Microbiology Cameron McCloskey Flashcards
Gram+ organisms stain…
Purple
Stain well due to thick peptidoglycan layer
Gram- organisms stain…
Pink
Thinner peptidoglycan layer doesn’t retain stain well
Endotoxin is produced by…
Grams -
Exotoxin is produced by…
A
Gram+ organisms and G-
Exported from the cell
Gram+ cocci in chains are?
A
Streptococciستريبتو كوسكاي
Gram+ cocci in clusters are?
A
Staphylococci ستافيلو كوكاي
Coagulate positive in clusters
The test to classify different Streptococci spp.? ستريبتو كوكاي
Haemolysis
Alpha (partial) - Strep. pneumoniae + viridans
Beta (complete) - Group A (pyogenes) and B Strep.
Gamma (none) - Enterococcus sp.
Examples of: Alpha-haemolytic Streptococci?
A
Strep. pneumoniae نومونيا + “viridans” group
Examples of: Non-haemolytic Streptococci?
A
Enterococcus sp. انترو كاكس
The test to distinguish Staphylococcus aureus from other Staph. spp.?
A
Coagulase test
+ve = Staph. aureus اوريس
-ve = other Staph. spp. and epidermidis (common skin commensals)
Opportunistic pathogen? ابرو تونيستك
Probably only cause infection in immunocompromised individuals
Virulence?
A
Degree of pathogenicity of an organism
Stages of viral replication?
-Attachment
-Entry - endocytosis
-Uncoating - viral nucleic acid released from capsid
-Nucleic acid and protein synthesis - host ribosomes used or polymerases
-Assembly = nucleic acid and proteins packed together
-Release =
Budding- Viruses released with envelope
derived from host cell membrane
Lysis- Virus accumulates until cell bursts,
kills cell
Virus detection?
PCR
Antigen detection
What do cytoxic T lymphocytes do in virus immunity?
A
Recognise proteins on cell surfaces as foreign and signals infected cell to commit suicide in order to prevent formation of new viruses
The 5 methods of spread of infection are…
A
Inhalation, Ingestion, Inoculation, mother to Infant, Intercourse
Viruses contain RNA or DNA, never both. True/False?
True
Size of their capsid (protein coat) limits space
Of both gram positive and negative which of the two has a larger periplasmic space?
A
Gram negative
(They have two different periplasmic spaces)
Which bacteria class has two membranes?
A
Gram negative
(Outer and plasma)
What exists on the outside of gram negative bacteria that confer antigenic properties?
A
Lipid polysaccharides (endotoxins)
Besides having antigenic properties, what other important characteristic do lipid polysaccharides possess?
A
They have bacterial toxin properties which cause damage to neighboring cells and evoke an inflammatory response
Why are gram positive bacteria more susceptible to antibiotics?
A
The outside peptidoglycan layer can act as a target for antibiotics such as penicillin
What happens when antibiotics bind to the peptidoglyan layer of gam positive bacteria?
A
The peptide cross links within peptidoglycan are broken down
What are flagella and fimbriae (pili)?
A
Extracellular proteinaceous extensions
What 5 key factors so bacteria require to grow and thrive?
A
Food (C, O, H, N, salts and vitamins etc.)
Correct temperature
pH
Osmotic pressure
Oxygen content
What are the stages in the chain of infection?
A
- Infectious microbe
2.Reservoir - Portal of exit
- Mode of transmission
- Portal of entry
- Susceptible host
What are the only 5 ways in which infection can be spread?
A
Inhalation
Ingestion
Inoculation (vaccination or artifical introduction) - direct or indirect
Mother to infant - vertical transmission
Intercourse - STI or STD
In what 5 situations (clinically) is hand washing necessary?
Before patient contact
Before aseptic task
After bodily fluid exposure
After patient contact
After contact with patient surroundings - when leaving zone
What are the three bacterial shapes?
A
Bacilli
Cocci
Spiral shaped
In what two ways can cocci divide?
A
In two planes - produce chains
In three planes - produce clusters
what is Atypical Bacteria
A
atypical bacteriais that they cannot beculturedin the normal way or detected using agram stain. most often implicate in pneumonia
What bacterium causes the disease cholera?
