Chapter 9 - Skin and Wound Infections - PHA211 PDF

PHA211 – Microbiological Basis of Disease Systems Clinically important bacteria Other Gram (+) cocci Gram (+) rods Chlamydia Gram (-) coc...

PHA211 – Microbiological Basis of Disease Systems Clinically important bacteria Other Gram (+) cocci Gram (+) rods Chlamydia Gram (-) cocci Mycoplasma Gram (-) rods Spirochetes Anaerobic organisms 2 Clinically important viruses 3 Clinically important fungi 4 Clinically important parasites 5 Systems 6 Learning outcomes ❑ List the pathogenic microorganisms, their general characteristics, classifications, nomenclature, methods of identification, pathogenicity factors and mechanisms of pathogenicity. ❑ Recognize the clinical picture caused by common pathogenic microorganisms, identify their etiology and relate to their basic management. ❑ State the suitable antimicrobial agents for treatment of different microbial pathogens and list preventive measures available for prevention of common communicable diseases including vaccines. 7  PHA211 – Microbiological Basis of Disease Chapter 9 Skin and Wound Infections  Outline I. Bacteria: II. Virus: 1. Bacilli 1. Herpesviruses 2. Streptococci 2. Varicella 3. Staphylococcus aureus 3. Rubella 4. Clostridium perfringens 4. Measles 5. Pasteurella multocida 5. Mumps 6. Propionibacterium acne 6. Human papillomavirus III. Fungi: 7. Parvovirus 1. Candida albicans 9  Some Definitions Wound infections-classification: ✓ Surgical wounds ✓ Traumatic wounds ✓ Burn wounds ✓ Chronic ulcers: ✓ Arterial/venous ✓ Diabetes neuropathy ✓ Pressure ulcers ✓ Bites: Skin Layers ✓ Animal ✓ Human ✓ Insects 10  Some Definitions Folliculitis Furuncle Cellulitis Carbuncle Impetigo Ecthyma Bacilli Common characteristics Shape Rod Motility Motile (flagella or sliding motility) Gram staining (+) Oxygen requirement Facultative anaerobes Catalase test (+) Polymyxin-Lysozyme-EDTA-Thallous acetate Culture media (PLET) agar Bacillus anthracis Important members Bacillus cereus Bacillus cytotoxicus 12 Bacillus anthracis bioterrorism Properties: ❑ Spore-forming ❑ Capsulated: Protein capsule (poly-D-gamma-glutamic acid) is key to evasion of the immune response. It feeds on the heme of blood protein hemoglobin using two secretory siderophore proteins, IsdX1 and IsdX2. ❑ At a genomic levels, B. anthracis strains present two characteristic plasmids: pXO1: contains the genes that encode for the anthrax toxin components: pXO2: encodes a five-gene operon (capBCADE: pathogenicity island) which synthesizes a poly-γ-D-glutamic acid (polyglutamate) capsule. 13  necrosis at the level of skin enter the body via WOUNDS (SOLDIER AND SOILEXAMPLE) Bacillus anthracis The three components of the anthrax exotoxins, PA, LF, and EF, are individually non-toxic, but they pair to form the two major virulence factors of B. anthracis: Lethal toxin (LT, composed of LF + PA) Edema toxin (ET, composed of EF + PA) PA is the cellular binding unit, and LF and EF are the catalytic units of the toxins. A combination of infection & toxemia. 14 Streptococci Common characteristics Ovoid to spherical Shape Occurring as pairs or chains Motility Non-motile Gram staining (+) Oxygen requirement Facultative anaerobes Catalase test (-) Culture media Blood agar Streptococcus agalactiae Important members Streptococcus pneumoniae Streptococcus pyogenes 15 Groups of Streptococci Group A Streptococci Group B Streptococci Ex: S. pyogenes Ex: S. agalactiae Activity: produce enzymes & toxins that dissolve blood clots, affect pus & WBC Presence: normally in the GI, movement, stimulate fever, lyse blood urinary & genital tracts cells Disease: in newborns during Infection: pharynx or skin, but the passage through the birth canal or resulting abscesses are usually temporary by health care workers Disease: when competing normal microbiota are depleted, or immunity is Diagnosis: ELISA impaired, or a large inoculum enables them to get a foothold Diagnosis: immunological tests to identify the presence of group A streptococcal antigens 16 Groups of Streptococci ACC to profile on blood agar -Hemolytic Other β-Hemolytic Streptococci Streptococci S. equisimilis: causes Viridans group pharyngitis Presence: normally in the S. anginosus: produces mouth, pharynx, GI, urinary abscesses & genital tracts TALI3 LA BARA B2ALBO PUS BACTERIA W IMMUNE CELLS Infection: opportunists producing purulent abdominal infections Disease: one cause of dental caries 17 Staphylococci Common characteristics Round Shape Bunches like grapes Motility Non-motile Gram staining (+) (staining darkly) Oxygen requirement Facultative anaerobes Catalase test (+) Culture media Enriched media containing broth &/or blood Staphylococcus aureus GOLDEN Important members Staphylococcus epidermidis Staphylococcus saprophyticus 18 Staphylococci They are hardy, being resistant to heat & drying.  They can persist for long periods on inanimate objects, which can then serve as sources of infection.  Frequent hand washing before & after contact with food or potentially infected individuals decreases the transmission of staphylococcal disease. 19  Staphylococcus aureus vegetative most virulent ❑ Properties: ✓ Part of the normal flora of certain mucous membranes (nares & vagina) & of the skin. ✓ The most virulent of the Staphylococci. opportunistic infection 20  Staphylococcus aureus ❑ Infection: wound or during surgery  penetration of the skin  abscess. bacterial infection: invasion and colonization ❑ Subsequent disease can be caused by: The actual infection; Toxins in the absence of infection (toxinosis); Or a combination of infection & intoxication. toxins released by bacteria both-most common 21  Staphylococcus aureus ❑ Pathogenesis: macromolecules, part of epithelial cell wall Initial attachment to fibronectin is mediated by fibronectin-binding proteins. Major injury is caused by the pore-forming -toxin  cell destruction by leaking their cytosol. -toxin also inserts in the polymorphonuclear neutrophils. Resistance to phagocytosis & the formation of a wall are aided by fibrinogen-binding clumping factor (Clf). fibrin wall-very hard walled lesion 22  Staphylococcus aureus ❑ Clinical significance: 23  Staphylococcus aureus ❑ Clinical significance: Localized skin infections:  Most common infections are small, superficial abscesses involving hair follicles (folliculitis) or sweat or sebaceous glands. Furuncles (boils) = subcutaneous abscesses formed around foreign bodies (ex: splinters); respond to local therapy. nasra men khashab Carbuncles = larger, deeper, multiloculated skin infections that can lead to bacteremia; require antibiotic therapy & debridement. stop it from becoming systemic Impetigo = localized, superficial, spreading crusty skin lesion (generally seen in children). golden in color 24  Staphylococcus aureus scrab from skin ❑ Laboratory identification: Gram grape like structure stain (+) ONLY ONE + Coagulase (+) Oxidase Staphylococcus Motility (-) (-) Staphylococcus Catalase aureus (+) 25 Clostridia Common characteristics Large, blunt-ended rods Shape Produce endospores Motility Motile Gram staining (+) Oxygen requirement Obligate anaerobes Catalase test (-) Culture media Anaerobically on blood agar Clostridium botulinum Clostridium difficile Important members Clostridium perfringens skin and wounds Clostridium tetani 26 Clostridia Spores are resistant to chemical disinfectants & may withstand UV irradiation or boiling temperatures for some time, although not standard autoclaving conditions (121°C for 15 min at increased pressure). 27  Clostridium perfringens ❑ Properties: ✓ Part of the normal flora of the vagina & GI tract. ✓ Spores are found in soil. ✓ Pathogenicity: secretes 12 exotoxins, 1 enterotoxin & other hydrolytic enzymes. depends on toxins and enzymes it produces ✓ Causes anaerobic cellulitis, myonecrosis (gas gangrene) & a common form of food poisoning (some strains). 