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81 Cards in this Set
- Front
- Back
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staphylcocccal
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Common inhabitant of the skin and mucous membranes
Spherical cells arranged in irregular clusters Gram-positive Lack spores and flagella May have capsules 31 species |
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Staphlococcus aureus
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Grows in large, round, opaque colonies
Optimum temperature of 37oC Facultative anaerobe Withstands high salt, extremes in pH, and high temperatures Produces many virulence factors |
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Virulence factors of S. aureus
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Enzymes:
Coagulase – coagulates plasma and blood; produced by 97% of human isolates; diagnostic Hyaluronidase – digests connective tissue Staphylokinase – digests blood clots DNase – digests DNA Lipases – digest oils; enhances colonization on skin Penicillinase – inactivates penicillin |
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toxins: Virulence factors of S. aureus
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Toxins:
Hemolysins (α, β, γ, δ) – lyse red blood cells Leukocidin – lyses neutrophils and macrophages Enterotoxin – induce gastrointestinal distress Exfoliative toxin – separates the epidermis from the dermis Toxic shock syndrome toxin (TSST) – induces fever, vomiting, shock, systemic organ damage |
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Folliculitis (s.aureus)
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superficial inflammation of hair follicle; usually resolved with no complications but can progress
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Furuncle (s.aureus)
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boil; inflammation of hair follicle or sebaceous gland progresses into abscess or pustule
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Carbuncle (s.aureus)
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– larger and deeper lesion created by aggregation and interconnection of a cluster of furuncles
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Impetigo (S.aureus)
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bubble-like swellings that can break and peel away; most common in newborns
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Osteomyelitis (systemic)(S.aureus)
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infection is established in the metaphysis; abscess forms
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Toxigenic disease
(S.aureus) |
Food intoxication – ingestion of heat stable enterotoxins; gastrointestinal distress
Staphylococcal scalded skin syndrome – toxin induces bright red flush, blisters, then desquamation of the epidermis Toxic shock syndrome – toxemia leading to shock and organ failure |
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Identification of Staphylococcus
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Frequently isolated from pus, tissue exudates, sputum, urine, and blood
Cultivation, catalase, biochemical testing, coagulase positive bubbles (S.aureus) |
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MRSA – methicillin-resistant S. aureus
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95% have penicillinase and are resistant to penicillin and ampicillin
MRSA – methicillin-resistant S. aureus – carry multiple resistance Some strains have resistance to all major drug groups except vancomycin HA-MRSA (hospital-acquired MRSA) account for 80% of Staph. infections |
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Treatment and Prevention of Staphylococcal Infections
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Treatments:
Abscesses have to be surgically perforated Systemic infections require intensive lengthy Preventions: Universal precautions by healthcare providers to prevent nosocomial infections Hygiene and cleansing |
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Streptococcal
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Gram-positive spherical/ovoid cocci arranged in long chains; commonly in pairs
Non-spore-forming, nonmotile Can form capsules and slime layers Facultative anaerobes Do not form catalase, but have a peroxidase system Most parasitic forms are fastidious and require enriched media Small, nonpigmented colonies Sensitive to drying, heat, and disinfectants |
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b-hemolytic Streptococci
Streptococcus pyogenes |
Most serious streptococcal pathogen
Strict parasite Inhabits throat, nasopharynx, occasionally skin Virulence Factors: Hyaluronic acid capsule, Streptolysins, Erythrogenic toxin (pyrogenic – cause fever and rash |
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Streptococcus pyogenes
transmission |
Transmission – contact, droplets, food, fomites
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Necrotizing Fasciitis
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In rare cases, skin infections can lead to necrotizing fasciitis (flesh-eating disease)
Infecting Streptococci release exotoxins that poison epidermal and dermal tissues Flesh dies and sloughs off, allowing the Streptococci to invade deeper tissues More dangerous infections are mixed with anaerobic bacteria or involve septicemia |
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Streptococcal pharyngitis
S. Pyogenes Diseases |
strep throat infection
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Scarlet fever
S. Pyogenes Diseases |
strain of S. pyogenes carrying a prophage that codes for erythrogenic toxin; can lead to sequelae
(systemic infection) |
