Microbiology JC093: Infection Outbreak: Infection Control Flashcards
1
Q
Purpose of infection control
A
Protect health care workers, patients and visitors from nosocomial acquisition of epidemiologically important microorganisms and thus reduce hospital acquired infections
- Reduce risk + delay onset of HAI
- Prevent outbreaks / cross infection (protect patients, staff, visitors)
- Cost saving
2
Q
Definition
A
- Community acquired infection
- onset of symptoms before / within 48 hours of admission - Hospital acquired infection
- onset of symptoms **after 48 hours of admission
- 5-10% of all in-patients —> ↑ morbidity, mortality, length of hospitalisation, healthcare expenses (extend hospital stay 3 days)
- examples:
—> Catheter-associated blood stream infections (CABSI)
—> **Pneumonia (ventilator, tracheostomy-associated)
—> **UTI (urinary bladder- / nephrostomy- / cystostomy-catheter associated)
—> **Surgical site infections
—> Pressure sore related infections
—> Infections associated with blood and blood products
Common causative agents of HAI:
- ***MRSA
- ***Multidrug resistant Gram -ve bacilli (ESBL, Carbapenemase-producing Enterobacteriaceae, Carbapenem-resistant Acinetobacter baumannii / Pseudomonas aeruginosa)
- ***Antibiotic-associated C. difficile colitis
- Infusion / Blood product related infections
- Any CAI of patients / staffs spread to others in the hospital (e.g. SARS, MERS, Influenza, Ebola, Common viral respiratory disease, Enteric (Norovirus) diseases, CA-MRSA, TB)
- Nosocomial infection
- “Disease” “to take care of”
- Synonymous with HAI: infection acquired during hospitalisation - Health care associated infection
- Infections acquired in healthcare institutions other than acute care facilities (e.g. long-term care facilities / nursing homes)
- Infections acquired during hospitalisation but not identified until after discharge
- Infections acquired through outpatient care e.g. day surgery, dialysis, chemotherapy centre, home parenteral therapy
3
Q
Outbreak
A
- Increase in occurrence of an infection ***above the background rate
- One episode of rare occurrence e.g. SARS / Many episodes of common occurrence e.g. seasonal influenza
Pseudo-outbreaks:
- clusters of positive cultures in patients without evidence of disease e.g. **laboratory errors (equipment contamination with subsequent contamination of patient specimens)
OR
- **perceived increase in infections ∵ surveillance was not previously conducted for that problem / ∵ surveillance definitions, intensity, methods have changed
4
Q
Surveillance
A
Ongoing, systematic collection, analysis, distribution of information
- regarding **occurrence + **risk factors of an infection in defined populations
Primary aim:
- Determine **existing rates of infection + **risk factors —> then outbreaks can be identified when a particular rate > pre-existing rate significantly on statistical calculation
5
Q
***How to investigate an outbreak
A
When cluster of cases observed
—> On-call microbiologist is alerted
—> Carry out outbreak investigation
-
Case definition
- develop a **Working case definition based on the known facts of outbreak
- Working case definition: able to include confirmed + possible cases
—> contain “time” + “space” + “person” (*時地人)
—> e.g. “a case of CA-MRSA is defined as any patient with positive isolation of MRSA which is susceptible to fluoroquinolone from Jan 2013 to Mar 2013 in a certain unit / hospital”
—> may need to be refined as outbreak investigation proceed + more information available - ***Case finding
- conducted after Working case definition developed -
**Confirmation of an outbreak
- infection rate > pre-outbreak rate
- monthly rate for a particular infection **>95% CI based on previous years’ rates for that particular month
—> an outbreak exist
—> warrant outbreak investigation -
**Epidemic curve
- Outbreak over time: plot **No. of cases (Y axis) against **Time (X axis)
—> see whether give hints to possible source / mode of transmission
—> single, shared (i.e. common) source —> **High initial park of onset (control source will stop outbreak)
—> person-to-person transmission —> epidemic curve of **long duration with few / no peaks
—> poor infection control technique / contaminated patient equipment, esp. those due to common organisms e.g. Acinetobacter species, Pseudomonas aeruginosa —> epidemic curve of **long duration -
**Line listing
- determine important data to collect
- design questionnaire, electronic file for **data collection
- age, sex, underlying diseases, use of antimicrobial agents, invasive procedures, operating room, surgeon, nurses, exposure to other health care workers, medications, IV fluid, placement in different cubicles / wards during hospitalisation
- after reviewing medical records —> make a table with data of patients for statistical analysis - ***Formulation of hypothesis
- about possible source of infection, how infection is transmitted -
