Trends in the frequency of multiple drug-resistant Enterobacteriaceae and their susceptibility to ertapenem, imipenem, and other antimicrobial agents: data from the Study for Monitoring Antimicrobial Resistance Trends 2002 to 2007

Modulating Liquid-Liquid Phase Separation of Nck Adaptor Protein against Enteropathogenic Escherichia coli Infection

Signaling proteins often form biomolecular condensates through liquid-liquid phase separation (LLPS) during intracellular signal transduction. Modulating the LLPS property of intracellular protein condensates will redirect intracellular signals and provide a potential way to regulate cellular physiology. Phosphorylation of multiple tyrosine residues of the transmembrane receptor nephrin is known to drive the LLPS of the adaptor protein Nck and neuronal Wiskott-Aldrich Syndrome protein (N-WASP) and form the Nck signaling complex. Phosphorylation of the translocated intimin receptor (Tir) in the host cell may recruit this enteropathogenic Escherichia coli (EPEC) virulence factor to the Nck signaling complex and lead to the entry of EPEC into the intestine cell. In this work, we first identified a phosphotyrosine (pY)-containing peptide 3pY based on the sequence similarity of nephrin and Tir; 3pY promoted the LLPS of Nck and N-WASP, mimicking the role of phosphorylated nephrin. Next, we designed a covalent blocker of Nck, peptide p1 based on the selected pY peptides, which site-selectively reacted with the SH2 domain of Nck (Nck-SH2) at Lys331 through a proximity-induced reaction. The covalent reaction of p1 with Nck blocked the protein binding site of Nck-SH2 and disintegrated the 3pY/Nck/N-WASP condensates. In the presence of membrane-translocating peptide L17E, p1 entered Caco-2 cells in the cytosol, reduced the number of Nck puncta, and rendered Caco-2 cells resistant to EPEC infection. Site-selective covalent blockage of Nck thereby disintegrates intracellular Nck condensates, inhibits actin reorganization, and shuts down the entrance pathway of EPEC. This work showcases the promotion or inhibition of protein phase separation by synthetic peptides and the use of reactive peptides as LLPS disruptors and signal modulators.

Genotypic Determination of Extended Spectrum β-Lactamases and Carbapenemase Production in Clinical Isolates of Klebsiella pneumoniae in Southwest Nigeria

INTRODUCTION

Klebsiella pneumoniae is a major pathogen implicated in healthcare-associated infections. Extended-spectrum β-lactamase (ESBL) and carbapenemase-producing K. pneumoniae isolates are a public health concern. This study investigated the existence of some ESBL and carbapenemase genes among clinical isolates of K. pneumoniae in Southwest Nigeria and additionally determined their circulating clones.

MATERIALS AND METHODS

Various clinical samples from 420 patients from seven tertiary hospitals within Southwestern Nigeria were processed between February 2018 and July 2019. These samples were cultured on blood agar and MacConkey agar, and the isolated bacteria were identified by Microbact GNB 12E. All K. pneumoniae were confirmed by polymerase chain reaction (PCR) using the 16s rRNA gene. Antibiotic susceptibility testing (AST) was done on these isolates, and the PCR was used to evaluate the common ESBL-encoding genes and carbapenem resistance genes. Genotyping was performed using multi-locus sequencing typing (MLST).

RESULTS

The overall prevalence of K. pneumoniae in Southwestern Nigeria was 30.5%. The AST revealed high resistance rates to tetracyclines (67.2%), oxacillin (61.7%), ampicillin (60.2%), ciprofloxacin (58.6%), chloramphenicol (56.3%), and lowest resistance to meropenem (43.0%). All isolates were susceptible to polymyxin B. The most prevalent ESBL gene was the TEM gene (47.7%), followed by CTX-M (43.8%), SHV (39.8%), OXA (27.3%), CTX-M-15 (19.5%), CTX-M-2 (11.1%), and CTX-M-9 (10.9%). Among the carbapenemase genes studied, the VIM gene (43.0%) was most detected, followed by OXA-48 (28.9%), IMP (22.7%), NDM (17.2%), KPC (13.3%), CMY (11.7%), and FOX (9.4%). GIM and SPM genes were not detected. MLST identified six different sequence types (STs) in this study. The most dominant ST was ST307 (50%, 5/10), while ST258, ST11, ST147, ST15, and ST321 had (10%, 1/10) each.

CONCLUSION

High antimicrobial resistance in K. pneumoniae is a clear and present danger for managing infections in Nigeria. Additionally, the dominance of a successful international ST307 clone highlights the importance of ensuring that genomic surveillance remains a priority in the hospital environment in Nigeria.

Covalent Reactive Peptides to Block Protein-Protein Interactions and Inhibit Microbe-Host Interaction

A key step in enteropathogenic Escherichia coli (EPEC) infection of intestinal cells involves a Tir-induced actin reorganization. Nck mediates this event by binding with WIP through its second SH3 domain (Nck-SH3.2). Recently we have developed a preventative antibacterial mechanism that safeguards intestinal cells by shutting down this intracellular signal through a site-selective covalent peptide-protein reaction, a new antibacterial strategy that acts on the host cells instead of bacterium cells. Here we present the experimental details of the design and synthesis of cysteine-reactive peptides to selectively block Nck-SH3.2 but not the other two SH3 domains. Procedures of EPEC infection, covalent reaction inside Caco-2 cells, and bacterial counting to check the antibacterial effect are also described.