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Rheumatic fever
Long-Term Complications of S. Pyogenes |
follows overt or subclinical pharyngitis in children or scarlet fever; can lead to carditis with extensive valve damage possible, arthritis, chorea, fever
Can last 3-6 months; effects not apparent until adulthood |
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Treatment and Prevention
S. Pyogenes Diseases |
Treated with penicillin or penicillin derivatives
Long-term penicillin prophylaxis for people with a history of rheumatic fever or recurrent strep throat No treatment for rheumatic fever and acute glomerulonephritis once developed, must treat preceding infections to avoid these conditions |
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α-Hemolytic Streptococci: Viridans Group
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Once invaded these types can cause
Bacteremia, meningitis, abdominal infection, tooth abscesses Persons with preexisting heart disease are at high risk; S. mutans produce slime layers that adhere to teeth, basis for plaque Persons with preexisting heart conditions should receive prophylactic antibiotics before surgery or dental procedures Colonization of heart by forming biofilms |
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subacute endocarditis
Streptococci: Viridans Group |
Blood-borne bacteria settle and grow on heart lining or valves
People with heart disease at higher risk. Colonization of heart by forming thick biofilms called vegetations Diagnosis: Blood cultures Treatment: Long term administration of penicillin-G treatments |
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Streptococcus pneumoniae
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Causes 60-70% of all bacterial pneumonias
Culture requires blood or chocolate agar & growth improved by 5-10% CO2 All pathogenic strains form large capsules – major virulence factor Causes pneumonia and otitis media (ear infections) |
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Pneumonia:
Streptococcus pneumoniae |
Occurs when cells are aspirated into lungs of susceptible individuals
Pneumococci multiply and induce an overwhelming inflammatory response |
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Otitis media:
Streptococcus pneumoniae |
Occurs when cells gain access to middle ear by way of eustachian tube
Results in meningitis in some cases (most common cause of adult meningitis and a common cause of meningitis in children) Meninigitis: Severe Inflammation of the lining of the Brain and spinal cord. |
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diagnosis, treatment, and prevention of Streptococcus pneumoniae
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Gram stain of specimen – presumptive identification
Quellung test or capsular swelling reaction Traditionally treated with penicillin G or V Increased drug resistance Two vaccines available for high risk individuals: Capsular antigen vaccine for older adults and other high risk individuals – effective 5 years Conjugate vaccine for children 2 to 23 months Conjugate vaccine: vaccine made of pneumococcal Ags associated with diptheria Ags |
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Neisserial Diseases
genus neisseria |
Gram-negative, bean-shaped, diplococci
None develop flagella or spores Capsules on pathogens Pili Strict parasites, do not survive long outside of the host Aerobic or microaerophilic Produce catalase and cytochrome oxidase Pathogenic species require enriched complex media |
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Neisseria gonorrhoeae: Gonorrhea
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Males – urethritis, yellowish discharge, scarring, and infertility
10% of males are asymptomatic Females – vaginitis, urethritis, salpingitis (PID) mixed anaerobic abdominal infection, common cause of sterility and ectopic tubal pregnancies 50% of females are asymptomatic |
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Diagnosis and Treatment of gonorrhea
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Gram stain – Gram-negative intracellular (neutrophils) diplococci from urethral, vaginal, cervical, or eye exudate – presumptive identification
20-30% of new cases are penicillinase-producing PPNG or tetracycline resistant TRNG Combined therapies indicated Recurrent infections can occur Reportable infectious disease |
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Neisseria meningitidis: The Meningococcus
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Virulence factors:
Capsule Adhesive fimbriae IgA protease Endotoxin: 12 strains Prevalent cause of meningitis; sporadic or epidemic Human reservoir – nasopharynx; 3-30% of adult population; higher in institutional settings High risk individuals are those living in close quarters, children 6 months-3 years, children and young adults 10-20 years Disease begins when bacteria enter bloodstream, cross the blood-brain barrier, permeate the meninges, and grow in the cerebrospinal fluid Very rapid onset; neurological symptoms; endotoxin causes hemorrhage and shock; can be fatal |
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diagnosis, treatment, and prevention, meningococcus meningitis
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Diagnosis:
Gram stain CSF, blood, or nasopharyngeal sample Culture for differentiation Treatment and Prevention: Treated with IV penicillin G, cephalosporin Prophylactic treatment of family members, medical personnel, or children in close contact with patient Primary vaccine contains specific purified capsular antigens |
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Tetanus:Clostridium tetani
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Common resident of soil and GI tracts of animals
