GUIDELINES FOR WORK-UP OF WOUND SPECIMENS

Transcription

1 GUIDELINES FOR WORK-UP OF WOUND SPECIMENS Yvette McCarter, PhD, D(ABMM) Director of Clinical Microbiology, Shands Jacksonville Professor of Pathology, UF College of Medicine-Jacksonville Jacksonville, FL 1

2 Faculty Disclosure The Association of Public Health Laboratories adheres to established standards regarding industry support of continuing education for healthcare professionals. The following disclosures of personal financial relationships with commercial interests within the last 12 months as relative to this presentation have been made by the speaker: Nothing to disclose 2

3 Objectives Discuss the use of the direct Gram stain to assess specimen quality and the advantages of reporting morphological identifications of organisms on direct specimen Gram stains. Describe the use of direct Gram stain results to aid in the work-up of wound cultures and review a new CAP requirement for utilizing the Gram stain. Demonstrate how to design and implement clinically relevant, timely approaches for cost-effective wound culture work-up. 3

4 Introduction Wound cultures are frequently contaminated with resident flora -- difficult to determine which organisms are potential pathogens. Work up can be problematic time and resources spent to work up cultures of little clinical value. Working up mixed cultures may generate clinically misleading results inappropriate and unnecessary antimicrobial therapy. 4

5 Still striving The major goal of the clinical microbiology laboratory is to provide information of maximal clinical usefulness as rapidly as is consistent with acceptable accuracy and minimal cost. Jay P. Sanford, MD (1974) 5

6 Utility of the Gram Stain A well-performed direct Gram stain is rapid, inexpensive, informational Allows for evaluation of specimen quality o Identification of superficially contaminated specimens o Enhances the discrimination between samples with potential pathogens vs. colonizing flora Provides presumptive organism identification o Guides rational selection of preliminary antibiotic therapy o Guides interpretation of culture results 6

7 Gram Stain Screening Criteria Standardized screening criteria o Consistent smear interpretations among technologists o Establish the quality of specimens submitted Optimal smear preparation and staining o Targeted selection of grossly mucopurulent portions of the specimen Use interpretive comments o Assist clinicians in interpreting results 7

8 Squamous Epithelial Cells Superficial Contamination 8

9 Neutrophils Inflammation 9

10 Interpretation and Reporting of Organisms in Direct Smears Bartlett JAMA 247: Designation of organism genera more useful than description of organism morphology Bartlett et al Diagn Microbiol Infect Dis 14: Reliable differentiation of Gram negative bacilli o Bacteroides or Haemophilus 95% o Enteric Gram negative bacilli 82% o Pseudomonas 56% 10

11 Enteric-like Gram negative bacilli Plump Gram-negative rods, can have non-uniform sizes and can sometimes show bipolar staining 11

12 Gram negative coccobacilli suggestive of Haemophilus or Bacteroides Gram-negative coccobacilli/pleomorphic rods that may be faint YM 12 staining 12 12

13 Non-enteric Gram negative bacilli Thin, somewhat faint staining, uniform in shape, elongated rods, sometimes in pairs end to end ( hot dogs ) 13

14 Gram positive cocci suggestive of Staphylococcus Gram-positive spherical Gram-positive 14 cocci in clusters or tetrads 14

15 Gram positive cocci suggestive of Streptococcus 15 Gram positive cocci in pairs or chains 15

16 Gram positive bacilli suggestive of Bacillus/Clostridium Gram positive bacilli suggestive of Diphtheroids Large box-car shaped Gram positive bacilli Small Gram positive bacilli, clubshaped, Chinese letter 16 appearance

17 Yeast Gram positive/variable yeast with/without buds, or with/without 17 pseudohyphae 17 17

18 Use of Interpretive Comments Wound specimens containing more squamous epithelial cells than neutrophils X6976 Collect D/T: 12/31/ Receive D/T: 12/31/ Wound Culture and Gram Stain Specimen Description Foot Direct Smear Suggests No neutrophils Many squamous epithelial cells No organisms seen Squamous cells in this specimen indicate the presence of superficial material that may contain contaminating or colonizing bacteria unrelated to infection. Collection of another specimen is suggested avoiding superficial sources of contamination. Culture Pending Report Status Preliminary 18

19 Use of Interpretive Comments Squamous epithelial cells are seen in a specimen with an anaerobic culture request H73026 Collect D/T: 01/01/ Receive D/T: 01/01/ Anaerobe Culture Specimen Description Request credited Leg Evidence of superficial material. Specimen unsuitable for anaerobic culture. Please consult Microbiology if clinical considerations warrant complete processing of this specimen. (Specimen will be held 5 days) Report Status Final 01/01/

