staphylococci

Question 1

• staphylococcus is a genus in gram — bacteria and it appears to be – shaped and from in —-
• they are —
• traditionally divided into – groups based on their ability to —-
  1- —– staphylococci ( S.aureus) can colonise nasal passages and other moist skin areas ( ex. axilla , groin )
  2- —- staphylococci ( >20 other species)
  are common in human skin commensals ( ex. S. epidermidis)

Answer 1

• positive
• spherical ( cocci )
• forms in clumps/ clusters
• facultative anaerobes
  -2 groups
• ability to clot plasma ( the coagulase reaction/test)
• Coagulase-positive staphylococci
• Coagulase-negative staphylococci

Question 2

-A laboratory test used to differentiate S. aureus (coagulase +ve) from other staphylococci (negative) ——
- —– is an enzyme that can cause blood clot formation (converting fibrinogen to fibrin) which allows the bacteria to coat its surface w — and possibly resists —

Answer 2

• coagulase test
• coagulase
• fibrin
• phagocytosis

Question 3

-Used to differentiate staphylococci from streptococci (also a Gram-positive coccus) —–
-presence of a —- is determined by the ability of the bacteria to reduce — into water and oxygen which results in the production of —-

Answer 3

• catalase test
• catalase ( aka an enzyme )
• reduce hydrogen peroxide
• bubbles
  ( staphylococci = catalase + )

Question 4

• staphylococcus aureus is found in —– and about —– healthy humans colonised.
• its increased with:
• its distinguished as being — or resistant to —–
  1- Resistance to usual treatment results from production of an —–
  2- usually a — infection , — at higher risk ( colonisation vs infection )
• can also be resistant to other —-
• in hospital:

Answer 4

• moist skin folds, mucosal surfaces, nasopharynx
• 20-40%
• increased if:
• Diabetes mellitus
• Injecting drug use
• Where a foreign body/implant is present
• methicillin-sensitive (MSSA) or
  resistant (MRSA)
• altered penicillin-binding protein (PBP2a)
• healthcare associated infections
• elderly
• antimirobial classes
• isolate / cohort w contact precautions

Question 5

S. aureus pathogenesis:
- portal of entry:
1——
2- —– by:
- a —- in a skin or from enters through —–membranes allowing access to adjoining tissue

• attaches to cells by:
  1- —- which facilitates attachment
  2- —- as it inhibits —- and facilitates — to implants
  3- —– biding protein which is — , its for the attachement to — and —-
  4- —– ex: — which promotes collagen attachment and found in strains that causes —–

Answer 5

• ingestion
• penetration
• break
• mucous membrane
• surface cell
• capsule
• inhibits chemotaxis and phagocytosis
• facilitates the adherence to implants
• fibrin/fibrongen binding protein which is a clumping factor
• blood clot and traumatised tissue
• matrix binding protein
• adhesins
• osteomyelitis or septic arthritis

Question 6

s. aureus pathogenesis :
-it can invade/defeat the —- which causes inhibition of —- with the survival within —–
- production of —- that promotes —- as:

Answer 6

• immune ssytem
• phagocytosis
• within phagocytes
• extracellular substance
• invasion
• invasins and enzymes

Question 7

S/ aureus can can damage to the host cells by:
1- — damage through —-
2- —
3- — as:
- —- which are super antigens
- —–
- —– 8 antigenic type ( A-E , G-I) causes food poisoning and will be converted to GIHEP module
- —- toxins which causes scalded skin syndrome
- others as :
S. aureus can also cause damage by getting out and spread further to:

Answer 7

• direct damage by peptidgoglcycan wall
• enzymes
• toxins
• exotoxins
• toxic shock sydrim toxin (TSST-1)
• endotoxin
• exfoliative toxin
• cytokines ( alpha beta leukocidin _)
• person-to-person: – direct contact via skin carriage, especially hands
• environment: shed on to surface

Question 8

classification of staphylococcal infection:

Answer 8

1. Skin & soft tissue
2. Systemic – invasive
3. Toxin-mediated
   -a) Food Poisoning / Gastroenteritis
   - Short incubation period,
   self-limiting
   - Covered in GIHEP module
   - b) Scalded Skin Syndrome
   - c) Toxic Shock Syndrome

