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Bacterial Diseases
Gram-positiveGram-negative
Rickettsias, Chlamydias, Spirochetes and Vibrios
Bacterial Diseases Classified by:
AirborneUpperLower
FoodborneWaterborneSoilborneArthropodbornePhysical Contact
STDContact Animal
Or by…..
Physiological properties:Catalase
Hydrogen peroxide water
OxidaseWater hydrogen peroxide
PeroxidaseBreakdown peroxidase (by-products that cause
tissue damage)
Or, by……..
Gram-positiveGram-negativeRickettsias, Chlamydias, Spirochetes and
Vibrios
Gram-positive bacteria
Staphylococcus aureusCapsule!grows in large, round,
opaque coloniesoptimum temperature
37oCfacultative anaerobewithstands high salt,
extremes in pH, & high temperatures
produces many virulence factors
Enzymes of S. aureusCoagulase
coagulates plasma and blood
produced by 97% of human isolates
Hyaluronidasepromotes invasion
Staphylokinasedigests blood clots
Dnasedigests DNA
Lipaseshelps bacteria colonize oily
skin
Penicillinase inactivates penicillin
Toxins of S. aureus
hemolysins lyse RBCs
Leukocidindamages cell membranes
Enterotoxinsact in the gastrointestinal tract
exfoliative toxinseparates epidermal layers
toxic shock syndrome toxin (TSST)
Epidemiology and PathogenesisPresent in most environments frequented by
humansReadily isolated from fomitesCarriage rate for healthy adults is 20-60%
mostly in anterior nares, skin, nasopharynx, intestine
Predisposition to infection include: poor hygiene and nutrition, tissue injury, preexisting
primary infection, diabetes, immunodeficiency
Increase in community acquired methicillin resistance MRSA
Staphylococcal Disease - 1Localized cutaneous infections – invade skin through
wounds, follicles, or glands folliculitis
superficial inflammation of hair follicleusually resolved with no complications but can progress
furuncle Boilinflammation of hair follicle or sebaceous gland progresses into abscess
or pustule carbuncle
larger and deeper lesion created by aggregation and interconnection of a cluster of furuncles
impetigo bubble-like swellings that can break and peel awaymost common in newborns
Staphylococcal Disease - 2
Systemic infections osteomyelitis
infection is established in the metaphysis
abscess formsbacteremia
primary origin is bacteria from another infected site or medical devices
endocarditis possible
Staphylococcal Disease - 3Toxigenic disease
food intoxicationingestion of heat stable
enterotoxinsgastrointestinal 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
Other Staphylococci
S. epidermidis lives on skin & mucous
membranesendocarditis, bacteremia, UTI
S. hominis lives around apocrine sweat
glandsS. capitis
live on scalp, face, external ear
S. saprophyticus infrequently lives on skin,
intestine, vagina; UTI
Streptococci
Gram-positive spherical/ovoid cocci arranged in long chainsNon-spore-forming, nonmotileCan form capsules & slime layersFacultative anaerobesSensitive to drying, heat & disinfectants 25 species
Streptococci
Lancefield classification system based on cell wall Ag 17 groups (A,B,C,….)