28 Clostridium perfringens ❑ Exotoxins:  toxin: ▪ Most important ▪ Required for virulence in tissue ▪ Is a lecithinase (phospholipase C): degrades lecithin in mammalian cell membranes ▪ Causes lysis of endothelial cells, erythrocytes, leukocytes & platelets. cell leakage by necrosis (iNFLAMMATION- NON PROGRAMMED WAY) θ toxin (perfringolysin O): a cholesterol-dependent hemolysin & an important virulence factor. AN INTEGRAL PART OF THE CELL MEMBRANE Other exotoxins have hemolytic or other cytotoxic & necrotic effects, either locally or when dispersed in the bloodstream. 29  Clostridium perfringens ❑ Enterotoxin: A small, heat-sensitive protein. Acts in the lower portion of the small intestine. EPITHELIAL Binds to receptors on the epithelial cell surface. Alters the cell membrane, disrupting ion transport, leading to loss of fluid & intracellular proteins. 30  Clostridium perfringens ❑ Degradative enzymes: Metabolically vigorous organism producing a variety of hydrolytic enzymes: e.g. proteases, DNases, protein catabolism ALSO hyaluronidase & collagenases. a structural molecule at the level of ECM and tissues collagen breakdown (humongous protein that is part of the ECM , key role) Liquefy tissue & promote the spread of infection. loses its rigidity Products resulting from degradation serve as fermentation substrates for the organism rapid metabolism. bacterial metabolism 31  Clostridium perfringens ❑ Clinical significance: i. Myonecrosis (gas gangrene) ii. Acute food poisoning (see chapter 15) iii. Anaerobic cellulitis 32  Clostridium perfringens infection and intoxication ❑ Myonecrosis (gas gangrene): exposure to  Spores germinate in open wounds (e.g. those caused by GI tract surgery, burns, puncture entery way wounds & war wounds).  Production of cytotoxic factors. t the site of injury, all3 will be produced cells dying,...  Fermentation of organic compounds in host tissues  formation of gas bubbles. CO2 at the site of injury  Disease progresses: increased capillary permeability  exotoxins carried by the circulation from the damaged tissues to other organs  systemic effects (e.g. shock, renal failure & intravascular hemolysis).  Untreated myonecrosis is fatal. 33  Clostridium perfringens infection ❑ Clinical significance: Anaerobic cellulitis:  A clostridial infection of connective tissue. not as common as gas gangrene  Bacterial growth spreads rapidly along fascial planes. 34  Clostridium perfringens swab or scrape ❑ Laboratory identification: ❖ When cultured anaerobically on blood agar, it grows rapidly, producing colonies with a unique double zone of -hemolysis. complete ❖ With Gram stain, specimens from diseased tissue show vegetative clostridial forms (large, Gram+ rods), accompanied by other bacteria & cellular debris. 35 Pasteurella Common characteristics Shape Pleomorphic changes shapes Motility Non-motile Gram staining (-) Oxygen requirement Facultative anaerobes Oxidase test (+) Culture media Agar with heme or cytochromes Important member Pasteurella multocida 36  Pasteurella multocida ❑ Properties: ✓ Common cause of infection following bites or scratches caused by dogs & (especially) cats. ✓ Can cause disease or asymptomatic infections. 37  Pasteurella multocida ❑ Clinical significance: localized at site 1. Animal bite or scratch  soft tissue infections (majority of infections in humans).  Typical clinical manifestation: a rapidly developing cellulitis at the site of injury.  The infection is potentially dangerous & can cause a chronic local infection of deep tissues & osteomyelitis. we might reach bones and muscles 2. Nasopharyngeal colonization of the patient  infection (smaller fraction of infections). respiratory It responds well to several antimicrobials, with penicillin being drug of choice. 