Microbiology Flashcards
State the components and the functions of the human microbiome
1000 species: bacteria, fungi and viruses
Variability of species between individuals, but a consistent range of functions at given body sites
people never exposed to antibiotics have a bigger range of distinct species making up their microbiome
Where is it?
- on and within our bodies
- at the interfaces between self and non self
- at our interface with the environment
- def of ecosystem: a system formed by the interaction of a community of organisms with its environment
Where is it not: blood lypmh etc. we talk in the lab about sterile sites:
Components:
SITE - SPECIES - PHYLUM:
GI - Bacteroides - Bacteroidetes
Urogenital (female) - Lactobacilli - Firmicutes
Skin - Proprionibacterium - Actinobacteria
Oral - Streptococci - Firmicutes
Nasal - Staphylococci - Firmicutes
May be different levels of bacteria in different areas in different people but still the same physiological functions happen there
WHAT DOES IT DO?
- nutrition
- metabolism
- immune programming - almost definitely does this function - bacteria instruct immune system about pathogens
- inflammatory modulation - speculation with this
- innate immunity - done by out performing pathogens - grow so that bad bacteria can’t grow there instead so in this way it keeps it healthy
- may have something to do with CNS and brain development?
Review the key stages in the acquisition of the human microbiome
Birth is Critical:
vaginal microbiota - first organisms you acquire during birth - vaginal mucous gets squeezed into mouth as it is being squeezed through - first gasp - inhales the mucous and some is swallowed
Prenatal:
Maternal diet, maternal GI and vaginal microbiota, antibiotics
Perinatal:
Mode of delivery, skin, antibiotics
Postnatal
Environment, people, feeding, antibiotics
what is the significance of Proteus, Providencia, and Morganella species in urine
- Associated with renal calculi
- Express urease enzyme which converts urea to ammonia
- Ammonia alkalises the urine, causing precipitation of struvite crystals
what is the significance of yeast in the urine
Candida species from children’s urine should prompt a search for fungal balls in the bladder
These patients require surgical removal of fungal balls
what is a UTI
what is a lower uti and an upper uti
UTI: an inflammatory response of the urothelium to bacterial invasion that is usually associated with bacteriuria and pyuria.
Lower UTI: infection between the urethra and the ureterovesical junction
Upper UTI: infection above the ureterovesical junction
describe the pathogenesis of uti
Infection of the urinary tract occurs when
- Pathogen virulence increases
and/or
- Host defence mechanisms decrease - decreased urine flow
Pathogen factors in UTI:
Uropathogens survive and invade by virtue of their virulence factors
An ‘arsenal of weapons’ against the host:
- Motility mediator – flagella powers bacteria’s directional movement
- Adhesins – fimbria allow attachment to host epithelium
- Invasins – proteases break down host epithelial barrier
- Toxins – destroy host tissues and cause systemic instability
- Immune escape mediators – disguise bacteria from immune recognition
- Biofilm production – shield bacteria from immune attack - live in colonies - communities
Normal flora of the periurethral area (e.g. lactobacilli, coagulase negative Staphylococci) inhibit colonisation with uropathogens Factors which alter this flora: - Systemic antibiotics - Prolonged hospitalisation - Spermicides (nonoxynol-9) - Oestrogen deficiency - pre menstruation and end of fertile period (menstruation) - Low vaginal pH - Low cervical IgA
how would you investigate urethritis
Urine for microbiological culture
Urine or swab for PCR detection of Chlamydia or Gonococcus
Gram stain of a purlulent discharge can reveal gonococcus (Gram negative cocci inside epithelial cells)
name some of the risk factors of cystitis
Ineffective voiding: Bladder outflow obstruction (e.g. prostate enlargement, tumour, clots, cystocoele) Memory impairment (Alzheimer’s disease) Neurological deficit (Stroke, Parkinson’s disease, spinal cord injury)
Smoking:
- Causes a chemical interstitial cystitis
Diabetes mellitus
- Raised urinary glucose feeds bacterial growth
Sexual intercourse
- Delivers pathogens to urethral entry
describe the presentation of cystitis
Urinating that is:
- Painful (dysuria)
- Frequent (urinary frequency)
- Urgent (urinary urgency)
Urine that is:
- bloody (haematuria)
- turbid
- foul-smelling
General/nonspecific symptoms:
- Fever
- Confusion
- Abdominal pain
- these are important in young - can’t tell you what’s happening
- ppl who have cognitive impairment - can’t tell you
- ppl with a catheter in - can’t see urine cuz they aren’t urinating
describe how you would investigate cystitis
Urinalysis
Nitrites, leucocytes, blood
Urine microscopy
Pyuria, bacteriuria
Urine for organisms and sensitivities (O&S)
>100,000 organisms/ml is significant
Imaging Ultrasound or CT renal tracts Indicated if recurrent or complicated cystitis for: Anatomical abnormality Renal stones Tumours
describe the management of cystitis
Good hydration
Glycaemic control in diabetes
Antibiotic therapy: Several oral options available: all taken for 3 days - Nitrofurantoin - Trimethoprim - Pivmecillinam - Cephalexin (useful in pregnancy)
Fosfomycin 3g single dose
describe prophylaxis of cystitis
Genital hygiene
Post-coital voiding
Avoidance of diaphragm/spermicide
Estriol vaginal cream (post-menopausal)
Insufficient evidence for:
Cranberry juice
‘Wiping front to back’
Clothing
describe the risk factors associated with pyelonephritis
Cystitis:
- 50% of cases results in upper UTI - infection rises up
- Ureterovesical junction can be compromised through bladder oedema
Interference with ureter peristalsis:
- Pregnancy
- Stones
- Strictures
describe presentation of pyelonephritis
= Symptoms of cystitis
PLUS classical triad of:
Fevers/rigors
Flank pain
Nausea and vomiting
describe investigation of pyelonephritis
Same measures as for cystitis
(e.g. urine culture and sensitivities)
Blood cultures
Imaging
USS or CT renal tracts
describe management of pyelonephritis
- Resuscitation
- Empirical antimicrobial therapy:
- (after cultures taken) - before you get the results
Several options available:
- IV Piperacillin-Tazobactam
- IV/PO Ciprofloxacin
- IV Gentamicin - Targeted antimicrobial therapy
- (when culture results available) - amend the empirical antibody treatment and make it more specific because you now have the results
what is the difference between a complicated and uncomplicated UTI
Uncomplicated UTI: an infection in a healthy patient with a structurally and functionally normal urinary tract.
Complicated UTI: infection associated with factors that increase the chance of acquiring bacteria and decrease the efficacy of therapy:
- Structural or functional abnormality of the urinary tract
- Immunocompromised host
- Hypervirulent or resistant bacteria
who needs antibiotic treatment for Asymptomatic bacteriuria
Pregnant women:
- x30 risk of pyelonephritis compared to non-pregnant matched patients
- associated with premature labour and low weight babies
Patients awaiting urological surgery or procedure:
- 60% of bacteriuric patients will have bacteraemia post-instrumentation of their renal tract
- 10% of these will develop sepsis
who needs antibiotic treatment for Asymptomatic bacteriuria
Pregnant women:
- x30 risk of pyelonephritis compared to non-pregnant matched patients
- associated with premature labour and low weight babies
Patients awaiting urological surgery or procedure:
- 60% of bacteriuric patients will have bacteraemia post-instrumentation of their renal tract
- 10% of these will develop sepsis
Compare the fundamental differences between a bacterial and a viral
infection
Bacterial:
- they are cells
- adhere to host tissue
- invasiveness - penetrate into the cells and their epithelia
- evasion of host defences - can disguise or cloak themselves
- toxins
viruses:
obligate intracellular parasites - need a cell for the virus to live in
- needs receptor at site of entry to the body
- dissemination - spreading
- multiplication in target organs - this can kill the cell - adds to damage virus is causing
- shedding - enter cell - multiply then leave cell
define serotype
