Detecting / Reporting Resistance in Nonfastidious GNR Part #2. Janet A. Hindler, MCLS MT(ASCP)

Transcription

1 Detecting / Reporting Resistance in Nonfastidious GNR Part #2 Janet A. Hindler, MCLS MT(ASCP)

2 Methods Described in CLSI M100-S21 for Testing non-enterobacteriaceae Organism Disk Diffusion MIC P. aeruginosa x x Acinetobacter spp. x x Burkholderia cepacia x x Stenotrophomonas maltophilia x x Other non-enterobacteriaceae - x

3 Table 2B-5 CLSI M100-S21 Other Non-Enterobacteriaceae Other non-enterobacteriaceae include Pseudomonas spp. (not P. aeruginosa) and other nonfastidious, glucose-nonfermenting, gram-negative bacilli, but exclude P. aeruginosa, Acinetobacter spp., Burkholderia cepacia, B. mallei, B. pseudomallei, and Stenotrophomonas maltophilia. Refer to Tables 2B-2, 2B-3, and 2B-4 for testing of Acinetobacter spp., B. cepacia, and S. maltophilia, respectively, and CLSI document M45 for testing of Burkholderia mallei and B. pseudomallei.

4 Pseudomonas aeruginosa

5 What are some characteristics of P. aeruginosa that impact AST? Ability to acquire many types of resistance mechanisms MDR, XDR, PDR phenotypes Sometimes slower growth rates Sometimes mucoid phenotypes Antimicrobial therapy often requires combinations of agents (difficult to correlate in vitro results with in vivo efficacy)

6 Pseudomonas aeruginosa Recommended or Alternative Drugs ticarcillin, piperacillin ceftazidime, cefepime aztreonam doripenem, imipenem, meropenem tobramycin, gentamicin, amikacin ciprofloxacin (levofloxacin*) β-lactams -lactam as above + tobramycin or ciprofloxacin for serious infections For UTI, single drug usually effective R to -lactams may emerge during therapy *not listed in Sanford but has P. aeruginosa indication The Sanford Guide to Antimicrobial Therapy. 41 tst ed

7 Rx: Comment Pseudomonas aeruginosa Rx: The susceptible category for these drugs* implies the need for high-dose therapy for serious infections caused by P. aeruginosa. For these infections, monotherapy has been associated with clinical failure.. * penicillins, β-lactam/β-lactamase inhibitors CLSI M100-S21. Table 2B.

8 Specimen: Peritoneal fluid Diagnosis: Appendicitis Report Option Pseudomonas aeruginosa ceftazidime ciprofloxacin gentamicin imipenem piperacillin-tazo MIC (µg/ml) 8 S 1 S 2 S 1 S 16/4 S Infectious Diseases consult suggested for serious infections due to Pseudomonas aeruginosa

9 Pseudomonas aeruginosa Beta-lactam Breakpoints (1) Reevaluation but no change in breakpoints for cefepime, ceftazidime, aztreonam Added dosage information (ceftazidime and aztreonam dosages are higher than those for Enterobacteriaceae) M100-S21 Table 2B-1.

10 Pseudomonas aeruginosa Beta-lactam Breakpoints (2) Deleted breakpoints for: Ceftriaxone, cefotaxime - limited indications (e.g., urinary tract infections) Ceftriaxone FDA Prescribing Information updated Nov No P. aeruginosa breakpoints Cefotaxime no FDA update Ceftizoxime, cefoperazone, moxalactam - no longer available in USA Forthcoming changes in breakpoints for: Carbapenems Extended-spectrum penicillins β-lactam / β-lactamase inhibitor combinations

11 Outcomes of bacteremia (N=34 episodes) due to P. aeruginosa with reduced susceptibility to piperacillin-tazobactam 85.7% 22.2% 30.0% 20.5% Tam et al Clin Infect Dis. 46:862.

