Micro Bio – Microbiology Test Answers – Flashcards

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·         study of cells or entities called microorganisms that

o   Carry out one or more life processes

o   Usually too small to be seen by naked eye

Life processes


·         Living cells carry out all 4

o   Replicate

o   Grow

o   Metabolize

o   Respond to environment



·         Microorganisms AKA microbes




o   Bacteria

o   Archaea

o   Protozoa

o   Algae

o   Helminths

o   Viruses




·         Bacteria




o   Unicellular

o   Prokaryotic

o   Many shapes and sizes but usually

§  0.2-3um in diameter

§  0.5-10um in length

o   Peptidoglycan cell walls (some don’t)




·         Archaea



o   Unicellular

o   Prokaryotes

o   Similar to bacteria in shape and size

o   Different than bacteria

§  Different cell wall (not peptidoglycan)

§  Different ribosomal structure

o   Two groups

§  Methanogens – Obligate anaerobes that produce methane gas

§  Extremophiles – Live under extreme conditions of temp, pH, or salinity




·         Fungi




o   Unicellular or Multicellular

o   Eukaryotes

o   Cell walls of chitin or cellulose

o   Plant-like absorptive metabolism

o   Require organic source of carbon – No photosynthesis

o   Mushrooms, yeasts, mold




·         Protozoa




o   Unicellular

o   Eukaryotes

o   Lack cell walls

o   Require organic source of carbon – No photosynthesis

o   Above was historical definition – with addition of some algae reclassified, no longer holds




·         Algae




o   Unicellular or Multicellular

o   Photosynthesis

o   Cell walls of polysaccharides and other substances (cellulose, agar, silica, calcium carbonate)

o   Eg. Spirogyra and Diatoms



·         Helminths




o   Multicellular

o   Eukaryotes

o   Lack cell walls

o   Invertebrate worms studied because

§  Some are parasites of humans and animals

§  Microscopic forms in life cycle

o   Examples

§  Wucheria bancrofti elephantiasis

§  Schistosoma mansoni schistosomiasis

§  Liver fluke

§  Tapeworm

§  Guinea worm

§  Ascaris roundworms





o   Small acellular particles that can’t be seen by light microscopy

o   Composition

§  Nucleic acid

§  Protein coat

§  Sometimes membrane coat

o   Variety of shapes and sizes

§  0.02 - .25 um in diameter

§  1um in length

o   Obligate intracellular parasites




·         Classification and Identification



o   Diverse group w/millions of species

o   Genus

§  Noun

§  Capitalized

o   Species

§  Adjective or noun

§  Lowercase

o   Italics or underlined

o   Genus – closely related species

o   Species – organisms that can interbreed

§  Doesn’t apply to prokaryotes due to asexual repro

o   Prokaryotic species

§  Closely related cell strains

§  Prokaryotic cell strain – Cells derived from single cell

o   Ordered taxonomic hierarchy

o   Bergey’s Manual of Systematic Bacteriology 2nd Edition – Authoritative guide           


Microbes Effect on World and Humans




o   Essential for ecological balance

§  Recycle bound vital elements to unbound forms

·         Carbon

·         Nitrogen

·         Oxygen

·         Phosphorous

·         Sulfur

§  Photosynthetic microbes produce most 0­2

§  Plankton – marine microbes

·         Convert C02 into marine animal food

·         Base of ocean food chain

o   Benefit human lives

§  Normal body flora

·         Microbial antagonism – outcompete pathogenic microbes for attachment space and nutrients

·         Supply essential vitamins

§  Produce foods and products

·         Cheese, bread, beer, wine, chocolate, pickles

·         Antibiotics, insulin, HGH, steroids

·         Alcohol, acetone, other chemicals

§  Clean sewage and pollution

·         Remove organic matter and toxic pollutants from waste in treatment plants

·         Biosensors to detect toxic substances and pathogens in environment

·         Detoxify dumps and spill sites

§  Agriculture

·         Produce nitrogen fertilizer

·         Kill caterpillar pests

o   Adverse effects

§  Infection diseases

§  Food spoilage

§  Weathering and breakdown of materials



Discovery of Microbes



o   1673 – Antoni van Leeuwenhoek made first microscope able to see microbes

§  300x magnification

§  Called Fungi, Algae, Protozoa, and Bacteria animalcules

§  Hooke’s earlier microscope (1665) could not see microscope



Life prior to discovery of microbes




o   Unknown before 1673

o   Medical and economic significance known less than 150 years

o   Uncontrollable food spoilage

o   Entire families would get sick and die from infectious diseases

o   Bubonic plague (black death) would periodically appear



Black Plague




o   541 – 767 AD

§  40-100 million deaths

o   1347-1352 AD

§  25 million deaths in Europe (1/4 of pop)

