Bacteriology
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Bacteriology - Details
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| 🇬🇧 | 🇬🇧 |
| What is an infection? | It is when a microorganism accomplishes 5 steps: 1-Adherence and Penetration 2-Survival 3-Multiply 4-Release out of the host 5-Infect other hosts (transmissiblity) |
| What do we mean by subclinical infections? | They are infections that occur but are asymptomatic (most infections are asymptomatic) |
| What are clinical infections? | They are infections that cause symptoms |
| Are infections and inflammations the same thing? | No! Infection=عدوى Inflammation=التهاب |
| What do we mean by acute illness? | They are illnesses that occur suddenly and are found for a short period of time (opposite of chronic illness) |
| What do we mean by carriers of infection? | They are asymptomatic infected individuals that are able to transmit the infection. |
| What do we mean by recurrent illness? | They are illnesses that reoccur after they disappear. For example herpes, which comes from either saliva (kissing, eating from same spoon...) called herpes labialis or sex transmitted called genital herpes.... Pxs present ulcers either on lips or genitals, they disappear yet they may reappear after a while induced by stress. |
| What do we mean by latency of an infection? | It is the time the infection is inapparent before it reappears and causes symptoms (like herpes hiding) |
| What do we mean by NCD? | Non-communicable diseases, such as diabetes HTN heart attacks... |
| What do we mean by risk factors? | They are factors that facilitate the infection to have clinical manifestations (such as smoking, non sterility...) |
| What do we mean by immunopathological diseases? | They are diseases that disturb the immune system so that it triggers unwanted actions done by it, makes the immune system as the bad guy |
| Give examples on immunopathological diseases. | ARDS (acute respiratory distress syndrome) which may occur due to flu, burning... and causes pulmonary edema, lungs are filled with water, and gas exchange becomes harder...Thus leading to hypoxia, all due to immune system acting on pneumocytes (cells of alveoli) Another one is COVID, Hepatitis, Viral Rashes (which are coupling of viruses with antibodies going to the skin and appearing as a rash |
| What do we mean by opportunistic infections? | They are infections that take advantage of situations to occur (for example a person recieving treatment for HIV and another without it, the clinical manifestations...) |
| Give an example of opportunistic infections. | Contaminated Foli Catheter inserted causing urinary edema Fungi for atheletes feet due to humidity |
| What do we mean by a pathogen? | Any bacteria that causes a disease is a pathogen. Bacteria may be pathogenic or non-pathogenic, and may alternate between both according to certain conditions. |
| What do we mean by virulent factor? | Is the factor that causes a bacteria to become pathogenic |
| What do we mean by oncogenicity? | Virulence that can lead to cancer in some infections. |
| What do we mean by nosocomial infections? | Infections that occur in healthcare places (hospitals, clinics...) |
| In what type of procedures do nosocomial infections usually occur? | Invasive operations where we are inserting something into the px. It is preferred to leave any invasive action as our last option. |
| What are examples of common nosocomial infections? | Staphylococcus aureus, E.coli (in urinary system causing UTI ) |
| What do we mean by microbiota? | AKA normal flora, they are bacteria that aid with body functions, they are the first line of defense, digestions, toxin degradation and immune system maturation... for example bacteria that digest cellulose/starch into fatty acids that inhibit immunopathological events from occuring. |
| What do we mean by resident and transient microbiota? | Resident: present always in our bodies Transient: present for some in a period of time. |
| Is it healthy to consume alot of antibiotics constatly? | Alot of antibiotics may lead to damage in necessary microbiota which will lead to more infections. |
| Give an example of transient flora. | Staphylococcus Aureus found for some people at nasopharynx can be transmitted by sneezing/ nose picking to other non-carrier people and cause clinical manifestations maybe. |
| What are probiotics? | The opposite of antibiotics, restore flora activity. |