12 Pseudomonas aeruginosa Forthcoming (2012) Breakpoint (MIC µg/ml) Changes 1 Agent Current CLSI Breakpoints Forthcoming 2012 Susc Int Res Susc Int Res Piperacillin Piperacillintazobactam Ticarcillin Ticarcillinclavulanate Doripenem None (FDA 2 S) Imipenem Meropenem will be published with dosage comments

13 Some notes about other broad - spectrum drugs and P. aeruginosa. Drug Ertapenem Tigecycline -lactamase inhibitors For P. aeruginosa. No significant activity; (in contrast to other carbapenems, imipenem, meropenem, and doripenem which have activity against P. aeruginosa) No significant activity Add very little to activity of antipseudomonal penicillins Piperacillin-tazobactam = piperacillin Ticarcillin-clavulanic acid = ticarcillin Note: -lactamase inhibitor combinations (e.g., piperacillintazobactam) often used as empiric therapy for GNR and have enhanced activity over -lactam alone (e.g., piperacillin) against many other GNR.

14 AST of P. aeruginosa from cystic fibrosis (CF) patients Mucoid strains often grow better on agar media than in broth No consensus recommendation to test mixture of colony types

15 Guidelines for AST of CF P. aeruginosa Isolates 1994 CF Consensus Conference document Recommended disk diffusion for mucoid and nonmucoid strains CF Foundation. Vol 5. Section 1:1-26. More recent summary in Saiman & Siegel Infect Cont Hosp Epidemiol. 24:S6-52. Broth microdilution (BMD) = agar dilution. Saiman et al J Clin Microbiol. 37:2987. Etest, and disk diffusion = BMD. Burns et al J Clin Microbiol. 38:1818. Vitek and MicroScan BMD. Burns et al Diagn Microbiol Infect Dis. 39:257.

16 Pseudomonas aeruginosa The susceptibility of P. aeruginosa isolated from patients with cystic fibrosis can be reliably determined by disk diffusion or dilution methods, but may require extended incubation up to 24 hours before reporting as susceptible. CLSI M100-S21. Table 2B-1.

17 Value of tobramycin Etest in select settings for P. aeruginosa isolates from CF patients Cystic fibrosis patients sometimes treated with aerosolized tobramycin Tobramycin concentrations: Serum following IV dose usually 4 10 µg/ml BAL fluid following inhalation mean is 90 µg/ml Routine tobramycin MIC test system upper range usually 16 µg/ml Option: perform Etest for tobramycin-r P. aeruginosa to obtain actual MIC (Etest upper range 256 µg/ml) Morosoni et al J Clin Microbiol. 43:4480 Rosenfeld et al J Ped. 139:572.

18 Acinetobacter baumannii

19 What are some characteristics of Acinetobacter baumannii that impact AST? Can acquire many types of resistance mechanisms MDR, XDR, PDR phenotypes Generally low virulence Frequent colonizer Notes: Perform AST on invasive isolates Perform AST on other isolates when requested In some cases, to determine if isolate is MDR only for infection control purposes Most MDR and nosocomial transmission occurs with A. baumannii; other species less worrisome

20 The dilemma of colonization vs. infection Acinetobacter baumannii from variety of sources during nosocomial outbreak 18 with documented infections among 59 patients Go et al Lancet 12:1329. Colonization of mucous membranes and skin: Up to 43% among non-hospitalized individuals 75% among hospitalized patients on regular ward Mostly species other than A. baumannii Siefert et al J Clin Microbiol. 35:2819.

21 Specimen: Sputum Diagnosis: Cerebral hemorrhage GS: Many oral flora Few GNR Occasional WBCs Culture: Few Acinetobacter baumannii Many Normal oral flora Report Option Susceptibilities for A. baumannii are not routinely done because A. baumannii is frequently a colonizer when isolated from non-sterile body sites (e.g. respiratory). If A. baumannii is causing infection, susceptibility test results should guide therapy. Please contact laboratory to request testing

22 Acinetobacter baumannii Recommended Drugs doripenem or imipenem or meropenem fluoroquinolone + amikacin or ceftazidime Alternative Drugs ampicillin-sulbactam colistin Sanford, 2011.

