AbstractAntimicrobial Resistance Research Articles

Longitudinal Monitoring of Extended-Spectrum-Beta-Lactamase/AmpC-Producing Escherichia coli at German Broiler Chicken Fattening Farms

Antimicrobial resistance of Escherichia coli to modern beta-lactam antibiotics due to the production of extended-spectrum beta-lactamases (ESBL) and/or plasmid-mediated AmpC beta-lactamases (AmpC) represents an emerging and increasing resistance problem that dramatically limits therapeutic options in both human and veterinary medicine. The presence of ESBL/AmpC genes in commensal E. coli from food-producing animals like broilers may pose a human health hazard. However, there are no data available concerning the prevalence of ESBL/AmpC-producing E. coli in German broiler flocks using selective methods. In this longitudinal study, samples were taken from seven conventional broiler fattening farms at three different times within one fattening period. Various samples originating from the animals as well as from their direct environment in the barn were investigated for the occurrence of ESBL/AmpC-producing E. coli. Average detection levels of 51, 75, and 76% in animal samples collected during the three samplings in the course of the fattening period demonstrate a colonization of even 1-day-old chicks, as well as a continuous significant (P < 0.001) increase in prevalence thereafter. The detection frequencies in housing environmental samples were relatively high, with an increase over time, and ranged between 54.2 and 100%. A total of 359 E. coli isolates were characterized by PCR and partly via the disc diffusion method. This study shows that prevalence of ESBL/AmpC-producing E. coli increases during the fattening period of the broiler flocks examined. Both colonized day-old chicks and contaminated farm environments could represent significant sources of ESBL/AmpC-producing E. coli in German broiler fattening farms.

Next-Generation Antimicrobial Susceptibility Testing

Antimicrobial resistance has emerged as one of the most-significant health care problems of the new millennium, and the clinical microbiology laboratory plays a central role in optimizing the therapeutic management of patients with infection. This minireview explores the potential value of innovative methods for antimicrobial susceptibility testing of microorganisms that could provide valuable alternatives to existing methodologies in the very near future.

Prediction of Antimicrobial Activity of Synthetic Peptides by a Decision Tree Model

Antimicrobial resistance is a persistent problem in the public health sphere. However, recent attempts to find effective substitutes to combat infections have been directed at identifying natural antimicrobial peptides in order to circumvent resistance to commercial antibiotics. This study describes the development of synthetic peptides with antimicrobial activity, created in silico by site-directed mutation modeling using wild-type peptides as scaffolds for these mutations. Fragments of antimicrobial peptides were used for modeling with molecular modeling computational tools. To analyze these peptides, a decision tree model, which indicated the action range of peptides on the types of microorganisms on which they can exercise biological activity, was created. The decision tree model was processed using physicochemistry properties from known antimicrobial peptides available at the Antimicrobial Peptide Database (APD). The two most promising peptides were synthesized, and antimicrobial assays showed inhibitory activity against Gram-positive and Gram-negative bacteria. Colossomin C and colossomin D were the most inhibitory peptides at 5 μg/ml against Staphylococcus aureus and Escherichia coli. The methods described in this work and the results obtained are useful for the identification and development of new compounds with antimicrobial activity through the use of computational tools.

Reviewer Acknowledgement 2012

Contributing reviewersAntimicrobial Resistance and Infection Control would like to thank the following colleagues for their assistance with peer review of manuscripts for the journal in 2012.

Antibiotic Policy of India: Need to Act Now

Antimicrobial resistance has become a global challenge and needs to be tackled at the earnest. India lacks a functioning antibiotic policy and there is an urgent need to develop such a policy. A national antibiotic policy was published a couple of years back but lack of political will and complex practical issues have delayed its implementation. Various Indian medical societies have now put their efforts together for defining a roadmap to tackle the problem of infection control and prevention of antimicrobial resistance. A practicable functioning antibiotic policy is the need of the hour.