o   1352 – 1771 AD

§  50 million deaths

o   People had no clue of cause

o   Appears in art and religious interpretations

o   Caused by Yersinia pestis

§  Endemic of wild rodents

§  Transmitted to humans by rat fleas

o   Still occurs but we manage spread

o   Contributing factors in history

§  Ignorance

§  Poor sanitation

§  Religious superstition

·         Thought to be punishment from God

·         Foul humors, Poisoned water or witch’s spells blamed

·         Perfumed sachets worn

·         Witches and suspected water poisoners driven out or killed

·         Cats slaughtered – contributed to rat infestation

·         “Ring around rosies” expresses futility of medieval remedies


Spontaneous generation



o   Proposed by Aristotle in 340 BC – believed for >2000 yrs

o   1668 – Francesco Redi

§  Disproved for higher life forms using meat in open, corked, and gauze covered jars

o   1745 – John Needham

§  Resurrected theory for microorganisms using boiled beef infusion in jars with guaze and corks (both had growth)

o   1799 – Lazzaro Spallanzani

§  Tried to refute Needham using sealed jars with broth

§  Boiled after sealing, no growth till broken

§  Critics say he destroyed “vital” force, had to be broken

o   1861 – Louis Pasteur

§  Biogenesis – Living cells only from preexisting living cells, this theory disproved it

§  Used boiled infusions with curvy spouts – didn’t develop microbes even with open air unless sterile infusion comes in contact with dust that is settled



Golden Age of Microbiology – 1860-1910




o   Methods for culturing and studying individual species

o   Role of microbes in fermentation, disease, spoilage

o   Preventive methods for infectious diseases

o   Scientific method established



Louis Pasteur



Father of Microbiology

o   1861 – Louis Pasteur

§  Biogenesis – Living cells only from preexisting living cells

§  Used boiled infusions with curvy spouts – didn’t develop microbes even with open air unless sterile infusion comes in contact with dust that is settled

o   Showed yeast responsible for wine fermentation and bacteria for wine spoilage to acids

o   Pasteurization – heating liquid foods to 63 degrees C to kill bacteria

o   Proposed germ theory of disease in 1857 but Robert Koch proved it in 1876

o   Disproved spontaneous generation

o   Developed rabies and chicken cholera vaccines from attenuated forms of microbes



Robert Koch



Father of Laboratory Microbiology


o   1876 – Proved microbes cause diseases in animals

§  Took Bacillus anthracis from anthrax-infected cattle and showed it was transmitted to other cattle

§  Developed methods for growing and isolating bacteria on solid media in the lab

o   1882 – showed Mycobacterium tuberculosis caused TB

o   Discovered delayed hypersensitivity

o   Koch’s Postulates – link microbe to disease

§  Agent must be found in every disease case and be absent from healthy hosts

§  Agent must be isolated and grown outside host

§  When agent introduced to healthy subject, must develop disease

§  Agent must be isolated from now infected host

o   Lab Techniques

§  Growing and isolating microbes on solid media

§  Simple staining

§  First photomicrograph of bacteria and bacteria in diseased tissue

§  Techniques to estimate bacteria number

§  Petri dishes

§  Steam sterilization of media

§  Aseptic techniques


§  Distinguishing bacteria from each other


Edward Jenner


 (1798) Invented vaccination

   Gave humans cowpox to protect against smallpox

Ignaz Semmelweis


·         (1848) – Hand disinfection

o   Reduced death rate of women giving childbirth by people using chlorinated lime water


Florence Nightengale


·         (1854) – Infection control

o   Introduced strict cleanliness standards at army hospitals reducing death and disease rate of wounded


John Snow


·         (1854) – Epidemiology

o   Stopped cholera epidemic by mapping infections and shutting down contaminated well


Joseph Lister


·         (1860s) – Aseptic Surgery

o   Disinfected with phenol and reduced infection and death rates


Emil von Behring


·         (1890) – Antibodies

o   Inoculated animals with diptheria toxin and antibodies protected against diptheria


Elie Metchnikoff
(1900) – Phagocytosis and cellular immunity
Paul Ehrlich (1900)


