Surgical Microbiology Flashcards
Relation of oxygen with staphylococcus aureus
Facultative anaerobe
Gram test of staphylococcus aureus
Gram positive
blood agar plates test for staphylococcus aureus
Haemolysis
Catalase test for staphylococcus aureus
positive
carriers state of staphylococcus aureus
20% of populations are long term carrier
Result of exotoxin of staphylococcus aureus
toxic shock syndrome
entero toxin of staphylococcus may cause
gastroenteritis
Does staphylococcus have any toxins
Yes
Exotoxin and enterotoxin
Treatment of infection with staphylococcus aureus
Ideally treated with penicillin
How do many strains of staphylococcus aureus now resistant
through beta Lactamase production.
Why penicillin may be ineffective in case of infection with staphylococcus aureus
many strains now resistant and in the UK less than 5% of isolates are sensitive to penicillin.
What does the mec operon gene do?
mecA is a gene found in bacterial cells which allows them to be resistant to antibiotics such as methicillin, penicillin and other penicillin-like antibiotics. The bacteria strain most commonly known to carry mecA is methicillin-resistant Staphylococcus aureus (MRSA).
What are Penicillin-binding proteins
Penicillin-binding proteins (PBPs) are bacterial enzymes that play a key role in the biosynthesis of cell walls.
PBPs are membrane-associated proteins that bind to penicillin and other β-lactam antibiotics.
Importance of Penicillin-binding proteins
PBPs are inhibited by β-lactam antibiotics
Common cause of cutaneous infections and abscesses and why
Staphylococcus aureus because 20% population are long term carriers on skin
Gram test of streptococcus pyogens
Positive
colonies of streptococcus pyogens
forms chain
What is Lancefield grouping
Lancefield grouping is a method for classifying streptococci based on the antigens in their cell walls. The system is named after Rebecca C. Lancefield, who initially divided streptococci into groups A and B in 1928. Today, the system includes groups A through H and K through V.
types of hemolysis in blood agar media
Alpha-hemolysis: Partial hemolysis that produces a wide zone of complete hemolysis with blurred edges
Beta-hemolysis is complete hemolysis. It is characterized by a clear (transparent) zone surrounding the colonies
Gamma-hemolysis: Non-hemolysis, where there is no lysis or clearing
Delta-hemolysis: A narrow zone of incomplete hemolysis with blurred edges
Hemolysis by streptococcus pyogens in blood agar
Beta/complete
Is streptococcus pyogens a? part of normal skin microflora
Rarely
Catalase test of streptococcus pyogens
negative
Releases a number of proteins/ virulence factors into host and their effect
hyaluronidase, streptokinase which allow rapid tissue destruction
superantigen of streptococcus pyogens
pyogenic exotoxin A which results in scarlet fever
Treatment of streptococcus pyogens
Remains sensitive to penicillin, macrolides may be used as an alternative.
Mechanism of macrolides
Macrolides are antibiotics that inhibit bacterial protein synthesis by binding to the bacterial 50S ribosomal subunit
Which drugs are macrolides and their use
Macrolides are a class of drugs used to manage and treat various bacterial infections. Azithromycin, clarithromycin, and erythromycin are commonly used to treat infections like pneumonia, sinusitis, pharyngitis, and tonsillitis.
Escherichia coli type
rod
Gram test for E coli
Negative
Relation of oxygen with E coli
Facultative anaerobe
Due Escherichia coli produce spores
non sporing
Location of E coli
Wide range of subtypes and some are normal gut commensals
lethal toxins of E coli with effect
O157 subtype may produce lethal toxins resulting in haemolytic-uraemic syndrome IN CHILDREN
Early symptoms of HUS (Haemolytic–uraemic syndrome)
vomiting, bloody diarrhea (loose stool/poop), stomach pain, fever, chills, and headache
Late symptoms of Hemolytic–uremic syndrome
(HUS) is a group of blood disorders characterized by low red blood cells, acute kidney injury (previously called acute renal failure), and low platelets.
Effect of Enterotoxigenic E-Coli
produces an enterotoxin (ST enterotoxin) that results in large volume fluid secretion into the gut lumen (Via cGMP activation)
moderate invasive Vs significant invasive
E coli to intestinal cells and cause structural damage
Enteropathogenic- moderate
Enteroinvasive- significant
Feature of invasion of gut by E coli
enteritis and large volume diarrhoea together with fever
Antibiotics for E coli
Fluoroquinolones: Such as ciprofloxacin
Macrolides: Such as azithromycin
Why penicillin may not work against
E coli
They are resistant to many antibiotics used to treat gram positive infections and acquire resistance rapidly and are recognised as producing beta lactamases
Shape of Campylobacter jejuni
Curved
gram test for campylobacter jejuni
Negative
Does campylobacter jejuni produce spore
non sporulating
Relation of campylobacter jejuni with diarrhoea
One of the commonest causes of diarrhoea worldwide
What is enteritis
Enteritis is inflammation of the small intestine
How campylobacter jejuni is related to appendicitis
Remains a differential for right iliac fossa pain with diarrhoea
Good thing about treatment of campylobacter jejuni
Self limiting infection so antibiotics are not usually advised. However, the QUINOLONES (cipro/moxi) are often rapidly effective
What are quinolone drugs
Currently there are four quinolone generations: nalidixic acid, ciprofloxacin, levofloxacin and moxifloxacin
Shape of Helicobacter pylori
helix shaped rod
Gram test of Helicobacter pylori
Negative
Relation of oxygen with Helicobacter pylori
microaerophillic
How hydrogen can be a source of energy for Helicobacter pylori
Produces hydrogenase that can derive energy from hydrogen released by intestinal bacteria
Can Helicobacter pylori move
Flagellated and mobile
Which Helicobacter pylori may cause ulcers
Those carrying the cag A gene may cause ulcers
Dual effect on gastric acid by Helicobacter pylori
1.Helicobacter pylori (H. pylori) uses urease to neutralize gastric acid and colonize the stomach:
2.H. pylori infection has been found to consistently elevate plasma gastrin concentrations.