Another classification system is based on hemolysis reactions -hemolysis
A,B,C,G & some D strains –hemolysis
S. pneumoniae & others collectively called viridans
γ-hemolysis Enterococcus faecalis does not induce hemolysis
StreptococciSkin infections Impetigo (pyoderma)
superficial lesions that break and form highly contagious crust
often occurs in epidemics in school children
associated with insect bites, poor hygiene, and crowded living conditions
Erysipelas pathogen enters through a break in the
skin eventually spreads to the dermis and
subcutaneous tissues can remain superficial or become
systemic
Throat infections Streptococcal pharyngitis
strep throat
-hemolytic S. pyogenes
Most serious streptococcal pathogen
Inhabits throat, nasopharynx, occasionally skin
Produces C-carbohydrates, M-protein (fimbrae), streptokinase, hyaluronidase, DNase, hemolysins
S. pyogenes
GASProduces toxinsHumans only reservoirTransmission
contact, droplets, food, fomites
Skin infections pyoderma, impetigo,
erysipelas
Systemic infections strep throat, pharyngitis,
scarlet fever
S. pyogenes
Causes streptococcal pharyngitis Strep throat enters the upper
respiratory tract through respiratory droplets
Some patients with strep throat may develop scarlet feverexhibiting a rash caused
by erythrogenic exotoxins
S. pyogenes
Rheumatic fever serious complication
affecting the joints and heart
causes permanent heart damage called rheumatic heart disease
Acute glomerulonephritus rare inflammatory
response to M proteins may lead to renal damage
Group B: S. agalactiae
Regularly resides in human vagina, pharynx & large intestine
wound and skin infections & endocarditis in debilitated people
can be transferred to infant during delivery & cause severe infectionMost prevalent cause of neonatal pneumonia, sepsis, &
meningitisTargets infants without Ab, and mothers that do not
provide passive immunityPregnant women should be screened & treated
“Typical” Pneumonia Can Be Caused by Several Bacteria:
80% of “typical” pneumonia cases are caused by Streptococcus pneumoniae
Others: Haemophilus
influenzaeStaphylococcus aureusKlebsiella pneumoniae
Streptococcus pneumoniae
Small, lancet-shaped cells arranged in pairs and short chains
Culture requires blood or chocolate agar
Growth improved by 5-10% CO2
Lack catalase & peroxidases cultures die in O2
S. pneumoniae
All pathogenic strains form large capsules major virulence factor
Vaccine available for high risk people
S. Pneumoniae Epidemiology
5-50% of all people carry it as normal flora in pharynx
Does not survive long outside of its habitatPneumonia occurs when cells are
aspirated into the lungs of susceptible individuals
Pneumococci multiply induce inflammatory response
Traditionally treated with penicillin G or VIncreased drug resistance
Cultivation and Diagnosis
Gram stain of specimen presumptive identification
α hemolyticQuellung test or capsular swelling
reaction
Bacillus
gram-positiveendospore-formingmotile rodsmostly saprobic
primary habitat is soilversatile in degrading complex macromoleculessource of antibiotics2 species of medical importance
Bacillus anthracisBacillus cereus
Bacillus anthracis
facultativelarge, block shaped
rodscentral spores
develop under all conditions except in the living body
virulence factors capsule & exotoxins
Bacillus anthracis3 types of anthrax
Cutaneous spores enter through skin,
black soreleast dangerous
Pulmonary inhalation of spores
Gastrointestinal ingested spores
treated with penicillin or tetracycline
http://www.youtube.com/watch?v=mi3sYzDsSGI
Bacillus cereus
common airborne & dustborne
grows in foods, spores survive cooking & reheating
ingestion of toxin-containing food causes nausea,
vomiting, abdominal cramps & diarrhea
24 hour durationno treatmentspores abundant in the
environment
Clostridiumgram-positivespore-forming rodsAnaerobic 120 speciesoval or spherical spores produced only under
anaerobic conditionscause wound & tissue infections and food intoxications
C. difficileC. botulinumC. perfringensC. tetanis
Clostridium difficile-Associated Disease (CDAD)
Normal resident of colon, in low numbers
Causes antibiotic-associated colitis relatively non-invasive treatment with broad-spectrum
antibiotics kills the other bacteriaallowing C. difficile to
overgrow Produces enterotoxins that
damage intestines Major cause of diarrhea in
hospitals Increasingly more common in
community acquired diarrhea
Clostridium botulinum
Anaerobic, endospore-forming, Gram-positive bacillus
Common in soil and waterBotulism results when the endopsores germinate
and produce botulism toxins
Clostridium botulinum
Causes 3 diseases1. food poisoning
o spores are in soil, may contaminate vegetables