| What is quorum? | It is a high density community of bacteria that are needed to perform a certain function, for example bioluminescence for vibrio fischeri in symbiosis with fish, they do not glow unless bacteria are in high density making a quorum. |
| What is quorum sensing? | It is the process which makes the bacteria able to know whether they made a quorum or not. it is done by the release of auto inducers/ pheromones which are recognized by these bacteria, and the more concentrated the more it means that we have a quorum, and thus activating bioluminescence/ virulence. We may also have a low density community of bacteria but with a high amount of pheromone release, thus acting as a quourm. |
| What is biofilm? | It is when a number of bacteria are stuck on a surface, and start releasing biomolecules (polysaccharides, glycoproteins...) making a layer of slimy substance that may be virulent An example is plaques of teeth. |
| What do we mean by epidemiology? | We answer the three questions: Where, When, and Who is affected+ modes of transmission of diseases caused by any bacteria/virus. For example: epidemio of TB is in india, in 2022 for the underprevelaged people living in rural areas. |
| What is an endemic? | Is a disease spread but limited to a particular region For example: Malta fever/ Brucellosis which is usually found in the mediterranean due to the large consumption of diary products there. |
| What is an epidemic? | Its a disease which came from outside of a region where it usually doesn't exist. For example: increasing HIV in Lebanon |
| What is the difference between bright-field and light-field light microcopes? | Bright field emmits light on the whole specimen showing the whole structures, while dark field emits light only on the sides of the specimen (showing only the borders of the sample.) |
| What kind of microscopes do we use to see bacteria vs viruses? | Bacteria= light microscope, virus= dark microscope. |
| What kind of microscope do we use to observe spirochetes with small diameters? | Dark-field light microscope, since with light field the spirochetes wont appear due to their small diameter, light will pass right through it. |
| What disease is caused by bacillus anthracis? | Anthrax which is used in bioterrorism, and causing organ failure, sepsis, inflammations, hemmorrhage and possibly death |
| What is meant by fluorescence? | Adding fluorochromes into something to color it (for example: TB glowing yellow with fluorescence) |
| What are the two types of immunofluorescence? | Direct (antibody with fluorochrome attaches directly to the bacteria) Indirect (antibody attaches to another secondary fluorescent antibody to color it) |
| Are introns present for bacterial genes? | For eubacteria yes, for archae they are abscent. |
| What are episomes found in bacteria? | They are non-chromosomal DNA molecules (plasmids) that may have a function in conferring against antibiotics |
| What are inclusion bodies found in bacteria? | Vacuoles with stored elements such as glycogen, poly-beta hydroxybuteric acid(PHB).. |
| What kinds of polyphosphate granules are found within bacteria? | Volutin (AKA metachromatin) |
| What are magnetosomes? | Collecting irons in bacteria |
| What is the mesosome? | It appears in the middle of the bacteria, its debated whether its an artifact during staining or has a role in binary fission |
| Do bacteria present sterols in their plasma membranes? | No sterols, instead they present hopanoids. For archae, isoprenoids are present instead of sterols For mycoplasma where no cell wall is present, sterols are present (the only exception) |
| Why do proteins in bacteria exist in larger amount than those of human cells plasma membranes? | Since bacteria live on their own, not inside an environment of an organ, so they need a lot of strength to survive --->increase in protein quantity. |
| What does exoenzymes mean? | They are enzymes secreted by bacteria and exerted outside where they apply their actions (for example cytotoxins that destroy other surrounding cells) |
| What does chemotaxis mean? | Movement induced by chemokines for bacteria) |
| What kind of passive diffusions usually occur for bacteria? | Simple and channel protein diffusions |
| What are sidophores? | They move iron from outside the bacteria |
| What is lactoferrin? | They are molecules that attract iron from milk, found mostly for babies in order to get iron for the body in opposed to magnetosomes of the flora. |
| What bacteria cannot be stained by gram staining? | Acid-fast bacteria, and mycoplasma (cannot be stained by any kind of staining since lacks cell wall) |