23 Table 1A CLSI M100-S21 Suggested Drugs to Test / Report NO or

24 Imip-S Mero-R Pt. treated with meropenem based on imipenem-s result. Lesho et al Fatal A. baumannii infection with discordant carbapanem susceptibility. Clin Infect Dis. 41:758.

25 A. baumannii % Susceptible 1 (N=80) Amp- Sulb Pip- Taz Ceftaz Mero Amik Gent Tob Cipro T-S First isolate/pt (CLSI M39-A3) What are the susceptibility profiles of A. baumannii isolates at UCLA? UCLA 2009

26 A. baumannii (N=80 patients; 12 had multiple isolates with > 1 profile) Resistance Profile # patients % 1 NO Resistance Ak, A-S, Ctaz, Cip, Mero Ak, A-S, Ctaz, Cip A-S, Ctaz, Cip, Mero Ctaz A-S, Ctaz, Cip, Mero A-S, Ctaz, Cip Other (10 profiles) of 80 patients with A. baumannii Drugs examined: Ak - amikacin A-S amp-sulbactam Ctaz - ceftazidime Cip - ciprofloxacin Mero - meropenem UCLA 2009

27 Stenotrophomonas maltophilia

28 Stenotrophomomas maltophilia Recommended Drugs trimeth-sulfa Alternative Drugs ticarcillin-clav or aztreonam + ticarcillin-clav minocycline doxycycline ceftazidime (moxifloxacin) (tigecycline) Sanford, 2011.

29 Table 1A CLSI M100-S21 Suggested Drugs to Test / Report levofloxacin (not ciprofloxacin)

30 The dilemma of colonization vs. infection Stenotrophomonas maltophilia from respiratory isolates: 29-47% = infection Del Toro et al Medicine. 81:228. Khardori et. al RID. 12:997. Laing et al JCM. 33:513. Lanotte et al Clin Microbiol Infect. 9:1142. Villarino et al Infect Cont Hosp Epidem. 13:201.

31 Specimen: Sputum Diagnosis: Head Trauma Gram stain: Many oral flora Moderate GNR Occasional WBCs Report Option Culture: Many Stenotrophomonas maltophilia Many Normal oral flora Susceptibilities for S. maltophilia are not routinely done because S. maltophilia is frequently a colonizer when isolated from non-sterile body sites (e.g. respiratory). If S. maltophilia is causing infection, trimethoprim-sulfamethoxazole is the drug of choice (>97% susceptible) and is often used in combination with other agents

32 Stenotrophomonas maltophilia % Susceptible N Tmp- Smx Levo Cipro Mino Ceftaz Ticarclav Gales et al J Chemother. 20:38. 2 Sader et al Intl J Antimicrob Agents. 25:95. (good resource for antibiograms on unusual non-fermenters!!!) 3 UCLA 1/06-12/10

33 What more should we know about AST / reporting on MDR GNR?

34 No single definition of MDR fits all isolates and works for all facilities! Individual facilities should seek appropriate guidance and adopt effective measures that fit their circumstances and needs. (page 31)

35 Goal: by applying these definitions, clinical, reference and public health microbiology laboratories will use a common terminology for grading various antimicrobial resistance profiles Very new and not yet (?) widely accepted. Clin Microbiol & Infection. July 27, Epub.

36 Definitions MDR multidrug-r (e.g., R to 3 drug classes) XDR extensively drug-r (e.g., R to almost all classes but retains S to at least one drug class) PDR pandrug-r (e.g., R to all drug classes) Definitions apply to acquired (vs. intrinsic ) resistance and to drugs that might be used to treat an infection caused by the species.