o improper canning does not kill spores & they germinate in the can producing botulinum toxin
toxin causes paralysis by preventing release of acetylcholine
2. infant botulism o caused by ingested spores that germinate & release
toxin
3. wound botulismo spores enter wound & cause food poisoning symptoms
Clostridium botulinumDiagnosis
Symptoms are diagnostic
TreatmentAdminister neutralizing antibodies against botulism
toxinAdminister antimicrobial drugs in infant botulism cases
PreventionProper canning of foodInfants under 1 year should not consume honey
Gangrene Mass of body tissue dies (necrosis)Usually occurs when blood flow ceases to a
part of the body
Types :Gas gangrene (myonecrosis)
caused when spores enter the body through a severe open wound
Dry gangreneWet gangrene
Clostridium perfringens
Clostridium perfringens
Vegetative cells ferment muscle carbohydrates and decompose muscle proteins
Large amounts of gas accumulate under the skin causing a crackling sound
-toxin damages and lyses blood cells
Treatment involves:Antibiotics tissue debridementAmputationexposure in a hyperbaric
oxygen chamber
Clostridium tetani
Tetanus Causes hyperactive muscle contractions
Spores can enter the body through a woundproduce toxins
• Tetanospasmin inhibits compounds needed to inhibit muscle contraction
Symptoms of tetanus include:Trismus (lockjaw)
involves spasms of the jaw muscle and clenching of the teeth
Opisthotonusinvolves muscle spasms that cause an arching of the back
Spasmodic inhalation and seizures in the diaphragm and rib cagereduces ventilation
Sedatives, muscle relaxants, and penicillin are used in treatment
Tetanus toxoid is used in vaccination
Clostridium tetani
Listeria monocytogenesnon-spore-forming gram-positive
coccobacilli 1-4 flagellano capsulesresistant to cold, heat, salt, pH extremes &
bileprimary reservoir is soil & watercan contaminate foods & grow during
refrigeration
Listeria monocytogenes
Listerosis immunocompromised patients,
fetuses & neonates affects brain & meninges
20% death rate
ampicillin & trimethoprim-sulfamethoxazole
Prevention pasteurization & cooking
Mycoplasmas
M. pneumoniae primary atypical
pneumoniaWalking pneumonia
pathogen slowly spreads over interior respiratory surfaces
causes fever, chest pain and sore throat
Corynbacterium diptheriae
gram-positive irregular bacilli 2 stages of disease:
1. Local infection –upper respiratory tract inflammation
– sore throat, nausea, vomiting, swollen lymph nodes, pseudomembrane formation can cause asphyxiation
2. Diptherotoxin production and toxemia target organs primarily heart and
nerves
Epidemiology and Pathology
Reservoir of healthy carrierspotential for diphtheria
is always presentMost cases occur in non-
immunized children living in crowded, unsanitary conditions
Acquired via respiratory droplets from carriers or actively infected individuals
Corynbacterium diptheriae
Diagnostic methods Pseudomembrane and swelling indicativeStainsConditions, historySerological assay
Treatment:AntitoxinPenicillin or erythromycin
Prevented by toxoid vaccine series and boosters
Mycobacterium Genus
gram-positive irregular bacilliacid-fast stainingstrict aerobes produce catalasepossess mycolic acids & a unique type of
peptidoglycando not form capsules, flagella or sporesgrow slowly2 medically important:
Mycobacterium tuberculosisMycobacterium leprae
Mycobacterium tuberculosis
contain complex waxes & cord factor prevent destruction by
lysosomes of macrophages
transmitted by airborne respiratory droplets
only 5% infected people develop clinical disease
Primary TB
infectious dose 10 cellsphagocytosed by
alveolar macrophages multiply intracellularly
after 3-4 weeks immune system attacks, forming tuberclesgranulomas consisting
of a central core containing bacilli surrounded by WBCs
Secondary TB
reactivation of bacillitubercles expand & drain into the
bronchial tubes & upper respiratory tractgradually patient experiences more
severe symptomsviolent coughing, greenish or bloody sputum,
fever, anorexia, weight loss, fatigueuntreated 60% mortality rate
Extrapulmonary TB
during secondary TB, bacilli disseminate to regional lymph nodes, kidneys, long bones, genital tract, brain, meninges
these complications are grave
Diagnosis
1. in vivo or tuberculin testing
2. X rays
3. direct identification of acid-fast bacilli in specimen
4. cultural isolation and biochemical testing
Treatment of TB
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 bacilliCalmet-Guerin strain of M. bovis used in
other countries
Mycobacterium leprae
Hansen’s bacillusstrict parasite slowest growing of all speciesmultiplies within host cells in large packets
called globicauses leprosy
chronic disease that begins in the skin & mucous membranes & progresses into nerves
Leprosy (Hansen’s Disease)
spread through direct inoculation from leprotics
2 formstuberculoid
superficial infection without skin disfigurement
damages nerves and causes loss of pain perception
lepromatous deeply nodular infection causes severe disfigurement of the
face & extremities
Diagnosing
Combination of symptomology, microscopic examination of lesions, and patient history
Detection of acid-fast bacilli in skin lesions, nasal discharges, and tissue samples
Treatment and Prevention
Treatment by long-term combined therapy
Prevention requires constant surveillance of high risk populations
WHO sponsoring a trial vaccine
Gram-negative Cocci and Bacilli
Bacterial Meningitis
meninges of brain and spinal cordcross the blood-brain
barrier
can be caused by several bacterial speciesNeisseria meningitides Streptococcus
pneumoniaeHaemophilus influenzae
Neisseria
Gram-negative diplococcinone develop flagella or sporescapsules on pathogensStrict parasites
do not survive long outside of the hostResidents of mucous membranes of warm-blooded
animalsAerobic or microaerophilicPathogenic species require enriched complex media and
CO2
2 primary human pathogens Neisseria gonorrhoeae Neisseria meningitidis
Neisseria meningitidis
Virulence factors capsule, pili, IgA protease
12 strainsserotypes A, B, C, cause most cases
Disease begins when bacteria enter bloodstream, pass into cranial circulation, multiply in meningesvery rapid onsetendotoxin causes hemorrhage and shockcan be fatal
Treated with penicillin, chloramphenicolVaccines exist for group A and C
Neisseria gonorrhoeae
Causes gonorrheaVirulence factors
pili, other surface molecules, IgA proteaseStrictly a human infectionIn top 5 STDsInfectious dose 100-1,000Does not survive more than 1-2 hours on
fomitesInfection is asymptomatic in 10% of males and
50% of females
Gonorrhea
Males urethritis, yellowish
discharge, scarring & infertility
Extragenital infectionsanal, pharygeal,
conjunctivitis, septicemia, arthritis
Gonorrhea
Females vaginitis, urethritis,
salpingitis (PID) mixed anaerobic abdominal infection
common cause of sterility & ectopic tubal pregnancies
Gonorrhea in Newborns
Infected as they pass through birth canal
Eye inflammation, blindness
Prevented by prophylaxis after birth
Diagnosis and Control
Gram stain20-30% of new cases are
penicillinase-producing PPNG or tetracycline resistant TRNG
Recurrent infections can occur
Reportable infectious disease
Enterobacteriaceae Family
Enterics gram-negative bacteria many members inhabit soil,
water, & decaying matter cause diarrhea through
enterotoxins divided into coliforms (lactose
fermenters) and non-coliforms (non lactose fermenters)
Antigens and virulence factors of typical enteric bacteria
Testing of Enterics
miniaturized, multichambered tube inoculating rod pulled through length of
tubecarries an inoculum to all chambers
Coliform Organisms and Diseases: Escherichia coli
most common aerobic & non-fastidious bacterium in gut
@ 150 strainsMost not infectious
Escherichia coli
enterotoxigenic E. coli causes severe diarrhea due to heat-labile toxin &
heat-stable toxin stimulate secretion & fluid lossalso has fimbrae
enteroinvasive E. coli causes inflammatory disease of the large intestine
enteropathogenic E. coli linked to wasting from infantile diarrhea
Enterohemorrhagic E. coliNewest strainCan permanently damage kidney
Escherichia coli
pathogenic strains frequent agents of infantile diarrhea greatest cause of mortality among babies
causes ~70% of traveler’s diarrheacauses 50-80% UTIindicator of fecal contamination in water
Other Coliforms
Serratia marcescensproduces a red pigmentcauses pneumonia,
burn & wound infections, septicemia & meningitis
Klebsiella pneumoniae
Citrobacter opportunistic UTIs &
bacteremia
Salmonella
S. enteritidis 1,700 serotypes salmonellosis zoonotic gastroenteritis 2-5 days
Typhoid Fever
caused by Salmonella enterica serotype Typhi (S. typhi) typhoid fever ingested bacilli adhere to small
intestine cause invasive diarrhea that leads
to septicemia
S. Typhi is transmitted by the five Fs: Flies Food Fingers Feces Fomites
Shigella
shigellosis incapacitating dysentery
S. dysenteriae, S. sonnei, S. flexneri & S. boydii
produce H2S or ureaseNonmotilenonencapsulated
Shigella
invades villus of large intestinecan perforate intestine or invade blood
enters Peyer’s patches & instigates inflammatory response endotoxin & exotoxins
treatment fluid replacement & ciprofloxacin & sulfa-trimethoprim
Yersinia pestis
tiny, gram-negative rodunusual bipolar staining & capsulesvirulence factors
capsular & envelope proteins protect against phagocytosis & foster intracellular growth
coagulase
Yersinia pestis
sylvatic plague humans develop plague through contact with wild
animals urban plague
domestic or semidomestic animals or infected humansfound in 200 species of mammals
rodents harbor the organism but do not develop the disease
flea vectors bacteria replicates in gut, coagulase causes blood
clotting that blocks the esophagus flea becomes ravenous
Pathology of Plague bubonic
bacillus multiplies in flea bite, enters lymph, causes necrosis & swelling in groin or axillabubo
septicemic progression to massive bacterial growth virulence factors cause intravascular
coagulation subcutaneous hemorrhage & purpura black plague
pneumonic infection localized to lungs, highly
contagious fatal without treatment
Plague
Treatmentstreptomycin,
tetracycline or chloramphenicol
Killed or attenuated vaccine
http://www.youtube.com/watch?v=9IjhQDnoCcY
Bordetella pertussis
aerobic coccobacilluscauses pertussis or whooping cough
communicable childhood affliction acute respiratory syndromeoften severe, life-threatening complications in
babiesreservoir
apparently healthy carrierstransmission by direct contact or inhalation of
aerosols
Bordetella pertussis
virulence factorsreceptors that recognize & bind to ciliated
respiratory epithelial cellstoxins that destroy & dislodge ciliated cells
DTaP vaccine acellular vaccine contains toxoid & other Ags
Pseudomonas
small gram-negative bacilli single polar flagellumhighly versatile metabolism
Pseudomonas aeruginosa
intestinal resident in 10% normal peopleresistant to soaps, dyes, quaternary
ammonium disinfectants, drugs, dryingUse aerobic respiration
do not ferment carbohydrates
Opportunistic
Pseudomonas aeruginosacommon cause of nosocomial infections in hosts
with burns, neoplastic disease, cystic fibrosiscomplications include pneumonia, UTI,
abscesses, otitis, & corneal diseasegrapelike odorgreenish-blue pigment (pyocyanin)multidrug resistant
Francisella tularensiscauses tularemia
zoonotic disease of mammals (particularly rabbits)endemic to the northern hemisphere
Aerobic bacillitransmitted by contact with infected animals,
water & dust or bites by vectorsheadache, backache, fever, chills, malaise &
weaknessintracellular persistence can lead to relapse30% death rate in systemic & pulmonic forms
gentamicin or tetracycline
Mycoplasma pneumoniae Legionella pneumophilaCoxiella burnetiiChlamydia pneumoniaeChlamydia psittaci
“Atypical” Pneumonia Can Be Caused by a Diverse Group of Bacterial Species
Legionella pneumophila
“Legionellosis”, Legionaires disease
Motile aerobic bacilliwidely distributed in water live in close association with
amebasprevalent in males over 50nosocomial disease in elderly
patients fever, cough, diarrhea,
abdominal pain, pneumonia fatality rate of 3-30%azithromycin
Rickettsias, Chlamydias, Spirochetes and Vibrios
Rickettsia
obligate intracellular parasitesgram-negative cell wallamong the smallest bacterianonmotile pleomorphic rods or coccobacilliticks, fleas & louse are involved in their life cycle bacteria enter endothelial cells & cause necrosis
of the vascular lining treat with tetracycline & chloramphenicol
4 Types of Rickettsioses
Rocky Mountain spotted fever R. rickettsii zoonosis carried by dog ticks & wood ticks most cases on eastern seaboard distinct spotted rash
Chlamydias
obligate intracellular parasites
small gram-negative cell wall
alternate between 2 stageselementary body
small metabolically inactive, extracellular, infectious form
reticulate body grows within host cell
vacuoles
Chlamydia trachomatis 1. trachoma
attacks the mucous membranes of the eyes, genitourinary tract & lungsocular trachoma
• severe infection, deforms eyelid & cornea, may cause blindness
inclusion conjunctivitis • occurs as babies pass through birth
canal• prevented by prophylaxis
2. STD urethritis, cervicitis, scarring lymphogranuloma venereum
disfiguring disease of the external genitalia & pelvic lymphatics
Spreading to the fallopian tubes can cause salpingitis
Left untreated can cause pelvic inflammatory disease (PID)
Increases the danger of infertility or ectopic pregnancies
Chlamydia can also occur in the pharynx or anus
Males complain of painful urination and watery dischargecause infertility in males
Spirochettes
Treponema
Borrelia
Treponema
Gram-negative spirochetes live in the oral cavity, intestinal tract, &
perigenital regions of humans & animalspathogens are strict parasites
Treponema pallidum
human is the natural hostextremely fastidious &
sensitivecannot survive long outside
of the hostcauses syphilis ID = 50 cells
Pathogenesis and Host Response
Spirochete binds to epithelium, multiplies, and penetrates capillaries.
