Properties of plasmids responsible for production of extended-spectrum beta-lactamases

Solid waste dumpsite leachate and contiguous surface water contain multidrug-resistant ESBL-producing Escherichia coli carrying Extended Spectrum β-Lactamase (ESBL) genes

Dumpsites generate leachates containing bacteria that may carry antibiotic resistance genes, such as extended spectrum β-lactamase (ESBL). However, the contribution of dumpsite leachates in the environmental spread of ESBL genes has not been investigated in greater detail. This study aimed to quantify the impact of Ajakanga dumpsite leachate on the spread of ESBL genes through surface water. The susceptibility of Escherichia coli isolated from dumpsite leachate and the accompanying surface water to selected antibiotics was assessed by the standardized disc diffusion method. The isolates were evaluated for phenotypic ESBL production using the double disc synergy test (DDST). The detection of ESBL genes in the isolates was carried out using a primer-specific polymerase chain reaction (PCR). Escherichia coli isolates from leachate (n = 26/32) and surface water (n = 9/12) expressed ESBL phenotype. The ESBL-producing isolates showed the highest level of resistance to the 3rd generation cephalosporin antibiotics: cefotaxime (100%), cefpodoxime (97%), ceftazidime (97%), with low resistance observed to imipenem (6%) and azithromycin (3%). All the isolates were multidrug-resistant, showing resistance to three or more classes of antibiotics. All the ESBL-producing E. coli obtained carried blaCTX-M, 21/35 (60%) carried blaTEM while none of the isolates bore blaSHV. This study found that ESBL-producing Escherichia coli from dumpsite leachate and nearby surface water had identical resistance signatures indicating the relatedness of the isolates, and that dumpsite leachate could contribute to the transfer of ESBL-producing bacteria and their genes to receiving surface water. This study has necessitated the need for a review of the guidelines and operational procedures of dumpsites to forestall a potential public health challenge.

Plasmid-Encoded Traits Vary across Environments

Plasmids are key mobile genetic elements in bacterial evolution and ecology as they allow the rapid adaptation of bacteria under selective environmental changes. However, the genetic information associated with plasmids is usually considered separately from information about their environmental origin. To broadly understand what kinds of traits may become mobilized by plasmids in different environments, we analyzed the properties and accessory traits of 9,725 unique plasmid sequences from a publicly available database with known bacterial hosts and isolation sources. Although most plasmid research focuses on resistance traits, such genes made up <1% of the total genetic information carried by plasmids. Similar to traits encoded on the bacterial chromosome, plasmid accessory trait compositions (including general Clusters of Orthologous Genes [COG] functions, resistance genes, and carbon and nitrogen genes) varied across seven broadly defined environment types (human, animal, wastewater, plant, soil, marine, and freshwater). Despite their potential for horizontal gene transfer, plasmid traits strongly varied with their host's taxonomic assignment. However, the trait differences across environments of broad COG categories could not be entirely explained by plasmid host taxonomy, suggesting that environmental selection acts on the plasmid traits themselves. Finally, some plasmid traits and environments (e.g., resistance genes in human-related environments) were more often associated with mobilizable plasmids (those having at least one detected relaxase) than others. Overall, these findings underscore the high level of diversity of traits encoded by plasmids and provide a baseline to investigate the potential of plasmids to serve as reservoirs of adaptive traits for microbial communities. IMPORTANCE Plasmids are well known for their role in the transmission of antibiotic resistance-conferring genes. Beyond human and clinical settings, however, they disseminate many other types of genes, including those that contribute to microbially driven ecosystem processes. In this study, we identified the distribution of traits genetically encoded by plasmids isolated from seven broadly categorized environments. We find that plasmid trait content varied with both bacterial host taxonomy and environment and that, on average, half of the plasmids were potentially mobilizable. As anthropogenic activities impact ecosystems and the climate, investigating and identifying the mechanisms of how microbial communities can adapt will be imperative for predicting the impacts on ecosystem functioning.

Genetic Relationship between Salmonella Isolates Recovered from Calves and Broilers Chickens in Kafr El-Sheikh City Using ERIC PCR

A prevalent bacterial intestinal infection with severe economic damage is salmonellosis. Our study was carried out to diagnose Salmonella from chickens and calves, to determine its resistance to antimicrobials' phenotypic and genotypic characterization of integrons and β lactamase genes in the multidrug resistance of different Salmonella serotypes, and to detect the genetic relationship between Salmonella isolates collected from different origins using an ERIC PCR. In total, 200 samples from diseased chicken and diarrheic calves were obtained from 50 various farms from Kafr El-sheikh, Egypt. Salmonella poultry isolates were characterized as S. Typhimurium (3/8), S. Enteritidis (3/8), and S. Kentucky (2/8), but Salmonella isolates from cattle were S. Enteritidis (1/2) and S. Kentucky (1/2). When antibiotic susceptibility testing was completed on all of the isolates, it showed that there was multidrug resistance present (MDR). A PCR was applied for identifying the accompanying class 1 integrons and ESBLs from MDR Salmonella isolates (two isolates of S. Kentucky were divided as one from calf and one from poultry). Our results detected blaTEM and class 1 integron, but were negative for bla IMP, bla VIM, and bla SHV. An ERIC PCR was conducted for understanding the clonal relation between various β-lactamase-producing MDR Salmonella isolates. The same four previously mentioned isolates were also tested. The two isolates of S. Enteritidis isolated from poultry and calves had 100% similarity despite indicating that there were interactions between broilers and calves living on the same farm that caused infection from the same Salmonella strains, while the other two isolates of S. Kentucky showed only 33% serovarities.

Antimicrobial Resistance Genes in ESBL-Producing Escherichia coli Isolates from Animals in Greece

The prevalence of multidrug resistant, extended spectrum β-lactamase (ESBL)-producing Enterobacteriaceae is increasing worldwide. The present study aimed to provide an overview of the multidrug resistance phenotype and genotype of ESBL-producing Escherichia coli (E. coli) isolates of livestock and wild bird origin in Greece. Nineteen phenotypically confirmed ESBL-producing E. coli strains isolated from fecal samples of cattle (n = 7), pigs (n = 11) and a Eurasian magpie that presented resistance to at least one class of non β-lactam antibiotics, were selected and genotypically characterized. A DNA-microarray based assay was used, which allows the detection of various genes associated with antimicrobial resistance. All isolates harbored blaCTX-M-1/15, while blaTEM was co-detected in 13 of them. The AmpC gene blaMIR was additionally detected in one strain. Resistance genes were also reported for aminoglycosides in all 19 isolates, for quinolones in 6, for sulfonamides in 17, for trimethoprim in 14, and for macrolides in 8. The intI1 and/or tnpISEcp1 genes, associated with mobile genetic elements, were identified in all but two isolates. This report describes the first detection of multidrug resistance genes among ESBL-producing E. coli strains retrieved from feces of cattle, pigs, and a wild bird in Greece, underlining their dissemination in diverse ecosystems and emphasizing the need for a One-Health approach when addressing the issue of antimicrobial resistance.

Phage phiKZ-The First of Giants

The paper covers the history of the discovery and description of phiKZ, the first known giant bacteriophage active on Pseudomonas aeruginosa. It also describes its unique features, especially the characteristic manner of DNA packing in the head around a cylinder-shaped structure ("inner body"), which probably governs an ordered and tight packaging of the phage genome. Important properties of phiKZ-like phages include a wide range of lytic activity and the blue opalescence of their negative colonies, and provide a background for the search and discovery of new P. aeruginosa giant phages. The importance of the phiKZ species and of other giant phage species in practical phage therapy is noted given their broad use in commercial phage preparations.