Causes tetanus or lockjaw, a neuromuscular disease Most commonly among geriatric patients and IV drug abusers; neonates in developing countries Spores usually enter through accidental puncture wounds, burns, umbilical stumps, frostbite, and crushed body parts Anaerobic environment is required for vegetative cells to grow and release toxin Tetanospasmin – neurotoxin causes paralysis by binding to motor nerve endings; blocking the release of neurotransmitter for muscular contraction inhibition; muscles contract uncontrollably Death most often due to paralysis of respiratory muscles |
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treatment and prevention:
Tetanus:Clostridium tetani |
Treatment aimed at deterring degree of toxemia and infection and maintaining homeostasis
Antitoxin therapy with human tetanus immune globulin; inactivates circulating toxin but does not counteract that which is already bound Control infection with penicillin or tetracycline; and muscle relaxants Vaccine available; booster needed every 10 years |
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Botulism; Food Poisoning
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intoxication associated with inadequate food preservation
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botulism: Clostridium botulinum
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spore-forming anaerobe; commonly inhabits soil and water
Botulin toxin is carried to neuromuscular junctions and blocks the release of acetylcholine, necessary for muscle contraction to occur Double or blurred vision, difficulty swallowing, neuromuscular symptoms |
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treatment and prevention of
botulism: Clostridium botulinum |
Determine presence of toxin in food, intestinal contents or feces
Administer antitoxin; cardiac and respiratory support Infectious botulism treated with penicillin Practice proper methods of preserving and handling canned foods; addition of preservatives |
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Tuberculosis (TB): Mycobacterium tuberculosis
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Virulence factors – contain complex waxes and cord factor that prevent destruction by lysosomes or macrophages
Gram-positive irregular bacilli Acid-fast staining Strict aerobes Produce catalase Possess mycolic acids and a unique type of peptidoglycan Do not form capsules, flagella, or spores Grow slowly |
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epidemiology: TB
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Predisposing factors include: inadequate nutrition, debilitation of the immune system, poor access to medical care, lung damage, and genetics
Estimate 1/3rd of world population and 15 million in U.S. carry tubercle bacillus; highest rate in U.S. occurring in recent immigrants Bacillus very resistant; transmitted by airborne respiratory droplets |
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primary TB
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Infectious dose 10 cells
Phagocytosed by alveolar macrophages and multiply intracellularly After 3-4 weeks; Tubercle formed -- immune system attacks, forming tubercles, granulomas consisting of a central core containing bacilli surrounded by WBCs If center of tubercle breaks down into necrotic caseous lesions, they gradually heal by calcification |
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Secondary and Extrapulmonary TB
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Secondary:
If patient doesn’t recover from primary tuberculosis, reactivation of bacilli can occur Tubercles expand and drain into the bronchial tubes and upper respiratory tract Gradually the patient experiences more severe symptoms Violent coughing, greenish or bloody sputum, fever, anorexia, weight loss, fatigue Untreated, 60% mortality rate Extrapulmonary: During secondary TB, bacilli disseminate to regional lymph nodes, kidneys, long bones, genital tract, brain, and meninges These complications are grave |
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diagnosis TB
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Mantoux test – local intradermal injection of purified protein derivative (PPD); look for red wheal to form in 48-72 hours – induration; established guidelines to indicate interpretation of result based on size of wheal and specific population factorsX-rays
X-rays Direct identification of acid-fast bacilli in specimen Cultural isolation and biochemical testin |
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treatment and prevention of TB
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6-24 months of at least 2 drugs from a list of 11
One pill regimen called Rifater (isoniazid, rifampin, pyrazinamide) Vaccine based on attenuated bacilli Calmet-Guerin strain of M. bovis used in other countries In the US it is reccommended: the vaccine should be considered for infants and children who do not test positive for TB but who are:Continually exposed to a patient with infectious TB of the lungs (and the child cannot be removed from this person)Exposed to a person with TB that is resistant to antituberculosis drugs |
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Pseudomonas:
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Small gram-negative rods with a single polar flagellum
Free living Primarily in soil, sea water, and fresh water; also colonize plants and animals Important decomposers and bioremediators Frequent contaminants in homes and clinical settings Use aerobic respiration; do not ferment carbohydrates Produce oxidase and catalase Many produce water soluble pigments |
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Pseudomonas aeruginosa
