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Epidermis 2
- Mucous memb.
- a. wet, not as tough as skin
- b. often low pH
- c. Normal flora
- d. macrophages, IgA
- e. mucous
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Staphylococcus aureus and other staph species
- a. Gm+ cocci in clusters
- b. facultative metabolism
- c. colonies 2-3mm. opaque with non-water soluble golden pigment +/- hemolysis
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Staphylococcus aureus #2
- d. vir and inv factors numerous (examples
- 1. coagulase (clots fibrinogen)
- 2. enterotoxins (food poisoning)
- 3. hyaluronidase (breaks down extracellular matrix)
- 4. cytotoxins (kill WBC's)
- 5. exfoliative toxins (skin peeling)
- 6. others
- 7. and other staph species are normal flora of skin, GI tract, oropharynges and urogenital tract
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Note: the virulence of a particual specimen and disease it causes depend on which vir factors the strain possesses
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Staphylococcus aureus and other staph
A. Wound infections
B. in-dwelling catheter infection
- A. Wound infection
- 1. autoinoculation or from fomites or hands
- 2. Coagulase + or - staph
- 3. can be MDR staph (eg. MRSA)
- 4. may require aggressive antibiotic treatment
- 5. can cause systemia
- B. in-dwelling catheter infection
- 1. catheters allow constant contact tof skin to open tissues leading to infection
- 2. coagulase - staph, skin normal flora
- 3. often causes low grade bacteremia
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Staph continued
Diseases
- furunucles: infections which start in hair follicle (rare cause of systemia)
- carbuncle: infection is larger, deeper and more serious (must drain and treat with antibiotic)
- pustules: a small lesion filled with pus (usually self-lmiting with drainage)
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Staph continued
Staph skin diseases of newborn or children
- 1. Scalded skin syndrome
- a. neonates
- b. staph stain with exfoliative toxin
- c. erythema that starts in mouth and covers body in 2 days
- d. top layer of skin peels
- e. neonate recovers in about 2wks when IR kicks in
- f. rare secondary systemia can kill in 36 hrs.
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Staph cont
Staph skin diseases of newborn cont
- 2. Impetigo (children, esp. boys)
- a. staph strain with hyaluronidase vir. factor
- b. superficial, rapidly spreading, contagious skin lesions, esp. of face.
- c. heals without scarring
- d. neonatal version: bullous impetigo
- e. also Streptococcus pyogenes
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Staph cont
toxic shock syndrome
- 1. TSST-1 toxin producing strains of S. aureus
- 2. systemia or from super absorbent tampons (no longer on the market)
- 3. entire body desquamation
- 4. rapidly fatal systemic shock if not treated
- Staph. aureus an also cause endocarditis, systemia and food poisoning (later)
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Staph cont
3. Sources of infection
- a. autoinoculation from skin, GI or nasopharyngeal normal flora
- b. fomites, droplet nuclei and hands cause many nosocomial infections
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Staph cont
4. Treatment
- a. Multiple drug resistance (MDR) is common (due to bacteriophage transduction?)
- b. Methicillin resistant S. aureus (MRSA) now common in hospital environment and becoming common outside hospital.
- c. Vancomycin resistant S. aureus (VRSA) has now been detected
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Streptococcal skin infections
1. intro
- a. Strept pyogenes and other streptococci cause a variety of diseases.