Antimicrobial resistance in hospitalized surgical patients: a silently emerging public health concern in Benin

BACKGROUND

Surgical site infections are related to high morbidity, mortality and healthcare costs. Because the emergence of multidrug-resistant bacteria in hospitals is becoming a worldwide challenge for surgeons who treat healthcare-associated infections, we wished to identify the causative agents involved in these infections and the rate of multidrug-resistant bacteria in six public hospitals in Benin.

METHODS

Using standard microbiological procedures, we processed pus specimens collected from obstetrics and gastrointestinal surgery wards. Mass spectrometry (MALDI-TOF) was used for confirmation. For the antibiotic susceptibility test, we first used the Kirby-Bauer disk diffusion method. The secondary test (by microdilution) used the Beckton Dickinson Phoenix automated system (Becton Dickinson Diagnostic, USA).

RESULTS

We included 304 patients, whose median length of stay was 9 days. A total of 259 wound swabs (85.2%) had positive aerobic bacterial growth. In obstetrics, S. aureus (28.5%, n = 42) was the most common isolate. In contrast, Gram-negative bacteria (GNB) were predominant in gastrointestinal surgery, the most dominant being E.coli (38.4%, n = 31). Overall, 90.8% (n = 208) of aerobic bacteria were multidrug resistant. Two-thirds of S. aureus (65.3%, n = 32) were methicillin-resistant Staphylococcus aureus (MRSA), three of which carried both MRSA and induced clindamycin resistance (ICR). GNB showed high resistance to ceftazidime, ceftriaxone and cefepime. Extended-spectrum beta-lactamases were presented by 69.4% of E.coli (n = 43/62) and 83.3% of K. pneumoniae (n = 25/30). Overall, twelve Gram-negative bacteria (5.24%) showed resistance to at least one carbapenem. No isolates showed a wild-type susceptible phenotype.

CONCLUSION

This study shows the alarming prevalence of multidrug-resistant organisms from surgical site infections in Benin hospitals. To reduce the spread of such bacteria in Benin, periodic surveillance of surgical site infections and strict adherence to good hand-hygiene practice are essential.

Antimicrobial Resistance Pattern of Escherichia coli Isolated from Frozen Chicken Meat in Bangladesh

Escherichia coli is known as one of the most important foodborne pathogens in humans, and contaminated chicken meat is an important source of foodborne infection with this bacterium. The occurrence of extended-spectrum β-lactamase (ESBL)-producing E. coli (ESBL-Ec), in particular, in chicken meat is considered a global health problem. This study aimed to determine the magnitude of E. coli, with special emphasis on ESBL-Ec, along with their phenotypic antimicrobial resistance pattern in frozen chicken meat. The study also focused on the determination of ESBL-encoding genes in E. coli. A total of 113 frozen chicken meat samples were purchased from 40 outlets of nine branded supershops in five megacities in Bangladesh. Isolation and identification of E. coli were done based on cultural and biochemical properties, as well as PCR assay. The resistance pattern was determined by the disc diffusion method. ESBL-encoding genes were determined by multiplex PCR. The results showed that 76.1% of samples were positive for E. coli, of which 86% were ESBL producers. All the isolates were multidrug-resistant (MDR). Resistance to 9-11 and 12-13 antimicrobial classes was observed in 38.4% and 17.4% isolates, respectively, while only 11.6% were resistant to 3-5 classes. Possible extensive drug resistance (pXDR) was found in 2.3% of isolates. High single resistance was observed for oxytetracycline (93%) and amoxicillin (91.9%), followed by ampicillin (89.5%), trimethoprim-sulfamethoxazole, and pefloxacin (88.4%), and tetracycline (84.9%). Most importantly, 89.6% of isolates were resistant to carbapenems. All the isolates were positive for the blaTEM gene. However, the blaSHV and blaCTX-M-2 genes were identified in two ESBL-non producer isolates. None of the isolates carried the blaCTX-M-1 gene. This study provided evidence of the existence of MDR and pXDR ESBL-Ec in frozen chicken meat in Bangladesh, which may pose a risk to human health if the meat is not properly cooked or pickled raw only. This emphasizes the importance of the implementation of good slaughtering and processing practices by the processors.

Molecular characterization of virulence and drug resistance genes-producing Escherichia coli isolated from chicken meat: Metal oxide nanoparticles as novel antibacterial agents

Escherichia coli is a major global foodborne pathogen, infecting a wide range of animals and contaminating their meat products. E. coli, can lead to high morbidity and mortality with a huge economic loss especially if foodborne diseases are associated with multidrug resistant (MDR)- and multivirulent-producing pathogens. Due to the increased resistance to common antimicrobials used to treat livestock animals and human infections, the discovery of new and innovative nanomaterials are in high demand. Recently, metal oxides can be considered as effective inorganic agents with antimicrobial features. Hence, this study might be the first to evaluate the efficiency of metal oxide nanoparticles (MO-NPs) as novel antibacterial agents against MDR/multivirulent E. coli pathogens isolated from chicken meat. The occurrence of pathogenic E. coli was determined in fresh warm chicken meat parts (breast, thigh, liver and gizzard). Ninety-one of 132 (69%) chicken meat parts were Escherichia -positive with E. coli as the only species isolated. Out of identified 240 E. coli strains, 72.5% (174/240) were classified as MDR E. coli strains. Fifty-five profile patterns were obtained. From each pattern, one strain was randomly selected for further analysis of virulence and resistance genes. Extracted DNA was assessed for the presence of antibiotic resistance genes (bla_IMP-7, bla_IMP-25, bla_TEM, bla_SHV, bla_OXA-2, tetA, aadA, and aac(3)-IV) and virulence genes (stx1, stx2, hlyA, eaeA, aggR, eltB, estIb, papA, afa and hlyD). Clustering analyses revealed that 10 E. coli harboring the highest number of virulence and resistance genes were shifted together into one cluster designated as cluster X. The average activities of zinc peroxide nanoparticles (ZnO₂-NPs) were higher than that of zinc oxide nanoparticles (ZnO-NPs) and titanium dioxide nanoparticles (TiO₂-NPs) by 20% and 29%, respectively. The anti-inflammatory activity of ZnO₂-NPs in comparison with aspirin was assessed using membrane stabilization, albumin denaturation, and proteinase inhibition methods. Significant anti-inflammatory activity of ZnO₂-NPs was achieved at concentration levels of 500-1000 μg/ml. It seems that MO-NPs are effective alternative agents, since they exhibited a competitive antibacterial capability against MDR/multivirulent-producing E. coli pathogens isolated from chicken meat. Hence, ZnO₂-NPs are a promising nanoparticles-based material for controlling foodborne pathogens, thereby valued for food safety applications.

Limited contribution of non-intensive chicken farming to ESBL-producing Escherichia coli colonization in humans in Vietnam: an epidemiological and genomic analysis

OBJECTIVES

To investigate the risk of colonization with ESBL-producing Escherichia coli (ESBL-Ec) in humans in Vietnam associated with non-intensive chicken farming.

METHODS

Faecal samples from 204 randomly selected farmers and their chickens, and from 306 age- and sex-matched community-based individuals who did not raise poultry were collected. Antimicrobial usage in chickens and humans was assessed by medicine cabinet surveys. WGS was employed to obtain a high-resolution genomic comparison between ESBL-Ec isolated from humans and chickens.

RESULTS

The adjusted prevalence of ESBL-Ec colonization was 20.0% (95% CI 10.8%-29.1%) and 35.2% (95% CI 30.4%-40.1%) in chicken farms and humans in Vietnam, respectively. Colonization with ESBL-Ec in humans was associated with antimicrobial usage (OR = 2.52, 95% CI = 1.08-5.87) but not with involvement in chicken farming. blaCTX-M-55 was the most common ESBL-encoding gene in strains isolated from chickens (74.4%) compared with blaCTX-M-27 in human strains (47.0%). In 3 of 204 (1.5%) of the farms, identical ESBL genes were detected in ESBL-Ec isolated from farmers and their chickens. Genomic similarity indicating recent sharing of ESBL-Ec between chickens and farmers was found in only one of these farms.

