Day 6: Invasive meningicoccal disease, Vaccines for N. meningitidis and Biofilms, antimicrobials resistance Flashcards
HC 14, 15, 16
HC14: Character N. meningitidis
- Gram-negative diplococcus
- Natural habitat: human nasopharynx
- At 5-30% it is culturable from population > not pathogenic > carriers
Carriage N. menigitidis is associated with age: peak at ..
Around 19 y/o: asymptomatic carriage
Peak of carriage N. meningitidis at age because
Behaviour, not age (19)
> crowds, kissing, bar/disco, active and passive smoking
> risk factors are strongly and independently linked to risk for meningococcal carriage
> whole relationship with age is gone when adjusted for behaviour.
Changes is risk factors N. meningitidis over years
- Less smoking
- Less crowding
- Carriage decreased among teenagers
In 0.01% of Nm carriers: invasive pathogenesis and disease:
Septicemia (blood disease) and meningitis (meninges inflammation)
Invasion Nm
From nasopharyngeal cavity across epithelium to blood
> septicemia or even further to reach cerebrospinal fluid: meningitis
Meningococcemia
Meningococci in bloodstream
> sepsis
> petechial rash: round spots in skin from bleeding: cannot be pushed away: problematic stage
> Disseminated intravascular coagulation (DIC): abnormal blood clotting
» ischemic tissue damage, purpura fulmicans, too little blood to extremeties: dies off, amputations
> meningitis
High morbidity rate in IMD (invasive meningococcal disease), why>
Residual damage after cured
> limb loss
> cognitive deficits
> hearing loss
> seizure disorders
Is there vaccination for Nm?
Yes, in national program
Spread from adolescents peak incidence Nm to risk groups:
Eldery and infants
Effect COVID-19 on Nm incidence
Decreased > more distance held
Surveillance Nm disease in Netherlands
- Mandatory notification
- Laboratory surveillance
> look at characteristics of disease and monitor it
> isolates from blood or CSF (cerebrospinal fluid)
> Antibiotics given to patients immediately
> negative CSF culture > Molecular methods like PCR
Is there a link between the notifications of Meningococcal disease and laboratory data?
Yes, all linked and mandatory
> coverage >90%
Serogroups Nm
Based on chemical composition of polysaccharide capsule
> protects against effects immune system
> 13 serogroups
> A, B, C, X, Y and W cause >95% of IMD
> in Europe: B and C most prevalent
Typing methods Nm
- Phenotype
> serogroup, PorA epitope sequencing, FetA epitope sequencing - Genotype
- Multi locus sequence typing using MLST
PorA
Protein in gram negatives like Neisseria meningitidis
> on outer membrane: porine A protein
» transport nutrients, transmembrane protein
> two variable loops in PorA: VR1 and VR2
» mutates constantly to hide from immune system with different epitope
» use foward and reverse primers for both VR1/2 to deteminate them
» into public database
FetA
Outer membrane protein of Nm
> one variable epitope: VR (variable region)
> beta barrel in membrane, VR loop sticks out
Typing of Nm isolates: annotation
Nm: B: P1.7,4:F5-1
> Nm: Neisseria meningitidis
> B: serogroup
> P1 (PorA) 7,4 > VR1 type 7, VR2 type 4
> F5-1 > ForA type 5-1
Multi Locus Sequence Typing (MLST)
- Sequence seven loci
> housekeeping genes: essential genes for viability and are present in all strains because essential
> number assigned for each allele
> combination of allele numbers > sequence type (ST) > a number like ST81
When different ST
When one of the housekeeping genes has a different allele
Single Locus Variant (SLV): example stain 2 of strain 1
Differs only one of the alleles from strain 1 (original)
Clonal complexes (CCs)
Any ST that matches the central genotype at 4 or more loci considered in the MLST.
Visualize the relatedness in MLST
BURST algorithm
> Circle is the CC, around the dots, the STs
> everything within the circle is from the CC
In the BURST pictures of MLST database, there are (within CCs) big dots with a flower like circle around it. What is it.