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Common inhabitant of soil and water
Intestinal resident in 10% normal people Resistant to soaps, dyes, quaternary ammonium disinfectants, drugs, drying Frequent contaminant of ventilators, IV solutions, anesthesia equipment Opportunistic pathogen |
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Pseudomonas aeruginosa: nosocomial infection,UTI, abscesses
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Common cause of nosocomial infections in hosts with burns, neoplastic disease, cystic fibrosis
Complications include pneumonia, UTI, abscesses, otitis, and corneal disease Endocarditis, meningitis, bronchopneumonia Grapelike odor and greenish-blue pigment (pyocyanin) Multidrug resistant Treated with third generation antibiotics Vaccine trials underway |
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Tularemia: Francisella tularensis
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Gram negative Rod
Causes tularemia, a zoonotic disease of mammals endemic to the northern hemisphere, particularly rabbits – AKA “Rabbit Fever” Transmitted by contact with infected animals, water and dust or bites by vectors |
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Tularemia:Francisella tularensis
signs and symptoms: |
ID: 10 – 50 bacteria; incubation period of 3 – 21 days
Infection usually occurs through inoculation of skin abrasion or eyes Signs and symptoms: Headache, backache, chills, malaise, and weakness Fever, ulcerative skin lesions, swollen lymph glands, conjunctivitis, sore throat, intestinal disruption, pulmonary involvement (severe) 10% death rate in systemic and pulmonic forms Intracellular persistence can lead to relapse |
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Tularemia: Treatments and Preventions
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Treated with Gentamicin or tetracycline
Attenuated vaccine being made Potential bioterrorism agent Because of such low ID and considered to be one of the most infectious bacteria |
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Pertussis: Bordetella pertussis
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Minute, encapsulated coccobacillus
Causes pertussis or whooping cough, a communicable childhood affliction Acute respiratory syndrome Often severe, life-threatening complications in babies Reservoir – apparently healthy carriers Transmission by direct contact or inhalation of aerosols Virulence factors Receptors that recognize and bind to ciliated respiratory epithelial cells Toxins that destroy and dislodge ciliated cells Loss of ciliary mechanism leads to buildup of mucus and blockage of the airways Vaccine – DTaP – acellular vaccine contains toxoid and other Ags |
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Enterobacteriaceae Family
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Large family of small, non-spore-forming gram-negative rods
Many members inhabit soil, water, decaying matter, and are common occupants of large bowel of animals including humans Facultative anaerobes, grow best in air All ferment glucose, reduce nitrates to nitrites, oxidase negative, and catalase positive Divided into coliforms (lactose fermenters) and non-coliforms (non-lactose fermenters) Enrichment, selective and differential media utilized for screening samples for pathogens |
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Escherichia coli:
coliforms (lactose fermenters) |
The Most Prevalent Enteric Bacillus
Most common aerobic and non-fastidious bacterium in gut 150 strains Some have developed virulence through plasmid transfer, others are opportunists |
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Enterotoxigenic E. coli
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causes severe diarrhea due to heat-labile toxin and heat-stable toxin – stimulate secretion and fluid loss; also has fimbriae
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Enteroinvasive E. coli
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causes inflammatory disease of the large intestine
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Enteropathogenic E. coli
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linked to wasting form infantile diarrhea
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Enterohemorrhagic E. coli,
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O157:H7 strain, causes hemorrhagic syndrome and kidney damage
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Escherichia coli
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Pathogenic strains frequent agents of infantile diarrhea – greatest cause of mortality among babies
Causes ~70% of traveler’s diarrhea Causes 50-80% UTI Coliform count – indicator of fecal contamination in water Often complicate surgery, endoscopy, tracheostomy, catheterization, dialysis and immunosuppressant therapy Usually effectively treated with antimicrobics (man-made antibiotics) and enterotoxin inactivation and rehydration in some instances |
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E. coli O157:H7
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ID = 100 cells
Infection can lead to intestinal hemorrhage Virulence associated with a cell wall receptor that allows cell to fuse to host cell, providing direct contact for toxin delivery Contains gene for shiga toxin from Shigella Heat-labile exotoxin that can injure nerve cells, nerves and the intestine Reservoir in intestine of cattle, allowing it to rather easily contaminate food chain Rapidly identified using Rainbow Agar: O157:H7 colonies appear black |
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Salmonella typhi: non-coliforms (non-lactose fermenters)
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Gram negative; true pathogens