A
Vibrio chlolera
(Vibrio family of 34 members)
What are rigid spiral bacteria called?
Spirillum سباي ريليم
What are flexible spiral bacteria called?
A
Spirochaete سبايروكيت
How are the flagella utilised differently between spirullum and spirochaete?
A
Spirillum - tufts at each end to aid movement
Spirochaete - within periplasm causing cork-screw motion - efficient at travelling through secretions
What are fusiform bacteria?
A
Bacteria with a thin strand structure that play a part in the natural gut flora
Why are fusiform bacteria potentially dangerous?
A
By crossing the placenta in pregancy, they can cause still births and even cancer
With gram positive bacteria there is only one type of membrane, what is it?
A
Cytoplasmic membrane
What is selctive media?
A
This is a growth medium that contains specific nutrients for a specific type of microbe to grow over others
What is haemolysis?
A
Destruction of red blod cells
What is alpha haemolysis?
A
Partial haemolysis - greening of colonies (remember greening )
What is beta haemolysis?
A
Total haemolysis - the most aggressive
What is gamma haemolysis?
A
No haemolysis
What is multi locus sequence typing (MLST)?
A
This allows sequences of bacterial DNA and entire genomes to be sequenced and uploaded to a database
This allows previously sequenced sections to be matched to newly scanned sequences
Microorganisms can be classed depending on where they originate in relation to the body. What are these classifications?
A
Endogenous - originate from within the body
Exogenous - originates outwith host
- Endotoxin is not really a toxin its a series of components from the outer surfaces of the Gram-negative cell wall, that you think of as being the predominant material the Lipopolysaccharide or LPS. Its immunostimulatory and key factor in Gram-negative sepsi
What are commensal organisms?
A
Organisms that are Endogenous , part of the natural flora and often form mutual relations with the host
examples E.(scherichia) coil (urinary infection) , Klebsiella and proteus (wound infection) .
What are opportunistic organisms?
A
Exogenous organisms that infect the host when there is an opportunity such as immunocompromisation
Aerobic gram negative cocci appear in which formation?
A
Diplococci ديبلو كوكاي (two cocci)
What are the two (out of 10) pathogenic aerobic gram negative cocci species?
A
Neisseria .(ناسيريا) meningitidis - can cause meningitis
Neisseria gonorrhoea كا نا ريا - can cause gonorrhoea
What are coliforms كولافورم?
A
Gram negative bacteria - rod shaped and non-spore forming
Can grow either anerobially or aerobically - better aerobically
Many part of the natural bowel flora
Should not enter sterile areas as can cause disease e.g. peritonitis, UTI, biliary tract infection etc
What is the first line antibiotic used for any infection caused by coliforms?
A
Gentamicin
What is it on the outside of gram negative bacteria that stimulates the immune system?
A
Lipopolysaccharides (endotoxins) composed of O antigens and lipids
Why can it be advantageous for gram negative bacteria to stimulate the immune system?
A
Vascularity, available nutrients and protein production can increase
Describe the mechanism of fever production which lead to sepsis
A
Endotoxin interacts with macrophages to stimulate immune response and cytokine release
Cytokines cause adverse effects of sepsis and travel to the hypothalamus
Prostaglandin E is produced which means the body perceives itself as cold
Shivering is stimulated which generates heat and rasies the body temperature
Describe the process of sepsis
A
Small blood vessels become leaky meaning fluid is lost into tissues - due to inflammation
This causes hypovolaemia
Blood pressure is reduced
Organ perfusion becomes inadequate and organ shutdwon may occur
Blood clotting system activates leading to clot formation
Clotting factors become used up leading to haemorrhage
When will septic shock occur?
A
After cell death lipopolysaccarides are released (causing inflammation), yet this also happens with valid treatment
But, due to the sudden disintegration of many cells septic shock will occur due to the huge immune response initiated
What is the most important group of non-haemolytic streptococci?
A
Enterococci ينترو كوكاي
(two type of enterococcus E.faecalis and E.faecium)
What is Clostridium كلوست ريديم spp and why is it hard to treat?
A
Gram positive anaerobic baccili باسلي - part of normal bowel flora
Spores are produced - can live outside body
Exotoxins produced can cause severe body damage
Antibiotic resistant (spore production) and general resistance
What are the two main classes of antiobiotic that related to their function?
A
Bacteriostatic - inhibits growth
Bacteriocidal - kills bacteria
What are narrow spectrum antibiotics?
A
Antibiotics which are very specific in the bacteria that they target
Which types of antibiotics will target the cell wall?
A
B lactam (includes penicillins)
Glycopeptide
Describe how penicillin halts cell wall production
A
Peptide cross links exist in the cell wall
These are formed from D alanine to D alanine terminal proteins
Such terminal proteins are formed when transpeptidase cleaves this dipeptide, releasing energy and creating the bond
Penicillin resembles a terminal protein such as this and can bind irreversible to transpeptidase which halts cell wall production (((((bactericidal antibiotic))))
What are beta lactam antibiotics?
A
Antiobiotics containing the beta-lactam ring in their molecular structure
Common in penicillins, co-amoxiclav, cephalosporins etc.
Name a penicillin which targets gram positive bacteria well
A
Flucloxacillin
فلوكلو كلاسلين
(IV or oral)
What are the 3 forms of penicillin?
A
Benzylpenicillin |(b’enzil) (penicillin G) - IV
Phenoxymethyl فا نوكسي penicillin
(penicillin V) -oral
Benzathine بين زاثين penicillin - IM
What is flucloxacillin فلكو كلاسيلين commonly prescribed for?
Streptococcus aureus
Skin infections from staph and strep
Deals with gram positive bacteria
What is the purpose of clavulanic كلافالانك acid in co-amoxicillin ?
A
B lactamases are microorganisms that destroy the B lactam ring of antibiotics including amoxicllin renderinging them useless
Clavulanic acid inhibits B lactamases which allows the B lactam ring to remain intact.
Essentially co-amoxiclav is a “work around” to allow amoxicillin to work where it wouldn’t normally
What is special about temocillin?
A
It is resistant to B lactamases
It will generally target coliforms
Cephalosporins are very attractive antibiotics due to their bacteriostatic and bacteriocidal properties as well as being B lactamase resistant. However, what is their major disadvantage?
A
They are broad spectrum so cause damage to the natural flora
This clears the environment for dangerous bacteria which they cannot kill
They remove the competition for harmful bacteria
Do glycopeptide antibiotics possess a B lactam ring in their structure?
A
No
Give two examples of glycopeptides
A
Vancomycin
Teicoplanin تيكو بلينين
How do glycopeptides function?
A
They bind to the end of peptides
This prevents peptide binding proteins such as transpeptidase from binding to their substate (the protein)
Proteins cannot be incorporated into the cell wall
Peptidoglycan cannot be synthesised
Cross links are reduced and the cell wall is weakened
Why can glycopeptides only function on gram postitive bacteria?
A
The outer membrane in gram egative bacteria blocks any activity they could have on the peptidoglycan layer
Describe how antibiotics can target bacterial protein synthesis
A
Human ribosomes are different to bacterial ribosomes
Antibiotics are taken into bacterial cells by active transport
They bind to the 30S subunt and prevent tRNA from binding at receptor sites
The chain of elonagtion is inhibited
What type of antibiotic is gentamicin جين سيمنتن and why is it bactericidal?
A
Aminoglycoside
Gentamicin targets protein synthesis
When it binds to the 30S subunit in the ribosome, it inhibits protein sythesis
bactericidal antibiotics, meaning that they kill bacteria rather than just inhibiting their growth.
What is the mode of action for the tetracyclines?
A
They are transported into the cell and bind to the 30S subunit of the ribosome.
This blocks tRNA binding sites and stops chain elongation
ive an example of a tetracycline تيجري سكيلين antibiotic
A
Doxycycline
Tetracycline
Minocycline
What is the mode of action for macrolides?
