The times they are a-changin': carbapenems for extended-spectrum-β-lactamase-producing bacteria

Carbapenem-sparing strategy: carbapenemase, treatment, and stewardship

PURPOSE OF REVIEW

describing the current role of carbapenems and carbapenem-sparing strategies in the setting of antimicrobial stewardship programs.

RECENT FINDINGS

sparing carbapenems with other drugs appears to be an interesting perspective for a variety of reasons in the current context of the multidrug-resistant (MDR) pandemic. Specific algorithms should also be precisely investigated to define better how to spare carbapenems within empiric and targeted regimens, with combination treatment or monotherapies, aiming at the best use of the new drugs and improving de-escalation as soon as possible for most of the patients.

SUMMARY

stewardship programs may be useful in reducing probable misuse and overuse of antibiotics, which has probably contributed to the emergence of carbapenem-resistant bacteria worldwide. The proposal of carbapenem-sparing strategies has then generated substantial scientific debate and, overall, the concept of sparing these drugs is well advocated together with judicious use of novel drugs, appropriate measures of infection control and prevention as well as in stewardship programs to curb the spread of MDR and XDR-strains in healthcare facilities.

Novel strategies for the management of bacterial and fungal infections in patients with liver cirrhosis: focus on new antimicrobials

Introduction: Liver cirrhosis is a frequent condition caused by different etiologies. Bacterial and fungal infections are common complications, representing an independent prognostic stage in patients with cirrhosis, dramatically worsening their clinical outcomes.Areas covered: The present review article addresses manifold points and to this purpose an inductive literature search of MEDLINE database through PubMed was performed. First, it provides an overview on the mechanisms underlying immune disfunctions in patients with cirrhosis, who are prone to develop infections being at higher risk than the general population. Second, commonest types of bacterial and fungal infections in patients with advanced liver disease are described, focusing on their deleterious impact as decompensating events. Third, the rise of multidrug-resistant (MDR) bacteria and fungi as causative agents of infection in cirrhotic subjects is illustrated. Eventually, the most promising novel therapeutic options against MDR pathogens and fungi are reviewed.Expert opinion: The management of bacterial and fungal infections in patients with cirrhosis is difficult, due to the frequent co-existence of renal impairment, low platelet count and other conditions that limit the antimicrobial choice. New antibacterial and antifungal compounds may overcome this issue by providing a better tolerability profile, along with equal or superior efficacy compared with older drugs.

Comparative Activities of Ceftazidime-Avibactam and Ceftolozane-Tazobactam against Enterobacteriaceae Isolates Producing Extended-Spectrum β-Lactamases from U.S. Hospitals

The activities of ceftazidime-avibactam, ceftolozane-tazobactam, and comparators were evaluated for 733 isolates displaying resistance to broad-spectrum cephalosporins and carrying extended-spectrum β-lactamase (ESBL) genes detected by whole-genome sequencing analysis. Isolates were collected during 2017 in U.S. hospitals. The ESBL producers were 486 Escherichia coli, 190 Klebsiella pneumoniae, and 42 Enterobacter cloacae isolates and isolates from 3 other species. The most common groups of ESBL-encoding genes were bla _CTX-M-15-like (n = 491 isolates) and bla _CTX-M-15 alone (n = 168) or plus bla _OXA-1 (n = 260), followed by bla _CTX-M-14-like (n = 162), which included bla _CTX-M-27 and bla _CTX-M-14 (104 and 51 isolates, respectively), and bla _SHV-12 and bla _SHV-7 (48 and 22 isolates, respectively). ESBL producers carried other β-lactamases, including 1 E. cloacae harboring bla _KPC-3 All ESBL-producing isolates were susceptible to ceftazidime-avibactam, and 90.2/83.9% (CLSI/EUCAST breakpoints) were susceptible to ceftolozane-tazobactam. Tigecycline (98.1/95.8% susceptible) and colistin (99.2%) were comparators that displayed the greatest activity against these isolates. Ceftolozane-tazobactam inhibited 91.4/83.9% of isolates carrying bla _CTX-M-15-like and 97.5/95.1% of isolates carrying bla _CTX-M-14-like, and its activity was more limited against the 91 isolates carrying bla _SHV (66.7/61.1% susceptible). Ceftolozane-tazobactam inhibited 95.5% of the E. coli isolates but only 83.0%, 64.3%, and 80.0% of K. pneumoniae, E. cloacae, and other species harboring ESBL-encoding genes (CLSI breakpoints), respectively. Outer membrane protein sequences for ceftolozane-tazobactam-nonsusceptible isolates did not exhibit significant differences compared to those in genetically related ceftolozane-tazobactam-susceptible isolates. Ceftazidime-avibactam was more active than other agents tested, including ceftolozane-tazobactam, and the activity of this combination was stable regardless of species or ESBL gene carried.

