Skip to main content
PMC home page
The Brazilian Journal of Infectious Diseases logoLink to The Brazilian Journal of Infectious Diseases
letter
. 2017 Apr 20;21(5):569–573. doi: 10.1016/j.bjid.2017.03.008

The in vitro activity of ceftazidime–avibactam against 417 Gram-negative bacilli collected in 2014 and 2015 at a teaching hospital in São Paulo, Brazil

Flávia Rossi a, Ana P Cury a, Maria RG Franco a, Raymond Testa b, Wright W Nichols b,◊,⁎
PMCID: PMC9425450  PMID: 28435011

Dear Editor:

Avibactam is a new non-β-lactam β-lactamase inhibitor that restores the in vitro activity of ceftazidime against isolates of Enterobacteriaceae and Pseudomonas aeruginosa that harbor Ambler molecular class A, class C and some class D β-lactamases,1 but not those harboring metallo-β-lactamases.2 Ceftazidime–avibactam and comparator antibacterial agents were tested by reference broth microdilution against 417 non-repetitive Gram-negative bacilli (387 unselected, plus 30 selected blaKPC-positive, meropenem–nonsusceptible, Klebsiella pneumoniae) collected prospectively from medical centers at Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Brazil, in 2014 and 2015. Specimen sources were associated with bloodstream, respiratory, urinary, gynecological, intra-abdominal, wound, or skin and skin structure infections. Isolates defined as “non-selected” were collected without phenotypic pre-selection so that they represented those encountered clinically. Only one isolate per patient was included in the study. Minimum inhibitory concentrations (MICs), one per isolate, were determined by reference Clinical and Laboratory Standards Institute (CLSI) broth microdilution methods3 using frozen microtiter plates pre-loaded with antibiotic-containing growth medium. MICs of ceftazidime–avibactam were measured by varying the concentration of ceftazidime in twofold increments with avibactam at a fixed concentration of 4 mg/L.3 Quality control (data not shown) was achieved according to CLSI guidelines3 using American Type Culture Collection (ATCC) isolates, Escherichia coli ATCC 25922, E. coli ATCC 35218, K. pneumoniae ATCC 700603, and P. aeruginosa ATCC 27853. The test results are summarized in Table 1.

Table 1.

In vitro activities of ceftazidime, ceftazidime–avibactam, and comparator antibiotics against Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter baumannii isolated from patients in São Paulo, Brazil, 2014–2015.

Organism (no. of isolates) and antibiotic MIC (mg/L)
 %Sa %Ra
MIC50 MIC90 Range
Citrobacter freundii (25)
 Ceftazidime 0.5 >128 0.06 to >128 68.0 28.0
 Ceftazidime–avibactam 0.25 0.5 0.06–1 100 0
 Cefepime ≤0.06 8 ≤0.06–32 80.0 8.0
 Piperacillin/tazobactam 8 >128 2 to >128 72.0 20.0
 Meropenem 0.25 0.5 0.12–4 96.0 4.0
 Colistin 0.5 1 0.5–2 100 0
 Amikacin 1 2 0.5–8 100 0
 Levofloxacin 0.25 32 0.03 to >32 68.0 28.0



Citrobacter koseri (23)
 Ceftazidime 0.25 0.25 0.06–1 100 0
 Ceftazidime–avibactam 0.12 0.25 0.06–0.5 100 0
 Cefepime ≤0.06 0.12 ≤0.06–0.5 100 0
 Piperacillin/tazobactam 4 8 0.25–32 91.3 0
 Meropenem 0.25 0.25 0.12–0.5 100 0
 Colistin 0.5 0.5 0.25–0.5 100 0
 Amikacin 1 2 0.12 to >128 95.7 4.3
 Levofloxacin 0.03 0.25 ≤0.015–1 100 0



Enterobacter aerogenes (25)
 Ceftazidime 0.25 64 0.06–64 72.0 28.0
 Ceftazidime–avibactam 0.12 0.5 0.06–0.5 100 0
 Cefepime 0.06 0.5 ≤0.06–64 92.0 8.0
 Piperacillin/tazobactam 4 128 2 to >128 68.0 24.0
 Meropenem 0.25 1 0.25–4 96.0 4.0
 Colistin 0.5 1 0.25–1 100 0
 Amikacin 1 2 0.5–8 100 0
 Levofloxacin 0.06 1 0.03–32 92.0 8.0



