Here is the first Microbiology lecture in this system given by our lovely Dr Hani Masaadeh. This sheet is complete slides + Dr Comments, so you don t need to go back to the slides. Here is some dermatological Terminology which is very important just for your understanding but not required in the lecture. Flat, circumscribed, discolored area Elevated, solid area Elevated fluid filled area Elevated, flat-topped area Discrete, elevated, pus-filled area NB: this info is from Pulse s sheet Now let s start our mission Macule 5 mm Papule >5mm Nodule Blister 5mm Vesicle >5mm Bulla Plaque pustule
Lecture objectives; MSS micro lectures as whole not only this one: 1) Normal skin flora: some types of bacteria and fungi are normal flora of skin. 2) Skin microbiology: you should know pathogenic bacteria which colonize in our skin, the non-pathogenic and the opportunistic. 3) Common skin infections: you should know the pathogenicity, the epidemiology, the treatment and others 4) Emergency skin infections: some infections are called emergency skin infections as the management is emergency 5) Less common infections: the unusual infections, and 6) Non-bacterial infections: such as fungal infections and parasitic infections Natural Defenses of the skin the first line of the defense. Keratin: inhibit the growth of some microorganisms Skin sloughing: as external defense Sebum: low ph, high lipid; also inhibit the growth of microorganisms, Low ph inhibits all microorganisms except Acid fast bacteria, but it increases the growth of the fungi as it needs low ph. Sweat: low ph, High salt and Lysozyme: which digests peptidoglycan, which present gram positive bacteria cell wall as thick layer and gram negative bacteria cell wall as thin layer, you should know the composition of cell wall in both G+ & G- Normal Flora of the skin Large numbers of microorganisms live on or in the skin, usually these bacteria and the fungi are non-pathogenic, sometimes they will become pathogenic in immunocompromised patients. Numbers of bacteria are determined by location and moisture content, in moisture cases, the number of the bacteria is more than dry cases, because the humidity will increase the growth of the microorganisms.
Skin flora microbes are Opportunistic pathogens which become pathogenic in immunocompromised patients. Most skin flora can be categorized in three groups; 1- Diphtheroids: when we see suffix OID it means non-pathogenic, Diphtheriae is highly pathogenic, but when we say Diphtheroid we mean the diphtheria which is non-pathogenic. 2- Staphylococci: mostly staph. Epidermidis and other staph species which are non-pathogenic and a few numbers of staph aureus also present in the skin. 3- Yeasts: different types of yeasts present in our skin e.g. Candida albicans present in human mouth and in or skin. But in some cases we found high number of yeast which becomes pathogenic. Some types of normal flora:- Propionibacterium acnes: causes Acne its anaerobic bacteria which sometimes cause infections. Corynebacterium species are non-pathogenic except C. Diphtheriae. Staphylococci: staph. Epidermidis and staph. Aureus Streptococci sp.: some species of streptococci are Beta-hemolytic, Alphahemolytic and Gamma-hemolytic, usually B-hemolytic are highly pathogenic bacteria esp. group A. Candida albicans (Yeast) and Many others. Diphtheroids: Named for their resemblance to corynebacterium diphtheria Toxin of the bacteria inhibits elongation factor 2. Gram positive bacillus bacteria with varied shape and low virulence Non-toxin producers, as we said before OID means non-pathogenic so they have no toxin. Responsible for body odor caused by the bacterial breakdown of sweat. Common diphtheroid is propionibacterium acnes.
STAPHYLOCOCCI Gram positive, salt tolerant organisms, grow in the presence of salt relatively Avirulent such as s. epidermidis and s. saprophyticus but Can cause serious disease in immunocompromised people, such as septicemia caused by s. epidermidis. Principle species is staph epidermidis, Functions on the skin to prevent colonization of pathogenic flora. Maintains balance among skin flora. FUNGI (Yeast): we will have one lecture about the fungal skin infections Tiny lipophilic yeast universally found on normal skin. Usually from late childhood throughout life. Fungi shapes vary among strains. Usually round or oval; however, can be short rods. Fungi found on the skin are generally harmless but Can cause skin conditions such as rash or dandruff. PROPIONIBACTERIUM ACNES: Gram positive rod, Digests sebum, Attracts Neutrophils Neutrophil digestive enzymes cause lesions pus pockets Acne; most common skin disease in humanss Oil based cosmetics worsen the disease No effects of diet
ACNE TREATMENTS: healing by antiseptic not detergent as: Benzoyl peroxide dries plugged follicles, kills microbes Tetracycline (Antibiotic) Accutane inhibits sebum formation Folliculitis Symptoms Presents as small red bump or pimple. Infection can spread from infected follicle to adjacent tissues, it s highly contagious. Causes localized redness, swelling and tenderness. The lesion produced is called a Furuncle. Most are caused by staph aureus (80 to 90%) HAIR FOLLICLE INFECTIONS SCALDED SKIN SYNDROME Staphylococcal scalded skin syndrome (SSSS) Toxin mediated disease (Exotoxin) Occurs primarily in infants potentially fatal
SYMPTOMS Skin appears to be burned (scalded) Begins as generalized redness other symptoms incl. malaise, irritability, fever Nose, mouth, and genitalia may be painful before other indicators become apparent. Within 48 hours of infection, symptoms manifest (rapidly) Skin becomes red and wrinkled Large fluid filled blisters appear Skin is tender to the touch and may feel like sandpaper CAUSATIVE AGENT: Bacterial agent is Staph aureus. The disease is due to the production of toxins produced by S. Aureus, toxins are called Exfoliatins. Exfoliatins destroy integral layers of the outer epidermis Toxins are coded either by plasmid or on the bacterial chromosome EPIDEMIOLOGY: 5% of S. aureus strains produce exfoliatins. Disease can appear in any age. Most frequently in infants, the elderly and immunocompromised. Transmission is generally person-to-person. Easily transmitted. Disease is usually isolated; however, small epidemics can occur in nurseries. We can isolate the bacteria by using To isolate staph aureus we use catalase test first, to differenciate b/w staph and strep. And to isolate staph specifically we use coagulase test, to detect coagulase enzyme. PREVENTION AND TREATMENTS:- Only preventive measure is patient isolation Patients are in protective isolation
>>>>> Helps limit spread of bacterial agent. >>>>> Limits patient exposure to potential secondary pathogens Treatment incl. Bactericidal antibiotics Antistaphylococcals such as penicellinase-resistant penicillin Treatment also incl. removal of dead skin to prevent 2dry infection. 2dry infection may be from pseudomonas or strep B-hemolytic group A STREPTOCOCCAL IMPETIGO or PYODERMA INFECTION Pyoderma means: pyo = pus, derma = skin infection Characterized by pus production Pyodermas can result from insect bites, burns and scrapes - Such injuries can be so slight that they miss detection Impetigo is the most common type of pyoderma CAUSATIVE agent: Most cases incl. epidemics are caused by streptococcus pyogenes S. aureus is also implicated as a causative agent S. pyogenes is a gram positive, B hemolytic streptococci, often referred to as Group A due to presence of group A cell wall polysaccharide. Streptococcus species also form the characteristic chain formation Beta-hemolytic Complete hemolysis, Alpha-hemolytic Incomplete hemolysis and Gamma-hemolytic no hemolysis We can identify this bacterium by using Q test which is highly sensitive. And other test as general is catalase test.
ROCKY MOUNTAIN SPOTTED FEVER: Unusual disease in here Jordan First recognized in rocky mountain region in US. Representative of a group of rickettsial diseases Transmitted my ticks SYMPTOMS: Distinguished by initial rash of faint pink spots. Appears first on palms, wrists, ankles, and soles of feet. Rash eventually spreads to other parts of the body Spots become raised bumps and are hemorrhagic Shock or death can occur when certain body systems become involved especially the heart and kidney like septicemia involving the heart. CAUSATIVE agent: Rickettsia rickettsii Obligate, intracellular bacterium (strict), requires host organism for survival Gram negative, non-motile, coccobacillus. Bacteria are very small and often difficult to see in gram stain we use special stain and we can use scanning electron microscope. EPIDEMIOLOGY: Zoonotic disease occurs in areas in US, Canada and Mexic Highest incidence in US is in south Atlantic and south-central US Maintained in several species in nature Primarily in ticks and certain mammals
Main vectors incl. wood tick Dermacentor andersonii and the dog tick dermacentor variabilis (not mandatory to memorize these names just know its zoonotic disease and causative agent is Rickettsia rickettsii) Tick vectors remain infected for life PEVENTION: No vaccine currently available. Prevention should be directed towards: 1. Avoiding tick-infested areas 2. Using protective clothing 3. Using tick repellents containing DEET (type of detergent) 4. Carefully inspect body, especially dark, moist areas 5. Remove attached ticks carefully 6. Avoid crushing and contaminating bite area TREATMENT: Antibiotics are highly effective in treatment if given early Doxycycline (DOC) and chloramphenicol used most often Without treatment, overall mortality reaches approximately 20% With early diagnosis and treatment, mortality rates drop to less than 5% WHY DOES SKIN IS INFECTED? The skin is the largest organ in the body so there are multiple types of bacteria which are normally present on the skin For example: Staphylococcus epidermidis and yeasts. The presence of bacteria doesn t automatically lead to a skin infection.?? What is the difference b/w colonization and infection??? COLONIZATION: Bacteria are present, but causing no harm INFECTION: Bacteria are present and causing harm.
A break in the epidermal integrity can allow organisms to enter and become pathogenic. This can occur as a result of trauma, ulceration, fungal infection, skin disease such as eczema. IMPETIGO A highly infectious skin disease, which commonly occurs in children. CAUSATIVE agent: The causative organism is usually staphylococcus Aureus (>90% cases), but less often can be strep. Pyogenes. (B-hemolytic group A) Begins as vesicle, which may enlarge into a bulla. Weeping, exudative area which characteristic Honey colored or golden, gummy crusts, which leave denuded red areas when removed. May present as macules, vesicles, bullae or pustules. Bullae are more prominent in staphylococcal infection and in infants. Because skin of infant is more sensitive. TREATMENT: Mild localized cases use topical antibiotic as polyfax Widespread or more severe infections use systemic antibiotics, such as flucloxacillin (or erythromycin if penicillin allergic) FOLLICULITIS: Inflammation of the hair follicle. Presents as itchy or tender papules and pustules at the follicular openings. Complications incl. abscess formation and cavernous sinus thrombosis if upper lip, nose or eye affected.
CAUSATIVE agent: Most common cause is Staph Aureus. Other organisms to consider include: Gram negative bacteria as pseudomonas usually in patients with acne who are on broad spectrum antibiotics. Pseudomonas (Hot tub folliculitis) Yeasts (Candida and pityrosporum). TREATMENT: Topical antiseptics such as chlorhexidine. Topical antibiotics, such as Fusidic Acid or mupirocin. More resistance cases may need oral antibiotics such as flucloxacillin Hot tub folliculitis Ciprofloxacin Gram negative Trimethoprim broad spectrum CELLULITIS: Common disease especially for adult Infection of the deep subcutaneous layer of the skin. Presents as a hot, tender area of confluent erythema of the skin Can cause systemic infection with fever, headache and vomiting. Erysipelas is more superficial and well demarcated border. (Look at the picture in the next page).
CAUSATIVE AGENT: Streptococcus Group A strep pyogenes. Others include group B, C, D strep, staph Aureus, Haemophilus influenzae (children) and anaerobic bacteria (eg. Pasteurella spp. After animal bite) TREATMENT: Oral flucloxacillin or erythromycin if allergic Co-amoxilav in facial cellulitis If severe systemic upset, may require admission for IV antibiotics After the acute attack has settled, especially in recurrent episodes consider the underlying cause. (PIC: orbital cellulitis refer urgently) FURUNCULOSIS (BOILS) & CARBUNCLES Deeper staphylococcal abscess of the hair follicle Coalescence of boils leads to the formation of a carbuncle Treatment is with systemic antibiotics and may need incision and drainage. Consider looking for underlying causes, such as diabetes. Esp DM with alcerations. Erysipelas: more superficial than cellulitis and well demarcated (clear border b/w infected and non-infected areas). The END, forgive me any possible mistake. And sorry for being late. Cilmi Faradheere, Awn Good Luck all