ASM Comments on Legislation Restricting Use of Antibiotics in Animal Feed

Antimicrobial resistance is spreading worldwide among bacteria that are pathogenic to humans—threatening public health and intensifying concern about the extensive use of antimicrobials in food production. There currently is a shortage of scientific data on the actual magnitude of antimicrobial resistance directly linked to agricultural use. But ASM believes there is sufficient evidence to demand a much closer, more thorough look at the potential effects of food production practices on our ability to treat human infections. It clearly is time for a coordinated, strongly science-based effort to minimize the negative effects of resistant pathogens.

English

Antimicrobial resistance among pathogenic organisms is now a persistent problem and of tremendous public health care concern around the globe. These pathogens are able to develop mechanisms of resistance, the antimicrobial agents that were at one time the drug of choice. They continue to develop various mechanisms of resistance either by intrinsic or acquired, and have been able to transfer and accept different resistance genes, given rise to multi-drugs resistance bacteria called superbugs. This new phenomenon has caused an increase in the incidence of nosocomial infections making the treatment problematic for the health care providers. Resistance to antimicrobial agents is fast becoming a norm and is an enormous challenge worldwide. Key words: Antimicrobial resistance, antimicrobial agent, pathogen, mechanism, superbug.

Changing Trends in Antimicrobial Resistance and Serotypes of Streptococcus pneumoniae Isolates in Asian Countries: an Asian Network for Surveillance of Resistant Pathogens (ANSORP) Study

Antimicrobial resistance in Streptococcus pneumoniae remains a serious concern worldwide, particularly in Asian countries, despite the introduction of heptavalent pneumococcal conjugate vaccine (PCV7). The Asian Network for Surveillance of Resistant Pathogens (ANSORP) performed a prospective surveillance study of 2,184 S. pneumoniae isolates collected from patients with pneumococcal infections from 60 hospitals in 11 Asian countries from 2008 to 2009. Among nonmeningeal isolates, the prevalence rate of penicillin-nonsusceptible pneumococci (MIC, ≥ 4 μg/ml) was 4.6% and penicillin resistance (MIC, ≥ 8 μg/ml) was extremely rare (0.7%). Resistance to erythromycin was very prevalent in the region (72.7%); the highest rates were in China (96.4%), Taiwan (84.9%), and Vietnam (80.7%). Multidrug resistance (MDR) was observed in 59.3% of isolates from Asian countries. Major serotypes were 19F (23.5%), 23F (10.0%), 19A (8.2%), 14 (7.3%), and 6B (7.3%). Overall, 52.5% of isolates showed PCV7 serotypes, ranging from 16.1% in Philippines to 75.1% in Vietnam. Serotypes 19A (8.2%), 3 (6.2%), and 6A (4.2%) were the most prominent non-PCV7 serotypes in the Asian region. Among isolates with serotype 19A, 86.0% and 79.8% showed erythromycin resistance and MDR, respectively. The most remarkable findings about the epidemiology of S. pneumoniae in Asian countries after the introduction of PCV7 were the high prevalence of macrolide resistance and MDR and distinctive increases in serotype 19A.

Update on antimicrobial resistance: mechanisms, methods and practice

Antimicrobial resistance is a major problem for hospitals and the community. This interactive session developed for trainees will explore current antimicrobial resistance issues pertinent to the laboratory, including detection and importance in determining mechanisms of resistance, screening, therapeutic implications and consequences for infection control.Four trainees will present illustrative cases of antimicrobial resistance (MRSA, VRE, multi-resistant Gram-negative organisms and Candida) followed by expert panel discussion. Dr John Merlino will deliver an update on hot topics in antimicrobial susceptibility testing and resistance in a ‘show and tell session’. Finally trainees and the expert panel will have an opportunity to discuss prepared questions on antimicrobial resistance issues.