38  Pasteurella multocida ❑ Laboratory identification: ❖ Culture on blood agar showing small, translucent non-hemolytic colonies. gamma hemolysis ❖ Blood smear shows bipolar staining. extremities are stained and the middle is not history (cellulitis) 39 Propionibacteria ACNE Common characteristics Shape Rod-shaped or branched Motility Non-motile Gram staining (+) Oxygen requirement Anaerobe Catalase test (+) Culture media Blood agar Important member Propionibacterium acnes 40 Propionibacterium acnes feed on fatty acids produced by sebum (sebaceous glands) ❑ Properties: ✓ Lives in the sebaceous glands of the skin. ✓ Causes adolescent acne. ✓ May also infect patients who have intrusive medical devices. ✓ Antimicrobial drugs are more effective than topical agents in the treatment of acne. 41  Propionibacterium acnes ❑ Clinical significance: active bacterial growth (and replication) feeding on sebum buildup of sebum sebaceous gland still working and producing sebum growing bacteria (formation of pus) abnormal keratinization bacteria blocks the exit of sebum 42 Propionibacterium acnes ❑ Laboratory identification: ❖ Rods of diphtheroid like morphology. amplify and detect genetic material ❖ Quantitative real-time polymerase chain reaction. 43 Herpesviruses Common characteristics Genome dsDNA Envelope + Initiated by a number of virus-coded enzymes & transcription Lytic state factors Latent state Follows primary infection, to be reactivated at a later time Epstein-Barr virus Herpes simplex virus Important members Human cytomegalovirus Human herpesvirus Varicella-zoster virus 44  Herpes simplex virus ❑ Structure: STI antigenic power Envelope: contains antigenic, species-specific glycoproteins. protein rich protein liquid important for virus (like transcription factor) Tegument: amorphous proteinaceous material, containing virus-encoded enzymes & transcription factors essential for initiation of the infectious cycle. 45  Herpes simplex virus ❑ Replication: lesions eczema (red and crusty) An infected person is a lifelong source for contagion. HSV 1 is very common (up to 90% of children in under developed countries are seropositive) droplets poor sanitary conditions the virus stays latent in the nerves viral load is low (but enough to be transmitted via body fluids) 46  Herpes simplex virus ❑ Laboratory identification: Cell tissue culture inoculated with a sample of vesicle scraping, fluid or genital swab shows gross cytopathic changes in several days. scrapes Immunofluorescence of skin scrapings HSV in cell culture: Note the ballooning of cells. 47  Varicella zoster virus inhale droplets full of viral particles go into respiratory tract ❑ Time course of varicella (chickenpox) in children: and then replicate in lymph nodes travel all the way to liver and spleen and then systemically in the blood upon reactivation painful rash called zona (Localized in a zone) zennar nar ❑ In adults, the disease shows a longer time course & is more severe. 48 Rubella virus Common characteristics Genome (+)-sense, non-segmented ssRNA Envelope + Capsid Icosahedral Infection Genomic RNAs serve as mRNAs & are infectious Genus Rubivirus 49  Rubella virus ❑ Replication: 50 Rubella virus flulike symptoms ❑ Pathogenesis: Only infects humans. Lives in the mucus of an infected person. Spreads from person to person through contact or from a cough or sneeze. Rash- direct contact Transmitted up to a week before the rash appears and 1-2 weeks after. 1 week before-during- 1-2 weeks after Also transmitted from an infected mother to her unborn child causing Congenital Rubella Syndrome (CRS). harmful for the unborn baby 51  Rubella virus ❑ Clinical significance:  Symptoms for postnatal Rubella virus include a rash spreading down from the face to the extremities & in some cases a runny nose, fever or joint pain.  It is possible for the virus to be asymptomatic.  CRS causes a number of birth defects which include but are not limited to prenatal cataracts, may zar2a deafness, low birth weight & mental retardation. still birth (fetus dies in utero) first trimester=most dangerous  Rubella virus only has a large risk of infection if the disease is contracted by the mother in the first trimester, after which birth defects are less likely. 