They are taken into cells and bind to the 50S subunit in bacterial ribosomes. Prevent peptidyl transfer in proteins during translation. (chloramphenicol has similar process)
They can be lipophilic antibiotics and can easily pass through cell membrane to “find” bacteria hiding from the immune system.
Give an example of a macrolide antibiotic
A
Erythromycin ايري ثرومايسن
Clarithromycin كليري ثرومايسن
Azithromycin ايزي ثرومايسن
Describe how quinolone كوين الون work
They bind to the alpha subunit of DNA gyrase and prevent supercoiling of DNA which indirectly inhibits DNA synthesis
They are bactericidal
What is an example of a fluroquinolone? فلورو كوينلون
Ciprofloxacin سيبرو فلوكسيسين
Levofloxacin سليفو فلوكسيسين
Why is the use of fluroquinolones فلورو كولو لون very restricted?
They are broad spectrum
Why is folic acid required by bacterial cell and which antibiotics can prevent its synthesis?
Required to syntheiss key cell components
Sulphonamides and trimethoprim جراي ميث برم ، سيلفا نيماد
• Both Excreted via the urine
What are the serious side effects of gentamicin?
Renal damage and damage to cranial nerve VIII ( vestibulocochlear nerve)
Which antibiotics are associated with increased risk of clostridium difficile كلوستيريم ديفيسيل C diff? Which cause bowel infection
Cephalosporins سيفرو سبرانس
Co-amoxiclav كو أيموكسي كلاف
Ciprofloxacin سبرو فلوكسيسين
Clindamycin كلندومايسين
What is a biofilm?
A protective layer around a microorganism that allows it to grow in different environments
What are persister cells?
Cells that are extremely resisatnt to antibiotics
This is because they are encased within biofilms and cannot be targeted by antibiotics when in a dormant or inactive state - which they often are
What are some methods that bacteria use for horizontal gene transfer?
Transformation - genetic material is released into the extracellular space
Transduction - via bacteriophages (viruses that use bacteria to replicate within)
Conjugation - exchange of plasmids through direct comtact via sexual pilus
What are the two different types, or stages, of resistance? (2)
Cross resistance - resistant to single antibiotic(s) using the same mechanism
Multiple resistance - resistant to multiple unrelated antibiotics
What is MRSA?
A
Methicillin Resistant S. aureus
A “superbug”
It has an altered target site, so is difficult to treat
Therefore, only a small list of Gram-positive rods (bacilli) need to be memorised to categorise all bacteria - mnemonic = ABCD L
Actinomyces اكتينو مايسيس
Bacillus anthracis (anthrax) بسيليس انثرسيس
Clostridium كلا ستري ديي ام
Diphtheria: Corynebacterium diphtheriae. (dip.thee.ree.uh)
Listeria monocytogenes لستيريا مانو سايتاجنيس
Remaining organisms are Gram-negative rods, include
Escherichia coli
Haemophilus influenzae
Pseudomonas aeruginosa
Salmonella sp.
Shigella sp.
Campylobacter jejuni
mechanism of resistnace aganist
Penicillins
Bacterial penicillinase (β-lactamase) cleaves β-lactam ring
mechanism of resistnace aganist Cephalosporins
Changes to penicillin-binding-proteins (PBPs), which are types of transpeptidases*
mechanism of resistnace aganist
Macrolides
Post-transcriptional methylation of the 23S bacterial ribosomal RNA
mechanism of resistnace aganist
Fluoroquinolones (2)
Mutations to DNA gyrase topoisomerase and efflux pumps which reduce intracellular quinolone concentration
mechanism of resistnace aganist
Tetracyclines
Increased efflux of the bacteria by plasmid-encoded transport pumps, ribosomal protection
mechanism of resistnace aganist
Aminoglycosides
There are three mechanisms of aminoglycoside resistance: reduced uptake or decreased cell permeability, alterations at the ribosomal binding sites, or production of aminoglycoside modifying enzymes- acetyltransferases, adenyltransferases and phosphotransferases
mechanism of resistnace aganist
Sulfonamides
competitively inhibit the incorporation of PABA into folic acid, thereby preventing the synthesis of folic acid.
mechanism of resistnace aganist
Vancomycin
Alteration to the terminal amino acid residues of the NAM/NAG-peptide subunits (normally D-alanyl-D-alanine) to which the antibiotic binds.
antibitotics Inhibit cell wall formation (BETA-lactams)?
- penicillins: binds transpeptidase blocking cross-linking of peptidoglycan cell walls
- cephalosporins modified beta lactation
*
Inhibit protein synthesis: these antibiotics are bateriostatic
- aminoglycosides (cause misreading of mRNA)
- chloramphenicol
- macrolides (e.g. erythromycin)
- tetracyclines
- fusidic acid
All are bacteria which inhibit protein synthesis
Inhibit DNA synthesis
- quinolones (e.g. ciprofloxacin)
- metronidazole
- sulphonamides
- trimethoprim
Inhibit RNA synthesis
rifampicin ريفام بسين
Which step cause the purple appearance of G+ in gram stain (cry
Which step causes the pink appearance of G- in gram stain (saf)
Primary dye: A primary stain (crystal violet) is applied to a heat-fixed smear of bacterial culture.
Trapping: Iodide is added as a mordant. This binds crystal violet within the cell wall and traps it there.
Decolorisation: The smear is rapidly decolourised with ethanol or acetone.
Counterstain: A second dye (safranin or carbol fuchsin) is applied to counter stain the sample.
+ Examples of enveloped DNA viruses
+ Examples of enveloped RNA viruses include
+ Examples of non-enveloped viruses include
+ include herpesvirus, poxvirus, and hepatitis B virus.
+ hepatitis C virus, coronavirus, influenza, mumps, measles, rabies, ebola, and retroviruses
+ rotavirus, poliovirus, norovirus and coxsackieviruses.
determine what each indicate ?
Positive HBsAg indicates current infection, which may be either acute or chronic
IgM anti-HbcAg indicates acute infection; IgG anti-HbcAg indicates chronic or resolved infection
Positive anti-HBsAg demonstrates immunity, whether from vaccination or natural infection
Hydrogen peroxide was added to a small sample of the culture, with no observable reaction.
What organism is most likely responsible for this presentation?
All species of streptococcus are catalase negative, so will not produce gas on addition of hydrogen peroxide
What is the diffrent btween lipopolysaccharide and peptidoglycan ?
- lipopolysaccharide are presnet on the outer memebrane of gram negtive bacteria
- peptidoglycan are presented in both G+/- but moslty in G+
Which antibiotics are used from gram positive cover
Glycopeptides
Quellung reaction
(quel-lung)
is the only test which may be used to identify Streptococcus pneumoniae,
what is ASO titre
Antibody titre to Streptolysin O (ASO titre) used to determine recent infection with Streptococcus pyogenes
what does Viridans group Streptococcus (no Lancefield classification) cause
dental infections,** endocarditis**, abscesses
All species of streptococcus are catalase negative True/Flase
True
Penciline allergy would lead to the symptons of
anapylaxis
* symptoms include unable to speak and starts to gasp for air
main sid effect of aminoglycoside are
nephrotoxicity and ototoxicity
untreated sort throat infection can lead to
- Rheumatic fever:
- Scarlett fever
- Post streptococcal glomerulonephritis (PSGN)
side effect of vancomycine
Vancomycine : side effect include damages kidneys, occasionally causes ‘red man syndrome’ (allergy) include rash with more eosinophilia, and low neutropenia
* Can only be given IV
Which of the following statements is correct regarding bacterial toxins?
Endotoxins are only produced by Gram positive bacteria
Excessive release of endotoxin causes toxic shock syndrome
Exotoxins do not activate the host adaptive immune response
Endotoxin is a major pathogen-associated molecular pattern (PAMP) which activates the host innate immune response
Endotoxin is secreted by all bacterial cells
Endotoxin, or bacterial lipopolysaccharide (LPS), is a pathogen-associated molecular pattern (PAMP) recognised by toll-like receptor 4 (TLR4), part of the innate immune system. Recognition results in the toxic biological effects of endotoxin, notably local inflammation and fever. Large amounts of endotoxin can cause a massive pro-inflammatory reaction and endotoxic shock
Shiga Toxin producing wich exotoxin ?
