iii. Centripetal lesions
iv.Secondary infections may result; treat with antibiotics
v.Infection during pregnancy may result in birth defects
Infectious Disease Affecting
Section 17 Preparation for the Survey of Microbial Diseases
Categories of microbial identification techniques.
Phenotypic
enzymatic activities, physical conditions, antibiotics can effect it, chem comp of it's walls/membranes
Immunologic
Genotypic
Infectious Diseases Affecting the Respiratory System
The Respiratory Tract and Its Defenses
Upper
Lower
Defenses
Anatomical
Nasal hairs
ciliated epithelium of trachea and bronchi
mucus, cough, sneezing
swallowing
2nd and 3rd
Complement action in the lungs, increased levels of cytokines and antimicrobial peptides
small active molecules secreted to regulate, stimulate, suppress, and
control the cell development, inflammation, and immunity
macrophages in the alveoli of the lungs
clusters of lymphoid tissue in the tonsils
secretory IgA
Normal Biota of the Respiratory Tract
9 major bacterial genera
Strepococcus, prevotella, sphingomonas, pseudomonas, acinetobacter, fusobacterium,
megasphaera, veillella and staphylococcus
capable of causing serious disease are frequently part of “normal” biota
1.Streptococcus pyogenes, Haemophilus influenzae, Streptococcus pneumonia
2.Neisseria meningitides, Staphylococcus aureus
Lung microbiome is altered in patients with lung disorders
Normal biota is important for microbial antagonism
Upper Respiratory Tract Diseases Caused by Microorganisms
The common cold (“rhinitis”)
Sinusitis
Acute otitis media (ear infection)
Pharyngitis
Diphtheria
Diphtheria
Diseases Caused by Microorganisms Affecting the Upper and Lower Respiratory Tracts
Whooping cough (“pertussis”)
Respiratory syncytial virus infection
Influenza
Lower Respiratory Tract Diseases Caused by Microorganisms
Tuberculosis
(MDR-TB and XDR-TB)
Pneumonia
Exposition
Microbial Nutrition and Growth - Environmental Factors
Skin Diseases Caused by Microorganisms Pt2
Maculopapular rash diseases
Signs and symptoms
i. Koplik’s spots
ii. Maculopapular exanthem
iii. Subacute sclerosing panencephalitis (SSPE)
Causative agent:
Morbillivirus, single-stranded, enveloped RNA virus,
Wartlike eruptions
1. Viruses cause all warts
2. Warts (papillomas)
a.Benign, squamous epithelial growths
b.Human papillomavirus (HPV)
i. Common (seed) warts HPV-2, -4, -27, -29
ii. Plantar warts HPV-1
c.Spread by direction contact, autoinoculation
d.Harmless, resolve over time
e.Nonprescription salicylic acid or cryosurgery for removal
3.Molluscum contagiosum
a.Firm waxy nodules with milky fluids
b.Common in children; nodules on the face, arms, legs, trunk
c.Lesions can be disfiguring and widespread in immunocompromised patients
d.Poxvirus, enveloped, dsDNA
d.Poxvirus, enveloped, dsDNA
e.Direct contact, fomites, sexual contact
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Large pustular skin lesions
Leishmaniasis
a. Zoonosis transmitted by female sand fly
i. Leishmania tropica (cutaneous leishmaniasis)
ii. Leishmania braziliensis (mucocutaneous leishmaniasis)
b. Endemic to equatorial regions; dogs serve as reservoirs
c. Small red papule appears at the bite site and spreads into a large ulcer
Cutaneous anthrax
a. Bacillus anthracis endospores entering through small cuts or abrasions
b. Eschar formation
c. Penicillin and ciprofloxacin treatment
Ringworm (cutaneous mycoses)
1.Fungal dermatophytes cause mycoses that are confined to the nonliving epidermal tissues, hair and nails
2.Tinea, various locations
3.Causative agents
a. About 39 species in several genera
b. Direct microscopic examination required for diagnosis
4.Pathogenesis and virulence factors
a. Digest keratin
b. Spores may remain for years on fomites
5.Transmission and epidemiology: direct and indirect contact with infected animals; soil
6.Prevention and treatment
a. Avoid contact
Hand, foot, and mouth disease
1.Most common in babies and children under age 5
2.Sore throat, fever, malaise, spots inside mouth, spots on palms and soles
3.Most frequently: oxsackievirus
4.Transmitted: secretions and direct contact
5.Uncomplicated, no treatment, no vaccine
Staphylococcus aureus**