| What do we ask a px who we need a urine sample from to do? | Give us urine from midstream, since the upstream urine will be contaminated by flora from the skin, so in order to indentify whether we have a UTI, we need to exclude these flora and look for bacteria found inside the urinary tract.. |
| Describe the procedure of identifying gram + and -bacteria. | Add crystal violet to sample - it will dye all bacterial cell walls purple. add iodin- will fixate violet into only gram+ since they have a thich cell wall. Add ethyl alcohol which will remove purple from gram- add safarrin which will stain the unstained gram- pink |
| What do teichoic acids contribute to in bacteria? | Pathogenesis (they are virulence factors) |
| Describe the molecules of the peptidoglycan layer. | N-acetyle glucasamine and N-a muramic acid attached to each other by beta (1-4) linkage This linkage is destroyed by lysozymes, thus making gram + sensitive to it while gram - not (only 1 layer of peptidoglycans) Tetrapeptide is attached to NAM sugar (alanine, glutamine, another aa, and DAP diaminopymelic acid which is precursor of lysin found only for bacteria) |
| Talk about teichoic acids in bacteria. | Found in gram+, present at cell wall and at membrane, give the structure of the cell wall (rigid) negatively charged. |
| What constitutes the gram- envelope? | Endotoxins Lipoproteins Lipopolysaccharides (three layers: Lipid A which is constant among bacterial species and causes immunopathology (sepsis)/ B = core saccharide which is the same for all gram -/ and C which is O antigen is unique for each species and important for stereotyping. |
| What external structures are found for bacteria? | Pilli (made of pillin protein, similar role to cilia, could be an adherence role like E.coli in urinary tract mediates attachment, pilli may by considered as virulence factors in the case of E.coli causing UTI, sex pilli cause conjugation role DNA exchange) Flagella (Differ from euakryotic, made by protein flagellin, flagella has H-antigen) |
| What are the types of flagellated bacteria? | Atrichous (no flagella) monotrichous (one flagella) Lophotrichous (many flagella in one side) Amphitrichous (one flagella on each side) peritrichous (many flagella all over) amphilotrichous (many flagella on two opposite poles) |
| Talk about capsule of bacteria. | Usually polysaccharides made, may be polypeptide (for bacillus anthracis) Capsulated bacteria = have more protection. capsules are tightly attached >> glycocalyx >> slime |
| What are biofilms? | Combination of slime and calyx, making a middle sugar layer (for example plaques at teeth causing periodontitis) |
| Talk about bacterial porins. | Usually wide causing bacteriophages (viruses) to enter. LamB porins transport sugars Tsx porins transport nucleotides and amino acids OmpA porins are recievers of sex pilus for conjugation (F-mediated) |
| What are protoplasts and spheroplasts? | They are L formed bacteria that are capable of growing and dividing unequally/ unevenly and lost their cell wall for an unknown reason, which makes them hard to culture |
| How do we culture protoplasts and spheroplasts? | By treating them like eukaryotes (since they lost their cell walls and became more fluid). |
| Can protoplasts and spheroplasts be stained? | No (lost cell wall) |
| What kind of bacteria are protoplasts and spheroplasts? | Protoplasts: gram + and spheroplasts: gram - |
| Is mycoplasma a protoplast or a spheroplast? | It was once considered as an L form. |
| Interpret this graph. | This is the graph of what happens to bacteria when facing rough conditions. X axis is the time, Y axis is the number of cells. First bacteria are in latency phase, they are still managing the conditions, then they enter the exponential phase, where they increase in number to stay alive, then they enter the stationary phase, where cells are still managing their life together, and finally if no spores are formed, they enter the D phase which is the death. If spores are formed it stays on S phase |
| What is a spore? | Haploid, non-functional state of a bacteria which occurs on harsh conditions. When no more nutrients are present. |
| Which bacteria undergo sporulation? | Gram + like Bacillus and Clostridium. |
| What does germination mean? | Opposite of sporulation, when bacteria retains its functions when nutrients are present. |