You have two example of an exotoxin linked to C. difficile, that damage membrane and Shiga/Vero toxin produce strains (S/VTEC) that also damge GI tract epithelial.
So what a toxin is, protein component to components that cause damage outside the bacteria in the host/environment.
Endotoxin is not really a toxin its a series of components from the outer surfaces of the Gram-negative cell wall, that you think of as being the predominant material the Lipopolysaccharide or LPS. Its immunostimulatory and key factor in Gram-negative sepsis.. the condiiton you have been briefly introduced too. I would add the key learning outcome is that you can contrast the two, i.e. identify that the endotoxin is not a really a toxin.
In the context of antibiotic resistance what are these process (3)
- Internal mutations e.g. point mutations, insertions, deletions, transpositons etc
- Acquisition of foreign DNA from plasmids, transposons or bacteriophages
- Alteration of bacterial membranes: prevents antibiotics entering bacterium
Efflux Pumps
are transport proteins involved in the extrusion of toxic substrates (including virtually all classes of clinically relevant antibiotics) from within cells into the external environment.
Commonly occurs against tetracyclines and fluoroquinolones, macrolides.
Mehtods of antibotic resistance with exmaples (4)
Efflux Pumps e,g tetracyclines and fluoroquinolones, macrolides.
Alterations of ribosomal target sites. antiribosomal agents e.g. tetrayclines, macrolides, clindamycin, aminoglycosides
Alterations of cell wall precursor targets. glycopeptide antibiotcs e.g. vancomycin, enterococci/staph aureus.
Alterations of critical enzymes
.
Alterations of critical enzymes. e,g, alteration of penicillin binding proteins prevents binding of beta-lactam antibiotics, epseically in streptococci and staph aureus.
Penicillin is only used for ________
Gram Positive bacteria
Flucloxacillin is usually prescribed for
prescribed for staph and strep skin infections
Glycopeptide antibiotics work by inhabiting protein synthesis True / False
False they Interference with cell wall synthesis
family members’ of :
Aminoglycosides
Quinolones (fluoroquinolones)
Macrolides
Cephalosporins
Gentomycine
ciprofloxacin and levofloxacin
erthromycin , azithromycin and clarithromycin
Cefaclor, Cefadroxil and cefalexin and ceftriaxone
Note that all antiribosmes end with cin however vancomycin is interfere with amino acid of cell wall and
Tetracyclines are also antribosmes but don’t end with cin
A Patient has a penicillin allergy, what is likely to be prescribed instead?
Tetracyclines (e.g. doxycycline), quinolones (e.g. ciprofloxacin), aminoglycosides (e.g. gentamicin) and glycopeptides (e.g. vancomycin) are all unrelated to penicillins and are safe to use in the penicillin allergic patient. Especially macrolides (e.g. clarithromycin),
A. Mycobacterium tuberculosis stain well with gram staining true/false
FLASE
Obligate anaerobes
can servive in any oxygenated (aerobic) or no oxygen (anaerobic) environment
Name the test used to distinguish
Staphylococcus species.
Streptococci, enterococci
Gram negative bacteria
coagulative test
Haemolysis test
Lactose for road shape bacteria
fungal infection in the oral cavity is mostly caused by
Candida fungal
- Gram negative cocci that appear in pairs on gram film
Neisseria spp.
- Staphylococcus causes scarlet fever True /False
FALSE its Streptococcus spp.
Syncitia formation in viruses
Some viruses involve in transformation of host cell into begging or malignant
Viral persistence
they may become quiescent (no active replication)
Immune reactivity to viruses include
CD8+ lead to apoposis of infected cell
Neutralisation by IgM and IgG which used in antibody detection methods
Immune reactivity to viruses include
CD8+ lead to apoposis of infected cell
Neutralisation by IgM and IgG which used in antibody detection methods
What does MRSA stand for?
Methicillin-resistant staphylococcus aureus
Which endotoxin in gram negative bacteria can trigger Acute Respiratory Distress Syndrome (ARDS?
lipopolysaccharide (LPS) also known as endotoxin.