·         Humoral immunity and Father of Chemotherapy

o   Salvarsan – first drug to treat infectious disease (syphilis)

o   Renounced by religious zealots


Alexander Fleming


·         (1928) – Penicillin

o   Not used to treat until 1942




·         Modern Microbiology uses




o   Biochemistry

o   Microbial Genetics

o   Molecular Biology

o   Recombinant DNA Technology

o   Gene Therapy

o   Environmental Microbiology

o   Serology

o   Immunology

o   Chemotherapy



·         Infectious diseases of Modern Times




o   1900 - Half of deaths caused by infectious diseases

o   1997 - 1/16 deaths caused by infectious diseases

o   Reduction due to

§  Vaccines

§  Antibiotics

§  Sanitation

o   1998 – 45% of deaths in low income countries infectious diseases

o   1998 – 5% of deaths in high income countries infectious diseases

o   1998 – Six biggest infectious killers

§  Respiratory infection


§  Diarrheal

§  TB

§  Malaria

§  Measles

o   Low income countries have 9x disease rate

§  Poor sanitation allow diseases to flourish

§  Lack resources and medicine to treat diseases

o   Why diseases still kill in high income countries

§  No vaccines or treatments for some (hep C and HIV)

§  Hosts elderly and have compromised immune systems

§  New diseases reemerge and previously controlled ones reemerge

§  Antibiotics can cause resistant strains


·         Treatment and Prevention


o   Treat

§  Isolate and identify agent

§  Test for sensitivity to antibiotics

§  Treat patient with most effective antibiotic

o   Prevented

§  Vaccination

§  Sanitation and infection control

§  Med/Dental precautions between doctor and patient


·         Diseases that can be transmitted in Healthcare facilities



o   Disease / transmission / incubation /survival


o   TB / Respiratory droplets and sputem / Months or years /Months


o   Group A Strep / Saliva and open lesions / Days / Hours-days

o   Syphilis / Open lesions / Weeks / Seconds – minutes

o   Flu or Colds / Respiratory Droplets / Days / Hours

o   Hep B / Saliva, blood, body secretions / Months / Months

o   AIDS / Blood, semen, body secretions / Years / Days – hours

o   Herpes / Saliva, open lesions / Weeks / Minutes



·         1991 Time ran article “Should you Worry about Getting AIDS from your Dentist




o   Dr. David Acer had AIDS and died along with 6 patients of it

o   Never proven but Kimberly Bergalis got a lot of publicity for being teenage patient

o   Dr. Feldman – Pitt dentist died of AIDS, didn’t transmit to patients

o   Acer only known case with possibility of transmission from healthcare worker to patient