Safeguarding intestine cells against enteropathogenic Escherichia coli by intracellular protein reaction, a preventive antibacterial mechanism

A critical problem in the fight against bacterial infection is the rising rates of resistance and the lack of new antibiotics. The discovery of new targets or new antibacterial mechanisms is a potential solution but is becoming more difficult. Here we report an antibacterial mechanism that safeguards intestine cells from enteropathogenic Escherichia coli (EPEC) by shutting down an infection-responsive signal of the host intestine cell. A key step in EPEC infection of intestinal cells involves Tir-induced actin reorganization. Nck mediates this event by binding with Tir through its SH2 domain (Nck-SH2) and with WIP through its second SH3 domain (Nck-SH3.2). Here we report the design of a synthetic peptide that reacts precisely with a unique cysteine of the Nck-SH3.2 domain, blocks the binding site of the Nck protein, and prevents EPEC infection of Caco-2 cells. Oral update of this nontoxic peptide before EPEC administration safeguards mice from EPEC infection and diarrhea. This study demonstrates domain-specific blockage of an SH3 domain of a multidomain adaptor protein inside cells and the inhibition of Tir-induced rearrangement of the host actin cytoskeleton as a previously unknown antibacterial mechanism.

Klebsiella pneumoniae: an increasing threat to public health

OBJECTIVES

This review fills the paucity of information on K. pneumoniae as a nosocomial pathogen by providing pooled data on epidemiological risk factors, resistant trends and profiles and resistant and virulent genes of this organism in Asia.

METHODS

Exhaustive search was conducted using PubMed, Web of Science, and Google scholar for most studies addressing the prevalence, risk factors, drug resistant-mediated genes and/or virulent factors of K. pneumoniae in Asia. Data extracted for meta-analysis were analyzed using comprehensive meta-analysis version 3. Trends data for the isolation rate and resistance rates were entered into Excel spread sheet and the results were presented in graphs.

RESULTS

The prevalence rate of drug resistance in K. pneumoniae were; amikacin (40.8%) [95% CI 31.9-50.4], aztreonam (73.3%) [95% CI 59.9-83.4], ceftazidime (75.7%) [95% CI 65.4-83.6], ciprofloxacin (59.8%) [95% CI 48.6-70.1], colistin (2.9%) [95% CI 1.8-4.4], cefotaxime (79.2%) [95% CI 68.0-87.2], cefepime (72.6) [95% CI 57.7-83.8] and imipenem (65.6%) [95% CI 30.8-89.0]. TEM (39.5%) [95% CI 15.4-70.1], SHV-11 (41.8%) [95% CI 16.2-72.6] and KPC-2 (14.6%) [95% CI 6.0-31.4] were some of the resistance mediated genes observed in this study. The most virulent factors utilized by K. pneumoniae are; hypermucoviscous phenotype and mucoviscosity-related genes, genes for biosynthesis of lipopolysaccharide, iron uptake and transport genes and finally, adhesive genes.

CONCLUSION

It can be concluded that, antimicrobial resistant in K. pneumoniae is a clear and present danger in Asia which needs strong surveillance to curb this menace. It is very important for public healthcare departments to monitor and report changes in antimicrobial-resistant isolates.

Prevalence of extended-spectrum-β-lactamase-producing Enterobacteriaceae: first systematic meta-analysis report from Pakistan

Background

South-Asia is known as a hub for multidrug-resistant (MDR) bacteria. Unfortunately, proper surveillance and documentation of MDR pathogens is lacking in Pakistan. The alarming increase in the prevalence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae is a serious problem. From this perspective, we analysed published data regarding ESBL-producing Enterobacteriaceae in different regions of Pakistan.

Methods

A meta-analysis was performed to determine the prevalence of ESBL-producing Enterobacteriaceae in Pakistan. A Web-based search was conducted in electronic databases, including PubMed, Scopus and PakMedi Net (for non-indexed Pakistani journals). Articles published (in either indexed or non-indexed journals) between January 2002 and July 2016 were included in the study. Relevant data were extracted, and statistical analysis was performed using the Metaprop command of STATA version 14.1.

Results

A total of 68 studies were identified from the electronic data base search, and 55 of these studies met our inclusion criteria. Pakistan’s overall pooled proportion of ESBL-producers was 0.40 (95% CI: 0.34–0.47). The overall heterogeneity was significant (I2 = 99.75%, p < 0.001), and significant ES = 0 (Z = 18.41, p < 0.001) was found. OXA, SHV, TEM and CTX-M were the most commonly found gene variants for ESBLs in these studies.

Conclusion

The prevalence of ESBL-producing Enterobacteriaceae is high in Pakistan. Little is known about the annual frequency of ESBLs and their prevalence in different provinces of Pakistan. No data are available regarding ESBL frequency in Baluchistan. This underscores an urgent demand for regular surveillance to address this antimicrobial resistance problem. Surveillance to better understand the annual ESBL burden is crucial to improve national and regional guidelines.