- d. S. pyogenes can be carried transiently, in low numbers, with the normal flora in the nasopharynges
- e. disease spread is most commonly from transient carriers in the form of droplet nuclei, hands, fomites
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Strept skin infections
2. skin diseases
A. pyoderma
- 1. introduction of mo into broken skin
- 2. pustule develops, usually self-limiting
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Streptococcal skin infections
2. skin diseases
b. erysipelas
- 1. secondary to strept throat or pyoderma
- 2. skin raised, inflamed, painful, low grade symptoms of systemia
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Strep skin infections
c. cellulitis
- 1. secondary to streopt throat or pyoderma
- 2. a deeper infection than erysipelas
- 3. skin not raised,but is inflamed, painful, symptoms of systemia
- 4. many organisms can cause cellulitis
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Strep skin infections
d. impetigo
e. necrotizing fasciitis (flesh eating virus)
- 1. introduced through skin break
- 2. initially like cellulites, spreads to muscle and fat and degrades theses tissues with enzymes (vir factors)
- 2. rapidly fatal systemia develps w/o aggressive treatment
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Other skin diseases that can also be caused by fungi and viruses
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Burn infections
- many mo's can cause burn infections
- 1. coliforms (Gm-, facultative rods from GI)
- 2. Staph and Strep
- 3. Most common and dangerous: Pseudomonas aeruginosa
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Pseudomonas aeruginosa characteristics
- 1. Gm-, aerobic rod
- 2. found in water, soil, sometimes as GI normal flora
- 3. extremely antibiotic and disinfectant resistant
- 4. an opportunist but once it starts, a very serious infection ensues
- 5. often makes blue and green pigments
- 6. makes a wide variety of vir and inv factors that are very good at breaking down tissue and spreading the infection
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course of Pseudomonas burn infection
- 1. autoinoculation or introduction from environment (soil, water, disinfectants, flowers, air, soapy water, hands)
- 2. mo divides rapidly in weepage from burns
- 3. hydrolytic enzymes allow easy tissue invasion
- 4. fatal systemia, pneumonia follows (2-4wks)
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Treatment of Pseudomonas burn infection
- 1. strict isolation/aseptic procedures to prevent infection
- 2. antibiotic treatment difficult (combination therapy)
e. Pseudomonas is also noted for Cystic Fibrosis pneumonia.
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Area of eye that can become infected
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protection of the eyes
- 1. cornea/sclera are tough walled
- 2. tears wash away mo's
- 3. tears contain lysozyme
- 4. mucous entraps mo's
- 5 IgA is likely present
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Eye infection
Diseases
1. Chlamydia trachomatis
- a. Obligate intracellular bacteria
- b. causes a conjuctivitis called Trachoma
- c spread by poor sanitation, flies, and the rubbing of eyes
- d. highly contagious
- e. lack of treatment leads to abraion of cornea by eyelid/lashes that then causes blindness (common cause of blindnes in 3rd world)
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Eye infection diseases
2. Neisseria gonorrhoeae
- a. Gm- intracellular bacteria
- b. causes a disease in neonates called gonococcal conjuctivitis
- c. infection occurs during vaginal birth in a mother with gonorrhea
- d. lack of treatment leads to blindness
- e. neonates are given prophylactic antibiotic eye drops at birth to prevent
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Eye infections
3. Haemophilus influenzae biotype aegyptius
- a. Gm- small rods
- b. causes a disease called contact conjuctivitis or pinkeye
- c. spread by poor sanitation, flies and the rubbing of eyes
- d. highly contagious
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Pseudomonas spp infections
- infections caused by overly long term use of soft contact lenses
- several different viral conjunctivitis'
- protozoal eye infection caused by ancanthamoeba keratits
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Bacterial diseases of the Circulation and Lymphatic systems
Intro
- Closed system
- 1. oxygenates tissues
- 2. eliminate CO2
- 3. remove wasts from tissues and deliver them to spleen and kidneys
- 4. provide mobility to immune system, hormones and other chemical signals
- 5. maintain temp homeostasis
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Lymphatic system
- (open system)
- 1. pick up lymph from interstitial spaces
- 2. clear lymph before it is returned to circ.
