Cephalosporin-resistant Enterobacteriaceae Research Articles

Extended spectrum ß-lactamase- and constitutively AmpC-producing Enterobacteriaceae on fresh produce and in the agricultural environment

The attribution of fresh produce to the overall community-associated exposure of humans to ESBL- or AmpC-producing bacteria is currently unknown. To address this issue, the prevalence of ESBL- and AmpC-producing Enterobacteriaceae on fresh produce produced in the Netherlands was determined. Seven vegetable types that are consumed raw were selected: blanched celery, bunched carrots, chicory, endive, iceberg lettuce, mushrooms, and radish. The vegetables were mostly obtained from supermarkets. To determine whether the agricultural environment is the source of ESBL-producing Enterobacteriaceae on fresh produce, iceberg lettuce was also obtained directly from three farms, in conjunction with soil and irrigation water. ESBL-producing Enterobacteriaceae isolated from vegetables and environment were all environmental species: Rahnella aquatilis (n=119), Serratia fonticola (n=45) and Pantoea agglomerans (n=1). ESBL genes of R. aquatilis and S. fonticola were identified as blaRAHN-1 and blaRAHN-2 and blaFONA-1, blaFONA-2, blaFONA-3/6 and blaFONA-5, respectively. For R. aquatilis and S. fonticola, different prevalence numbers were observed using different isolation methods, which could at least partially be explained by an inverse correlation between the level of cefotaxime resistance of these species and incubation temperature. R. aquatilis was isolated from 0 to 46% of soil samples and 11 to 83% of vegetable samples, and S. fonticola from 2 to 60% of soil samples and 0 to 1.3% of vegetable samples. Third generation cephalosporin-resistant faecal Enterobacteriaceae were isolated from 2.7%, 1.3% and 1.1% of supermarket vegetables, iceberg lettuce from farms, and agricultural soil respectively. Faecal Enterobacteriaceae were all identified as Citrobacter and Enterobacter species and, with the exception of one Citrobacter koseri strain, all had phenotypes indicative of constitutive AmpC production. Comparison of fresh produce and its agricultural environment indicates that the Enterobacteriaceae population on fresh produce reflects that of the soil it is grown in.Public health risks associated with exposure to ESBL- and AmpC-producing bacteria through consumption of uncooked fresh produce are diverse. They range from occasional ingestion of 3GC-resistant opportunistic pathogens which may result in difficult-to-treat infections, to frequent ingestion of relatively harmless ESBL-producing environmental bacteria that may therewith constitute a continuously replenished intestinal reservoir facilitating dissemination of ESBL genes to (opportunistic) pathogens.

Identical plasmid AmpC beta-lactamase genes and plasmid types in E. coli isolates from patients and poultry meat in the Netherlands

The increasing prevalence of third-generation cephalosporin-resistant Enterobacteriaceae is a worldwide problem. Recent studies showed that poultry meat and humans share identical Extended-Spectrum Beta-Lactamase genes, plasmid types, and Escherichia coli strain types, suggesting that transmission from poultry meat to humans may occur. The aim of this study was to compare plasmid-encoded Ambler class C beta-lactamase (pAmpC) genes, their plasmids, and bacterial strain types between E. coli isolates from retail chicken meat and clinical isolates in the Netherlands.In total, 98 Dutch retail chicken meat samples and 479 third-generation cephalosporin non-susceptible human clinical E. coli isolates from the same period were screened for pAmpC production. Plasmid typing was performed using PCR-based replicon typing (PBRT). E coli strains were compared using Multi-Locus-Sequence-Typing (MLST).In 12 of 98 chicken meat samples (12%), pAmpC producing E. coli were detected (all blaCMY-2). Of the 479 human E. coli, 25 (5.2%) harboured pAmpC genes (blaCMY-2 n=22, blaACT n=2, blaMIR n=1). PBRT showed that 91% of poultry meat isolates harboured blaCMY-2 on an IncK plasmid, and 9% on an IncI1 plasmid. Of the human blaCMY-2 producing isolates, 42% also harboured blaCMY-2 on an IncK plasmid, and 47% on an IncI1 plasmid. Thus, 68% of human pAmpC producing E. coli have the same AmpC gene (blaCMY-2) and plasmid type (IncI1 or IncK) as found in poultry meat. MLST showed one cluster containing one human isolate and three meat isolates, with an IncK plasmid. These findings imply that a foodborne transmission route of blaCMY-2 harbouring plasmids cannot be excluded and that further evaluation is required.