Enterobacter cloacae (26)
 Ceftazidime 0.5 128 0.12 to >128 73.1 26.9
 Ceftazidime–avibactam 0.25 1 0.06–2 100 0
 Cefepime 0.12 32 ≤0.06 to >128 69.2 23.1
 Piperacillin/tazobactam 4 128 1 to >128 76.9 11.5
 Meropenem 0.25 0.5 0.12–1 100 0
 Colistin 0.5 >32 0.5 to >32 76.9 23.1
 Amikacin 1 4 0.5–16 100 0
 Levofloxacin 0.06 8 0.03 to >32 88.5 11.5



Escherichia coli (27)
 Ceftazidime 0.25 1 0.12–64 96.3 3.7
 Ceftazidime–avibactam 0.12 0.25 0.06–0.25 100 0
 Cefepime ≤0.06 0.5 ≤0.06–1 100 0
 Piperacillin/tazobactam 4 16 2–64 92.6 0
 Meropenem 0.25 1 0.12–2 96.3 0
 Colistin 0.5 1 0.25–1 100 0
 Amikacin 2 2 0.5–4 100 0
 Levofloxacin 0.03 32 ≤0.015–32 66.7 25.9



Klebsiella oxytoca (25)
 Ceftazidime 0.12 0.5 0.06–0.5 100 0
 Ceftazidime–avibactam 0.12 0.5 0.03–0.5 100 0
 Cefepime ≤0.06 0.12 ≤0.06–0.5 100 0
 Piperacillin/tazobactam 4 16 0.25 to >128 96.0 4.0
 Meropenem 0.25 2 0.12–4 64.0 8.0
 Colistin 0.5 1 0.25–4 96.0 4.0
 Amikacin 1 8 0.5–16 100 0
 Levofloxacin 0.06 1 ≤0.015–8 96.0 4.0



Klebsiella pneumoniae (27)
 Ceftazidime 32 >128 0.06 to >128 37.0 63.0
 Ceftazidime–avibactam 0.5 4 ≤0.015–8 100 0
 Cefepime 64 >128 ≤0.06 to >128 37.0 55.6
 Piperacillin/tazobactam 128 >128 2 to >128 40.7 55.6
 Meropenem 0.5 >32 0.12 to >32 70.4 29.6
 Colistin 0.5 32 0.5 to >32 85.2 14.8
 Amikacin 2 8 0.5–32 96.3 0
 Levofloxacin 16 >32 0.06 to >32 40.7 59.3



Klebsiella pneumoniae (blaKPC) (30)
 Ceftazidime 128 >128 8 to >128 0 93.3
 Ceftazidime–avibactam 2 4 0.25–64 96.7 3.3
 Cefepime 128 >128 2 to >128 3.3 96.7
 Piperacillin/tazobactam >128 >128 128 to >128 0 100
 Meropenem >32 >32 8 to >32 0 100
 Colistin 8 >32 0.5 to >32 46.7 53.3
 Amikacin 2 16 1 to >128 90.0 6.7
 Levofloxacin 32 >32 0.06 to >32 6.7 93.3



Morganella morganii (25)
 Ceftazidime 0.5 8 0.06–128 80.0 12.0
 Ceftazidime–avibactam 0.06 0.25 0.03–2 100 0
 Cefepime ≤0.06 8 ≤0.06 to >128 84.0 8.0
 Piperacillin/tazobactam 1 8 0.25–128 92.0 4.0
 Meropenem 1 1 0.5–1 100 0
 Colistin >32 >32 >32 to >32 0 100
 Amikacin 4 8 1–8 100 0
 Levofloxacin 1 >32 0.03 to >32 60.0 36.0



Proteus mirabilis (25)
 Ceftazidime 0.06 0.5 0.06–8 96.0 0
 Ceftazidime–avibactam 0.06 0.06 0.03–0.12 100 0
 Cefepime 0.12 0.5 ≤0.06–32 92.0 4.0
 Piperacillin/tazobactam 0.5 1 0.25–2 100 0
 Meropenem 1 1 0.5–2 96.0 0
 Colistin >32 >32 >32 to >32 0 100
 Amikacin 2 8 1–128 96.0 4.0
 Levofloxacin 0.06 4 0.03–8 88.0 4.0



Proteus vulgaris (22)
 Ceftazidime 0.12 0.25 0.03–0.5 100 0
 Ceftazidime–avibactam 0.06 0.12 0.03–0.25 100 0
 Cefepime 0.12 0.5 ≤0.06–2 100 0
 Piperacillin/tazobactam 0.5 1 0.12–2 100 0
 Meropenem 1 2 0.5–2 86.4 0
 Colistin >32 >32 >32 to >32 0 100
 Amikacin 2 4 0.5–16 100 0
 Levofloxacin 0.03 0.06 ≤0.015–4 95.5% 0



Providencia rettgeri (14)
 Ceftazidime 0.12 0.5 0.06–0.5 100 0
 Ceftazidime–avibactam 0.06 0.25 0.03–0.5 100 0
 Cefepime ≤0.06 0.12 ≤0.06–0.12 100 0
 Piperacillin/tazobactam 1 4 0.5–4 100 0
 Meropenem 0.5 0.5 0.12–0.5 100 0
 Colistin >32 >32 8 to >32 0 100
 Amikacin 4 8 0.5–32 92.9 0
 Levofloxacin 1 >32 0.12 to >32 57.1 42.9



Providencia stuartii (22)
 Ceftazidime 4 16 0.25 to >128 59.1 31.8
 Ceftazidime–avibactam 0.5 1 0.12 to >128 95.5 4.5
 Cefepime >128 >128 ≤0.06 to >128 22.7 72.7
 Piperacillin/tazobactam 8 64 1–128 72.7 4.6
 Meropenem 0.5 0.5 0.12–0.5 100 0
 Colistin >32 >32 >32 to >32 0 100
 Amikacin 2 8 0.5–64 90.9 4.6
 Levofloxacin >32 >32 0.25 to >32 4.5 95.5



Serratia marcescens (26)
 Ceftazidime 0.25 32 0.12 to >128 80.8 15.4
 Ceftazidime–avibactam 0.25 1 0.06–32 96.2 3.8
 Cefepime 0.25 >128 ≤0.06 to >128 80.8 19.2
 Piperacillin/tazobactam 4 >128 2 to >128 84.6 11.5
 Meropenem 0.5 1 0.25–4 96.2 3.8
 Colistin >32 >32 >32 to >32 0 100
 Amikacin 2 8 1–64 92.3 3.8
 Levofloxacin 0.25 1 0.03–4 96.2 0



Pseudomonas aeruginosa (25)
 Ceftazidime 4 >128 0.5 to >128 60.0 40.0
 Ceftazidime–avibactam 4 16 0.5–64 84.0 16.0
 Cefepime 4 128 1 to >128 52.0 40.0
 Piperacillin/tazobactam 16 >128 2 to >128 60.0 28.0
 Meropenem 4 >32 1 to >32 32.0 32.0
 Colistin 1 2 0.5–2 100 0
 Amikacin 4 8 1–8 100 0
 Levofloxacin 0.5 32 0.12–32 60.0 40.0



Acinetobacter baumannii (50)
 Ceftazidime >128 >128 1 to >128 18.0 82.0
 Ceftazidime–avibactam b >128 >128 2 to >128 nab na
 Cefepime 64 >128 1 to >128 14.0 80.0
 Piperacillin/tazobactam >128 >128 ≤0.06 to >128 14.0 82.0
 Meropenem >32 >32 2 to >32 16.0 84.0
 Colistin 0.5 1 0.25–32 98.0 2.0
 Amikacin 64 >128 1 to >128 30.0 56.0
 Levofloxacin 16 >32 0.06 to >32 20.0 72.0
Open in a new tab
a

%S, %R: percent of isolates interpreted as susceptible or resistant. MICs were interpreted according to CLSI criteria (breakpoints),3 except for colistin against Enterobacteriaceae and ceftazidime–avibactam, for which CLSI criteria are not available. MICs of colistin against Enterobacteriaceae were interpreted by EUCAST (European Committee on Antimicrobial Susceptibility Testing) criteria.4 MICs of ceftazidime–avibactam were interpreted according to criteria set by the United States Food and Drug Administration.5 Accordingly, the susceptible and resistant criteria for the Enterobacteriaceae were (mg/L), respectively: ceftazidime, MIC ≤4 and ≥16; ceftazidime–avibactam, MIC ≤8 and ≥16; cefepime, MIC ≤2 and ≥16; piperacillin/tazobactam, MIC ≤ 16 and ≥128; meropenem, MIC ≤ 1 and ≥4; colistin, MIC ≤2 and >2; amikacin, MIC ≤16 and ≥64; and levofloxacin, MIC ≤2 and ≥8. Criteria for susceptible and resistant for P. aeruginosa were (mg/L), respectively: ceftazidime, MIC ≤8 and ≥32; ceftazidime–avibactam, MIC ≤8 and ≥16; cefepime, MIC ≤8 and ≥32; piperacillin/tazobactam, MIC ≤16 and ≥128; meropenem, MIC ≤2 and ≥8; colistin, MIC ≤2 and ≥8; amikacin, MIC ≤16 and ≥64; and levofloxacin, MIC ≤2 and ≥8. The criteria used to interpret MIC values against A. baumannii were identical to those used for P. aeruginosa except for ceftazidime–avibactam, which lacks a breakpoint because the drug label does not include Acinetobacter spp., and colistin, the criterion of resistance to which was MIC ≥4 mg/L.