A novel framework to compare the effectiveness of β-lactamase inhibitors against extended-spectrum β-lactamase-producing Enterobacteriaceae

OBJECTIVES

Extended-spectrum β-lactamases (ESBLs) present a serious challenge in the treatment of Gram-negative bacterial infections. ESBLs mediate resistance to most β-lactams, which may be reversed with the addition of an active β-lactamase inhibitor (such as tazobactam, relebactam and avibactam). However, various ESBLs may exhibit different susceptibilities to these inhibitors, which could impact efficacy. We proposed a framework for comparing the efficacy of these inhibitors when combined with the same β-lactam.

METHODS

Three clinical isolates of Klebsiella pneumoniae harbouring CTX-M-15 and one Escherichia coli isolate with SHV-12 were examined. Piperacillin MICs were determined by broth dilution using escalating concentrations of tazobactam, relebactam and avibactam. The resulting MICs were characterized as response to inhibitor concentrations using an inhibitory sigmoid E_max model. Using the best-fit parameter values, the model was conditioned with fluctuating inhibitor concentrations to simulate instantaneous MIC_i profiles for each isolate-inhibitor pair. Using a simulated exposure of 4 g piperacillin every 8 h, %fT > MIC_i was estimated for each piperacillin/inhibitor combination. A hollowfibre infection model was subsequently used to validate the predicted effectiveness of selected combinations.

RESULTS

In all scenarios, piperacillin MIC reductions were well characterized with increasing inhibitor concentrations. As predicted by %fT > MIC_i, combining piperacillin with avibactam (61.4%-73.6%) was found to be superior to tazobactam (13.5%-44.5%) for suppressing bacterial growth over time.

CONCLUSION

We illustrated a practical approach to compare the performance of different inhibitors. This platform may be used clinically to identify the optimal pairing of various β-lactams and β-lactamase inhibitors for individual isolates producing ESBLs.

Prevalence of Aminoglycoside-Modifying Enzymes in Escherichia coli and Klebsiella pneumoniae Producing Extended Spectrum β-Lactamases Collected in Two Multicenter Studies in Spain

The in vitro activity of amikacin, gentamicin, kanamycin, tobramycin, neomycin, and netilmicin against 420 Escherichia coli producing extended spectrum β-lactamases (Ec-ESBLs) and 139 Klebsiella pneumoniae producing extended spectrum β-lactamase (Kp-ESBL) collected in two multicenter studies performed in Spain in 2000 and 2006 was determined. The presence of genes encoding aminoglycoside-modifying enzymes (AMEs) and 16S ribosomal RNA (rRNA) methylases [aac(3)-Ia, aac(3)-IIa, aac(3)-IVa, aac(6')-Ib, ant(2")-Ia, ant(4')-IIa, aph(3')-Ia, aph(3')-IIa, armA, rmtB, and rmtC] was also investigated. The resistance to (one or more) aminoglycosides was significantly higher in Kp-ESBL (104/139, 74.8%) than in Ec-ESBL (171/420, 40.7%; p < 0.0001). The lowest resistance rates for both species in the two studies were observed for amikacin. The prevalence of AME genes was significantly different in Ec-ESBL (161/420, 38.3%) than in Kp-ESBL (115/139, 82.7%; p < 0.0001). The most prevalent AME genes in Ec-ESBL and Kp-ESBL were aac(6')-Ib (16.2% and 44.6%) and aac(3)-IIa (14.7% and 43.1%), respectively. The expected phenotypic profile correlated with the found AMEs encoding genes in 59.6% Ec-ESBL and 26.1% Kp-ESBL. In Ec-ESBL, aac(6')-Ib was usually associated in 2000 with bla_SHV (26.6%), but with bla_CTX-M-1 group (34.8%) in 2006, while aac(3)-IIa was coincident in 2000 with bla_TEM (14.6%) and with bla_CTX-M-1 group (16.3%) in 2006. Among Kp-ESBL, the aac(6')-Ib and aac(3)-IIa genes were more frequent in strains with bla_TEM (22.0% and 44.0%) in 2000 and with bla_CTX-M-1 group (46.4% and 34.0%) in 2006. Resistance to aminoglycosides in Ec-ESBL and Kp-ESBL is frequent and related to production of AMEs; this limits the clinical use of aminoglycosides against these organisms.

