Lecture 5.1 - Hospital Acquired Infections PDF

Key terms: ◦Hospital acquired infections - HAI ◦Healthcare associated infections - HCAI ◦Nosocomial infections Hospital acquired infections: ◦Infections arising as a consequence of providing healthcare ◦Neither present nor incubating at time of admission (onset is at least 4...

Key terms: ◦Hospital acquired infections - HAI ◦Healthcare associated infections - HCAI ◦Nosocomial infections Hospital acquired infections: ◦Infections arising as a consequence of providing healthcare ◦Neither present nor incubating at time of admission (onset is at least 48 hours after admission) ◦Also includes infections in hospital visitors and healthcare workers ◦NHS England defines probable healthcare-associated COVID-19 inpatient infection as patients diagnosed more than 7 days after admission Consequences: ◦Hospital acquired infections (HAIs) are a major health and economic burden (8% of inpatients) ◦Results in increase in: ‣ Length of hospitalisation ‣ Morbidity ‣ Cost of care ‣ Mortality ◦Highest prevalence of HAIs - generally in ICU ◦Preventable Types of infections: ◦HAIs can be classified into six main types which account for 80% of all HAIs: ‣ Respiratory tract infections (pneumonia/other respiratory infections) - 22.8% ‣ Urinary tract infections - 17.2% ‣ Surgical site infections (SSI) - 15.7% ‣ Clinical sepsis - 10.5% ‣ Gastrointestinal infections - 8.8% ‣ Bloodstream infections - 7.3% Infection transmission: ◦Routes of entry of microbes ◦Skin - 10% ◦Gastrointestinal - 21% ◦Respiratory - 14% ◦Urogenital - 20% ◦Person to person transmission (respiratory/faecal-oral) Predisposing factors in patients: ◦Extremes of age ◦Obesity/malnourished ◦Diabetes ◦Cancer ◦Immunosuppression  ◦Smoker ◦Surgical patient ◦Emergency admission ◦Prosthetic devices Organisms causing hospital acquired infections: ◦Bacteria (staphylococcus aureus including MRSA, Clostridium difficile, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa) ◦Viruses (blood borne viruses hepatitis B and C, HIV, Norovirus, Rotavirus, SARS-CoV-2) ◦Fungi (Candida Albicans, Aspergillus species) ◦Parasites (Cryptosporidium spp - patient with cryptosporidiosis contaminated ice cubes through frequent use of the ice machines) Simplified Ventilator system: Ventilator associated pneumonia (VAP): ◦Pneumonia develops in 5-20% of mechanically ventilated patients ◦Mortality of ventilator associated infection is 10% ◦Associated complication - pulmonary ARDS (acute respiratory distress syndrome), pneumothorax, pulmonary oedema Pathogenesis of VAP: ◦Micro aspiration of oropharyngeal pathogens around the cuff ◦Micro aspiration of gastro-enteric regurgitated secretion ◦Bio film within the endotracheal tube ◦Cross contamination via respiratory equipment Ventilator associated Pneumonia: ◦Causative pathogens ‣ EARLY (5 days of being off ventilator) - MRSA, Pseudomonas species, multi-drug resistant organisms VAP bundle: ◦Elevation of the head of the bed 30 degrees to prevent aspiration ◦Sedation holiday to check for continued ventilation needs - try to get patient to breathe on their own ◦Weaning trials to indicate if the ventilator is still needed daily ◦Medication to prevent gastrointestinal bleeding (stress-related mucosal disease is a typical complication of critically ill patients)  ◦DVT prophylaxis (thromboembolism is a major complication in these patients) ◦Sub-glottal suctioning to prevent colonisation and infection from pooling of secretions must be done every 4 hours ◦Oral care to prevent accumulation of oral bacteria every 4 hours Catheter related blood stream infections: ◦Introduction to skin pathogens at the time of insertion ◦Contamination of the catheter hub(s) ◦Contaminated infusate (every infusate should be sterilised to a certain standard) ◦Migration of skin pathogens into the cutaneous catheter tract ◦Hematogenous seeding from a distant infectious focus ◦Most common pathogens: S.epidermis, S.aureus, Candida albicans Prevention measures: ◦Fill out central line insertion check list ◦Hand hygiene prior to insertion ◦Use standardised supply kit that is all inclusive for the insertion of central venous catheter ◦Use maximal barrier precautions (full body drape, wearing of cap, mask, gown and gloves) ◦Clean skin with chlorhexidine and allow to air dry ◦Need for continuation of catheter is evaluated on a daily bases ◦Central line dressings are changed every 7 days ◦Positive pressure caps are used on all central line ports and changed every 7 days Surgical site infections (SSI): ◦Most common HAI in surgical patients ◦Superficial incisional SSI: skin + subcutaneous tissue ◦Deep incisional SSI: deep soft tissue (fascia + muscle) ◦Organ/space SSI: organs, body cavities, sub-integumental spaces ◦Occur within 30 days post-op, or within 1 year if an implant is left, and infection appears to be related to the operation ◦Most SSIs occur between 5-10 days post-operation - most vulnerable time for patient Organisms causing SSI: ◦Enterobacterales - caused SSI are the most prevalent in large bowel surgery, contributing 48.5% of superficial SSIs and 55.7% of deep or organ/space SSIs ◦Infecting organisms in hip and knee surgery ‣ Methicillin sensitive staphylococcus aureus Hip 32%, knee 40.7% ‣ Methicillin resistant staphylococcus aureus Hip 4%, knee 3.1% ‣ Coagulase-negative staphylococci Hip 25.1%, knee 23.9% ◦Infections can also be caused by a mixture of organisms Prevention measures: ◦Screened prior to surgery for MRSA  ◦Chlorhexidine washes/shower ◦Alcohol containing skin prep (2% chlorhexidine gluconate in 70% isopropyl alcohol solution) ◦Preoperative antibiotics ◦Appropriate hair removal ◦Euglycemia ◦Optimise tissue oxygenation ◦Wound care ◦Best practice checklist ◦Surveillance for SSi ◦Educate providers, patient regarding SSI Catheter associated urinary tract infection (CAUTI): ◦Approximately 20% of hospital-acquired bacteraemias arise from the urinary tract, and the mortality associated with this condition is approximately 10%. ◦Urinary catheter associated infections are defined as an infection occurring 48 hours after insertion of a urinary catheter, signs and symptoms of infection (fever, pain, frequency, urgency, increased white count etc) and a positive urine culture of greater than 10^3 cfu/ml Causative organisms: ◦Multidrug resistant enterobacteriaceae (MDRE) ‣ Escherichia coli (gram negative) ‣ Klebsiella, Proteus and Pseudomonas species (gram-negative) ◦Candida albicans Prevention of catheter associated UTI: ◦Evaluation of catheter need prior to insertion ◦Hand hygiene should be done immediately before and after any manipulation of the catheter site ◦Closed catheter system ◦Catheter securement system ◦Urinary collection bag not to be higher than the bladder ◦Urinary collection bag not to rest on the floor ◦The catheter and collecting tube should be free of kinking ◦The collecting bag should be emptied regularly Multiresistant organisms: ◦MROs are bacteria that have become resistant to many of the antibiotics used to treat infections caused by them ◦Multidrug resistant organisms of concern are: ‣ Methicillin resistant staphylococcus aureus (MRSA) ‣ Vancomycin resistant Enterococci (VRE) ‣ Multidrug resistant Enterobacteriaceae (MDRE) Antimicrobial resistance: ◦Antimicrobial resistance is the ability of a microbe to resist the effects of medication that once could successfully treat the microbe ◦The term antibiotic resistance is a subset of anti-microbial resistance, as it applies only to bacteria becoming resistant to antibiotics ◦Factors to consider:  ‣ Duration of antibiotics ‣ Use of broad spectrum antibiotics ‣ Hygiene Principles of antibiotic resistance: ◦Inactivation of antibiotic (e.g. beta-lactamase) ◦Alteration of target - or binding site ◦Alteration of metabolic pathway - prevent formation of proteins or alter DNA ◦Reduced drug accumulation Emergence of resistance in staphylococci and gram positive bacteria: Methicillin resistant staphylococcus aureus (MRSA): ◦Methicillin-resistant staphylococcus aureus (MRSA) refers to a group of gram-positive bacteria that are genetically distinct from other strains of staphylococcus aureus. ‣ mecA gene codes for PBP2a which has low affinity for beta lactam antibiotics ◦Prevention - screening/handwashing/isolation ◦Management - antibiotics (vancomycin), dependent on site of infection Norovirus: ◦Norovirus is a non-enveloped, ss +ve strand RNA virus ◦Spread by faecal-oral route ◦Norovirus infection is characterised by nausea, vomiting, watery diarrhoea, abdominal pain, and in some cases, loss of taste. A person usually develops symptoms of gastroenteritis 12-48 hours after being exposed to norovirus ◦General lethargy, weakness, muscle aches, headaches and low-grade fevers may occur ◦Most who contract it make a full recovery within 2-3 days Rotavirus: ◦Rotavirus is a non-enveloped ds RNA virus ◦Rotavirus (RV) is considered as the most important viral agent of acute gastroenteritis worldwide in children less than 5 ◦Vaccines available for prevention of rotavirus infections ◦48 hours after the admission in hospital to 72 hours after hospital discharge Clostridium difficile (Clostridioides difficile): ◦Clostridium difficile gram positive spore forming rods ◦Pathogenic strains produced toxic polypeptides Toxin A and Toxin B  ‣ Toxin A and Toxin B are exotoxins which stimulate the inflammatory response ‣ Toxin A and Toxin B are enterotoxins (cause gastrointestinal symptoms) ◦Symptoms include watery diarrhoea, fever, nausea and abdominal pain. It makes up about 20% of cases of antibiotic-associated diarrhoea Clostridium difficile associated problems: ◦Antibiotic associated diarrhoea - benign, self-limited after use of antimicrobials, clostridium difficile implicated in 10-25% ◦Antibiotic associated colitis - worse diarrhoea, fever, abdominal pain, leukocytosis, clostridium difficile implicated in 50-75% ◦Antibiotic associated pseudomembranous colitis - typical pseudomembranous, high leukocytosis, profuse diarrhoea, abdominal pain + distension, can progress to toxic megacolon, sepsis and death (6-30%). Clostridium difficile implicated in 90-100% Risk factors/management - clostridium difficile: ◦Antibiotic use and clostridium difficile infection: ‣ High risk - Cephalosporins, Clindamycin, Co-amoxiclav, Ciprofloxacin ‣ Intermediate risk - Amoxicillin, Carbapenems, Erythromycin ‣ Low risk - Nitrofurantoin, Penicillin V, Trimethoprim, Vancomycin ◦Healthcare environment ◦Acid suppression medication (may help clostridium difficile proliferate by altering gut flora) ◦Management - isolation measure, treatment of dehydration and vancomycin