Bacteriology Summary
Bacteriology Summary
Bacteriology Summary
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Lec 1
Joseph Lister(1860) = father of aseptic techniques
Robert Hooke(1876) = Cell theory + proved that a specific bacteria caused
disease
Kochs Postules Exceptions = Vaccination
Edward Jenner (1796)= invented vaccines (vacc. of cowpox protected from
smallpox too)
Anton van Leuwenheuk(1673) = 1st microscope
Louis Pasteur: disproved spontaneous generation, fermentation,
Pasteurization, Silkworm disease cause, Rabies vaccine, Aerobes and
Anaerobes + Pasteur Institute
Protozoa = unicellular eukaryotes
Quinine= to treat malaria
Salversan = to treat syphilis, discovered by Paul Ehlrich
Compound light microscope resolution = 0.2um
Numerical aperture= ability to gather light
Phase contrast microscopy= useful for examining live specimens
UV light = short wavelength
Pseudomonas fluoresce naturally under light
Flagellar H protein is an antigen in E.coli
Fimbriae and Pilli(proteins) = for attachment not motility
Exotoxin= LPS eg. O antigens !! Endotoxin(fatal causes septic schock)=protein
eg.Lipid A
Mycoplasma and Nocardia = Acid fast (coz they contain mycolic acid)
Mycoplasma lacks cell wall
Archeas cell wall has NO peptidoglycan
Protoplast = product of destruction of gram +ve cell wall
Spheroplast = remain of partial destruction of gram ve cell wall
Bacteria contain plasmids = extrachromosomal DNA molecules
Antibiotics work on prokaryotic ribosomes(70s)not eukaryotic ribosomes(80s)
Inclusion bodies(reserve deposits) = found in prokaryotic and eukaryotic cells
Gram +ve Endospores = resting structures formed by BACILLUS(aerobes) AND
CLOSTRIDIUM(obligate anaerobes)
Sporulation = process of endospore formation
Germination = return of endospore to vegetative state
E.coli O157:H7 causes bloody diarrhea
(E.coli also causes food poisoning)
Gram ve strictly aerobes = PSUEDOMONAS + NEISSERIA(causes gonorrhea)
I.
II.
III.
IV.
V.
2. PH
I.
II.
III.
IV.
Pschrophiles (cold-loving)
Mesophiles (moderate temp loving)
Thermophiles (heat-loving)
= 60
Physchrotrophes
Hyperthermophiles (grow at 80 degrees eg. Archea)
Acidophilic
Neutrophilic
Basophilic
Halophilic (salt loving)
3. Osmotic
I. Hypertonic
(causes Plasmolysis = cell shrinkage)
II. Isotonic
III. Hypotonic
(causes cell burst)
4. Oxygen [SOD enzyme is to break down superoxide free radicals,
NOT FOUND IN Anaerobes or Microaerophiles]
I.
Selective Media
Differential media
a. Blood agar = bacteria that destroys RBCS(hemolysis) eg. S.PYOGENES
Reproduction in Prokaryotes
1.Binary fission (main method for bacteria)
2.Budding
3.Conidiospores (eg.actinomycetes)
4.Fragmentation of filaments
Generation time = time required for a cell to divide and its population to double
Bacterial growth curve:
I.
Lag phase= adjustment to new conditions
II.
Log phase= cells produced more than cells dying(affected by radiation and antibiotics)
III.
Stationary phase= cells produced = cells dying ( rate of prod decreased due to) :
Accumulation of toxic waste material
Acidic ph of media
Limited nutrients
Insufficient oxygen supply
IV.
