Senior Talk Alina Iovleva Content Expert: Dr. Robert A. Bonomo Combination vs. Monotherapy in treatment of Carbapenem Resistant Acinetobacter baumanii (CRAB) infections Senior Talk Alina Iovleva Content Expert: Dr. Robert A. Bonomo

Learning Objectives: 1.Epidemiology and significance 2. Mechanisms of resistance 3. Drugs available to treat Carbapenem Resistant A. baumannii 4. Combination vs Monotherapy in A. baumannii treatment 5. Novel approaches to treatment of XDR infections

Case: 57 y.o NH resident, with COPD, HTN, OSA, and obstructive uropathy, presented to the hospital with acute renal failure and respiratory failure requiring intubation. She was found to have pneumonia and was started on Vancomycin/piperacillin-tazobactam. She improved on therapy, extubated and discharged back to NH. She returns 3 days later with respiratory failure. Sputum growing A. baumanii.

Susceptibilities come back and are as above. Looks quite dismal. Then you go to uptodate and try to figure out what kind of bug it is and how to treat it

Acinetobacter spp. G – coccobacilli, strictly aerobic, non-motile, catalase positive and oxidase negative, glucose non-fermenter group contains 34 genomic species Ubiquitous (soil, water, hydrocarbon sludge) A.baumannii complex found almost exclusively in hospitals

Acinetobacter calcoaceticus- baumannii complex Acinetobacter calcoaceticus, A. baumannii, A.pittii, A. nosocomialis genetically highly related and difficult to distinguish phenotypically and biochemically 25% Acinetobacter isolates are misidentified as A. baumannii by most commercial methods. Acinetobacter calcoaceticus – nonpathogenic Higgins, P.G., et al., A PCR-based method to differentiate between Acinetobacter baumannii and Acinetobacter genomic species 13TU. Clinical Microbiology and Infection, 2007. 13(12): p. 1199-1201

Risk Factors for CRAB infection: Recent exposure to antibiotics, esp carbapenems and 3rd generation cephalosporins Presence of CVC or urinary catheter Severity of illness Large hospital size (>500) Prolonged ICU stay Lin, M.F. and C.Y. Lan, Antimicrobial resistance in Acinetobacter baumannii: From bench to bedside. World J Clin Cases, 2014. 2(12): p. 787-814.

Bad Bugs, No Drugs, No ESKAPE Enterococcus faecium (VRE) Staphylococcus aureus (MRSA) Klebsiella pneumonia Acinetobacter baumannii Pseudomonas aerugenosa Enterobactereceae 2/3 of nosocomial infections And present therapeutic challenges due to limited treatment options due to resistance Boucher, H.W., et al., Bad bugs, no drugs: no ESKAPE! An update from the Infectious Diseases Society of America. Clin Infect Dis, 2009. 48(1): p. 1-12.

CDC. Antibiotic Resistance Threats in the United States (2013)

Resistance Terminology MDR – resistant to 1 agent in 3 antimicrobial groups (ex: R to ceftriaxone, Bactrim, Cipro) XDR –resistance to 1 agent in all but 2 antimicrobial groups (ex: only sensitive to tigecycline and colistin) PDR- resistant to all antimicrobial agents

50-70% of Ab clinical isolates are now extensively Drug Resistant (XDR; i.e. resistant to all antibiotics except colistin or tigecycline), reflecting a >15-fold increase since 2000. Number of PDR strains of Ab, resistant to tigecycline and colistin are increasing Perez et al AAC 2007, Talbot and others, 2006, CID; Talbot ERAIT, 2009, Boucher CID 2009

Does resistance matter? BSI by XDR Ab cause >50-60% mortality In a recent study 13,796 patients in 1,265 ICUs from 75 countries, Ab was one of only two of 19 microorganisms strongly linked (p<0.01) to increased mortality by multivariate analysis; Odds ratio for death: 1.53 McGowan ICHE 2019, Hoffman et al, ICHE 2010, McGowan AJM 2006 Paterson CID 2006, Perez AAC 2007, Vincent JAMA 2009, Gordon JAC 2009

Mortality: 16-76% from 8% to 35%, according to strain and type of infection (Falagas & Rafailidis, 2007). Accordingly, different A. baumannii strains could be endowed with different pathogenic potential, as suggested by two studies using the mouse model of pneumonia: an MDR strain isolated from the blood culture of a patient with nosocomial pneumonia showed 80% mortality to mice, in contrast to 13% mortality for a strain causing meningitis (Eveillard et al., 2010), while a strain belonging to international clone 1 (see below) and a sporadic isolate were more virulent than a strain belonging to international clone 3 and the type strain (de Breij et al., 2012). Differences in mortality may be attributable to the expression of specific virulence factors and determinants. For example, two strains with the same PFGE profile, where one was a mucoid isolate from cerebrospinal fluid and the other was a nonmucoid isolate from a ventriculo peritoneal catheter, showed mortality rates of 48% and 19%, respectively, in a mouse model of pneumonia (Eveillard et al., 2010). Lemos, E.V., et al., Carbapenem resistance and mortality in patients with Acinetobacter baumannii infection: systematic review and meta-analysis. Clin Microbiol Infect, 2014. 20(5): p. 416-23.

Evolution of resistance 1970s-> sensitive to amoxicillin and nalidixic acid 1980s-> reports of increasing resistance 1990s -> first reports of imipenem resistance 2010-> 49% resistant to carbapenems -> horizontal gene transfer -> genome fluidity

Survey of “Resistance genes” in A. baumannii bla AMEs QRDR RND Efflux pumps OMPs Tet ADC aacC1 gyrA AdeABC HMP-AB tetA OXA aacC2 parC AdeM OmpA tetB IMP aacC3 AdeIJK 33-36 kDa tetM VIM, GIM SIM, SPM, NDM aacA4 AdeS CraS AdeDE 25/29 kDa CarO tetX PER aphA1 Res Is?? OprD (43kDA) PBPs TEM* aphA6 AbaR 1-10 OmpW SHV aadA1 Col R pmrAB 44, 47kDa, 22 integrons CTX-M rmt* lpxABC OMVs

“The Resistance Island” 86 Kb, 88 orfs, 82 orfs from another source and 45 resistance genes The sequence analysis of A. baumannii AYE antibacterial resistance genes indicates that frequent genetic exchanges take place with Pseudomonas spp., Salmonella spp., or Escherichia spp. This repetition is likely due to a duplication, which suggests a transposition mechanism for the insertion. However, no inverted repeats characteristic of transposons were found at the extremities of the island. The 86-kb region was classified as a genomic island (and designated AbaR1) on the basis of its size (>10 kb), marked G + C content difference from the rest of the chromosomes (52.8% versus 38.8%), the presence of genes associated with genome instability such as integrases, transposases, and insertion sequences, and the diverse phylogenetic origin of the associated ORFs [11]. At the same position, flanked by identical nucleotide sequences and within the homologous ATPase ORF, the A. baumannii strain SDF genome sequence exhibits a genomic island (designated AbaG1), albeit only 19,632 bp in length, with a G + C content of 31.3% Another unexpected finding was the presence of a similar structure in the genome of susceptible strain SDF, identically inserted in the homologous ATPase-like ORF. This genomic island was found in an “empty” state, exhibiting mobility-associated genes but no resistance markers. This coincidental genetic insertion in the two strains strongly suggests that this ATPase ORF constitutes a specific hotspot of genomic instability in the A. baumannii genome. This prompted us to investigate whether this feature was common to all A. baumannii strains. Using a polymerase chain reaction assay based on the conserved ATPase ORF flanking sequences (Protocol S1), 17 (77%) out of the 22 clinical A. baumannii isolates were found to exhibit an intact ATPase ORF. These 17 isolates included 11 isolates resistant to several antibiotic families, including β-lactams, and six susceptible to β-lactams. Among the five isolates exhibiting an interrupted ATPase ORF, four were resistant to most β-lactams except imipenem, including some that were also resistant to other antibiotic families, and one was susceptible to β-lactams but resistant to cotrimoxazole and rifampin (Protocol S1). The presence of a genomic island within the ATPase ORF is thus not a conserved feature among isolates, and its absence at this location is not predictive of the observed pattern of antibiotic susceptibility. Finally, our last surprise was the identification of several putative resistance genes in a strain not exhibiting the associated phenotype. This was the case for two putative β-lactamases (present in the AYE and SDF), including the class D β-lactamase blaOXA-69. The expression of OXA-69 in E. coli resulted in low levels of carbapenem resistance [35], and its sequence is 97% identical to the OXA-51 carbapenemase, found associated with full carbapenem resistance [41]. However, the presence of blaOXA-69 in the susceptible AYE strain suggests that it might only be a step away from acquiring this new resistance through subtle changes in expression level or a specific mutation or series of mutations that alter the substrate profile and enhance catalytic activity. Besides the direct acquisition of genetic material from resistant bacterial species, the maintenance of spare copies of “ready-to-optimize” resistance genes in the genome of A. baumannii, perhaps selected by exposure to subinhibitory levels of the drug in the environment, might also play a role in its rapid adaptation to new derivatives of the major antibiotic classes. AbaRs: complexity is growing! Fournier et al., PLoS Genet. 2006 Jan;2(1):e7. Epub 2006 Jan 13.

Difficulties in studying A.baumanii Unreliable identifications tests Unreliable susceptibility tests Fluid genome and fast development of resistance

Drugs available to treat resistant A.baumannii Colistin Tigecycline Sulbactam Rifampin Fosfomycin Minocyline Vancomycin

Monotherapy vs Combination Therapy

Monotherapy(MT) vs combination(CT) therapy for sepsis due to MDR A Monotherapy(MT) vs combination(CT) therapy for sepsis due to MDR A.baumannii: analysis of a multicenter prospective cohort. Lopez-Cortes et al. Prospective observational study 28 Spanish hospitals Primary outcome: 30 day mortality Secondary outcome: all-cause 14 day mortality MT -> use of single agent active in vitro Colistin (46) Carbapenem(10) Tigecycline (5) Sulbactam (5) Tetracycline (2) CT-> use of 2 or more active drugs Bitherapy with carbapenem was considered MT when carbapenem MIC was >32 and CT when it was lower J Antimicrob Chemother, 2014. 69(11): p. 3119-26.

Monotherapy(MT) vs combination(CT) therapy for sepsis due to MDR A Monotherapy(MT) vs combination(CT) therapy for sepsis due to MDR A.baumannii: analysis of a multicenter prospective cohort. Lopez-Cortes et al. CT therapies: Colistin+tigecycline (9) Carbapenem+tigecycline (4) Colistin+carbapenem(3) Colistin+sulbactam (2) Colistin+AG(2) Colistin +rifampicin(2) Carbapenem+AG(2) Tigecycline+rifampicin(2) Tigecycline+AG(1) Colistin+tigecycline+carbapenem+AG(3) Colistin+tigecycline+AG(2) Tigecycline+carbapenem+rifampicin(1) J Antimicrob Chemother, 2014. 69(11): p. 3119-26.

Monotherapy(MT) vs combination(CT) therapy for sepsis due to MDR A Monotherapy(MT) vs combination(CT) therapy for sepsis due to MDR A.baumannii: analysis of a multicenter prospective cohort. Lopez-Cortes et al. No mortality benefit from using CT compared with MT 30 day mortality : MT 23.5% vs CT 24.2 % RR 1.03 CI 0.49-2.16 P=0.94 Multivariate analysis of 30 day survival: also showed no trend towards reduced mortality Problems with the study: Low colistin dose ?High rate of inappropriate empirical treatment? Several types of infection CT and MT groups made up of multiple agents Small sample size Did not look into microbiological eradication

Excess Mortality Associated with Colistin-Tigecycline compared with colistin-carbapenem combination therapy for XDR A.baumannii Bacteremia: a multicenter prospective observational study. Cheng et al Primary outcome: 14 day mortality Colistin- tigecycline (29 patients) Colistin-carbapenem (26 patients) 14 day mortality 35% vs 15% (p=0.105) In hospital mortality 69% vs 50% (p=0.152) Subgroup analysis of 14 day mortality for Tig MIC >2 showed HR of 6.93 compared to colistin-carbapenem (1.61-29). Crit Care Med, 2015. 43(6): p. 1194-204