CONCLUSIONS

The integration of epidemiological and genomic data in this study has demonstrated a limited contribution of non-intensive chicken farming to ESBL-Ec colonization in humans in Vietnam and further emphasizes the importance of reducing antimicrobial usage in both human and animal host reservoirs.

Prevalence, antimicrobial resistance and virulence genes of Escherichia coli isolated from retail meat in Tamaulipas, Mexico

OBJECTIVES

The aim of this study was to determinate the prevalence of Escherichia coli and its resistance to antimicrobials and the presence of virulence genes in retail samples of beef and pork in several locations in Tamaulipas, Mexico.

METHODS

A total of 106 samples (54 beef and 52 pork) collected from August 2013 to March 2014 were analysed to detect E. coli isolates. The E. coli isolates were then analysed for detection of virulence factors and antimicrobial resistance genes. Antimicrobial susceptibility to 16 antimicrobial agents was also determined.

RESULTS

A total of 158 E. coli isolates were obtained, among which 3 (1.9%) harboured the virulence gene stx1, 28 (17.7%) harboured stx2 and 34 (21.5%) harboured hlyA. High phenotypic resistance was observed in almost all isolates, since 146 (92.4%) showed a multiresistant phenotype with resistance to cefalotin (92%), ampicillin (92%), cefotaxime (78%), nitrofurantoin (76%) and tetracycline (75%). The antimicrobial resistance genes tet(A) and tet(B) were detected in 56% of isolates, strA in 9.6%, aadA in 17% and aac(3)-IV in only 0.6% of strains.

CONCLUSIONS

Based on these results, it can be concluded that retail beef and pork meat may play a role in the spread of antimicrobial-resistant E. coli strains in this region.

Colonization, Infection, and the Accessory Genome of Klebsiella pneumoniae

Klebsiella pneumoniae is a Gram-negative pathogen that has a large accessory genome of plasmids and chromosomal gene loci. This accessory genome divides K. pneumoniae strains into opportunistic, hypervirulent, and multidrug-resistant groups and separates K. pneumoniae from two closely related species, Klebsiella variicola and Klebsiella quasipneumoniae. Some strains of K. pneumoniae act as opportunistic pathogens, infecting critically ill and immunocompromised patients. These K. pneumoniae are a common cause of health-care associated infections including pneumonia, urinary tract infections (UTIs), and bloodstream infections. K. variicola and K. quasipneumoniae are often clinically indistinguishable from opportunistic K. pneumoniae. Other strains of K. pneumoniae are hypervirulent, infecting healthy people in community settings and causing severe infections including pyogenic liver abscess, endophthalmitis, and meningitis. A third group of K. pneumoniae encode carbapenemases, making them highly antibiotic-resistant. These strains act as opportunists but are exceedingly difficult to treat. All of these groups of K. pneumoniae and related species can colonize the gastrointestinal tract, and the accessory genome may determine if a colonizing strain remains asymptomatic or progresses to cause disease. This review will explore the associations between colonization and infection with opportunistic, antibiotic-resistant, and hypervirulent K. pneumoniae strains and the role of the accessory genome in distinguishing these groups and related species. As K. pneumoniae infections become progressively more difficult to treat in the face of antibiotic resistance and hypervirulent strains, an increased understanding of the epidemiology and pathogenesis of these bacteria is vital.

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.

Persistence and reversal of plasmid-mediated antibiotic resistance

In the absence of antibiotic-mediated selection, sensitive bacteria are expected to displace their resistant counterparts if resistance genes are costly. However, many resistance genes persist for long periods in the absence of antibiotics. Horizontal gene transfer (primarily conjugation) could explain this persistence, but it has been suggested that very high conjugation rates would be required. Here, we show that common conjugal plasmids, even when costly, are indeed transferred at sufficiently high rates to be maintained in the absence of antibiotics in Escherichia coli. The notion is applicable to nine plasmids from six major incompatibility groups and mixed populations carrying multiple plasmids. These results suggest that reducing antibiotic use alone is likely insufficient for reversing resistance. Therefore, combining conjugation inhibition and promoting plasmid loss would be an effective strategy to limit conjugation-assisted persistence of antibiotic resistance.

It is unclear whether the transfer of plasmids carrying antibiotic resistance genes can explain their persistence when antibiotics are not present. Here, Lopatkin et al. show that conjugal plasmids, even when costly, are indeed transferred at sufficiently high rates to be maintained in the absence of antibiotics.

Beta-lactam and quinolone resistance markers in uropathogenic strains isolated from renal transplant recipients

Our objectives were to investigate the extended-spectrum beta-lactamases (ESBLs) and carbapenemases (CR) genetic determinants and to assess the association between ESBL production and quinolone resistance in bacterial strains isolated from renal transplant recipients with urinary tract infections. Material and methods: A number of 30 isolates were recovered from urine specimens of patients with renal transplant from October 2015 to March 2016. The isolates were analyzed for ESBL production using double disc synergy test and for CR production by the Hodge test. Phenotypically confirmed isolates were screened by PCR for the identification of ESBL, CR and fluoroquinolone resistance genes. Results: The 30 clinical bacterial strains isolated from urinary tract infections in renal transplant recipients were identified as Klebsiella pneumoniae (17), Pseudomonas aeruginosa (7), Morganella morganii (2), Escherichia coli (2), Edwardsiella tarda (1) and Enterobacter cloacae (1). Out of them, 22 isolates were ESBL producers and 20 multi-drug resistant (MDR) (i.e., 13 K. pneumoniae and 7 P. aeruginosa strains). More than half of the ESBL clinical strains (14/22, 63.63%) revealed at least one ESBL gene, the most frequent being blaCTX-M type (18/22, 81.81%), either alone (4/22, 18.18%) or in combination with another ESBL gene (17/22, 77.27%), followed by blaTEM (13/22, 59.09%). The blaOXA-48 was present in 10 isolates (33.33%). The most frequent association of ESBLs and CR genes (5/14, 35.71%) was revealed by blaCTX-M- blaTEM - blaOXA-48, encountered particularly among K. pneumoniae isolates (4/17, 23.52%). The qnrB gene was identified in five strains, i.e. one P. aeruginosa ESBL isolate (expressing the blaCTX-M gene) and four K. pneumoniae ESBL isolates (harboring the blaCTX-M - blaTEM genes combination). Conclusions: The uropathogenic strains isolated from renal transplant recipients exhibited high rates of MDR and beta-lactam resistance. The selective pressure exerted by quinolones could enable uropathogenic bacteria to acquire resistance to this class of antibiotics.

Extended spectrum β-lactamase producing Escherichia coli and Klebsiella pneumoniae: critical tools for antibiotic resistance pattern

Drug resistance is a phenomenon where by an organism becomes fully or partially resistant to drugs or antibiotics being used against it. Antibiotic resistance poses an exacting intimidation for people with underlying medical immune conditions or weakened immune systems. Infections caused by the enzyme extended spectrum β-lactamase (ESBL) producing multi drug resistance (MDR) Enterobacteriaceae especially Escherichia coli and Klebsiella pneumoniae are resistant to a broad range of beta lactams, including third generation cephalosporins. Among all the pathogens, these two MDR E. coli and K. pneumoniae have emerged as one of the world's greatest health threats in past two decades. The nosocomial infections caused by these ESBL producing MDR E. coli and K. pneumoniae complicated the therapy and limit treatment options.