Death or decline phase = cells dying greater than cells produced
Biosafety levels : 1 - 4 (eg. Ebola)
Commercial sterilization: killing CLOSTRIDIUM BOTULINUM endospores
Sterilization : by autoclave (121 C for 15 mins)
Pasteurization includes
63 C for 30 mins
2 C for 15 sec
140 C for <1 min
*** DESTRUCTION OF ENDOSPORES:
OR
Lec 2
ANTIBIOTICS
Aminoglycoside
antibiotics = Streptomycin+ Gentamycin + Neomycin
Works on 30s
Against gram -ve bacteria
Cause auditory nerve damage and kidneys
Streptomycin _____ TB
Gentamycin_______ Pseudomonas
Neomycin______ tropical application
Tetracyclines
Works on 30s
Produced by Streptomyces spp.
Effective against gram + and -ve as well as intracellular bacteria
Reacts with 30s subunit interferes woth attachment of tRNA at ribosome
Used to treat UTI, syphillis and gonnorhea
Macrolides
(eg erythromycin) and (azithromycin)
Bacteriostatic acts on protein synthesis
Against gram +ve cocci
Used to treat RTI, GIT and genital
Rifampin
Quinolone
Inhinits DNA gyrase reponsible for DNA replication
Used for UTI
Floroquinolones
(eg Norfloxacin and Ciprofloxacin)broad spectrum , for UTI skin infections
and resp infections
Cipro = for anthrax
Polymyxin B
fungicidal, acts on cell membrane, narrow spectrum
Effective against gram -ve (Pseudomonas)
Sulfonamides
inhibit mtabollic processes(EG.septrin = bacteriostatic and broad
spectrum)
Inhibits folic acid synthesis by PABA
Inhibitory activity of sulfa drugs is by SIMILARITY in structure with PABA
NOTE: READ ALL TESTS IN LEC 3 SLIDE 41-48
LEC 5-6
Common causes of nosocomial infection:
1. Staphylococci
2. S.aureus
3. Enterococcus
4. C.difficile
3 types of exotoxin
1. AB toxin (eg.botulinum and tetanus toxin)
2. Membrane disrupting toxins(eg leukocidins) and (hemolysins like S.pyogenes)
3. Superantigens cause release of cytokines( eg. Staphylococcus)
TYPES OF EXOTOXINS:
1) Cytotoxin
i) Diptheria toxin( AB Toxin that inhibits protein synthesis)
-from Corynebacterium diptheria
ii) Erythrogenic toxin (superantigens that damage capillaries) -from S.pyogenes
2)Neurotoxin
i)Botulinum toxin (AB toxin that prevents nerve impulse transmission, results in flaccid
paralysis)
- from Corynebacterium botulinum
ii)Tetanus toxin or Tetanospasmin (AB toxin that prevents inhibitory nerve impulse
transmission, results in spasmodic muscle contractions)
-from Clostridium tetani
3)Enterotoxin
i)Vibrio enterotoxin(AB toxin stimulates secretion of fluid and electrolytes causing
diarrhea.
-from Vibrio Cholerae
ii)Staphylococcus aureus(superantigen)
-from Staphylococci
S.pyogenes = membrane disrupting exotoxin. Erythrogenic.
Endotoxins = from Lipid A component of gram ve only, LPS, has fever, no antitoxin, large
LD50 and less toxic
Endotoxins are released by= bacterial cell death, antibiotics and antibodies
Endotoxins cause macrophages to release large amounts of cytokines(symptoms fever and
shock)
Organisms that have endotoxins include:
1. Salmonella typhi
2. Proteus sp.
3. Neisseria meningitides
S.aureus (superantigen) causes eith food poisoning, or toxic shock syndrome
Clostridim sp. (membrane disrupting) (eg. C.perfringes gas gangrene and food poisoning)
(eg.C.difficileantibiotic-assosciated diarrhea)
E. coli and Shigella cause Travellers diarrhea
S.pneumonie alpha hemolytic, optochin sensitive, bile soluable and capsulated(+ve quelling test)
S.viridans (eg.mutans or sanguis), optochin resistant, not bile soluable and no capsule
(Lec 7)
DIGESTIVE SYSTEM
Tooth decay or DC = Endogenous infection
PORPHYROMONAS GINGIVALIS:
A. Most likely cause of periodontal disease
B. Belongs to bacteroids
C. Non motile
D. Gram ve
E. Rod-shaped
F. Pathogenic bacterium
Enterobacteriaceae
1. Grow in aerobic or anaerobic conditions
2. Ferment glucose
3. All motile EXCEPT: Shigella and Klebsiella
4. 2 toxins [Exotoxin = Enterotoxin and Cytotoxin called shiga] and
[Endotoxin = E.coli]
5. Other eg. Yersinia, Salmonella, Klebsiella, Enterobacter and Proteus
Antigenic structure
A. O antigen: LPS (endotoxin) is Heat stable
B. H antigen: flagellar protein is Heat labile
C. K antigen: capsular(surface)
E.coli :
Shingella
Shigellosis = non motile, non lactose fermenting and causes Bacillary
Dysentry
Shigellosis or bacillary dysentery primary causes:
Shigella dysenteriae
Shigella sonnei
Shigella flexneri
Shigella boydi
Salmonella:
Gram ve rod
Motile pertrichious
Most produce Hydrogen Sulphide
Detected by growing on ferrous sulfate
Cause = typhoid fever, paratyphoid fever and food-borne illnesses
Sources ( Peter)= birds and turtles/ food= egg, meat and chicken
L: tract of humans and other animals
Impo. Species = S.typhi, S.paratyphi, S.enteritidis (almost all are
pathogenic)
Transmission = eating raw or undercooked food/ Orofecal route
Salmonellosis = food-borne disease
Salmonella typhi and paratyphi cause TYPHOID FEVER
S.typhi= humans are the only reservoir mafi in animals, spread through
human feces, does not produce H2S gas in lab.
Typhoid fever= usually assoc with ulceration of intestinal wall, often resides
in gallbladder of asymptomatic hosts (eg. Typhoid Mary), treatment=
antibiotic and vaccine
Coliform bacteria = E.COLI
Klebsiella
Impo species. = Klebsiella pneumonie [ Opportunistic pathogens]
Causes Chest infections, bronchopneumonia, lung abscesses, UTI,
septicemia.
Cholera:
Life threatening disease
Results in hypovolemic shock and acidosis
Campylobacter Gastroenteritis
Cause = Campylobacter jejuni
Campylobactor species = gram ve, microaerophilic,nonferemnting,motile,oxidase-+ve, grow at 37 and 42 C, source = birds and
untreated birds, transmission = orofecal route, most common cause of
diarrhea.
Lab diagnosis = darting motility, in dark field microscopy, capnophilic,
thermophilic, oxidase and catalase +ve, sensitive to nalidixic acid,
antibiotic = Modified Skirrow medium( Erythromycin and Ciprofluxacin)
Guillian Barre Syndrome= most coomon cause of acute neuro-muscular
paralysis, due to formation of antibodies against C.jejuni
Helicobacter pylori:
Major transmission = person to person contact
Assoc with Chronic Superfiscial Gastritis
Responsible for most peptic ulcer diseases(gastric and duodenal ulcers)
Usually asyptomatic
Cariogenic bacterium and gastric cancer
Lives in mucus layer over but protected from gastric acid
Most effiecient producers of urease hence relaeases NH3 to buffer acidity
Highly motile
Survives at acidic ph (2-3)
Lab diagnosis= Urea breath test, Upper gastrointestinal endoscopy, gram
stain
.
Clostridium:
Sporing bacteria
Source = soil and GIT of humans and animals
Cause= gas gangrene,tetanus, botulism, and PMC
Clostridia= gram +ve, large, rod-shaped bacteria, anaerobe, all form
endospores, grow under aerobic conditions
Lec 8
RESP SYSTEM
Infections of the upper respiratory system are most common
Lower respiratory system is usually sterile because of the mucociliary
escalator action.
