The antimicrobial activity of mecillinam, nitrofurantoin, temocillin and fosfomycin and comparative analysis of resistance patterns in a nationwide collection of ESBL-producing Escherichia coli in Norway 2010-2011

Review of the In Vitro Microbiological Activity of Mecillinam Against Common Uropathogens in Uncomplicated Urinary Tract Infection: Focus on Resistant Pathogens

Antimicrobial resistance in uropathogens commonly causing urinary tract infections (UTIs) is a growing problem internationally. Pivmecillinam, the oral prodrug of mecillinam, has been used for over 40 years, primarily in Northern Europe and Canada. It is recommended in several countries as a first-line agent for the treatment of uncomplicated UTIs (uUTIs) and is now approved in the United States. We performed a structured literature search to review the available evidence on susceptibility of common uUTI-causing uropathogens to mecillinam. Among 38 studies included in this literature review, susceptibility rates for Escherichia coli to mecillinam-including resistant phenotypes such as extended-spectrum β-lactamase-producing E. coli-exceed 90% in most studies. High rates of susceptibility were also reported among many other uropathogens including Klebsiella spp., Enterobacter spp., and Citrobacter spp. In the current prescribing climate within the United States, pivmecillinam represents a viable first-line treatment option for patients with uUTI.

Antibiotic resistance monitoring in wastewater in the Nordic countries: A systematic review

The Nordic countries (Denmark, Finland, Iceland, Norway, and Sweden) have effectively kept lower antibiotic-resistant bacterial (ARB) pathogen rates than many other countries. However, in recent years, these five countries have encountered a rise in ARB cases and challenges in treating infections due to the growing prevalence of ARB pathogens. Wastewater-based surveillance (WBS) is a valuable supplement to clinical methods for ARB surveillance, but there is a lack of comprehensive understanding of WBS application for ARB in the Nordic countries. This review aims to compile the latest state-of-the-art developments in WBS for ARB monitoring in the Nordic countries and compare them with clinical surveillance practices. After reviewing 1480 papers from the primary search, 54 were found relevant, and 15 additional WBS-related papers were included. Among 69 studies analyzed, 42 dedicated clinical epidemiology, while 27 focused on wastewater monitoring. The PRISMA review of the literature revealed that Nordic countries focus on four major WBS objectives of ARB: assessing ARB in the human population, identifying ARB evading wastewater treatment, quantifying removal rates, and evaluating potential ARB evolution during the treatment process. In both clinical and wastewater contexts, the most studied targets were pathogens producing carbapenemase and extended-spectrum beta-lactamase (ESBL), primarily Escherichia coli and Klebsiella spp. However, vancomycin-resistant Enterococcus (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) have received more attention in clinical epidemiology than in wastewater studies, probably due to their lower detection rates in wastewater. Clinical surveillance has mostly used culturing, antibiotic susceptibility testing, and genotyping, but WBS employed PCR-based and metagenomics alongside culture-based techniques. Imported cases resulting from international travel and hospitalization abroad appear to have frequently contributed to the rise in ARB pathogen cases in these countries. The many similarities between the Nordic countries (e.g., knowledge exchange practices, antibiotic usage patterns, and the current ARB landscape) could facilitate collaborative efforts in developing and implementing WBS for ARB in population-level screening.

Assessing Clinical Potential of Old Antibiotics against Severe Infections by Multi-Drug-Resistant Gram-Negative Bacteria Using In Silico Modelling

In the light of increasing antimicrobial resistance among gram-negative bacteria and the lack of new more potent antimicrobial agents, new strategies have been explored. Old antibiotics, such as colistin, temocillin, fosfomycin, mecillinam, nitrofurantoin, minocycline, and chloramphenicol, have attracted the attention since they often exhibit in vitro activity against multi-drug-resistant (MDR) gram-negative bacteria, such as Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. The current review provides a summary of the in vitro activity, pharmacokinetics and PK/PD characteristics of old antibiotics. In silico modelling was then performed using Monte Carlo simulation in order to combine all preclinical data with human pharmacokinetics and determine the probability of target (1-log kill in thigh/lung infection animal models) attainment (PTA) of different dosing regimens. The potential of clinical efficacy of a drug against severe infections by MDR gram-negative bacteria was considered when PTA was >95% at the epidemiological cutoff values of corresponding species. In vitro potent activity against MDR gram-negative pathogens has been shown for colistin, polymyxin B, temocillin (against E. coli and K. pneumoniae), fosfomycin (against E. coli), mecillinam (against E. coli), minocycline (against E. coli, K. pneumoniae, A. baumannii), and chloramphenicol (against E. coli) with ECOFF or MIC90 ≤ 16 mg/L. When preclinical PK/PD targets were combined with human pharmacokinetics, Monte Carlo analysis showed that among the old antibiotics analyzed, there is clinical potential for polymyxin B against E. coli, K. pneumoniae, and A. baumannii; for temocillin against K. pneumoniae and E. coli; for fosfomycin against E. coli and K. pneumoniae; and for mecillinam against E. coli. Clinical studies are needed to verify the potential of those antibiotics to effectively treat infections by multi-drug resistant gram-negative bacteria.

CTX-M-producing Escherichia coli strains: resistance to temocillin, fosfomycin, nitrofurantoin and biofilm formation

Aim: ESBL-producing and bacterial biofilms-forming Escherichia coli are associated with antimicrobial treatment failure. This study aimed to investigate the phenotypic resistance mechanisms of CTX-M E. coli against old antibiotics - cell wall synthesis inhibitors temocillin, nitrofurantoin and fosfomycin. Materials & Methods: Susceptibility to old antibiotics testing was performed using disk diffusion method, biofilm formation was evaluated spectrophotometrically, and PCR was used for the determination of CTX-M type. Results & conclusion: Temocillin was active against nearly 93%, nitrofurantoin and fosfomycin, respectively, 91.7% and 98.6% of tested E. coli. Thus, it demonstrated to be a good alternative therapeutic option against ESBL infections. Bacteria resistant to old antibiotics had CTX-M-15 or CTX-M-15, TEM-1 and OXA-1 combinations. No significant association was found between CTX-M E. coli resistance to temocillin, nitrofurantoin and fosfomycin; however, the level of biofilm formation was found as not affected by the type of CTX-M β-lactamases.

Coexistence of virulence and β-lactamase genes in avian pathogenic Escherichia coli

Emergence of multidrug resistance in E. coli and advent of newer strains is becoming serious concern which requires keen observations. This study was designed to find the ciprofloxacin resistant E. coli isolates co-existed with multi-drug resistance along with β-lactamase production from poultry source, and finally the genome sequencing of these strains to explore genetic variations. Study constituted on isolation of n = 225 E. coli from broiler farms of central China which were further subjected to identification of resistance against ciprofloxacin followed by antibiogram of n = 26 antibiotics and identification of β-lactamase production. Whole genome resequencing was performed using Illumina HiSeq 4000 system. PCR results revealed predominant β-lactamase genes i.e.CTX-M, CTX-M-1, CTX-M3, TEM-1 and OXA. Furthermore, the MDR isolates were containing most of the tested virulence genes. The most prevalent virulence genes were pap-C, fim-C, fim-H, iuc-D, irp-2, tra-T, iro-N and iut-A. The single nucleotide polymorphisms (SNPs) loci mentioned in this data give valuable genetic markers to growing high-throughput techniques for fine-determination of genotyping of MDR and virulent isolates. Characterization of SNPs on functional basis shed new bits of knowledge on the evolution, disease transmission and pathogenesis of MDR E. coli isolates. In conclusion, these findings provide evidence that most of poultry E. coli are MDR, β-lactamase producers, and virulent which could be a zoonotic threat to the humans. The whole genome resequencing data provide higher resolution of resistance and virulence characteristics in E. coli which can further be used for the development of prevention and treatment strategies.

OUP accepted manuscript

Background

With increasing resistance to common antibiotics the treatment of urinary tract infections has become challenging and alternative therapeutic options are needed. In the present study, we evaluate the activity of three older and less frequently used antibiotics against MDR Enterobacterales.

Methods

Susceptibility of mecillinam, temocillin and nitroxoline was assessed in Enterobacterales isolated from urinary specimens with elevated MICs of third-generation cephalosporins. Susceptibility was determined by the recommended reference MIC methods and additionally by disc diffusion. All isolates were characterized for common β-lactamases by phenotypic and molecular assays.

Results

In total 394 Enterobacterales were included. The most common resistance mechanisms were ESBLs (n = 273), AmpC (n = 132), carbapenemases [n = 12, including OXA-48-like (n = 8), VIM (n = 2), KPC (n = 1) and NDM (n = 1)] or others (n = 2). Resistance was observed in 59% of isolates to ceftazidime, in 41% to piperacillin/tazobactam and in 54% to ciprofloxacin. In comparison, resistance was less frequent against mecillinam (15%), temocillin (13%) or nitroxoline (2%). Mecillinam showed higher activity in Enterobacter spp., Escherichia coli and in OXA-48-like-producing isolates compared with temocillin, which was more active in Proteus mirabilis and in ESBL-producing isolates. Activity of nitroxoline was high against all isolates, including carbapenemase-producing isolates. Correlation between disc diffusion and MIC methods was good for mecillinam and moderate for temocillin and nitroxoline.

Conclusions

Mecillinam, temocillin and nitroxoline show good to excellent in vitro activity in MDR Enterobacterales. The activity of mecillinam and temocillin was higher in certain species and restricted depending on β-lactamase production while nitroxoline showed universally high activity irrespective of species or β-lactamase present.

Activity of temocillin against third-generation cephalosporin-resistant Escherichia coli and Klebsiella pneumoniae bloodstream isolates from a clinical trial

Background

Extended spectrum β-lactamase (ESBL) and AmpC-producing Gram-negative bacilli contribute significantly to the antimicrobial resistance (AMR) burden worldwide. Temocillin is an intravenous semisynthetic antibiotic that is stable to hydrolysis by ESBLs and AmpC. Temocillin may be a treatment option for serious infections due to these organisms.

Methods

Third-generation cephalosporin-resistant Escherichia coli and Klebsiella pneumoniae isolates from the MERINO trial were collected. The majority originated from the urinary tract. Isolates had previously undergone whole genome sequencing (WGS) to identify antimicrobial resistance genes. Temocillin minimum inhibitory concentration (MIC) values were determined by broth microdilution (BMD) with a concentration range of 2 to 128 mg/L. A recent EUCAST guideline has recommended clinical breakpoints for urinary E. coli, Klebsiella spp. (except K. aerogenes) and Proteus mirabilis (resistant >16 mg/L).

Results

317 index bloodstream isolates (275 E. coli and 42 K. pneumoniae) were used. The frequency of β-lactamases among isolates was: CTX-M-15 (56%), OXA-1 (31%), CTX-M-27 (14%), CTX-M-14 (12%) and CMY-2 (8%). Overall, 95% of isolates were susceptible, increased exposure according to EUCAST clinical breakpoints v11.0. Summary MIC values were obtained: MIC50 was 8 mg/L and MIC90 was16 mg/L (range ≤2 to ≥128 mg/L) and did not differ markedly between species. Higher MIC values were seen among isolates that produced more than one β-lactamase but this did not appear to be specific to a single β-lactamase.

Conclusions

Temocillin demonstrated favourable in vitro activity against ceftriaxone-resistant Enterobacterales bloodstream isolates and may be a suitable agent to be trialled for treatment of serious infections due to these organisms.

Is the Antibacterial Activity of Multi-Walled Carbon Nanotubes (MWCNTs) Related to Antibiotic Resistance? An Assessment in Clinical Isolates

Antimicrobial resistance has spread globally, compromising the treatment of common infections. This feature is particularly harmful for nosocomial pathogens that can survive on hospital surfaces. Research studies have been conducted to evaluate new materials that are able to counteract the microbial growth and the colonization of the hospital environment. In this context, nanotechnologies have showed encouraging applications. We investigated the antibacterial activity of multi-walled carbon nanotubes (MWCNTs), both pristine (p) and functionalized (f), at concentrations of 50 and 100 μg mL⁻¹, against bacterial strains isolated from hospital-acquired infections, and this activity was correlated with the antibiotic susceptibility of the strains. The inhibiting effect of MWCNTs occurred for both types and doses tested. Moreover, f-MWCNTs exerted a greater inhibiting effect, with growth decreases greater than 10% at 24 h and 20% at 48 h compared to p-MWCNTs. Moreover, a lower inhibitory effect of MWCNTs, which was more lasting in Gram-positives resistant to cell wall antibiotics, or temporary in Gram-negatives resistant to nucleic acid and protein synthesis inhibitors, was observed, highlighting the strong relation between antibiotic resistance and MWCNT effect. In conclusion, an antimicrobial activity was observed especially for f-MWCNTs that could therefore be loaded with bioactive antimicrobial molecules. However, this potential application of CNTs presupposes the absence of toxicity and therefore total safety for patients.

Genetic basis of molecular mechanisms in β-lactam resistant gram-negative bacteria

Antibiotic-resistant bacteria are considered one of the major global threats to human and animal health. The most harmful among the resistant bacteria are β-lactamase producing Gram-negative species (β-lactamases). β-lactamases constitute a paradigm shift in the evolution of antibiotic resistance. Therefore, it is imperative to present a comprehensive review of the mechanisms responsible for developing antimicrobial resistance. Resistance due to β-lactamases develops through a variety of mechanisms, and the number of resistant genes are involved that can be transferred between bacteria, mostly via plasmids. Over time, these new molecular-based resistance mechanisms have been progressively disclosed. The present review article provides information on the recent findings regarding the molecular mechanisms of resistance to β-lactams in Gram-negative bacteria, including CTX-M-type ESBLs with methylase activity, plasmids harbouring phages with β-lactam resistance genes, the co-presence of β-lactam resistant genes of unique combinations and the presence of β-lactam and non-β-lactam antibiotic-resistant genes in the same bacteria. Keeping in view, the molecular level resistance development, multifactorial and coordinated measures may be taken to counter the challenge of rapidly increasing β-lactam resistance.

Trends in prevalence of extended-spectrum beta-lactamase-producing Escherichia coli isolated from patients with community- and healthcare-associated bacteriuria: results from 2014 to 2020 in an urban safety-net healthcare system

BACKGROUND

The prevalence of infections caused by extended-spectrum beta-lactamase producing Escherichia coli (ESBL-E. coli) is increasing worldwide, but the setting in which this increase is occurring is not well defined. We compared trends and risk factors for ESBL-E. coli bacteriuria in community vs healthcare settings.

METHODS

We collected electronic health record data on all patients with E. coli isolated from urine cultures in a safety-net public healthcare system from January 2014 to March 2020. All analyses were stratified by healthcare-onset/associated (bacteriuria diagnosed > 48 h after hospital admission or in an individual hospitalized in the past 90 days or in a skilled nursing facility resident, N = 1277) or community-onset bacteriuria (bacteriuria diagnosed < 48 h after hospital admission or in an individual seen in outpatient clinical settings without a hospitalization in the past 90 days, N = 7751). We estimated marginal trends from logistic regressions to evaluate annual change in prevalence of ESBL-E. coli bacteriuria among all bacteriuria. We evaluated risk factors using logistic regression models.

RESULTS

ESBL-E. coli prevalence increased in both community-onset (0.91% per year, 95% CI 0.56%, 1.26%) and healthcare-onset/associated (2.31% per year, CI 1.01%, 3.62%) bacteriuria. In multivariate analyses, age > 65 (RR 1.88, CI 1.17, 3.05), male gender (RR 2.12, CI 1.65, 2.73), and Latinx race/ethnicity (RR 1.52, CI 0.99, 2.33) were associated with community-onset ESBL-E. coli. Only male gender (RR 1.53, CI 1.03, 2.26) was associated with healthcare-onset/associated ESBL-E. coli.

CONCLUSIONS

ESBL-E. coli bacteriuria frequency increased at a faster rate in healthcare-associated settings than in the community between 2014 and 2020. Male gender was associated with ESBL-E. coli bacteriuria in both settings, but additional risks-age > 65 and Latinx race/ethnicity-were observed only in the community.

Temocillin susceptibility among Enterobacterales strains recovered from blood culture in France

Temocillin is used for several years in some European countries but, only since 2015 in France. We assessed the susceptibility of Enterobacterales strains isolated from blood culture 1 year before (2014) and 2 years after (2017) its use in France. 1,387 strains were included by 17 clinical laboratories located throughout France: 363 in 2014 and 1,024 in 2017. The rate of resistance to temocillin was 4.6% and 26.7% in 3rd generation cephalosporin (3GC) susceptible and resistant strains respectively. Cephalosporinase-overproducer (COPE) strains were significantly more resistant to temocillin (37.7%) than ESBL-producer (ESBL-PE) (23.5%) (P < 0.01). The rate of temocillin resistance was correlated to the number of inactive beta-lactams. The rate of resistance to temocillin trend to increase from 13.9% in 2014 to 23.9% in 2017 (P < 0.01). Temocillin remains highly active against Enterobacterales but the trend in resistance should be assessed over time.

Treatment and Outcomes of Children With Febrile Urinary Tract Infection Due to Extended Spectrum Beta-lactamase-producing Bacteria in Europe: TOO CUTE Study

BACKGROUND

The prevalence of extended-spectrum beta-lactamase producing Εnterobacteriaceae (ESBL-PE) is increasing globally. ESBL-PE are an important cause of urinary tract infections (UTIs) in children. We aimed to characterize the clinical presentation, treatment and outcomes of childhood UTI caused by ESBL-PE in Europe.

METHODS

Multicenter retrospective cohort study. Children 0 to 18 years of age with fever, positive urinalysis and positive urine culture for an ESBL-PE uropathogen, seen in a participating hospital from January 2016 to July 2017, were included.

MAIN OUTCOME MEASURES

Primary outcome measure: day of defervescence was compared between (1) initial microbiologically effective treatment (IET) versus initial microbiologically ineffective treatment (IIT) and (2) single initial antibiotic treatment versus combined initial antibiotic treatment.

SECONDARY OUTCOME MEASURES

Clinical and microbiologic failure of initial treatment.

RESULTS

We included 142 children from 14 hospitals in 8 countries. Sixty-one children had IET and 77 IIT. There was no statistical difference in time to defervescence for effective/ineffective groups (P = 0.722) and single/combination therapy groups (P = 0.574). Two of 59 (3.4%) and 4/66 (6.1%) patients exhibited clinical failure during treatment (P = 0.683) when receiving IET or IIT, respectively. Eight of 51 (15.7%) receiving IET and 6/58 (10.3%) receiving IIT patients (P = 0.568) had recurring symptoms/signs suggestive of a UTI. Recurrence of a UTI occurred 15.5 days (interquartile range, 9.0-19.0) after the end of treatment.

CONCLUSIONS

Time to defervescence and clinical failure did not differ between IET/IIT groups. Non-carbapenem beta-lactam antibiotics may be used for the empiric treatment of ESBL febrile UTIs, until susceptibility testing results become available.

Activity of temocillin against ESBL-, AmpC-, and/or KPC-producing Enterobacterales isolated in Poland

We evaluated the in vitro effectiveness of temocillin and several commonly used antimicrobials against Enterobacterales bacteria in isolates from Polish patients. We tested 400 isolates: 260 extended-spectrum β-lactamase (ESBL)- and/or ampC β-lactamase (AmpC)-producing isolates; 40 Klebsiella pneumoniae carbapenemase (KPC)-producing isolates; and 100 ESBL-, AmpC-, and KPC-negative isolates. The minimal inhibitory concentrations (MICs) of temocillin and 16 other antimicrobials were determined by reference microdilution. We also determined the activities of fosfomycin and ceftazidime/avibactam in KPC-producing isolates. The antibiotic sensitivities were interpreted according to EUCAST, BSAC, and CLSI criteria. Overall, 91% of the isolates were susceptible to temocillin using the urinary tract infection breakpoint (≤ 32 mg/L), and 61.8% were susceptible using the systemic infection breakpoint (≤ 8 mg/L). Meropenem and imipenem were the most active drugs (MIC50 values of 0.06 and 0.5 mg/L, respectively). Colistin and ertapenem (both MIC50 = 0.12 mg/L) were less active than meropenem or imipenem, but some strains were 77% susceptible to each of them. Among the KPC-producing isolates, 42.5% had MIC values of ≤ 32 mg/L (urinary tract infection breakpoint), but 100% were resistant to temocillin (systemic infection breakpoint). Ceftazidime/avibactam was active against 100% of the KPC-producing isolates, and fosfomycin was active against 40%. The empirical susceptibility rate observed among the urinary isolates suggests that temocillin may be considered as an alternative to carbapenems in the absence of KPC-producing bacteria. With regard to isolates from other sources, temocillin might be useful as a documented therapy agent or an empirical treatment in hospitals with a low prevalence of ESBL/AmpC-producing strains.

Microbial risk factors for treatment failure of pivmecillinam in community-acquired urinary tract infections caused by ESBL-producing Escherichia coli

The aim of this study was to identify microbial risk factors for treatment failure of pivmecillinam in community-acquired urinary tract infections (ca-UTIs) caused by ESBL-producing Escherichia coli. Eighty-nine ESBL-producing E. coli isolated from women suffering from ca-UTIs were included. The susceptibilities to mecillinam were determined using MIC gradient strip. Whole genome sequencing was performed on a MiSeq platform, and genome assembly was performed using SPAdes v3.11.0. Neither mecillinam MICs nor ESBL genotypes were associated with treatment outcome of patients treated with pivmecillinam. Specific STs, however, showed significant differences in treatment outcome. Patients infected with ST131 were more likely to experience treatment failure compared to patients infected with non-ST131 (p 0.02) when adjusted for pivmecillinam dose, mecillinam MIC and severity of infection. Patients infected with ST69 were more often successfully treated compared to patients infected with non-ST69 (p 0.04). Patients infected with bla_CTX-M-15 ST131 strains were more likely to experience treatment failure than those infected with non-bla_CTX-M-15 ST131 strains (p 0.02). The results suggest that specific STs are associated with the clinical efficacy of pivmecillinam. Further studies with a larger number of strains, including a larger number of mecillinam resistant strains, are needed to confirm these results.

Temocillin against Enterobacteriaceae isolates from community-acquired urinary tract infections: low rate of resistance and good accuracy of routine susceptibility testing methods

Background

Temocillin is an old 'revived' antibiotic that may play an important role in the treatment of febrile urinary tract infection (UTI). Data regarding its activity against current Enterobacteriaceae isolates as well as the performance of routine susceptibility testing methods are, however, scarce.

Objectives

To determine the MICs of temocillin for Enterobacteriaceae strains reflecting the current epidemiology and to analyse the accuracy of three commercial methods.

Methods

Enterobacteriaceae isolates causing community-acquired UTI were prospectively collected from September 2015 to January 2017 in two French centres. Temocillin MIC was determined by agar dilution (AD) as the reference method and then compared with: (i) susceptibility testing by disc diffusion; (ii) MIC determination by Etest; and (iii) MIC estimation by the Vitek 2 automated system.

Results

A total of 762 Enterobacteriaceae were analysed comprising 658 (86.4%) Escherichia coli and 37 (4.9%) ESBL-producing isolates. Susceptibility rate assessed by AD was 99.6% according to the 8 mg/L clinical breakpoint and was significantly lower against the ESBL-producing isolates than the non-ESBL-producing isolates (94.6% versus 99.9%, P < 0.01). The MIC50 and MIC90 for the total set were 3 and 6 mg/L, respectively. According to the 8 mg/L clinical breakpoint, the major error rate was <1% for disc diffusion and Etest, and significantly higher for Vitek 2 (4.3%, P < 0.01), but still low. No very major error was noticed.

Conclusions

Temocillin showed a high level of activity against Enterobacteriaceae from community-acquired UTI and good to excellent reliability of routine methods for susceptibility testing in such a setting.

Emerging clinical role of pivmecillinam in the treatment of urinary tract infections caused by Extended Spectrum βeta-lactamase (ESBL) producing Enterobacteriaceae

BACKGROUND

Extended Spectrum βeta-lactamase (ESBL)-producing Enterobacteriaceae causing urinary tract infections (UTIs) appear resistant to many common oral agents. There is a growing need to discover new antibiotics to combat with emerging antibiotic resistance problem. Until the discovery of new antimicrobials, we can bring back forgotten antibiotics to our clinical formulary. Pivmecillinam (prodrug of mecillinam), an oral antimicrobial agent is effective against ESBL producing organisms. We analysed the sensitivity rates of ESBL-producing Enterobacteriaceae from urine samples to mecillinam and to document if pivmecillinam is a suitable alternative option in the treatment of UTI.

MATERIALS/METHODS

This retrospective study was conducted from September 2015 to September 2017. Data were collected from the pathology information system. Antimicrobial sensitivity testing on ESBL-producing Enterobacteriaceae isolates was carried out by disc diffusion method in accordance with The European Committee on Antimicrobial Susceptibility Testing.

RESULTS

A total of 986 ESBL-producing Enterobacteriaceae were tested for mecillinam during the study period. Of 986 organisms, Escherichia coli was the most common organism (889); followed by Klebsiella species (71) and others Enterobacteriaceae (26). Mecillinam sensitivity was found in 96% Escherichia coli (855/889 isolates), 83% Klebsiella species (59/71 isolates) and 88% other Enterobacteriaceae (23/26 isolates). Overall 95% (935/986 isolates) of ESBL-producing urinary isolates were sensitive to mecillinam.

CONCLUSIONS

Pivmecillinam appears to be suitable option to treat ESBL-producing Enterobacteriaceae causing uncomplicated UTI. Our results showed low resistance rate to mecillinam. We recommend the use of pivmecillinam in uncomplicated UTIs because of ESBL-producing Enterobacteriaceae. More studies on in vitro activity of mecillinam against ESBL producing organism and its use and clinical outcome should be tried in future.

The use of nitrofurantoin for children with acute cystitis caused by extended-spectrum Β-lactamase-producing Escherichia coli

BACKGROUND

Acute cystitis in children caused by extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (E. coli) is on the rise. Treatment of these is usually parenteral treatment. The aim of this study was to investigate the clinical and microbiological efficacy of oral nitrofurantoin treatment in children with lower urinary tract infection (UTI) caused by ESBL-producing E. coli.

METHODS

Fifty children with lower UTI due to ESBL-producing E. coli were prospectively studied. Demographic data, clinical condition, laboratory values, treatment regimens, and complications of the patients were recorded. Urine samples were obtained by transurethral catheterization or clean catch; urine bags were not used for specimen collection for culture. Patients with lower UTI due to ESBL-producing E. coli and found to be susceptible to nitrofurantoin were given oral nitrofurantoin. Patients were re-evaluated 3-4 days after the end of treatment. Renal scintigraphy was performed 1-3 months after the end of treatment.

RESULTS

A total of 50 pediatric patients (48 females and 2 males) were enrolled into study. The mean age was 7.5 ± 3.96 years (range, 1-17 years). The duration of nitrofurantoin treatment was 10 days. Bacteriological response was observed in 49 of 50 patients (98%). No patient had symptoms after treatment. No significant side-effect was observed in any of the patients. All patients had normal serum creatinine values. Renal scintigraphic study, which was performed in all patients 1-3 months after completion of treatment, demonstrated the non-scarring in 48 of 50 patients (96%).

CONCLUSIONS

UTIs due to ESBL-producing E. coli are a serious problem because of the bacteria's multidrug antibiotic resistance pattern. This study suggests that oral nitrofurantoin treatment could be a good alternative for lower UTI caused by ESBL-producing E. coli in pediatric patients.

Pivmecillinam compared to other antimicrobials for community-acquired urinary tract infections with Escherichia coli, ESBL-producing or not - a retrospective cohort study

Objectives

To compare the therapeutic effect of pivmecillinam and other common oral antibiotics for community-acquired urinary tract infections (UTIs) caused by Extended Spectrum Beta-Lactamase (ESBL)- or non-ESBL-producing Escherichia coli.

Methods

Retrospective cohort study from 2010 to mid-2016 with data from the regional Laboratory Database and three national databases on antibiotic prescriptions, hospital admission, and mortality, respectively. Primary care patients (≥18 years) empirically treated for UTI caused by non-ESBL- or ESBL-producing E. coli (non-ESBL and ESBL E. coli) were included. Seven antibiotics, commonly used empirically for UTI, were investigated. Treatment failure measured as the redemption of a new antibiotic prescription or admission to hospital due to UTI. Cox proportional hazard ratios and adjusted risk differences along with 95% confidence intervals were calculated for 14 and 30 days, respectively.

Results

Thirty-six thousand two hundred and ninety-three (95.7%) and 1624 (4.3%) cases were included in the non-ESBL and ESBL groups, respectively. Male sex, high age, ESBL production, and resistance to empirical therapy were found to independently increase the risk of treatment failure. Compared to pivmecillinam, ciprofloxacin had significantly lower treatment failure for non-ESBL E. coli, but significantly higher treatment failure in ESBL E. coli. There was no significant difference between nitrofurantoin and pivmecillinam.

Conclusion

All antibiotics seem to have a higher risk of treatment failure for UTI caused by ESBL-producing E. coli as compared to non-ESBL-producing E. coli. At present, nitrofurantoin and pivmecillinam seem to be the most relevant orally available therapies for E. coli UTI. Local resistance data should guide which of the two that should be the contemporary first-line option.

Pharmacokinetics and Pharmacodynamics of Temocillin

Temocillin, a 6-α-methoxy derivative of ticarcillin, is a forgotten antibiotic that has recently been rediscovered, and issues about clinical breakpoints and optimal therapeutic regimens are still ongoing. Temocillin spectrum is almost restricted to Enterobacteriaceae. The addition of the α-methoxy moiety on ticarcillin confers resistance to hydrolysis by Ambler classes A and C β-lactamases (extended spectrum β-lactamases, Klebsiella pneumoniae carbapenemase and AmpC hyperproduced enzymes). Temocillin is bactericidal, and the effect of inoculum size on its activity is relatively mild. The proportion of spontaneous resistant mutants in vitro to temocillin is low, as found in vivo. After intravenous infusion, temocillin showed a prolonged elimination half-life of approximately 5 h. The percentage of protein binding of temocillin is high (approximately 80%), and is concentration-dependent. Temocillin clearance is mainly renal, and urinary recovery is high, ranging from 72 to 82% after 24 h. Furthermore, the penetration of temocillin into bile and peritoneal fluid is high, but poor into cerebrospinal fluid. The cumulative percentage of a 24-h period during which the free drug concentration exceeds the minimum inhibitory concentration (fT > MIC) at steady-state pharmacokinetic conditions seems to be the best pharmacokinetic/pharmacodynamic (PK/PD) index correlating with temocillin efficacy. An fT > MIC of 40-50% is associated with antibacterial effect and survival in vivo. Monte Carlo simulations performed in critically ill patients showed that the 2 g every 12 h and 2 g every 8 h regimens provide a 95% probability of target attainment of 40% fT > MIC up to an MIC of 8 mg/L. In less severely ill patients or in specific foci of infection, such as urinary tract infection, a 4 g daily regimen should be adequate for strains with temocillin MIC up to 16 mg/L. Data regarding actual wild-type MIC distribution, clinical efficacy, PK profiling in volunteers or patients, and PD targets are scarce, and further studies are required to support appropriate dosing recommendations and determination of clinical breakpoints.

Resurrecting Old β-Lactams: Potent Inhibitory Activity of Temocillin against Multidrug-Resistant Burkholderia Species Isolates from the United States

Burkholderia spp. are opportunistic human pathogens that infect persons with cystic fibrosis and the immunocompromised. Burkholderia spp. express class A and C β-lactamases, which are transcriptionally regulated by PenR_A through linkage to cell wall metabolism and β-lactam exposure. The potency of temocillin, a 6-methoxy-β-lactam, was tested against a panel of multidrug-resistant (MDR) Burkholderia spp. In addition, the mechanistic basis of temocillin activity was assessed and compared to that of ticarcillin. Susceptibility testing with temocillin and ticarcillin was conducted, as was biochemical analysis of the PenA1 class A β-lactamase and AmpC1 class C β-lactamase. Molecular dynamics simulations (MDS) were performed using PenA1 with temocillin and ticarcillin. The majority (86.7%) of 150 MDR Burkholderia strains were susceptible to temocillin, while only 4% of the strains were susceptible to ticarcillin. Neither temocillin nor ticarcillin induced bla expression. Ticarcillin was hydrolyzed by PenA1 (k _cat/K_m = 1.7 ± 0.2 μM^-1 s^-1), while temocillin was slow to form a favorable complex (apparent K_i [K_{i  app}] = ∼2 mM). Ticarcillin and temocillin were both potent inhibitors of AmpC1, with K_{i  app} values of 4.9 ± 1.0 μM and 4.3 ± 0.4 μM, respectively. MDS of PenA revealed that ticarcillin is in an advantageous position for acylation and deacylation. Conversely, with temocillin, active-site residues K73 and S130 are rotated and the catalytic water molecule is displaced, thereby slowing acylation and allowing the 6-methoxy of temocillin to block deacylation. Temocillin is a β-lactam with potent activity against Burkholderia spp., as it does not induce bla expression and is poorly hydrolyzed by endogenous β-lactamases.

Pharmacokinetics and Pharmacodynamics of Fosfomycin and Its Activity against Extended-Spectrum-β-Lactamase-, Plasmid-Mediated AmpC-, and Carbapenemase-Producing Escherichia coli in a Murine Urinary Tract Infection Model

Fosfomycin has become an attractive treatment alternative for urinary tract infections (UTIs) due to increasing multidrug resistance (MDR) in Escherichia coli. In this study, we evaluated the pharmacokinetic (PK) and pharmacodynamic (PD) indices of fosfomycin and its in vivo activity in an experimental murine model of ascending UTI. Subcutaneous administration of fosfomycin showed that the mean peak plasma concentrations of fosfomycin were 36, 280, and 750 mg/liter following administration of a single dose of 0.75, 7.5, and 30 mg/mouse, respectively, with an elimination half-life of 28 min, and urine peak concentrations of 1,100, 33,400, and 70,000 mg/liter expected to be sustained above 1 mg/liter (MIC of the test strain, NU14) for 5, 8, and 9.5 h, respectively. The optimal PK/PD indices for reducing urine colony counts (number of CFU per milliliter) were determined to be the area under the concentration-time curve/MIC from 0 to 72 h and the maximum concentration/MIC on the basis of the dose-dependent bloodstream PK and the results of an evaluation of six dosing regimens. With a dosing regimen of 15 mg/mouse twice (every 36 h), fosfomycin significantly reduced the number of CFU per milliliter of all susceptible strains in urine, including clinical MDR strains, except for one clinical strain (P = 0.062). Variable degrees of reduction were observed in the bladder and kidneys. No significant reductions in the number of CFU per milliliter were observed with the resistant strains. In conclusion, fosfomycin shows concentration-dependent in vivo activity, and the results suggest that fosfomycin is an effective alternative to carbapenems in treating MDR E. coli in uncomplicated UTIs. The data on the effectiveness of fosfomycin against the MDR isolates along with the results of PK/PD modeling should facilitate the further development of improved recommendations for its clinical use.

Clinical isolates of Escherichia coli solely resistant to mecillinam: prevalence and epidemiology

In routine susceptibility testing of Gram-negative bacteria, a particular resistance phenotype was observed: an Escherichia coli isolate from a urine sample exhibited resistance solely to mecillinam (MEC) but was fully susceptible to other β-lactam antibiotics (MEC-R-BL-S). The objectives as this study were to determine the prevalence of this phenotype and to describe the phenotype, molecular epidemiology and genetic background. Between 1 January 2014 and 31 January 2016, MEC-R-BL-S E. coli isolates from urine were collected and genes previously reported as mostly involved in MEC resistance were analysed. The genetic relatedness among isolates was investigated by repetitive element sequence-based PCR (rep-PCR) and multilocus sequence typing (MLST). Ten MEC-R-BL-S isolates were collected, accounting for 0.4% (10/2547) of all E. coli obtained from urine samples, 0.9% (10/1135) of ampicillin-susceptible E. coli isolates and 9.6% (10/104) of MEC-R E. coli isolates. The isolates appeared as small colonies with round morphology and had impaired fitness. The isolates were not clonal and belonged to various extraintestinal or commensal E. coli phylogroups. Mutations in the cysB gene were evidenced in all clinical isolates. In conclusion, microbiologists should be aware of these isolates with a particular susceptibility phenotype, which is not due to error in disk diffusion but is a real non-enzymatic antibiotic resistance pattern.

Membrane-Active Hydantoin Derivatives as Antibiotic Agents

Hydantoin (imidazolidinedione) derivatives such as nitrofurantoin are small molecules that have aroused considerable interest recently due to their low rate of bacterial resistance. However, their moderate antimicrobial activity may hamper their application combating antibiotic resistance in the long run. Herein, we report the design of bacterial membrane-active hydantoin derivatives, from which we identified compounds that show much more potent antimicrobial activity than nitrofurantoin against a panel of clinically relevant Gram-positive and Gram-negative bacterial strains. These compounds are able to act on bacterial membranes, analogous to natural host-defense peptides. Additionally, these hydantoin compounds not only kill bacterial pathogens rapidly but also prevent the development of methicillin-resistant Staphylococcus aureus (MRSA) bacterial resistance under the tested conditions. More intriguingly, the lead compound exhibited in vivo efficacy that is much superior to vancomycin by eradicating bacteria and suppressing inflammation caused by MRSA-induced pneumonia in a rat model, demonstrating its promising therapeutic potential.

Troubled water under the bridge: Screening of River Mur water reveals dominance of CTX-M harboring Escherichia coli and for the first time an environmental VIM-1 producer in Austria

Antibiotic resistant bacteria (ARB) in the aquatic environment are reported from all over the world and their presence in the environment has become quite common. The current most prominent example is the presence of beta-lactamases harboring Enterobacteriaceae. The aim of this study was to investigate the presence and diversity (on the genetic and phenotypic levels) of extended spectrum beta-lactamases (ESBL) and carbapenemases harboring Enterobacteriaceae from the River Mur in the center of Graz, Austria's second largest city. Thus over a period of four months water samples were taken, filtrated and screened for these bacteria. All samples revealed ESBL harboring Enterobacteriaceae, of which all with only one exception were Escherichia coli. Dominant ESBL gene family was CTX-M, represented by subgroups CTX-M-1 group, CTX-M-2 group and CTX-M-9 group. Surprisingly co-resistances to non-beta-lactam antibiotics were low, only resistance to trimethoprim was detected in 50% of all (70) isolates. One Klebsiella oxytoca with GES-1 was isolated. To date, GES ESBL has never been reported from Austria before and only rarely from other European countries. Screening for carbapenemase harboring Enterobacteriaceae revealed one Enterobacter cloacae with the gene for VIM-1. Members sharing the same multi-locus-sequence-type (MLST) as well as members of the same rep PCR clusters occurred at different sampling time points. ESBL-harboring Enterobacteriaceae are common in Austrian river water, is dominated by Escherichia coli and CTX-M enzymes. Furthermore, some of the isolates could be linked to different origins.

In vitro efficacy of 16 antimicrobial drugs against a large collection of β-lactamase-producing isolates of extraintestinal pathogenic Escherichia coli from dogs and cats

PURPOSE

The aim of this study was to assess the in vitro efficacy of candidate antimicrobials against extended-spectrum β-lactamase (ESBL)-producing isolates of extraintestinal pathogenic Escherichia coli (ExPEC) from companion animals.

METHODOLOGY

A total of 90 ESBL-producing ExPEC isolates from dogs and cats were tested for susceptibility to 16 antimicrobials with the agar dilution method. We also identified the ESBLs and AmpC β-lactamases of these isolates with PCR and DNA sequencing.Results/Key findings. All isolates were susceptible to meropenem, tebipenem and amikacin (AMK), and various proportions were susceptible to latamoxef (LMX, 97.8 %), fosfomycin (FOM, 97.8 %), faropenem (FPM, 96.7 %), nitrofurantoin (NFT, 96.7 %), flomoxef (FMX, 93.3 %), piperacillin/tazobactam (PTZ, 92.2 %), cefmetazole (CMZ, 91.1 %), chloramphenicol (80.0 %), trimethoprim/sulfamethoxazole (64.4 %), amoxicillin/clavulanic acid (63.3 %), ceftibuten (60.0 %), tetracycline (52.2 %) and enrofloxacin (10.0 %). A genetic analysis showed that 83 of the 90 (92.2 %) isolates were positive for CTX-M-type genes: CTX-M-14 (n=26), CTX-M-27 (n=20), CTX-M-55 (n=17), CTX-M-15 (n=12), CTX-M-2 (n=5), CTX-M-24 (n=2), CTX-M-104 (n=2) and CTX-M-3 (n=1). Eight isolates also expressed AmpC β-lactamase phenotypes.

CONCLUSION

This study demonstrates that the susceptibility rates to PTZ, CMZ, LMX, AMK, FOM, FPM, NFT and FMX were similar to those to carbapenems (>90 %), implying that these drugs are available alternatives to carbapenems for the treatment of companion animals infected with ExPEC-producing CTX-M-type ESBLs. Further in vivo studies of the effective use of these antimicrobials are required.

Global research trends of World Health Organization's top eight emerging pathogens

BACKGROUND

On December 8th, 2015, World Health Organization published a priority list of eight pathogens expected to cause severe outbreaks in the near future. To better understand global research trends and characteristics of publications on these emerging pathogens, we carried out this bibliometric study hoping to contribute to global awareness and preparedness toward this topic.

METHOD

Scopus database was searched for the following pathogens/infectious diseases: Ebola, Marburg, Lassa, Rift valley, Crimean-Congo, Nipah, Middle Eastern Respiratory Syndrome (MERS), and Severe Respiratory Acute Syndrome (SARS). Retrieved articles were analyzed to obtain standard bibliometric indicators.

RESULTS

A total of 8619 journal articles were retrieved. Authors from 154 different countries contributed to publishing these articles. Two peaks of publications, an early one for SARS and a late one for Ebola, were observed. Retrieved articles received a total of 221,606 citations with a mean ± standard deviation of 25.7 ± 65.4 citations per article and an h-index of 173. International collaboration was as high as 86.9%. The Centers for Disease Control and Prevention had the highest share (344; 5.0%) followed by the University of Hong Kong with 305 (4.5%). The top leading journal was Journal of Virology with 572 (6.6%) articles while Feldmann, Heinz R. was the most productive researcher with 197 (2.3%) articles. China ranked first on SARS, Turkey ranked first on Crimean-Congo fever, while the United States of America ranked first on the remaining six diseases. Of retrieved articles, 472 (5.5%) were on vaccine - related research with Ebola vaccine being most studied.

CONCLUSION

Number of publications on studied pathogens showed sudden dramatic rise in the past two decades representing severe global outbreaks. Contribution of a large number of different countries and the relatively high h-index are indicative of how international collaboration can create common health agenda among distant different countries.

Extended-spectrum β-lactamase-producing bacteria caused less than 5% of urinary tract infections in a paediatric emergency centre

AIM

The last decade has seen a significant increase in extended-spectrum β-lactamase (ESBL) secreting organisms responsible for paediatric urinary tract infections (UTIs), particularly in community-acquired infections. These expose patients to the risks of antibiotic treatment failure and renal scarring. This prospective study examined the prevalence and risk factors of febrile ESBL UTIs and their treatment in the paediatric emergency department of a university hospital.

METHODS

In this prospective observational study, all children from 0 to 16 years of age with febrile UTIs were included from May 2012 to April 2013. Cases with and without ESBL involvement were compared.

RESULTS

Of the 474 diagnosed febrile UTIs, 22 (4.6%) with a 95% confidence interval (95% CI) of 2.9-6.9 were due to an ESBL-producing organism. Escherichia coli was found in 85% of cases. Significant odds ratios (OR) for ESBL urinary tract infections were prior hospitalisation (OR 4.1, 95% CI 1.6-10.8), urinary tract abnormalities (OR 3.9, 95% CI 1.5-10.2) and previous antibiotic treatment (OR 3.1, 95% CI 1.2-8.8). All ESBL urinary tract infections had positive outcomes.

CONCLUSION

The prevalence of febrile ESBL urinary tract infections was less than 5% in a paediatric emergency department. This low rate was not high enough to justify changing our guidelines.

β-Lactams and β-Lactamase Inhibitors: An Overview

β-Lactams are the most widely used class of antibiotics. Since the discovery of benzylpenicillin in the 1920s, thousands of new penicillin derivatives and related β-lactam classes of cephalosporins, cephamycins, monobactams, and carbapenems have been discovered. Each new class of β-lactam has been developed either to increase the spectrum of activity to include additional bacterial species or to address specific resistance mechanisms that have arisen in the targeted bacterial population. Resistance to β-lactams is primarily because of bacterially produced β-lactamase enzymes that hydrolyze the β-lactam ring, thereby inactivating the drug. The newest effort to circumvent resistance is the development of novel broad-spectrum β-lactamase inhibitors that work against many problematic β-lactamases, including cephalosporinases and serine-based carbapenemases, which severely limit therapeutic options. This work provides a comprehensive overview of β-lactam antibiotics that are currently in use, as well as a look ahead to several new compounds that are in the development pipeline.

Nosocomial infection and its molecular mechanisms of antibiotic resistance

Nosocomial infection is a kind of infection, which is spread in various hospital environments, and leads to many serious diseases (e.g. pneumonia, urinary tract infection, gastroenteritis, and puerperal fever), and causes higher mortality than community-acquired infection. Bacteria are predominant among all the nosocomial infection-associated pathogens, thus a large number of antibiotics, such as aminoglycosides, penicillins, cephalosporins, and carbapenems, are adopted in clinical treatment. However, in recent years antibiotic resistance quickly spreads worldwide and causes a critical threat to public health. The predominant bacteria include Methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, and Acinetobacter baumannii. In these bacteria, resistance emerged from antibiotic resistant genes and many of those can be exchanged between bacteria. With technical advances, molecular mechanisms of resistance have been gradually unveiled. In this review, recent advances in knowledge about mechanisms by which (i) bacteria hydrolyze antibiotics (e.g. extended spectrum β-lactamases, (ii) AmpC β-lactamases, carbapenemases), (iii) avoid antibiotic targeting (e.g. mutated vanA and mecA genes), (iv) prevent antibiotic permeation (e.g. porin deficiency), or (v) excrete intracellular antibiotics (e.g. active efflux pump) are summarized.