52  Rubella virus ❑ Laboratory identification: demonstration of a rise in antibody titer. dilution serology- agglutination caught it when u were a kid or immunity 53 Paramyxoviruses Common characteristics Genome (-)-sense, non-segmented ssRNA Envelope + Form Spherical Human metapneumovirus Measles virus Important members Mumps virus cause raches Parainfluenza virus Respiratory syncytial virus 54  Paramyxoviruses ❑ F (fusion) protein allows virus to enter cells via a fusion process (rather than by receptor-mediated endocytosis). ❑ Replication: 55 Paramyxoviruses ❑ Pathogenesis: They cause a wide variety of well-known illnesses, such as measles, mumps & parainfluenza. Measles ranks among the most common childhood diseases. A vaccine for measles, mumps & rubella was developed in the early 1970s & is used in most industrialized nations. Still, measles is one of the most contagious diseases known, causing 30-40 million cases & 1-2 million deaths/year worldwide in unvaccinated populations. reapperances 56 Paramyxoviruses ❑ Laboratory identification: ❖ Measles virus: Demonstration of an increase in the titer of antiviral antibodies. ❖ Mumps virus: Virus may be recoverable from saliva, blood, CSF or urine & can be cultured. Serologic tests detect antiviral antibody in the blood. 57 Papovaviruses Common characteristics Genome dsDNA Envelope X Shape Icosahedral Induce both lytic infections & either benign or malignant Infection tumors, depending on infected cell type Important member Human Papillomavirus 58 Human papillomavirus ❑ Properties: ✓ Over 150 types are now recognized, based on ≠ in the DNA sequences. ✓ Transmission of infection requires direct contact with infected individuals or contaminated surfaces. ✓ Exhibits great tissue & cell specificity, infecting only surface epithelia of skin & mucous membranes. ✓ Most common sexually transmitted infection in the US: 79 million are infected with HPV, 14 million new infections each year. ✓ Major cause of cervical cancers in women. 59  Human papillomavirus ❑ Clinical significance: 60  Human papillomavirus ❑ Laboratory identification: ❖ Diagnosis of cutaneous warts generally involves no more than visual inspection. ❖ Typing of HPV is done either by immunoassays for viral antigens or PCR amplification. ❖ HPV cannot be cultured in the laboratory. 61 Parvoviruses Common characteristics Genome ssDNA Envelope X Shape Icosahedral 62 Parvoviruses ❑ Properties: ✓ The only human pathogens with ss-DNA. ✓ The smallest of the DNA viruses. ✓ Cause a fatal disease in puppies. 63  Parvoviruses ❑ Replication: 64  Parvoviruses ❑ Clinical significance: Erythema infectiosum  Childhood illness also called fifth disease.  Caused by the primary parvovirus B19.  Begins as a red rash on the cheeks & spreads to the arms, thighs, buttocks & trunk.  Sunlight aggravates it. UV EXPOSURE 65  Parvoviruses ❑ Laboratory identification: ❖ Detection of viral proteins by immunologic methods. 66 Candida albicans ❑ Properties: ✓ Yeast ✓ Part of the normal body flora (skin, mouth, vagina & intestines) ✓ Grows at the normal vaginal pH of 4.0 pH change causes it to overgrow(Opportunistic infection) ✓ Can also be introduced to the body (e.g. during sexual contact). STI 67  Candida albicans candida fibronectins on epithelial cells- secretes proteinases to degrade proteins paving the way for hyphae to develop until it binds to ECM, continue growing ❑ Pathogenesis: Overgrowth of candida (candidiasis) occurs when competing bacterial flora are eliminated (e.g. by antibacterial antibiotics). Surface receptors on the yeast bind to fibronectin covering the epithelial cell or to elements of the ECM when the epithelial surface is lost or when C. albicans has invaded beyond it. Invasion is associated with formation of hyphae & production of proteinases, which may digest tissue elements. 