| List the steps for sporulation. | 1-Cell Division 2-Axial filament formation (septum forming assymetrically) 3-Big cell engulfs the small one making the forespore (Small cell) 4-Nucleiod of big cell denatures, only forespore remains. 5-Formation of cortex between inner and outer membrane of forespore (outer coming from big cell) 6-Synthesis of caot from keratin which is very tough 7-Exosporium formation which is an outer layer of lipoprotein and carbs giving strength. 8-Cell intakes needed nutrients and calcium dipicolinate inside the forespore. 9-Spore is released. |
| List the layers of the formed spores of bacteria (inside to outside) | Inner membrane Cell wall Cortex Outer membrane Coat Exosporium |
| Where do we find Clostridium Tetani spores? | They are presents as spores in rusty nails, soil and sometimes in animal bites Tetani (كزاز - صدأ) |
| What are the different shapes spores present in? | Different shapes are according to the placement of the nucleiod. May be central, terminal or subterminal |
| What is the shape of the Clostridium Tetani spore? | Looks like a tennis racket (drumsick appearance) |
| What does refractivity mean? | Ability for refraction (it increases due to the coat of spores) |
| What do we mean by culture medium? | It is a tube containing nutrients where we can witness bacterial growth and multiplication. |
| What kinds of culture media do we have? | Broth medium (tube containing liquid nutrients) Agar medium (Petri dish with gelly texture - includes solidifying agent - called petri in response to the scientists name, his wife suggested it) |
| How to witness bacterial growth in petri dishes? | Adding one drop of bacteria and streak it, after adding nutrients and maybe red blood cells (streptococcus and staphylococcus) After streaking, bacteria is less on loop of dish and more on the agar, and they start appearing as little dots: these are colonies of bacteria, that resulted from one microscopic one. |
| Why do we call bacteria colony forming unit? | Since one microscopic bacteria on agar may give us a colony of bacteria seen as a dot on the eye sight level. |
| What are the two categories of culture media? | Selective (for specific bacteria , like MacConkey agar which has bile salts stopping gram + growth thus making it gram - selective) Non-Selective (Gives colonies of all kinds if bacteria, without distinguishing them) |
| What is the differential medium? | It is a medium where chemical reactions done by bacteria allow us to identify it. Non-selective Strep and staph |
| What is the enrichment medium? | Medium where we add nutrients for bacteria to grow fast |
| What is the specific culture? | Selective and specific for one kind of bacteria, works only on salmonella and shigella (SS culture) |
| Talk about coccus shape of bacteria. | Diplococcus (strep pneumonia) Streptococcus (Streptococcus pyogene - causes pharyngitis (sore throat)) Tetrad (4 coccus) Staphylococcus (many dimensions like grapes) |
| Talk about bacillus shape of bacteria. | Spore - former (clostridium botulinum) Flagellate bacilla (flagellated rod - Salmonella typhi) Streptobacilli (chain of bacilli) |
| Talk about spiral shapes of bacteria. | Vibrios (Coma , shaped appearance - vibrio cholera) Spirilla (heliobacter - helicopter shape - flagella on one side) Spirochetes (spiral appearance with narrow width - observed by dark microscope) |
| Do we consider different bacteria types associating as biofilms? | No, in biofilms we are talking about cities of bacteria (millions and billions) |
| How is the metabolism of bacteria mediated? | Through genetics, where enzymatic proteins mediate anabolism and catabolism of sugars, lipids... using focal metabolites (like aa and sugars) bacteria metabolism occurs |
| Do focal metabolites follow the same pathway of metabolsim? | No, there are many pathways according to the needs of the bacteria. |
| What is serotyping? | It is a test designed to describe a way of grouping of the bacteria, it is forensic fingerprinting by using antigens and antibodies attaching to them. |
| How many serotypes does vibrio cholera have? | Over 300 serotypes, but only O1 and O139 are what cause endemics and epidemics. |
| What microorganisms can be serotyped? | Bacteria (have many O and H antigens) and viruses. |
| What is hybridoma technology? | Cancer cell + B cell merged together to make loads of antibodies (monoclonal) |
| What is quasispecies? | Core of antigen O in gram- is common for gram - but every strain has its own antigens Bacteria with small oligosaccharides instead of polysaccharides (O1.1 1.2 1.3) |
| Give an example of problematic quasispecies. | Immune system cannot degrade Neisseria Gonorrhea since it keeps changing oligosaccharides O antigen (so it has different but predictable O antigens but shifting makes it unpredictable) |