Question 9

systemic s.aureus infection:

Answer 9

• Bloodstream infection (BSI)
• Endocarditis
  – Usually secondary to BSI
• Bone/joint infections
  – Ex. septic arthritis, osteomyelitis
• Deep abscesses, e.g. brain, spine, psoas muscle
• Pneumonia
  – Risk factors: viral respiratory infection, cystic fibrosis, ventilation,
  aspiration

Question 10

• toxin mediated : scaled skin syndrome:
  1- spectrum of — skin disorder:
  has localised —- , generalised —- of entire body surface , —- usually spared
  2- —- toxin by which these toxins are spread —- from localised source , split — in skin layer ( middle layers )
  3- most common in —-
  4- its —-
  5- mortality: –

Answer 10

• superficial blisering
• blister
• exfoliation
• mucous membrane
• heamatogenously
• intracellular bridge
• in children less than 6 yr mainly in neonates , immunuspressed adults and Renal failure
• its contagious
• Children <3% / Adults up to 60%

Question 11

• scaled skin syndrome:
  1- skin extremly —
  2- large patches of — slide off underlying layer at the slightest pressure — sign
  3- complication due to —–
  4- managemt:

Answer 11

• painful
• necrotic epidermis
• nikolyski sign
• sepsis , 2ndary infection , dehydration
• management:
• Rehydration
• Wound care
• Antimicrobial treatment

Question 12

Toxin-Mediated: Staphylococcal Toxic Shock Syndrome (TSS):
1-TSS toxin-1 acts as a —- –>
massive —– release
2- Historically associated with —-
3- its —— , —– , —– onset :
- ——
- —–
4- other organ involved:

Answer 12

• superantigen
  -cytokines
• high absorbency tampons
• rapid , dramati , fulminant onset
• pyrexia and hypertension
• rash w subsequent desquamation,
  especially on palms and soles
• other organs involved:
  – Renal failure
  – CNS (disorientation without focal
  neurological signs)
  – Muscular (severe myalgia, increase in CK)

Question 13

labatory diagnosis:
1- day 0 aka — :
2- day 1+ aka —- :
3- 24 hours later aka — :
4- 24 hours later aka — :

Answer 13

1- patient specimens ( blood culture for example ) –> incubate at 37 degree c
2- postive signal –>
* Gram stain; bunches of grapes
* Set up culture plates in lab
* Team reviews patient
* ? PCR for earlier confirmation
3- culture result —>
* Read agar culture plates
* Coagulase test
* Phone team/patient reviewed
4- antibiotic suspeciability results –?
* Alter empiric antibiotic therapy as
appropriate
* If MRSA – infection control
precautions & decolonisation

Question 14

management of s.aureus infection:

Answer 14

1. History, especially timing and presentation of symptoms
2. Clinical exam
   a) Focus on a possible source or evidence of the spread of
   infection if systemically unwell
   b) Be sure to examine:
   a) Skin: IV line sites or other indwelling devices, surgical wounds,
   soft tissue infections or abscesses
   a) Remember scars can indicate implantable devices or joint or valve
   replacements
   b) CVS: evidence of known or new / changed murmur on
   auscultation
   c) Musculoskeletal: new bone or joint pain, reduced range of motion
   or limp, swelling, loss of function
   c) Always consider the possibility of deep-seated infection
3. Investigations: (depends on the clinical presentation)
   * General bloods: FBC, U&E, CRP, lactate
   * Microbiological (specimen will depend on infection site)
   – Abscess - pus or tissue better than skin swab
   – BSI – blood cultures
   – Pneumonia – sputum, broncho-alveolar lavage (BAL)
   – Septic arthritis – joint fluid
   – TSS (next slide)
   – Food poisoning – food (not stool)
   * Other investigations (as relevant):
   – Imaging (ex. CXR, CT or MRI scans, Echocardiogram (ECHO))

Question 15

TTS 0 investigation and management:
1- investigation:
- —- if febrile or systemically unwell which is rarley —-
- —- for culture if skin lesion
- other swabs for culture:
2- managemt:
- — quickly
- —– and —- input
- rapid —-
- source control :

Answer 15

• blood culture
• positive
• wound swab
• abcess , cervix/vagina
• recognise it
• Resuscitation & critical
  care input
• rapid IV antimicrobials
• sources: Debride infected or
  necrotic wounds, drain
  abscess etc

Question 16

antibiotic treatment:
1- Choice, route & duration of treatment depends on the —-
- mild infection as — :
- skin/soft tissue infection as respirtsoty tract infection :
- blood stream infection :
- complication infection as (endocarditis, septic arthritis,
osteomyelitis): —-
2- — for suspecitble MMSSA and its the 1st generation cephalopsorin (e.g. cefazolin) also an option
3- —- if MRSA and or its alts as:
3- if bloodstream infection look for sources:

Answer 16

• site and complexity of the infection
• as boil has no treatment
• 7 days
• 14 days
• at least 4 weeks but maybe longer
  -Flucloxacillin
• Vancomycin or Teicoplanin (glycopeptide) , alt as: (daptomycin, linezolid, tetracyclines)
• ECHO, radiology & repeat blood cultures after commencing
  antimicrobial treatment to confirm blood is now sterile

Question 17

• Skin infections & necrotizing
  pneumonia
• Younger, healthier patients
• Less antibiotic resistant, but
  more virulent
• Certain strains, e.g. USA300,
  still more common in North
  America
  are all under —-

Answer 17

community acquired MRSA

Question 18

coagulase-negative staphylococci :
1- natural inhabitants of —-
2- much —- than s.aureus and rarely — in health individuals
- S. epidermidis infections often associated with —- example:
- S. saprophyticus causes —-

Answer 18

skin and mucosa
less virulent
rarely pathogenic
prosthetic devices e.g. Joint replacements, prosthetic valves, pacemakers
urinary infection
( check slide 26 important for pathogenesis )

Question 19

S. epidermidis infections (Devices) :
1- blood stream infection often – to IV lines
2- — : prosthetic valves
3- —- infection
4- continuous —-
5- —

Answer 19

• 2ndary
• endocarditis
• Prosthetic joint infections
• Continuous ambulatory peritoneal dialysis peritonitis
• Ventriculitis / shunt-associated
  meningitis

Question 20

Diagnosis & Management of CoNS:
1- diagnosis;
2- managemt:
- —- : often the prosthesis must come out for effective treatment aka —
- — material
- Coagulase-negative staphylococci often —– including —-
- —- is usual empiric treatment
- Indication & duration of treatment depends on —–

Answer 20

Diagnosis
Often patient not particularly systemically unwell
1. History and examination
2. Blood cultures (at least two sets)
- source control
- biofilm
- culture prosthetic material
- antibiotic resistant includes: methicillin/flucloxacillin
- on location of infection & if prosthetic material can be removed

Question 21

true or false:
Biofilm formation. CoNS e.g. S. epidermidis and S.aureus (including MRSA!!) are extremely good at
attaching to surfaces and producing biofilms

Answer 21

true

Question 22

preventing staphyloccocal infection:

Answer 22

1-Prevent transmission
from patient-to-
patient:
* Hand hygiene
* Environmental and
equipment hygiene
* Transmission-
based precautions
for MRSA:
* Isolate/cohort
* Contact
precautions:
gloves,
apron/gown
2- protect skin barrier:
* Prevent pressure sores
* Diabetic foot care
3- Care of wounds and surgical site
4-Care of intravenous catheters:
* Don’t put them in unless needed
* Review the ongoing need daily
* Remove as soon as possible
* Look after them properly

Question 23

summary of syaphyloccoi :
1- +ve ( s.aureus)
- —- of population carry s.aureus without infection
- most common cause of infection:
- — factors ++
- treatment w —
2- -ve
- —– : coloniser of skin and mucosa
- is – pathogenic in healthy individuals
- s. epidermis infections are associated w —- and empiric treatment w —- and the source control through —-
- S.saprophyticus – >

Answer 23

• 20-40%
• skin and soft tissue , systemic , toxic mediated
• flucloxacillin (MSSA) or vancomycin
  (MRSA)
• normal flora
• rarely
• prosethic devices
• vancoymic as resistance is common
• source control by remove device or by biofilm
• UTI