b

na: not applicable because A. baumanni is not an indicated species for ceftazidime–avibactam.5

Addition of avibactam at 4 mg/L decreased MICs of ceftazidime against unselected Enterobacteriaceae, especially K. pneumoniae, Citrobacter freundii, and Enterobacter cloacae, among which MIC90 values decreased from 128 to >128 mg/L to 0.5–4 mg/L. Among the unselected isolates of these three species 37–73% were susceptible to ceftazidime, whereas 100% were susceptible to ceftazidime–avibactam. The relatively large decreases in the MIC90 of ceftazidime caused by the addition of avibactam when testing clinical isolates of C. freundii, Enterobacter aerogenes, E. cloacae, Morganella morgannii, Providencia stuartii, and Serratia marcescens likely resulted from the ceftazidime-nonsusceptible isolates of those species producing stably derepressed AmpC β-lactamases.6 This is consistent with the observation that >90% of the isolates of those species remained susceptible to meropenem (Table 1). Of the 27 unselected isolates of K. pneumoniae tested, only 70.4% were susceptible to meropenem, and 37–41% were susceptible to the other β-lactam comparator agents tested, including the β-lactam/β-lactamase-inhibitor combination piperacillin-tazobactam. Susceptibility to levofloxacin was also low, at 40.7%, and almost 15% of the isolates lacked susceptibility to colistin. Of the 30 selected meropenem-nonsusceptible, blaKPC-positive, isolates of K. pneumoniae: none was susceptible to ceftazidime alone, but 29 (96.7%) were susceptible to ceftazidime–avibactam in vitro (MIC90, 4 mg/L). As expected, none of the β-lactam agents (except ceftazidime–avibactam) displayed appreciable activity against these isolates, and even susceptibility to colistin was compromised at 46.7% (Table 1). Susceptibility to amikacin was 90.0% (Table 1). This level of susceptibility of the blaKPC-positive isolates to ceftazidime–avibactam is consistent with the results of the global surveillance studies of carbapenem-resistant K. pneumoniae.2 In the case of E. coli, the range of MICs showed the avibactam effect, 0.12–64 mg/L for ceftazidime as opposed to 0.06–0.25 mg/L for ceftazidime–avibactam. Little to no avibactam effect was observed when testing ceftazidime–avibactam as opposed to ceftazidime against Citrobacter koseri, Klebsiella oxytoca, Proteus vulgaris, or Providencia rettgeri, as all isolates were already susceptible to ceftazidime.

Addition of avibactam decreased the MIC90 of ceftazidime against 25 unselected isolates of P. aeruginosa from >128 mg/L to 16 mg/L, resulting in 84% of isolates being interpreted as susceptible in vitro (Table 1), indicating a slightly lower level of susceptibility than has been found among isolates of this species in global surveillance studies. For example, in one recent global study, the MIC90 of ceftazidime–avibactam against 7062 isolates of P. aeruginosa was 8 mg/L, and 92% were susceptible.7 Avibactam inhibits the AmpC β-lactamase of P. aeruginosa and restores susceptibility to ceftazidime in isolates in which the mechanism of resistance is that of stable derepression of that enzyme.8 However, multidrug-resistant P. aeruginosa clone ST277 that frequently harbors metallo-β-lactamase SPM-1 is disseminated widely in Brazil8 and avibactam does not inhibit metallo-β-lactamases, which might explain the 16% resistance to ceftazidime–avibactam found here (Table 1). Nevertheless, the percent of the P. aeruginosa isolates in the present study that were susceptible to ceftazidime–avibactam was higher than the percent that were susceptible to the other β-lactam agents tested, including meropenem (32% susceptible) and piperacillin/tazobactam (60% susceptible) (Table 1).

The MIC90 of ceftazidime against 50 isolates of Acinetobacter baumannii was >128 mg/L whether avibactam was present or not, which is consistent with this species not being listed on the drug label.5

In conclusion, the in vitro antibacterial activity of ceftazidime–avibactam against bacteria isolated from patients in Brazil was consistent with results from other surveillance studies except that the percent susceptibility of the sample of clinical isolates of P. aeruginosa at 84% (Table 1) was somewhat lower than the proportions observed elsewhere,7 possibly related to the dissemination of the metallo-β-lactamase, SPM-1, in Brazil.8 The in vitro activity of ceftazidime–avibactam described in the present work is consistent with its recently-reported efficacy in phase 3 clinical studies.9

Conflicts of interest

WW Nichols and R Testa were employees of AstraZeneca at the time of the study and WWN is an AstraZeneca shareholder. Pfizer acquired the AstraZeneca product, ceftazidime-avibactam, in December 2016. The Hospital das Clinicas da Universidade de São Paulo Group declare no conflicts of interest.

Acknowledgements

We thank AstraZeneca for funding this study and TR Di Gioia and J Nobrega Jr for technical assistance.

References

  • 1.Lagacé-Wiens P.R.S., Walkty A., Karlowsky J.A. Ceftazidime–avibactam: an evidence-based review of its pharmacology and potential use in the treatment of Gram-negative bacterial infections. Core Evidence. 2014;9:13–25. doi: 10.2147/CE.S40698. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.deJonge B.L., Karlowsky J.A., Kazmierczak K.M., Biedenbach D.J., Sahm D.F., Nichols W.W. In vitro susceptibility to ceftazidime–avibactam of carbapenem-nonsusceptible Enterobacteriaceae isolates collected during the INFORM global surveillance study (2012–2014) Antimicrob Agents Chemother. 2016;60:3163–3169. doi: 10.1128/AAC.03042-15. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.CLSI . Clinical and Laboratory Standards Institute; Wayne, PA: 2015. Performance Standards for Antimicrobial Susceptibility Testing; Twenty-Fifth Informational Supplement. CLSI document M100-S25. [Google Scholar]
  • 4.European Committee on Antimicrobial Susceptibility Testing. 2015. Breakpoint tables for interpretation of MICs and zone diameters. Version 5.0. http://www.eucast.org/fileadmin/src/media/PDFs/EUCAST_files/Breakpoint_tables/v_5.0_Breakpoint_Table_01.pdf [Accessed September 27, 2016].
  • 5.Allergan. 2016. AVYCAZ (ceftazidime–avibactam) for injection, for intravenous use. Prescribing Information. 2016. http://www.accessdata.fda.gov/drugsatfda_docs/label/2016/206494s002lbl.pdf. [Accessed September 27, 2016].
  • 6.Curtis N.A.C., Eisenstadt R., Rudd C., White A.J. Inducible Type I β-lactamases of Gram-negative bacteria and resistance to β-lactam antibiotics. J Antimicrob Chemother. 1986;17:51–61. doi: 10.1093/jac/17.1.51. [DOI] [PubMed] [Google Scholar]
  • 7.Nichols W.W., deJonge B.L.M., Kazmierczak K.M., Karlowsky J.A., Sahm D.F. In vitro susceptibility of global surveillance isolates of Pseudomonas aeruginosa to ceftazidime–avibactam: INFORM 2012–2014. Antimicrob Agents Chemother. 2016;60:4743–4749. doi: 10.1128/AAC.00220-16. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8.Silveira M.C., Albano R.M., Asensi M.D., Carvalho-Assef A.P. Description of genomic islands associated to the multidrug-resistant Pseudomonas aeruginosa clone ST277. Infect Genet Evol. 2016;42:60–65. doi: 10.1016/j.meegid.2016.04.024. [DOI] [PubMed] [Google Scholar]
  • 9.Carmeli Y., Armstrong J., Laud P.J., et al. Ceftazidime–avibactam or best available therapy in patients with ceftazidime-resistant Enterobacteriaceae and Pseudomonas aeruginosa complicated urinary tract infections or complicated intra-abdominal infections (REPRISE): a randomised, pathogen-directed, phase 3 study. Lancet Infect Dis. 2016;16:661–673. doi: 10.1016/S1473-3099(16)30004-4. [DOI] [PubMed] [Google Scholar]

Articles from The Brazilian Journal of Infectious Diseases are provided here courtesy of Elsevier

RESOURCES