Moves into circulation and multiplies Untreated marked by stages
PrimarySecondaryTertiary
Spirochete appears in lesions and blood during first 2 stages communicable
Stages of Syphilis
Primary syphilis appearance of hard
chancre at site of inoculation
chancre heals spontaneously
Secondary syphilis fever, headache, sore
throat, red or brown rash on skin, palms and soles
rash disappears spontaneously
Stages of Syphilis
Tertiary syphilis about 30% of infections enter
in tertiary stage can last for 20 years or longerneural, cardiovascular
symptoms, gummas developCongenital syphilis
nasal discharge, skin eruptions, bone deformation, nervous system abnormalities
Borrelia
Borrelioses Gram-negative spirochetestransmitted by arthropod vectorB. hermsii
relapsing fever
B. burgdorferi Lyme disease
B. hermsii - Relapsing Fevermammalian reservoirs
squirrels, chipmunks, wild rodentstick-borneafter 2-15-day incubation, patients have high
fever, shaking, chills, headache, & fatigueNausea, vomiting, muscle aches, abdominal
painextensive damage to liver, spleen, heart, kidneys, &
cranial nervesparasite changes & immune system tries to
control itrecurrent relapses
tetracycline
B. burgdorferi - Lyme Disease
transmitted by tickscomplex 2-year cycle
involving mice & deernonfatal, slowly
progressive syndrome that mimics neuromuscular & rheumatoid conditions
B. burgdorferi - Lyme Disease
Symptoms:70% get bull’s eye rash fever, headache, stiff
neck, & dizziness if untreated can progress to
cardiac & neurological symptoms, polyarthritis
tetracycline, amoxicillinvaccine for dogs, human
vaccine discontinued insect repellant containing
DEET
Vibrio cholera
CholeraCurviform gram-
negativetop 7 causes of
morbidity & mortalityingested with food or
waterinfectious dose 108
Vibrio cholera
infects surface of small intestine, noninvasive
cholera toxin causes electrolyte & water loss through: secretory diarrhea, resulting dehydration leads
to muscle, circulatory, & neurological symptomsTreatment
oral rehydration, tetracyclinevaccine
Campylobacter jejuni
important cause of bacterial gastroenteritis
transmitted by beverages & food
Curviform gram-negative reach mucosa at the last
segment of small intestine near colonadhere, burrow through
mucus and multiplysymptoms of headache,
fever, abdominal pain, bloody or watery diarrhea
Helicobacter pylori
Curviform gram-negativediscovered in 1979 in stomach biopsied
specimens causes 90% of stomach & duodenal ulcerspeople with type O blood have a 1.5-2X
higher rate of ulcersSame receptor in common
produces large amounts of urease
The bacteria produce urease, which in turn produces ammonianeutralizes acid in
that area of the stomach
allows the bacteria to survive
The ammonia, and an H. pylori cytotoxin destroy mucous-secreting cellscreates a sore
© P. Hawtin/Photo Researchers, Inc.