Bacteriology

Question 1

What is the size of the smallest moving object a person can see?

Answer 1

0.1 mm

Microbiology is the study of living things below 0.1mm or visible size, including viruses

Question 2

Which of these are benefits that bacteria can provide to the hosts they colonize?

Answer 2

Provide vitamins & Stimulate the immune system

Most colonization is beneficial, we are just beginning to understand how his works

Question 3

What was Anthony Leeuwenhoek ‘s nationality?

Answer 3

Dutch

From Delft, The Netherlands

Question 4

What is a “microbiome”?

Answer 4

Complete set of microbes in a niche

It is good to know this exact definition, a “metagenome” is the entire total gene sequence of a sample or that obtainable from a niche or body site

Question 5

Why is it possible to identify many important bacteria simply by shape and Gram stain type?

Answer 5

Only a few are able to cause common human infections

Question 6

A bacterial virulence factor is…

Answer 6

A specific adaptation that assist the organism to infect the host and cause disease (Reactive cell wall lipid - Flagella - Ability to grow in mucus)

Question 7

What is the difference between a bacterial species, and a strain?

Answer 7

a strain is any isolate

Question 8

What is the modern defining characteristic now used to define different types of bacteria?

Answer 8

16S ribosomal sequence

Question 9

What is microbiology?

Answer 9

The study of living things that are too small to see (& viruses)

Question 10

Bacterial in nature are often growing exponentially (T/F)

Answer 10

False

They are most often growing in biofilms and mixed populations where they are slow growing or not growing. Otherwise there would be way to many of them by tomorrow

Question 11

Where does most of the material go when you are composting garabage?

Answer 11

Into the air, as carbon dioxide

Unless anaerobic, most of your compost waste goes into the air as CO2 though the action of soil bacteria using the nutrients for energy there in aerobic respiration

Question 12

Which physiological process provides bacteria more energy as ATP than fermentation?

Answer 12

Aerobic respiration & anaerobic respiration

Question 13

Which of these is not an intracellular bacteria?
Chlamydia - Streptococcus mutans - Rickettsiae - Mycoplasma

Answer 13

Streptococcus mutans

These are the three most commonly described intracellular bacteria in traditional bacteriology textbooks and questions. There are many more though, some important pathogens (Anthrax, Salmonella and Tuberculosis bacteria, for example).

Question 14

What is the distinction in how the bacterial terms “cell wall” and “envelope” are commonly used?

Answer 14

Wall for Gram positives, envelope for Gram negatives

This is not a definition, rather just how the two terms are used by those that know about bacteria

Question 15

Why are Gram positive bacteria typically more sensitive to widely used antibiotics like beta lactams ?

Answer 15

The peptidoglycan target is on the outside of the bacteria

The target of many antibiotics is peptidoglycan synthesis, which is directly on the outside in Gram positives, but not Gram negatives.

Question 16

What is the most significant function of a capsule for a pathogenic bateria?

Answer 16

They can block phagocytosis by immune cells

Allowing some bacteria to grow directly in the blood where there are numerous phagocytes (macrophages and neutrophils). Additional concerns are that capsules can reduce diffusion of antibiotics, and increase adherence.

Question 17

Which of these features of bacterial walls and envelopes are specific to Gram negative bacteria?
(Capsules - fimbriae - flagella - teichoic acids - LPS)

Answer 17

LPS

Teichoic acids are in Gram positive walls only, while capsules flagella and fibriae may be present in both Gram positives and Gram negatives

Question 18

Why do bacteria require immense metabolism and energy?

Answer 18

To polymerize biological macromolecules from precursors

Question 19

What is homologous recombination?

Answer 19

recombination between two DNA helixes that are aligned over shared sequence (>400 bp)

If two DNA molecules have similar sequence more than about 400 base pairs, and align, enzymes can cause a ‘cross over’ or swaping of segments of sequence between then. This happens in meiosis, and in repairing damaged regions of the bacterial chromosome.