Flagellated; survive outside the host Resistant to chemicals – bile and dyes Salmonella typhi – most serious pathogen of the genus; cause of typhoid fever; human host |
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Typhoid Fever
(salmonella typhi) |
Bacillus enters with ingestion of fecally contaminated food or water; occasionally spread by close personal contact
Asymptomatic carriers; some chronic carriers shed bacilli from gallbladder Bacilli adhere to small intestine, cause invasive diarrhea that leads to septicemia Treat with chloramphenicol or sulfatrimethoprim 2 vaccines for temporary protection |
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Plague: Yersinia pestis
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nonenteric
Tiny, gram-negative rod, unusual bipolar staining and capsules Virulence factors – capsular and envelope proteins protect against phagocytosis and foster intracellular growth Coagulase Endotoxin Murine toxin |
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Yersinia pestis
(plague how do u get) |
Humans develop plague through contact with wild animals (sylvatic plague) or domestic or semidomestic animals (urban plague) or infected humans
Found in 200 species of mammals – rodents, without causing disease Flea vectors – bacteria replicates in gut, coagulase causes blood clotting that blocks the esophagus; flea becomes ravenous ID 3-50 bacilli |
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Bubonic
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bacillus multiplies in flea bite, enters lymph, causes necrosis and swelling called a bubo in groin or axilla
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Septicemic
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progression to massive bacterial growth; virulence factors cause intravascular coagulation subcutaneous hemorrhage and purpura – black plague
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Pneumonic
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– infection localized to lungs, highly contagious; fatal without treatment
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Diagnosis, Treatment and Prevention of Plague
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Diagnosis depends on history, symptoms, and lab findings from aspiration of buboes
Treatment: streptomycin, tetracycline, or chloramphenicol Killed or attenuated vaccine available Prevention by quarantine and control of rodent population in human habitats |
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Haemophilus meningitis:
Haemophils influenza |
Tiny gram-negative pleomorphic rods
Fastidious, sensitive to drying, temperature extremes, and disinfectants None can grow on blood agar without special techniques – chocolate agar Require hemin, NAD, or NAD Can only grow within human cells agent of acute bacterial meningitis Also may cause; epiglottitis, otitis media, sinusitis, pneumonia, and bronchitis |
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Haemophilus meningitis: transmitted, prevention, treatment, signs and symptoms
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Transmitted through discharges from nasopharynx
Similar to meningococcal meningitis Symptoms and signs: Fever, vomiting, stiff neck, neurological impairment Treatment: Combination of chloramphenicol and ampicillin is usually effective Untreated cases have 90% fatality rate, but even with prompt diagnosis and treatment, 33% of children sustain residual disability Prevention: Outbreaks in families and day cares may necessitate rifampin prophylaxis of contacts Subunit vaccine available, often delivered with DTaP |
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Syphilis: Treponema Pallidum
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Causes Syphilis
Human is the natural host Extremely fastidious and sensitive; cannot survive long outside of the host sexually transmitted and transplacental |
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Genus Treponema
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Thin, regular, coiled cells
Live in the oral cavity, intestinal tract, and perigenital regions of humans and animals Pathogens are strict parasites with complex growth requirements Require live cells for cultivation |
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Stages of Syphilis
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Primary:
Spirochete binds to the epithelium, multiplies, and forms a chancre Fluid from the chancre is highly contagious Chancre spontaneously heals as the spirochete moves into the blood Secondary Spirochete is multiplying in the bloodstream Rash forms on the skin, palms and soles with fever, headache and sore throat The rash disappears spontaneously Latency/Tertiary If left untreated, tertiary syphilis forms Damage to multiple tissues and organs Cardiovascular and Neuromuscular |
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Syphilis Diagnosis and Testing
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Stages of syphilis can mimic other diseases
Consider symptoms, history, microscopic, and serological testing RPR, VDRL, FTA-ABS Treatment: penicillin G |
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Lyme Disease:Borrelia burgdorferi
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Complex lifecycle involving mice and deer and transmission by ticks
Acquired by tick bites Nonfatal, slowly progressive syndrome that mimics neuromuscular and rheumatoid conditions 50-70% get bull’s eye rash Fever, headache, stiff neck, and dizziness If untreated can progress to cardiac and neurological symptoms, polyarthritis Treated with tetracycline or amoxicillin |
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Campylobacteriosis: Campylobacter sp.