o   Many from patient to healthcare professionals from needlesticks

1. Is a family of small, nonmotile, oxidase-positive, facultatively anaerobic, gram-negative rods.
2. They have *fastidious growth requirements.*
A. They require heme or cytochromes for growth.
B. They are usually grown on chocolate agar (agar that
contains heated blood).
3. There are two medically important genera.
A. Pasteurella.
B. Haemophilus.
1. Pasteurella are normal flora in the
nasopharyngeal & oral cavities of
animals, including cats and dogs.
2. P. multocida is the major
pathogen for humans.
A. Humans become infected primarily
by animal bites, but can also be
infected by scratches or inhalation
of aerosols from animals.
B. Infection is characterized by local
inflammation and swelling of lymph
nodes at the site of infection.
3. Diagnosis.
A. Is by culture of clinical specimens on microbial
media, followed by identification of the isolated
bacterial colonies.
B. Biochemical or serological tests can be used to
identify Pasteurella species.
C. Pasteurella are non-motile gram-negative
coccobacilli that have a bipolar appearance in
stained smears.
4. Antibiotics are used to treat Pasteurella infections.
1. Is a genus of small gram-negative pleomorphic
rods that require *heme and NAD+ for growth.*
A. They are usually grown on chocolate agar.
B. Haemophilus means blood-loving.
2. Haemophilus species colonize the mucous
membranes of humans and some animals.
3. 4 species are pathogenic for humans.
A. H. influenzae.
B. H. ducreyi.
C. H. aphrophilus.
D. H. aegyptius.
Haemophilus influenzae
1. Causes a variety of human diseases including
meningitis, otitis media, epiglottitis, pneumonia
and sinusitis.
A. It causes disease primarily in *children less than 4
years of age* and in the *elderly.*
B. Most children develop natural immunity (antibodies) to H. influenzae by 4 years of age.
C. It is the *2nd leading cause of community-acquired pneumonia.*
2. Epidemiology.
A. H. influenzae is commonly present in the throat of
healthy individuals.
B. It is transmitted to new hosts by infected respiratory
3. Major virulence features.
A. Pathogenic strains produce an *anti-phagocytic* polysaccharide *capsule* that resists phagocytosis.
1) There are 6 capsular types.
2) H. influenzae *capsular type b (Hib) causes most H.
influenzae infections.*
4. Diagnosis.
A. Is by culture of clinical specimens on microbial
media, followed by identification of the isolated
bacterial colonies using biochemical or serological
5. Treatment is usually with cephalosporin.
A. Hib meningitis and epiglottitis are *life-threatening
and must be treated promptly with antibiotics to prevent death*
H. influenzae Type B (Hib): Prevention
1. An effective Hib
vaccine for infants
was introduced in
A. Pre-Hib vaccine,
Hib was the #1
cause of meningitis
in children under 4 years of age,
causing about
20,000 cases/year.
B. Hib vaccination of
infants has reduced
the incidence of Hib
meningitis in
children under 4 to
about 450 cases/year
Haemophilus ducreyi
1. Causes a *sexually
transmitted disease*
called *chancroid* that is
characterized by the
formation of an *ulcer at
the site of infection* on
the genitals, mouth or
2. Chancroid is painful in
men, but often asymptomatic in women.
A. The incidence of chancroid in the U.S. is less than 100
cases/year, but it is a common STD in Africa & Asia.
Other Haemophilus species
1. H. aphrophilus.
A. Is a member of the normal
flora in the mouth and
a rare cause of endocarditis.
2. H. aegyptius.
A. Causes a contagious
conjunctivitis called pink-eye, which is common in
school children in the U.S.
B. Responds to tetracycline treatment.
C. A brazilian strain of H. aegyptius causes severe
conjunctivitis and a life-threatening hemorrhagic fever.
3. Other Haemophilus species can cause opportunistic infections.
Truly Pathogenic Aerobic Gram-negative Rods
1. Are a diverse group of aerobic, gram-negative
rods that cause disease in humans and animals,
and have fastidious growth requirements.
2. This group includes species from the following
A. Bartonella;
B. Brucella;
C. Bordetella;
D. Francisella;
E. Legionella; and,
F. Coxiella.
1. Is a genus of pleomorphic gram-negative
bacilli commonly found in the *flora of animals* that cause disease only in humans.
2. 3 species are pathogenic for humans.
