Point-Counterpoint: Piperacillin-Tazobactam Should Be Used To Treat Infections with Extended-Spectrum-Beta-Lactamase-Positive Organisms

A review of the mechanisms that confer antibiotic resistance in pathotypes of E. coli

The dissemination of antibiotic resistance in Escherichia coli poses a significant threat to public health worldwide. This review provides a comprehensive update on the diverse mechanisms employed by E. coli in developing resistance to antibiotics. We primarily focus on pathotypes of E. coli (e.g., uropathogenic E. coli) and investigate the genetic determinants and molecular pathways that confer resistance, shedding light on both well-characterized and recently discovered mechanisms. The most prevalent mechanism continues to be the acquisition of resistance genes through horizontal gene transfer, facilitated by mobile genetic elements such as plasmids and transposons. We discuss the role of extended-spectrum β-lactamases (ESBLs) and carbapenemases in conferring resistance to β-lactam antibiotics, which remain vital in clinical practice. The review covers the key resistant mechanisms, including: 1) Efflux pumps and porin mutations that mediate resistance to a broad spectrum of antibiotics, including fluoroquinolones and aminoglycosides; 2) adaptive strategies employed by E. coli, including biofilm formation, persister cell formation, and the activation of stress response systems, to withstand antibiotic pressure; and 3) the role of regulatory systems in coordinating resistance mechanisms, providing insights into potential targets for therapeutic interventions. Understanding the intricate network of antibiotic resistance mechanisms in E. coli is crucial for the development of effective strategies to combat this growing public health crisis. By clarifying these mechanisms, we aim to pave the way for the design of innovative therapeutic approaches and the implementation of prudent antibiotic stewardship practices to preserve the efficacy of current antibiotics and ensure a sustainable future for healthcare.

[Potential Nephrotoxicity of Combination of Vancomycin and Piperacillin-Tazobactam: Recommendations from the AG ABS of the DGPI supported by experts of the GPN]

The combination of vancomycin and piperacillin/tazobactam (V+P/T) is used for empirical antibiotic treatment of severe infections, especially in immunocompromised patients and those colonized with multidrug-resistant bacteria. Nephrotoxicity is a frequently observed adverse effect of vancomycin. Its risk can be reduced by therapeutic drug monitoring and adjusted dosing. Piperacillin/tazobactam (P/T) rarely causes interstitial nephritis. The results of retrospective cohort studies in children predominantly show a low, clinically irrelevant, additive nephrotoxicity (defined as an increase in creatinine in the serum) of both substances. Due to the limitations of the existing publications, the ABS working group of the DGPI and experts of the GPN do not recommend against the use of P/T plus vancomycin. Preclinical studies and a prospective study with adult patients, which evaluated different renal function tests as well as clinical outcomes, do not support previous findings of additive nephrotoxicity. Time-restricted use of V+P/T can minimize exposure and the potential risk of nephrotoxicity. Local guidelines, developed in collaboration with the antibiotic stewardship team, should define the indications for empirical and targeted use of P/T and V+P/T. When using combination therapy with V+P/T, kidney function should be monitored through clinical parameters (volume status, balancing, blood pressure) as well as additional laboratory tests such as serum creatinine and cystatin C.

In vitro and in vivo evaluation of two combined β-lactamase inhibitors against carbapenem-resistant Acinetobacter baumannii

The objective of this study was to evaluate the in vitro and in vivo efficacy of clavulanic acid (C/A) in combination with tazobactam against clinical strains of carbapenem-resistant Acinetobacter baumannii. The MIC of 24 clinical strains of A. baumannii was determined, and a checkerboard assay and time-kill curve analysis were performed in selected strains to determine the synergy between C/A and tazobactam. The efficacy of C/A in monotherapy and in combination with tazobactam was evaluated in vitro in cell culture experiments and in a murine peritoneal sepsis model. The C/A and C/A plus tazobactam MIC50 were 128 and <1 mg/L, respectively. The checkerboard assay showed that tazobactam (4 and 8 mg/L) demonstrated synergy with C/A against A. baumannii Ab40, an OXA-24 producer strain, and Ab293, a lacking OXA β-lactamase strain. The time-kill curve assay showed both bactericidal and synergistic effects against Ab40 and Ab293, with C/A 1xMIC and tazobactam (4 and 8 mg/L) at 24 h. In the murine peritoneal sepsis model with Ab293 strain, the combination of C/A and tazobactam reduced bacterial loads in tissues and blood by 2 and 4 log10 CFU/g or mL compared with C/A alone. Combining C/A with tazobactam could be considered as a potential alternative strategy to treat A. baumannii in some cases, and future work with more strains is needed to confirm this possibility.