Classification of organisms according to antigenic properties
describe how the gram stain works
needed because bacterial cells are transparent
- first stain is crystal violet and iodine
- these bind to peptidoglycans on the cell wall
- acetone washes away this stain from gram negative but doesn’t wash it away in gram positive
describe how the gram stain works
needed because bacterial cells are transparent
- first stain is crystal violet and iodine
- these bind to peptidoglycans on the cell wall
- acetone washes away this stain from gram negative but doesn’t wash it away in gram positive (because gram positive have thicker peptidoglycan walls and negative have their cell membrane washed away by acetone)
- neutral red is a counter stain
- applied second
- gram positive stays purple because it already has the violet/iodine stain
- gram negative takes up the counter stain and show up pink-red
when classifying bacteria what is the difference between cocci and rods
cocci = ball like rods = longer thinner
these are then gram negative or positive
name some gram positive cocci and rods
name some gram negative cocci and rods
lecture 2 slide 7 on notability
what does a classification of obligate anaerobe mean
has to live in anaerobic conditions
what does a classification of obligate aerobe mean
has to live in aerobic conditions
what does a classification of facultative anaerobe mean
will grow in presence or absence of oxygen
slight preference to low oxygen environments
most medically important bacteria in this category
highlights how adaptive they are
name 5 methods to categorise bacteria
Staining characteristics - gram stain
Growth characteristics- Aerobic/ Anaerobic
Haemolysis on blood agar
Metabolic activity- Coagulase/ Catalase/ Oxidase
Antigenic features - ‘Serotyping’
Nucleic acid molecules - ‘Genotyping’
where might some gram positive cocci clusters be found in the body
Skin, nasal, desquamated squames- dust
where might you find
B-haemolytic Streptococci:
(Lancefield group A, B, G)
Streptococcus oralis Streptococcus pneumoniae
Mouth, upper respiratory tract
where might you find Enterococcus faecalis
GI Tract
where might you find Clostridium tetani Clostridium difficile Clostridium perfringens
Soil. Anaerobic, spore forming, bacteria
where might you find Listeria monocytogenes Bacillus species
Food
where might you find Proprionibacterium acnes
skinf
where might you find Lactobacillus acidophilus
Food, female GU tract
where might you find Neisseria meningitidis
Upper respiratory tract
where might you find Neisseria gonorrhoeae
Genito- Urinary tract
where might you find Haemophilus influenzae
Respiratory tract
where might you find Escherichia coli Klebsiella pneumoniae Proteus mirabilis Salmonella enteritidis
Bacteroides fragilis
Gastro-intestinal tract: mammalian
where might you find Pseudomonas aeruginosa
Aquatic environments
where might you find Campylobacter jejuni
Gastro-intestinal tract: Avian
where might you find Mycobacterium tuberculosis
TB. ‘acid and alcohol fast bacilli’: Respiratory tract
where might you find Legionella Pneumophila
Chlamydia Trachomatis
Mycoplasma pneumoniae
Cell wall deficient bacteria:
- Legionella: aquatic and respiratory tract
- Chlamydia: respiratory and GU tract
- Mycoplasma: respiratory tract
where might you find Treponema pallidum
Syphillis. Spirochaete (spiral bacteria) GU tract
name some DNA viruses, RNA viruses and reverse transcribing viruses
see lecture 2 slide 24 notability
Evaluate the use of white cell count and differential, C-Reactive Protein and Temperature to detect and monitor infection
CRP one of many acute phase proteins: made by the liver and believed to modulate inflammation and tissue repair
These markers can help confirm or refute a diagnosis of infection, but cannot be
definitive.
They may just indicate Inflammation
temp can indicate inflammation
can indicate infection possibly but not always as temp can vary naturally or could be something other than infection such as cancer connective tissue disease or drug reaction
what does transmissibility mean
ability to be transmitted
what is meant by incubation period
the time between exposure to a pathogen and when symptoms are first apparent.