**Case-control study
- comparison of exposure to potential risk factors in the affected patients with those in control group by **univariate analysis
- ∵ hospital outbreaks usually only small no. of cases —> stratify in data + multi variate analysis usually not possible - ***Collect environmental samples for microbiological testing
- samples which may be source of outbreak
- microbiological typing to establish clonality (whether patient sample and environmental sample have similar microbes) by:
—> Antibiogram
—> Biotype
—> Single / Multilocus sequence genotyping
—> Pulse field gel electrophoretic genotyping
—> Complete genome sequencing
6
Q
Infection control team
A
- Daily operation of infection control practice
- Led by infection control officer (clinical microbiologist / physician received training in infection control)
- Infection control nurse (ratio of 1 per 250 beds in HK)
7
Q
Roles of Infection control team
A
- Develop annual infection control plan
- Surprise visits to monitor daily patient care practice to prevent infection
- Identify + resolve problems in implementation of infection control practice
- **Standard + Transmission-based precautions
- **Hand hygiene
- ***Personal protective equipment (PPE) - Epidemiological surveillance for health care associated infections (e.g. surgical site infections, device-associated infections)
- Outbreak investigations
- Education + Training to health care workers on infection control
- Monitor staff health / immunisation status + percutaneous exposure (needle stick injuries) / mucosal exposure to bloodborne pathogens e.g. HBV, HCV, HIV
- Collaborate with pharmacy / other specialities for antibiotic stewardship program
- Others:
- environmental cleaning, disinfection, sterilisation of equipment, disposal of infectious waste
- development of infection control policies / procedures
- oversight on use of new products directly / indirectly relate to risk of nosocomial infections
8
Q
4 main portals of transmission
A
- Contact (direct: person-to-person / indirect: via environment)
- Finger skin to skin: skin colonisation / infection
- Finger skin to mucosa of eye, nose, mouth: colonisation / infection (acute viral respiratory diseases)
- Ingested into GI tract: GI colonisation / Infectious diarrhoea - Droplet
- Airborne
- Parenteral (injection, infusion, transplantation, needle stick)
9
Q
Standard precaution
A
- applicable to ***ALL patients
Aim:
- reduce risk of transmission of bloodborne / other pathogens from recognised / unrecognised sources (even when presence of such agent is unsuspected)
- **basic level of infection control precaution —> used as a minimum in care of all patients to prevent acquisition of infection from **blood, all body fluids, secretions, excretions (except sweat) (regardless of whether contain visible blood), non-intact skin, mucous membranes
- ***Hand hygiene before / after every patient contact (including hand hygiene after gloves removed)
- **Gloves, **gowns, ***eye protection used when exposure to body secretions / blood is possible (e.g. in patients with profuse bleeding / vomiting / diarrhoea)
- Safe disposal of sharp instruments and needles in impervious sharp box
- ***Safe injection practices:
- hand hygiene
- maintenance of an aseptic field
- proper preparation of injection site
- use of gloves
- sterile, single-use, disposable needle, syringe used for each injection
- single-dose vials are preferred over multiple dose vials whenever possible
10
Q
***Transmission-based precautions
A
- 2nd tier of basic infection control
- for patients with **documented / suspected to be infected with **highly transmissible / ***epidemiologically important pathogens —> additional precautions beyond standard precautions are needed to interrupt transmission in hospitals
- rooms of patients requiring different precautions should be clearly marked with signs containing instructions regarding type of precaution that must be observed
- Contact precautions
- care of patients with
—> **Selected MDR bacteria e.g. VRE, MRSA
—> **Enteric virus (Noro, Rota)
—> **Scabies
—> Viral respiratory (e.g. RSV) pathogens
—> **C. difficile
- Hand hygiene + **Gloves required upon room entry for patients on contact precautions
- Nonsterile gloves for all patient contact
- **Gowns + Gloves removed prior to exiting isolation rooms
- Medical equipment dedicated to a single patient - Droplet precaution
- care of patients with suspected / confirmed infections with
—> **ALL respiratory viruses
—> **N. meningitidis
—> Bordetella pertussis
—> **Hib
—> **Mycoplasma pneumoniae
—> Mumps, Rubella
—> Streptococcal pharyngitis, Diphtheria, Pneumonic plague
—> other pathogens spread by droplets
- Respiratory secretion **>5 μm —> fall to ground within 1-2 metres —> healthcare workers **within 2 metres should wear surgical masks
- ***Surgical mask to patient (if tolerated) as source control to reduce shedding of respiratory droplets