Temporal trends of extended-spectrum cephalosporin-resistant Escherichia coli and Klebsiella pneumoniae isolates in in- and outpatients in Switzerland, 2004 to 2011

Increasing trends for invasive infections with extended-spectrum cephalosporin-resistant (ESC-R) Enterobacteriaceae have been described in many countries worldwide. However, data on the rates of ESC-R isolates in non-invasive infections and in the outpatient setting are scarce. We used a laboratory-based nationwide surveillance system to compare temporal trends of ESC-R rates in Escherichia coli and Klebsiella pneumoniae for in- and outpatients in Switzerland. Our data showed a significant increase in ESC-R rates from 1% to 5.8% in E. coli (p<0.001) and from 1.1% to 4.4% in K. pneumoniae (p=0.002) during an eight-year period (2004–2011). For E. coli, the increase was significantly higher in inpatients (from 1.2% to 6.6%), in patients residing in eastern Switzerland (from 1.0% to 6.2%), in patients older than 45 years (from 1.2% to 6.7%), and in male patients (from 1.2% to 8.1%). While the increase in inpatients was linear (p<0.001) for E. coli, the increase of ESC R K. pneumoniae isolates was the result of multiple outbreaks in several institutions. Notably, an increasing proportion of ESC-R E. coli was co-resistant to both trimethoprim-sulfamethoxazole and quinolones (42% in 2004 to 49.1% in 2011, p=0.009), further limiting the available oral therapeutic options.

Cross-Sectional Study on Fecal Carriage ofEnterobacteriaceaewith Resistance to Extended-Spectrum Cephalosporins in Primary Care Patients

The aim of this study was to gain knowledge of the local epidemiology of extended-spectrum cephalosporin-resistant bacteria in primary care patients in a Swiss community. Fecal swabs were obtained from 291 primary care patients. Phenotyping and genotyping methods were used for further characterization of the isolates. Risk factors associated with carriage of ß-lactam-resistant strains were determined. Extended-spectrum cephalosporin-resistant Enterobacteriaceae were detected in 15 (5.2%) of the primary care patients. Thirteen isolates were CTX-M producers, one produced SHV-12, and three carried CMY-2. The pathogenic pandemic clone Escherichia coli ST131 was detected in 26.6% of the patients. Two patients (13.3%) carried two distinct strains simultaneously. There was a statistically significant risk of carriage of resistant strains for persons with a history of antibiotic therapy 4 months before sampling (p=0.05), markedly for therapy with ß-lactam (p=0.01). Age, gender, or history of hospitalization 4 months before sampling was not a risk factor for the acquisition of resistant bacteria in the analyzed patients. The relatively low prevalence of extended-spectrum cephalosporin-resistant strains in the community reflects the nationwide restrictive policy of antibiotic prescription as well as local implementation thereof. Nevertheless, our study shows that a potent antimicrobial resistance reservoir is present in primary care patients.

Decontamination of cephalosporin-resistant Enterobacteriaceae during selective digestive tract decontamination in intensive care units