Typically the period taken by the multiplying organism to reach a threshold necessary to produce symptoms in the host
what is meant by infectious period
period infected person can transmit infection to susceptible host
what does transmissibility mean
ability to be transmitted
how contagious it is
what are the cardinal signs of inflammation
Rubor - redness Calor - heat Tumour - swelling Dolor - pain functio laesa - loss of function
define sepsis
‘Sepsis is characterised by a life-threatening organ dysfunction due to a dysregulated host response to infection’
what is the difference between sensitivity and specificity in diagnostic tests
seNsitive test has v low false Negative rate
sPecific test has a low false Positive rate
what are positive and negative predictive values in diagnostic tests
- Positive Predictive Value: the probability that the person with a positive test result has the disease - want this to be high then you’ll have a lot of confidence
- Negative Predictive Value: the probability that the person with a negative test result does not have the disease - want this to be high as well
what is the difference between direct and indirect tests
Direct- detect an organism, or a part of an organism
- E.g:
• Microscopy- view directly using light or electron microscopy, (generally following Gram staining)
• Culture- the growing of an organism in a controlled environment
• Toxin detection- identify a pre-formed toxin associated with a specific organism
• Antigen detection- using immunological methods to identify a antigen specific to an organism
• Nucleic acid amplification test (NAAT)- detect nucleic acid sequence specific to an organism
Indirect- detects an
element of the hosts specific, adaptive immune response to an organism. - eg looking for the antibodies raised against the organism
- referred to as serology or serological tests
describe how a direct toxin detection or direct antigen detection test work using enzyme immunoassay (EIA)
see microbiology 4 - diagnosing infection - slide 10
A specific antibody is bound to the test bed (‘solid phase surface’ in step 1). Then the patient sample is added (step 2). If the antigen is present in the patients faeces it binds to the antibody. We then add a second antibody which binds to the antigen in the sample. This second antibody has an enzyme label attached to it (‘e’)- step 3. Then some chromogenic (colour generating) substance is added- if the enzyme ‘e’ is present there will be a colour change. This can be detected by a machine reader, or in the example about a little cassette is used which can read by eye.
Describe Upper Respiratory Tract (URT) infections with examples
- above larynx = upper respiratory tract infection
- below larynx = lower respiratory tract infection
examples:
colds / sinusitis / otitis media / mumps / pharyngitis / epiglottitis
Common cold: > e.g: - rhinoviruses - coronaviruses - adenoviruses
- mucosal irritation - sneezing and coughing - symptoms - this can help spread the disease
often trigger LRTI
describe Acute Epiglotitis
- Young children
- Medical emergency!
- Respiratory obstruction
- Intubation and antibiotics required
- Blood culture often positive
Used to be common but Hib vaccine has largely eliminated this condition
cause:
- Haemophilus influenzae capsular type B
describe sinusitis
URTI
- All ages
- Facial pain
- Localised tenderness
- Fever
Viruses:
- Streptococcus pneumoniae
- Haemophilus influenzae
describe Acute Epiglotitis
URTI
- Young children
- Medical emergency!
- Respiratory obstruction
- Intubation and antibiotics required
- Blood culture often positive
Used to be common but Hib vaccine has largely eliminated this condition
cause:
- Haemophilus influenzae capsular type B
describe mumps
URTI
- Parotitis - swelling of parotid salivary gland
- Respiratory spread
- No specific treatment
- Vaccine preventable (MMR)
but seems to be less effective in recent years
Diagnosis:
- RT-PCR for mumps RNA in saliva, (or buccal swab) or urine
describe Infectious mononucleosis (IM)
URTI
Epstein Barr Virus- Herpes family
– Transmitted in saliva- infects B lymphocytes
– Teenagers and young adults get IM
– Babies get asymptomatic infection
Fever, sore throat, lymphadenopathy Splenomegally, lethargy, hepatitis Symptoms immunologically mediated
Blood white cell changes
test:
Monospot serology test
Or EBV IgM
Complications rare – eg encephalitis, nearly always with complete recovery
No specific treatment
describe Streptococcus pyogenes
URTI
• Pharyngitis- manifests as sore throat & fever
– Peritonsillar abscess (‘quinsy’)
- scarlet fever
– Rheumatic fever.
– Rheumatic heart disease
– Acute glomerulonephritis.
DIAGNOSIS –
(1) Throat Culture
(2) ASOT (Anti-streptolysin O titre)(serology)
Treatment – Penicillin (Erythromycin)
describe Diphtheria
URTI
Corynebacterium diphtheriae - Gram positive bacillus
- Pharyngeal diphtheria. – pseudomembrane
- toxin can cause fatal heart failure and a polyneuritis
- Toxin is phage coded
Disease of the past here but still prevalent in other areas of the world.