How does Helicobacter pylori neutralise the gastric acid and why?
It secretes urease that breaks down gastric urea> Carbon dioxide and ammonia> ammonium>bicarbonate (simplified!) The bicarbonate can neutralise the gastric acid.
To save itself
How does Helicobacter pylori increase gastric acid production and result
colonises the gastric antrum and irritates
These patients will develop DUODENAL ulcers
When and what will happen with the acid neutralising ability suppresses the acid producing ability of Helicobacter pylori
In those with more DIFFUSE H-Pylori infection gastric acid levels are lower and ulcers develop by local tissue damage from H-Pylori- these patients get GASTRIC ulcers.
Tests to diagnose helicopter pylori
1.Serology (approx. 75% sensitive).
2.Biopsy urease test during endoscopy probably the most sensitive.
Risk of Helicobacter pylori
In patients who are colonised 10-20% risk of peptic ulcer, 1-2% risk gastric cancer, <1% risk MALT lymphoma.
illness phases of fasciola hepatica
two
symptoms of acute phase is fasciitis hepatica
immature worms begin penetrating the gut, causing
fever
nausea,
swollen liver,
skin rashes and
extreme abdominal pain
Symptoms of chronic phase of fasciola hepatica
occurs when the worms mature in the bile duct, and can cause
intermittent pain,
jaundice and
anemia.
Treatment of fasciola hepatica
with triclabendazole. Some patients may need ERCP
Which pus has a pungent aroma
Bacteroides fragilis
ENT feature of glandular fever
combination of pharyngitis and tonsillitis is often seen in glandular fever
Kigella age group
children aged 6 months to 4 years
Disease caused by Kigella kingae
infectious discitis (D) and infectious spondylodiscitis (SD)
risk of wound infection in case of uncomplicated surgery
around 3-5% (Pasquali et al and Matsui et al).
indicative of quinsy
Unilateral swelling and fever
Microscopic colitis
Microscopic colitis is a common condition characterised by normal endoscopic appearances, microscopic features of colonic inflammation and thickening of the sub epithelial collagen layer.
Why Yersinia enterocolitica is DD of appendicitis
Yersinia can be mistaken for acute appendicitis due to mesenteric lymphadenitis and ileitis.
Cause of plague
Yersinia pestis
most common organism affecting previously abnormal heart valves.
Streptococcus viridans
most common cause of bacterial tonsillitis
streptococcal organisms.
Which organism tends to colonise plastic devices
Staphylococcus epidermidis
What is melanosis coli
Melanosis coli is a benign pigment disorder in which the lining of the large intestine, or colon, turns black or brown, usually as a result of laxative use.
This may occur as a result of laxative abuse and consists of lipofuschin laden macrophages that appear brown.
Which diarrhea/septicemia is associated with carcinoma of the colon
Streptococcus bovis
most common cause of bladder calcification by infection worldwide
Schistosomiasis
Location is Schistosoma mansoni infection
typically resided in the colon from where it is excreted.
Disease causing bulls neck appearance
Infection with diphtheria
In which infection the oropharynx is covered with a thick grey membrane which bleeds following attempted removal.
Infection with diphtheria
Organism containing sulphur granules
actinomycosis
Ototoxicity is a recognised adverse reaction with which antibiotics
the aminoglycoside
Best treatment of infective dislocation of total hip replacement
Removal of metal work implantation of gentamicin beads and delayed revision is the mainstay of managing this complication after 4 weeks. In earlier infections, linear exchanges covered by prolonged courses of antibiotics can be used.
Birds are a recognised reservoir of which organism causing painful diarrhea
campylobacter jejuni
Which drugs are aminoglycosides?
gentamicin, tobramycin, amikacin, plazomicin, streptomycin, neomycin, and paromomycin
Use of Chloramphenicol
superficial eye infections such as bacterial conjunctivitis, and otitis externa
Causes of Discitis in children
Staphylococcus aureus,
Kingella kingae(6 months to 4 years), Mycobacterium tuberculosis, Brucella
Treatment of Discitis in children
Initial treatment is with broad spectrum intravenous antibiotics that cover s aureus, children aged 4 months to 6 years need cover for Kigella.
ESR & WCC in septic arthritis
The WCC should ideally be > 12 and the ESR > 40 to suggest septic arthritis.
Relation of virus with synovitis
Viral illnesses can be associated with transient synovitis
Shenton’s line
Shenton’s line should be a smooth, continuous arc that connects the femoral neck to the superior margin of the obturator foramen.
Why prophylactic use of antibiotics is not appropriate for Mayo repair
As the Mayo repair does not involve implantation of prosthetic mesh the use of antibiotics is not appropriate.
Solution for skin preparation before incision
Alcoholic chlorhexidine