Elevated prevalence of multidrug-resistant gram-negative organisms in HIV positive men

BACKGROUND

Routes of transmission of multidrug-resistant gram-negative organisms (MDRGN) are not completely understood. Since sexual transmission of MDRGN might represent a potential mode that has not been noticed so far, this study evaluated transmission of MDRGN in HIV positive men.

METHODS

Between November 2014 and March 2016, we retrospectively investigated the MDRGN prevalence in rectal swabs of n = 109 males tested positive for HIV (HP). These findings were compared to the MDRGN prevalence in n = 109 rectal swabs in age-matched males tested negative for HIV (HN) within the same period. According to the infection control protocol of University Hospital Frankfurt, Germany (UHF), patients admitted to intensive/intermediate care units have to be screened for MDRGN on day of admittance. Patients without HIV testing or MDRGN screening were excluded.

RESULTS

MDRGN prevalence in rectal swabs was significantly higher (p = 0.002) in male HP (23.9%; 95% confidence interval 16.2-32.9%) than in age-matched male HN (8.3%; 3.8-15.1%). In total, 35 MDRGN species were detected. The most frequent MDRGN species was Escherichia coli with resistance due to ESBL expression and additional resistance to fluoroquinolones with n = 25/35 (71.4%; 53.7-85.4%). Thereof, n = 19/26 (73.1%; 52.2-88.4%) were detected in HP and n = 6/9 (66.7%; 29.9-92.5%) in HN, respectively.

CONCLUSIONS

Prevalence of MDRGN is significantly higher in male HIV positive than in male HIV negative individuals. This might indicate sexual transmission of MDRGN within the male HIV positive population. As treatment options in case of MRGN infections are limited, prevention of MDRGN transmission is strongly emphasized.

ESBL Detection: Comparison of a Commercially Available Chromogenic Test for Third Generation Cephalosporine Resistance and Automated Susceptibility Testing in Enterobactericeae

Rapid detection and reporting of third generation cephalosporine resistance (3GC-R) and of extended spectrum betalactamases in Enterobacteriaceae (ESBL-E) is a diagnostic and therapeutic priority to avoid inefficacy of the initial antibiotic regimen. In this study we evaluated a commercially available chromogenic screen for 3GC-R as a predictive and/or confirmatory test for ESBL and AmpC activity in clinical and veterinary Enterobacteriaceae isolates. The test was highly reliable in the prediction of cefotaxime and cefpodoxime resistance, but there was no correlation with ceftazidime and piperacillin/tazobactam minimal inhibitory concentrations. All human and porcine ESBL-E tested were detected with exception of one genetically positive but phenotypically negative isolate. By contrast, AmpC detection rates lay below 30%. Notably, exclusion of piperacillin/tazobactam resistant, 3GC susceptible K1+ Klebsiella isolates increased the sensitivity and specificity of the test for ESBL detection. Our data further imply that in regions with low prevalence of AmpC and K1 positive E. coli strains chromogenic testing for 3GC-R can substitute for more time consuming ESBL confirmative testing in E. coli isolates tested positive by Phoenix or VITEK2 ESBL screen. We, therefore, suggest a diagnostic algorithm that distinguishes 3GC-R screening from primary culture and species-dependent confirmatory ESBL testing by βLACTATM and discuss the implications of MIC distribution results on the choice of antibiotic regimen.