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Wound infections
This document discusses wound infections, including the types (exogenous and endogenous), common causative organisms, and methods for diagnosis. It notes that pus accumulation is a sign of local infection and describes redness, pain, and swelling as additional indicators. Culture-based methods are outlined for identifying bacteria and determining pathogenicity from wound specimens. The importance of discussing isolated organisms with the physician is emphasized.
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Wound infections
- 1.
- 2. The accumulationof pus, either within an abscess or exuding from a sinus tract or from a mucocutaneous surface, is one of the cardinal indicators of local sepsis. Redness, pain and swelling
- 3. Liable tocontamination from body surface & environment Contaminants relatively low numbers Infection occurs if contaminants evades the host’s defence Multiplication of commensal may be colonization Virulence and resistance determines infection
- 4. Exogenous WoundInfections Endogenous Wound Infections
- 5. Source ofinfection is outside the body of the patient. Traumatic injury Decubitus pressure ulcers Animal or Human bites Burns Foreign bodies
- 6. Caused byorganisms that have been leading a commensal existence elsewhere in the patient’s body. Surgical or post operative sepsis. Nosocomial
- 8. Staphylococcus aureus,Streptococcus pyogenes,pneumococcus and coliform bacilli. Anaerobic organisms involved in soiled deep or lacerated wounds and devitalized tissues present. Gas gangrene and tetanus Mixed infections Pathogenic synergy
- 10. Ill, bedridden patient Anaerobic conditions because of tissue necrosis Most of these lesions are located near the anus or on the lower extremities Infection with bowel flora Chronic infection Bacteremia B. fragilis, Clostridia sp, Enteric bacteria, S. aureus and P. aeruginosa.
- 12. CDC groupEF-4 Weeksella zoohelcum Pasteurella spp Staphylococcus intermedius Staphylococcus aureus Simonsiella Capnocytophaga canimorsus
- 14. Pseudomonas sp Klebsiella sp Proteus sp E. coli Clostridia sp Aeromonas hydrophila
- 15. Streptobacillus moniliformis Spirillum minus
- 17. AEROBES: α haemolyticstreptococci S. aureus Streptococcus pyogenes Eikenella corrodens
- 18. ANAEROBES: Peptostreptococcus Prevotellaoris Prevotella buccae Porphyromonas sp Fusobacterium nucleatum
- 20. Bacteremia Significantmortality Interfere with the acceptance of skin grafts. 4 types – Impetigo, Surgical infections, Cellulitis, Systemic infections Factors that contribute to infection include loss of skin barrier, coagulated proteins, loss of vascularity, dehydration & immune response S. aureus, P.aeruginosa, Enterococci, Enterobacter sp & E. coli. Candida, Aspergillus niger, Fusarium, Mucor Herpes simplex
- 22. Chronic osteomyelitis S. aureus, Enterobacteriaceae, P. aeruginosa Anaerobic GNB & GPC Actinomycosis Actinomyces spp., Aggregatibacter actinomycetemcomitans, P. propionicum, Prevotella & Porphyromonas Tuberculosis, atypical mycobacteria, Nocardia Implanted foreign bodies Curettings or biopsy
- 24. Problems interms of collection Perirectal fistula in Crohn’s disease Bowel involvement only culture of specific key organisms like mycobacteria or Actinomyces are meaningful. Biopsy
- 26. AEROBES: S. aureus CONS Streptococcus pyogenes Streptococcus anginosus E. coli, klebsiella sp Enterococcus sp Proteus, Morganella & Providencia sp Pseudomonas sp
- 27. ANAEROBES : Clostridiumspp Peptostreptococcus spp Bacteroides spp Prevotella Porphyromonas Fusobacterium FUNGI : Candida spp
- 28. SPECIMENS : Woundswab Pus or exudate Fragments of excided tissue removed at wound toilet or Curettings Biopsy Blood
- 29. Physician should beurged that when a special investigation is required, they should state this clearly on the request form.Thus the routine investigation is usually confined to a search for the common pyogenic bacteria and anaerobic pathogens and does not include an examination for mycobacteria, actinomyces, nocardia, diphtheria, anthrax or fungi
- 30. Naked EyeExamination Microscopy Culture Gas Chromatography
- 31. Staphylococci -thick creamy pus Strep. Pyogenes – straw colored & watery Proteus – fishy smell Pseudomonas – sweet,musty odour & a blue pigment Anaerobes – offensive, putrid smell Actinomycosis – sulphur granules Mycetoma – black or brown granules Amoebic abscess – anchovy sauce
- 32. Presence ofrelative numbers of polymorphs and bacteria Morphology and arrangement Wet film – fungi or motile bacteria - fluid aspirated from inflamed joint resembling septic arthritis may show uric acid crystals - Dark ground microscopy Ziehl Neelsen or Fluorescent staining – AFB Immunofluorescent staining – Clostridia species Hematoxylin & Eosin – viral inclusions
- 33. Blood agar– aerobic - anaerobic MacConkey agar or CLED Agar Cooked Meat Broth PNPG Blood Agar Firm agar Special media
- 34. Culture platesare examined after overnight incubation at 37º C Relative number and type of colonies noted If there is no growth, the plates should be reincubated for another 24 h. If A. Israeli or Bacteroides suspected, plates incubated for 7 days If turbid, the broth should be subcultured
- 35. Difficulty inculture of slow growing anaerobes that are highly sensitive to oxygen. Their still invisible growth may be killed by exposure to air during examination. Anaerobic cabinet Inoculated on two anaerobic plates
- 36. Difficult inmixed cultures Scanty growth of CONS, diptheroids are not reported E.Coli from perineal wound etc are not reported. Physician informed in case of Clostidium perfringens. In chronic superficial lesions, the presence of mixed commensal bacteria can be disregarded as insignificant Pure growth of commensal type organism grown from deep sites(eg.pleural fluid) should be reported with sensitivities, unless the number of the organism is so small as to indicate they are contaminants.
- 37. Numerous orpredominant organism is pathogenic. Relative number of colonies may not reflect the number of organism in lesion. Variations such as relative speed of growth of different species under the cultural conditions used, the presence of traces of antibacterial drugs , and the greater tendency of delicate pathogens to die during transport Colonies in subculture from broth bears no relation to the number of organism in lesion. Discussion with the physician.
- 38. Significance ofisolates Predict the likelihood of burn wound sepsis Probability of wound healing Tissue weighed, homogenized, diluted serially, and inoculated into multiple agar plates. S.pyogenes are clinically significant, no matter what the quantity of bacteria present. >105 CFU/g is considered significant in burns Single biopsy of a wound will not give an accurate picture of the microbial flora of chronic wound
- 39. Buchanan etal 0.1(10-1) & 0.01(10-2 ) ml of sample in blood agar in duplicate The number of CFUs per gram of tissue is calculated using the formula: Number of CFUs counted * Reciprocal of volume of homogenate inoculated(10-1or 10-2 ) * volume of diluent used for tissue homogenization /weight of tissue