Question 20

Which one of these is NOT a bacterial genetic element?
(plasmid - transposon - circular chromosome - ribosome)

Answer 20

Ribosome

Question 21

What is unique about bacterial genes or transcription units compared to those of eukaryotes?

Answer 21

They can have more than one protein coding region

About half bacterial genes are arranged to make “polycistronic” mRNAs that have more than one protein coding region recognized by the ribosome. These were identified first, and called bacterial “operons”.

Question 22

What additional capabilities do temperate (or “lysogenic”) bacteriophages have compared to lytic phages?

Answer 22

Ability to do specialized transduction

By potentially integrating into the host chromsome temporarily, they can move specific short pieces of DNA adjacent to their attachment site with them into a new bacteria when they progress to lysis.

Question 23

What is the main reason the community acquired resistant bacterial infections are increasing?

Answer 23

Use in farming, and unregulated disposal of excess drugs

Question 24

What are antibiotics as found in Nature?

Answer 24

Bacterial signal molecules, bacterial secondary metabolites, and produced by fungi and soil bacteria

Question 25

Order these by rank as considerations for treating a dental infection that clearly appears to be anaerobic, like an abcess:
(erythromycin - beta lactams - clindamycin - metronidazole)

Answer 25

(Beta lactams - erythromycin - metronidazole - clindamycin)

Question 26

What is clavulanic acid?

Answer 26

This is the inhibitor of the resistance mechanism most commonly encountered for beta lactams. It is half of the ‘Augmentin’ combination. It is another decoy- a competetive inhibitor of these bacterial secreted enzymes that can cut B-lactam rings.

Question 27

Clinical dentistry indicates the use of antibiotics in all of these situations. Choose the one where antibiotics are not routine:

Answer 27

Anaerobic soft tissue abscess in a healthy patient

This is a judgment call and done differently by different practitioners. The types of named syndromes and lesion types will be more clear in your clinical training. A generic uncomplicated abscess is not routinely treated with antibiotics in an otherwise healthy patient, only drained.

Question 28

Guidelines on the prophylatic use of antibiotics in routine dental procedures have changed through the years, resulting in confusion about this. Indicate which of these REMAINS on of the instances where antibiotics are used prior to invasive dental procedures:

Answer 28

History of infective endocarditis

This is a high yield area to know. Go over the different discontinued and remaining indications, and test yourself again on sorting them out for practice.

Question 29

Metronidizole is a very useful drug with low resistance because of its mechanism of action. Which is a limitation of its use?

Answer 29

It only works on microbes growing anearobically & It is not compatible with patients unlikely to comply with instructions not to mix with drinking

Question 30

(T/F) B-lactams are simply never an option when it comes to someone indicating they may have had an allergy to penicillin as a child.

Answer 30

False

People can be tested for this allergy in very low dose, and are unlikely to react. However, this is is difficult to take advantage of in practice unless part of a long range plan.

Question 31

The two major type of pathogenic staphylococci are readily distinguished by:

Answer 31

Production of white or yellow pigment & production of coagulase

Catalase production is used only to identify Streptcoccus relative to staphylocci, Both are common Gram positive cocci where only both staph have the catalase enzyme. Both coagulase positive and negative staphylococci are found on the skin, although aureus inhabits the nose of some people.

Question 32

Which of these staphylococcal virulence factors would be most important for growth in the bloodstream and sepicemia?

Answer 32

Presence of a polysaccharide capsule

Capsules shield bacteria from phagocytic cells in the blood stream. This is the only virulence factor of direct relevance as the question asks.

Question 33

Which of these is not a disease frequently associated with staphylococci?

(sinusitis - meningitis - arthritis - bone infection - impetigo -endocarditis)

Answer 33

Meningitis

Question 34

What is the staphylococcal A protein?

