Presentation on theme: "MICR 201 Microbiology for Health Related Science"— Presentation transcript:
1 MICR 201 Microbiology for Health Related Science Microbiology- a clinical approach by Anthony Strelkauskas et al. 2010Chapter 26: Infections of the skin and eyes
2 Why is this chapter important? Skin and eyes are in contact with potentially pathogenic organisms all the time.Alterations of skin and eyes can represent a psychological burden.Infections of the eyes can lead to blindness.
4 Anatomy of skin Largest organ in the body. Barrier between our body and the outsideFirst line of defense against invading microorganismsOuter layer (epidermis) comes into direct contact with the environment.Constant shedding of cells keeps pathogens from successfully attaching to the skin.Skin gets infected when surface is disrupted.Exceptions: some worm infections; schistosomiasis, hookworm infection
5 Anatomy of skin Close access to blood system Surface penetrated by hairs and glandsSite of infections
6 Skin lesions Four main types of skin lesions: Macules Papules Vesicles Pustules
7 Bacterial infections of the skin in burnpatients
8 Staphylococcus aureus Gram+cocci in clustersCatalase +Facultative anaerobeSalt tolerantCoagulase +LeukocidinExfoliative toxinProtein A (captures antibodies)Golden-yellow coloniesAntibody (Fc region)SAYPrA
9 Staphylococcal skin infections FolliculitisInfections of hair folliclesStyFolliculitis of an eyelashFuruncle (boil)Abscess; pus surrounded by inflamed tissueAbscessInflammation of tissue under the skin, accumulation of pus, walled off
10 Staphylococcal scalded skin syndrome (SSSS) Caused by exotoxinExfoliatinsMostly in children < 2 yearsGood prognosis and long lasting immunity
11 Streptococcus pyogenes Gram + cocci in pairs and chainsCatalase negativeFacultative anaerobebeta-hemolytic streptococciGroup A antigenM protein (adherence and anti- phagocytic)Streptolysin OHyaluronidaseStreptokinaseDNAseErythrogenic toxin (phage encoded)Responsible for red rash of scarlet fever!
14 Acne Comedonal acne Inflammatory acne Nodular cystic acne Gram + rods Occurs when sebum channels are blocked by shedded cellsInflammatory acnePropionibacterium acnesGram + rodsAnaerobicSkin floraNodular cystic acne
15 Acne pathogenesis and treatment Propionibacterium acnes utilizes glycerol in sebum and produces fatty acids (fermentation!)Fatty acids are pro-inflammatoryNeutrophils are attracted further contributing to inflammationTreatmentbenzoyl peroxide (antiseptic, dries out acne lesions)Antibiotics (erythromycin, clindamycin)Isotretinoin (reduces sebum production, TERATOGENIC, 30% of newborns with severe damage)
16 Gangrene Ischemia Necrosis Gangrene Gas gangrene Loss of blood supply to tissueNecrosisDeath of tissueGangreneDeath of soft tissueGas gangreneClostridium perfringens, gram-positive, endospore-forming anaerobic spore forming rod, grows in necrotic tissueProduces phospholipase, proteinase, hyaluronidaseProduce also hydrogen gasTreatment includes surgical removal of necrotic tissue and/or hyperbaric chamberIn addition antibiotics such as penicillin and clindamycin
18 Viral infections of the skin ExanthemAerosol infection viremia skin manifestationSkin tumors (warts)MeaslesRubellaSmallpox (variola)Chickenpox and shinglesHerpes simplex virus type 1Warts
19 Measles Extremely contagious infection Caused by single-stranded RNA virusTransmitted by respiratory routeCold symptoms and feverViremiaMacular rash, raised spots, Koplik's spots in oral mucosaRash begins on face, affects trunk and extremities15-25% mortality rate in developing countriesUp to 15% of cases of measles have complications - Otis media, sinusitis, pneumonia, sepsis, encephalitisPrevented by vaccination
20 Rubella (German measles) Very mild or asymptomatic infectionLow-grade fever, lymphadenopathy, and faint macular rash.Very serious in pregnant womenCan cause congenital abnormalities in fetus (embryoathy)Infected individual contagious for 8 days before and 8 days after appearance of rash.