Epidemiology and susceptibility of pathogens from SMART 2011-12 Turkey: evaluation of hospital-acquired versus community-acquired urinary tract infections and ICU- versus non-ICU-associated intra-abdominal infections

Objectives

To describe the epidemiology and susceptibility of pathogens (including ESBL producers) from hospital-acquired (HA) versus community-acquired (CA) urinary tract infections (UTIs) and ICU- versus non-ICU-associated intra-abdominal infections (IAIs) in Turkey as a part of the SMART study.

Methods

: For this report, Gram-negative pathogens (363 from UTIs and 458 from IAIs) were collected in 2011 and 2012 at six hospitals in Turkey. HA versus CA UTIs and ICU- versus non-ICU-associated IAIs were compared for the species isolated, percentage of ESBL-positive isolates by species and susceptibility for overall and individual Gram-negative species.

Results

: Escherichia coli was the most common pathogen identified in HA (40.2%) and CA (73.9%) UTIs and ICU-associated (25.8%) and non-ICU-associated (43.3%) IAIs. The rate of ESBL-positive E. coli was significantly higher in HA than in CA UTIs (50.5% versus 38.2%, P  <   0.001) and in non-ICU-associated than in ICU-associated IAIs (52.5% versus 29.2%, P  = 0.029). Of the drugs studied, only amikacin was active against ≥90% of pathogens in UTIs, while ertapenem, imipenem and amikacin were active against ≥90% of E. coli ; and imipenem, amikacin and cefoxitin were active against ≥90% of Klebsiella pneumoniae in IAIs.

Conclusions

Our findings demonstrated that E. coli continues to be the principal pathogen of UTIs and IAIs in Turkey. Along with a high rate of ESBL-positive isolates, high antimicrobial resistance among Gram-negative bacilli from either UTIs or IAIs was noted particularly in the case of HA UTIs and ICU-associated IAIs, with a higher likelihood of carbapenem- or amikacin-based therapy to provide the broadest activity against bacterial pathogens.

Trends and relationship between antimicrobial resistance and antibiotic use in Xinjiang Uyghur Autonomous Region, China: Based on a 3 year surveillance data, 2014-2016

PURPOSES

The objective of the study was to identify the trends and relations between antimicrobial resistance (AMR) and antibiotic use in the Xinjiang Uyghur Autonomous Region in Western China from 2014 to 2016.

METHODS

A retrospective, descriptive analysis of AMR prevalence, and trends and relations between AMR and antibiotic use during the 3-year period was performed.

RESULTS

Third-generation cephalosporin-resistant Escherichia coli was the most prevalent resistant pathogen in terms of both resistance density and resistance proportion. A significant correlation was found between resistance density of third-generation cephalosporin-resistant Klebsiella pneumoniae and the use of beta-lactam-beta-lactamase inhibitor combinations (cc=0.63, p=0.03), quinolones (cc=0.60, p=0.04), and carbapenems (cc=0.76, p=0.004), among which only beta-lactam-beta-lactamase inhibitor combinations showed a significant correlation with third-generation cephalosporin-resistant E. coli (cc=0.63, p=0.03). For carbapenem-resistant Pseudomonas aeruginosa, not only carbapenem use (cc=0.65, p=0.02) but also penicillin (cc=0.76, p=0.004) and quinolone (cc=0.69, p=0.01) use showed significant correlation. A strong correlation was observed between the resistant proportion of third-generation cephalosporin-resistant E. coli and only the use of beta-lactam-beta-lactamase inhibitor combinations (cc=0.61, p=0.03).

CONCLUSION

The association between antibiotic use and AMR, especially the implication of the difference in resistance density and resistance proportion, is crucial for local physicians and decision-makers to better use of antibiotics and allocate healthcare resources more effectively, as well as to better implement antimicrobial stewardship and effective infection control strategies.

Pathogen Prevalence and Antimicrobial Susceptibility Among Enterobacteriaceae Causing Hospital-associated Intra-abdominal Infections in Adults in the United States (2012-2013)

PURPOSE

Selection and prompt initiation of the appropriate empiric antimicrobial therapy are critical to decrease morbidity and mortality and shorten the length of hospitalization among patients with hospital-associated intra-abdominal infections (HA-IAIs). Therapeutic choices for the treatment of patients with HA-IAI require careful consideration. This study was conducted to evaluate the antimicrobial susceptibility of common pathogens collected from adult patients with HA-IAI in the United States.

METHODS

Gram-negative bacilli (N = 1285) were collected during 2012-2013 from SMART (Study for Monitoring Antimicrobial Resistance Trends). Isolates were tested at a central laboratory by using Clinical and Laboratory Standards Institute methods and interpretation of susceptibility to 12 antimicrobial agents.

FINDINGS

Most of the isolates (80.8%) were Enterobacteriaceae, and Escherichia coli was the most common species. Susceptibility to frequently used antimicrobial agents for treating IAI showed that ertapenem, imipenem, and amikacin were more active than other agents against Enterobacteriaceae, including multidrug-resistant isolates. More than 92% of E coli, including extended-spectrum β-lactamase (ESBL) producers, and Klebsiella pneumoniae isolates were susceptible to ertapenem, imipenem, and amikacin. Cefepime was the most active (>90% susceptibility) cephalosporin against all species except K pneumoniae (86.6%) but with much reduced activity against isolates with ESBLs. Piperacillin/tazobactam had reduced activity against Enterobacter species (70.4%-76.4% susceptible) and ESBL-producing K pneumoniae (22.5% susceptible). Fluoroquinolones exhibited poor activity against E coli (overall susceptibility <70%).

