1. Bacterial infections of the Skin
Staphylococcal Infections
Streptococcal Infections
Acne
Burn Infections

2. 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

3. 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

4. Streptococcal infection

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

6. 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

7. 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

8. 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

9. 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).

10. Burn infections which are usually nosocomial account for 80% of deaths among burn patients
Eschar
Debridement
Diagnosis of burn bacterial infection: more than 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: …

11. 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

12. 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

13. 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

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

15. 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

16. 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

17. 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

18. 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: , 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

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

20. 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

21. 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

22. In chickenpox: the virus enters the upper respiratory tract and conjunctiva
In 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

23. 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

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

25. 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)

26. Transmission is by direct contact and by fomites

27. 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)

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

29. 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

30. 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

31. 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

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

33. 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

34. 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

35. 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

36. 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

37. 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)

38. 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

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

40. 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