Answer 34

Surface molecule that binds antibodies non-specifically

Question 35

What is the difference between greek and roman/latin letter (A, B, etc.) designations for groups of streptococci?

Answer 35

Roman indicate different serotypes - greek indicate different hemolysis patterns

Roman letters are for Lancefiled serology groups that are now used mainly to distinguish two different types of beta-hemolytic (cleared zone) streps. Group A, or S. pyogenes, and the enteric Group B streps, which we did not cover in the class, but are a cause of newborn infections.

Question 36

What are the important post-infection Sequelae in Streptococcus pyogenes (G.A.S.) disease?

Answer 36

Rheumatic Fever and glomerulonephritis

Scarlet Fever is an acute phase of GAS (S. pyogenes) infection.

Question 37

What are the secreted damaging enzymes causing hemolysis on blood agar generically called?

Answer 37

Streptolysins

Spe proteins are Strep pyogenes (s.p.e) toxic shock superantigens like those made by Staphylococcus aureus, Protein G is a surface protein that binds antibodies non-specifically.

Question 38

Which is correct in terms of the relative pathogenic potential of S. pneumoniae and S. oralis?

S. pneumoniae can cause heart valve infections

S. pneumoniae is able to cause many diseases

S. oralis can cause heart valve infections

Answer 38

All are correct

Like S. aureus, S. pneumoniae is a generalist in terms of known roles in many infectious diseaases. The oralis group streps are only known to cause heart valve endocarditis in patients already at risk that require prophylactic antibiotics for invasive procedures.

Question 39

What is the simplest way to definitive identify Streptococcus pneumoniae causing characteristic disease?

Answer 39

Distinct cell shape and arrangement

Question 40

The pneumococcus is alpha hemolytic unless

Answer 40

Grown anearobically

Question 41

Which pair of infectious diseases caused by S. pneumoniae are caused as frequently by other bacteria?

Endocarditis and arthritis

Meningitis and ear infection

Bacteriemia and impetigo

Answer 41

All are correct.

Pneumcoccus only is distinctive in the frequency in which it is found to be the cause of pneumonia. Although it is also a cause of all these other diseases, other bacteria are as or more often.

Question 42

Which of the Gram positive rods form spores?

Answer 42

Bacillus and clostridium

Question 43

Which of the Gram positive rods are strictly anaerobes?

Answer 43

Clostridium

Question 44

(T/F) Teichoic acids are always inflammatory

Answer 44

False

That in the cell wall of Lactobacillus may help regulate immune responses.

Question 45

Which of the Gram positive rods are intracellular bacteria?

Answer 45

Bacillus anthracis, listeria monocytogenes, and mycobacterium tuberculosis

There are many more than the examples used in basic textbooks that we saw earlier in the class (chlamydia, rickettsia, and mycoplasma). This a vey important thing to know about these types of bacteria, they all grow inside of human cells, rather than on epithelial surfaces or in tissues like clostridia.

Question 46

What is the difference between the ‘O antigen’ and Lipid A in Gram negative LPS?

Neisseria LPS lacks the O-antigen

The O antigen is used in strain typing differences among the same species

Haemophillus lacks the O antigen

Answer 46

All of these

Neisseria (meningitides and gonorrhea) have ‘LOOS’ rather than LPS, which is lacking the long outer O antigen regions. Lipid A is the base which gives the biological activity or endotoxin, and can cause shock if levels rise in the blood.

Question 47

Which is NOT a Bordetella toxin?

Answer 47

Spe superantigen

PT causes host cells to produce cAMP, and adenylate cylase toxin is a bacterial secreted enzyme that does the same thing. Tracheal toxin is a petidoglycan monomer exported to the periplasm. These three are part of Whooping Cough symptoms. Spe is Strep pyogenes (GAS) toxc shock superantigen toxin.

Question 48

Which of these bacteria is NOT a major cause of meningitis?