A. Bartonella bacilliformis.
B. Bartonella quintana.
C. Bartonella henselae.
3. Bartonella are *facultative intracellular parasites*
that grow slowly and are difficult to culture.
4. Bartonella infections are treated with
erythromycin and gentamicin.
Bartonella bacilliformis
1. Causes bartonellosis (Oroya fever), a life-
threatening infection of red blood cells and
endothelial cells.
A. Bartonellosis is initially characterized by fever,
anemia, headache, muscle and joint pain.
B. Vascular skin lesions occur 2-8 weeks later and
continue to occur in successive crops for 1 year.
2. Is transmitted to humans by blooding-sucking
sand flies of the genus Phlebotomus which are
found only in Peru, Columbia and Ecuador.
Bartonella henselae
1. Is commonly found in the *oral flora of cats.*
2. It causes *cat scratch disease*, a common
infection caused by cat scratches or bites.
A. Cat scratch disease is characterized by formation of
a raised papule at the infection site, fever and
swollen lymph nodes.
B. The disease is usually self limiting in healthy hosts
and subsides after a few weeks or months.
C. It can also be transmitted to humans by flea bites.
3. B. henselae also causes *bacillary angiomatosis* and *peliosis hepatis* in *immunodeficient hosts.*
These diseases are discussed with B. quintana.
Bartonella quintana
1. Causes *trench fever*, a disease characterized by
fever, headache, muscle, joint & leg pain usually
lasting about 5 days, but sometimes for years.
A. It is spread to new hosts by *human body lice* and *thrives
in unsanitary conditions.*
B. It was a common disease of soldiers in World War I.
C. The natural reservoir for the organism other than lice
and humans is unknown.
2. B. quintana and B. henselae can both cause *bacillary angiomatosis* and *peliosis hepatis* in *immunodeficient hosts*. Both are common diseases
in AIDS patients.
A. Peliosis hepatis is characterized by the *formation of
blood filled cavities in the liver and spleen.*
Bacillary Angiomatosis in AIDS Patients
B. quintana and B. henselae can both cause bacillary angiomatosis
1. Is characterized by fever, scaly skin and the formation of
*inflamed, raised, highly vascularized skin lesions that bleed easily*(Bartonella infect endothelial cells).
2. The lesions can occur all over the body and in every
organ, especially the liver and spleen (peliosis hepatis).
1. A genus of small, nonmotile, aerobic, gram-negative
rods that are *facultative intracellular parasites.*
2. Brucella *infect the mammary glands and placenta of
animals,* causing abortions, runting and sterility.
3. They cause brucellosis (undulant fever) in humans
A. Brucellosis can be asymptomatic, mild, or severe
depending upon the infecting strain.
B. Illness is characterized by *intracellular infection* of
macrophages, fluctuating fever, fatigue and weight loss
C. Humans become infected by *ingesting unpasteurized contaminated dairy products* or through *contact with infected animal parts.*
D. It is no longer common in the U.S. (100 cases/year).
1. Is a genus of small, aerobic, nonmotile, gram-
negative rods.
2. B. pertussis is the most important pathogen. It
causes *pertussis* (also called *whooping cough)*.
A. Pertussis occurs naturally in *young children* in
unimmunized populations; many adults are carriers.
B. B. pertussis produces many virulence factors that allow it
to cause disease in hosts. The most important are:
1) *Pertussis toxin:* It ADP-ribosylates proteins, raises
cyclic AMP levels in cells & causes mucus secretion.
2) *Filamentous hemagglutinin*, an adhesin.
3) Endotoxin, dermonecrotic toxin and tracheal
cytotoxin; the latter kills ciliated epithelial cells.
4) *Adenylate cyclase:* It raises cAMP levels in cells.
Bordetella pertussis
1. Is transmitted to new hosts by
inhalation of respiratory
droplets from infected hosts.
2. B. pertussis adheres to and
colonizes ciliated epithelial
cells in the lower respiratory
tract (see figure) and kills them.
A. Mucus accumulates in the
lower respiratory tract, causing
the host to try to expel it by
coughing violently.
3. Whooping cough occurs in 4 stages:
1incubation-no symptoms, 2 catarrhal-rhinorrhea, sneezing, malaise, fever, 3-paroxysmal-repetivie cough, with whoops, vomiting, exhaustion, 4-convalescent-diminishing cough, possible 2ndry complications

