Wound infection & its impact on wounds healing by primary & secondary intention

1. Wound infection & its impact on wounds healing by primary & secondary intention Shila Patel Lead Nurse Infection Prevention & Control Epsom and St Helier University Hospitals NHS Trust

2. Today’s Topics • Defining wound infection • Impact on the patient • Factors influencing individual vulnerability • Microbial pathogenicity and virulence • Implications for the patient • Pain • Cost to the NHS and society • Impact on the practitioner-patient relationship • Case presentation • Preventing cross-infection • Summary

3. Defining wound infection The first step to understanding the impact of wound infection is defining wound infection accurately 4 basic conditions exist in open wounds: • Contamination • Colonisation • Critical colonisation • Infection

4. Contamination - a normal state • Defined as the presence of non-multiplying organisms on the surface of a wound • Not associated with delayed wound healing / active disease • All wounds are contaminated with micro-organisms • The type and quantity of organisms will vary from one wound to another

5. Contamination • Contamination can occur in a variety of ways: • Transfer of normal body bacteria, e.g. Staphylococcus aureus (including MRSA) & Staphylococcus epidermidis from other body sites into a wound • During surgery, e.g. bowel surgery when gut flora can readily contaminate the wound site, e.g. E.Coli • Cross-contamination from other patients, often via the hands of healthcare staff (preventing cross-contamination is therefore vital) • Environmental contamination, e.g. following a road traffic accident

6. Colonisation- a normal state • Defined as the presence of multiplying micro-organisms on the surface of a wound, but with no host immune response, or clinical signs and symptoms • Similarly to contamination it is a normal state and not associated with active disease, ill health or delayed wound healing • May be the pre-cursor to critical colonisation

7. Colonised wound

9. Critical colonisation- abnormal state • A transition state between surface colonisation and invasion of micro-organisms into viable tissue • The point at which the organisms can no longer be controlled and may lead to infection. There are no obvious signs of healing at this stage • It is worth noting that this is largely a conceptual stage, with limited supporting evidence

10. Infection • Defined as the presence of multiplying micro-organisms that overwhelm the body’s immune system resulting in spreading cellulitis (inflammation of the tissues) • Causes active disease, likely to delay wound healing

11. Infection Clinical diagnosis involves: • Assessing the patient / wound for the presence of clinical signs / symptoms, e.g.: • Pus • Cellulitis – redness, heat, swelling • Increasing pain • Wound breakdown • Fever • Increased leucocytes and • Identifying the causative micro-organism(s) (many wounds are polymicrobial) • Note: defining wound infection is a clinical diagnosis. Positive microbiology results in the absence of clinical signs/symptoms is not wound infection but rather wound colonisation (even if positive for MRSA)

12. Infection

13. Infection

14. Infection

15. What determines colonisation or infection?What determines the impact of infection? Individual vulnerability, including wound characteristics Type, quantity & disease causing ability (virulence) of the micro-organisms present versus Infection occurs when the balance between these factors is lost Emmerson, 1998

16. Wound characteristics • Anatomical position of the wound e.g. sacral sores more likely be become colonised/infected due to contamination with urine/faeces • Duration the longer a wound exists the greater the opportunity for colonisation/infection and further complications

17. Factors influencing individualvulnerability • Circulatory disorders • e.g. cardiovascular disease • Causes reduced blood and O2 supply to wounds, slows the healing process and increases the risk of infection • For rapid wound healing to occur the wound tissue O2tension needs to be > 40mm Hg • Levels < 20 mm Hg is unlikely to support healing • In healthy individuals with acute wounds the tissue O2 tension ranges between 60-90mm Hg • In chronic non-healing wounds the wound tissue tension can drop between 5-20mm Hg causing cell destruction and tissue necrosis, both of which facilitate microbial growth

18. Factors influencing individualvulnerability • Metabolic disorders • e.g. diabetes mellitus • Reduces neutrophil activity and interferes with phagocytosis • This can delay the normal inflammatory response and ingestion of microorganisms, preventing formation of granulation tissue and increasing the risk of infection

19. Factors influencing individualvulnerability • Nutritional status • Malnutrition is associated with a poor immune response and increased risk of wound infection • Malnutrition is defined as a deficiency, excess or imbalance of essential nutrients and causing a measureable adverse effect • Some studies have found up to 40% of pts are malnourised on admission to hospital

20. Factors influencing individualvulnerability • Immunosuppression • Can arise for a variety of reasons: concurrent infections and drugs, e.g. chemotherapy and long term steroid therapy • Can predispose to potentially serious infection • Advancing age • Also associated with increased susceptibility • Age linked to increased chronic disease and slower immune response

21. Factors influencing individualvulnerability • Additional specific risk factors associated with surgical site wound infection • Obesity: deep layers of adipose tissue reduce blood and O2 perfusion to the wound • Pre-operative colonisation with Staphylococcus aureus, sensitive and resistant strains (MRSA), increased risk particularly linked to complex procedures / implant surgery, e.g. hip prosthesis

22. Factors influencing individualvulnerability • The range of vulnerability factors discussed indicates that the impact of wound infection will vary from one pt to another depending on the number, type and severity of risk factors experienced • The more susceptible an individual the greater the impact is likely to be

23. Microbial pathogenicity & virulence • Pathogenicityis the ability of a microorganism to cause disease and is dependant on their virulence factors • Virulenceare the factors by which microorganisms invade, multiply and cause damage to tissues • Virulence factors can be genetic, biochemical or structural • They involve a number of complex processes

24. Microbial pathogenicity & virulence • Virulence factors fall into 2 main categories: • Invasiveness factors • Invasin production: extracellular substances / enzymes facilitate invasion of host cells, e.g. hyaluronidase, produced by streptococci & staphylococci and attacks connective tissue • Ability to overcome / bypass host defence mechanisms, e.g. slime production (Pseudomonas aeruginosa) enabling avoidment of phagocytosis

25. Microbial pathogenicity & virulence Toxigenesis factors Ability to produce toxin Exotoxins and endotoxins which can cause either a local or systemic effect, dependant on the amount of toxin released (Todar, 2009)

26. Microbial pathogenicity & virulence • Structural features • A variety of structure features also facilitate virulence, e.g.: • Capsules which offer protection from phagocytosis and complement action • Pili which facilitate attachment to host cells • Sticky biofilm on the wound surface which facilitate polymicrobial communities by evading host defence mechanisms • Ability to emit single bacteria which lead to further local infections / weaken the collagen matrix in healing wounds, resulting in further wound breakdown / re-ulceration

27. Biofilm on wound

28. Synergistic relationships Polymicrobial wounds Individually some microorganisms can have low virulence However, wounds containing a variety of microorganisms can develop synergistic relationships and gain virulence

29. Bio burden A high bio burden can increase virulence Quantitative measure of infection: - 105 cfu / cm2 (White, 2003) However, for some organisms, e.g. Group A Beta Haemolytic streptococci, very few organisms required for pathogenesis – high virulence factors Large numbers of organisms may be identified without overt infection In polymicrobial wounds individual species of microorganisms may be present in low numbers but are pathogenic due to synergistic relationships

30. All of these factors indicate the impact of wound infection will vary from one pt to another according to the pathogenicity / virulence of the microorganisms coupled with individual susceptibility

31. Implications for the patient • A number of studies have been undertaken considering the impact of surgical site infection (SSI) Coello et al (2005) • They studied 140 English hospitals participating in the national Surgical Site Infection Surveillance Scheme between Oct 1997-June 2001 • 67,410 pts included in the surveillance following 9 types of surgical procedures, e.g. limb amputation, abdominal hysterectomy, knee/hip prosthesis • Results: 2832 pts had an SSI, with superficial infection the most common. They had an increased length of hospital stay and crude mortality was higher for all categories. After adjusting for confounding factors pts who underwent vascular surgery, hip prosthesis & large bowel surgery had a higher adjusted mortality rate • Conclusion: post-operative wound infection following certain types of surgery is associated with significant mortality

32. Implications for the patient Partanen et al (2006) • Evaluated the impact of deep wound infection following hip fracture surgery on functional mobility and mortality • 2276 pts followed up, all over 50yrs & with non-pathological fractures. Control pts matched for age, sex, fracture type, treatment method and mobility, but without wound infection were used for comparison • Results: 29 pts developed deep wound infection. 4 months following surgery the pts with deep wound infection had poorer mobility & greater dependency on walking aids. These pts had an increased length of hospital stay. 1yr following surgery the overall mortality for pts with infection was also higher – 34.5% versus 24.1%. Diabetes was a common risk factor for the infection cohort • Conclusion: deep wound infection following hip fracture surgery has a significant impact on mobility and can increase the risk of mortality

33. Implications for the patient • It is unclear whether the findings of these studies are applicable to all types of wounds • However, the studies demonstrate that wound infection following certain surgical procedures, affects quality of life (mobility) and can increase mortality • Wound infection may also impact the pt in other ways. Delayed discharge may delay a return to paid employment, cause financial difficulties, affect self-esteem and overall psychological well-being • Therefore, potentially extensive impact for the patient in a variety of ways

34. Pain Wound infection can produce a significant increase in pain Wound infection Chronic inflammation around wound site Excitation of sensory receptors Sensitisation of indirect pain e.g. nociceptors mediators Pain is one of the most reliable indicators of wound infection