Antimicrobial Susceptibility Pattern of Extended-spectrum Beta-lactamases Producing Organisms Isolated in a Tertiary Care Hospital, Bangladesh

Context:

Infection caused by extended-spectrum beta-lactamases (ESBL) producing organism is a major problem regarding antibiotic resistance.

Aims:

The aim of this study was to find out the antibiogram of ESBL producing organisms isolated from various samples.

Settings and Design:

This cross-sectional study was carried out in the Department of Microbiology of a Tertiary Care Hospital, Dhaka, Bangladesh from January to June 2014.

Subjects and Methods:

One Hundred and seventy-nine ESBL producing Gram-negative organisms detected phenotypically by double-disc synergy test were enrolled in this study. Required data were collected from the records of the Microbiology laboratory.

Results:

ESBL production was detected in 16.07% (179/1114) of isolated organism. Of Escherichia coli, 15.75% were ESBL producers; 14.01% Pseudomonas spp., 36.84% Proteus spp., 18.57% Klebsiella spp., and 21.05% of Acinetobacter spp., were ESBL producers. Maximum (43.58%) ESBL producers were isolated from surgery departments, and wound swabs yielded majority (53%) of them. About 13% ESBL producers were isolated in outdoor patients mostly from community-acquired infections. Most ESBL producers were resistant to commonly used antibiotics. Carbapenems especially imipenem was the most effective drug showing excellent sensitivity; colistin and piperacillin/tazobactam also had better sensitivity result. Most of the ESBL producers showed a good sensitivity to amikacin, but all of them were highly resistant to ciprofloxacin.

Conclusions:

ESBL production should be detected routinely in all Microbiology laboratories. Infection control, rational use of antibiotics must be done promptly to prevent the development and spread of ESBL producing organisms.

Dissecting the effects of antibiotics on horizontal gene transfer: Analysis suggests a critical role of selection dynamics

Horizontal gene transfer (HGT) is a major mechanism responsible for the spread of antibiotic resistance. Conversely, it is often assumed that antibiotics promote HGT. Careful dissection of the literature, however, suggests a lack of conclusive evidence supporting this notion in general. This is largely due to the lack of well-defined quantitative experiments to address this question in an unambiguous manner. In this review, we discuss the extent to which HGT is responsible for the spread of antibiotic resistance and examine what is known about the effect of antibiotics on the HGT dynamics. We focus on conjugation, which is the dominant mode of HGT responsible for spreading antibiotic resistance on the global scale. Our analysis reveals a need to design experiments to quantify HGT in such a way to facilitate rigorous data interpretation. Such measurements are critical for developing novel strategies to combat resistance spread through HGT.

Pediatric extended spectrum β-lactamase infection: Community-acquired infection and treatment options

BACKGROUND

Infection caused by extended spectrum β-lactamase (ESBL)-producing Enterobacteriaceae in pediatric patients has been increasing and spreading to the community, compromising the options for effective antibiotics. This retrospective study was conducted to identify which antibiotics ESBL-producing Enterobacteriaceae remain susceptible to. In addition, the prevalence of community-acquired infection caused by these organisms, and the possibility of association between these organisms and septic shock, were explored.

METHODS

Antibiotic susceptibility of ESBL-producing and non-ESBL-producing Escherichia coli and Klebsiella pneumoniae strains isolated from pediatric patients were reviewed to determine the rates of susceptibility to various antibiotics. A chart review was performed to clarify the prevalence of community-acquired infection and the severity.

RESULTS

Of 849 strains analyzed, 40% were ESBL positive. Apart from cephalosporins, ESBL-producing strains were also less likely to be susceptible to other antibiotics, such as quinolones, gentamicin, netilmicin, and cotrimoxazole, more than 90% of which were still susceptible to amikacin, carbapenems, colistin, and tigecycline. Around 20% of community-acquired infections in the present study were caused by ESBL-producing strains. ESBL-producing strains found in the community were more likely to be susceptible to gentamicin, netilmicin, and cefepime than those found in hospital. Infection caused by ESBL-producing strains was not significantly associated with septic shock.

CONCLUSION

The increase in infection caused by ESBL-producing Enterobacteriaceae limits the availability of effective antibiotics. Given that carbapenems are necessary for treating serious infections, amikacin, cefepime, and piperacillin/tazobactam are possible options for consolidative therapy or for non-serious infection.

Multidrug resistant, extended spectrum β-lactamase (ESBL)-producing Escherichia coli isolated from a dairy farm

Escherichia coli strains were isolated from a single dairy farm as a sentinel organism for the persistence of antibiotic resistance genes in the farm environment. Selective microbiological media were used to obtain 126 E. coli isolates from slurry and faeces samples from different farm areas. Antibiotic resistance profiling for 17 antibiotics (seven antibiotic classes) showed 57.9% of the isolates were resistant to between 3 and 15 antibiotics. The highest frequency of resistance was to ampicillin (56.3%), and the lowest to imipenem (1.6%), which appeared to be an unstable phenotype and was subsequently lost. Extended spectrum β-lactamase (ESBL) resistance was detected in 53 isolates and blaCTX-M, blaTEM and blaOXA genes were detected by PCR in 12, 4 and 2 strains, respectively. Phenotypically most isolates showing resistance to cephalosporins were AmpC rather than ESBL, a number of isolates having both activities. Phenotypic resistance patterns suggested co-acquisition of some resistance genes within subsets of the isolates. Genotyping using ERIC-PCR demonstrated these were not clonal, and therefore co-resistance may be associated with mobile genetic elements. These data show a snapshot of diverse resistance genes present in the E. coli population reservoir, including resistance to historically used antibiotics as well as cephalosporins in contemporary use.

Prevalence of Class 1 Integrons and Extended Spectrum Beta Lactamases among Multi-Drug Resistant Escherichia coli Isolates from North of Iran

Background:

Extended spectrum beta lactamases (ESBLs) are an important cause of transferable multidrug resistance (MDR) in gram-negative bacteria. The most described ESBL genes are generally found within integron-like structures as mobile genetic elements. The aim of this study was to identify the accompanying of class 1 integrons and ESBLs in the MDR E. coli isolates.

Methods:

Susceptibility to antimicrobial agents was determined for 33 E. coli strains by the disk diffusion method. Double-disk synergy test was applied for screening ESBL. To identify the strains carrying integrons, the conserved regions of integron-encoded integrase gene intI1 were amplified. For detection of gene cassettes, 5′CS and 3′CS primers were used.

Results:

All E. coli isolates were identified as multi-drug resistant. More than 50% of the isolates were resistant to tetracycline, cephalothin, cefuroxime, amoxicillin-clavulanic acid, and third generation cephalosporines. Nearly all of the isolates displayed sensitivity to piperacillin. There was a significant correlation between production of ESBL and resistance to all antibiotics except for ciprofloxacin and piperacillin (P < 0.01). Thirty two MDR strains (97%) included class 1 integron, and some isolates that included integrons were similar in the size of gene cassettes. The isolates were different in the resistance profiles; however, some others had similar resistance profiles. Of eight ESBL positive isolates, seven (87.5%) carried class 1 integrons.

Conclusion:

Class 1 integrons were frequent in MDR and also ESBL-producing E. coli isolates. High prevalence of class 1 integrons confirms that integron-mediated antimicrobial gene cassettes are important in E. coli resistance profile.

Detection of expanded-spectrum β-lactamases in Gram-negative bacteria in the 21st century

Emerging β-lactamase-producing-bacteria (ESBL, AmpC and carbapenemases) have become a serious problem in our community due to their startling spread worldwide and their ability to cause infections which are difficult to treat. Diagnosis of these β-lactamases is of clinical and epidemiological interest. Over the past 10 years, several methods have been developed aiming to rapidly detect these emerging enzymes, thus preventing their rapid spread. In this review, we describe the range of screening and detection methods (phenotypic, molecular and other) for detecting these β-lactamases but also whole genome sequencing as a tool for detecting the genes encoding these enzymes.

Characterization of pre-antibiotic era Klebsiella pneumoniae isolates with respect to antibiotic/disinfectant susceptibility and virulence in Galleria mellonella

The EGD Murray collection consists of approximately 500 clinical bacterial isolates, mainly Enterobacteriaceae, isolated from around the world between 1917 and 1949. A number of these "Murray" isolates have subsequently been identified as Klebsiella pneumoniae. Antimicrobial susceptibility testing of these isolates showed that over 30% were resistant to penicillins due to the presence of diverse blaSHV β-lactamase genes. Analysis of susceptibility to skin antiseptics and triclosan showed that while the Murray isolates displayed a range of MIC/minimal bactericidal concentration (MBC) values, the mean MIC value was lower than that for more modern K. pneumoniae isolates tested. All Murray isolates contained the cation efflux gene cepA, which is involved in disinfectant resistance, but those that were more susceptible to chlorhexidine were found to have a 9- or 18-bp insertion in this gene. Susceptibility to other disinfectants, e.g., H2O2, in the Murray isolates was comparable to that in modern K. pneumoniae isolates. The Murray isolates were also less virulent in Galleria and had a different complement of putative virulence factors than the modern isolates, with the exception of an isolate related to the modern lineage CC23. More of the modern isolates (41% compared to 8%) are classified as good/very good biofilm formers, but there was overlap in the two populations. This study demonstrated that a significant proportion of the Murray Klebsiella isolates were resistant to penicillins before their routine use. This collection of pre-antibiotic era isolates may provide significant insights into adaptation in K. pneumoniae in relation to biocide susceptibility.

Characterization of Extended-Spectrum β-Lactamase-Producing Escherichia coli Strains Isolated from Retail Foods in Shaanxi Province, China

Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli strains have been reported worldwide; however, the incidence and characterization of foodborne ESBL-producing E. coli strains have been rarely reported in the People's Republic of China. Among a collection of 659 E. coli isolates recovered from retail foods in Shaanxi Province, People's Republic of China, 223 cefoxitin-resistant and/or cefoperazone-resistant isolates were screened for ESBL production with the double disk diffusion test. The ESBL-producing isolates were characterized for antimicrobial resistance and the presence of blaTEM, blaSHV, and blaCTX-M genes. Isolates with blaCTX-M were further classified by PCR as having blaCTX-M-1, blaCTX-M-2, blaCTX-M-8, blaCTX-M-9, or blaCTX-M-25. One hundred forty-seven isolates were identified as ESBL positive. PCR detection revealed that 146 isolates (99.3%) contained the blaCTX-M gene. Among these isolates, 42 (28.8%) were positive for the enzyme CTX-M-1, 5 (3.4%) for CTX-M-2, and 99 (67.8%) for CTX-M-9. No CTX-M-8 and CTX-M-25 were found in this study. One hundred fifteen isolates (78.2%) were positive for the blaTEM gene, but blaSHV was not detected. Among the 147 ESBL-producing E. coli isolates, 75 (51.0%), 35 (23.8%), and 4 (2.7%) isolates were positive for blaTEM and blaCTX-M-9, blaTEM and blaCTX-M-1, and blaTEM and blaCTX-M-2, respectively. All of the 147 ESBL-producing isolates were resistant to three or more non-β-lactam antibiotics. This study provides evidence that foodborne E. coli can harbor ESBL-encoding genes. Thus, food could be a vehicle for the dissemination of ESBL-producing E. coli strains, a situation that requires surveillance and appropriate management strategies.

Antibiotic resistance and genotype of beta-lactamase producing Escherichia coli in nosocomial infections in Cotonou, Benin

Background

Beta lactams are the most commonly used group of antimicrobials worldwide.

The presence of extended-spectrum lactamases (ESBL) affects significantly the treatment of infections due to multidrug resistant strains of gram-negative bacilli. The aim of this study was to characterize the beta-lactamase resistance genes in Escherichia coli isolated from nosocomial infections in Cotonou, Benin.

Methods

Escherichia coli strains were isolated from various biological samples such as urine, pus, vaginal swab, sperm, blood, spinal fluid and catheter. Isolated bacteria were submitted to eleven usual antibiotics, using disc diffusion method according to NCCLS criteria, for resistance analysis. Beta-lactamase production was determined by an acidimetric method with benzylpenicillin. Microbiological characterization of ESBL enzymes was done by double disc synergy test and the resistance genes TEM and SHV were screened by specific PCR.

Results

ESBL phenotype was detected in 29 isolates (35.5%). The most active antibiotic was imipenem (96.4% as susceptibility rate) followed by ceftriaxone (58.3%) and gentamicin (54.8%). High resistance rates were observed with amoxicillin (92.8%), ampicillin (94%) and trimethoprim/sulfamethoxazole (85.7%). The genotype TEM was predominant in ESBL and non ESBL isolates with respectively 72.4% and 80%. SHV-type beta-lactamase genes occurred in 24.1% ESBL strains and in 18.1% of non ESBL isolates.

Conclusion

This study revealed the presence of ESBL producing Eschericiha coli in Cotonou. It demonstrated also high resistance rate to antibiotics commonly used for infections treatment. Continuous monitoring and judicious antibiotic usage are required.

In vitro susceptibility of characterized β-lactamase-producing strains tested with avibactam combinations

Avibactam, a broad-spectrum β-lactamase inhibitor, was tested with ceftazidime, ceftaroline, or aztreonam against 57 well-characterized Gram-negative strains producing β-lactamases from all molecular classes. Most strains were nonsusceptible to the β-lactams alone. Against AmpC-, extended-spectrum β-lactamase (ESBL)-, and KPC-producing Enterobacteriaceae or Pseudomonas aeruginosa, avibactam lowered ceftazidime, ceftaroline, or aztreonam MICs up to 2,048-fold, to ≤4 μg/ml. Aztreonam-avibactam MICs against a VIM-1 metallo-β-lactamase-producing Enterobacter cloacae and a VIM-1/KPC-3-producing Escherichia coli isolate were 0.12 and 8 μg/ml, respectively.

Phenotypic and molecular characterization of extended-spectrum beta-lactamase-producing Escherichia coli in Bangladesh

Background

Resistance to cephalosporins in Enterobacteriaceae is mainly due to the production of extended-spectrum beta-lactamase (ESBL). Little is known about ESBL-producing bacteria in Bangladesh. Therefore, the study presents results of phenotypic and molecular characterization of ESBL-producing Escherichia coli from hospitals in Bangladesh.

Methods

A total of 339 E. coli isolated from patients with urinary tract and wound infections attending three different medical hospitals in urban and rural areas of Bangladesh between 2003–2007 were screened for ESBL-production by the double disk diffusion test. Isolates with ESBL-phenotype were further characterized by antibiotic susceptibility testing, PCR and sequencing of different β-lactamase and virulence genes, serotyping, and XbaI-macrorestriction followed by pulsed-field gel electrophoresis (PFGE).

Results

We identified 40 E. coli with ESBL phenotype. These isolates were resistant to ceftriaxone, ceftazidime, cefotaxime, aztreonam, cefepime, and nalidixic acid but remained susceptible to imipenem. All but one isolate were additionally resistant to ciprofloxacin, and 3 isolates were resistant to cefoxitin. ESBL genes of blaCTX-M-1-group were detected in all isolates; blaTEM-type and blaOXA-1-type genes were detected in 33 (82.5%) and 19 (47.5%) isolates, respectively. Virulence genes that are present in diarrhoeagenic E. coli were not found. Class-1 integron was present in 20 (50%) isolates. All the ESBL-producing E. coli isolates harbored plasmids ranging between 1.1 and 120 MDa. PFGE-typing revealed 26 different pulsotypes, but identical pulsotype showed 6 isolates of serotype O25:H4.