- Speaking: 99.9% particles <5 μm - Airborne precautions
- care of patients with suspected / confirmed infections
—> **TB
—> **Measles
—> **Varicella
—> **Smallpox
—> **COVID-19
—> **SARS
- spread by airborne droplet nuclei **<5 μm + remain suspended in air for long time
- patients nursed in airborne infection isolation room with **negative air pressure (pressure differential of 2.5 Pa between patient room and anteroom) + minimum 12 air changes per hour
- doors to isolation rooms must remain **closed, all persons entering must wearing a respirator (*N95) with filtering capacity of 95% that allows tight seal over nose + mouth
11
Q
Hand hygiene
A
- General term referring to any action of hand cleansing (using soap + water, detergents containing anti-septic agent, alcohol-based handrub)
- Purpose: physical removal of dirt, organic material, chemical inactivation of microorganisms
Hands contain:
- ***Transient flora (e.g. S. aureus, Gram -ve bacteria, Yeast)
- ***Resident flora (e.g. Coagulase-negative staphylococci, Corynebacterium spp., Yeast)
- Bacteria can survive on hands for hours
- Virus can for 15 mins
5 moments recommended by WHO:
- Before touching patient
- Before a clean / aseptic procedure
- After body fluid exposure risk
- After touching patient
- After touching patient surroundings
Soap + Water (Chlorhexidine soap: 30-60 seconds):
- Hand ***visibly soiled
- Dealing with ***spores of C. difficile
- After using ***restroom
Alcohol-based:
- More effective in bactericidal / virucidal activity than Soap + Water (3 log reduction vs 0.8 log reduction in 15 seconds)
- More convenient + not limited by availability of washing basins
- Better skin care (Glycerol present)
- USA: Ethanol, Isopropanol
- Europe: Ethanol, Isopropranol, N-propanol
—> Ethanol (2 carbon): Better in vitro virucidal activity (記: EV)
—> Isopropanol, N-propanol (3 carbon): Better in vitro bactericidal activity (記: IB) - concentration 75-80%
- require Alcohol + Water to denature proteins
- Poor activity against **bacterial spore, **protozoan oocysts, ***non-enveloped viruses (e.g. Norovirus)
- No residual activity
- Alcohol for 30 seconds: 3.5 log reduction of microbial count
- Alcohol for 60 seconds: 4-5 log reduction of microbial count
12
Q
Constituents of different formulae of alcohol-based handrub
A
- WHO formula 1
- ethanol 80%
- glycerol 1.45%
- H2O2 0.125% - WHO formula 2
- isopropyl alcohol 75%
- glycerol 1.45%
- H2O2 0.125%
- Ethanol 80% + Isopropyl alcohol 75%: active component for microbial killing
- Glycerol 1.45%: emollients + humectants for better skin care
- H2O2 0.125%: inhibit growth of bacterial ***spore inside bottle
13
Q
Personal Protective Equipment (PPE)
A
- Variety of barriers / respirators used alone / in combination to protect mucous membranes, airways, skin, clothing from contact with infectious agents
- Selection depends on nature of patient interaction / likely mode of transmission
Gowns:
- disposable non-permeable 100% polypropylene in ***splash-prone procedures
14
Q
Gloves
A
Protect patients + health care workers from exposure to infectious materials that maybe carried on hands
Wear when:
- Anticipating ***direct contact with blood / body fluids, mucous membranes, non-intact skin, other potentially infectious material
- Direct contact with patients who are **colonised / infected with pathogens transmitted by contact route e.g. **VRE, ***MRSA
- Handling / touching visibly / potentially contaminated patient care equipment and environmental surfaces
Note:
- May have to be changed during care of single patient to prevent cross-contamination of different body sites
- Discard between patients
- Must not be washed for reuse ∵ microorganisms cannot be reliably removed from glove surfaces and cannot ensure continued glove integrity
- Put on last if worn in combination with other PPE
- Remove properly
- Hand hygiene following removal —> ensure hands not carry infectious material that might have penetrated through unrecognised tears / that could contaminate hands during glove removal
15
Q
Masks
A
- Protect health care workers from contact with infectious material from patients e.g. ***respiratory secretion + sprays of blood / body fluids
- Engage in procedures requiring sterile technique to protect patients from exposure to infectious agents carried in health care worker’s mouth / nose
- May be used in combination with goggles to protect mouth, noses, eyes / face shield instead to provide more complete protection for the face
- Procedures that generate ***splashes / sprays of blood, body fluids, secretions, excretions (e.g. endotracheal suctioning, bronchoscopy, invasive vascular procedures) require face shield / mask + goggles
- Masks not confused with particulate respirators (used to prevent inhalation of small particles that may contain infectious agents transmitted via airborne route)