The effect of meropenem versus piperacillin-tazobactam in critically ill patients with sepsis and septic shock

Background

Antibiotics are a popular and efficient treatment for sepsis and septic shock. However, there is presently little proof of Meropenem with piperacillin-therapeutic tazobactam's benefits.

Methods

From January 1, 2010 to January 1, 2021, we treated a total of 1244 patients with sepsis and septic shock using either Meropenem (n = 622, 1 g every 8 h) or piperacillin-tazobactam (n = 622, 3.375 g or 4.5 g every 8 h). The intervention was administered for 7 days following randomization and continued for up to 14 days thereafter, or until the patient was discharged from the critical care unit or passed away, whichever occurred first.

Results

First, we discovered that there were no significant changes in the duration of stay in ICU, Cardiovascular in SOFA, Coagulation in SOFA, Hepatic in SOFA, or Central Nervous System in SOFA between the meropenem alone group and the piperacillin-tazobactam group. In addition, WBC beyond the standard limit was 68.00% in the meropenem alone group against 61.89% in the piperacillin-tazobactam group (P = 0.03). However, Meropenem had a lower mortality rate on ventilator-free days, vasopressor-free days, and hospital-free days.

Conclusion

This procedure may offer clinical evidence for the safety and efficacy of meropenem with piperacillin-tazobactam in critically sick patients with sepsis and septic shock.

Efficacy of carbapenem vs non carbapenem β-lactam therapy as empiric antimicrobial therapy in patients with extended-spectrum β-lactamase-producing Enterobacterales urinary septic shock: a propensity-weighted multicenter cohort study

BACKGROUND

The rise in antimicrobial resistance is a global threat responsible for about 33,000 deaths in 2015 with a particular concern for extended-spectrum beta-lactamase-producing Enterobacterales (ESBL-E) and has led to a major increase in the use of carbapenems, last-resort antibiotics.

METHODS

In this retrospective propensity-weighted multicenter observational study conducted in 11 ICUs, the purpose was to assess the efficacy of non carbapenem regimen (piperacillin-tazobactam (PTZ) + aminoglycosides or 3rd-generation cephalosporin (3GC) + aminoglycosides) as empiric therapy in comparison with carbapenem in extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E) urinary septic shock. The primary outcome was Day-30 mortality.

RESULTS

Among 156 patients included in this study, 69 received a carbapenem and 87 received non carbapenem antibiotics as empiric treatment. Baseline clinical characteristics were similar between the two groups. Patients who received carbapenem had similar Day-30 mortality (10/69 (15%) vs 6/87 (7%), OR = 1.99 [0.55; 5.34] p = 0.16), illness severity, resolution of septic shock, and ESBL-E infection recurrence rates than patients who received an empiric non carbapenem therapy. The rates of secondary infection with C. difficile were comparable.

CONCLUSIONS

In ESBL-E urinary septic shock, empiric treatment with a non carbapenem regimen, including systematically aminoglycosides, was not associated with higher mortality, compared to a carbapenem regimen.

