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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