- 3. system has no pump
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Protection of the circ and lymph systems
- 1. sterile
- 2. 1st, 2nd and 3rd levels of immunity
- 3. filtration of lymph by lymph nodes and blood by spleen
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Cardiac Diseases
1. Subacute bacterial endocarditis (SBE)
- a. slow onset of symptoms: fever, weakness,heart murmur
- b. caused by oral streptococci and others from infections throughout the body (e.g. tooth infection, tonsillectomy, body piercings, gynecological exam, teeth cleaning, flossing or even brushing teeth)
- c. often patient has a previous lesions of the heart which provide tissue for the bacteria to entangle in (e.g. causes include scarlet fever, syphilis, previous SBE or heart deformities)
- d. slowly fatal if not treated (long term antibiotics)
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Diagnosis of (SBE)
- 1. imaging of mass in hearat
- 2. blood culture
- a. draw blood into broth filled bottle, incubate
- b. requires many bottles because: unknown mo metabolic requirements (O2, nutrients), interfereing chems, antibiotics, few mo's in blood, etc
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Acute bacterial endocarditis
- a. initial symptosm: fever, chills, weakness (i.e. nonspecific type symptoms)
- b. rapid onset, later symptoms: decreased cardiac output and microcoaagulation of peripheral blood (rapidly fatal)
- c. usually caused by S. aureus
- d. parenteral drug users have a milder form of this disease that is more like SBE
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Septicemia (AKA sepsis, bacteremia)
- 1. bacteria growing in blood stream
- 2. often septicemia is secondary to other problems: patient is immuno-compromised, pneumonia, TB, burn patient, syphilis, invasive GI bacteria, gangrene, cellulitis
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Septiciemia cont
symptosm
fever and malaise, then decrease in cardiac output, decrease in bp, decrease in temp, acute systematic inflammation (septic shock) and deat
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Septicemia cont
bacterial products in the blood stream produces what?
- a toxemia leading to systemic shock
- 1. lipid A of LPS of Gm- cell membrane are present in Gm- systemia
- 2. treatment with antibiotics leads to release of more endotoxins, often resulting in systemic shock and death
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Septicemia from zoonotic sources
- a. bites can introduce mo's directly into the blood stream or tissues
- b. mo's can be pathogens carried by the animal (e.g. rabies, malaria, plague)
- c. mo's can be part of oral normal flora which can also be very dangerous (e.g. human)
- d. bites often cause bacterial systemias
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Septicemia from zoonotic sources cont.
Plague
- a. Yersinia pestis
- 1. short, Gm- rod
- 2. facultative
- b. Main vir factor: antiphagocytic capsule
- c. transmission: flea bite or droplet nuclei from pneumonia
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Septicemia from zoonotic sources cont.
Plague cont
course of disease
- 1. flea bites infected rodent (usually rat or ground squirrel)
- 2. bacilli multiply in gut of flea
- 3. gut becomes blocked
- 4. flea bites host bug gut is blocked resulting in regurgitated blood back into the bite
- 5. mo's carried to regional lymph nodes of of new host
- 6. mo's not phagocytized and multiply in node
- 7. infected node becomes pus filled, swollen: bubo
- 8. systemia follows with generalized symptoms plus the buboes
- 9. systemic shock precedes death (nearly 100% fatal at this stage)
- 10. takes 3-5 days
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Plague cont
treatment
what was the vector called in the US?
History in Europe
treatment: prompt antibiotics (before the systemia is too severe)
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Vector was from ground squirrel
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pneumonic plague and the black death in Europe in the 14th centrury
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Septicemia from zoonotic sources
Tularemia
- a. Franciella tularensis
- 1. Gm- coccobacillus
- 2. aerobic, obligate intracellular
- 3. vir: antiphagocytic capsule
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Tularemia cont
transmission
mo's is found in a variety fo rodents, birds and ticks
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Tularemia cont
human disease is of 3 varieties, depending on mode of infection. What are the varieties?
- a. typhoid-like tularemia from eating undercooked infected rabbits
- b. pneumonic tularemia: inhaled blood spray or other infectious aerosol (bio-weapon?): like pneumonic plague, high mortality
- c. ulcerative: cut or infected tick bite (most common) will lead to a local lesion that can spread to a regional lymph node and then a systemia
- Treatment: prompt, prolonged antibiotics: Russian-made vaccine
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Septicemia from zoonotic sources cont
Lyme disease
- a. 1st detected in the city of Lyme, Ct. in 1975 and thought to be arthritis
- b. Borrelia bergdorferi
- 1. spirochete
- 2. spiral shape
- 3. must be grown in animal host
- Outdoorsy people most likely to get Lyme disiease during spring and summer time
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Septicemia from zoonotic sources cont
Course of Lyme disease (3 stages)
- 1. target-like rash at site fo tick-bite, which then fades (75% of patients have this)
- 2. 2-3 weeks after rash starts to fade, a systemia leads to flu like symptoms, irregular heart beat, neurological symptoms: facial paralysis, encephalitis (antibiotics effective up to this point)
- 3. moths to years later, symptoms caused by hypersensitivity to mo: severe arthritis
- Treatment: long term antibiotics
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Septicemia from zoonotic sources cont.