When activatedneutrophils release various substances including enzymes and reactive oxygen species that can damage nearby cells and tissues.
enter the lungs and release inflammatory mediators. This is termed Acute Respiratory Distress Syndrome (ARDS), widespread inflammation of the lungs resulting in acute breathlessness that can be fatal.
What kind of bacteria is streptococcus pneumonia (Gram, haemolytic, Group)? Streptococcus pneumoniae is an alpha-haemolytic gram-positive bacterium. It has no Lancefield grouping. What are the immunogenic complications of Group A streptococcus? (3)
Rheumatic fever
Rheumatic heart disease
Acute glomerulonephritis
One difference between Pilus and Fimbrae
Involve in bacterial conjugation
Act as adherent attachment for different type of cell surface
What is common about clostridium , bacillus anthracis
Produce endospores
What is the difference between capsule and slim layer cell envelops
Capsule made of organized polysaccharides , has virulence factor e.g Strep . Pneumonia
Slim layer made of unorganized polysaccharides allow cell adherent e.g pseudomonas.
Which part of the L.PS in G- which cause inflammation ?
And which part of the bacteria do antibodies bind to ?
Lipid A
O-antigen
Where are beta-lactamases found in a bacterial cell?
In the extra cellular space called periplasmic space
Different between G+/-
4 steps of Gram Staging
- Crystal violet
- Apply mordant Iodine
- Apply ethanol
- Apply counter stain Safranin
These Atypical Microbes usually Lack Colour Because Microbes Barely Eat Ramen (these are G- bacteria)
Trypinema , Anaplasmosis , Mycoplasma
Ureaplasma , Leptospira, Chlamdiea , Bartonela , Mycobacteria , Borrelia , Elichia , Ricketsia
a component of the strain of MRSA (Methicillin Resistant Staphylococcus Aureus)
which causes severe skin infection such as necrotising fasciitis?
Panton Valentine Leukocidin
is a cytotoxin associated with highly virulent strains of Staph. aureus causing necrolytic skin infection.
The microbiology film shows circular organisms arranged into lines. Which genus does this organism belong to?
(Streptococci), strep = strips/lines, cocci = circular
This organism produces a golden culture on a blood agar plate. Which organism is this?
(Staph. Aureus), staph aureus classically shows up golden on a blood agar plate. It is the only organism that does this.
virus can stay in the body in a latent state and reactivate to cause disease?
(Herpes Simplex Virus) – Latency is characteristic of a herpetic viral infection. HSV is responsible for recurrent cold sores and genital herpes.
bacteria which is resistant to most oral antibiotics
Pseudomonas aerugniosa
is a gram-necative coccabicallus, which is resistant to most oral antibioticcs.
**Coagulase and catalase positive cocci with a gold aura”
Staphylococcus aureus
Describe the appearance of neisseria meningitidis
**N. Meningitidis is an
aerobic
gram negative coccus
which appears as diplococci.
**
stain pink or red on a Gram stain.
Staphilococci?
Staphylococci are Gram positive cocci that appear round in grape-like clusters under the microscope
The circulating blood volume is decreased in the septic patient
Sepsis is easily treated with antibiotics
True / false
In sepsis there is a decrease in circulating blood volume due to endotoxins causing vasodilation & intravascular fluid to leak into adjacent tissue.
difference between Streptococcus?
and Streptococci & Staphylococci
Streptococcus appears as Gram-positive cocci in chains on Gram stain.
Streptococci and Staphylococci are both Gram-positive cocci, which means that they appear as spherical-shaped bacteria that stain purple on a Gram stain.
Streptococci are often arranged in chains and can be further classified based on their hemolytic properties on blood agar.
Staphylococci, on the other hand, are often arranged in clusters and can be differentiated from Streptococci by their ability to form clusters and by their coagulase activity.
Which cellular component is targeted by beta-lactam antibiotics?