Detection of mutations associated with multidrug-resistantMycobacterium tuberculosisclinical isolates

Antimicrobial resistance was studied in 100 Mycobacterium tuberculosis strains selected randomly from sputum cultures of newly diagnosed tuberculosis patients. Resistance of the isolates to rifampicin, isoniazid, and ethambutol was tested by both drug susceptibility testing (DST) and allele-specific PCR (AS-PCR). A total of 19 (19%) isolates were found resistant to at least one of the antituberculosis drugs investigated by PCR compared with 14 (14%) resistant isolates detected by DST. Eleven mutations were detected by AS-PCR in the rpoB gene (codons 516, 526, and 531), associated with rifampicin resistance, a marker of multidrug-resistant tuberculosis (MDR-TB), 14 mutations in the katG gene codon 315 that confers resistance to isoniazid, and nine mutations in the embB gene codon 306 that confers resistance to ethambutol. Mutations in the six multidrug-resistant isolates were confirmed by DNA sequencing. Results were compared with phenotypic DST data. Nineteen different mutation types to at least one of the drugs were found; six isolates (6%) were classified as MDR-TB, defined as resistance to at least rifampicin and isoniazid. The rates of concordance of the PCR with the phenotypic susceptibility test were 71.4, 54.5, and 44.4 for isoniazid, rifampicin, and ethambutol, respectively. These results highlight the importance of molecular epidemiology studies of tuberculosis in understudied regions with a tuberculosis burden to uncover the true prevalence of the MDR-TB.

Antimicrobial resistance pattern of gram negative bacteria to 3rd and 4th generation cephalosporins

Antimicrobial resistance (AMR) is increasing & the status in rural areas is less known. To find out the AMR pattern of clinical isolates of selected gram negative bacilli (GNB) to 3rd and 4thgeneration cephalosporins (GCPs) at a rural and urban tertiary care hospital.

Surveillance of health care workers for multidrug-resistant organisms in faecal samples in a tertiary care cancer centre

Antimicrobial resistance among nosocomial pathogens is a significant problem in most clinical settings adding to the cost of medical care and the morbidity and mortality of patients. Enterobacteriaceae carrying extended spectrum β-lactamases(ESBLs), Vancomycin resistant Enterococcus (VRE), methicillin resistant Staphylococcus aureus (MRSA) have emerged as significant pathogens. Many of the health care workers, who come in contact with patients regularly, are carriers of many of these organisms. They are potential source of transmission of these organisms. This study was undertaken to determine the extent of prevalence of faecal carriers of multi-drug resistant organisms among health care workers.

Selected mutli-drug-resistance-organisms in selected Polish long-term-care facilities*

Nosocomial infections and antimicrobial resistance (AR) are a very well-known public health problems. Unfortunately, up to now there is no surveillance of AR in Polish long term care facilities (LTCF). The aim of this presentation was to analyze prevalence of selected Multi-Drug-Resistance-Organisms (MDRO) among residents of LTCFs in Krakow, Poland.

Implementation of e-Bug in Belgium

Antimicrobial resistance is an important issue in Belgium. For more than a decade, national projects aiming to promote the prudent use of antimicrobials and to decrease antimicrobial resistance in ambulatory, nursing-home and hospital settings have been launched by the Belgian Antibiotic Policy Coordination Committee (BAPCOC), coordinated by the Federal Public Service of Public Health, Food Chain Safety and Environment. In this paper, we describe the implementation of the e-Bug Project in Belgium by the University of Antwerp in collaboration with BAPCOC and supported by the Ministries of Education, and how e-Bug complemented a new national campaign focusing on antibiotic use in children first started on the European Antibiotic Awareness Day in 2008. We also describe the impact of the organization of education in Belgium on the implementation process, as well as plans for the future of e-Bug in our country.

Status report on carbapenemases: challenges and prospects

Antimicrobial resistance in hospital and community-onset bacterial infections is a significant source of patient morbidity and mortality. In the past decade, we have witnessed the increasing recovery of carbapenem-resistant Gram-negative bacteria. For many isolates, carbapenem resistance is due to the production of carbapenemases, β-lactamases that can inactivate carbapenems and frequently other β-lactam antibiotics. Currently, these enzymes are mainly found in three different β-lactamase classes (class A, B and D). Regardless of the molecular classification, there are few antimicrobials available to treat infections with these organisms and data regarding agents in development are limited to in vitro studies. This article focuses on the epidemiology of carbapenemase-producing Gram-negative bacteria. We also review available agents and those in development with potential activity against this evolving threat.