Comparison of colistin-carbapenem, colistin-sulbactam, and colistin plus other antibacterial agents for the treatment of XDR A. baumannii bloodstream infections. Batirel et al. Retrospective observational multicenter study 27 Turkish tertiary hospitals Primary outcome: 14 day mortality Secondary outcome: clinical and microbiologic response MT: colistin (36) CT: Colistin+carbapenem (102) Colistin+sulbactam (69) Colistin +other abx (43) Eur J Clin Microbiol Infect Dis, 2014. 33(8): p. 1311-22.

Comparison of colistin-carbapenem, colistin-sulbactam, and colistin plus other antibacterial agents for the treatment of XDR A. baumannii bloodstream infections. Batirel et al. 14 day survival: CT 68.2% vs MT 55.5% p=0.14 In-hospital crude mortality CT 52.3% vs MT 72.2% p= Microbiologic eradication CT 79.9% vs MT 55.6% p=0.001 No significant survival difference was found in clinical and microbiological outcomes and 14 day survival between three combination groups Weakness: more late therapy in MT group (but not significantly) Eur J Clin Microbiol Infect Dis, 2014. 33(8): p. 1311-22.

Comparison of colistin-carbapenem, colistin-sulbactam, and colistin plus other antibacterial agents for the treatment of XDR A. baumannii bloodstream infections. Batirel et al. Eur J Clin Microbiol Infect Dis, 2014. 33(8): p. 1311-22.

Comparison of colistin and colistin/sulbactam for treatment of multidrug resistant Ab VAP. Kalin et al Retrospective, n=89

Colistin and rifampicin compared with colistin alone for treatment of serious infections due to XDR A.baumannii: a multicenter randomized clinical trial. Durante-Mangoni et al Italy, N=210 Weaknesses: 20.8% patient’s in monotherapy group received adjunctive meropenem or tigecycline, which would lower then expected mortality. Not blinded No difference in mortality Increased microbiologic eradication Clin Infect Dis, 2013. 57(3): p. 349-58.

Colistin vs. the combination of colistin and rifampicin for the treatment of carbapenem-resistant Acinetobacter baumannii ventilator-associated pneumonia. Aydemir et al Epidemiol Infect, 2013. 141(6): p. 1214-22

94 patients infected with CRAB, col alone or col + fosfo for 7 to 14 days.. Combo better micro response and a trend toward better clinical outcomes and lower mortality than mono

Retrospective multicenter study Clinical Experience of Colistin-Glycopeptide Combination in Critically Ill Patients Infected with Gram-Negative Bacteria Petrosillo, et al Retrospective multicenter study Patients in ICU who received colistin for GNB infection (n =184) VAP (64.5%) and BSI (20%) Outcomes: 30 day mortality and nephrotoxicity MDR AB(59.6%), CR Klebsiella (14.5%) MDR Psa (18.7%) 16% had G+ infection. 40% received CGC. Improved survival no difference in nephrotoxicity. Antimicrob Agents Chemother, 2014. 58(2): p. 851-8.

Clinical Efficacy and Safety of the Combination of Colistin plus Vancomycin for the Treatment of Severe Infections Caused by Carbapenem-Resistant Acinetobacter baumannii Garnacho_Montero et al retrospective study of VAP or bacteremia by CRAB N=57 Colistin +Vancomycin (29) vs colistin alone (28). 28 day mortality was 48% vs 50% Baseline characteristics, clinical cure, microbiological eradication, and mortality were similar in both groups but the rate of acute kidney injury was higher in group I (55.2 vs. 28%; p = 0.04). Chemotherapy, 2013. 59(3): p. 225-31.

Tetracyclines for multidrug-resistant A. baumannii infections Tetracyclines for multidrug-resistant A.baumannii infections. Falagas et al 10 retrospective studies reviewed of using minocyline/doxycycline alone or in combination with other abx. N=156 Clinical success achieved in 76.9% Mortality in 20 out of 100 available cases Unable to extrapolate data for monotherapy vs combination therapy

Drugs to Rx Ab Drug Dosing +/- Combination vs Monotherapy Colistin 5 mg/kg/d load followed by 5mg/kg/2-3 doses Mainstay therapy Poor lung penetration Difficulty dosing Combo> mono Nephrotoxicty ??? Fosfomycin* 4 grams/q12 Well tolerated No IV in US Resistance in mono Rx Combination tx: no mortality benefit, increased microbiologic eradication Rifampin 600 mg q12-24 Toxic Sulbactam 3-9 grams /day Can’t get alone in US Increasing rates of resistance

Drugs to Rx Ab Drug Dosing +/- Combination vs Monotherapy Tigecycline 100 mg load, 50 mg q12 Bacteriostatic Low blood levels ?increased mortality if MIC>2 Minocycline* ??? High rates of resistance in US Seems promising but needs Prospective/randomized studies Vancomycin 10-15 mg q12 In vitro synergy nephrotoxicity ??? (probably no benefit)

Monotherapy Vs Combination therapy Studies Sites of infection Drugs Monotherapy Vs Combination therapy Studies Patients Bugs

Summary Evidence is inconclusive and hard to interpret Common issues : Multiple compared antibiotics and different sites of infections Heterogeneous organisms and mechanisms of resistance Small number of patients, few randomized studies Late therapy Is monotherapy truly monotherapy? Patients often co-infected with other organisms and receive Abx for it. Ex: Vancomycin, meropenem. Does microbiologic eradication matter even though there is no mortality difference? Most authors recommend using combination therapy in severe cases.

References: 1. Aydemir, H., et al., Colistin vs. the combination of colistin and rifampicin for the treatment of carbapenem-resistant Acinetobacter baumannii ventilator-associated pneumonia. Epidemiol Infect, 2013. 141(6): p. 1214-22. 2. Batirel, A., et al., Comparison of colistin-carbapenem, colistin-sulbactam, and colistin plus other antibacterial agents for the treatment of extremely drug-resistant Acinetobacter baumannii bloodstream infections. Eur J Clin Microbiol Infect Dis, 2014. 33(8): p. 1311-22. 3. Cheng, A., et al., Excess Mortality Associated With Colistin-Tigecycline Compared With Colistin-Carbapenem Combination Therapy for Extensively Drug-Resistant Acinetobacter baumannii Bacteremia: A Multicenter Prospective Observational Study. Crit Care Med, 2015. 43(6): p. 1194-204. 4. Claeys, K.C., A.D. Fiorvento, and M.J. Rybak, A Review of Novel Combinations of Colistin and Lipopeptide or Glycopeptide Antibiotics for the Treatment of Multidrug- Resistant Acinetobacter baumannii. Infect Dis Ther, 2014. 5. Doi, Y., G.L. Murray, and A.Y. Peleg, Acinetobacter baumannii: evolution of antimicrobial resistance-treatment options. Semin Respir Crit Care Med, 2015. 36(1): p. 85- 98. 6. Durante-Mangoni, E., et al., Colistin and rifampicin compared with colistin alone for the treatment of serious infections due to extensively drug-resistant Acinetobacter baumannii: a multicenter, randomized clinical trial. Clin Infect Dis, 2013. 57(3): p. 349-58. 7. Falagas, M.E., et al., Tetracyclines for multidrug-resistant Acinetobacter baumannii infections. Int J Antimicrob Agents, 2015. 45(5): p. 455-60. 8. Garnacho-Montero, J., et al., Clinical efficacy and safety of the combination of colistin plus vancomycin for the treatment of severe infections caused by carbapenem- resistant Acinetobacter baumannii. Chemotherapy, 2013. 59(3): p. 225-31. 9. Imperi, F., et al., The genomics of Acinetobacter baumannii: insights into genome plasticity, antimicrobial resistance and pathogenicity. IUBMB Life, 2011. 63(12): p. 1068-74. 10. Kalin, G., et al., Comparison of colistin and colistin/sulbactam for the treatment of multidrug resistant Acinetobacter baumannii ventilator-associated pneumonia. Infection, 2014. 42(1): p. 37-42. 11. Karageorgopoulos, D.E., et al., Tigecycline for the treatment of multidrug-resistant (including carbapenem-resistant) Acinetobacter infections: a review of the scientific evidence. J Antimicrob Chemother, 2008. 62(1): p. 45-55. 12. Khawcharoenporn, T., et al., Colistin-based treatment for extensively drug-resistant Acinetobacter baumannii pneumonia. Int J Antimicrob Agents, 2014. 43(4): p. 378-82.

References: 13. Lemos, E.V., et al., Carbapenem resistance and mortality in patients with Acinetobacter baumannii infection: systematic review and meta- analysis. Clin Microbiol Infect, 2014. 20(5): p. 416-23. 14. Lin, M.F. and C.Y. Lan, Antimicrobial resistance in Acinetobacter baumannii: From bench to bedside. World J Clin Cases, 2014. 2(12): p. 787-814. 15. Lopez-Cortes, L.E., et al., Monotherapy versus combination therapy for sepsis due to multidrug-resistant Acinetobacter baumannii: analysis of a multicentre prospective cohort. J Antimicrob Chemother, 2014. 69(11): p. 3119-26. 16. Pachon, J. and M.J. McConnell, Considerations for the development of a prophylactic vaccine for Acinetobacter baumannii. Vaccine, 2014. 32(22): p. 2534-6. 17. Perez, F. and R.A. Bonomo, Vaccines for Acinetobacter baumannii: thinking "out of the box". Vaccine, 2014. 32(22): p. 2537-9. 18. Petrosillo, N., et al., Clinical experience of colistin-glycopeptide combination in critically ill patients infected with Gram-negative bacteria. Antimicrob Agents Chemother, 2014. 58(2): p. 851-8. 19. Poirel, L., R.A. Bonnin, and P. Nordmann, Genetic basis of antibiotic resistance in pathogenic Acinetobacter species. IUBMB Life, 2011. 63(12): p. 1061-7. 20. Poulikakos, P., G.S. Tansarli, and M.E. Falagas, Combination antibiotic treatment versus monotherapy for multidrug-resistant, extensively drug-resistant, and pandrug-resistant Acinetobacter infections: a systematic review. Eur J Clin Microbiol Infect Dis, 2014. 33(10): p. 1675-85. 21. Shields, R.K., et al., Epidemiology, clinical characteristics and outcomes of extensively drug-resistant Acinetobacter baumannii infections among solid organ transplant recipients. PLoS One, 2012. 7(12): p. e52349. 22. Siontorou, C.G., Nanobodies as novel agents for disease diagnosis and therapy. Int J Nanomedicine, 2013. 8: p. 4215-27. 23. Sirijatuphat, R. and V. Thamlikitkul, Preliminary study of colistin versus colistin plus fosfomycin for treatment of carbapenem-resistant Acinetobacter baumannii infections. Antimicrob Agents Chemother, 2014. 58(9): p. 5598-601. 24. Viehman, J.A., M.H. Nguyen, and Y. Doi, Treatment options for carbapenem-resistant and extensively drug-resistant Acinetobacter baumannii infections. Drugs, 2014. 74(12): p. 1315-33.

Big picture: Regardless, mortality is still high and available treatments are limited!

Are we entering post-antibiotic era?

CDC. Antibiotic Resistance Threats in the United States (2013)

Ways to battle resistance: Antibiotic Stewardship Rapid diagnostics Novel therapies

Novel therapies: Vaccination Passive antibody therapy Antibacterial peptides

A.Baumannii vaccine development Pachon, J. and M.J. McConnell, Considerations for the development of a prophylactic vaccine for Acinetobacter baumannii. Vaccine, 2014. 32(22): p. 2534-6.

Vaccines: unanswered questions Who to immunize? Will critically ill patient able to mount a response to vaccine? Perez, F. and R.A. Bonomo, Vaccines for Acinetobacter baumannii: thinking "out of the box". Vaccine, 2014. 32(22): p. 2537-9.