- Effective vaccine.
- Treatment – antitoxin (antibody) + Penicillin or Erythromycin
describe Laryngitis and tracheitis
Inbetween upper and lower RTI
- Common & lots of causes
- One example is Croup - Inbetween upper and lower RTI
- Croup = laryngotracheobronchitis causing inspiratory stridor due to laryngeal narrowing – young children
Caused by Parainfluenza viruses 1&2
Diagnosis:
- PCR
- But mostly clinical diagnosis
treatment:
- Paracetamol & fluids
- Corticosteroids if severe
- Adrenaline if hospitalised
describe Bordetella pertussis (whooping cough)
LRTI
gram negative coccobacillus
Catarrhal illness then paroxysms of coughs.
– Followed by a ‘whoop’ sound due to inspiratory gasp of air.
– Can go on for weeks – “100 day cough”
– Most severe in young babies
Lobar or segmental collapse of the lungs can occur
- Spread from person to person by air-borne droplets. - quite infectious
- Attach to respiratory epithelium.
treatment:
- macrolide
- (also prophylaxis for contacts can be given)
- Immunisation – acellular vaccine.- seen re-emergence lately though
describe acute bronchitis
LRTI
inflammation of mucous membranes in the bronchial tubes
Viral = Non-productive cough
Bacterial = Productive cough
often viral
virus can trigger a subsequent bacterial infection
Acute exacerbation of chronic bronchitis
- COPD (Chronic obstructive pulmonary disease)
describe bronchiolitis
LRTI
• RSV (Respiratory Syncitial Virus) is the main agent
• <2 years of age- narrow bronchioles.
• Wheezy presentation
– Cough, wheeze, low O2,raised resp rate, cyanosis, consolidation
• => interstitial pneumonia.
describe RSV (Respiratory Syncitial Virus)
- Transmitted by large droplets and by hands.
- October – February
- About 1 in every 100 infants with RSV bronchiolitis or pneumonia requires admission to hospital.
- Severe in children with heart and lung problems – these are given prophylatic paluvizumab each winter
- Paluvizumab is a monoclonal antibody specific to RSV
- Treatment – ribavirin if severe / life threatening
describe typical pneumonia
• Classical scenario is lobar pneumonia due to
Streptococcus pneumoniae:
– Lobar pneumonia- clinical and radiological
– Positive blood cultures
– Productive cough- Rust coloured sputum
• Gram stain – polymorphs and gram positive diplococci
• Culture – pneumococcus
• Pneumococcal Urinary antigen
describe atypical pneumonia
– “atypical agents”
• E.G. Mycoplasma pneumoniae,
• Chlamydophila pneumoniae, Chlamydophilia psittaci, Legionella pneumophila, Coxiella burnetii (Q fever) Mycoplasma pneumoniae
– “atypical symptoms”
• Extrapulmonary symptoms
• Little or no sputum – Dry cough
• No evidence of lobar consolodation
describe TB
Mycobacterium tuberculosis
- Primary infection often asymptomatic
- Dormancy and reactivation
- Diagnosis:
- Zeihl Neelson stain on sputum- Quick - not very sensitive
- Culture – Slow – weeks – special media
- PCR
Treatment:
- 3 drug combination to prevent resistance - resistance is increasing and is problematic
- Prolonged course – months.
name some bacteria that cause intoxication and then some that cause infection
Intoxication:
Bacillus cereus Staphylococcus aureus Clostridium perfringens Clostridium botulinum
Infection: Salmonella Shigella Escherichia coli Vibrio cholerae Campylobacter Clostridium difficile Listeria monocytogenes
describe salmonella and how it causes infection
gram negative rods
from family of Enterobacteriaceae
over 2000 different serotypes
not a normal inhabitant of the gut
2 main syndromes:
> ENTEROCOLITIS:
- a zoonosis - acquired from a non human animal
- lots of different serotypes
- eg S. typhimurium & S. enteritidis
- transmitted to humans via contaminated food
- Incubation Period 6h-2d
- Symptoms: nausea, vomiting, abd. cramps, and non-bloody
diarrhoea
- Duration 2-7d
- Diagnosis: Culture on selective media or PCR
- Treatment - fluid and electrolyte replacement, only antibiotics if immunocompromised
> ENTERIC FEVERS:
- human infections - host is humans
- eg Salmonella typhi and Salmonella paratyphi
- human to human transmission
- Incubation Period 10 to 14 days - much longer than enterocolitis
- Symptoms: fever with headache, myalgias, malaise can be severe sepsis
- Duration = 1 week followed by diarrhoea
- Diagnosis: Culture on selective media
describe shigella and how it causes infection
Gram –ve rods- enterobacteriacea
bacillary dysentery
human pathogen
spread by feral-oral route
v small infectious dose - so therefore v infectious
- four species
- S. dysenteriae; the most serious
- Most cases in UK caused by S. sonnei
- Primarily a pediatric disease (& causes outbreaks in childcare facilities)
- Short IP- diarrhea is watery initially, but later contains mucus & blood & pus- abdominal cramps & fever
- Antibiotics should only be given for severe shigella diarrhoea – susceptibility testing important - variability in terms of what antibiotics shigella are sensitive to
describe Escherichia coli and how it causes infection
- Gram –ve rods
- enterobacteraceae
- some strains are normal gut flora others cause infections
- Six distinct groups of E. coli with different pathogenetic mechanisms some invasive, others toxigenic
- ETEC enterotoxigenic E.coli (cause traveller’s diarrhoea)
- EPEC enteropathogenic E.coli (cause diarrhoea in babies )
- EHEC enterohaemorrhagic E.coli Haemolytic uraemic syndrome - Associated with eating undercooked, ground beef & raw milk or contact with animals - Cause bloody diarrhoea with abdominal cramps but no fever (HC) - can cause complication of HUS (Haemolytic Uremic syndrome)
- Specific tests to identify strains of pathogenic E. coli - can be difficult
- Antibacterial therapy- not indicated
describe cholera
- acute infection
- caused bu comma-shaped gram negative bacterium V. cholerae serotype 01
- symptoms due to enterotoxin
- Toxin causes fluid loss & painless, profuse, watery diarrhea
- Can cause death by dehydration and electrolyte imbalance if untreated
- Treatment: fluid replacement critical
- Infection acquired from contaminated water supplies
describe campylobacter and how it causes infection
Curved or S-shaped Gram negative rods
The most common cause of food-associated diarrhoea in UK
Most human illness is caused by one species, C jejuni
come from non human animals
Campylobacter enteritis:
- duration of symptoms 1 week
- fever
- abdominal pain
- blood in faeces
- rare complication: Guillain- Barre syndrome
describe Clostridium difficile and how it causes infection
Gram +ve anaerobic rods- spore forming
Component of normal gut flora ; flourish under selective pressure of antibiotics (broad-spectrum)
person to person spread
common cause of hospital acquired infectious diarrhoea
this is a cause of Antibiotic-associated diarrhea
- produces an enterotoxin and cytotoxin
- can cause Pseudo-membraneous colitis- can be rapidly fatal
- Diagnosis : detection of toxin in faeces
- Treatment:
> Stop antibiotics
> Oral metronidazole or vancomycin ..or oral fidaxomicin
BNF treatment: • First line: - Oral metronidazole 10–14 days • If recurrent or non responding: - oral vancomycin 10–14 days • For infection not responding to vancomycin, or for life-threatening infection, or in patients with ileus: - oral vancomycin + iv metronidazole • Difficult situations: - Oral fidaxomicin – expensive - Faecal matter transplant
what are the two main viruses associated with viral diarrhoea
Rotaviruses & Norovirus
what are the main symptoms of viral diarrhoea
watery diarrhea and vomiting.
describe rotavirus
• Mainly diarrhoea • <2 years of age • Severe presentation –dehydration common, major killer in 3rd world • Incubation 1-2 days • Duration ~ 4 days - diagnosis: – Viral particles can be seen by electron microscopy – Detection of viral RNA / antigen
describe norovirus
• Mostly vomiting, (‘Winter vomiting disease’)
• All ages
• Outbreaks in community, institutions, hospitals & Food associated outbreaks
• Incubation 1-2 days
• Duration 2 days
- diagnosis: PCR
what are the symptoms of meningitis
- Fever
- Stiff neck
- Photophobia
- Headache
- Vomiting
- Irritable
- Drowsy
what are the causes of bacterial viral and fungal meningitis
Bacteria: - Neisseria meningitidis - Haemophilus influenzae type b - Streptococcus pneumoniae (NHS to remember)
Viral:
- enteroviruses (most common) & others
Fungal:
- e.g Cryptococcus neoformans
describe Neisseria meningitidis aka meningococcus
- Commonest and severe
- Children (<5y) and young adults (15-20y)
- rash
• Capsule types A B & C and others Y & W
– Vaccines for ACWY
– Most UK cases now B – new vaccine has been introduced
Present with:
- Haemorragic rash
- Purpura
- Non blanching on tumbler test
- Onset is sudden- hemorrhagic skin rash is a key clinical observation
- Person to person via respiratory droplets
describe Pnemococcal meningitis
caused by Streptococcus pneumoniae aka pneumococcus
more common in:
– Older age /Post head trauma / Related to sinus etc – Splenectomy
• Prevention: vaccines
describe Haemophilus meningitis
caused by Haemophilus influenzae (capsule type B)
– Children 1-5 years of age
– Rare now since the HIB vaccine
Prevention:
• prophylaxis for close contacts
• Hib vaccine (UK childhood immunization schedule)
what causes TB meningitis
M. tuberculosis
describe neonatal meningitis
- Causes : Group B haemolytic streptococci (GBS) -10-30% of pregnant women colonized- (normal inhabitants of female genital tract)
- Also E. coli & L. monocytogenes
- Early or later onset disease. <1wk or >1wk age
- Permanent neurological sequelae- cerebral or cranial nerve palsy, mental retardation, hydrocephalus
- Clinical diagnosis -no specific signs-difficult to diagnose
- Blind’ antibiotic treatment
describe fungal meningitis
• C. neoformans
encapsulated yeasts
• Associated with meningitis in patients with depressed cell-mediated immunity (AIDS)
• Slow onset
• Diagnosis: India-ink-stained preparations of CSF- antigen detection
• Treatment: antifungal drugs
what are the general principals for bacterial meningitis
- antibiotics - give first does before urgent transfer to hospital
- if meningococcal disease - benzyl penicillin IV or IM
- if you don’t know the cause of the bacterial meningitis - cefotaxime or ceftriaxone
what is encephalitis, what is the main cause and how is it treated what are the main symptoms
- Inflamation of the brain substance
- -Key cause herpes simplex (HSV-1) – temporal lobe brain
- Treat with aciclovir – early – high dose – IV
– Stroke like signs and memory loss
– Behavioural changes
– Reduced consciousness
– Seizures
what are prions
strange infectious agents • Tiny – much smaller than viruses • No nucleic acid! • resistance to heat, disinfection and UV radiation • Very long incubation period • No immune response
describe transmissible Spongiform
encephalopathies
- transmitted by folding event
- protein randomly folds to wrong shape
- this wrong shape one causes other normal proteins to now change to the wrong shape version (autocatalytic)
- can have a genetic predisposition to it
- infectious from person to person
presentation: • Dementia • Ataxia • Other features • Progressive & fatal - brain full of holes - no actual inflammation
examples Is CJD Creutzfeldt-Jakob disease
define bacteruria
Bacteriuria: the presence of bacteria in the urine
define pyuria
Pyuria: the presence of white blood cells in the urine
Name the common bacterial causes of community-acquired and nosocomial UTI
1 = Escherichia coli
(70-95% of community acquired UTI)
- Escherichia coli with a P-fimbriae attach to urological epithelium
Allows them to ascend the renal tract to cause pyelonephritis (kidney infection)
Gram negative organisms:
Members of the Enterobacteriacae:
- Klebsiellaspp.
- Enterobacterspp.
- Proteusspp.
- Morganellaspp.and others
Pseudomonas aeruginosa
Important Gram positive organisms:
Staphylococcus saprophyticus
Streptococcus agalactiae
(Group B Streptococcus)
Enterococcus faecalis/faecium
