wound infections
TRANSCRIPT
WOUND INFECTIONS RAJESH KUMAR R S
The accumulation of 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
WOUND INFECTION
Liable to contamination 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
INFECTION VS COLONIZATION
Exogenous Wound Infections
Endogenous Wound Infections
TYPES
Source of infection is outside the body of the patient.
Traumatic injury Decubitus pressure ulcers Animal or Human bites Burns Foreign bodies
EXOGENOUS WOUND INFECTION
Caused by organisms that have been leading a commensal existence elsewhere in the patient’s body.
Surgical or post operative sepsis.
Nosocomial
ENDOGENOUS WOUND INFECTIONS
TRAUMATIC WOUND
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
TRAUMATIC WOUNDS
DECUBITUS PRESSURE ULCERS
Ill, bed ridden 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.
BED SORES
DOG BITES
CDC group EF-4 Weeksella zoohelcum Pasteurella spp Staphylococcus intermedius Staphylococcus aureus Simonsiella Capnocytophaga canimorsus
DOG BITES
SNAKE BITES
Pseudomonas sp Klebsiella sp Proteus sp E. coli Clostridia sp Aeromonas hydrophila
SNAKE BITE
Streptobacillus moniliformis Spirillum minus
RAT BITE
HUMAN BITES
AEROBES:
α haemolytic streptococci S. aureus Streptococcus pyogenes Eikenella corrodens
HUMAN BITES
ANAEROBES:
Peptostreptococcus Prevotella oris Prevotella buccae Porphyromonas sp Fusobacterium nucleatum
BURNS
Bacteremia Significant mortality 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
BURNS
SINUS TRACT INFECTIONS
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
SINUS TRACT INFECTIONS
FISTULA
Problems in terms of collection Perirectal fistula in Crohn’s disease Bowel involvement only culture of specific
key organisms like mycobacteria or Actinomyces are meaningful.
Biopsy
FISTULA
POST OPERATIVE WOUND INFECTION
AEROBES: S. aureus CONS Streptococcus pyogenes Streptococcus anginosus E. coli, klebsiella sp Enterococcus sp Proteus, Morganella & Providencia sp Pseudomonas sp
POST OPERATIVE WOUND INFECTIONS
ANAEROBES : Clostridium spp Peptostreptococcus spp Bacteroides spp Prevotella Porphyromonas Fusobacterium
FUNGI : Candida spp
SPECIMENS : Wound swab Pus or exudate Fragments of excided tissue removed at
wound toilet or Curettings Biopsy Blood
DIAGNOSIS OF WOUND INFECTION
Physician should be urged 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
Naked Eye Examination Microscopy Culture Gas Chromatography
LABORATORY EXAMINATION
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
Naked Eye Examination
Presence of relative 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
MICROSCOPY
Blood agar – aerobic - anaerobic MacConkey agar or CLED Agar Cooked Meat Broth PNPG Blood Agar Firm agar Special media
CULTURE
Culture plates are 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
Difficulty in culture 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
Difficult in mixed 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.
INTERPRETATION AND REPORTING
Numerous or predominant 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.
Significance of isolates 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
QUANTITATIVE CULTURE
Buchanan et al 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
SEMIQUANTITATIVE CULTURE OF TISSUE
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