IMPLICATIONS

Proper empiric antimicrobial treatment, including combining appropriate agents, of HA-IAI requires detailed understanding of the epidemiology of common pathogens and antimicrobial resistance patterns. In light of rising rates of antimicrobial resistance, ongoing surveillance is critical for clinical decision-making.

Resistance Rates of Intra-Abdominal Isolates from Intensive Care Units and Non-Intensive Care Units in the United States: The Study for Monitoring Antimicrobial Resistance Trends 2010-2012

BACKGROUND

Enterobacteriaceae (3,235 isolates), Pseudomonas aeruginosa (476 isolates), and Acinetobacter baumannii (106 isolates) from inpatient intra-abdominal infections (IAIs) were collected for the 2010-2012 Study for Monitoring Antimicrobial Resistance Trends (SMART) program in the United States. This report evaluates the in vitro activity of several antimicrobial agents recommended for treatment of IAIs and compares profiles of isolates from intensive care units (ICUs) and non-intensive care units (non-ICUs).

METHODS

Gram-negative bacilli from hospitalized patients with IAIs were obtained each year from 2010-2012 from hospitals in the United States and tested for susceptibility to 12 antibiotics according to 2012 Clinical and Laboratory Standards Institute (CLSI) guidelines.

RESULTS

The most active agents against members of the Enterobacteriaceae family from both ICUs and non-ICUs were amikacin, ertapenem, and imipenem-cilastatin, whereas the least active agent was ampicillin-sulbactam. Amikacin was the only agent with good activity against P. aeruginosa, whereas none of the agents tested exhibited substantial activity against A. baumannii. Amikacin, ceftazidime, ceftriaxone, ciprofloxacin, levofloxacin, and imipenem-cilastatin were significantly less active against Enterobacteriaceae from ICU patients, whereas cefepime and ceftazidime were significantly less active against P. aeruginosa from ICU patients. Intensive care unit isolates were more likely to be multi-drug-resistant than non-ICU isolates, although there was no difference in extended-spectrum β-lactamase (ESBL) production rates between the two patient groups.

CONCLUSIONS

Despite increasing resistance trends, in this study amikacin, ertapenem, and imipenem-cilastatin were shown to have good in vitro activity against the most frequently isolated gram-negative bacilli from IAIs in ICU and non-ICU settings.

Clinical management of infections caused by multidrug-resistant Enterobacteriaceae

Enterobacteriaceae showing resistance to cephalosporins due to extended-spectrum β-lactamases (ESBLs) or plasmid-mediated AmpC enzymes, and those producing carbapenemases have spread worldwide during the last decades. Many of these isolates are also resistant to other first-line agents such as fluoroquinolones or aminoglycosides, leaving few available options for therapy. Thus, older drugs such as colistin and fosfomycin are being increasingly used. Infections caused by these bacteria are associated with increased morbidity and mortality compared with those caused by their susceptible counterparts. Most of the evidence supporting the present recommendations is from in vitro data, animal studies, and observational studies. While carbapenems are considered the drugs of choice for ESBL and AmpC producers, recent data suggest that certain alternatives may be suitable for some types of infections. Combined therapy seems superior to monotherapy in the treatment of invasive infections caused by carbapenemase-producing Enterobacteriaceae. Optimization of dosage according to pharmacokinetics/pharmacodynamics data is important for the treatment of infections caused by isolates with borderline minimum inhibitory concentration due to low-level resistance mechanisms. The increasing frequency and the rapid spread of multidrug resistance among the Enterobacteriaceae is a true and complex public health problem.

Predictors of hospital surface contamination with Extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae: patient and organism factors

Background

The role of the hospital environment in transmission of ESBL-Klebsiella pneumoniae (ESBL-KP) and ESBL-Escherichia coli (ESBL-EC) is poorly defined. Recent data however suggest that in the hospital setting, ESBL-KP is more transmissible than ESBL-EC. We sought therefore to measure the difference in hospital contamination rates between the two species and to identify key risk factors for contamination of the hospital environment with these organisms.

Methods

We systematically sampled 8 surfaces in the rooms and bathrooms of adult patients colonized or infected with ESBL-EC or ESBL-KP throughout their hospital stay. Data were collected on factors potentially affecting contamination rates. Environmental contamination was defined as recovery of an ESBL-producing organism matching the source patient’s isolate. Multivariate logistic regression analysis was performed at the level of the patient visit using generalized estimating equations to identify independent predictors of environmental contamination.

Results

24 patients (11 with ESBL-KP, 11 ESBL-EC and 2 with both organisms) had 1104 swabs collected during 138 visits. The overall contamination rate was 3.4% (38/1104) and was significantly higher for ESBL-KP than ESBL-EC (5.4% versus 0.4%; p < 0.0001). After multivariate analysis, environmental contamination was found to be negatively associated with carbapenem exposure (OR 0.06 [95% CI 0.01-0.61]; p = 0.017) and positively associated with the presence of an indwelling urinary catheter (OR 6.12 [95% CI 1.23-30.37]; p = 0.027) and ESBL-KP in the source patient (OR 26.23 [95% CI 2.70-254.67]; p = 0.005).

Conclusions

Contamination of the hospital environment with ESBL-producing Enterobacteriaceae (ESBL-E) is inversely associated with carbapenem exposure. Predictors of hospital contamination with ESBL-E include: indwelling urinary catheters and ESBL-KP. Rooms of patients with ESBL-KP have substantially higher contamination rates than those with ESBL-EC. This finding may help explain the apparently higher transmissibility of ESBL-KP in the hospital setting.

Multiresistant uropathogenic extended-spectrum β-lactamase (ESBL)-producing Escherichia coli are susceptible to the carbon monoxide releasing molecule-2 (CORM-2)

Carbon monoxide (CO) releasing molecules (CO-RMs) have been shown to inhibit growth of commensal Escherichia coli (E. coli). In the present study we examined the effect of CORM-2 on uropathogenic E. coli (UPEC) that produces extended-spectrum β-lactamase (ESBL). Viability experiments showed that CORM-2 inhibited the growth of several different ESBL-producing UPEC isolates and that 500 μM CORM-2 had a bactericidal effect within 4 h. The bactericidal effect of CORM-2 was significantly more pronounced than the effect of the antibiotic nitrofurantoin. CORM-2 demonstrated a low level of cytotoxicity in eukaryotic cells (human bladder epithelial cell line 5637) at the concentrations and time-points where the antibacterial effect was obtained. Real-time RT-PCR studies of different virulence genes showed that the expression of capsule group II kpsMT II and serum resistance traT was reduced and that some genes encoding iron acquisition systems were altered by CORM-2. Our results demonstrate that CORM-2 has a fast bactericidal effect against multiresistant ESBL-producing UPEC isolates, and also identify some putative UPEC virulence factors as targets for CORM-2. CO-RMs may be candidate drugs for further studies in the field of finding new therapeutic approaches for treatment of uropathogenic ESBLproducing E. coli.

A 10 year surveillance for antimicrobial susceptibility of Escherichia coli and Klebsiella pneumoniae in community- and hospital-associated intra-abdominal infections in China

The objective of this study was to investigate the susceptibility of hospital-associated (HA) and community-associated (CA) Escherichia coli and Klebsiella pneumoniae isolated from patients with intra-abdominal infections (IAIs) in China. From 2002 to 2011, the minimum inhibitory concentrations (MICs) of 12 antibiotics against 3074 E. coli and 1025 K. pneumoniae from 23 centres located in 16 cities were determined by the broth microdilution method. During the 10 year study period, ertapenem, imipenem, amikacin and piperacillin-tazobactam retained high and stable activity against E. coli and K. pneumoniae isolates regardless of whether their source was HA or CA and regardless of their extended-spectrum beta-lactamase (ESBL) production. However, the susceptibility of E. coli to cephalosporins and ampicillin-sulbactam decreased dramatically during the 10 years, especially for the CA isolates. Fluoroquinolones showed low activity against E. coli. During the whole study period, the ESBL rates for E. coli isolates from IAIs increased from 36.1 % in 2002–2003 to 68.1 % in 2010–2011 (P<0.001). Correspondingly, the ESBL rates in HA isolates increased from 52.2 % in 2002–2003 to 70.0 % in 2010–2011 (P = 0.001), and in CA isolates from 19.1 % in 2002–2003 to 61.6 % in 2010–2011 (P<0.001). The ESBL-positive rate in K. pneumoniae remained between 30.1 and 39.3 % of the total isolates with no significant change during the 10 years. In conclusion, carbapenems retained the highest susceptibility rates against HA and CA E. coli and K. pneumoniae. High prevalence of ESBL in HA E. coli and fast-growing resistance in CA E. coli severely limit the empirical use of the third- and fourth-generation cephalosporins in the therapy of IAIs.

Etiology, extended-spectrum β-lactamase rates and antimicrobial susceptibility of gram-negative bacilli causing intra-abdominal infections in patients in general pediatric and pediatric intensive care units--global data from the Study for Monitoring Antimicrobial Resistance Trends 2008 to 2010

BACKGROUND

Antimicrobial resistance has been increasing for several years and is often higher in intensive care units (ICUs) than in other facilities. The spread of extended-spectrum β-lactamases (ESBLs) in particular has profoundly impacted antimicrobial efficacy and usage. The Study for Monitoring Antimicrobial Resistance Trends has monitored the in vitro activity of ertapenem and several comparators against aerobic gram-negative bacteria from intra-abdominal infections (IAIs) for many years. This report summarizes susceptibility levels and epidemiology for key IAI pathogens cultured from general pediatric medical wards and pediatric ICUs globally.

METHODS

1248 gram-negative bacteria were collected from pediatric IAIs by 113 labs in 40 countries from 2008 to 2010. Susceptibility was determined by Clinical and Laboratory Standards Institute broth microdilution. Susceptibility rates (%S) were determined for species with ≥10 isolates.

RESULTS

Sixty-two percent of isolates came from general pediatric wards and 38% from pediatric ICUs. The overall ESBL-positive rate was 11.0% for Escherichia coli and 38.9% for Klebsiella pneumoniae; the ESBL-positive rate for E. coli was twice as high in ICU as non-ICU. Most study drugs inhibited >90% of ESBL-negative isolates, but only the carbapenems inhibited >90% of ESBL-positive E. coli and only imipenem inhibited >90% of ESBL-positive K. pneumoniae.