Conclusion

The prevalence of multidrug-resistant ESBL-producing E. coli isolates appears to be high and the majority of the isolates were positive for bla_CTX-M. Although there was genetic heterogeneity among isolates, presence of a cluster of isolates belonging to serotype O25:H4 indicates dissemination of the pandemic uropathogenic E. coli clone in Bangladesh.

Study of extended spectrum β-lactamase producing Enterobacteriaceae and antibiotic coresistance in a tertiary care teaching hospital

Aims:

To study the prevalence of extended spectrum β-lactamase (ESBL) producing Enterobacteriaceae and coresistance to other commonly used antibiotics from the Bhopal region of Central India.

Settings and Design:

A prospective study was conducted from September 2011 to August 2012 in Microbiology Department of our tertiary health care center.

Materials and Methods:

A total of 1044 Enterobacteriaceae isolates were recovered from various specimens. ESBL production was detected by using Clinical Laboratory Standard Institute (CLSI) that described the phenotypic confirmatory test along with routine antibiotic susceptibility testing.

Statistical Analysis:

Two-tailed Z-test.

Results:

Escherichia coli was the most common isolate (65.32%). ESBL production was confirmed in 504 (48.27%) isolates. The isolates of E. coli (50.14%) were the most common ESBL producers. Maximum ESBL isolates were obtained from urine samples (52.28%) and male patients (52.54%). Sensitivity to imipenem was 100% followed by piperacillin–tazobactam (89.28%), meropenem (87.5%), and amikacin (83.92%). Significant resistance was detected against trimethoprim–sulfomethoxazole, fluoroquinolones, and gentamicin.

Conclusion:

This is the only study conducted from Central India and shows high prevalence of ESBL production among Enterobacteriaceae. Imipenem seems to be more sensitive than meropenem. Piperacillin–tazobactam combination was found to be the best among the β-lactam–β-lactamase inhibitor combinations. Prevalence of ESBL producers were more in males than females.

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.

Prevalence of extended spectrum beta lactamase producing Escherichia coli and Klebsiella pneumoniae urinary isolates in a tertiary care hospital in Kathmandu, Nepal

BACKGROUND

Escherichia coli and Klebsiella pneumoniae are the major bacterial pathogens being isolated and reported from mid stream urine (MSU) specimens, globally. These uropathogens are mostly implicated as the major extended spectrum beta-lactamase (ESBL) producers, severely limiting the therapeutic management in cases of urinary tract infections. Limited studies had been reported from Nepal investigating the ESBL producers among uropathogens. This study was designed to assess the prevalence of ESBL producing E.coli and K. pneumoniae in urinary isolates at a centrally located major tertiary care hospital in Kathmandu valley, Nepal.

METHODS

Between September 2011 and May 2012, during the nine months period, 6308 MSU specimens were collected aseptically from the same number of clinically suspected patients of urinary tract infections. The samples were cultured on MacConkey agar and blood agar. The isolates with significant bacteriuria (105 CFU / ml) were identified based on standard laboratory procedures. Antimicrobial susceptibility tests were carried out using various antimicrobial discs alongwith ceftriaxone on E.coli and K. pneumoniae isolates by Kirby Bauer disc diffusion method as per the recommendations of CLSI. On initial screening with ceftriaxone (30 μg) disc showing resistance was then confirmed for ESBL production by phenotypic confirmatory disc diffusion test (PCDDT) using ceftazidime (30 ug) and ceftazidime + clavulanic acid (30 μg + 10ug) disc as per guidelines of CLSI (2011).

RESULTS

Out of a total of 6308 MSU specimens investigated for significant bacteriuria, E.coli isolates were 444 (7.04%) and K.pneuminiae were 145 (2.3%) making a total of 589 (9.34%). Initial screening with ceftriaxone disc revealed 155 isolates of E.coli and 70 isolates of K.pneumoniae to be resistant. Further testing by PCDDT method showed 60/444 (=13.51%) of E. coli and 24/145 (=16.55%) of K. pneumoniae isolates to be confirmed ESBL producers. These ESBL - producer uropathogens showed high degree of resistance to ceftriaxone (100.0%), amoxycillin, fluoroquinolones and co-trimoxazole.

CONCLUSION

An emerging and moderately high prevalence of ESBL-producing E. coli and K. pneumoniae was observed and confirmed in the urinary isolates investigated. It is essential to have a regular and routine monitoring of ESBL producing clinical isolates in laboratory practice.

Prevalence of extended-spectrum β-lactamase-producing Escherichia coli on Bavarian dairy and beef cattle farms

Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli strains are believed to be widely distributed among humans and animals; however, to date, there are only few studies that support this assumption on a regional or countrywide scale. Therefore, a study was designed to assess the prevalence of ESBL-producing E. coli in dairy cows and beef cattle in the southern part of Bavaria, Germany. The study population included 30 mixed dairy and beef cattle farms and 15 beef cattle farms. Fecal samples, boot swabs, and dust samples were analyzed for ESBL-producing E. coli using selective media. PCR was performed to screen for CTX-M and ampC resistance genes. A total of 598 samples yielded 196 (32.8%) that contained ESBL-producing E. coli, originating from 39 (86.7%) of 45 farms. Samples obtained from mixed farms were significantly more likely to be ESBL-producing E. coli positive than samples from beef cattle farms (fecal samples, P < 0.001; boot swabs, P = 0.014; and dust samples, P = 0.041). A total of 183 isolates (93.4%) of 196 ESBL-producing E. coli-positive strains harbored CTX-M genes, CTX-M group 1 being the most frequently found group. Forty-six additional isolates contained ampC genes, and 5 of the 46 isolates expressed a blaCMY-2 gene. The study shows that ESBL-producing E. coli strains are commonly found on Bavarian dairy and beef cattle farms. Moreover, to our knowledge, this is the first report of the occurrence of blaCMY-2 in cattle in Germany.

Modified Double Disc Synergy Test to Detect ESBL Production in Urinary Isolates of Escherichia coli and Klebsiella pneumoniae

BACKGROUND AND OBJECTIVES

Various phenotypic methods are recommended in the routine practice to detect the ESBL production in gram negative bacilli. Among them, the Double Disc Synergy Test (DDST) which uses the third generation cephalosporins (3GC), is a simple and a reliable method. But the coexistence of AmpC may give false negative results. In such cases, the ESBL detection can be improved by using cefepime along with the third generation cephalosporins in DDST.

METHODS

A total of 350 urinary isolates (224 Escherichia coli and 126 Klebsiella pneumoniae) were studied for ESBL production by the modified double disc test (MDDST) i.e. by using cefotaxime, ceftriaxone, cefpopdoxime (third generation cephalosporins) and cefepime ( fourth generation cephalosporin) along with a amoxicillin-clavulanate disc.

RESULTS AND INTERPRETATION

ESBL production was seen in 63.4% (142/224) Escherichia coli and in 60.3% (76/126) Klebsiella pneumoniae isolates by MDDST. Among these, in twelve E.coli and five K.pneumoniae strains, only cefepime but none of the third generation cephalosporins showed synergism with amoxicillin-clavulanate. All these seventeen strains showed a clear extension of the edge of inhibition which was produced by cefepime towards the amoxicillin-clavulanate disc. These strains were further tested for AmpC co-production by the AmpC disc test and all these strains were found to be AmpC positive, thus revealing the superior activity of cefepime in detecting ESBLs in the bacteria which co-produced AmpC. A high degree of coresistance was found in the ESBL producers.

CONCLUSION

The ESBL detection can be improved by MDDST by using cefepime along with the third generation cephalosporins.

A genetic approach to the development of new therapeutic phages to fight pseudomonas aeruginosa in wound infections

Pseudomonas aeruginosa is a frequent participant in wound infections. Emergence of multiple antibiotic resistant strains has created significant problems in the treatment of infected wounds. Phage therapy (PT) has been proposed as a possible alternative approach. Infected wounds are the perfect place for PT applications, since the basic condition for PT is ensured; namely, the direct contact of bacteria and their viruses. Plenty of virulent ("lytic") and temperate ("lysogenic") bacteriophages are known in P. aeruginosa. However, the number of virulent phage species acceptable for PT and their mutability are limited. Besides, there are different deviations in the behavior of virulent (and temperate) phages from their expected canonical models of development. We consider some examples of non-canonical phage-bacterium interactions and the possibility of their use in PT. In addition, some optimal approaches to the development of phage therapy will be discussed from the point of view of a biologist, considering the danger of phage-assisted horizontal gene transfer (HGT), and from the point of view of a surgeon who has accepted the Hippocrates Oath to cure patients by all possible means. It is also time now to discuss the possible approaches in international cooperation for the development of PT. We think it would be advantageous to make phage therapy a kind of personalized medicine.

Extended-spectrum β-lactamase/AmpC-producing uropathogenic Escherichia coli from HIV patients: do they have a low virulence score?

Extended-spectrum β-lactamase (ESBL) production and quinolone resistance are often associated in enterobacteria. Prior exposure to 3G cephalosporins/quinolones accelerates the risk of resistance to both these groups of antibiotics. Hence, information on the antimicrobial resistance pattern of uropathogenic Escherichia coli (UPEC) isolates is important to better formulate the guidelines for the empirical therapy of urinary tract infection in the context of HIV/AIDS. The aim of this study was to determine the incidence of ESBL/AmpC and fluoroquinolone (FQ) resistance among urinary E. coli isolates and to establish the association of extraintestinal virulence and phylogenetic distribution with antibiotic resistance and host immunocompromisation. Accordingly, 118 urinary Escherichia coli isolates from HIV (n = 76) and non-HIV antenatal patients (n = 42) from Chennai, South India, were analysed for the presence of five virulence-associated genes (VAGs): pap, sfa/foc, afa/dra, iutA and kpsMII. Compared with the susceptible HIV isolates, the majority of the ESBL(+)AmpC(+)FQ(R) isolates harboured iutA (66.7%) and pap (40%). The FQ-resistant HIV isolates were significantly enriched for iutA (67.8%) and kpsMII (47.5%) and qualified as UPEC (54.2%), while a majority of the FQ-susceptible isolates from the non-HIV patients were found to harbour pap (48.4%), sfa/foc (41.9%) and kpsMII (48.4%) and were classified as UPEC (40.5%). We conclude that antibiotic-resistant (ESBL(+)AmpC(+)and/or FQ(R)) phylogroup D isolates with limited virulence are competent enough to establish infections in HIV patients, while among non-HIV patients, an array of virulence factors is essential for E. coli to overcome host defences irrespective of antibiotic resistance.

AFM probing the mechanism of synergistic effects of the green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) with cefotaxime against extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli

Background

Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae poses serious challenges to clinicians because of its resistance to many classes of antibiotics.

Methods and Findings

The mechanism of synergistic activity of a combination of (−)-epigallocatechin-3-gallate (EGCG) and β-lactam antibiotics cefotaxime was studied on Extended-spectrum β-lactamase producing Escherichia coli (ESBL-EC), by visualizing the morphological alteration on the cell wall induced by the combination using atomic force microscopy (AFM). Cells at sub-MICs (sub-minimum inhibitory concentrations) of cefotaxime were initially filamentated but recovered to the normal shape later, whereas cells at sub-MICs of EGCG experienced temporal disturbance on the cell wall such as leakage and release of cellular debris and groove formation, but later recovered to the normal shape. In contrast, the combination of cefotaxime and EGCG at their respective sub-MICs induced permanent cellular damages as well as continuous elongation in cells and eventually killed them. Flow cytometry showed that intracellular oxidative stress levels in the cell treated with a combination of EGCG and cefotaxime at sub-MICs were higher than those in the cells treated with either cefotaxime or EGCG at sub-MICs.

Conclusions

These results suggest that the synergistic effect of EGCG between EGCG and cefotaxime against ESBL-EC is related to cooperative activity of exogenous and endogenous reactive oxygen species (ROS) generated by EGCG and cefotaxime, respectively.

The emergence of antibiotic resistance in typhoid fever

Typhoid fever, caused by Salmonella typhi, causes over 20 million cases annually, with at least 700,000 deaths. The main burden of disease is in developing countries, particularly the Indian Subcontinent and South East Asia. However, cases in returning travellers, immigrants and refugees in developed countries are not uncommon. Drug resistance is fast becoming a major problem in the management of this infection. Chloramphenicol resistance became established globally in the S.Typhi population after 1972 on plasmids of incompatibility group IncH. Multi-drug resistance defined as resistance to the three first-line agents used to treat typhoid fever, namely chloramphenicol, ampicillin and co-trimoxazole, and acquired on the same plasmid type, has been endemic in most of South East Asia and the Indian Subcontinent for many years. Resistance data from many endemic areas are sparse and with the increasing problem of reduced sensitivity to the fluoroquinolone antibiotics, empirical choice of antibiotics may be difficult. We review the historical aspects of the development of resistance and the current data available on the epidemiology of antibiotic resistance in S.Typhi.

Discrepancy between effects of carbapenems and flomoxef in treating nosocomial hemodialysis access-related bacteremia secondary to extended spectrum beta-lactamase producing Klebsiella pneumoniae in patients on maintenance hemodialysis

Background

Hemodialysis (HD) patients are susceptible to extended spectrum beta-lactamase (ESBL)-producing bacterial infections. Because the optimal treatment and clinical significance of ESBL-producing Klebsiella pneumoniae (ESBL-Kp) HD access-related bacteremia remain unclear, we conducted this retrospective study to determine the clinical outcomes of patients treated with either flomoxef or a carbapenem.

Methods

The eligibility criterion was fistula or graft- or catheter- related ESBL-Kp bacteremia in patients on maintenance HD. The clinical characteristics and antibiotic management were analyzed. Outcome was determined by mortality resulting from bacteremia during the 14‐day period after the first positive blood culture for flomoxef-susceptible ESBL-Kp.

Results

The 57 patients studied were predominantly elderly, malnourished, with a history of severe illnesses and broad-spectrum antibiotic use before the onset of bacteremia, and with severe septicemia as determined by the Pitt bacteremia score (PBS). The study population comprised 7 fistula, 8 graft, and 42 HD catheter-related bacteremia (CRB) cases, and the mortality rate was high (36/57, 63.2%) in these 57 patients. Of 42 patients with CRB, those in the deceased group (27/42, 64.3%) had significantly lower levels of serum albumin, longer prior hospital stay and duration of catheter-dependent HD, and higher PBS than patients in the survived group. Failure to receive effective antibiotics (flomoxef or a carbapenem) within 5 days after onset of bacteremia and treatment with flomoxef both significantly contributed to higher mortality. Multivariate analyses revealed that flomoxef use, PBS, and catheter-dependent HD >30 days were independently associated with increased mortality (OR, 3.52; 95% CI, 1.19–58.17, OR, 2.92; 95% CI, 1.36–6.26 and OR, 5.73; 95% CI, 1.21–63.2, respectively).

