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 marcenscens 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 IgM 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 ProgressivIn 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