21 Smallpox (Variola) Infection caused by a DNA poxvirus. Two forms of smallpox:Variola major – mortality rate 20% or higherVariola minor – mortality rate 1%Vaccinatiom: side effects, 1-2 deaths/millionSmallpox has effectively been eradicated from the entire world; last victim in Somalia in 1977Only reservoir is humans; should be no more casesStocks of smallpox virus mean further infections are possibleDecreased herd immunity to smallpox increases the possibile potential as bioweapon
23 Smallpox: Pathogenesis Dominant feature is the appearance of papulovesicular rash and pustules.Incubation period is usually days.Can be 4-5 daysAbrupt onset of fever, chills, and muscle achesRash appears 3-4 days later.Papulovesicles most prominent on the head and extremities.Become pustular over days.Death from smallpox results from:Overwhelming virus infectionBacterial superinfection
24 Summary of viral infections Measles (measles virus, Koplik’s spots, subacute panencephalitis)Rubella (rubella virus, embryopathic)Small pox (variola virus, up to 30% mortality)Chicken pox and shingles (Varizella Zoster virus, latency dorsal root ganglion)Herpes simplex virus (HSV 1, latency trigenimal ganglion and recurrence)Warts (Papilloma virus, cancer)
25 Fungal infections of the skin CandidiasisDermaphytosis
26 Infections of the eyes Pink eye HSV1 River blindness Contact lenses (Pseudomonas)River blindness
27 Neonatal eye infections Infected by the mother during vaginal birthNeonatal gonorrheal ophthalmia by Neisseria gonorrhoeae infectionChlamydia trachomatis can also infect the eyes of newborns.Both infections cause large amounts of pus to form in the eyes.Causes ulceration and scarring of the cornea if not treatedCommon practice to treat eyes of newborn infants with erythromycin.
29 Eye infections treatment Topical eye drops and ointments containing erythromycin or gentamicin are effective against acute bacterial conjunctivitis.Fluoroquinolones can be used for eye infections caused by Pseudomonas.Quinolones such as ciprofloxacin useful for all types of eye infection.
30 LOAIASIS Parasitic worm Loa loa African rain forest Transmitted by bite of deer flyMigrate from tissue to eyeGrow up to an inch and easily seen
31 Chapter 26 key conceptsSkin is an impermeable barrier to almost all pathogens.A wide variety of bacteria can cause infection of the skin, with necrotizing fasciitis being one of the worst infections.Bacteria can infect hair follicles, sebaceous glands, and sweat glands.Viral pathogens also require a portal of entry to infect the skin.Viral infections that cause lesions on the skin include measles, rubella, smallpox, chickenpox, herpes simplex type 1, and human papillomavirus.Fungi are always present on the skin but rarely cause infection.
32 Chapter 26 key conceptsThe most common fungal infection of the skin is candidiasis.Dermatophytosis can be seen as ringworm, athlete’s foot, or jock itch.One of the most common parasitic infections of the skin is leishmaniasis.Eyes are infected through direct exposure to pathogens.A common eye infection and leading cause of blindness is trachoma, which is caused by Chlamydia trachomatis.Parasitic infections of the eye include loaiasis.32
33 Final Examination – Wednesday, June 12, 2013 10:45am – 1:15pmLecture, Chapter End Self Study Questions100 Multiple Choice Questions: 2 points each x 100 = 200 points~65%: Chapters 14-26~35%: Chapters 1-13Please bring Scantron and No. 2 pencil
34 CORRECTION – Chapter Question Chapter 22 Infections of the Digestive System1. The most common source of gastrointestinal infection in the developed world isA. SalmonellaB. ShigellaC. EscherichiaD. CampylobacterE. Staphylococcus aureusCorrect answer is D. Campylobacter