35. Pain • Antimicrobial dressings, e.g. iodine / honey, can further increase pt’s pain on application (Hofman, 2006) • This can make the pt fear wound dressing changes • Increased psychological impact of pain • Conversely it has also been reported that antimicrobial dressings reduce pain in certain wound types, e.g. leg ulcers (Vanscheidt et al, 2003) & burn wounds (Vloemans et al, 2003) • Therefore, the impact of pain can be really significant • Appropriate pain assessment and management will be critical

36. Infected dermatitis – extremely painful

37. Cost to the NHS & Society Coello et al (2005) • Considered the increased length of hospital stay and cost of SSI in wounds following a variety of surgical procedures • Results: associated with increased length of hospital stay ranging from 3.3 days for abdominal hysterectomy to 21.0 days for limb amputation Associated additional cost to the NHS ranged from £959 for abdominal hysterectomy to £6103 for limb amputation • These results suggest that the cost of wound infection may impact NHS service provision for other patients – it has to be paid for somehow and the NHS does not have unlimited resources • Conclusion: the cost to the NHS can be significant

38. Impact on the practitioner-patient relationship Gardner & Cook (2004) • Considered how pts are informed about having a SSI in their wound • Difficulties often experienced by pts in gaining relevant information • Healthcare professionals avoid communicating this information • Staff reluctance to discuss the matter may be related to feelings of guilt & responsibility • This may have a negative impact on the practitioner-patient relationship

39. Impact on the practitioner-patient relationship • Whilst it is unclear whether these findings apply to all types of wound infection, it is possible that pts and staff do experience similar difficulties and feelings, e.g. with chronic wound infection • This may be exacerbated if the wound is infected by MRSA • Many pts already have a poor perception of MRSA via the media (Hamour et al, 2003) • Therefore staff may feel reluctant to fully discuss the wound infection / status with the pt, further impacting the practitioner – patient relationship • Adequate communication is vital

40. Case Presentation 70yr male patient On admission to hospital found to be drowsy and confused Incontinent of urine PMH - COPD IHD Paraproteinaemia Schizophrenia Renal impairment Residential home

41. O/E Alert but disorientated Obese Pyrexial - 38° C Urinalysis positive: nitrites, leucocytes, blood Blood cultures – sterile MRSA screening swabs - positive (skin suppression therapy commenced) Urinary retention – catheterised Δ Acute confusional state 2° to UTI Treated with14 days Co-amoxiclav

42. Progress 12 days after admission Sacral sore grade 2-3 noted Still MRSA positive, including sacral sore, after one course of skin suppression therapy (NB CSU was MRSA neg)

43. 3 days later Pyrexial - 39° C CSU > 50 WBC >108 / L (coliforms) Blood cultures sterile Started on Tazocin Femoral line inserted for IV access Continued to spike fevers Repeat blood cultures yielded MRSA Started teicoplanin

44. 4 days later Sacral sore “Deep sloughy cavity plus discharge - pus” “Size of a fist” Referred to tissue viability “Sacral pressure ulcer, grade 3 8-10 cm diameter as conservative estimate” Teicoplanin continued - sacral ulcer dressed

45. Over next 2 weeks Attention to diet Sacral ulcer dressings Gradual deterioration Renal impairment – teicoplanin stopped - nearly 3 weeks completed Hb dropped Paraproteinaemia worsened Pyrexial again

46. Finally Referred for palliative care Died just over 6 weeks after admission RIP

47. Summary MRSA septicaemia 2° to infected sacral ulcer, which developed in hospital MRSA isolated from both blood and sacral ulcer Root Cause Analysis: Septicaemia might have been prevented by better care Therefore the impact / cost of wound infection for the patient can be fatal

49. Preventing cross-infection • Preventing cross-infection from an infected wound, healing by either primary or secondary intention, is vital • Healthcare professionals have a duty to safeguard pts from Health Care Associated Infections, such as wound infection, as much as possible • Implement standard infection control precautions at all times and with all patients • In additional at the time of wound dressing: • Turn off bedside fans – they can distribute bacteria over a wide are • Avoid bed-making as shaking sheets disperses skin scales / bacteria • Avoid sweeping floors as this can distribute dust / bacteria found in dust

50. Summary • A variety of factors can influence the impact of wound infection in both wounds healing by primary and secondary intention • There is a fine balance between individual patient vulnerability and the pathogenicity and virulence of the causative microorganisms • When the causative microorganisms overwhelm the individual’s immune system, wound infection will arise and the greater the vulnerability of the pt the greater the impact • The impact or cost to the patient, the NHS and the practitioner-patient relationship can be significant. Good communication is vital • Healthcare staff need to have a good understanding of these factors to prevent wound infection whenever possible and where it cannot be prevented accurate assessment and management is essential