1. Diagnosis of pertussis is usually done by symptoms.
2. Treatment is primarily by supportive care.
A. Antibacterial drugs have little effect on the course of the
disease, which takes 4 or 5 weeks to resolve.
3. Prevention of pertussis is by immunization with the *DaPT vaccine.*
4. U.S. pertussis incidence has increased significantly in
recent years (10,000 - 26,000 cases per year) due to:
A. A refusal by some parents to have their children
immunized; and,
B. Increased occurrence and diagnosis of pertussis in adults.
The current acellular pertussis vaccine is not as effective
as the previous vaccine. CDC now recommends a pertussis booster shot for adults
Francisella tularensis
1. Is a small non-motile, aerobic, gram-negative
coccobacillus that causes the highly infectious
zoonotic disease *tularemia*.
Virulence Properties of F. tularensis
1. F.t. is one of the most infectious microbes known,
but its virulence factors are not well understood.
A. It *passes through microscopic breaks in skin and
mucous membranes*; the *infectious dose is 10 cells.*
B. It produces an *antiphagocytic capsule*, but also
*multiplies inside host cells,* especially macrophages,
which makes it a *facultative intracellular pathogen.*
2. Its endotoxin causes inflammation and hemorrhagic necrosis.
Epidemiology of Tularemia
cause by Francisella tularensis
1. Tularemia occurs all over the world. It is caused by
F. tularensis,* a facultative intracellular parasite that
infects more than 100 animals and amoebas.*
A. Tularemia is most commonly *associated with rabbits*
in whom it is often fatal.
B. F. tularensis also commonly infects wood ticks. It is
transmitted to new tick generations by *transovarian passage* into tick eggs, so tick larvae are born with it.
C. There are 100-200 cases of tularemia/year in the US.
2. F. tularensis has two biovars (strains).
A. Type A is found only in *North America,* is lethal for
rabbits and *causes severe illness in humans.*
B. *Type B is found in the rest of the world,* is not lethal
for rabbits and *causes mild illness in humans.*
3. Tularemia can be transmitted to humans by:
A. The *bite of an infected arthropod,* such as ticks and
deer flies. This is the most common route of infection.
B. *Contact with an infected animal,* especially rabbits.
C. *Inhalation of aerosols* from an infected animal or
D. *Ingestion of contaminated food (meat) or water.*
4. Tularemia occurs in 3 clinical forms depending
upon the route of infection.
A. *Ulceroglandular* tularemia.
B. *Pneumonic* tularemia
C. *Typhoidal* tularemia.
Pathogenesis of Ulceroglandular Tularemia
1. Ulceroglandular tularemia
is caused by contact with a
F. tularensis infected
animal or biting arthropod.
2. In 2-6 days an *ulcerating
papule* forms at the site
where F. tularensis
entered the body, as
shown in the figure.
3. F. tularensis *spreads to
the lymph nodes* that drain
the tissue, where it is
*ingested by macrophages*
4. Macrophages are *unable to kill F. tularensis*. It
*multiplies inside them* and eventually lyses them,
spreading the infection to other macrophages.
5. The lymph node enlarges, undergoes hemorrhagic
necrosis, ulcerates and forms a draining sinus.
6. F. tularensis *spreads to other tissues and organs* via the
lymphatics and blood, and forms granulomas in them.
7. Ulceroglandular tularemia can be mild, chronic or life-
threatening, depending upon the infecting strain of F.
tularensis, the site of infection and the immune status
of the host.
A. The signs and symptoms of ulceroglandular tularemia
are *headache, fever, night sweats, fatigue, and weight
loss* (symptoms common to all chronic infections).
Pathogenesis of Pneumonic Tularemia
1. Pneumonic tularemia is a *rapidly developing life-threatening infection* caused by *inhalation of F. tularensis into the lungs*.
A. There is a sudden onset of fever, chills and muscle
aches 2-4 days after inhaling F. tularensis.
B. Within 24 hours the host develops chest pain,
dyspnea and cyanosis. Antibiotic treatment must
started at this stage or the host will die within 18
hours from massive pneumonia and/or septic shock.
2. Pneumonic tularemia is *highly contagious* &
can *spread person to person via respiratory droplets*. It has a *30% mortality rate* and can be
used as *biological warfare weapon.*
Pathogenesis of Typhoidal Tularemia
1. Typhoidal tularemia is caused by *ingesting F. tularensis*.
2. Its symptoms are similar to typhoid fever, and
include headache, high fever, prostration,abdominal pain and diarrhea.
Diagnosis of Tularemia
1. Tularemia is difficult to diagnose because it is
uncommon in the U.S., and its symptoms mimic
those of several other diseases.
2. It is diagnosed by detecting F. tularensis in
infected tissue by fluorescent antibody staining or
by determining antibody titers to F. tularensis.
3. F. tularensis is dangerous to culture and should
be grown only in special facilities designed for
handling highly hazardous pathogens.
4. F. tularensis is fastidious and is grown on a
special cystine-glucose-blood agar medium
Treatment and Prevention of Tularemia
1. Tularemia is treated with ciprofloxacin (500 mg
po BID) or doxycycline (100 mg BID) for 14
days. Streptomycin & gentamicin are also used.
2. Tularemia can be difficult to treat because of
the intracellular location of the microbes inside
macrophages. Relapses are common.
3. Prevention of tularemia is done by avoiding the
major reservoirs of the bacteria in nature.
4. An experimental vaccine is available for
individuals at risk for contracting tularemia.
5. Prophylactic antibiotics are given to individuals
exposed to a host with pneumonic tularemia.
1. Are aerobic, slender, pleomorphic, gram-negative
rods that are commonly found in water.
A. They are *facultative intracellular parasites* of protozoa.
2. The most important Legionella pathogen is
*Legionella pneumophila* which causes 2 distinct
disease syndromes in humans.
A. *Legionnaires’ disease*, which is a severe pneumonia
that has a 20% mortality rate.
B. *Pontiac fever*, which is a mild flu-like illness.
3. Humans usually acquire L. pneumophila by
inhaling it in *aerosols from water sources,
especially air conditioning cooling towers.*
4. Legionnaires disease occurs primarily in males
who have an underlying lung condition, are heavy
smokers, alcohol abusers, or a chronic lung illness.
5. Immunocompromised hosts are also susceptible to
developing Legionnaires’ disease.
6. There are about 3,000 cases of Legionnaires’
disease per year in the U.S.
7. Legionella cannot be eradicated from the