20 Use of Interpretive Comments Specimens containing numerous morphotypes of bacteria in the direct Gram stain DIRECT SMEAR SUGGESTS: Moderate neutrophils No squamous cells Gram negative rods suggestive of Enteric-like Gram negative bacilli Gram positive cocci in clusters suggestive of Staphylococcus Gram positive rods suggestive of Bacillus/Clostridium Gram negative coccobacilli suggestive of Bacteroides/Haemophilus Gram stained direct smear suggests the presence of a mixture of organisms. Culture has not been performed because a mixed culture can be anticipated. This information is of doubtful value for direction of therapy against mixed infections containing this many potential pathogens. Please consult Microbiology if clinical considerations warrant complete processing of this specimen. (Specimen will be held 5 days). 20

21 Work up of Wound Cultures There are no clear guidelines for working up bacterial cultures o Rely on information that is available in the literature or colleagues o Query colleagues from same or different laboratories often get numerous differing opinions There seems to be a need for some consistency when performing culture work up o Uniformity in work up and reporting of bacterial isolates 21

22 A new requirement from the College of American Pathologists **NEW/REVISED** 07/31/2012 MIC Direct Gram Stain Procedures 22

23 MIC Direct Gram Stain Procedures (Phase I) **NEW/REVISED** 07/31/2012 The laboratory has protocols in place to use Gram stain results to provide a preliminary identification of organisms, evaluate specimen quality when appropriate, and to guide work-up of cultures. NOTE: The laboratory should have guidelines for the interpretation of the Gram stain reaction of the organism, morphology of the organism, and the quantification of organisms and cells. The protocol should address correlation of direct Gram stain results with final culture results. This does not mean that interpretation of the Gram stain morphology suggesting a specific organism identification (e.g. gram positive diplococcic morphologically suggestive of pneumococcus) is required. Evidence of Compliance: Written procedure for Gram stain (laboratories may use the correlation of Gram stain results with the final culture results as a component of the QC program) 23

24 Work up of Wound Cultures Specimen Quality When working up wound cultures the following are assumed: o Neutrophils infection or inflammation o Squamous epithelial cells superficial contamination = If a specimen contains a large amount of SEC, superficial contamination is likely. Bacteria isolated from such specimens should be minimally worked up o Extensive testing on heavily mixed cultures should not routinely be performed. 24

25 Work up of Wound Cultures Two Approaches These systems provide the means to consistently work up organisms from wound cultures Quality (Q) Score System Q/234 System Cumitech 7B: Lower Respiratory Tract Infections, ASM

26 Work up of Wound Cultures Q Score System (RC Bartlett, 1974) Determine average number or PMN and SEC/LPF on direct gram stain and assign value (see Key) Add values together using table below to obtain Q score Q score = # of potential pathogens (PP) worked up Key: 0 = no cells 1 = 1-9/lpf 2 = 10-24/lpf 3 = 25/lpf Q0 = 0PP Q1 = 1PP Q2 = 2PP Q3 = 3PP 26

27 Work up of Wound Cultures Q Score System Specimens without SEC are considered good quality specimens regardless of the number of PMN Up to 3 organisms can be considered potential pathogens (PP) and be worked up (ID/AST) if from a good quality specimen (Q3) The lower quality of the specimen (e.g., the more SEC present) the fewer the organisms worked up (Q2, Q1) o Q0 provide morphologic ID of organisms present but no work up 27

28 Work up of Wound Cultures Q Score System # PP in culture < Q-score: work up PP with ID/AST (2PP) (Q3) # PP in culture > Q-score: Look to direct Gram stain (3PP) (Q2) Work up only PP that were seen in direct Gram stain with ID/AST If all PP in the culture are seen in direct Gram stain Do not work up; perform morphological identification (MID) on all isolates MID = any rapid biochemical testing that can be performed (catalase, indole, oxidase, strep typing, etc.) 28

29 Work up of Wound Cultures Q/234 System Evaluate specimen quality (PMN and SEC) using whichever system you choose Culture work up is based on number of PP present: 2PP = Work up with ID/AST, as appropriate 3PP = Look to direct Gram stain Work up to 2 PP if they are seen in the direct Gram stain If all 3 PP are seen in the direct Gram stain, perform MID on all 3 4PP = Perform morphological identification (MID) on all isolates 29

30 Example 1: Leg Wound GS: moderate PMN (+2), few SEC (-1), many gram positive cocci suggestive of Staph, many gram positive cocci suggestive of Strep CULT: many Staph aureus, many β hemolytic strep, moderate coagulase neg staph, few diphtheroids WORK UP: Q Score (Q1=1PP): Q234 (2PP): 30

31 Example 1: Leg Wound GS: moderate PMN (+2), few SEC (-1), many gram positive cocci suggestive of Staph, many gram positive cocci suggestive of Strep CULT: many Staph aureus, many β hemolytic strep, moderate coagulase neg staph, few diphtheroids WORK UP: Q Score (Q1=1PP): MID S. aureus and β Strep; Report Mixed flora Q234 (2PP): 31

32 Example 1: Leg Wound GS: moderate PMN (+2), few SEC (-1), many gram positive cocci suggestive of Staph, many gram positive cocci suggestive of Strep CULT: many Staph aureus, many β hemolytic strep, moderate coagulase neg staph, few diphtheroids WORK UP: Q Score (Q1=1PP): MID S. aureus and β Strep; Report Mixed flora Q234 (2PP): Work up S. aureus and β Strep; Report Mixed flora 32

