Microbiology - Infection and Immunity Flashcards
Prophylaxis
Treatment given, or action taken to prevent disease
HCAI
Healthcare-associated Infections MRSA C. difficile ESBL Surgal site infections
MRSA as a HCAI
Indwelling catheters (urinary, PEG’s etc) Poor hygiene (handwashing, etc)
C. difficile as a HCAI
Antibiotics
Proton pump inhibitors
Poor hygiene
ESBL as a HCAI
Urinary catheters
Surgical site infections
Gram -ve bacteria
MRSA
Group A streptococcus
Anaerobes
How do we prevent HCAI
Operating theatre air quality Vaccination Post exposure prophylaxis Surveillance - outbreak investigation Standardisation ANTT
ANTT
Aseptic no touch technique
Why do we need to prevent HCAI
To reduce morbidity and mortality which may result from sepsis
To reduce the length of stay in hosp
To reduce the economic burden
To reduce the risk of surgical procedure
Patients w/ HCAI’s are 7x more likely to die as inpatients
Factors associated w/ infection
The micro-organisms
The host
The environment
Treatment: previous and current
Preventing airborne transmission
Place the infected patients in source isolation
Protect the vulnerable patients by use of filtered air, negative pressure (TB)
Preventing direct contact
Patients w/ microorganisms that pose a risk for others (e.g. MRSA, Vancomycin-resistant enterococci, Clostridium difficile, Norovirus) are placed in source-isolation
Aseptic technique, hand hygiene etc
Environmental hygiene
Decontamination of contaminated equipment or medical devices
Safe disposal of hosp waste
Screening of suspects carriage (patient) and immunisation (staff)
Enhancing resistance to infection
Vaccination
Optimising nutrition
Other factors e.g. body temp
Infection transmission route (HCAI)
Person to person spread Direct contact (skin to skin) Faecal-oral Airborne/ droplet Blood to blood Environment or person spread - indirect
Factors to consider for surgical antibiotic prophylaxis
Type of wound
Most likely pathogens
Antimicrobial factors
Type of wound - Abx prophylaxis
Clean
Clean/ contaminated, has opportunity to become contaminated as is in close proximity to a contaminated area
Dirty – contaminated, purulent (filled w/ pus)
Colonisation vs infection
Microorganisms existing in the body but don’t invade tissue or cause detectable (clinical) damage vs when microorganisms begin to invade the body tissues and cause detectable (clinical) damage
Examples of clean surgeries
Cardiac/ vascular Breast Orthapaedic Dialysis access Neurologic
Most likely pathogen in clean surgeries
Staphylococcus aureus,
S. aureus, Cogaulase -ve
Examples of clean/contaminated surgeries
Burn
Head and neck
GI
GU
Most likely pathogen in clean/contaminated surgeries
Coagulase -ve staphylococci
Psuedomonas aeruginosa
Example of dirty surgeries
Ruptured viscera
Most likely pathogen in a dirty surgery
Streptococci
S. aureus
Anareobes
Enterococci
Routes of delivery for Abx
Oral - time for conc to peak IV - injection or infusion Intramuscular Local PK/PD characteristics
Patient related factors to HCAI
4 hr mark is very critical
Host resistance Age Malnutrition Hypovolemia Obesity Diabetes Steroids Other immunosuppressants
Host resistance in patient related factors
Healing response
Local wound characteristics
Operative characteristics
Hypovolemia
Poor tissue perfusion
Procedure related factors
Some procedures are riskier than others depending on entry of tract
Pre-existent sepsis (local or distant)
Poor skin preparation, incl shaving
Nonviable tissue in wound
Hematoma
Foreign material, incl drains and sutures
Dead space
Golden standard sample to send to microbiology
Bone sequestrae
Pus is better than swabs
Most septic part of body
Bone
Main presentation of infections
Fever Chills and sweats Change in cough or a new cough Sore throat or mouth sore Shortness of breath Nasal congestion Stiff neck Dysuria Unusual vaginal discharge Increased urination D + V Pain in the abdomen or rectum Redness, soreness or swelling New onset of pain
Localised signs of infection
Rubor (redness)
Tumor (swelling)
Calor (heat)
Dolor (pain)
Classification of skin and soft tissue infections
Superficial
Moderate
Deep
Respiratory infections
Sore throat, about 70% of acute sore throats are caused by viruses
A lab diagnosis is not generally necessary for pharyngitis or tonsilitis
Cause of pneumonia or LRTI
Viruses in winter, and bacteria in summer (70%)
LRTI vs URTI
Usually more severe than infections of the URT and choice of appropriate antimicrobial therapy is important and be life saving
Symptoms of pneumonia and LRTI
Fever, sweating and/or chills Cough, often severe, that produces phlegm Shortness of breath Difficulty breathing Nausea and vomiting Muscle aches
Rash
Manifestation of infection that’s generalised in the skin
UTI
Bacterial infection usually acquired by ascending route from the urethra to the bladder
May proceed to kidney or bloodstream —> septicaemia
Most common cause of ascending UTI
Gram -ve rod E. coli
Bacteria causing infections of GI tract
E. coli
Salmonella
Campylobacter
Viruses causing infections of GI tract
Rotavirus
Norovirus
Abdominal infections
Usually polymicrobial
Usually result in an intra-abdominal abscess or secondary peritonitis, may be generalised or localised (phlgemon)
Symptoms of abdominal infections
Abdominal pain or tenderness Bloating or distention Fever Nausea + vomiting Loss of appetite Thirst Inability to pass stool or gas Fatigue
Viral hepatitis
Viruses directly targets the liver from A-E
Diff aetiologies e.g. non-infectious multisystemic conditions, infectious agents (hepatotropic viruses) and drug toxicity
Obstetrics and neonatal infections
Congenital
Perinatal
Postnatal
Congenital infections
Maternal —> microorganisms enter the blood, establish infection in placental —-> foetal infection
Intrauterine infections in pregnant women
May result in death of the foetus or congenital malformations
When will a foetus survive despite a congenital infection
In relatively non-cytopathic virus or when controlled by mother’s IgG response but may still be born w/ malformations or other pathological changes
Perinatal infections
Maternal blood: passage down infected birth canal e.g. herpes simplex
How do postnatal infections
Milk Blood Saliva contact Infected umbilical stump Meconium ----> sepsis
CNS infections
Usually blood -borne or infectious agents invading via peripheral nerves
Clinical feature of meningitis - bacterial
Clinical features incl a haemorrhagic skin rash w/ petechiae
Incubation period of bacterial meningitis
1-3 days
Sudden onset of sore throat, fever, irritability, neck stiffness
Pathogens causing bacterial meningitis
Haemophilus influenzae
Streptococuus Pneumoniae
Neisseria meningitides
Treatment for bacterial meningitis
Ceftriaxone - cephalosporin
2-4g daily by IV infusion or IV injection or deep intramuscular injection
Viral meningitis
Most common type of meningitis
Milder disease than bacterial meningitis, w/ headache, fever and photophobia but less neck stiffness
CSF is clear
Tetanus
Cl. tetani toxin is carried to CNS in peripheral nerve axons
Spores carrying tetanus
Widespread in soil and originate from fences of domestic animals
Spores enter wound and if necrotic tissue or the presence of a foreign body permits local and anaerobic growth —> tetanospasmin is produced
FUO
Fever of Unknown Origin
Common causes of FUO
Bacterial infections Viral infections Malignancy Automimmue Miscellaneous
Bacterial infections causing FUO
OM, abscess, infective endocarditis, typhoid fever
Viral infections causing FUO
EBV
Enterovirus
Adenovirus
Malignancy causing FUO
Leukaemia
Lymphoma
Neuroblastoma
Autoimmune conditions causing FUO
SLE
IBD
Miscellaneous conditions causing FUO
Kawasaki disease
Drug fever
Periodic fever
Causes of infective endocarditis
Native valves are usually infected by oral streptococci and staphylococci
Bacterial endocarditis signs
FROM JANE
Fever Roth spot Oster nodes Murmur Janeway lesions Anaemia Nail bed haemorrhage Emboli
When should sepsis be treated
Within 1 hr w/ Abx
Blood clotting
Disseminated intravascular coagulation
Sepsis 3
Low systolic pressure (<100 mmHg)
Increased respiratory rate (>22 breaths/ min)
Altered mental state
Body sites that are usually sterile
Blood and bone marrow Cerebrospinal fluid Serous fluids Tissues Lower respiratory tract Bladder
Body sites that have normal commensal organisms
Mouth, nose and upper respiratory tract Skin Gastrointestinal tract Female genital tract Urethra
Main 3 factors leading to infection
Host
Environment
Pathogen factors
Koch’s postulates
The microbe must be present in every case of the disease.
The microbe must be isolated from the diseased host and grown in pure culture.
The disease must be reproduced when a pure culture is introduced into a non-diseased-susceptible host.
The microbe must be recoverable from an experimentally infected host.
Functions of toxins
Promote bacterial survival by killing cells of the defence system
Killing other cells
Disabling tissue function,
Exotoxins
Substances produced by bacteria with a variety of functions
Nerve stimulating toxins
Staphylococcal enterotoxins act on gut nerves, which signal to the brain to cause vomiting
Toxins as super antigens
Activating many T lymphocytes, with the release of many cytokines, especially tumour necrosis factor (TNF), causing shock
Endotoxins
Produced by Gram -ve bacteria
Stimulate macrophages to release cytokines, TNF and IL1
How can HCAI be acquired
Exogenous source (e.g. from another patient – cross-infection) Endogenous source (i.e. another site within the patient – self- or auto-infection).
Reducing risks of post-operative infections
Preoperative stay minimised
Any infections treated before
Operations kept to minimum w/ good air flow - laminar air flow
Adequate debridement
Reducing the risk of infection in surgery
Abx and prophylaxis Foot flow – minimising coming in and out People in theatre Air flow directed away from pt Scrubbing and hand washing Reduce contamination n Sterile environment