68 CLINICAL CASE STUDIES Who’s responsible for this infectious disease? 69  Case study #1 Clinical history: – Over the course of 1 week, a 6-year-old boy develops 0.5 to 1.0 cm pustules on his face. – During the next 2 days, some of the pustules break, forming shallow erosions covered by a honey-colored crust. – New lesions then form around the crust. – The boy's 40-year-old uncle develops similar lesions after visiting for 1 week during the child's illness. 70  Case study #1 Laboratory findings: Staphylococcus aureus Betta HEMOLYSIS (COMPLETE) 71 cluster together like grapes  Case study #1 What is the most likely infectious agent? Staphylococcus aureus 72  Case study #2 Clinical history: – A suspicious envelope arrived for sorting at rural post office. – The envelope was opened and found to contain white powder. – Approximately 2 days later, the postal worker who handled the letter developed cutaneous boils, which were and 1 to 5 cm in diameter with central necrosis and eschars. 73  Case study #2 Clinical history: – He and his wife also developed a mild nonproductive cough with fatigue, wheezing (difficulty breathing) myalgia for 72 hours, followed by severe dyspnea, diaphoresis and cyanosis. unnatural sweating hypoxia, blue (lips and fingers) – Temperature of 39.5°C, pulse 105/min respiration 25/min and blood pressure low 85/45 mm Hg. very low – Crackles were heard at the lung bases. ykharkhir sodor 60-100 (normal pulse) 74  Case study #2 Laboratory/Radiology findings: – A chest X ray shows a widened mediastinum and small pleural effusions – WBC count of 13,130 /mm 3 – Hemoglobin 13.7 g/dL, – Hematocrit 41.2% – MCV 91 um3 – Platelet count 244,000 /mm3 – Both died despite antibiotic therapy – Several cattle, horses, and sheep on the postal worker's farm also died. 75  Case study #2 What is the most likely infectious agent? Bacillus anthracis 76  Case study #3 Clinical history: – An 80-year-old man complains of a painful rash on his left forehead. – The rash is vesicular and only on that side. – He is being treated with chemotherapy for leukemia. immunocompromised – Smear of material from the base of the vesicle reveals multinucleated giant cells with intranuclear inclusions. new baby viruses 77  Case study #3 What is the most likely infectious agent? Herpes Simplex Virus 78  Case study #4 Clinical history: – A 25-year-old woman has a painful, inflamed swollen hand. – She was bitten by a cat about 8 hours ago. Laboratory findings: – small Gram-negative rods in the exudate from lesion. 79  Case study #4 What is the most likely infectious agent? Pasteurella multocida 80  Case study #5 Clinical history: – An 8 year old girl has a pruritic rash on her chest. – Lesions are round or oval with an inflamed border and central clearing. – The lesions contain both papules and vesicles. Laboratory findings: – Hyphae in KOH prep of scrapings from the lesion. 81  Case study #5 What is the most likely infectious agent? Candida albicans 82  Case study #6 Clinical history: – An infant was brought to the ER with a rash. – Upon further examination, Koplik spots were detected. – The appearance of these spots was preceded by Fever, malaise, loss of apetite. – It was Followed by: conjunctivitis, coryza (inflammation of the mucous membrane in the nose), and cough (CCC). 83  Case study #6 What is the most likely infectious agent? Measles 84 FYI 85  Case study #7 Clinical history: – A 6-year-old girl presents with fever. Her mother tells you it started with fever and one vesicle on the thumb. 3 days later she looks like this: 86  Case study #7 What is the most likely infectious agent? Varicella Zoster Virus 87  Case study #8 Clinical history: – A young boy presents with “slapped cheeks rash”. – This is known as Erythema infectiosum or the fifth disease. Clinical history: – Immunological assays to detect viral proteins. 88  Case study #8 What is the most likely infectious agent? Parvovirus B19 89