33 Example 2: Abdominal Wound GS: many PMN (+3), no SEC (0), many enteric-like gram negative bacilli, many gram negative coccobacilli CULT: moderate E. coli, moderate Bacteroides spp., few Enterococcus spp. WORK UP: Q Score (Q3=3PP): Q234 (3PP): 33

34 Example 2: Abdominal Wound GS: many PMN (+3), no SEC (0), many enteric-like gram negative bacilli, many gram negative coccobacilli CULT: moderate E. coli, moderate Bacteroides spp., few Enterococcus spp. WORK UP: Q Score (Q3=3PP): Work up E. coli, Bacteroides spp. and Enterococcus spp. Q234 (3PP): 34

35 Example 2: Abdominal Wound GS: many PMN (+3), no SEC (0), many enteric-like gram negative bacilli, many gram negative coccobacilli CULT: moderate E. coli, moderate Bacteroides spp., few Enterococcus spp. WORK UP: Q Score (Q3=3PP): Work up E. coli, Bacteroides spp. and Enterococcus spp. Q234 (3PP): Work up E. coli and Bacteroides spp.; MID Enterococcus spp. 35

36 Premise for Q Systems The more superficially contaminated the specimen, the higher the number of colonizing organisms present The quality of the specimen is important in determining acceptability of specimen and extent of culture work up If organisms are seen in the direct Gram stain, there is a greater chance they are associated with an infective process o At least 10 5 organisms must be present to visualize them in direct Gram stain 36

37 Advantages of Q Systems Offer a consistent approach for interpreting cultures o The systems are based on the quality of the specimen (primarily SEC) o Work up is based on organisms seen in the direct Gram stain o Limits the number of organisms worked up from mixed cultures reporting of misleading information can be minimized 37

38 Advantages of Q Systems No potential pathogen is ever ignored o All potential pathogens are reported may not be fully identified or have full AST performed o The pathogens that some believe should ALWAYS BE WORKED UP (S. aureus, β Strep, and P. aeruginosa) always indicated on the report o Either system can be modified to include screening for MRSA, VRE, ESBLs, etc 38

39 Advantages of Q Systems They provide guidelines o Both Q Systems offer guidelines for a systematic approach to culture interpretation and work up o These Guidelines are just that = Guidelines! Exceptions can be made if necessary o Any concerned physician can consult with microbiology to have further work performed on any culture if clinically indicated 39

40 The Q Systems in Practice C Matkoski, SE Sharp, and DL Kiska Evaluation of the Q Score and Q234 Systems for Cost-Effective and Clinically Relevant Interpretation of Wound Cultures. J Clin Microbiol 44:

41 Matkoski et al. 305 wound cultures evaluated over 3 months o 147 (48%) and 84 (28%) would have been interpreted differently with Q-score and Q234 systems, respectively, as compared to their routine wound procedure Routine procedure = work up to 3 organisms per culture o The majority of these differences were the result of unnecessary culture work-up utilizing their routine procedure 41

42 Matkoski et al. The reagent cost savings as compared to the routine procedure were greatest with Q score: o Q-score: $4895 per year o Q234: $1503 per year The cost savings would increase for both Q systems if technologist time were factored in as well 42

43 Matkoski et al. Although the Q-score had a yearly savings of $3,392 over the Q234 system and would have eliminated more culture work-up, it had several issues that would need to be addressed prior to implementation: o It would require physician approval for not culturing specimens with a Q score of zero (Q0) o It would require the training of all shifts to be able to examine the Gram stain and generate a Q score The Q234 system did not require a different interpretation of direct smears 43

44 Matkoski et al. Conclusions Both the Q score and the Q234 systems showed clinical relevance, cost effectiveness and would allow for standardized approaches to the work up of wound cultures. The Q234 system proved to be a more practical procedure to implement in their laboratory. o The Q234 system does not require a change in Gram stain interpretation or physician approval for specimen rejection. 44

45 Matkoski et al. Conclusions All potential pathogens are reported from a culture with either full ID or MID, allowing for further consultation with the ordering physician if clinically warranted. The Q234 system, which is more structured and cost-effective than their current method, was acceptable to their Infectious Disease physicians. This system allowed technologists to make more independent and consistent decisions about the significance of organisms in a wound culture. 45

46 As your mother used to say Watch your P s and Q s Gram stain of direct specimens is useful o For specimen quality assessment o For providing rapid presumptive identification o As a guide for culture work up o Permits compliance with new CAP checklist item Watch your P s and Q s Determine your P s Potential Pathogens Pick one of the Q s Q Systems Report consistent and clinically-relevant wound culture results 46

47 Helpful References Sharp, SE, et al Cumitech 7B, Lower Respiratory Tract Infections. ASM Press, Washington, DC C Matkoski, SE Sharp, and DL Kiska Evaluation of the Q Score and Q234 Systems for Cost-Effective and Clinically Relevant Interpretation of Wound Cultures. J Clin Microbiol 44: