Evaluation of the NCCLS extended-spectrum beta-lactamase confirmation methods for Escherichia coli with isolates collected during Project ICARE

Short Antibiotic Treatment Duration for Osteomyelitis Complicating Pressure Ulcers: A Quasi-experimental Study

Background

Osteomyelitis-complicating pressure ulcers are frequent among patients with spinal cord injuries (SCIs), and the optimal management is unknown. In our referral center, the current management is debridement and flap coverage surgeries, followed by a short antibiotic treatment. We aimed to evaluate patients' outcomes a year after surgery.

Methods

We performed a quasi-experimental retrospective before/after study on SCI patients with presumed osteomyelitis associated with perineal pressure ulcers. We included all patients who underwent surgery with debridement and flap covering, followed by effective antibiotic treatment, between May 1, 2016, and October 30, 2020. The effective antimicrobial treatment duration included the 10 days leading up to January 1, 2018 (before period), and the 5 to 7 days after (after period). We also compared the efficacy of 5-7-day vs 10-day antibiotic treatment and performed uni- and multivariable analyses to identify factors associated with failure.

Results

Overall, 415 patients were included (77.6% male patients; mean age ± SD, 53.0 ± 14.4 years). Multidrug-resistant organisms (MDROs) were involved in 20.7% of cases. Favorable outcomes were recorded in 69.2% of cases: 117/179 (65.3%) in the 10-day treatment group vs 169/287 (71.9%) in the 5-7-day treatment group (P = .153). The only factor associated with failure in the multivariate analysis was a positive culture from suction drainage (odds ratio, 1.622; 95% CI, 1.005-2.617; P = .046). Effective treatment duration >7 days and intraoperative samples negative for MDROs were not associated with better outcomes (P = .153 and P = .241, respectively).

Conclusions

A treatment strategy combining surgical debridement and flap covering, followed by 5 to 7 days of effective antibiotic treatment seems safe.

Hip joint infections caused by multidrug-resistant Enterobacterales among patients with spinal cord injury: experience of a reference center in the Greater Paris area

Introduction

We aimed to describe the management and treatment of hip joint infections caused by multidrug-resistant Enterobacterales among patients with spinal cord injury (SCI).

Methods

We included all hip joint infections associated with grade IV decubitus ulcers caused by Extended-Spectrum Beta-Lactamase producing Enterobacterales (ESBL-PE) and Carbapenemase-Producing Enterobacterales (CPE) treated in a reference center for bone and joint infections (BJIs) over 9 years in a retrospective study.

Results

Seventeen SCI patients with ischial pressure ulcers breaching the hip capsule (mean age 52 ± 15 years) were analyzed. In 16 patients, paraplegia was secondary to trauma and one was secondary to multiple sclerosis. Infections were mostly polymicrobial (n=15; 88.2%), notably caused by Klebsiella pneumoniae (n=10) and S. aureus (n=10). The carbapenemases identified were exclusively OXA-48-type (n=3) including 2 isolates co-expressed with ESBL-PE within the same bacterial host.

Multidrug-resistant Enterobacterales were commonly resistant to fluoroquinolones (n=12; 70.6%). Most therapies were based on carbapenems (n=10) and combination therapies (n=13). Median duration of treatment was 45 (6-60) days. Of 17 cases of hip joint infections, 94.1% (n=16) benefited from a femoral head and neck resection.

Infection control was initially achieved in 58.8% (n=10) of cases and up to 88.2% after revision surgeries, after a median follow-up of 3 (1-36) months.

Conclusion

Hip infections among SCI patients caused by multidrug-resistant Enterobacterales are often polymicrobial and fluoroquinolones-resistant infections caused by K. pneumoniae and S. aureus, highlighting the need for expert centers with pluridisciplinary meetings associating experienced surgeons, clinical microbiologists and infectious disease specialists.

Native bone and joint infections caused by extended-spectrum β-lactamase-producing Enterobacterales: experience of a reference centre in the Greater Paris area

Antibiotic treatment of native osteomyelitis caused by extended-spectrum β-lactamase-producing Enterobacterales (ESBL-PE) is a challenge. Limited epidemiological and outcome data are available. This retrospective cohort study included osteomyelitis patients with ESBL-PE infections treated in a reference centre for bone and joint infections (BJIs) between 2011-2019. Twenty-nine patients with native BJI (mean age, 44.4 ± 15.7 years) were analysed. Fifteen cases were paraplegic patients with ischial pressure sores breaching the hip capsule. Other cases included eight other hip infections, four tibial infections and two foot infections. Infections were mostly polymicrobial (n = 23; 79.3%), including Staphylococcus aureus (n = 13; 8 methicillin-resistant). Klebsiella pneumoniae (n = 13) was the most frequent ESBL-producing species identified, followed by Escherichia coli (n = 10), including 3 E. coli/K. pneumoniae co-infections, and Enterobacter spp. (n = 9). ESBL-PE were rarely susceptible to fluoroquinolones (n = 4; 13.8%). Most therapies were based on carbapenems (n = 22) and combination therapies (n = 19). The median duration of treatment was 41 (5-60) days. Primary control of the infection was achieved in 62.1% (18/29) of cases and up to 86.2% after second look surgeries, after a median follow-up of 6 (1-36) months. Infection with ESBL-producing K. pneumoniae was associated with failure (P = 0.001), whereas age, infection location, prior colonisation and antimicrobial therapy were not found to be predictors of outcome. ESBL-PE native BJIs are often polymicrobial and fluoroquinolone-resistant infections caused by K. pneumoniae, highlighting the need for expert centres with pluridisciplinary meetings with experienced surgeons.

Molecular Characterization of Antibiotic Resistance Associated with TEM and CTX-M ESBL in Uropathogenic E. coli Strains Isolated from Outpatients

Background & Objective

Escherichia coli (E. coli) is a leading cause of urinary tract infections becoming resistant against beta-lactams and cephalosporins through different mechanisms, including ESBL production due to the presence of ESBL specific genes, including blaCTX-M and blaTEM. The purpose of the present study was to detect the uropathogenic E. coli strains producing the ESBL.

Methods

A total of 100 isolates of uropathogenic E. coli were randomly selected in a period of 6 months and their resistances to a number of antibiotics including amoxicillin, amikacin, gentamicin, ciprofloxacin, ceftazidime, cefotaxime, ceftriaxone, ceftizoxime, nalidixic acid, and nitrofurantoin were determined. Then, DDT test was used to detect the presence of ESBL. Finally, the presence of blaCTX-M and blaTEM resistance genes was analyzed by PCR method.

Results

The resistance profile of bacterial isolates to the antibiotics was as follows: amoxicillin: 16.7%, amikacin: 7.8%, gentamicin: 20.3%, ciprofloxacin: 35.5/%, ceftazidime: 35.0%, cefotaxime: 40.0%, ceftriaxone: 41.3%, nalidixic acid: 64.0%, nitrofurantoin: 9.7%, and ceftizoxime: 100%. Of these, 28 isolates (28%) were reported to be resistant to cefotaxime, ceftazidime, and ceftriaxone. In DDT test, 21 ESBL positive cases (21%) were detected. PCR results showed that the presence of blaCTX-M and blaTEM genes in the isolates were 21% and 20%, respectively.

Conclusion

Regarding the production of ESBL by some E. coli isolates, phenotypic detection of ESBL-producing isolates is routinely suggested in the laboratories. Likewise, the treatment regimen should be selected regarding the ESBL production to avoid treatment failure.

Treatment of bone and joint infections by ceftazidime/avibactam and ceftolozane/tazobactam: a cohort study

OBJECTIVES

Ceftazidime/avibactam (C/A) and ceftolozane/tazobactam (C/T) are two novel antibacterials with known efficacy against Gram-negative bacteria (GNB). We aimed to describe the efficacy and safety of surgical management combined with C/A or C/T treatment for bone and joint infections (BJIs).

METHODS

We conducted an observational, bicentric study of patients treated with C/A or C/T for a BJI between May 2016 and June 2019. Failure was defined as the need for unplanned additional antibiotic treatment or orthopaedic surgery, or death due to the BJI up to the patient's latest visit.

RESULTS

Overall, 15 patients were included. Nine patients were treated with C/A, mainly for polymicrobial BJI due to multidrug-resistant (MDR) bacteria (Enterobacteriaceae, n = 7). Six patients were male, the median age was 66 years and the median Charlson comorbidity index (CCI) was 5. It was the first septic episode at the site in 3/9 patients. The cure rate was 7/9 (median follow-up, 272 days). Two patients showed C/A-related confusion. Five patients were treated with C/T for BJI involving MDR Pseudomonas aeruginosa. Four patients were male, the median age was 53 years and the median CCI was 2. All patients had previous septic episodes at the infection site. The cure rate was 3/5 (median follow-up, 350 days). One patient was successfully treated by C/T then C/A for multistage spondylodiscitis.

CONCLUSION

In our experience, C/A and C/T are two effective and safe options, even as salvage treatment for BJI due to MDR-GNB despite the absence of label, however more data are warranted.

The Frequency and Antimicrobial Resistance of blaTEM and blaCTX-M Genes in Escherichia coli Isolated From Patients With a Urinary Tract Infection

Introduction: The production of β-lactamase in bacteria, especially in Escherichia coli as a prevalent opportunistic bacterium, has caused many problems in patient treatment. β-lactamases are encoded by extended-spectrum β-lactamase (ESBL) genes such as blaTEM and blaCTX-M. We aimed to assess the prevalence and antibiotic sensitivity of β-lactamases encoded by blaCTX-M and blaTEM in E. coli isolated from patients suffering from urinary tract infections (UTIs). Methods: Escherichia coli strains were isolated from the patients’ urine culture presented to medical diagnostic laboratories in Zabol, Iran. The agar disc-diffusion test was performed on Müller-Hinton agar to investigate the antibiotic resistance of these isolates using eight antimicrobial paper discs including gentamicin, tetracycline, co-trimoxazole, norfloxacin, cefuroxime, ampicillin, neomycin, and amoxicillin. A conventional polymerase chain reaction (PCR) was used to detect blaCTX-M and blaTEM. Results: The frequencies of resistance to cefuroxime, norfloxacin, co-trimoxazole, neomycin, amoxicillin, tetracycline, gentamicin, and ampicillin were found to be 45 (90%), 15 (30%), 33 (66%), 33 (66%), 44 (88%), 34 (68%), 4 (8%), and 50 (100%), respectively. Moreover, the prevalence of blaCTX-M was 25 (50%) while that of blaTEM was 16 (32%). Conclusion: Based on the results, gentamicin and norfloxacin can be recommended as effective antibacterials for treating UTI caused by E. coli in the study population. Moreover, the frequency of resistant genes including blaCTX-M and blaTEM was high in the isolated E. coli. Effective control systems including appropriate treatments for ESBL-producing strains are therefore required for humans and food animals.

Shigella flexneri: an emerging pathogen

Shigella flexneri is a leading etiologic agent of diarrhea in low socioeconomic countries. Notably, various serotypes in S. flexneri are reported from different regions of the world. The precise approximations of illness and death owing to shigellosis are missing in low socioeconomic countries, although it is widespread in different regions. The inadequate statistics available reveal S. flexneri to be a significant food and waterborne pathogen. All over the world, different antibiotic-resistant strains of S. flexneri serotypes have been emerged especially multidrug-resistant strains. Recently, increased resistance was observed in cephalosporins (3rd generation), azithromycin, and fluoroquinolones. There is a need for a continuous surveillance study on antibiotic resistance that will be helpful in the update of the antibiogram. The shigellosis burden can be reduced by adopting preventive measures like delivery of safe drinking water, suitable sanitation, and development of an effective and inexpensive multivalent vaccine. This review attempts to provide the recent findings of S. flexneri related to epidemiology and the emergence of multidrug resistance.

Efficacy of cefoxitin for the treatment of urinary tract infection due to extended-spectrum-beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae isolates

Introduction

Cefoxitin has a good in vitro activity and stability in resistance to hydrolysis by extended-spectrum beta-lactamases and is a good candidate for the treatment of urinary tract infection. However, data are scarce regarding its use in clinical practice.

Methods

We conducted a retrospective study from September 2014 to November 2017, in a tertiary care hospital in Garches (France). We gathered all prescriptions of cefoxitin for urinary tract infection due to extended-spectrum beta-lactamase isolates. We compared the clinical outcomes between Escherichia coli and Klebsiella pneumoniae extended-spectrum-beta-lactamase-producing isolates after a 90-day follow-up. When available, we assessed whether cefoxitin-based regimen was associated with an emergence of resistance.

Results

The treatment of 31 patients with a mean age of 60 ± 18 years was analyzed. We observed a clinical cure of 96.7% (n = 30/31) at day 30 and of 81.2% (n = 13/16) and 85.7% (12/14) at day 90 for extended-spectrum beta-lactamase Escherichia coli and Klebsiella pneumoniae isolates, respectively (p = 0.72). No adverse events were reported. One patient who relapsed carried a Klebsiella pneumoniae isolate that became intermediate to cefoxitin in the follow-up.

Conclusion

In a period of major threat with a continuous increase of extended-spectrum beta-lactamase obliging to a policy of carbapenem-sparing regimens, it seems detrimental to deprive physicians of using cefoxitin for extended-spectrum beta-lactamase Enterobacteriaceae for the treatment of urinary tract infection while our data show its efficacy.

ESBL-producing Escherichia coli and Its Rapid Rise among Healthy People

Since around the 2000s, Escherichia coli (E. coli) resistant to both oxyimino-cephalosporins and fluoroquinolones has remarkably increased worldwide in clinical settings. The kind of E. coli is also identified in patients suffering from community-onset infectious diseases such as urinary tract infections. Moreover, recoveries of multi-drug resistant E. coli from the feces of healthy people have been increasingly documented in recent years, although the actual state remains uncertain. These E. coli isolates usually produce extended-spectrum β-lactamase (ESBL), as well as acquisition of amino acid substitutions in the quinolone-resistance determining regions (QRDRs) of GyrA and/or ParC, together with plasmid-mediated quinolone resistance determinants such as Qnr, AAC(6')-Ib-cr, and QepA. The actual state of ESBL-producing E. coli in hospitalized patients has been carefully investigated in many countries, while that in healthy people still remains uncertain, although high fecal carriage rates of ESBL producers in healthy people have been reported especially in Asian and South American countries. The issues regarding the ESBL producers have become very complicated and chaotic due to rapid increase of both ESBL variants and plasmids mediating ESBL genes, together with the emergence of various "epidemic strains" or "international clones" of E. coli and Klebsiella pneumoniae harboring transferable-plasmids carrying multiple antimicrobial resistance genes. Thus, the current state of ESBL producers outside hospital settings was overviewed together with the relation among those recovered from livestock, foods, pets, environments and wildlife from the viewpoint of molecular epidemiology. This mini review may contribute to better understanding about ESBL producers among people who are not familiar with the antimicrobial resistance (AMR) threatening rising globally.

Outcome of bloodstream infections among spinal cord injury patients and impact of multidrug-resistant organisms

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

Our study aimed to describe the outcome of bloodstream infection (BSI) in spinal cord injury (SCI) patients and their associated risk factors for severity and mortality.

SETTING

A French University Hospital.

METHODS

We conducted a retrospective cohort study of all BSIs occurring in hospitalized SCI patients. We analyzed their outcome and risk factors especially the impact of multidrug-resistant organisms (MDROs).

RESULTS

Overall, 318 BSIs occurring among 256 patients were included in the analysis. Mean age was 50.8 years and gender ratio (M/F) was 2.70, with a mean injury duration of 11.6 years.Severity and 30-day mortality of BSI episodes were, respectively, 43.4% and 7.9%. BSI severity was significantly more frequent when caused by respiratory tract infections (RTIs) (odds ratio (OR)=1.38; 95% confidence interval (CI): 1.13-1.44) and significantly lower when caused by urinary tract infections (UTIs) (OR=0.47; 95% CI: 0.28-0.76). BSI mortality was significantly higher when caused by RTIs (OR=3.08; 95% CI: 1.05-8.99), catheter-related bloodstream infections (OR=3.54; 95% CI: 1.36-9.18) or Pseudomonas aeruginosa infections (OR=3.79; 95% CI: 1.14-12.55).MDROs were responsible for 41.2% of all BSI. They have no impact on severity and mortality, whichever be the primary site of infection.In multivariate analysis, mortality was higher when BSI episodes were due to RTIs (OR=3.26; 95% CI: 1.29-8.22) and Pseudomonas aeruginosa infections (OR=3.53; 95% CI: 1.06-11.70), or when associated with immunosuppressive therapy (OR=2.57; 95% CI: 1.14-5.78) or initial severity signs (OR=1.68; 95% CI: 1.01-2.81).

CONCLUSION

BSI occurring in SCI population were often severe but mortality remained low. MDROs were frequent but not associated with severity or mortality of BSI episodes. Risk factors associated with mortality were initial severe presentation, RTI, immunosuppressive therapy and BSI due to Pseudomonas aeruginosa.

Blood stream infections due to multidrug-resistant organisms among spinal cord-injured patients, epidemiology over 16 years and associated risks: a comparative study

STUDY DESIGN

Retrospective study.

OBJECTIVES

We aimed to describe the epidemiology of multidrug-resistant organisms (MDROs) during bloodstream infection (BSI) and identify associated risks of MDROs among patients with spinal cord injury (SCI).

SETTING

A teaching hospital, expert center in disability, in France.

METHODS

We studied a retrospective cohort of all BSIs occurring in SCI patients hospitalized over 16 years. We described the prevalence of MDRO BSI among this population and its evolution over time and compared the BSI population due to MDROs and due to non-MDROs.

RESULTS

A total of 318 BSIs occurring among 256 patients were included in the analysis. The most frequent primary sites of infection were urinary tract infection (34.0%), pressure sore (25.2%) and catheter line-associated bloodstream infection (11.3%). MDROs were responsible for 41.8% of BSIs, and this prevalence was stable over 16 years. No significant associated factor for MDRO BSI could be identified concerning sociodemographic and clinical characteristics, primary site of infection and bacterial species in univariate and multivariate analyses. BSI involving MDROs was not associated with initial severity of sepsis compared with infection without MDROs (43.8 vs 43.6%, respectively) and was not associated either with 30th-day mortality (6.2 vs 9%, respectively).

CONCLUSION

During BSI occurrence in an SCI population, MDROs are frequent but remain stable over years. No associated risk can be identified that would help optimize antibiotic treatment. Neither the severity of the episode nor the mortality is significantly different when an MDRO is involved.

The challenge of efflux-mediated antibiotic resistance in Gram-negative bacteria

The global emergence of multidrug-resistant Gram-negative bacteria is a growing threat to antibiotic therapy. The chromosomally encoded drug efflux mechanisms that are ubiquitous in these bacteria greatly contribute to antibiotic resistance and present a major challenge for antibiotic development. Multidrug pumps, particularly those represented by the clinically relevant AcrAB-TolC and Mex pumps of the resistance-nodulation-division (RND) superfamily, not only mediate intrinsic and acquired multidrug resistance (MDR) but also are involved in other functions, including the bacterial stress response and pathogenicity. Additionally, efflux pumps interact synergistically with other resistance mechanisms (e.g., with the outer membrane permeability barrier) to increase resistance levels. Since the discovery of RND pumps in the early 1990s, remarkable scientific and technological advances have allowed for an in-depth understanding of the structural and biochemical basis, substrate profiles, molecular regulation, and inhibition of MDR pumps. However, the development of clinically useful efflux pump inhibitors and/or new antibiotics that can bypass pump effects continues to be a challenge. Plasmid-borne efflux pump genes (including those for RND pumps) have increasingly been identified. This article highlights the recent progress obtained for organisms of clinical significance, together with methodological considerations for the characterization of MDR pumps.

Risk Factors for and Clinical Outcomes of Bloodstream Infections Caused by Extended-Spectrum Beta-Lactamase-ProducingKlebsiella pneumoniae

Objective:

To evaluate risk factors and treatment outcomes of bloodstream infections caused by extended-spectrum beta-lactamase-producingKlebsiella pneumoniae(ESBL-KP).

Design:

Retrospective case-control study. Stored blood isolates ofK. pneumoniaewere tested for ESBL production by NCCLS guidelines, double-disk synergy test, or both.

Setting:

A 1,500-bed, tertiary-care university hospital and referral center.

Patients:

Sixty case-patients with bacteremia due to ESBL-KP were compared with 60 matched control-patients with non-ESBL-KP.

Results:

There were no significant differences in age, gender, APACHE II score, or underlying diseases between the groups. Independent risk factors for infections caused by ESBL-KP were urinary catheterization, invasive procedure within the previous 72 hours, and an increasing number of antibiotics administered within the previous 30 days. Complete response rate, evaluated 72 hours after initial antimicrobial therapy, was higher among control-patients (13.3% vs 36.7%;P= .003). Treatment failure rate was higher among case-patients (35.0% vs 15%;P= .011). Overall 30-day mortality rate was 30% for case-patients and 28.3% for control-patients (P= .841). Case-patients who received imipenem or ciprofloxacin as a definitive antibiotic had 10.5% mortality. The mortality rate for initially ineffective therapy was no higher than that for initially effective therapy (9.1% vs 11.1%;P= 1.000), but statistical power was low for evaluating mortality in the absence of septic shock.

Conclusion:

ForK. pneumoniaebacteremia, patients with ESBL-KP had a higher initial treatment failure rate but did not have higher mortality if antimicrobial therapy was appropriately adjusted in this study with limited statistical power.

Global dissemination of β2-lactamases mediating resistance to cephalosporins and carbapenems

While the main era of beta-lactam discovery programs is over, these agents continue to be the most widely prescribed antimicrobials in both community and hospital settings. This has led to considerable beta-lactam pressure on pathogens, resulting in a literal explosion of new beta-lactamase variants of existing enzyme classes. Recent advances in the molecular tools used to detect and characterize beta-lactamases and their genes has, in part, fueled the large increase in communications identifying novel beta-lactamases, particularly in Gram-negative bacilli. It now seems clear that the beta-lactams themselves have shaped the field of new enzymes, and the evolution of key amino acid substitutions around the active sites of beta-lactamases continues to drive resistance. Over 130 variants of TEM beta-lactamase now exist, and more are reported in the scientific literature each month. The most disturbing current trend is that many bla structural genes normally limited to the chromosome are now mobilized on plasmids and integrons, broadening the spread of resistance to include carbapenems and cephamycins. Furthermore, in some Enterobacteriaceae, concomitant loss of outer membrane porins act in concert with these transmissible beta-lactamase genes to confer resistance to the most potent beta-lactams and inhibitor combinations available. Continued reviews of the literature are necessary in order to keep abreast of the ingenuity with which bacteria are changing the current genetic landscape to confer resistance to this important class of antimicrobials.

Detection of colonization by carbapenemase-producing Gram-negative Bacilli in patients by use of the Xpert MDRO assay

Detecting colonization of patients with carbapenemase-producing bacteria can be difficult. This study compared the sensitivity and specificity of a PCR-based method (Xpert MDRO) for detecting blaKPC, blaNDM, and blaVIM carbapenem resistance genes using GeneXpert cartridges to the results of culture with and without a broth enrichment step on 328 rectal, perirectal, and stool samples. The culture method included direct inoculation of a MacConkey agar plate on which a 10-μg meropenem disk was placed and plating on MacConkey agar after overnight enrichment of the sample in MacConkey broth containing 1 μg/ml of meropenem. Forty-three (13.1%) samples were positive by PCR for blaKPC and 11 (3.4%) were positive for blaVIM; none were positive for blaNDM. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the PCR assay for blaKPC were 100%, 99.0%, 93.0%, and 100%, respectively, compared to broth enrichment culture and sequencing of target genes. The sensitivity, specificity, PPV, and NPV of the assay for blaVIM were 100%, 99.4%, 81.8%, and 100%, respectively. Since none of the clinical samples contained organisms with blaNDM, 66 contrived stool samples were prepared at various dilutions using three Klebsiella pneumoniae isolates containing blaNDM. The PCR assay showed 100% positivity at dilutions from 300 to 1,800 CFU/ml and 93.3% at 150 CFU/ml. The Xpert MDRO PCR assay required 2 min of hands-on time and 47 min to complete. Rapid identification of patients colonized with carbapenemase-producing organisms using multiplex PCR may help hospitals to improve infection control activities.

The potential of use basil and rosemary essential oils as effective antibacterial agents

The considerable therapeutical problems of persistent infections caused by multidrug-resistant bacterial strains constitute a continuing need to find effective antimicrobial agents. The aim of this study was to demonstrate the activities of basil (Ocimum basilicum L.) and rosemary (Rosmarinus officinalis L.) essential oils against multidrug- resistant clinical strains of Escherichia coli. A detailed analysis was performed of the resistance of the drug to the strains and their sensitivity to the tested oils. The antibacterial activity of the oils was tested against standard strain Escherichia coli ATCC 25922 as well as 60 other clinical strains of Escherichia coli. The clinical strains were obtained from patients with infections of the respiratory tract, abdominal cavity, urinary tract, skin and from hospital equipment. The inhibition of microbial growth by both essential oils, presented as MIC values, were determined by agar dilution. Susceptibility testing to antibiotics was carried out using disc diffusion. The results showed that both tested essential oils are active against all of the clinical strains from Escherichia coli including extended-spectrum β-lactamase positive bacteria, but basil oil possesses a higher ability to inhibit growth. These studies may hasten the application of essential oils in the treatment and prevention of emergent resistant strains in nosocomial infections.

Assessment of extended-spectrum β-lactamase, KPC carbapenemase and porin resistance mechanisms in clinical samples of Klebsiella pneumoniae and Enterobacter spp

The emergence and spread of resistance mechanisms in Gram-negative bacilli has complicated the treatment of serious nosocomial infections. Current automated systems for detection of Klebsiella pneumoniae carbapenemase (KPC)-producing isolates are unreliable. One possible straightforward alternative method is evaluation of ertapenem resistance. However, the accuracy of this method is affected by other resistance mechanisms such as AmpC gene expression or extended-spectrum β-lactamase production associated with porin loss. This study included 128 samples of K. pneumoniae and Enterobacter spp. that were non-susceptible to ertapenem. The disk diffusion and Etest method were applied to determine susceptibility to imipenem, meropenem and ertapenem. Isolates exhibiting intermediate or complete resistance to ertapenem were evaluated for resistance mechanisms. bla(TEM), bla(SHV), bla(CTX-M), bla(CTX-M-2) and bla(KPC) genes were tested for by PCR, and the presence of outer membrane protein was investigated by dot-blot assay. bla(TEM) was detected in 52.9% and 10.3%, bla(SHV) in 29.4% and 0.94%, bla(CTX-M) in 41.4% and 1.9% and bla(CTX-M-2) in 23.5% and 1.9% of K. pneumoniae and Enterobacter cloacae isolates, respectively. The bla(KPC) gene was present in 12.6% of Enterobacter spp. isolates. OmpC and OmpF were present in 6.6% of E. cloacae isolates. These results indicate that several resistance mechanisms contribute to potential therapeutic failure of carbapenem therapy and point to the need for better detection methods and surveillance strategies.

Designing antibiotic cycling strategies by determining and understanding local adaptive landscapes

The evolution of antibiotic resistance among bacteria threatens our continued ability to treat infectious diseases. The need for sustainable strategies to cure bacterial infections has never been greater. So far, all attempts to restore susceptibility after resistance has arisen have been unsuccessful, including restrictions on prescribing [1] and antibiotic cycling [2], [3]. Part of the problem may be that those efforts have implemented different classes of unrelated antibiotics, and relied on removal of resistance by random loss of resistance genes from bacterial populations (drift). Here, we show that alternating structurally similar antibiotics can restore susceptibility to antibiotics after resistance has evolved. We found that the resistance phenotypes conferred by variant alleles of the resistance gene encoding the TEM β-lactamase (bla_TEM) varied greatly among 15 different β-lactam antibiotics. We captured those differences by characterizing complete adaptive landscapes for the resistance alleles bla_TEM-50 and bla_TEM-85, each of which differs from its ancestor bla_TEM-1 by four mutations. We identified pathways through those landscapes where selection for increased resistance moved in a repeating cycle among a limited set of alleles as antibiotics were alternated. Our results showed that susceptibility to antibiotics can be sustainably renewed by cycling structurally similar antibiotics. We anticipate that these results may provide a conceptual framework for managing antibiotic resistance. This approach may also guide sustainable cycling of the drugs used to treat malaria and HIV.

Fosfomycin: efficacy against infections caused by multidrug-resistant bacteria

OBJECTIVE

To analyze the indications for and the efficacy of parenteral fosfomycin, especially against multidrug-resistant (MDR) and pan-resistant bacterial infections.

PATIENTS AND METHODS

During a unique crisis in fosfomycin production, the supply of this antibiotic had to be carefully monitored in France over a 10-week period. One hundred and sixteen assessable patients were included in a prospective cohort study.

RESULTS

The main indications for use were osteoarthritis, lung infection, urinary tract infection, and bacteraemia. The 2 bacteria most frequently involved were Pseudomonas aeruginosa and methicillin-resistant Staphylococcus. MDR bacteria were seen in 71.5% (83/116) of cases, especially MDR P. aeruginosa (n = 28). Critical situations were common, with 44.0% (51/116) of hospitalizations occurring in an intensive care unit and 22.4% (26/116) of patients with septic shock. The overall outcome was favourable in 76.8% of cases (76/99 assessable patients).

CONCLUSION

This study provided a unique opportunity to describe the use of fosfomycin and assess its efficacy, especially against MDR bacterial infections, even in critical situations.

Comparison of disc diffusion methods for the detection of extended-spectrum Beta lactamase-producing enterobacteriaceae

Background:

Resistance to broad-spectrum β lactams, mediated by extended-spectrum β lactamases (ESBLs), is an increasing problem world wide. This resistance poses problems for in vitro testing and reporting. Increased prevalence of ESBLs among Enterobacteriaceae creates a great need for laboratory testing methods that will accurately identify their presence.

Materials and Methods:

During the study, the Enterobacteriaceae isolated were tested for the presence of ESBL by the National Committee for Clinical Laboratory Standards (NCCLS) screening test, Jarlier double disc synergy (approximation) test (DDST) and NCCLS phenotypic confirmatory test (PCT), and compared their efficiency in detection.

Results:

A total of 313 Enterobacteriaceae were isolated and tested for the presence of ESBL. NCCLS PCT identified 200 (63.89%) as ESBL producers and DDST identified 176 (56.23%), with a P-value of <0.001. Among the screening agents, ceftazidime had a better sensitivity (89.49%) and specificity (95.74%).

Conclusions:

Close monitoring of the susceptibility pattern of isolates and careful spacing with specific discs can identify many ESBL producers. Ceftazidime has a better sensitivity and specificity as a screening agent. A combination of different tests can be useful for accurate identification.

qnr Prevalence in Extended Spectrum Beta-lactamases (ESBLs) and None-ESBLs Producing Escherichia coli Isolated from Urinary Tract Infections in Central of Iran

OBJECTIVES

Extensive use of quinolones has been associated with raising level of resistance. In the current, we focused on assessing the prevalence of Escherichia coli resistance to quinolones and frequency of qnrA, qnrB and qnrS in non ESBLs (extended spectrum beta-lactamases) and ESBLs producing E. coli with blaSHV and blaTEM.

MATERIALS AND METHODS

One hundred and fifty E. coli isolates were identified during Mar. 2007 to Apr. 2008 in Milad () hospital. They were tested for ESBLs production as well as quinolone resistance. PCR was performed for detection of blaSHV and blaTEM as well as qnrA, B and S.

RESULTS

Of 150 isolates, forty-two (28%) ESBLs producing and one hundred and eight (72%) non-ESBLs producing E. coli were identified. 64.2% (n= 24) of E. coli producing ESBLs and 4.62% (n= 5) of non-ESBLs E. coli were resistance to ciprofloxacin. 95.2% (n= 40) and 26.1% (n= 11) of the isolates harbored blaTEM and blaSHV, respectively. 23.8% (n= 10) had both genes. 37.5% (n= 9) and 20.8% (n= 4) of ESBLs producing E. coli were positive for qnrA and qnrB respectively. qnrS was not identified in any isolate.

CONCLUSION

Our study showed high frequency of ESBLs producing E. coli as well as quinolone resistance genes (qnrA, qnrB) in Milad hospital.

Characterization of multidrug resistant ESBL-producing Escherichia coli isolates from hospitals in Malaysia

The emergence of Escherichia coli that produce extended spectrum beta-lactamases (ESBLs) and are multidrug resistant (MDR) poses antibiotic management problems. Forty-seven E. coli isolates from various public hospitals in Malaysia were studied. All isolates were sensitive to imipenem whereas 36 were MDR (resistant to 2 or more classes of antibiotics). PCR detection using gene-specific primers showed that 87.5% of the ESBL-producing E. coli harbored the blaTEM gene. Other ESBL-encoding genes detected were blaOXA, blaSHV, and blaCTX-M. Integron-encoded integrases were detected in 55.3% of isolates, with class 1 integron-encoded intI1 integrase being the majority. Amplification and sequence analysis of the 5'CS region of the integrons showed known antibiotic resistance-encoding gene cassettes of various sizes that were inserted within the respective integrons. Conjugation and transformation experiments indicated that some of the antibiotic resistance genes were likely plasmid-encoded and transmissible. All 47 isolates were subtyped by PFGE and PCR-based fingerprinting using random amplified polymorphic DNA (RAPD), repetitive extragenic palindromes (REPs), and enterobacterial repetitive intergenic consensus (ERIC). These isolates were very diverse and heterogeneous. PFGE, ERIC, and REP-PCR methods were more discriminative than RAPD in subtyping the E. coli isolates.

Performance of the Phoenix bacterial identification system compared with disc diffusion methods for identifying extended-spectrum beta-lactamase, AmpC and KPC producers

Phenotypic identification of AmpC, KPC and extended-spectrum beta-lactamases (ESBLs) among members of the Enterobacteriaceae remains challenging. This study compared the Phoenix Automated Microbiology System (BD Diagnostics) with the Clinical and Laboratory Standards Institute confirmatory method to identify ESBL production among 200 Escherichia coli and Klebsiella pneumoniae clinical isolates. The Phoenix system misclassified nearly half of the isolates as ESBL-positive, requiring manual testing for confirmation. Inclusion of aztreonam +/- clavulanic acid (CA) and cefpodoxime +/- CA in the testing algorithm increased the ESBL detection rate by 6 %. Boronic acid-based screening identified 24 isolates as AmpC(+), but in a subset of genotypically characterized isolates, appeared to have a high false-positivity rate. PCR screening revealed eight KPC(+) isolates, all of which tested as ESBL(+) or ESBL(+) AmpC(+) by phenotypic methods, but half were reported as carbapenem-susceptible by the Phoenix system. Overall, these results indicate that laboratories should use the Phoenix ESBL results only as an initial screen followed by confirmation with an alternative method.

Control of extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in a children's hospital by changing antimicrobial agent usage policy

OBJECTIVES

This ambidirectional intervention study was performed to examine the impact of a change in antibiotic policy on extended-spectrum beta-lactamase (ESBL) prevalence in a children's hospital with a high prevalence of ESBL production among Escherichia coli and Klebsiella pneumoniae.

METHODS

The use of extended-spectrum cephalosporins was restricted and use of beta-lactam/ beta-lactamase inhibitor combinations was encouraged from 2002. All strains of E. coli and K. pneumoniae isolated from sterile body fluids from 1999 to 2005 were analysed for beta-lactamase production and the prevalences of ESBL production were compared at three periods; pre-intervention (1999-2001), transitional period (2002-03) and post-intervention (2004-05).

RESULTS

Comparing the pre- and post-intervention periods, overall piperacillin/tazobactam use increased from 2.2 to 108.0 days on antibiotics/1000 patient admission days/year (AD) (P for trend < 0.001), whereas extended-spectrum cephalosporin use decreased from 175.0 to 96.9 AD (P for trend < 0.001). Among 252 strains of E. coli (n = 128) and K. pneumoniae (n = 124), the overall prevalence of ESBL producers decreased from 39.8% (41/103) to 22.8% (18/79) (P for trend = 0.018). This decreasing trend of ESBL production was more evident for K. pneumoniae (64.1% to 25.6%; P for trend < 0.001) than E. coli (25.0% to 19.4%; P for trend = 0.514). The mortality rates of invasive disease caused by E. coli or K. pneumoniae remained unchanged.

CONCLUSIONS

The substitution of piperacillin/tazobactam for extended-spectrum cephalosporins successfully decreased the prevalence of ESBL production of K. pneumoniae and E. coli in an institute for children where ESBLs were endemic. The impact of change in antibiotic policy was more evident in K. pneumoniae than E. coli.

The AmpC inhibitor, Syn2190, can be used to reveal extended-spectrum beta-lactamases in Escherichia coli

AmpC beta-lactamases are not inhibited by clavulanic acid and could potentially mask detection of extended-spectrum beta-lactamases (ESBLs) using the Clinical and Laboratory Standards Institute confirmatory test. Syn2190 (1,5-dihydroxy-4-pyridone monobactam) selectively inhibits AmpC, but not ESBLs. Fifty-four MicroScan ESBL screen-positive strains of Escherichia coli and an unrelated group of 20 cefoxitin-nonsusceptible E. coli strains were tested with the confirmatory ceftazidime-cefotaxime-clavulanate disk method with or without 4 microg/mL of Syn2190 in the agar. Without Syn2190, 8 (14.8%) of 54 E. coli isolates and 0 of 20 cefoxitin-nonsusceptible E. coli isolates were confirmed. With Syn2190, an additional 9 (16.6%) of 54 of the MicroScan screen-positive E. coli isolates and 6 (30%) of 20 of the cefoxitin-nonsusceptible E. coli isolates were found. Multiplex polymerase chain reaction and sequence analysis confirmed the presence of the plasmid-associated beta-lactamase gene bla(CMY-2) in the 2 available MicroScan-screened E. coli isolates and in 5 of 6 of the cefoxitin-resistant group. These data suggest that in the presence of AmpC, ESBLs in E. coli may not be detected by the currently recommended confirmatory test.

Evaluation of the new VITEK 2 extended-spectrum beta-lactamase (ESBL) test for rapid detection of ESBL production in Enterobacteriaceae isolates

Extended-spectrum beta-lactamases (ESBLs) are a large, rapidly evolving group of enzymes that confer resistance to oxyimino cephalosporins and monobactams and are inhibited by clavulanate. Rapid reliable detection of ESBL production is a prerequisite for successful infection management and for monitoring resistance trends and implementation of intervention strategies. We evaluated the performance of the new VITEK 2 ESBL test system (bioMérieux, Inc, Hazelwood, Mo.) in the identification of ESBL-producing Enterobacteriaceae isolates. We examined a total of 1,129 clinically relevant Enterobacteriaceae isolates (including 218 that had been previously characterized). The ESBL classification furnished by the VITEK 2 ESBL test system was concordant with that of the comparison method (molecular identification of beta-lactamase genes) for 1,121 (99.3%) of the 1,129 isolates evaluated. ESBL production was correctly detected in 306 of the 312 ESBL-producing organisms (sensitivity, 98.1%; positive predictive value, 99.3%). False-positive results emerged for 2 of the 817 ESBL-negative isolates (specificity, 99.7%; negative predictive value, 99.3%). VITEK 2 ESBL testing took 6 to 13 h (median, 7.5 h; mean +/- SD, 8.2 +/- 2.39 h). This automated short-incubation system appears to be a rapid and reliable tool for routine identification of ESBL-producing isolates of Enterobacteriaceae.

CTX-M-2 and a new CTX-M-39 enzyme are the major extended-spectrum beta-lactamases in multiple Escherichia coli clones isolated in Tel Aviv, Israel

The rate of occurrence of the extended-spectrum beta-lactamase (ESBL)-producing phenotype among Escherichia coli isolates in Tel Aviv is 12% (22). The aim of this study was to understand the molecular epidemiology of E. coli ESBL producers and to identify the ESBL genes carried by them. We studied 20 single-patient ESBL-producing E. coli clinical isolates. They comprised 11 distinct nonrelated pulsed-field gel electrophoresis (PFGE) genotypes: six isolates belonged to the same PFGE clone, four other clones included two isolates each, and six unrelated clones included only one isolate. All isolates produced various beta-lactamases with pIs ranging from 5.2 to 8.2, varying within similar PFGE clones. The most prevalent ESBL gene was bla(CTX-M); 16 isolates carried bla(CTX-M-2) and three carried a new ESBL gene designated bla(CTX-M-39). Three strains carried bla(SHV) (two bla(SHV-12) and one bla(SHV-5)), and two strains carried inhibitor-resistant ESBL genes, bla(TEM-33) and bla(TEM-30); 18 strains carried bla(TEM-1) and eight strains carried bla(OXA-2). Plasmid mapping and Southern blot analysis with a CTX-M-2 probe demonstrated that bla(CTX-M-2) is plasmid borne. The wide dissemination of ESBLs among E. coli isolates in our institution is partly related to clonal spread, but more notably to various plasmid-associated ESBL genes, occurring in multiple clones, wherein the CTX-M gene family appears almost uniformly. We report here a new CTX-M gene, designated bla(CTX-M-39), which revealed 99% homology with bla(CTX-M-26), with a substitution of arginine for glutamine at position 225.

Extended-spectrum beta-lactamases: a clinical update

Extended-spectrum beta-lactamases (ESBLs) are a rapidly evolving group of beta-lactamases which share the ability to hydrolyze third-generation cephalosporins and aztreonam yet are inhibited by clavulanic acid. Typically, they derive from genes for TEM-1, TEM-2, or SHV-1 by mutations that alter the amino acid configuration around the active site of these beta-lactamases. This extends the spectrum of beta-lactam antibiotics susceptible to hydrolysis by these enzymes. An increasing number of ESBLs not of TEM or SHV lineage have recently been described. The presence of ESBLs carries tremendous clinical significance. The ESBLs are frequently plasmid encoded. Plasmids responsible for ESBL production frequently carry genes encoding resistance to other drug classes (for example, aminoglycosides). Therefore, antibiotic options in the treatment of ESBL-producing organisms are extremely limited. Carbapenems are the treatment of choice for serious infections due to ESBL-producing organisms, yet carbapenem-resistant isolates have recently been reported. ESBL-producing organisms may appear susceptible to some extended-spectrum cephalosporins. However, treatment with such antibiotics has been associated with high failure rates. There is substantial debate as to the optimal method to prevent this occurrence. It has been proposed that cephalosporin breakpoints for the Enterobacteriaceae should be altered so that the need for ESBL detection would be obviated. At present, however, organizations such as the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards) provide guidelines for the detection of ESBLs in klebsiellae and Escherichia coli. In common to all ESBL detection methods is the general principle that the activity of extended-spectrum cephalosporins against ESBL-producing organisms will be enhanced by the presence of clavulanic acid. ESBLs represent an impressive example of the ability of gram-negative bacteria to develop new antibiotic resistance mechanisms in the face of the introduction of new antimicrobial agents.

Why is the microbiology lab calling about an extended-spectrum beta-lactamase bacterium from a wound culture?

As more and more gram-negative bacteria produce extended-spectrum beta-lactamases, it is important that physicians know what to do when these bacteria cause postoperative infections in patients.

Serious Consequences to the Use of Cephalosporins as the First Line of Antimicrobial Therapy Administered in Hemodialysis Units

BACKGROUND

The dramatic spread of vancomycin-resistant enterococci (VRE) among hemodialysis (HD) patients led to the replacement of vancomycin with cephalosporins as part of the primary empiric therapy for bacterial infections in HD units. The aim of the study was to examine the effects of this new regimen on the colonization rate of resistant bacteria among HD patients.

METHODS

Rectal swabs were taken from 105 HD patients and 91 control hospitalized patients. Groups were matched for age, sex, nursing home residency and background diseases. Enterococci were tested for vancomycin resistance, Staphylococcus aureus isolates were tested for methicillin resistance (MRSA), and Enterobacteriaceae were tested for extended-spectrum beta-lactamase (ESBL) activity.

RESULTS

In the HD group 1 VRE, 1 MRSA and 9 ESBL-producing organisms were isolated compared to 1 MRSA and 1 ESBL organism in the control group (p = 0.018 for ESBL). In the year prior to the study, the use of cephalosporins had been enhanced in the HD group compared to the control group (p < 0.001), and in the HD ESBL-positive patients compared to the HD ESBL-negative ones (p = 0.007). The overall use of antibiotics in the control group was the same as in the HD group. In a subanalysis of the HD group alone, the ESBL carriers were older, sicker, used more antibiotics, were hospitalized frequently and had a higher mortality rate, compared to noncarriers.

CONCLUSIONS

The use of cephalosporins as first-line therapy in HD patients in central Israel reduced the prevalence of VRE colonization but may have contributed to the emergence of ESBL-producing organisms through induction of selection pressure. This may lead to serious complications in the management of these patients.

Successive emergence of Enterobacter aerogenes strains resistant to imipenem and colistin in a patient

Enterobacter aerogenes is an agent of hospital-acquired infection that exhibits a remarkable resistance to beta-lactam antibiotics during therapy. Five successive isolates of E. aerogenes infecting a patient and exhibiting a multiresistance phenotype to beta-lactam antibiotics and fluoroquinolones were investigated. Among these clinical strains, four presented resistant phenotypes during successive imipenem and colistin treatments. The involved resistance mechanisms exhibited by the successive isolates were associated with alterations of the outer membrane that caused a porin decrease and lipopolysaccharide modifications.

Molecular epidemiology of Enterobacteriaceae isolates producing extended-spectrum beta-lactamases in a French hospital

In 2002, 80 isolates of Enterobacteriaceae producing extended-spectrum beta-lactamases (ESBLs) were collected from infected patients in our hospital. Enterobacter aerogenes was the most common bacterium isolated from all specimens (36.5%). The ESBLs were predominantly (90%) TEM derivatives (TEM-24, TEM-3). Pulsed-field gel electrophoresis highlighted that E. aerogenes, Klebsiella pneumoniae, and Citrobacter koseri had a clonal propagation.

Utility of NCCLS guidelines for identifying extended-spectrum beta-lactamases in non-Escherichia coli and Non-Klebsiella spp. of Enterobacteriaceae

NCCLS screening and confirmation methods for detecting extended-spectrum beta-lactamases (ESBLs) apply only to Escherichia coli and Klebsiella spp., yet ESBLs have been found in other members of the family Enterobacteriaceae. We evaluated the effectiveness of NCCLS methods for detecting ESBLs in 690 gram-negative isolates of Enterobacteriaceae that excluded E. coli, Klebsiella pneumoniae, and Klebsiella oxytoca. Isolates were collected between January 1996 and June 1999 from 53 U.S. hospitals participating in Project ICARE (Intensive Care Antimicrobial Resistance Epidemiology). The antimicrobial susceptibility patterns of the isolates were determined by using the NCCLS broth microdilution method (BMD), and those isolates for which the MIC of ceftazidime, cefotaxime, ceftriaxone, or aztreonam was >or=2 microg/ml or the MIC of cefpodoxime was >or=8 microg/ml (positive ESBL screen test) were further tested for a clavulanic acid (CA) effect by BMD and the disk diffusion method (confirmation tests). Although 355 (51.4%) of the isolates were ESBL screen test positive, only 15 (2.2%) showed a CA effect. Since 3 of the 15 isolates were already highly resistant to the five NCCLS indicator drugs, ESBL detection would have an impact on the reporting of only 1.7% of the isolates in the study. Only 6 of the 15 isolates that showed a CA effect contained a bla(TEM), bla(SHV), bla(CTX-M), or bla(OXA) beta-lactamase gene as determined by PCR (with a corresponding isoelectric focusing pattern). Extension of the NCCLS guidelines for ESBL detection to Enterobacteriaceae other than E. coli and Klebsiella spp. does not appear to be warranted in the United States at present, since the test has poor specificity for this population and would result in changes in categorical interpretations for only 1.7% of Enterobacteriaceae tested.