Antimicrobial resistance: the global public health challenge

Antimicrobial resistance is one of the biggest challenges faced by public health at the beginning of the third millennium. The global presence of antimicrobial resistance is threatening the continued effectiveness of many current medications. Antibiotic resistance is usually associated with significant morbidity, longer hospitalization, excess costs and mortality. Many factors contribute to the unnecessary use of antibiotics including the phenomenal knowledge boom, direct patient requests, perceptions of patient demand, culture and norms and advertisements and other promotional literature. Self-medication with antimicrobials is often cited as a major factor contributing to drug resistance. The microorganisms employ several mechanisms in attaining multidrug resistance such as they lack of reliance on the glycoprotein cell wall; enzymatic deactivation of antibiotics, decreased cell wall permeability to antibiotics and altered target sites of antibiotic. Efflux mechanisms to remove antibiotics and increased mutation rate are some of the other important mechanism for the antimicrobial resistance. Optimal use of existing antimicrobial agents, using alternative treatment options, reducing the need for antimicrobials by increasing immunity, education of health professionals and patients, antibiotic policies and implementation of infection control measures are the strategies aimed at prevention of emergence and spread of antibiotic resistance.

Cefpodoxime 10 μg disc screening test for detection of Neisseria gonorrhoeae with mosaic PBP2 and decreased susceptibility to extended-spectrum cephalosporins for public health purposes

Antimicrobial resistance (AMR) in Neisseria gonorrhoeae remains a global public health problem. Susceptibility to first-line treatment extended-spectrum cephalosporins (ESCs) is decreasing worldwide resulting in therapeutic failures with oral ESCs. This study describes a cefpodoxime 10 μg disc test for screening for gonococci containing a penA mosaic allele encoding a mosaic penicillin-binding protein 2 (PBP2) and decreased ESC susceptibility. Selected clinical gonococcal isolates (n = 315), containing a high proportion of gonococci with decreased ESC susceptibility and high geographical, temporal and genetic diversity, were examined using agar dilution (n = 149; cefpodoxime and ceftriaxone) and Etest (n = 315; cefixime), and disc diffusion using a commercially available cefpodoxime 10 μg disc (n = 315). penA sequencing was performed on all isolates. The 2008 WHO gonococcal reference strains (n = 8) were included as quality controls. Using a ≤11 mm annular radius of growth inhibition as the breakpoint for the cefpodoxime 10 μg disc, all 78, with exception of one isolate (13 mm), mosaic PBP2-containing isolates, which also displayed decreased susceptibility to oral ESCs, were identified. In addition, 85 non-mosaic PBP2-containing isolates (44% of which contained a PBP2 A501 alteration) had annular radii ≤11 mm and raised minimal inhibitory concentrations to the ESCs. Screening for detection of mosaic PBP2-containing gonococci and decreased ESC susceptibility, most pronounced to oral ESCs, using a commercially available cefpodoxime 10 μg disc was rapid, inexpensive and sensitive. This test can be used in AMR surveillance programmes for public health purposes especially in less-resourced settings. Further studies to refine this disc testing-based approach are in progress.

Clinical Impact of Antimicrobial Resistance in European Hospitals: Excess Mortality and Length of Hospital Stay Related to Methicillin-Resistant Staphylococcus aureus Bloodstream Infections