CONCLUSIONS

Amikacin, imipenem and ertapenem were the most active against gram-negative bacteria from pediatric IAIs, followed closely by the fluoroquinolones and cefepime. Other cephalosporins were often <90% active. ESBL rates were 38.9% for K. pneumoniae and 11.0% for E. coli. Therapy for pediatric IAIs should take into consideration local ESBL rates because only carbapenems inhibited most of these pathogens.

Efficacy of doripenem and ertapenem against KPC-2-producing and non-KPC-producing Klebsiella pneumoniae with similar MICs

OBJECTIVES

In the clinical setting, the choice of definitive drug therapy is typically guided by the antimicrobial susceptibility profile of the infecting organism. We evaluated the activity of doripenem and ertapenem against Klebsiella pneumoniae isolates with similar MICs that exhibited KPC-based and non-KPC-based genotypes.

METHODS

Five doripenem-non-susceptible K. pneumoniae isolates, three producing KPC carbapenemases and two exhibiting porin modifications plus AmpC β-lactamase production, were tested in a neutropenic murine thigh infection model. The ertapenem MIC for all isolates was >32 mg/L. Regimens of 2 g of doripenem every 8 h (4 h infusion) and 1 g of ertapenem every 24 h (0.5 h infusion) simulating human concentration-time profiles were administered 2 h after inoculation. The change in bacterial density was evaluated after 24 h of therapy.

RESULTS

Consistent with the observed MICs, treatment with ertapenem resulted in minimal activity against all isolates tested. When comparing the activity of doripenem between the KPC and non-KPC producers with doripenem MICs of 8 mg/L, significantly better activity was noted for the non-KPC producer (P<0.001). Likewise, when comparing the two KPC-producing isolates with doripenem MICs of 24 mg/L and >32 mg/L with the non-KPC producer with an MIC of 32 mg/L, significantly greater activity was noted for the non-KPC producer (P<0.001).

CONCLUSIONS

When doripenem MICs were similar, activity was greater for non-KPC-producing isolates when compared with KPC producers. While the in vitro MIC is typically the sole method utilized to aid in drug selection, these data suggest that the genetic driver behind these MICs may also play a role in predicting in vivo activity.

Antimicrobial susceptibility of Enterobacteriaceae, including molecular characterization of extended-spectrum beta-lactamase-producing species, in urinary tract isolates from hospitalized patients in North America and Europe: results from the SMART study 2009-2010

In 2009-2010, 3646 urinary tract isolates of Enterobacteriaceae spp. were isolated from hospitalized patients in North America and Europe. Extended-spectrum beta-lactamase (ESBL) production was detected in 8.5% and 8.8% of Escherichia coli and Klebsiella pneumoniae, respectively, in North America and in 17.6% and 38.9% for Europe, respectively. The carbapenems (ertapenem and imipenem) were the most active agents in vitro, with ampicillin-sulbactam the least active. Molecular characterization of about 50% of ESBL-positive isolates identified the presence of bla(CTX-M) genes in over 90% of Escherichia coli from both continents. bla(KPC) was more common in North American isolates of K. pneumoniae than in European isolates (21.4% versus 6.9%). bla(TEM) and AmpC genes were infrequent. Enterobacteriaceae spp. isolated from hospitalized patients with urinary tract infections in both North America and Europe are often resistant to commonly used antimicrobials with bla(CTX-M) genes common in both Escherichia coli and K. pneumoniae.

Decreased susceptibility to noncarbapenem antimicrobials in extended-spectrum-β-lactamase-producing Escherichia coli and Klebsiella pneumoniae isolates in Toronto, Canada

Retrospective review from 11 Canadian hospitals showed increasing incidence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae from 0.12 per 1,000 inpatient days during 2005 to 0.47 per 1,000 inpatient days during 2009. By 2009, susceptibility rates of ESBL-positive E. coli/K. pneumoniae were as follows: ciprofloxacin, 12.8%/9.0%; TMP/SMX, 32.9%/12.2%; and nitrofurantoin, 83.8%/10.3%. Nosocomial and nonnosocomial ESBL-producing E. coli isolates had similar susceptibility profiles, while nonnosocomial ESBL-producing K. pneumoniae was associated with decreased ciprofloxacin (P = 0.03) and nitrofurantoin (P < 0.001) susceptibilities.

A ten years (2000-2009) surveillance of resistant Enterobacteriaceae in Zhejiang Province, China

OBJECTIVE

In Zhejiang Province, there are several highly developed cities near the coast and several relatively under-developed mountain areas. Analysis of the composition of bacteria isolated from patients as well as their antibiotic resistance profile from various areas of this province, and tracing of such data year-by-year, will help to delineate the bacterial resistance profile of these areas and to understand how the stage of socio-economical development impacts on the composition of clinical micro-flora and their resistance profile.

METHODS

In order to investigate variation in resistance rates and isolation rates of Enterobacteriaceae, from 2000 to 2009 in Zhejiang Province, China, Enterobacteriaceae isolated from 15 hospitals located in different regions of the province were surveyed.