Neisseria meningitides

Strep pneumoniae

Staph aureus

Answer 48

Staph aureus

Respiratory, encapsulated → bloodstream → meningitis, or the triplets Haemophilus influenzae, even though S. pneumoniae is Gram positive, and more likely to cause this in adults. Neisseria is associated with outbreaks among young adults living in close settings. Vaccines have largely stopped deadly childhood meningitis by Haemophilus influenzae.

Question 49

Which of these are true about Haemophilus influenza?

It is a major cause of ear infections from the throat

The vaccine is a protein conjugated capsule antigen

Can cause penumonia

Answer 49

All are true

A once deadly bacteria controlled by a great vaccine.

Question 50

Is there a vaccine for Cholera?

Answer 50

Yes, it’s a live strain of Vibrio

Question 51

What is the Vi capsule that is important in Typhoid Fever?

Answer 51

Capsule seen only on S. Typhi bacteria, important in using live Salmonella as a vaccine, and it is antiphagocytic

Typhoid Fever is more dangerous than Salmonella Typhimurium food poisoning. S. Typhi can make a capsule that allows it to survive in the blood stream and cause a systemic infection, S. Typhimurium does not.

Question 52

Which is NOT a toxin E. coli can acquire by horizontal gene exchange and become dangerous?

shiga toxin

heat stable toxin

heat liable toxin

LPS endotoxin

Answer 52

All of these are E. coli toxins.

E. coli is a one of the normal gut bacteria, but not the most abundant one. People appear to be colonized dynamically by different strains at different times. They are medically important because of gaining properties from related gram negative enteric bacteria, particularly quickly by conjugation.

Question 53

What is distinct about Shigella among the other Enterobacteriaceae ?

Answer 53

It is intracellular, invading epithelial cells

Also has the ‘shiga toxin’ that it can transfer to E. coli.

Question 54

Streptocccus pneumoniae is a potentially dangerous bacteria tha normally resides in the…

Answer 54

upper respiratory tract (mouth, nose , throat, etc)

Most common bacteria cause of human infectious respiratory disease, half of which are viral. For this topic, know the sites that are colonized, and where medically important bacteria covered are found.

Question 55

Which of these is NOT a normal resident of the oral microbiota?

Diptheria

Neisseria

Tannerella

Streptococcus

Answer 55

Staphylococcus aureus

Staph. aureus inhabits the nose of about 30% of so of people, but not the mouth.

Question 56

Moraxella are an odd coccus shaped Gram negative bacteria. What other genus of Gram negative coccus normally inhabits in the same body site?

Answer 56

Neisseria

These are the only two medically important Gram negative cocci, making them quite unique.

Question 57

(T/F) Most or all abundant oral bacteria have been proposed to play a role in periodontal disease.

Answer 57

True

Some, like those of the Red Complex, have historically thought to have a more central role. Which bacteria are those again?

Question 58

Which of this is not a valid theory about how periodontal disease occurs?

Answer 58

Aerobic bacteria outgrow and dominate the gingival crevice

Ideas change over time, but all of these remain true, except C. C would be the opposite, it is thought that strict anaerobes like P. gingivalis rise as facultative anaerobes fall in levels.

Question 59

What Gram positive bacteria are important colonizers of the gingival pocket in both health and disease?

Answer 59

Streptococcus and Actinomyces.

Question 60

About how many bacterial types do we now think are normally found in the mouth?

Answer 60

~600

Question 61

(T/F) Periodontitis is different than other diseases that are now being associated with the gut microbiota, as studies are finding more diversity of species in disease than in health.

Answer 61

True

We generally see a narrowing of the bacterial diversity as relevant to disease at other body sites that are normally colonized.

Question 62

Which Mutans streptococcus contributes to caries by producing water insoluble glycans and acid?

Answer 62

Strep sobrinus

This role of Strep sobrinus in caries is less well proven than that of Strep mutans, but is widely accepted.