Antimicrobial resistance is threatening the successful management of nosocomial infections worldwide. Despite the therapeutic limitations imposed by methicillin-resistant Staphylococcus aureus (MRSA), its clinical impact is still debated. The objective of this study was to estimate the excess mortality and length of hospital stay (LOS) associated with MRSA bloodstream infections (BSI) in European hospitals. Between July 2007 and June 2008, a multicenter, prospective, parallel matched-cohort study was carried out in 13 tertiary care hospitals in as many European countries. Cohort I consisted of patients with MRSA BSI and cohort II of patients with methicillin-susceptible S. aureus (MSSA) BSI. The patients in both cohorts were matched for LOS prior to the onset of BSI with patients free of the respective BSI. Cohort I consisted of 248 MRSA patients and 453 controls and cohort II of 618 MSSA patients and 1,170 controls. Compared to the controls, MRSA patients had higher 30-day mortality (adjusted odds ratio [aOR] = 4.4) and higher hospital mortality (adjusted hazard ratio [aHR] = 3.5). Their excess LOS was 9.2 days. MSSA patients also had higher 30-day (aOR = 2.4) and hospital (aHR = 3.1) mortality and an excess LOS of 8.6 days. When the outcomes from the two cohorts were compared, an effect attributable to methicillin resistance was found for 30-day mortality (OR = 1.8; P = 0.04), but not for hospital mortality (HR = 1.1; P = 0.63) or LOS (difference = 0.6 days; P = 0.96). Irrespective of methicillin susceptibility, S. aureus BSI has a significant impact on morbidity and mortality. In addition, MRSA BSI leads to a fatal outcome more frequently than MSSA BSI. Infection control efforts in hospitals should aim to contain infections caused by both resistant and susceptible S. aureus.

Antimicrobial resistance of thermotolerant Campylobacter spp. as a food safety issue

Antimicrobial resistance is a daunting public health threat impacting both human and animal health and it is a cause for concern wherever antimicrobial agents are in use. The usage of antimicrobial drugs in food producing animals could results in significant food safety issue - antimicrobial resistance among zoonotic bacteria in these animals. Resistance monitoring program still does not exist in Serbia, so we made a pilot program to screen the situation in our abattoirs. We found similar situation like the one in EU. The resistance to one or more antimicrobial drugs was found in 40.00% and 75.32% Campylobacter spp. strains isolated from poultry and pig carcasses, respectively. Fluoroquinolones are anitmicrobial drugs which, beside beta-lactams, are most often used in poultry breeding. Fluoroquinolones are also very important for treatment of some human diseases. We examined relationship between presence of fluoroquinolone resistant C. jejuni in poultry carcasses and fluoroquinolone treatment of poultry. Treatment with one of this antimicrobials - enrofloxacine selects resistant strains in chickens carcasses, C. jejuni strains resistant to enrofloxacine were isolated from all livers (100%) and 70% carcasses. The resistant bacteria may then be transmitted to humans through food supply and increase the risk of treatment failures. Resistant zoonotic pathogens in food have to be controlled through a complete, continuous farm-to-fork system.

Antimicrobial Resistance in Swiss Laying Hens, Prevalence and Risk Factors

Antimicrobial resistance is an emerging concern to public health, and food-producing animals are known to be a potential source for transmission of resistant bacteria to humans. As legislation of the European Union requires to ban conventional cages for the housing of laying hens on the one hand, and a high food safety standard for eggs on the other hand, further investigations about the occurrence of antimicrobial resistance in alternative housing types are required. In this study, we determined antimicrobial resistance in indicator bacteria from 396 cloacal swabs from 99 Swiss laying hen farms among four alternative housing types during a cross-sectional study. On each farm, four hens were sampled and exposure to potential risk factors was identified with a questionnaire. The minimal inhibitory concentration was determined using broth microdilution in Escherichia coli (n=371) for 18 antimicrobials and in Enterococcus faecalis (n=138) and Enterococcus faecium (n=153) for 16 antimicrobials. All antimicrobial classes recommended by the European Food Safety Authority for E. coli and enterococci were included in the resistance profile. Sixty per cent of the E. coli isolates were susceptible to all of the considered antimicrobials and 30% were resistant to at least two antimicrobials. In E. faecalis, 33% of the strains were susceptible to all tested antimicrobials and 40% were resistant to two or more antimicrobials, whereas in E. faecium these figures were 14% and 39% respectively. Risk factor analyses were carried out for bacteria species and antimicrobials with a prevalence of resistance between 15% and 85%. In these analyses, none of the considered housing and management factors showed a consistent association with the prevalence of resistance for more than two combinations of bacteria and antimicrobial. Therefore we conclude that the impact of the considered housing and management practices on the egg producing farms on resistance in laying hens is low.