Bacterial infections of the Skin Staphylococcal Infections Streptococcal

Bacterial infections of the Skin • • Staphylococcal Infections Streptococcal Infections Acne Burn Infections

Staphylococcal infections • strains of Staph colonize the skin and upper respiratory tract of infants within 24 hrs of birth • Half of adults and children are nasal carriers of S. aureus • Hair follicle infection • Folliculitis-pimples (pustules) –sty • Lager and deeper pus filled-abscess • Exterior abscess is known as furuncles or boil • Further Spread infection particularly on the neck and upper back creates a massive lesion called carbuncle

• Staphylococcal infections are easily transmitted • Asymptomatic carriers, hospital personnel and hospital visitors can spread staphylococci via the skin and nasal droplets and fomites • Infectious dose • 5 million must be injected into the skin to cause infection • 100 only if soaked into suture and tied into the skin

Streptococcal infection

Skin infections: Streptococcus pyogenes • Scarlet fever (scarlatina) – Temperate phage – Red producing toxin (erythrogenic); streptococcal pyrogenic exotoxins – 3 different types – Antigenic

Streptococcal gangrene Infection of the subcutaneous tissue and fascia (fat between the connective tissue and muscles) Debridement and antibiotic Flesh eating bacteria: Group A streptococci causing Fasciitis

Mixed staphylococcal and Streptococcal infections • Pyoderma and Impetigo (highly contagious pyoderma) • Pyoderma: pus producing skin infection caused by staphylococci, streptococci and corynebacteria, singly or in combination • Impetigo caused by staphylococci, streptococci or both occurs exclusively in children • Easily transmitted on hands, toys and furniture • Easily treated with penicillin and rarely cause fever • skin pigment can be lost permanently

Acne • Propionibacterium acnes, Gram positive, non spore former, anaerobic • Male sex hormones that stimulate sebaceous glands to increase in size and secrete sebum • Mo feed on sebum • Ducts become inflamed • Blackheads: mild form of acne • Cystic acne: the plugged ducts become inflamed, rupture and release of secretion • Bacteria especially Propionibacterium acnes infect and cause more destruction, by lipase that split free fatty acids off from the skin lipids • Tetracycline • Accutane: inhibits sebum production for several months after treatment is stopped

Burn infection • Pseudomonas aeruginosa is the prime cause of life threatening burn infection, Serratia marcens and species of Providencia • Gram negative, motile, aerobic rods, in soil, water, plants and animals, produce a sweet or grape like odor, Pyocyanin (greenish), pyoverdin (bluish), grows at 42 C, elastases, proteases, hemolysins, exotoxin A (Tissue necrosis).

• Burn infections which are usually nosocomial account for 80% of deaths among burn patients • Eschar • Debridement • Diagnosis of burn bacterial infection: more than 10 000 bacteria per gram of eschar • P. aeruginosa: Green discoloration, tissue killing toxins that erode skin • It is extremely resistant to antimicrobial drugs and has been found growing in surgical scrub solutions • Treatment: …

Viral skin infections • Rubella (German measles) • Togaviridae, enveloped polyhedral, positive sense RNA • Mildest human viral disease that cause skin rash; the main symptom (exanthema) • A rash the main symptom of rubella appears first on trunk 16 to 21 days after infection • But the virus spreads in the blood and other tissues before rash appears • Infected adult women: temporary arthritis and arthralgia, less in adult men

• Congenital rubella syndrome • Damage of the fetus organs systems during the first 8 weeks of pregnancy • After the 8 weeks damage is rare • Stillborn, suffer from deafness, heart abnormalities, liver disorders and low birth weight

• Infants infected before birth are rubella carriers • They excrete viruses and expose the hospital staff and visitors, pregnant women to the disease • MMR VACCINE • Life attenuated virus • Vaccinated children pose no threat to mothers who are susceptible and pregnant • The vaccine induce life long immunity • Rubella vaccine can cross the placenta and infect the fetus • However it is not teratogenic

• Four fold increase in the titer of Ig. M used to identify newborn carriers and assess immunity of pregnant women exposed to rubella

Transmission • Transmission is mainly by nasal secretions shortly before and for about a week following the appearance of the rash • It is highly contagious among children spread by direct contact among children aged 5 -14 years • Second immunisation is recommended for females before they become sexually active

Rubeola: Measles • Febrile (fever) with a rash, raise red rash; caused by T cell reaction with viral infected cells in small blood vessels • Paramyxoviridae, negative sense RNA, enveloped helical • The virus invades lymphatic tissue and blood • The virus enters the body via the nose, mouth and conjunctiva • Symptoms appear in 9 -11 days in children and 21 days in adults

Sign and Symptoms • Koplik’s spots (white spots with central bluish specks) appear first before the other symptoms appear, fever conjunctivitis and cough • Rash from the forehead, upper extremities, trunk and lower extremities • If the virus invades the lungs, kidneys or brain the common childhood disease is often fatal

Complications • The most common complication is URT and middle ear infection • Complications: measles encephalitis 1 -2/1000 and less than 30% mortality rates and leaves less than third with brain damage • Subacute sclerosing panencephalitis (SSPE) • 1: 200 000, always fatal • Persistence of measles virus in the brain tissue and cause death of nerve cells • Progressiv. In poorly nourished children, measles cause intestinal inflammation e mental deterioration and muscle rigidity • with extensive protein loss and shedding viruses in stools • MMR vaccine

• Rash from the forehead, upper extremities, trunk and lower extremities • Upper respiratory and middle ear infections: the most common complications • Measles encephalitis and SSPE

• The virus is highly contagious • The portal of entry is the respiratory tract • Coughing and sneezing: 99% susceptible of encountering the infection • Diagnosis by symptoms • Treatment alleviation of the symptoms and dealing with complications • Secondary bacterial infection: antibiotics

Chickenpox and shingles • Varicella (chikenpox) zoster (shingles) • Herpesvirus • Varicella; occurs in children; Zoster; sporadic in older and immunocompromised • Although chickenpox is a mild it might be fatal • Invade and damage cells that line blood vessels and lymphatics • Circulating blood clots and hemorrhages are common • Death from varicella pneumonia • Liver, spleen

• In chickenpox: the virus enters the upper respiratory tract and conjunctiva • In 14 -16 days after exposure, small irregular rose colored lesions appear • The fluid in them becomes cloudy and they dry and crust over a few days • The lesions are very important portals of entry to S. aureus

• Shingles painful lesions like those of chickenpox are confined to a single region supplied by a particular nerve, latent viruses acquired during a prior case of chickenpox • The virus reside in the ganglia in the cranium and near the spine • Pain and burning before lesions appear • Indistinguishable from chikenpox

• Infection can spread by respiratory secretions and contact with moist lesions not crusts • Vaccine: available but concerns about latency

Warts • Human papillomaviruses, double stranded DNA, Papovaviridae, naked polyhedral • Attack mucous membranes and skin • Dermal, laryngeal and genital warts • Genital warts , condylomata acuminata, do not become malignant • but some genital warts , depending on the strain , invisible chronic infection, might cause cervical cancer • 99% of cervical cancer is caused by genital warts • It is now classified as sexually transmitted disease • Juvenile onset laryngeal warts (large but benign)

• Transmission is by direct contact and by fomites

• Crotherapy • Caustic Chemical agents: PODOPHYLIN, SALICYLIC ACID, GLUTARALDEHYDE • 5 -FLUOROURACIL AND INTERFERON • Gardasil, a new vaccine against 4 strains of HPV • RECOMMENDED TO BE USED IN GIRLS (9 -26 YEARS)

• Immunological tests and microscopic examination of the tissue (diagnosis of warts) • Enzyme immunoassay and immunofluorescent antibody tests

Fungal infection • Fungi invading keratinised tissue is called: Dermatophytes and the disease is called dermatomycosis • Epidermophyton, microsporum, trichophyton • They cause various types of ringworms and attack the skin, nails and hair

Fungal infection • Ringworm: called so because of the shape of the lesion caused by it • It involves the skin hair and nails and most are named according to where they are found • None result in a severe disease but they are unsightly, itchy and persistent

• • • Tinea corporis: body ringworm Tinea unguium: nails ringworm Tinea capitis: scalp ringworm Tinea pedis: Tinea cruris (groin ringworm, jock itch), pubic area • Tinea barbae (beard) barber itch

• None of the dermatomycoses results in severe diseases and usually does not invade other tissues • They are itchy unsightly and persistent

• REMOVING DEAD TISSUE AND USING TOPICAL. Nailbeds: Griseofulvin orally • Athlete’s foot: topical miconazole • Diagnosis is by microscopic examination. Spores in the lab not on the body

Bacterial eye diseases • Opthalmia neonatorum (newborn conjunctivitis) • Pus forming infection of the eyes of the newborn • Caused by Neisseria gonorrhoeae and Chlamydia trachomatis can result in blindness • Penicillin resistant tetracycline is used • Preventive measures: a drop of silver nitrate solution kills gonococci • But not efffective against chlamydias • Penicillin, tetracycline and erythromycin is effective against most bacterial causes of ophthalmia neonatorum

Bacterial conjunctivitis • Bacterial conjunctivitis or pink eye • Inflammation of the conjunctiva caused by organisms such as • S. aureus, Streptococcus pneumoniae, Neisseria gonorrhoeae, Pseudomonas sp and Haemophilus influenzae

• It is extremely contagious especially among children • Spreads rapidly through schools and day centers • Topically applied sulfonamide ointment is an effective treatment • Children should not return to school until their infection is completely eliminated

Wound infections: Gas Gangrene • • • Mixed infection of Clostridium spp Clostridium perfringens Associated with deep wound Collagenases, proteases, and lipases The onset is sudden (12 -48 hrs after injury)

Clostridium perfringens • Spore forming Gram positive bacilli • It cause invasive infections • Produce a large variety of toxins and enzymes that result in a spreading infection • Toxins: have lethal, necrotizing and hemolytic properties

Toxins • Alpha toxin: lecithinase • Theta toxin: hemolytic and necrotising effect • DNase, and hyaluronidase • Some produce powerful enterotoxin

Gas gangarene • Often is a mixed infection • The onset of gangrene is sudden • Ferment muscle CHO and produce gas mainly hydrogen • Foul odor • Usually follows illegal abortion under unsanitary conditions • Penicillin, removing dead tissue (or amputated) • Hyperbaric oxygen chamber