Cell wall
macrolides are excreted by urine true/ false
false the excreted by liver they are lipophlic
what is the difference between G+ and G- cell walls
G+ have thick cell wall with no extra cover
G- thin cell wall with outer membrane cover
Gram-Positive Rods
“corney Mike’s list of basic cars”:
- Corney –Corneybacteria
- Mike’s –Mycobacteria
- List of –Listeria
- Basic –Bacillus
- Cars –Nocardia
Gram-Positive Cocci
- Staphylococcus
- Streptococcus
- Enterococcus
Gram PositiveAnaerobes
“CLAP”
- C–Clostridium
- L–Lactobacillus
- A–Actinomyces
- P–Propionibacterium
Atypical Bacteria
legionsofpsittaciMCQs”:
- Legions –Legionella pneumophila
- Psittaci –Chlamydia psittaci
- M –Mycoplasma pneumoniae
- C –Chlamydydophila pneumoniae
- Qs –Q fever(coxiella burneti)
When learning antibiotic coverage I used this stepwise process of escalating antibiotic treatment in a hospital patient to remember what antibiotics covered what bacteria
- Start withamoxicillinwhich coversstreptococcus,listeriaandenterococcus
- Switch toco-amoxiclavto additionally coverstaphylococcus,haemophilusande. coli
- Switch totazocinto additionally coverpseudomonas
- Switch tomeropenemto additionally coverESBLs
- Addteicoplaninorvancomycinto coverMRSA
- Addclarithromycinordoxycyclineto coveratypical bacteria
- Viral persistence
- refers to the ability of certain viruses to remain in the body for extended periods of time, either by
- becoming quiescent (no active replication)
- or by causing chronic infections.
When you can prescribe antibodies
Dermatology
* Trauma, Folliculitis, abscess, cellulitis
Urinary Tract Infections
* Catheter
* Age
* Pain, blood, cloudy, protein
Respiratory Tract Infections
* Sore throat
* Otitis media
* Sinusitis
* Pharyngitis
Urgent Scenarios include;
* Sepsis
* Cellulitis
* Meningitis
* Infective Endocarditis
Mecahnism of action of pencillin
Beta-lactam ring to inactivate cell wall transpeptidases?
, appear as Gram positive spherical cells arranged in grape like clusters.
D. Staphylococcus
yellow urethral is due to what type of route of infection
sexual intercourse
A 30 year old male has jaundice and deranged liver function tests 3 months after a holiday overseas. He admits to getting a new tattoo on holiday, in an unlicensed tattoo parlour for a dare
This is most likely to be hepatitis B, spread by blood to blood contact on improperly sterilised equipment, the incubation period is 6 weeks to 6 months and about half of infected adults have jaundice.
flagella’ on the bacteria is used for
B. Protein molecules that extend from the surface of bacteria & generate movement
microbiome’
Th genetic material associated with all the micro-organisms colonising the body
Malaria is caused by
a protozoa of the genus plasmodium
A. A prokaryote that contains a single cytoplasmic membrane surrounded by a relatively thick multi-layered cell wall that often contains a secondary polymer in addition to peptidoglycan. this describe a gram
G+
antibiotic that is taken up in an inactive form and reduced in the cytoplasm of the micro-organism leading to DNA damage.
D. Metronidazole (Nitroimidazole)
In which scenario would ‘transmission based’ rather than ‘standard’ infection control be appropriate?
A. Attending a patient consultation for an individual who has tested positive for Escherichia coli bacteremia
B. Attending a patient consultation for an individual who has tested positive for Staphylococcus areus bacteremia
C. Attending a ward where patients suffering with C. difficile infections have been identified
D. Receiving an individual who has returned from holiday showing symptoms of Middle-Eastern Respiratory Syndrome (Coronavirus)
E. When dealing with a catheterised patient in an ICU ward
Correct Answer(s): C
Justification for correct answer(s): Transmission-Based Precautions are the second tier of basic infection control and are to be used in addition to ‘Standard Precautions’ for patients who may be infected or colonized with certain infectious agents for which additional precautions are needed to prevent infection transmission.
Which virus is commonly associated with malignant epithelial tumours in humans?
Human papilloma virus
macrophages relase
Pyrogen = induces fever