Rapid Detection of Piperacillin-Tazobactam Resistance in Klebsiella pneumoniae and Escherichia coli

Rapid determination of susceptibility to piperacillin-tazobactam (TZP) is very important since the development of antibiotic resistance and inadequate treatment could increase the risk of clinical failure in infected patients, especially if such resistance is unknown to the clinician. Therefore, based on color change from orange to yellow of phenol red due to glucose metabolism (bacterial growth) in the presence of an adequate concentration of TZP (10 mg/L piperacillin and 5 mg/L tazobactam), the RapidTZP test has been developed to detect TZP resistance in Escherichia coli and Klebsiella pneumoniae isolates in a maximum of 3 h. A total of 140 isolates, 43 of E. coli and 97 of K. pneumoniae, were used to evaluate the performance of the test, 60 being resistant to TZP. The sensitivity and specificity of the test were 98.24% and 100%, respectively. Additionally, the RapidTZP test was validated by a pellet obtained directly from blood culture bottles. A total of 37 positive blood cultures for E. coli and 43 for K. pneumoniae were used for validation, 8 of them resistant to TZP. The sensitivity and specificity shown in the evaluation were 100% for both parameters. This new test is easy, fast, and accurate, providing results in 3 h. IMPORTANCE TZP is an antibiotic widely used for the empirical treatment of severe infections such as bloodstream infections. However, resistance to TZP in K. pneumoniae and E. coli has been increasing in the last few years. Thus, rapid detection of TZP resistance is critical to optimize the empirical treatment of patients with severe infections. In this study, we developed and evaluated a rapid test (RapidTZP) for the detection of TZP resistance in K. pneumoniae and E. coli directly from positive hemocultures in just 3 h. This rapid test has been validated on 138 K. pneumoniae and E. coli clinical isolates directly from agar plates and 80 K. pneumoniae and E. coli isolates causing bloodstream infections. The results demonstrate that the RapidTZP test has great clinical potential to optimize the empirical treatment of patients with bloodstream infections.

Best practices: Appropriate use of the new β-lactam/β-lactamase inhibitor combinations, ceftazidime-avibactam and ceftolozane-tazobactam in South Africa

Antibiotic stewardship of hospital-acquired infections because of difficult-to-treat resistant (DTR) Gram-negative bacteria is a global challenge. Their increasing prevalence in South Africa has required a shift in prescribing in recent years towards colistin, an antibiotic of last resort. High toxicity levels and developing resistance to colistin are narrowing treatment options further. Recently, two new β-lactam/β-lactamase inhibitor combinations, ceftazidime-avibactam and ceftolozane-tazobactam were registered in South Africa, bringing hope of new options for management of these life-threatening infections. However, with increased use in the private sector, increasing levels of resistance to ceftazidime-avibactam are already being witnessed, putting their long-term viability as treatment options of last resort, in jeopardy. This review focuses on how these two vital new antibiotics should be stewarded within a framework that recognises the resistance mechanisms currently predominant in South Africa's multi-drug and DTR Gram-negative bacteria. Moreover, the withholding of their use for resistant infections that can be treated with currently available antibiotics is a critical part of stewardship, if these antibiotics are to be conserved in the long term.

Pragmatic Comparison of Piperacillin/Tazobactam versus Carbapenems in Treating Patients with Nosocomial Pneumonia Caused by Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae

The effectiveness of piperacillin/tazobactam for managing nosocomial pneumonia caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae is unknown. To answer this question, we conducted a retrospective cohort study in two tertiary teaching hospitals of patients admitted between January 2018 and July 2021 with a diagnosis of nosocomial pneumonia caused by ESBL-producing K. pneumoniae receiving either piperacillin/tazobactam or carbapenems within 24 h from the onset of pneumonia for at least 72 h. Clinical outcomes, including 28-day mortality and 14-day clinical and microbiological cure, were analyzed. Of the 136 total patients, 64 received piperacillin/tazobactam and 72 received carbapenems. The overall 28-day mortality was 19.1% (26/136). In the inverse probability of treatment weighted cohort, piperacillin/tazobactam therapy was not associated with worse clinical outcomes, as the 28-day mortality (OR, 0.82, 95% CI, 0.23–2.87, p = 0.748), clinical cure (OR, 0.94, 95% CI, 0.38–2.35, p = 0.894), and microbiological cure (OR, 1.10, 95% CI, 0.53–2.30, p = 0.798) were comparable to those of carbapenems. Subgroup analyses also did not demonstrate any statistical differences. In conclusion, piperacillin/tazobactam could be an effective alternative to carbapenems for treating nosocomial pneumonia due to ESBL-producing K. pneumoniae when the MICs are ≤8 mg/L.