Rickettsial diseases
- Rickettsia spp.
- 1. very small Gm- rods
- 2. aerobes
- 3. obligate intracellular parasites
- Vectors: blood sucking insects like ticks, body lice, chiggers
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Rickettsial disease cont
2 groups
Spotted fever group
- Spotted fever group is represented in the Western Hemisphere by Rocky Mtn spotted fever.
- 1. Rickettsia rickettsii
- 2. tick-borne
- Course of disease
- a. 2-14 days after tick bite: high fever, chills, headache
- b. 2-3 days later: petichial rash that spreads from extremities to thorax (not always present), mo lives in endothelial cells.
- c. late stage includes GI symptoms, encephalitis, renal failure, resp. failure, diffuse intravasc. coagulation and 20-40$ mortality.
- Avoidance/treatment:avoid being bitten by ticks, treat with antibiotics before late stage symptoms (difficult to Dx without the rash)
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Rickettsial disease
2 groups
Typhus group
- Rickettsia prowazekii
- 1. endemic or louse-borne typhus
- 2. vector is body louse
- a. problem of crowded areas of poor personal hygiene, e.g. refugee camps, armies in the field
- 3. Siege of Granada in 1490, 5-6x due to disease
- 4. course of disease: abrupt high fever and stupor, headache, 40% of cases report rash, cardiac and CNS dysfunction with high mortality
- Avoidance/treatment: avoid being bitten by lice (field showers), vaccine is available, treat with antibiotics before late stage symptoms.
- (isolated cases difficult to Dx w/o the rash)
- In US, cases are mostly from fleas from flying squirrels
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Disease of Circulation cont
Gas gangrene
- 1. mo's: Clostridium perfringens and other Clostridial spp.
- a. Gm+, large sporing rods, anaerobic
- b. produces a wide variety fo vir and inv factors, esp. hydrolytic enzymes that enlarge the wound and spread the infection
- c. spores commonly found in soil and GI tract
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Gas gangrene
course of the disease
- a. deep wound & introduction of feces or soil provides inoculum (e.g. military type wound)
- b. spores germinate in anaerobic environment
- c. cells produce copious amounts of hydrolytic enzymes: destroys circulation, tissue death, deepens the wound, spreads the infection.
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Gas gangrene
Symptoms (in 6-72hrs)
- Swelling
- inflammation
- pain, fever
- foul-smelling gas in wound
- tissue necrosis
- then... systemia, with aggressive behavior, delirium and death
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Gas gangrene cont
Treatment (100% fatal if not treated)
- a. prompt cleaning of wounds
- b. surgery to remove necrotic tissue (debridement)
- c. amputation
- d. hyperbaric chamber (kills Clostridia by forcing O2 into the wound)
- Note: gangrene is a common consequence of diabetes, as progresive loss of circulation leads to tissue death in the toes, then legs.
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Diseases of circulation cont
other diseases of circulation
- a. bacterial : anthrax
- b. viral: small pox, Burkett's Lymphoma and EB virus, mononuecleosis, CMV, hemorrhagic fevers
- c. protozoal: malaria, Chagas' disease, toxoplasmosis, Leishmaniasis
- d. helminthic: Schistosomiasis, swimmer's itch
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Bacterial diseases of the Upper Respiratory tract.