environment because they are ubiquitous in water.
A. Reducing their number in problem sites such as cooling
towers, showers and faucets by sanitation and use of
disinfectants is a successful control measure.
Coxiella burnetii
1. Is a small aerobic, gram-negative rod that causes
a *zoonosis of ticks, cattle and other animals* called *Q fever* that can be transmitted to humans.
2. C. burnetii forms an unusual *endospore-like infective body* that enables it to *survive harsh
environmental conditions.*
3. It is an *obligate intracellular parasite* that multiplies within phagolysosomes.
4. It was originally thought to be a virus due to its
small size and parasitic nature.
5. *Farm animals* (cattle) and pets are the reservoirs most often associated with human Q fever.
6. Q fever is a *pneumonia-like illness in humans* which is characterized by fever, chills, chest pain,
headache and breathing difficulty.
A. Endocarditis is sometimes a late complication that
develops years after the initial infection.
B. Infections are self-limiting in most hosts, but can
become chronic and severe.
7. Q fever occurs primarily among ranchers,
veterinarians and food handlers.
A. There are about 150 reported cases/year in the U.S.
8. Transmission usually occurs by *inhalation of the infective bodies from an infected host* (usually cattle) of from a tick bite
Opportunistic Aerobic Gram-negative Rods
1. Are a diverse group of aerobic, gram-negative rods that cause *opportunistic infections* in humans.
2. Most of these bacteria have simple growth
requirements, and are ubiquitous in soil and water.
3. Includes species from the following genera:
A. Pseudomonas;
B. Burkholderia;
C. Stenotrophomonas;
D. Alcaligenes;
E. Acinetobacter; and,
F. Moraxella.
1. Is a genus of motile, aerobic, gram-negative rods
that are *ubiquitous in soil, plants, decaying organic matter and water.*
A. They do not ferment carbohydrates, have simple
growth requirements and require only a carbon source
and moisture to grow.
B. They have a single polar flagellum, are oxidase-
positive and catalase-positive.
C. Many species produce *pigments* (green, brown, red or yellow).
2. Pseudomonas species can degrade a wide array of organic substrates, including pesticides and oil
hydrocarbons which makes them useful as
environmental decomposers and bioremediators.
3. Pseudomonads can also cause *food spoilage* and disease in plants, and they cause *opportunistic infections* in hosts with compromised defenses.
4. Most human Pseudomonas infections are caused by *Pseudomonas aeruginosa.*
Pseudomonas aeruginosa
1. Is commonly found in soil and water, and in the
intestine & on skin in about 10% of healthy hosts.
2. It produces *many virulence factors,* but causes
disease *only in compromised hosts* with weakened defenses or if *introduced into the body by a wound*
3. The virulence factors of P. aeruginosa include:
A. Production of a polysaccharide *capsule* that is *anti-phagocytic* and forms thick *biofilms;*.
1) Thick P.a. biofilms form in the lungs of cystic
fibrosis patients, making treatment difficult.
B. *Fimbriae* which allow P.a. to attach to host cells.
C. Secretion of *cytotoxins* and numerous *hydrolytic enzymes* that damage host cells and tissue.
D. A potent *endotoxin.*
E. Resistance to drying, soaps, detergents and
disinfectants, in which it often grows.
4. Once P. aeruginosa breaches the outer anatomical
barriers of a host, it can invade and grown in
virtually any tissue or organ in the body.
5. In healthy hosts, P.a. most commonly causes
opportunistic skin, external ear, urinary tract and
eye infections.
A. P. aeruginosa is a common contaminate of swimming
pools, hot tubs, sponges, washcloths and the solutions
used to store and clean contact lenses.
6. In hospital patients, P.a. most commonly causes
skin infections in burn patients, but can also
cause surgical wound infections, urinary tract
infections, lung infections and septicemia.
A. P. aeruginosa is ubiquitous in sinks, showers, toilets,
water dispensers, mops, utensils and floors, and is a
common contaminant of respirators, dialysis equipment, anesthesia equipment, etc.).
7. P.a. causes 8-10% of all nosocomial infections.
A. 2/3 of severe burn victims develop P.a. skin infections.
B. Many P.a. strains produce a
*green pigment* called
*pyocyanin* which is visible in
infected skin,
8. P.a. also commonly infects
the lungs of cystic fibrosis
patients & is a common cause
of death in these patients.
A. It forms a thick biofilm that
protects it from phagocytosis,
and stimulates the formation
of large amounts of mucus.
9. Diagnosis of P. aeruginosa as the cause of an
infection must be made carefully because its
presence in a clinical sample can be due to
contamination of the sample, as opposed to
P.a. being the cause of the infection.
10. Treatment of P. aeruginosa infections can be
difficult because P. aeruginosa is resistant to
many antibiotics, and it forms biofilms that protect it from antibiotics.
1. Is a genus of motile, aerobic, gram-negative rods
formerly classified in the genus Pseudomonas.
2. Like Pseudomonas, Burkholderia are ubiquitous in
soil, plants, decaying organic matter and water, and
can decompose a broad range of organic molecules.
A. They are useful bioremediators at contaminated
environmnetal sites.
B. They also reduce fungal infection of plant crops.
3. Several Burkholderia species cause *opportunistic infections in humans.*
4. Burkholderia cepia is a common cause of *lung infections in cystic fibrosis patients*
A. B. cepia and P. aerugenosa often co-infect cystic
fibrosis patients with devastating results and a high
mortality rate.
B. B. cepia is resistant to many antimicrobial drugs.
C. It can also cause skin and urinary tract infections.
5. Burkholderia pseudomallei causes melioidosis, a
disease that is common in the tropics.
A. It causes skin nodules at wound sites, and bronchitis
and pneumonia if inhaled.
6. burkholder malei cause glanders, a severe lifethreatening disease of horses, donkeys, and mules
A. It can also cause fatal infections in humans (skin ulcers, septiceia, and pneumonia). the disease is controlled by slaughtering infected animals
1. Is a genus of motile, aerobic, gram-negative rods
formerly classified in the genus Pseudomonas.
A. They are *commonly found in water and soil* around plant roots, and *in feces of humans and animals.*
B. They can cause *opportunistic infections in compromised hosts.*
2. Stenotrophomonas maltophilia is the most
common isolate in nosocomial infections.