Treatment and Epidemiology of Third-Generation Cephalosporin-Resistant Urinary Tract Infections

BACKGROUND AND OBJECTIVES

Limited data are available on the contemporary epidemiology, clinical management, and health care utilization for pediatric urinary tract infection (UTI) due to third-generation cephalosporin-resistant Enterobacterales (G3CR) in the United States. The objective is to describe the epidemiology, antimicrobial treatment and response, and health care utilization associated with G3CR UTI.

METHODS

Multisite, matched cohort-control study including children with G3CR UTI versus non-G3CR UTI. UTI was defined as per American Academy of Pediatrics guidelines, and G3CR as resistance to ceftriaxone, cefotaxime, or ceftazidime. We collected data from the acute phase of illness to 6 months thereafter.

RESULTS

Among 107 children with G3CR UTI and 206 non-G3CR UTI with documented assessment of response, the proportion with significant improvement on initial therapy was similar (52% vs 57%; odds ratio [OR], 0.81; 95% confidence interval [CI], 0.44-1.50). Patients with G3CR were more frequently hospitalized at presentation (38% vs 17%; OR, 3.03; 95% CI, 1.77-5.19). In the follow-up period, more patients with G3CR had urine cultures (75% vs 53%; OR, 2.61; 95% CI, 1.33-5.24), antimicrobial treatment of any indication (53% vs 29%; OR, 2.82; 95% CI, 1.47-5.39), and subspecialty consultation (23% vs 6%; OR, 4.52; 95% CI, 2.10-10.09). In multivariate analysis, previous systemic antimicrobial therapy remained a significant risk factor for G3CR UTI (adjusted OR, 1.91; 95% CI, 1.06-3.44).

CONCLUSIONS

We did not observe a significant difference in response to therapy between G3CR and susceptible UTI, but subsequent health care utilization was significantly increased.

Do weekly surveillance cultures contribute to antibiotic stewardship and correlate with outcome of HSCT in children - a multicentre real-world experience of 5 years from Indian subcontinent?

BACKGROUND

The utility of weekly rectal swab surveillance cultures (RSSC) as a resource to identify gut colonisation with Extended Spectrum Beta-Lactamase (ESBL)-producing E Coli or Klebsiella pneumoniae carbapenemase (KPC) producing organisms, to guide empirical antibiotic therapy in HSCT patients continues to be a subject of interest. There is urgency to assess and justify modifications to empirical antibiotics based upon regional epidemiology and patient groups.

OBJECTIVE

To study the utility of weekly rectal swab surveillance cultures (RSSC) to guide empirical antibiotics therapy and the impact of gut colonisation on transplant outcomes.

STUDY DESIGN

This is a retrospective analysis of 317 successive first transplants done in three pediatric bone marrow transplant centres in Indian sub-continent, mainly for hemoglobinopathies, between April 2016 and April 2021. Transplantation, infection control and febrile neutropenia management protocols are identical among the three centres. First line antibiotics were chosen based on RCCS reports i.e. meropenem and high dose meropenem with colistin for ESBL and carbapenemase resistant colonisation respectively for first half of the study and no adjustment was made in the second half. Clinical response to antibiotics, long term outcomes, antibiotic-resistant bacteraemia and acute GVHD were analysed. Log-rank test, Chi-squared test and Wilcoxon test were used to compare data using R Statistical software.