37 Antibiotic Options for MDR GNR Nicasio et al Pharmacotherapy. 28:235.

38 See Table 5. Treatment Options for Selected Highly Resistant Bacteria

39 What should we know about testing / reporting colistin and polymyxin B? Class: lipopeptide; administered by IM & IV route Proteus/Providencia, Serratia, Burkholderia cepacia intrinsically resistant Active against most but not all MDR P. aeruginosa, A. baumannii, other GNR Polymyxin B and colistin activity are comparable Increasing colistin use - emerging resistance a concern Park et al Diagn Microbiol Infect Dis. 64:43. Samonis et al Clin Infect Dis. 50:1689. Kontopidou et al Clin Microbiol Infect. Accepted /j No FDA breakpoints; no FDA-cleared test Good reviews Landman et al Clin Microbiol Rev. 21:449. Zavascki et al J Antimicrob Chemother. 60:1206.

40 Colistin / Polymyxin B CLSI Breakpoints Organism MIC (µg/ml) Zone (mm) Susc Int Res Susc Int Res Acinetobacter spp. 2-4 none Pseudomonas aeruginosa Enterobacteriaceae None provided 3 1 colistin 2 polymyin B 3 most use MIC 2 µg/ml for Susc CLSI M100-S21 Tables 2B-1 & 2B-2.

41 Polymyxin B Activity* Isolates from Sentry global collection obtained 1/01-12/04 Organism N % S (MIC 2 µg/ml) Acinetobacter baumannii Enterobacter spp Klebsiella spp Pseudomonas aeruginosa * CLSI broth microdilution method Gales et al Clin Microbiol Infect. 12:315.

42 Since there are no FDA cleared MIC tests for colistin / polymyxin B, what are our options for testing? Send to reference lab for reference broth microdilution or agar dilution MICs Etest or other commercial test (e.g. Trek) - research use only [Disk diffusion for P. aeruginosa (not optimal)] BD package insert - wise to confirm S with MIC Currently at UCLA, perform reference broth microdilution (in-house prepared panels)

43 Inoculum preparation: Use saline Stay on lighter side of McFarland 0.5 Read at h (not beyond 18 h)

44 What should we know about testing/ reporting tigecycline? Class: glycylcycline; administered by IV route No CLSI breakpoints FDA breakpoints OK to use and report without comment Poor activity against Proteus / Providencia / Morganella Review tigecycline for MDR GNR Kelesidis et al J Antimicrob Chemother. 62:895. Pseudomonas aeruginosa

45 Tigecycline FDA Breakpoints Tigecycline (Prescribing Information)

46 Acinetobacter baumannii Tigecycline No CLSI or FDA breakpoints for Acinetobacter spp. Suggest report MIC without interpretation (test on request only) There have been reports of the development of tigecycline resistance in Acinetobacter infections seen during the course of standard treatment. Monitor with repeat C&S Wyeth 2009 update to product insert (2009)

47 Additional Drugs a to Consider for AST of MDR (upon MD request) Antimicrobial Agent Colistin (or polymyxin B) P. aeruginosa A. baumannii Yes Yes Doripenem Yes b Yes b Tigecycline No??? Others?????? a beyond those listed in CLSI M100-S21 b similar in vitro activity to that of imipenem and meropenem; use FDA breakpoints

48 Summary (1) CLSI has specific AST and reporting recommendations for several non- Enterobacteriaceae. Piperacillin-tazobactam is not considered superior to piperacillin for P. aeruginosa. Ertapenem and tigecycline are not considered antipseudomonal agents. There will be new CLSI breakpoints for several betalactams and P. aeruginosa in 2012.

49 Summary (2) Testing isolates of P. aeruginosa from CF patients can be difficult; there is no standard recommendation for testing mixed morphotypes in a single inoculum. A. baumannii and S. maltophilia are often colonizers and may not require AST (e.g., when isolated from respiratory specimens). There are few drugs with activity against S. maltophilia. There is no standard definition of MDR that must be used by all healthcare facilities.

50 Summary (3) Colistin / polymyxin B are drugs of last resort that may need to be tested on MDR gramnegative bacteria; resistance to these agents can be acquired. There are no breakpoints for tigecycline and Acinetobacter spp.

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