Normal respiratory tract flora:
i. Staphylococcus
ii. Corynebacterium
iii. Moraxella
iv. Hemophilus
v. Bacteroids
vi. Streptococcus
S.pneumonie and S.pyogenes can cause Laryngitis or Tonsilitis
Strep throat:
Cause = erthrogenic toxin( produced by S.pyogenes)
Drug of choice = penicillin
Bordetella Pertussis
Classification of pneumonia:
1. CAP (Community acquired pneumonia) caused by = S.pneumoniae &
H.influenzae
2. HAP(Hospital Nosocomial infection) caused by = Klebsiella sp., E.coli,
Pseudomonas and MRSA
3. Chronic pneumonia: caused by = M.TB, Nocardia, Actinomyces, Cryptococcus
neoformans and Aspergillus
4. Atypical pneumonia: caused by = Mycoplasma, Chalmydia and Coxiella
burnetti
Tuberuculosis
Leading killer of HIV positive people
Cause: M. tuberculosis, M.bovis and M.avium
M.TB = transmitted via aerosol, non motile rod-shaped bacterium,
obligate aerobe has Mycolic acids, incubation period = 1 -3 weeks
Test +ve reaction to tuberculin test
( Lec 9)
NERVOUS SYSTEM
Encephalitis = inflammation of brain (eg. Mami)
Meningioencephalitis = inflammation of both brain and meninges
Myelitis = inflammation of SC
Bacterial
meningitis(most
dangerous)
Viral meningitis(called
aseptic meningitis)
Usually mild. Clears up
Fungal meningitis
NEISSERIA
MENINGITIDUS
HEMOPHILUS
INFLUENZAE
S.PNEUMONIAE
MUMPS
INFLUENZA
ARBOVIRUS
HERPES
NEISSERIA MENINGITIDIS:
Coffee-bean-shaped cocci
Normally found in :oro-and naso-pharynx, and vagina
concentration of 510%CO2 encourages proliferation
cultures requires medium containing blood.
Highly contagious
Has polysaccharide capsule
frequently pleomorphic
Gram-negative
Humans are the only pathogen reservoir
Probable mode of spread to the meninges is through the blood.
13 meningococcal serogroups have been identified
Group A meningococcus accounts for an estimated 8085% of all cases
in the meningitis belt.
N.meningitidis is a major cause of epidemic
Meningococci are parasites of the nasopharynx
Transmission : through droplets of respiratory or throat secretions from
carriers
live in leukocytes in CSF
The symptoms are due to endotoxin
headache, fever, neck stiffness, and severe malaise, rash
disease occurs most often in young children < 2 y of age.
Sporadic outbreaks among young adults.
Diagnosis based on isolation and identification of the organisms from
either the blood or the CSF.
CSF sample :turbid due to large no. of pus ells
Serology (detection of antigen by Latex agglutination test
Meningococci are capsulate
Culture: N. meningitidis :Cultivation requires (blood) chocolate agar and
incubation in 5% to 10% carbon dioxide atmosphere
Selective media Modified Thayer-Marten (MTM) media containing
antibiotics
Biochemical tests : Oxidase +, sugar fermentation test.
Serology : Detection polysaccharide capsular antigen
Treatment : Penicillin G.
Prevention : immunization can be achieved with a vaccine made from
the purified capsule polysaccharides A, C, Y, and W-135
(tetravalent).MCV4
NB. There is no serogroup B. Conjugate vaccine
S. PNEUMONIE
LISTERIOSIS
Listeria monocytogenes:
Gram-positive rods
Peritrichous flagellation
Motile at 20 C
Can be cultured aerobically on blood agar.
Reproduce in phagocytes
Acquired by ingestion of contaminated food
May be asymptomatic in healthy adults
On isolated culture confused with diptheroids
Cultures will take 1-2 days for growth
Causes meningitis in newborns, immunosuppressed, pregnant women, and
cancer patients.
Can cross placenta and cause spontaneous abortion and stillbirth
Diagnosis: blood or spinal fluid test
TETANUS
Appearance under microscope :drum-stick
Clostridium tetani : Gram-positive bacilli, endospore-forming,
obligate anaerobe
Motile, clear zone of hemolysis, Robertson cooked media
Puncture wounds (such as those caused by rusty nails, splinters,
or insect bites.)
clinical manifestations do not result directly from the invasive
infection, but are rather caused by a strong neurotoxin =
TETANOSPASMIN (blocks inhibition pathway)
characteristic motor spasm of tetanus
Germinates under anaerobic conditions
Clinical features
BOTULISM
Clostridium botulinum :Gram-positive, Endospore-forming, Obligate
anaerobe, ubiquitous in soil and H2O
Intoxication (ingestion of botulinum toxin): Botulinum Toxin: Most Potent
Toxin on Earth
7 different Neurotoxins
Mechanism of action: Irreversible inhibition of ACh acetylcholine release
from motor neuron .
Resulting in flaccid paralysis of the musculature
3- Forms of Botulism
1. Food-borne botulism: Intoxication not infection, Due to improper
canning procedures
2. Wound botulism symptoms start ~ 4 days after wound infection
3. Infant botulism: Due to ingestion of endospores C. botulinum in
food (e.g., honey).
Diagnosis: Based on toxin detection by means of the mouse
neutralization test.
Therapy : Urgent administration of a polyvalent antitoxin.(A, B &E)
Prevention: Proper canning
Poliomyelitis
Rabies
Viral meningitis
Viral encephalitis
ARBOVIRAL ENCEPHALITIS
PYELONEPHRITIS
LEPTOSPIROSIS
Causative agent: Leptospira interrogans
Is a Gram negative, obligate aerobe spirochete, flagella
Reservoir: Dogs and rats
Transmission: Skin/mucosal contact from urine-contaminated water
Symptoms: Headaches, muscular aches, fever, kidney failure a possible
complication
Diagnosis: Serological test
Treatment: Doxycycline
o Arthritis
o Ophthalmia neonatorum
NB. N.meningitidus and N.gonnorhea are BOTH coffee- bean shaped !!!
SPIROCHAETES:
1. Treponema,
2. Borrelia,
Syphilis
Lyme disease
3. Leptospira,
Weils
N. MENGITIDUS
Fermentatio
Ferments glucose and
n test
maltose
Microscopic
Encapsulated
features
Transmission
Respiratory or oral
secretions
N. GONNORHEA
Ferments glucose but
NOT maltose
Un encapsulated
Sexually or vertical
Usually found
intracellularly in
LEUKOCYTES
Syphilis
Contagious, sexually transmitted disease
Spirochete Treponema pallidum = Microaerophilic.
Not been cultivated on artificial media in the lab.
Identification: darkfield microscopy or fluorescent antibody techniques
Congenitally transmitted syphilis ( Vertical: Mother to child), pass
through the placenta.
Invades mucosa or through skin breaks
Types:
Primary Syphilis
Forms at site of inoculation
Secondary Syphilis
Spread to local lymph nodes & then to the blood stream
Signs and Symptoms:
Usually occurs 4-8 weeks after primary chancre
Skin manifestations, Rash (75-90%),
Early on face, shoulders, flanks, palms and soles, anal or genital areas
Patchy alopecia or hair loss
The rash and ulcer will disappear in (3-6) months
Early Latent
Can involve of many body organs (2o and latent)
Late latent = Late Syphilis (tertiary)
Late disease (tertiary) infection/inflammation of the blood vessels in the central nervous
system and cardiovascular systems
involuted, a latent period occurs
few months or a lifetime
No clinical manifestations
Is positive serologic tests.
GENITAL WARTS
Human papillomaviruses= characterized by warts in genital area
Cause : HPV 16 causes cervical cancer and cancer of the penis
Prevention: Vaccination against HPV strains
CANDIDIASIS:
Causative agent: Candida albicans Grows on mucosa of mouth, intestinal
tract, and genitourinary tract that grows on pH: <4
Vulvovaginal candidiasis, yeasty discharge
Diagnosis: microscopic and culture
Treatment: Clotrimazole; fluconazole
LEC 10
BACILLUS ANTHRACIS
Gram-positive, endospore-forming, rods, nonmotile, nonhemolytic
Bamboo stick appearance
Referred to as medusa head appearance (culture
Aerobic and catalase positive
Primary habitat is soil.
Spike-like projections at the colony edge, ground glass texture exhibited
by the colonies
The disease strike primarily grazing animals, such as cattle and sheep.
Zoonotic disease of grazing animals
Not generally considered to be contagious
2 SPECIES OF MEDICAL IMPORTANCE:
1. Bacillus anthracis
2. Bacillus cereus
Occupational hazard
depends on the death of its host for formation of spores, which are the main
transmissible source of the disease.
It enters through: Cuts in the skin, Respiratory tract, Mouth.
Infection by B. anthracis are initiated by endospore
In the body taken by macrophages
Virulence factors are:
Two exotoxins
third toxic component, a cell receptor-binding protein called the protective
antigen, that binds the toxins to target cells and permit their entry.
1. The edema toxin
o Cause local edema, interfere with phagocytosis.
2. The lethal toxin
Specifically targets and kill microphages
capsule of B. anthracis is very unusual it has (amino acids instead of
polysaccharide) thats one of the major virulence factors
When enter the blood, proliferate without inhibition,until it kills the
macrophages
3 types of anthrax:
1- CUTANEOUS ANTHRAX
Over 90%
Entry through minor skin lesion
incubation period of 1-7 days
Symptoms: papule ---- vesicular ---- pustule (malignant) ---- depressed black
eschar + Edema
In most cases the pathogen does not enter the bloodstream
2- GASTROINTESTINAL ANTHRAX
BACILLUS CEREUS
INFECTIVE ENDOCARDITIS:
5.
6.
7.
8.
Oesophageal dilatation
Biliary tract surgery
Cardiac surgery
Injection drug use
Valve type
Nature
SUBACUTE IE
Normal valve
Previously abnormal
valves
Indolent nature,
local
Months - years
Develops to
metastatic infection
Days - weeks
Duration
Toxicity
Highly toxic
Causative agent
Fatality
untreatment
ACUTE IE
S.aureus
of
Quick
Mild toxicity
S. viridans or
enterococcus
Slow
Aetiological Agents
1. Streptococci
a. Native valves (not prosthetic)
b. Previously damaged
2. Enterococci
i. E. faecalis, E. faecium
ii. Associated with GU/GI tract
3. Staphylococci
viridans streptococci as the most common cause of
infective endocarditis
S. aureus
Acute endocarditis
S. epidermidis (Coagulase-negative staphylococci)
Prosthetic valve endocarditis
4. Gram negative organisms
P. aeruginosa most common
HACEK - slow growing, fastidious organisms
Haemophilus sp.
Actinobacillus
Cardiobacterium
Eikenella
5. Fungi
Candida species, Aspergillus species
Clinical features:
Laboratory features:
1. Fever
1. Anemia
2. Murmurs
3. ESR elevated,
4. Microscopic hematuria
5. Splenomegaly
6. Blood cultures.
5. Bacteremia.
8.
Echocardiography
OPHTHALMIA NEONATORUM
The etiology is herpes simplex type 1 (HSV-1) that invades the central nervous
system
Trifluridine is an effective treatment for herpes keratitis.
Acanthamoeba
Protozoa (amoeba), transmitted via water, can cause a serious form of keratitis.
Damage is often severe (corneal transplant), or even removal of the eye.