RESULTS

Of all 871 weekly RSSC done, 162 were positive for ESBL- or KPC-resistant organism. RCCS were ESBL-positive in 106 patients (33%) and KPC-positive in 10 patients (3%). Within 97 ESBL-positive patients for whom antimicrobial susceptibility testing (AST) report was available, only 22 (25%) demonstrated clinical resistance of Pip-Taz. Within the 10 KPC-positive patients' clinical resistance was observed only in 4 (40%) to Pip-Taz and 3 (30%) to meropenem. For ESBL-positive RSSC where 1st line empirical antibiotics were used, 66% of the patients responded clinically. Even within the 15 who were resistant to 1st line empirical antibiotics (Pip-Taz) on RSSC reports, 67% responded to Pip-Taz clinically. Within these patients 27 (56%) never needed any carbapenems. Using Pip-Taz empirically in ESBL-positive patients did not prolong meropenem use within 100 days of transplantation (p=0.18). For KPC-positive RSSC where 1st line empirical antibiotics were used, all patients clinically responded, including 4 who were resistant to Pip-Taz and 3 patients who were meropenem resistant on RCCS. Comparing patients who were ESBL-positive, KPC-positive and neither, no statistically significant difference was seen in overall survival (p=0.95), disease free survival (p=0.45), transplant related mortality (p=0.97), rejection (p=0.68) and rate of acute GVHD grade II-IV (p=0.78). Comparing the ESBL-positive patients who did and did not get higher-level empirical antibiotics, no statistical difference was seen in overall survival (p=0.32), disease free survival (p=0.64), transplant related mortality (p=0.65), rejection (p=0.46), acute GVHD grade II-IV (p=0.26) or antibiotic resistant bacteraemia (p=0.3).

CONCLUSIONS

In context of transplantation for non-malignant HSCTs, empiric antibiotic choice based on rectal swab surveillance cultures is not justified, even in regions with a high prevalence of antimicrobial resistance. Antimicrobial susceptibility testing (AST) reports in surveillance cultures did not correlate with in-vivo clinical response. Colonisation reported on weekly surveillance rectal swab cultures showed no correlation with clinical outcomes.

Cefoperazone sodium/sulbactam sodium vs piperacillin sodium/tazobactam sodium for treatment of respiratory tract infection in elderly patients

BACKGROUND

Respiratory tract infections in the elderly are difficult to cure and can easily recur, thereby posing a great threat to patient prognosis and quality of life.

AIM

To investigate the therapeutic effects of different antibiotics in elderly patients with respiratory tract infection.

METHODS

Seventy-four elderly patients with respiratory tract infection were randomly allocated to a study (n = 37; treated with cefoperazone sodium/sulbactam sodium) or control (n = 37; treated with piperacillin sodium/tazobactam sodium on the basis of routine symptomatic support) group. Both groups were treated for 7 d. Time to symptom relief (leukocyte recovery; body temperature recovery; cough and sputum disappearance; and rale disappearance time), treatment effect, and laboratory indexes [procalcitonin (PCT), C-reactive protein (CRP), white blood cell count (WBC), and neutrophil percentage (NE)] before and 7 d after treatment and the incidence of adverse reactions were assessed.

RESULTS

In the study group, the time to WBC normalization (6.79 ± 2.09 d), time to body temperature normalization (4.15 ± 1.08 d), time to disappearance of cough and sputum (6.19 ± 1.56 d), and time to disappearance of rales (6.68 ± 1.43 d) were shorter than those of the control group (8.89 ± 2.32 d, 5.81 ± 1.33 d, 8.77 ± 2.11 d, and 8.69 ± 2.12 d, respectively; P = 0.000). Total effective rate was higher in the study group (94.59% vs 75.68%, P = 0.022). Serum PCT (12.89 ± 3.96 μg/L), CRP (19.62 ± 6.44 mg/L), WBC (20.61 ± 6.38 × 10⁹/L), and NE (86.14 ± 7.21%) levels of the study group before treatment were similar to those of the control group (14.05 ± 4.11 μg/L, 18.79 ± 5.96 mg/L, 21.21 ± 5.59 × 10⁹/L, and 84.39 ± 6.95%, respectively) with no significant differences (P = 0.220, 0.567, 0.668, and 0.291, respectively). After 7 d of treatment, serum PCT, CRP, WBC, and NE levels in the two groups were lower than those before treatment. Serum PCT (2.01 ± 0.56 μg/L), CRP (3.11 ± 1.02 mg/L), WBC (5.10 ± 1.83 × 10⁹/L), and NE (56.35 ± 7.17%) levels were lower in the study group than in the control group (3.29 ± 0.64 μg/L, 5.67 ± 1.23 mg/L, 8.13 ± 3.01 × 10⁹/L, and 64.22 ± 8.08%, respectively; P = 0.000). There was no significant difference in the incidence of adverse reactions between the groups (7.50% vs 12.50%, P = 0.708).