RESULTS

The total numbers of the Enterobacteriaceae isolated increased more than 20-fold from 2000 to 2009. Among the Enterobacteriaceae, Escherichia coli and Klebsiella pneumoniae were the dominant isolates. The percentage of E. coli and K. pneumoniae that produced detectable extended-spectrum β-lactamases (ESBLs) increased from 2000 to 2007, and then declined slightly in 2008 and 2009. The percentages of K. pneumoniae and E. coli that were resistant to ceftazidime increased sharply from 2000 to 2009. There were remarkable increases in the carbapenem resistant rates during the decade, but they were much higher for the isolates from the developed cities than from the rural areas. In 2002, carbapenem-resistant E. coli was first found in Hangzhou, one of the highly developed cities in Zhejiang Province. By 2009, carbapenem-resistant bacteria were found for all species of Enterobacteriaceae surveyed in almost all areas of the province, although they were more frequently identified in developed areas than in rural areas.

CONCLUSION

Much restrictive actions have to be taken in terms of rational use of antibiotics and nosocomial control to prevent the further spread of the drug-resistant pathogens.

Antimicrobial susceptibility of gram-negative pathogens isolated from patients with complicated intra-abdominal infections in South African hospitals (SMART Study 2004-2009): impact of the new carbapenem breakpoints

BACKGROUND

The Study for Monitoring Antimicrobial Resistance Trends (SMART) follows trends in resistance among aerobic and facultative anaerobic gram-negative bacilli (GNB) isolated from complicated intra-abdominal infections (cIAIs) in patients around the world.

METHODS

During 2004-2009, three centralized clinical microbiology laboratories serving 59 private hospitals in three large South African cities collected 1,218 GNB from complicated intra-abdominal infections (cIAIs) and tested them for susceptibility to 12 antibiotics according to the 2011 Clinical Laboratory Standards Institute (CLSI) guidelines.

RESULTS

Enterobacteriaceae comprised 83.7% of the isolates. Escherichia coli was the species isolated most commonly (46.4%), and 7.6% of these were extended-spectrum β-lactamase (ESBL)-positive. The highest ESBL rate was documented for Klebsiella pneumoniae (41.2%). Overall, ertapenem was the antibiotic most active against susceptible species for which it has breakpoints (94.6%) followed by amikacin (91.9%), piperacillin-tazobactam (89.3%), and imipenem-cilastatin (87.1%), whereas rates of resistance to ceftriaxone, cefotaxime, ciprofloxacin, and levofloxacin were documented to be 29.7%, 28.7%, 22.5%, and 21.1%, respectively. Multi-drug resistance (MDR), defined as resistance to three or more antibiotic classes, was significantly more common in K. pneumoniae (27.9%) than in E. coli (4.9%; p<0.0001) or Proteus mirabilis (4.1%; p<0.05). Applying the new CLSI breakpoints for carbapenems, susceptibility to ertapenem was reduced significantly in ESBL-positive E. coli compared with ESBL-negative isolates (91% vs. 98%; p<0.05), but this did not apply to imipenem-cilastatin (95% vs. 99%; p=0.0928). A large disparity between imipenem-cilastatin and ertapenem susceptibility in P. mirabilis and Morganella morganii was documented (24% vs. 96% and 15% vs. 92%, respectively), as most isolates of these two species had imipenem-cilastatin minimum inhibitory concentrations in the 2-4 mcg/mL range, which is no longer regarded as susceptible.

CONCLUSIONS

This study documented substantial resistance to standard antimicrobial therapy among GNB commonly isolated from cIAIs in South Africa. With the application of the new CLSI carbapenem breakpoints, discrepancies were noted between ertapenem and imipenem-cilastatin with regard to the changes in their individual susceptibilities. Longitudinal surveillance of susceptibility patterns is useful to guide recommendations for empiric antibiotic use in cIAIs.

Surveillance programmes and antibiotic resistance: worldwide and regional monitoring of antibiotic resistance trends

Since the introduction of the penicillins many decades ago, multiple species of bacteria have responded to the use of antimicrobial agents in their ability to develop and transmit antimicrobial resistance. Increased consumption of antimicrobial agents, their misappropriate use among other factors have further catalysed this resistance phenomenon. As bacterial resistance is a global healthcare issue, appropriate monitoring through governmental, institutional and industry or pharmaceutical led surveillance programmes is essential. This chapter describes the resistance issue, factors affecting this issue and examples of such ongoing resistance surveillance programmes.

Phenotypic changes in a laboratory-derived ertapenem-resistant Escherichia coli strain

The aim of this study was to identify phenotypic changes in a laboratory-derived strain of ertapenem-resistant Escherichia coli (Ec-ERT) when compared to its susceptible parent strain (Ec-WT). In both strains, we assessed both the effects of ertapenem via time-kill curves and the occurrence of cross resistance with other beta-lactams. The strains were compared based on growth pattern, biochemical-physiological profile and changes in the subproteome using 2D-DIGE followed by MALDI-TOF/TOF MS. To assess virulence, we employed a murine model of intraperitoneal infection in which we investigated the invasiveness of both strains. Growth persistence of the laboratory-derived resistant strain was observed via the time-kill curve assay, but cross resistance was not observed for other beta-lactams. We also observed a slower growth rate and changes in the biochemical and physiological characteristics of the drug-resistant bacteria. In the resistant strain, a total of 51 protein spots were increased in abundance relative to the wild-type strain, including an outer membrane protein A, which is related to bacterial virulence. The mouse infection assay showed a higher invasiveness of the Ec-ERT strain in relation to the Ec-WT strain. In conclusion, the alterations driven by ertapenem in E. coli reinforce the idea that antimicrobial agents may interfere in several aspects of bacterial cell biology, with possible implications for host-bacteria interactions.