A central genotype (ST) with SLVs (single locus variants) around it.
Which CCs overrrepresented in IMD patients
CC41/44 and CC32
> specific characteristics that make them more virulent
CC53 and CC35 are almost never in IMD patients, why?
Often unencapsulated: vulnerable for immune response
The CC distribution among IMD patients is…
Dynamic, CCs disappear and appear in IMD patients
> different dominant clones
> is related to epidemiology (number of cases)
Are the strains of Nm identical to a certain outbreak? How to increase resolution to answer the question
Whole genome MLST > identify different strains
first: identify clusters or outbreaks
Which phenotypic and genotypic analyses are prerequisite to investigate vaccine effectiveness and coverage?
- Social behaviour including coronal regulations affect meningococcal carriages and IMD incidence
- Meningococcal surveillance: typing provides insight into epidemiology
- Fine typing of meningococci to identify clusters or outbreaks
HC15: Around 2000, peak incidence in … and decrease in …
MenC peak
MenB started to decrease
First accepted Nm vaccine
Against MenC
Vaccines Nm
Capsular polysaccharide conjugate vaccines
> Nm cultured > CPS (capsule polysaccharide) extracted > coupled to protein carrier
- Develop immunological memory
- Class switching and affinity maturation
- High affinity IgG
- Effective in infants (not yet developed to react to antigens on sugars, so protein carrier)
MenC vaccination, who?
Infants, 14 mo/o
> and adolescents: herd protection by reducing carriage reservoir: protect infants and eldery: follow up campaign
Continuous caution for Nm is required: rise of IMD cases with serogroup …
W
MenW origin
From England
> MenW CC11 (linked to IMD) from South America to England (not big outbreak) and genetic switch to UK-2013 strains > CC11 UK2013 > spread across Europe (increased chance of carriage)
Meningococcal ACWY multivalent vaccine
CPS conjugated to protein carrier
> MenW peaks cass at infants, adolescents and eldery
> also take mortality rates into account: highest for adeolescents
> Replacement MenC for MenACWY vaccine for 14 mo/o, all 15-18 y/o called up in 2019 and 14 y/o now also in vaccination program
> decreased MenW cases after vaccination
Why did the MenW cases decrease in non-vaccinated groups after vaccination program?
Herd immunity, less carriers and transmission
MenY and MenB cases after the ACWY vaccine
MenY: decrease trend
MenB: no effect
Why is MenB unaffected by vaccinations?
- Capsule polysaccharide is problematic for vaccines
- poorly immunogenic due to mimicry (identical sialic acid in nerve tissue > no auto-immunity wanted)
- different vaccine composition: protein vaccine antigens
Possible solutions against MenB
- Use outer membrane vesicles
- Use other vaccines
Outer membrane vesicle (OMV) strategy for MenB
- Small vesicles of outer membrane which contain components of outer membrane on them contains bacterial components as well
> vesicles used (OMVs), isolate and used for vaccination
> PorA as important protective antigen (however: variable)
» strain specific immunity
» protection from antibodies directed against VR1/2 loops
» include as many PorA as possible in meningococcus and isolate their OMVs
» 3 PorA variants made and 3 strains used: NonaMen
> 80-85% of circulating strains are covered, but vaccine not accepted
Use other vaccines for MenB: Reverse vaccinology
Reverse vaccinology
> Use genome meningococcus
> Genomic-based approach to vaccine development
> Test for antibody response in mice
> Test if they are on surface of meningococcus bacterium
> check if antibodies kill the bacterium
> 3 antigens selected: fHbp, NadA, NHBA
Registered MenB vaccines
- Baxsero
> three components and OMVs - trumenba
> One component, but important variant
Baxsero and antigenic components
4 antigenic components
> fHbp: factor H binding protein: for bacterial survival
> NadA: adhesin, promotes adherence to and invasion of human epithelial cells
> NHBA: heparin-binding: binds heparin, which promotes bacterial survival in blood
> OMV with one variant of PorA in it
» decrease pathogenesis on different steps to help optimize MenB vaccine effectiveness
Trumenba
Single antigenic component but 2 subfamilies
> Subfamily A: 30%
> Subfamily B: 70%
> all meningococcus B targeted: 1 variant of subfamilies A and B
> only fHbp targeted
Is there herd immunity with MenB vaccines?
No, there is no protection for non-vaccinated people as the carriage or transmission is not decreased, just the pathogenesis.
HC16: Which organ is the first barrier for bacteria and fungi
The skin
Which components of the skin are susceptible for infection
- Sweat glands
- Sebaceous glands near hair follicles
- Hair follicles
> can cause infection with penetrance
The composition of microbiota differs per …. of the skin
Location
Human antimicrobial peptides : where and how
In the cells > epithelium, endothelium, leukocytes, platelets
> rapid: storage and secretion, also for intracellular killing when phagocytosis
Human Antimicrobial Peptides are inducible. Transcription after:
- Tissue damage
- Inflammation
- Bacterial products (TLR mediated)
» thus: physiologically very first line of defense
Skin Human Antimicrobial peptides at:
- Sweat glads
- Epidermis
- Sebocytes
- Mast cells
Antimicrobial peptides work … and protective enzymes at the skin barrier work …
Directly ; indirectly
Not all bacteria are reached by disinfectants, what can happen when skin damage
Bacteria release and cause problems > for example under the hair when pulled out
Skin infections in who
Immunocompromised patients
Local skin infections sources
Surgical wound, infuse, oedema, eczema
Systemic skin infection inducing factors
Diabetes, Prednison (immune suppression), leukopenia (low white blood cells)
Impetigo
Krentenbaard
> skin surface infection by S. aureus or Streptococcus pyogenes (Group A streptococcus, GAS) or mixed
Folliculitis
- Infection of hair follicle
- Infection by staphylococcus aureus
Furuncle
Acute necrotic form of folliculitis (S. aureus)
Erysipelas (belroos, wondroos)
- Deeper in skin than Furuncle
- Close to deeper tissues
- Lymphatics can be infected as well
- Mostly legs, sometimes arms and face
- Via skin defect, GAS: streptococcus pyogenes
- eldery, diabetes, edema
- hard to get rid of.
Cellulitis
Infection into dermis and subcutaneous fat
> via skin defect
> S. aureus, GAS
Necrotising fasciitis and myositis
Flesh eating bacteria, into deeper layers
Type 1 Necrotising fasciitis and myositis
From inside out
> post-surgery
> necrosis from fasci (bindweefsel) towards the skin
> initially no skin signs
> often GAS
> also mixed infection aerobe and anaerobe with GAS
Type 2 Necrotosing fasciitis and myositis
Outside in: from skin (cellulitis) to fascii
> mono-infection GAS
> patient severely ill
> extremely painful
> surgery and antibiotics
> 1/3 die
Important skin pathogens
Staphylococcus aureus
Group A streptococcus like Streptococcus pyogenes
Major component S. aureus cell wall
Protein A
> prevents opsonation from occuring
> bind Fc tails of antibodies
> bind antibodies upside down and prevent recognition by immune cells
S. aureus extotoxins
- Exfoliatin cause scalded skin syndrome (SSSS)
- Panton Valentine attracts and destroys leukocytes
- TSST-1 Toxic Shock Syndrome
S. aureus toxins
TSST-1, enterotoxins, alpha hemolysin and others
S. aureus exoenzymes
In order to enter and penetrate
> Hyaluronidase destroys tissues
> Hemolysins destroy red blood cells and release iron
> Coagulase clot formation: form shell of platelets around bacterium to hide from immune cells
> Staphylokinase: dissolves clots when inside their shell to release and propagate pathogen
Invasins of S. aureus
Coagulase, staphylokinase
Adhesins
To attach to host proteins
Inhibition phagocytosis by S. aureus
- Protein A
- Capsular polysaccharide
- Clumping factor A (coagulase)
GAS like Streptococcus pyogenes
- Gram positive cocci in chains
- In throat, infection which can propagate to blood
- SPE A, B and C exotoxins cause the redness of people with this infection
- High fever
- Has M-protein: protein which sticks out against phagocytic cells
Invasins and adhesins of GAS/ S. pyogenes
Invasins:
- Streptolysins; lyse cells
- Streptokinases and protease break structures around bacterium down
- Flesh eating bacteria have proteases which break down entire tissue
Adhesins
> adhere epithelium: Lipoteichoic acid (LTA)
Sources examples Biomaterial-associated infection (BAI)
- Hip prosthesis
- Central venous catheter
- CSF shunt
- Heart valve
- Breast implant
Some biomaterials have higher chances of infection, why?
Connection between the outside and the inside
> like catheters
> need to be switched regularly
Problem removing infected biomaterial
they may grow with the adjacent bone which needs to be removed as well
BAI mostly by…
Often harmless skin bacteria becoming opportunistic like Staphylococcus epidermis
There is a … load of S. aureus needed to cause infection when wound with sutures (hechtingen) than without them
Lower
Elements of pathogenesis of BAI
1. Site of application of biomaterials
> name sites of applications
- External: no surgical wound, no port d’entrée
> urinary catheters
> Endotracheal tubes
> No penetrance of epithelium - Transcutaneous: surgical wound AND port d’entrée
> Intravenous catheters, shunts
> CAPD catheters
> external fixation devices
> like the pins for complicated fractures - Implanted: surgical wound, no port d’entrée
> prosthetic joints like hips and knees
> prosthetic heat valves or pieces
> Pacemakers
> Hydrocephalus shunts
> Brought in, but then closed
Transcutaneous device: intravascular catheter
- Insertion site wound: port d’entrée for skin bacteria
> possible extraluminal infection: from skin
> possible hub contamination: intraluminal: inside catheter
> possible hematogenous infection
> possible contiguous infection from deeper tissues to biomaterial
External device: urinary catheter
- mostly infections on skin nearby
- Natural defense: flushing with urine, but water flow is now removed
Implanted device: total hip
- Skin bacteria introduced during surgery
- Hematogenous infecion possible: bacteria find the prosthetic
- implantation site wound, no port d’entrée (nothing is brought in)
Elements involved in pathogenesis of BAI
2 Biomaterial characteristics
- Texture, surface, hydrophobicity, and charge determinants
> adhesion host proteins and blood platelets
> adherence of microorganisms, directly or to host proteins and blood platelets on the biomaterial.
> biocompatibility: nature of foreign body response
Elements of pathogenesis of BAI
3 Bacterial virulence factors
Adherence by specific adhesins of bacterium
- Biofilm initiated by quorum sensing
- production slime, polysaccaride intercellular adhesin PIA, enzymes from ica operon
Biofilm formation by quorum sensing
Gene expression regulated by population density via paracrine signals
> quorum sensing molecule produced: encapsidation
> extracellular matrix made
icaABCD operon
Intracellular adhesin operon
> insertion sequence transposon (IS256) can jump irregularly in a locus in ica cluster
> mutation to not produce the extracellular material
> from biofilm to no biofilm
Elements of pathogenesis of BAI
4 Host factors predisposing for infection
- Reduced neutrophil phagocytic and respiratory burst activity
> due to presence foreign body (prosthetic): frustated phagocytosis
> due to bacterial components such as Staphylococcus epidermidis extracellular polysaccharide slime
» combined influence of bacteria and biomaterial reduce defense
Elements of Pathogenesis of BAI
- Site of application of biomaterials
2 Biomaterial characteristics
3 Bacterial virulence factors
4 Host factors predisposing for infection