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Slender, curved, or spiral bacilli, often S-shaped or gull-winged pairs
Polar flagella Common residents of the intestinal tract, genitourinary tract, the oral cavity of birds and mammals Most important: Campylobacter jejuni Campylobacter fetus |
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Campylobacter jejuni: Bacterial
Gastroenteritis |
Important cause of bacterial gastroenteritis
Transmitted by beverages and food Reach mucosa at the last segment of small intestine near colon; adhere, burrow through mucus and multiply Heat-labile enterotoxin CJT stimulates a secretory diarrhea like that of cholera Symptoms of headache, fever, abdominal pain, bloody or watery diarrhea Treatment with rehydration and electrolyte balance therapy |
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Rickettsia Genus
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Small obligate intracellular parasites
Gram-negative cell wall Nonmotile pleomorphic rods or coccobacilli Ticks, fleas, and lice are involved in their life cycle Bacteria enter endothelial cells and cause necrosis of the vascular lining – vasculitis, vascular leakage, and thrombosis |
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Rocky Mountain Spotted Fever: Rickettsia rickettsi
transmitted |
Rickettsia rickettsii is transmitted to humans through a tick bite and is the most common rickettsial infection in North America
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Rocky Mountain Spotted Fever: signs, treatment, and prevention
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First symptoms are fever, chills, headache and a spotted rash appears in days
If untreated central nervous system can become involved and fatality rates are 20% if untreated Requires immediate treatment, even in suspected cases Diagnosed by analyzing for rickettsias in tissue biopsy or blood Treated with tetracycline or chloramphenicol Prevention: Protective clothing, insect repellant New vaccine has shown some success in protecting at-risk individuals |
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Chlamydial urethritis: Chlamydia trachomatis
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Human reservoir and 2 strains can infect humans:
Trachoma – attacks the mucous membranes of the eyes, genitourinary tract, and lungs Ocular trachoma – severe infection, deforms eyelid and cornea, may cause blindness Inclusion conjunctivitis – occurs as baby passes through birth canal; prevented by prophylaxis STD – second most prevalent STD; urethritis, cervicitis, salpingitis (PID), infertility, scarring Lymphogranuloma venereum – disfiguring disease of the external genitalia and pelvic lymphatics |
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Chlamydial urethritis: symptoms,diagnosis, treatment, and prevention
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Symptoms: urethritis, cervicitis, salpingitis (PID), infertility, scarring
Diagnosis: often requires examination of host cells, culturing analyses, or molecular analyses Treatment: intracellularly acting antibiotics (tetracyclines and azithromycin) Prevention: condom use; pro-phylactic treatment of partners of infected individuals |
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The Chlamydiaceae Family
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Small, gram-negative, obligate intracellular parasites
Alternates between: Elementary body – small metabolically inactive, extracellular, infectious form released by the infected host Reticulate body – noninfectious, actively dividing form, grows within host cell vacuoles |