CONCLUSION

Piperacillin sodium/tazobactam sodium is superior to cefoperazone sodium/ sulbactam sodium in the treatment of elderly patients with respiratory tract infection with a similar safety profile.

Healthcare-associated urinary tract infections in urology

The purpose of the present review is to report the incidence and characteristics of healthcare-associated urinary tract infections (HAUTIs) in urology with their microbiological and resistance patterns. Urinary tract infections are the main type of healthcare-associated infection in patients hospitalized in a urology ward. Patients admitted to urology departments report a high prevalence of urinary tract catheterization, up to 75% during the hospitalization period, and up to 20% had a urinary catheter before admission. An endourological surgical procedure is another risk factor for HAUTIs. Other risk factors for HAUTIs are the presence of immunosuppression and previous urinary tract infections.

In urological patients, Enterobacterales are the principal causative agent of HAUTIs, and E. coli is the most frequently isolated microorganism. However, there is also a high rate of microorganisms other than E. coli such as Klebsiella spp. and Enterococcus spp. Non-E. coli microorganisms show a higher prevalence in immunosuppressed patients and those with urinary catheters before admission. High resistance patterns are reported in patients with HAUTIs, and ESBL-producing bacteria are frequently described. Moreover, the isolation of multidrug-resistant microorganisms is more common in immunosuppressed patients, those with previous urinary tract infections, and urinary catheters into the upper urinary tract. Treatment must be tailored according to patient characteristics and patient profiles, bearing in mind the ORENUC classification for risk factors (no risk factors (O), recurrent urinary tract infections risk factors (R), extraurogenital risk factors (E), nephropathic disease (N), urological risk factors (U), permanent urinary catheter and non-resolvable urological risk factors (C)).

Comparison of therapy with β-lactam/β-lactamase inhibitor combinations or carbapenems for bacteraemia of nonurinary source caused by ESBL-producing Escherichia coli or Klebsiella pneumoniae

Background

Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae has become a public health concern. This study aimed to compare the clinical outcomes of patients with nonurinary source bacteraemia caused by ESBL-producing Escherichia coli (E. coli) or Klebsiella pneumoniae (ESBL-producing EK) receiving β-lactam/β-lactamase inhibitor combinations (BLICs) versus carbapenem treatment and assess the risk factors of mortality with these two drugs.

Methods

We conducted a retrospective single-centre study of adult hospitalised patients with ESBL-producing EK bloodstream infection (BSI) from nonurinary source at our centre over a 4-year period. One hundred and eighty patients who received BLICs or carbapenems were included in the analysis. The outcome variables were 14-day treatment failure and 30-day mortality. For more reliable results, propensity score analysis was performed to compare the efficacy of the two drugs and analyse their risk factors for 30-day mortality.

Results

Out of 180 patients, 114 received BLICs, and 66 received carbapenem therapy. Compared to carbapenem-treated patients, those treated with BLICs were older and had higher age-adjusted Charlson comorbidity index, but they had shorter stay in the hospital. Additionally, their Pitt bacteraemia score, SOFA score, rate of leukaemia, and immune compromise were lower. After propensity score matching (PSM), the baseline characteristics of patients in the two treatment groups were balanced. BLICs were associated with a higher 14-day treatment failure rate (20.6%, 13/63) than carbapenems (16.3%, 7/43), although the difference was not significant in either univariate analysis (P = 0.429) or multivariate analysis (P = 0.122). And the 30-day mortality rate in BTG (11.1%, 7/63) and CTG (11.6%, 5/43) did not significantly differ (univariate analysis, P = 0.926; multivariate analysis, P = 0.420). In the multivariate analysis, after PSM, leukaemia was the only independent predictor of mortality in both BTG and CTG.

Conclusions

Our study showed that BLICs had higher 14-day treatment failure rate compared with carbapenems, although there were no statistically significant differences because of the small number of patients, therefore, further evaluation of the efficacy of BLICs is needed.

OXA-1 β-lactamase and non-susceptibility to penicillin/β-lactamase inhibitor combinations among ESBL-producing Escherichia coli

Background

ESBL-producing Escherichia coli have expanded globally since the turn of the century and present a major public health issue. Their in vitro susceptibility to penicillin/inhibitor combinations is variable, and clinical use of these combinations against ESBL producers remains controversial. We hypothesized that this variability related to co-production of OXA-1 penicillinase.

Methods

During a national study we collected 293 ESBL-producing E. coli from bacteraemias, determined MICs by BSAC agar dilution, and undertook genomic sequencing with Illumina methodology.

Results

The collection was dominated by ST131 (n = 188 isolates, 64.2%) and blaCTX-M-15 (present in 229 isolates, 78.2%); over half the isolates (159/293, 54.3%) were ST131 with blaCTX-M-15. blaOXA-1 was found in 149 ESBL producers (50.9%) and blaTEM-1/191 in 137 (46.8%). Irrespective of whether all isolates were considered, or ST131 alone, there were strong associations (P < 0.001) between co-carriage of blaOXA-1 and reduced susceptibility to penicillin/inhibitor combinations, whereas there was no significant association with co-carriage of blaTEM-1/191. For piperacillin/tazobactam the modal MIC rose from 2 mg/L in the absence of blaOXA-1 to 8 or 16 mg/L in its presence; for co-amoxiclav the shift was smaller, from 4 or 8 to 16 mg/L, but crossed the breakpoint. blaOXA-1 was strongly associated with co-carriage also of aac(6')-Ib-cr, which compromises amikacin and tobramycin.

Conclusions

Co-carriage of OXA-1, a penicillinase with weak affinity for inhibitors, is a major correlate of resistance to piperacillin/tazobactam and co-amoxiclav in E. coli and is commonly associated with co-carriage of aac(6')-Ib-cr, which narrows aminoglycoside options.

High Heterogeneity of Multidrug-Resistant Enterobacteriaceae Fecal Levels in Hospitalized Patients Is Partially Driven by Intravenous β-Lactams

Multidrug-resistant Enterobacteriaceae (MRE) colonize the intestine asymptomatically from where they can breach into the bloodstream and cause life-threatening infections, especially in heavily colonized patients. Despite the clinical relevance of MRE colonization levels, we know little about how they vary in hospitalized patients and the clinical factors that determine those levels. Here, we conducted one of the largest studies of MRE fecal levels by tracking longitudinally 133 acute leukemia patients and monitoring their MRE levels over time through extensive culturing. MRE were defined as Enterobacteriaceae species that acquired nonsusceptibility to ≥1 agent in ≥3 antimicrobial categories. In addition, due to the selective media used, the MRE had to be resistant to third-generation cephalosporins. MRE were detected in 60% of the patients, but their fecal levels varied considerably among patients and within the same patient (>6 and 4 orders of magnitude, respectively). Multivariate analysis of clinical metadata revealed an impact of intravenous beta-lactams (i.e., meropenem and piperacillin-tazobactam), which significantly diminished the fecal MRE levels in hospitalized patients. Consistent with a direct action of beta-lactams, we found an effect only when the patient was colonized with strains sensitive to the administered beta-lactam (P < 0.001) but not with nonsusceptible strains. We report previously unobserved inter- and intraindividual heterogeneity in MRE fecal levels, suggesting that quantitative surveillance is more informative than qualitative surveillance of hospitalized patients. In addition, our study highlights the relevance of incorporating antibiotic treatment and susceptibility data of gut-colonizing pathogens for future clinical studies and in clinical decision-making.