Functions of URT
- eating
- taste
- smell
- hearing
- air processing and conduction
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Protection of URT
- 1. mucous to entrap mo's
- 2. sneezing to dislodge
- 3. macrophages to engulf
- 4. IgA
- 5. normal flora
- 6. inflammation
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URT disease
Sgreptococcus
- 1. Gm+ cocci in chains
- 2. facultative, but catalase - (acts like an aerotolerant anaerobe)
- 3. fastidious, nasopharyngeal species isolated on Blood agar
- 4. many species, classification based on surface Ag's
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Streptecoccus
classification basis
- 1. proposed by Rebecca Lancefield
- 2. different strep species were grouped by common surface Ag's
- 3. used agglutination tests,
- 4. groups are designated by letters
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Streptococcus
Classification
- Group A: Streptococcus pyogenes
- Group B: Strep agalactiae
- URT normal flora
- stubborn nosocomial systemia, pneumonia in comprimised
- serious systemia, meningitis acquired from mother during birth in neonates
- historically was a common cause of puerperal fever (childbirth fever) (Oliver Wendel Homes and I. Semmelweis and antisepsis)
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Streptococcus classification cont
Group C & D
- Group C: Streptococcus angiosus complex
- Stubborn opportunists
- Group D?: many spp.
- URT or GI normal flora
- Ocasional opportunists
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Viridans streptococci
- Variety of oral, GI and GU normal flora streptococci
- viridans = green, refers to appearance on blood agar
- occasional opportunists
- notables: S. mitis, S. salivarius, S. pnueumoniae
- lack surface Lancefield Ag's
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Isolation of streptococci from oral cavity
- 1. are fastidious, usually grown on blood agar +/- increased CO2 (differential medium)
- 2. Hemolysis of blood cells indicate which hemolysins the isolate makes:
- Group A: β-hemolysin, pathogen
- Group B: mostly β-hemolysin, likely pathogen
- Group C: mostly β-hemolysin, likely pathogen
- most others: α-hemolysin, non-pathogen or opportunist, except for S. pneumoniae
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Isolation of streptococci from oral cavity (cont
Hemolysis of blood cells: a quick screen for pathogens in the URT
Group A, B and C: β-hemolysin, possible pathogen
- most other strepts: α- hemolysin, non-pathogen except for S. pneumoniae
- most other strepts: have α-hemolysin & are non-pathogenic (except for S. pneumoniae which has an obvious capsule)
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vir and inv factors (S. pyogenes)
- 1) β-hemolysin
- 2) Streptolysin: cytotoxic
- 3) M Ag (fimbrae): antiphagocytic
- 4) others
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Streptococcal pharyngitis (strep throat)
- 1) caused by Group A only
- 2) symptoms (throat epithelium, esp. tonsils) •swollen •+patches of pus on tonsils •red •pain •inflammation •fever, malaise
- 3) transmission: droplet nuclei, fomites
- 4) treatment: prompt antibiotics
- if strep throat goes untreated, 2° effects or infections can occur
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possible consequences of untreated strep throat
1. Scarlet fever
- a) strain has a lysogenic phage that codes for an erythrogenic exotoxin
- b) rash of chest and extremities, later desquamation
- c) yellow exudate of tongue, later desquamation
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possible consequences of untreated strep throat (cont)
- 2) otitis media (middle ear infection)
- 3) Rheumatic fever: cross reacting Ab’s attack mitral valve of heart and joints
- 4) Glomerulonephritis: inflammation of the kidneys with edema and hypertension
- c. other possible diseases of S. pyogenes: impetigo, necrotizing fasciitis, cellulitis, pyoderma, erysipelas, systemia, TSS, pneumonia
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Diphtheria
- 1) Corynebacterium diphtheriae
- a) Gm+ pleomorphic rod
- b) palisades arrangement
- c) + metachromatic granules (PHB)
- 2) course of the disease
- a) transmission: airborne, droplet nuclei, fomites
- b) sore throat, fever, malaise
- c) then diphtheritic membrane forms, a serum clot, which is Dx
- d) Toxin: phage-borne powerful exotoxin
- e) toxin leads to heart and kidney failure, trouble swallowing, death
- 3) treatment: DPT vaccine contains diph. toxoid
- a) very effective
- b) diph. well controlled in US
- 4) a cutaneous form exists, mostly in the homeless
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