Antimicrobial susceptibility of global inpatient urinary tract isolates of Escherichia coli: results from the Study for Monitoring Antimicrobial Resistance Trends (SMART) program: 2009-2010

Escherichia coli is the most important uropathogen. The Study for Monitoring Antimicrobial Resistance Trends program collected 1643 E. coli isolates in 2009-2010 from urinary tract infection (UTI) specimens of hospitalized patients in countries worldwide. Ertapenem and imipenem were the most active agents tested, inhibiting >98% of all E. coli phenotypes. Overall, 17.9% of isolates were extended-spectrum beta-lactamase (ESBL) producers. The highest ESBL rate was from the Asia/Pacific region (27.7%). Amikacin and piperacillin-tazobactam achieved 90% inhibition levels only for ESBL-negative isolates. Ciprofloxacin and levofloxacin were not effective for ESBL-positive isolates, with only 14.6% and 15.9% susceptible, respectively. These observations highlight the need for continued monitoring of susceptibility of E. coli isolated from hospitalized patients with UTIs.

Determination of a new antibacterial peptide S-thanatin in rat plasma by an indirected-ELISA

In this study, antimicrobial peptide S-thanatin (Ts) was chemically synthesized and linked to keyhole limpet hemocyanin (KLH) and bovine serum albumin (BSA) by carbodiimide reagent. Rabbits were immunized with Ts-KLH and polyclonal antibody against Ts was purified by fractional precipitation of ammonium sulfate, coupled with anion-exchange chromatography. The purified antibody specifically binding to Ts residues but not BSA molecules was observed by Western-Blot analysis. Ts-BSA was selected as immobilized antigen and reacted with the residual antibody after the excess of anti-Ts antibody was combined with Ts in the sample. The binding antibody was recognized by HRP-conjugated secondary antibody. Finally, the horseradish peroxidase in the complex could catalyze the TMB substrate, resulting in color development. The method was evaluated by analysis of linearity, precision and accuracy and successfully applied in determination of Ts in rat plasma. The data of the pharmacokinetic parameters were also obtained. The proposed ELISA has a great value in routine analysis of Ts for its therapeutic monitoring and pharmacokinetic studies.

Evaluation of updated interpretative criteria for categorizing Klebsiella pneumoniae with reduced carbapenem susceptibility

We studied the accuracy of various susceptibility testing methods, including the 2009, 2010, and updated 2010 CLSI recommendations, to identify Klebsiella pneumoniae isolates with reduced susceptibility to carbapenems associated with different mechanisms of resistance. Forty-three wild-type (WT) strains, 42 extended-spectrum β-lactamase (ESBL) producers, 18 ESBL producers with outer membrane porin protein loss (ESBL/Omp strains), and 42 blaKPC-possessing K. pneumoniae (KPC-Kp) isolates were evaluated. Imipenem (IPM), meropenem (MEM), ertapenem (ERT), and doripenem (DOR) were tested by broth microdilution (BMD), Etest, and disk diffusion (DD), and the modified Hodge test (MHT) was performed using IPM and MEM disks. Results were interpreted according to original as well as recently updated interpretative criteria. MHT was positive for all 42 KPC-Kp isolates and 10 of 18 ESBL/Omp strains and therefore had poor specificity in differentiating between KPC-Kp and ESBL/Omp isolates. Based on the updated CLSI standards, phenotypic susceptibility testing by BMD and DD differentiated most carbapenem-susceptible from carbapenem-nonsusceptible K. pneumoniae isolates without the need for MHT, while the Etest method characterized many KPC-Kp isolates as susceptible, and breakpoints may need to be lowered for this method. However, both the original and updated CLSI criteria do not adequately differentiate between isolates in the KPC-Kp group, which are unlikely to respond to carbapenem therapy, and those in the ESBL/Omp group, which are likely to respond to carbapenem therapy if MICs are within pharmacokinetic/pharmacodynamic targets. Further studies are required to determine if there is a clinical need to differentiate between KPC-Kp and ESBL/Omp groups.

Susceptibility of gram-negative pathogens isolated from patients with complicated intra-abdominal infections in the United States, 2007-2008: results of the Study for Monitoring Antimicrobial Resistance Trends (SMART)

During 2007-2008, 1,036 gram-negative bacilli were isolated from patients with complicated intra-abdominal infections in the United States. Against members of the family Enterobacteriaceae, the most active agents in vitro were ertapenem, imipenem, and amikacin, while the least active agent was ampicillin-sulbactam. Ertapenem and imipenem were active against all extended-spectrum-beta-lactamase (ESBL)-positive Escherichia coli. Antimicrobial resistance in gram-negative bacilli isolated from patients with complicated intra-abdominal infections in the United States continues to increase.