Prevalences of cephalosporin-resistant Enterobacteriaceae are increasing globally, especially in intensive care units (ICUs). The effect of selective digestive tract decontamination (SDD) on the eradication of cephalosporin-resistant Enterobacteriaceae from the intestinal tract is unknown. We quantified eradication rates of cephalosporin-resistant and cephalosporin-susceptible Enterobacteriaceae during SDD in patients participating in a 13 centre cluster-randomized study and from a single-centre cohort. All SDD patients colonized with Enterobacteriaceae in the intestinal tract at ICU admission were included. Cephalosporin resistance was defined as resistance to ceftazidime, cefotaxime or ceftriaxone and aminoglycoside resistance as resistance to tobramycin or gentamicin. Duration of rectal colonization was determined by screening twice weekly during ICU stay. Swabs were inoculated on selective medium supplemented with tobramycin or cefotaxime. Five hundred and seven (17%) of 2959 SDD patients with at least one rectal sample were colonized with Enterobacteriaceae at ICU admission: 77 (15%) with cephalosporin-resistant Enterobacteriaceae and 50 (10%) with aminoglycoside-resistant Enterobacteriaceae. Fifty-six (73%) patients colonized with cephalosporin-resistant Enterobacteriaceae were successfully decontaminated before ICU discharge, as were 343 (80%) patients colonized with cephalosporin-susceptible Enterobacteriaceae (P = 0.17). For aminoglycoside resistance, 31 (62%) patients were decontaminated, as were 368 patients (81%) colonized with aminoglycoside-susceptible Enterobacteriaceae (P < 0.01). On average, decolonization was demonstrated after 4 days if colonized with cephalosporin-susceptible Enterobacteriaceae and aminoglycoside-susceptible Enterobacteriaceae, and after 5 and 5.5 days if colonized with cephalosporin-resistant Enterobacteriaceae and aminoglycoside-resistant Enterobacteriaceae, respectively (log-rank test P = 0.053 for cephalosporin resistance and P = 0.03 for aminoglycoside resistance). If eradication failed, no associations were found with increased resistance in time (P > 0.05 for all comparisons). SDD can successfully eradicate cephalosporin-resistant Enterobacteriaceae from the intestinal tract.

Variability of intestinal colonization with third-generation cephalosporin-resistant Enterobacteriaceae and antibiotic use in intensive care units

Healthcare-associated infections due to third-generation cephalosporin-resistant Enterobacteriaceae (CRE) have become a major public health threat, especially in intensive care units (ICUs). We assessed and compared β-lactam use, the prevalence of colonization with CRE at admission and the incidence of CRE acquisition across ICUs. A cohort study was conducted in 10 ICUs of the Paris (France) metropolitan area between November 2005 and February 2006. Antibiotic use was recorded prospectively in all patients admitted during the study period. Rectal swabs were collected at admission, twice weekly thereafter, before β-lactam prescription and before discharge. A total of 893 patients provided 3453 rectal swabs; 793 of the patients were newly admitted, mostly for medical reasons (80.7%). On admission, 74 patients (9.6%) were colonized with CRE, including 32 with an extended-spectrum β-lactamase (ESBL)-producing strain. Among the remaining 694 naive patients, 94 acquired CRE during their follow-up, including 31 with an ESBL-producing strain. Incidence rates of colonization ranged from 8.8 to 21.0/1000 patient-days for all CRE, and from 1.4 to 10.9/1000 patient-days for ESBL producers. A majority of patients (68.3%) were prescribed β-lactams during their ICU stay, with defined daily doses ranging from 428 to 985/1000 patient-days. Across ICUs, prescriptions of all antibiotics, β-lactams and carbapenems were significantly correlated to incidence rates of colonization with ESBL-producing CRE. The standardized and systematic follow-up of patients in 10 ICUs revealed great heterogeneity in the rates of colonization with ESBL- and non-ESBL-producing CRE, as well as in antimicrobial prescription practices.

Fourteen years in resistance

Resistance trends have changed greatly over the 14 years (1997–2011) whilst I was Director of the UK Antibiotic Resistance Monitoring and Reference Laboratory (ARMRL). Meticillin-resistant Staphylococcus aureus (MRSA) first rose, then fell with improved infection control, although with the decline of one major clone beginning before these improvements. Resistant pneumococci too have declined following conjugate vaccine deployment. If the situation against Gram-positive pathogens has improved, that against Gram-negatives has worsened, with the spread of (i) quinolone- and cephalosporin-resistant Enterobacteriaceae, (ii) Acinetobacter with OXA carbapenemases, (iii) Enterobacteriaceae with biochemically diverse carbapenemases and (iv) gonococci resistant to fluoroquinolones and, latterly, cefixime. Laboratory, clinical and commercial aspects have also changed. Susceptibility testing is more standardised, with pharmacodynamic breakpoints. Treatments regimens are more driven by guidelines. The industry has fewer big profitable companies and more small companies without sales income. There is good and bad here. The quality of routine susceptibility testing has improved, but its speed has not. Pharmacodynamics adds science, but over-optimism has led to poor dose selection in several trials. Guidelines discourage poor therapy but concentrate selection onto a diminishing range of antibiotics, threatening their utility. Small companies are more nimble, but less resilient. Last, more than anything, the world has changed, with the rise of India and China, which account for 33% of the world's population and increasingly provide sophisticated health care, but also have huge resistance problems. These shifts present huge challenges for the future of chemotherapy and for the edifice of modern medicine that depends upon it.

Comparison of plasmid-mediated quinolone resistance and extended-spectrum β-lactamases in third-generation cephalosporin-resistant Enterobacteriaceae from four Irish hospitals

In this study, the frequency of extended-spectrum β-lactamases (ESBL) and plasmid-mediated quinolone resistance (PMQR) mechanisms were investigated in 206 clinical isolates of third-generation cephalosporin (3GC)-resistant Enterobacteriaceae in four hospitals in the Republic of Ireland. bla(CTX-M-15) was the predominant ESBL gene. Of these 3GC resistant isolates, 54 % were also resistant to ciprofloxacin. Investigation of the PMQR mechanisms revealed that the aac(6')Ib-cr gene predominated in fluoroquinolone-resistant (FQR) strains of Escherichia coli and Klebsiella pneumoniae, while the qnrA gene predominated in the FQR strains of Enterobacter. The bla(CTX-M-15) gene was frequently identified with the aac(6')Ib-cr gene but was not always on the same plasmid. The prevalence of the bla(CTX-M-15) gene appeared to be hospital-dependent. The epidemiology of both ESBL-producing and PMQR strains within the four hospitals indicated that their prevalence is not due to the spread of these resistance genes between isolates from different hospitals.

High level cephalosporin-resistant Enterobacteriaceae ventilator-associated pneumonia: prognostic factors based on a cohort study

The impact of high level cephalosporin resistance due to Enterobacteriaceae harbouring a type I-inducible chromosomal β-lactamase on the outcome of ventilator-associated pneumonia (VAP) remains unknown. A retrospective cohort study was conducted in two intensive care units (ICUs) over a four-year period to identify factors prognostic of VAP caused by high level AmpC (HL-AmpC)-producing Enterobacteriaceae. The study included 75 patients, who developed VAP due to Enterobacteriaceae harbouring a type I-inducible chromosomal β-lactamase. One-third of these VAP episodes were due to HL-AmpC-producing Enterobacteriaceae. Demographic and clinical characteristics at ICU admission were similar for patients, regardless of Enterobacteriaceae susceptibility, but those who developed VAP due to HL-AmpC-producing Enterobacteriaceae received antibiotics more frequently before its onset and had higher disease severity and organ dysfunction scores. Enterobacter spp. were the major HL-AmpC-producing micro-organisms responsible for VAP. VAP due to HL-AmpC-producing Enterobacteriaceae is rare. High level cephalosporin resistance was not associated with higher day 28 mortality, despite its association with more severe disease at VAP onset.

Antibiotic Use and Acquisition of Resistant Flora in Intensive Care Units

Patients in intensive care units (ICUs) can become colonized with antibiotic-resistant bacteria through cross-transmission, antibiotic-induced selection of preexisting low-level resistant bacteria, or de novo development of resistance during treatment. Which of these pathways is most prevalent for intestinal colonization with cephalosporin-resistant Enterobacteriaceae (CRE) or fluoroquinolone-resistant CRE (FCRE), and how do changes in antibiotic pressure affect such colonization? A recent crossover trial from the Netherlands …

Effects of reducing beta-lactam antibiotic pressure on intestinal colonization of antibiotic-resistant gram-negative bacteria

BackgroundWe determined the effects of two antibiotic policies (predominance of either β-lactam antibiotics or fluroquinolones) on acquisition with third-generation cephalosporin-resistant Enterobacteriaceae (CRE) and fluoroquinolone-resistant CRE (FCRE) in two ICUs, with monitoring of other variables that may influence acquisition.MethodsAfter an 8-month baseline period, units were randomized to a predominant β-lactam antibiotic regimen (weekly cycling of ceftriaxone, amoxicillin–clavulanic acid and fluroquinolones) or a fluoroquinolone regimen for 3 months, with cross-over for another 3 months. Acquisition of CRE and FCRE was determined by microbiological surveillance.ResultsDuring baseline, acquisition rates for CRE and FCRE were 14/1,000 and 2/1,000 patient days at risk, respectively. Cross-transmission of CRE accounted for ≤25% of acquisitions, and CRE acquisition was associated with the use of β-lactam antibiotics (amoxicillin–clavulanic acid in particular). As compared to baseline, β-lactam antibiotic use [in defined daily dose (DDD)/1,000 patient days] was reduced from 854 to 526 (−39%) and 555 (−35%) during both intervention periods. Fluoroquinolone use was increased from 150 and 129 DDD/1,000 patient days in baseline and the β-lactam period to 514 DDD/1,000 patient days (+243%) in the fluoroquinolone period. Reductions in β-lactam use were not associated with reduced CRE acquisition [adjusted HRs were 1.0 (95% CR: 0.5–2.2) and 1.1 (95% CI: 0.5–2.5) during both periods, respectively]. Increased use of fluoroquinolones was associated with increased acquisition of FCRE [adjusted HR 4.1 (95% CI: 1.4–11.9; p < 0.01]. Infection control variables remained comparable during all periods.ConclusionA 35–39% reduction of β-lactam exposure was not associated with reduced acquisition of CRE, whereas a 243% increase of fluoroquinolone use increased acquisition of FCRE.

Experience of European intensive care physicians with infections due to antibiotic-resistant bacteria, 2009

A survey was performed among European intensive care physicians to obtain information about their perception and experience with selected antibiotic-resistant bacteria. Seventy-eight out of 95 (82%) participants considered having to deal with infections due to antibiotic-resistant bacteria in the intensive care unit where they work was a major or significant problem. Methicillin-resistant Staphylococcus aureus (MRSA) and third-generation cephalosporin-resistant Enterobacteriaceae were the most frequently reported antibiotic-resistant bacteria with 69 (73%) and 67 (71%) participants reporting having treated at least one patient with such an infection during the preceding six months, respectively. Antibiotic-resistant Gram-negative bacteria, including carbapenem-resistant Enterobacteriaceae, were more frequently reported than any selected antibiotic-resistant Gram-positive bacteria, with the exception of MRSA. Fifty (53%) participants declared having treated at least one patient infected with a bacterium totally or almost totally resistant to available antibiotics during the past six months, with 8 participants having treated more than 10 such patients and 13 having treated from 3 to 10 such patients.

Bacterial resistance surveillance in China: a report from Mohnarin 2004–2005

The aim of this study was to establish a nationwide antimicrobial resistant surveillance network and obtain information on bacterial resistance in China. A total of 4075 clinical bacterial isolates were collected from 17 hospitals in 15 cities throughout China. Antibacterial minimal inhibitory concentrations (MICs) were determined by the standard agar dilution method recommended by Clinical and Laboratory Standards Institute. The results of the MICs revealed the following bacterial resistance characteristics. Oxacillin resistance was shown by 62.9% of Staphylococcus aureus and 82.89% of Staphylococcus epidermidis strains. Penicillin non-sensitivity was show by 40.7% of the Streptococcus pneumoniae strains, which included 10.5% penicillin-resistant strains and 30.2% penicillin-intermediate strains. Five strains of Enterococci were vancomycin-intermediate, but all Enterococci strains were sensitive to teicoplanin. All Staphylococci were susceptible to glycopeptides. A high resistance to macrolides was a predominant characteristic of the Gram-positive cocci. Enterobacteriaceae strains were clearly resistant to the third generation cephalosporins, with the exception of ceftazidime, and the resistance rates ranged from 20 to 70%. About 65% of the Escherichia coli strains were resistant to fluoroquinolones. Carbapenems remained highly active against all the target bacteria. Latamoxef, piperacillin/tazobactam, cefoperazone/sulbactam and cefepime were all active against Enterobacteriaceae, which showed resistant rates of less than 10%. Imipenem resistance was found in 10.6% of Pseudomonas aeruginosa and 10.4% of Acinetobacter baumannii strains, most of which were multidrug resistant isolates. Combinations of beta-lactam/beta-lactamase inhibitor and fluoroquinolones also had potent antibacterial activity against non-fermenters. Amikacin was active against Enterobacteriaceae and P. aeruginosa. In conclusion, methicillin-resistant Staphylococci, penicillin-insensitive S. pneumoniae, macrolides-resistant Gram-positive cocci, cephalosporin-resistant Enterobacteriaceae, multidrug-resistant nonfermenters and fluoroquinolone-resistant E. coli were revealed to be the most serious problems in terms of bacteria resistance in China. No glycopeptides-resistant Staphylococcus strains were isolated, and the appearance of glycopeptides-resistant Enterococci was seldom.

Characterization of TEM-, SHV- and AmpC-type β-lactamases from cephalosporin-resistant Enterobacteriaceae isolated from swine

Extended-spectrum β-lactamase (ESBL) and AmpC-producing Enterobacteriaceae are an increasing problem in human medicine and an emerging problem in the veterinary field. Our study, therefore, focused on assessing the prevalence of β-lactamases isolated from swine. Sixty-six Salmonella enterica serovar Typhimurium ( S. Typhimurium), 33 Salmonella enterica serovar Enteritidis ( S. Enteritidis), 26 Klebsiella pneumonia ( K. pneumoniae) and 130 Escherichia coli ( E. coli) pig isolates collected from 1999–2006 were screened for β-lactam resistance by the disk diffusion test (DDT) and micro-broth dilution. Among the isolates, five E. coli and five K. pneumoniae exhibited reduced susceptibility to the cephalosporins tested. PCR, plasmid profiling and Southern blot hybridization showed the presence of multiple β-lactamases in these isolates of animal origin. Hybridization patterns of the DHA-1 specific probe indicated that dissemination of DHA-1 related β-lactamases could be attributed to plasmids of one common size among the enteric microbes of animal origin. To the best of our knowledge, this study reports the first identification of SHV-28 and DHA-1 from microbes of animal origin.

Sequence analysis of bla CTX-M-28 , an ESBL responsible for third-generation cephalosporin resistance in Enterobacteriaceae, for the first time in India

The most common group of ESBLs not belonging to the bla TEM or bla SHV families were termed bla CTX-M , to highlight their ESBLs' greater activity against cefotaxime than against ceftazidime. The presence of nosocomial bla CTX-M-28 -producing Enterobacteriaceae strains has not been reported earlier in Indian hospitals. The sequences of bla CTX-M-28 gene from cephalosporin-resistant Enterobacteriaceae were analyzed. The structural gene encodes a 290 amino-acid protein, which is most related to the bla CTX-M beta-lactamases. The conserved K-T-G was identified in the bla CTX-M-28 protein sequence, but significantly, two point mutations (N-->T) and (F-->S) were identified in the Y-G-N- and S-T-F-K-conserved motifs respectively. These point mutations were seen in all the three sequenced isolates.

Healthcare-Associated Infection in Developing Countries: Simple Solutions to Meet Complex Challenges

From the World Alliance for Patient Safety, World Health Organization Headquarters (B.A.), and Infection Control Programme, University of Geneva Hospitals, Geneva, Switzerland (B.A., D.P.). Received June 11, 2007; accepted July 11, 2007; electronically published October 22, 2007. Infect Control Hosp Epidemiol 2007; 28:1323-1327 2007 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2007/2812-0002$15.00. DOI: 10.1086/521656 Healthcare-associated infections are usually linked to sophisticated medical technology and the use of invasive devices. Their potential impact on patient safety in developing countries is, therefore, perceived as incidental. Furthermore, in countries with an annual per capita income less than US$2,000 and where less than 5% of the gross national product is spent for health, infection control may be considered a luxury that uses resources needed for other very pressing health priorities. Available data seem to clearly demonstrate that this point of view is distorted and subject to bias. In developing countries, the unsafe use of injection equipment, other medical devices, and blood products; inadequate surgical procedures; and deficient biomedical waste management result in thousands of infections acquired not only from patients, but also from healthcare workers—most of them unreported. The World Health Organization (WHO) estimates that the proportion of injections given with syringes or needles that are reused without sterilization is between 1.5% and 69.4% in transitional and developing countries. In a survey conducted in 22 developing countries, the percentage of facilities not using proper waste disposal methods ranged from 18% to 64%. Furthermore, in 2000-2001, the WHO announced the alarming fact that more than 70 countries did not test all donated blood for human immunodeficiency virus, hepatitis B, hepatitis C, and syphilis. As a consequence, unsafe blood transfusions and injections result in an astounding number of new infections due to hepatitis B virus, hepatitis C virus, and human immunodeficiency virus every year (Table). In industrialized countries, healthcare-associated infection is a complication for between 5% and 10% of patients admitted to acute care hospitals. In developing countries, the risk of infection is 2-20 times higher, and the proportion of patients infected can exceed 25%. In a recent study in intensive care units (ICUs) in 8 developing countries, the overall device-associated infection rates were as high as 22.5 cases per 1,000 ICU-days, and the rates of specific device-associated infections exceeded by several times those reported in industrialized countries. Similarly, the rates of bloodstream infection in neonates are 3-20 times higher in developing countries, and, in some countries, approximately half of the patients in neonatal ICUs acquire an infection, and case fatality rates may reach 52%. In developed countries, between 2% and 5% of patients who undergo surgery develop a surgical site infection; in developing countries, much higher rates are reported, ranging from 12% to 39%. A complex range of factors determines the risk of acquiring an infection in healthcare settings in developing countries. The view that antimicrobial resistance substantially facilitates the spread of nosocomial pathogens is well known. In developing countries, inappropriate use of antibiotics and the use of counterfeit drugs contribute to very high resistance rates, although this is poorly documented because of the lack of reliable surveillance systems. In a report on neonatal ICU– acquired infections in different countries, 36% of Staphylococcus aureus isolates recovered were reported to be methicillin-resistant strains (MRSA), and 46% of Escherichia coli strains and 51% of Klebsiella species strains were resistant to third-generation cephalosporins. In adult ICU patients, MRSA accounted for 84% of healthcare-associated infections, and third-generation cephalosporin–resistant Enterobacteriaceae accounted for 51%. Understaffing and low levels of staff preparedness and knowledge are key factors leading to poor infection control in developing countries. The WHO Health Report 2006 revealed that worldwide, 57 countries (all developing) currently have critical staff shortages, equivalent to a global deficit of 2.4 million physicians, nurses, and midwives. Given this situation, the education and recruitment of infection control professionals is very far from being a realistic solution. Governments struggling with other well-known health priorities clearly are not primarily committed to developing infection control policies and standards. Several factors make the implementation of minimum standards for infection control very difficult, including poor hygiene and sanitation; lack or shortage of basic equipment, such as gloves; inadequate struc-

An Algorithm to Estimate the Importance of Bacterial Acquisition Routes in Hospital Settings

An algorithm is presented to calculate likelihoods of acquisition routes using only individual patient data concerning period of stay and microbiologic surveillance (without genotyping). The algorithm also produces estimates for the prevalence and the number of acquisitions by each route. The algorithm is applied to colonization data of third-generation cephalosporin-resistant Enterobacteriaceae (CRE) from September 2001 to May 2002 in two intensive care units (ICUs) (n = 277 and n = 180, respectively) of Utrecht, Kingdom of the Netherlands. Genotyping and epidemiologic linkage are used as the reference standard. Surveillance cultures were obtained on admission and twice weekly thereafter. All CREs were genotyped. According to the reference standard, the daily prevalence of CRE in ICU-1 and ICU-2 was 26.1% (standard deviation: 15.4) and 15.1% (standard deviation: 13.4), respectively, with five of 23 (21.7%) and six of 21 (28.6%) cases of acquired colonization being of exogenous origin, respectively. On the basis of the algorithm, the endogenous route was responsible for more acquisitions than the exogenous route (p = 0.003 and p < 0.001 for ICU-1 and ICU-2, respectively). The estimated number of acquisitions is 30 and 27, and the estimated prevalence is 27.6% and 17.6% for ICU-1 and ICU-2, respectively. By use of longitudinal colonization data only, the algorithm determines the relative importance of acquisition routes taking patient dependency into account.

Activity of faropenem against cephalosporin-resistant Enterobacteriaceae

There is a need for new oral agents active against extended-spectrum beta-lactamase (ESBL) producers, as these increasingly cause community-onset infections. We therefore evaluated faropenem, a penem in Phase III development, against recently collected oxyimino-cephalosporin-resistant bacteria. We tested 847 consecutive cephalosporin-resistant Enterobacteriaceae collected at 16 centres in South-East England in 2004, 501 of them with CTX-M enzymes; we also tested reference strains and transconjugants with acquired beta-lactamases and various modes of AmpC expression. MICs were determined by the BSAC agar dilution method. Modal MICs of faropenem for Escherichia coli or Klebsiella spp. with CTX-M or non-CTX-M ESBLs or high-level AmpC enzyme were 0.5-1 mg/L, with over 95% of producers susceptible to <or=2 mg/L. Modal MICs for Enterobacter and Citrobacter spp. with ESBLs or derepressed AmpC were 2-4 mg/L, although around 5% of AmpC-derepressed Enterobacter spp. required faropenem MICs of 16 mg/L. MICs of 8-16 mg/L were seen also for most AmpC-derepressed Serratia spp. isolates. Derepression of AmpC in isogenic mutant series typically raised faropenem MICs by one doubling dilution; among the beta-lactamases introduced into E. coli, only NMC-A (Class A) and IMP (Class B) carbapenemases caused substantive rises in faropenem MICs. Faropenem has good activity against E. coli and Klebsiella spp. with ESBLs, including the CTX-M types now proliferating in Europe, but was less active against AmpC-derepressed and ESBL-producing Enterobacter spp. Its clinical utility will depend on levels achieved in the urinary tract, the site of most of the community infections caused by ESBL producers, and more work is needed in this area.

Efficacy of practised screening methods for detection of cephalosporin-resistant Enterobacteriaceae

Enterobacteriaceae with extended-spectrum beta-lactamases (ESBLs) are now widespread and simple phenotypic tests are required to detect them in diagnostic laboratories. We investigated the performance of screening methods at 16 hospitals in South-East England. Sixteen laboratories in South-East England submitted 1195 consecutive Enterobacteriaceae isolates found to be resistant, by their routine methods, to any or all of cefpodoxime, ceftazidime and cefotaxime. These isolates were re-tested centrally with various cephalosporin/clavulanate combinations and with multiplex PCR for bla(CTX-M) and bla(AmpC) alleles. Screening methods among the laboratories were the following: cefpodoxime discs alone (1 site); cefpodoxime, cefotaxime and ceftazidime discs (9 sites) or agar dilution (1 site); Phoenix (2 sites), Vitek 1 (1 site) and Vitek 2 (2 sites). A total of 8% of isolates submitted based on disc tests proved fully cephalosporin-susceptible, compared with 3% sent based on tests with automated systems and none of those sent based on agar dilution tests. Among isolates submitted solely on cefpodoxime resistance 256/372 (69%) proved cephalosporin-susceptible or had only borderline resistance with no clear mechanism demonstrable; this proportion decreased to 28/160 (18%) for those submitted on the basis of resistance to ceftazidime, 18/122 (15%) for those resistant to cefotaxime and 26/496 (5%) for those resistant to both cefotaxime and ceftazidime. The inference of ESBL production by Vitek 2 had the best agreement with reference laboratory results. Many isolates found resistant only to cefpodoxime at the source sites proved not to have ESBLs or AmpC; screening with cefotaxime and ceftazidime allowed better specificity for identification of mechanism-based resistance, as did the automated systems. Cefpodoxime disc tests nevertheless remain a useful primary screen for laboratories prepared only to test one agent.

Prevalence and mechanisms of cephalosporin resistance in Enterobacteriaceae in London and South-East England

To investigate the molecular epidemiology of Enterobacteriaceae producing extended-spectrum beta-lactamases (ESBLs) in London and South-East England. A prospective study involving 16 hospital microbiology laboratories in London and South-East England was undertaken over a 12 week period. Each laboratory submitted up to 100 consecutive cephalosporin-resistant Enterobacteriaceae isolates judged clinically significant by microbiology staff. Centralized testing was undertaken to confirm organism identification and cephalosporin resistance and to analyse resistance mechanisms. The predominant mechanism of cephalosporin resistance in isolates from both hospital and community settings was the production of CTX-M-type ESBLs, with CTX-M-producing Escherichia coli as the most numerous resistant organism overall. Other major mechanisms of cephalosporin resistance included production of non-CTX-M ESBLs and AmpC beta-lactamases. Most ESBL (both CTX-M and non-CTX-M) producers were multiply resistant to non-beta-lactam antibiotics, including trimethoprim, ciprofloxacin and gentamicin. CTX-M enzymes, which were unrecorded in the UK prior to 2000, have become the major mechanism of cephalosporin resistance in Enterobacteriaceae in South-East England. E. coli has overtaken Klebsiella and Enterobacter spp. to become the major host for ESBLs. Due to the multiple antibiotic resistance exhibited by many ESBL-producers, these changes have major implications for antimicrobial therapy.