A. It can contaminate disinfectants, dialysis equipment,
respiratory equipment, water dispensers and catheters
B. It forms biofilms which protect it from drugs and disinfectants, and is resistant to many antibiotics
1. Is a genus of nonfermentative, oxidase positive,
motile, gram-negative rods in the same family as
A. They are *commonly found in soil and water habitats,* and can become *established in the normal flora of humans.*
2. They can cause *opportunistic infections* (pneumonia, septicemia and meningitis).
3. The most common clinical isolate is Alcaligenes faecalis. It is commonly found in *feces, and occasionally sputum and urine.*
1. Is a genus of aerobic, nonmotile, short, plump gram-negative coccobacilli that are *widely distributed in water and soil.*
A. Acinetobacter species are commonly found in the *feces of humans and animals.*
B. They are *extremely resistant to the environment* and *survive for months on inanimate objects* (faucets,
toilets, bedding, sinks, respiratory equipment, dialysis equipment and catheters).
2. Acinetobacter causes *opportunistic nosocomial infections and also community acquired
infections* (wounds, lungs, burns, septicemia).
A. They commonly infect *traumatic injuries acquired by military personnel.*
3. The most common Acinetobacter clinical isolate in
nosocomial infections is *Acinetobacter baumanti.* It causes *3% of all healthcare-associated infections.*
A. It is resistant to many antibiotics and forms biofilms
which protect it from drugs and disinfectants.
1. Is a genus of aerobic, nonmotile, short, plump *gram-negative coccobacilli* that are commonly found in the *normal flora on the mucus membranes of humans and animals.*
2. One species, *M. catarrhalis*, (formerly Branhamella
catarrhalis) can cause *opportunistic infections* of the sinuses, bronchi, ears, and lungs
Opportunistic Anaerobic Gram-Negative Bacilli
1. Obligately anaerobic gram-negative bacilli are the
predominant flora in the large intestine, and on the
mucous membranes of the urinogenital tract. They
are important for human health because they:
A. Inhibit the growth of pathogens by microbial
antagonism, synthesize some essential vitamins that
humans cannot make, and aid in the digestion of food.
B. Do not cause disease at their normal site on the body,
but can cause *opportunistic anaerobic infections* if
introduced into other parts of the body by trauma or
2. Obligately anaerobic gram-negative bacilli are
classified into several genera & more than 50 species.
A. The most important genera that contain *opportunistic
pathogens for humans are Bacteroides and Prevotella*
1. Is a genus of anaerobic, gram-negative rods that
are commonly found in *the large intestine and upper respiratory tract of humans and animals.*
2. *Bacteroides fragilis* is the most important human Bacteroides pathogen.
A. It is the *leading cause of abdominal infections
following surgery or injury.*
B. It can also cause genital infections in women and
wound infections in skin.
1. Is a genus of anaerobic, gram-negative rods that
are commonly found in the mouth, dental plaque
and the urinary, genital & upper respiratory tracts.
2. It can cause sinus, ear and periodontal infections.
3. It can also cause gynecological infections, brain
abscesses and abdominal infections.
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