882 infection control & hospital epidemiology july 2017, vol. 38, no. 7


table 1. Resistance Rates of BL/IBL Combinations Against Escherichia coli, Klebsiella, and Proteus Species


BL/IBL combination (% of resistance in each group)


Enterobacterial Groups (No. of Isolates)


Community spectrum (878) Extended spectrum (ESBL) (62) Carbapenem-resistance spectrum(2) Total (942)


AMC SAM 2 (100) TZP


251 (28.6) 427 (48.6) 108 (12.3) 51 (82.2) 60 (96.8) 28 (45.2) 2 (100)


2 (100) 304 (32.3) 489 (51.9) 138 (14.6)


NOTE. BL/IBL, β-lactam/inhibitor of β-lactamase; AMC, amoxicillin/ clavulanate; SAM, ampicillin/sulbactam; TZP, piperacillin/tazobactam; ESBL, extended-spectrum β-lactamase.


in both community-based and ESBL-spectrum profiles. None of the combinations were active in vitro against CRE isolates. A more liberal use of carbapenems is not without


consequence and may result in the emergence of a resistance to this agent4 as well as others, such as polymyxins5,6 and fosfomycin,7 due to the influence of an increased demand, which may severely limit future treatment options. In this study, tazobactam was the most superior (while


sulbactam was the less active) IBL to inhibit β-lactamases, no matter their spectrum, as previously described elsewhere.1 Notably, these results obtained with TZP may reflect the increased activity of piperacillin. However, the applicable comparison is between amoxicillin and ampicillin due to the overlapping activities of these agents. Although SAM has historically been favored for its activity


against Acinetobacter, its activity is no longer observed, and its usefulness is questionable in community-based infections (eg, pyelonephritis, appendicitis, cholecystitis, complicated urinary infections, and others), which often require hospitali- zation and more appropriate empirical therapy protocols. For community-acquired infection of mild-to-moderate severity in adults, SAM is not recommended because of high rates of resistance to this agent among community-acquired E. coli, according to the guidelines by the Surgical Infection Society and the Infectious Diseases Society of America.8 Therefore, would nosocomial use of AMC (endovenous) not be more appropriate than SAM? Regardless, some important factors may influence this option:


First, although the addition of IBLs appears to reduce the hydrolyzing effect of β-lactamase enzymes on the β-lactam ring, their activity is diminished when a high concentration of bacteria is present, cf, “inoculum effect.”9 These contrasting distributions may be important because respiratory tract infections imply in a high inoculum of bacteria in a compartment where penetration of antibiotics may be impaired, whereas urinary tract infections have amoremoderateinoculumand β-lactams easily concentrate in the urine. Second, the presence of other mechanisms of β-lactam resistance, such as ampC β-lactamase overproduction or additional ESBLs, certainly act by reducing the activity of BL/IBLs.10 Third, our results are disturbing because the use of any BL/IBL combination is already ineffective against >10% of resistant organisms and should not be used unless hospital


surveys indicate >90%susceptibility, as indicated for quinolones, for example.8 In conclusion, our results show the superior activity of TZP


among the BL/IBL agents regardless of the profiles presented by the isolates. The use of SAM must be questioned (and even replaceable by AMC) due to the high resistance rates observed. Further studies are required to confirm our findings in other nosocomial populations.


acknowledgments


Financial support:No financial support was provided relevant to this article. Potential conflicts of interest: The author reports no conflicts of interest relevant to this article.


Leandro Reus Rodrigues Perez, PhD;1,2 Gabriel Azambuja Narvaez, MD1


Affiliation: 1. Hospital Mãe de Deus, Porto Alegre, Brazil; 2. Universidade


Federal do Rio Grande do Sul, Porto Alegre, Brazil. Address correspondence to Leandro Reus Rodrigues Perez, PhD, Micro-


biology Unit, Hospital Mãe de Deus, 286, José de Alencar Street, 90610-000, Porto Alegre RS, Brazil (leandro.reus@gmail.com). Infect Control Hosp Epidemiol 2017;38:881–883 © 2017 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2017/3807-0022. DOI: 10.1017/ice.2017.93


references


1. Payne DJ, Cramp R, Winstanley DJ, Knowles DJC. Comparative activities of clavulanic acid, sulbactam, and tazobactam against clinically important β-lactamases. Antimicrob Agents Chemother 1994;38:767–772.


2. Perez LR. Is the polymyxin B resistance among multidrug-resistant Enterobacteriaceae (except for the carbapenemase-producing ones) a myth or a matter? Infect Control Hosp Epidemiol 2017;38:126–127.


3. Tamma PD, Han JH, Rock C, et al. Carbapenem therapy is associated with improved survival compared with piperacillin- tazobactam for patients with extended-spectrum β-lactamase bacteremia. Clin Infect Dis 2015;60:1319–1325.


4. Rodrigues Perez LR. Carbapenem-resistant Enterobacteriaceae: a major prevalence difference due to the high performance of carbapenemase producers when compared to the nonproducers. Infect Control Hosp Epidemiol 2015;36:1480–1482.


5. Rodrigues Perez LR, Dias CG. Emergence of infections due to a polymyxin B-resistant KPC-2-producing Klebsiella pneumoniae in critically ill patients: What is the role of a previous coloniza- tion? Infect Control Hosp Epidemiol 2016;37:240–241.


6. Perez LR. Know thy self, know thy enemy: a current survey and a forecast for KPC-producing Klebsiella pneumoniae resistance among inpatients in southern Brazil. Infect Control Hosp Epide- miol 2017;38:754–755.


7. Perez LR. Menacing emergence of fosfomycin resistance among Klebsiella pneumoniae carbapenemase-2-producing K. pneumoniae driven by prior use in critically ill patients. Infect Control Hosp Epidemiol 2016;37:748–749.


8. Solomkin JS, Mazuski JE, Bradley JS, et al. Diagnosis and management of complicated intra-abdominal infection in adults


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