Clinical cure rate and cost-effectiveness of carbapenem-sparing beta-lactams vs. meropenem for Gram-negative infections: A systematic review, meta-analysis, and cost-effectiveness analysis

The increasing incidence of infections caused by extended-spectrum beta-lactamase (ESBL)/AmpC-producing bacteria leads to increasing use of carbapenems and risk of carbapenem resistance. Treatment success of carbapenem-sparing beta-lactams (CSBs) for ESBL infections is unclear. The aim of this study was to appraise the clinical cure rate and estimate the cost-effectiveness of meropenem vs. CSBs (piperacillin-tazobactam, temocillin, ceftazidime-avibactam, and ceftolozane-tazobactam) for urinary tract infections (UTIs) or intra-abdominal infections (IAIs) due to ESBL/AmpC-producing bacteria. A systematic literature search of the Cochrane library, EMBASE, PubMed, and Web of Science was conducted to identify studies assessing the clinical cure rate of the antibiotics. To assess the cost-effectiveness of CSBs vs. meropenem, a combined decision analytic and Markov model was probabilistically analysed over a 5-year period. The main outcome was presented as the incremental cost-effectiveness ratio and evaluated with a threshold of €20 000 per life year gained (LYG). From 656 identified articles, 17 and 14 studies were included in the qualitative synthesis and quantitative synthesis, respectively. A clinical cure of ceftazidime-avibactam and ceftolozane-tazobactam was comparable to meropenem in patients with complicated IAIs (cIAIs) due to ESBL (Risk ratio [RR]=1·04, 95% confidence interval [CI]=0·95-1·13). Both temocillin and ceftolozane-tazobactam were deemed cost-effective compared to meropenem with €157·58 and €13 398·34 per LYG, respectively, in patients with UTIs due to ESBL. However, only ceftazidime-avibactam (plus metronidazole) was cost-effective for the treatment of IAIs, with €16 916·77 per LYG. These results show that several CSBs can be considered as viable candidates for the treatment of UTIs and IAIs caused by ESBL.

Newer β-Lactam/β-Lactamase inhibitor for multidrug-resistant gram-negative infections: Challenges, implications and surveillance strategy for India

Antimicrobial resistance (AMR) is a major public health concern across the globe, and it is increasing at an alarming rate. Multiple classes of antimicrobials have been used for the treatment of infectious diseases. Rise in the AMR limits its use and hence the prerequisite for the newer agents to combat drug resistance. Among the infections caused by Gram-negative organisms, beta-lactams are one of the most commonly used agents. However, the presence of diverse beta-lactamases hinders its use for therapy. To overcome these enzymes, beta-lactamase inhibitors are being discovered. The aim of this document is to address the burden of AMR in India and interventions to fight against this battle. This document addresses and summarises the following: The current scenario of AMR in India (antimicrobial susceptibility, resistance mechanisms and molecular epidemiology of common pathogens); contentious issues in the use of beta-lactam/beta-lactamase inhibitor as an carbapenem sparing agent; role of newer beta-lactam/beta-lactamase inhibitor agents with its appropriateness to Indian scenario and; the Indian Council of Medical Research interventions to combat drug resistance in terms of surveillance and infection control as a national response to AMR. This document evidences the need for improved national surveillance system and country-specific newer agents to fight against the AMR.

Resistance mechanisms and population structure of highly drug resistant Klebsiella in Pakistan during the introduction of the carbapenemase NDM-1

Klebsiella pneumoniae is a major threat to public health with the emergence of isolates resistant to most, if not all, useful antibiotics. We present an in-depth analysis of 178 extended-spectrum beta-lactamase (ESBL)-producing K. pneumoniae collected from patients resident in a region of Pakistan, during the period 2010–2012, when the now globally-distributed carbapenemase bla-NDM-1 was being acquired by Klebsiella. We observed two dominant lineages, but neither the overall resistance profile nor virulence-associated factors, explain their evolutionary success. Phenotypic analysis of resistance shows few differences between the acquisition of resistance genes and the phenotypic resistance profile, including beta-lactam antibiotics that were used to treat ESBL-positive strains. Resistance against these drugs could be explained by inhibitor-resistant beta-lactamase enzymes, carbapenemases or ampC type beta-lactamases, at least one of which was detected in most, but not all relevant strains analysed. Complete genomes for six selected strains are reported, these provide detailed insights into the mobile elements present in these isolates during the initial spread of NDM-1. The unexplained success of some lineages within this pool of highly resistant strains, and the discontinuity between phenotypic resistance and genotype at the macro level, indicate that intrinsic mechanisms contribute to competitive advantage and/or resistance.