Conclusions

Considering the high mortality rate, ESBL-Kp should be recognized as a possible pathogen in patients on maintenance HD at high risk of acquiring HD access infections associated with ESBL-producing bacteria. Carbapenems rather than flomoxef should be the therapy of choice in these critically vulnerable patients.

Postoperative meningitis and epidural abscess due to extended-spectrum β-lactamase-producing Klebsiella pneumoniae: a case report and a review of the literature

17-year-old man had been involved in a traffic accident. He underwent a bilateral craniotomy with artificial dura mater to remove bilateral acute subdural hematomas. Seven months later, a right cranioplasty was performed using frozen auto-bone, and he developed extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae meningitis and an epidural abscess. Since his general status was poor, we could not remove the foreign body (artificial dura mater). He was successfully treated with meropenem and chronic suppression with oral trimethoprim-sulfamethoxazole. By describing this case and the results of a review of the pertinent literature, we discuss the importance of ESBL-producing Klebsiella pneumoniae meningitis in posttraumatic/postoperative patients.

ESBL genotypes in fluoroquinolone-resistant and fluoroquinolone-susceptible ESBL-producing Escherichia coli urinary isolates in Manitoba

OBJECTIVE

Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli are increasingly common in nosocomial and community settings. Furthermore, fluoroquinolone (FQ) and even multidrug resistance (MDR) appear to be associated with certain ESBL genotypes. The purpose of the present study was to determine which ESBL genotypes are associated with FQ and MDR in E coli urinary isolates in Manitoba.

METHODS

The authors determined the antimicrobial susceptibility, genetic similarity and ESBL genotype of 27 FQ-resistant and seven FQ-susceptible, ESBL-producing urinary isolates submitted to the clinical microbiology laboratories of two teaching hospitals between October 2000 and April 2005. Susceptibilities to beta-lactams, FQs, trimethoprim-sulfamethoxazole (SXT), doxycycline (DOX), gentamicin (GM) and tigecycline were determined by microbroth dilution; pulsed-field gel electrophoresis (PFGE) was used to determine genetic relatedness, and ESBL genotype was determined by polymerase chain reaction and sequencing.

RESULTS

Of 34 ESBL-producing organisms, 27 (79.4%) were found to be ciprofloxacin (CIP) resistant, 27 (79.4%) were SXT resistant, eight (23.5%) were GM resistant and 29 (85.3%) were DOX resistant. Twenty-three (67.6%) had MDR, with concomitant resistance to CIP and SXT; 16 had concomitant resistance to CIP, SXT and DOX; and seven (20.6%) had MDR, with concomitant resistance to CIP, SXT, DOX and GM. All isolates were susceptible to tigecycline. Of 27 FQ-resistant ESBL-producing organisms, seven (25.9%) were genotype CTX-M-14, 19 (70.4%) were genotype CTX-M-15 and one (3.7%) was genotype CTX-M-24. Among the seven FQ-susceptible strains, three (42.8%) expressed SHV-type enzymes, three (42.8%) expressed TEM-type enzymes and one (14.3%) expressed CTX-M-9. CTX-M-15 was the most common MDR-associated genotype. Of a total of 19 strains, 18 (94.7%) were resistant to FQs and SXT; 15 (78.9%) were resistant to FQs, SXT and DOX; and five (26.3%) were resistant to FQs, SXT, DOX and GM. PFGE analysis revealed genetic similarity within CTX-M-15-producing isolates only.

CONCLUSION

CTX-M-15 in E coli is strongly associated with an MDR phenotype compared with other genotypes. CTX-M-14 is associated with FQ resistance only. PFGE suggests clonality of CTX-M-15-producing isolates within and among hospitals.

Genetic methods for detection of antibiotic resistance: focus on extended-spectrum β-lactamases

BACKGROUND

In 1928, the first antibiotic, penicillin, was discovered. That was the beginning of a great era in the development and prescription of antibiotics. However, the introduction of these antimicrobial agents into clinical practice was accompanied by the problem of antibiotic resistance. Currently, bacterial resistance to antibiotics poses a major problem in both hospital and community settings throughout the world.

METHODS AND RESULTS

This review provides examples of modern genetic methods and their practical application in the field of extended-spectrum β-lactamase detection. Since extended-spectrum β-lactamases are the main mechanism of Gram-negative bacterial resistance to oxyimino-cephalosporins, rapid and accurate detection is requested in common clinical practice.

CONCLUSIONS

Currently, the detection of extended-spectrum β-lactamases is primarily based on the determination of bacterial phenotypes rather than genotypes. This is because therapeutic decisions are based on assessing the susceptibility rather than presence of resistance genes. One of the main disadvantages of genetic methods is high costs, including those of laboratory equipment. On the other hand, if these modern methods are introduced into diagnostics, they often help in rapid and accurate detection of certain microorganisms or their resistance and pathogenic determinants.

Retrospective study of an outbreak in a Kuwaiti hospital of multidrug-resistant Klebsiella pneumoniae possessing the new SHV-112 extended-spectrum beta-lactamase

Patients infected with bacteria producing extendedspectrum beta-lactamases (ESBL) are at higher risk of mortality and morbidity. Several mutations in genes encoding SHV, tem and CTX-M beta-lactamases have been associated with ESBL activity. This paper describes a new SHV mutation in ESBL-producing strains of Klebsiella pneumoniae isolated in Kuwait. The study included 13 K. penumoniae strains isolated from patients admitted to the Amiri hospital of Kuwait. The production of ESBL in all strains was confirmed by Vitek system and E-test. All the ESBL genes were amplified by PCR and examined by DNA sequencing. All these ESBL-positive isolates were resistant to ceftazidime and cefotaxime. DNA sequencing revealed an A815G point mutation in the bla (SHV )gene causing an asparagine (AAT) to aspartic acid (GAT) mutation at position 253 of the enzyme. This new mutation was assigned the unique number SHV-112, and the Genebank accession number EU477409. This study reports a new mutation in the SHV gene in K. pneumoniae with ESBL capability. There could be other mutations still to be found in ESBL genes of K. pneumoniae in Kuwait and probably in other middle eastern countries, and researchers in the region should make use of molecular techniques to look for more novel mutations in ESBL-producing strains of K. pneumoniae.

Extended-spectrum β-lactamases of Escherichia coli and Klebsiella pneumoniae screened by the VITEK 2 system

The VITEK 2 automated system (bioMérieux) is one of the most widely used instruments in clinical microbiology laboratories for the identification and evaluation of the susceptibility profiles of bacteria including the detection of extended-spectrum β-lactamases (ESBLs) produced by Escherichia coli, Klebsiella pneumoniae and Klebsiella oxytoca. Currently, the Clinical and Laboratory Standards Institute recommends the use of ESBL confirmatory tests in addition to standard susceptibility testing. In order to evaluate the accuracy of VITEK 2-positive results regarding clinical isolates of E. coli (n = 110) and K. pneumoniae (n = 72), four additional ESBL detection systems were compared: the Phoenix Automated Microbiology System (BD Diagnostic Systems) and the MicroScan WalkAway-96 System (Dade Behring), and two manual systems as confirmatory tests, the Etest (AB Biodisk) and double disc diffusion (DDS) test. Epidemiological data regarding the tested strains were also collected and their susceptibility phenotypes were determined. The four methods resulted in concordant results for 126 of the 182 strains. However, the different tests displayed distinct results: the VITEK 2 system was in disagreement in 23.9 % of cases with DDS, in 15.3 % with Etest, in 23 % with the MicroScan WalkAway-96 System and in 23.6 % with the Phoenix Automated Microbiology System. Epidemiological data indicated that the majority of ESBL-positive E. coli strains were isolated from patients admitted to internal medicine wards (72.7 %), whilst K. pneumoniae ESBL-positive isolates were equally distributed between internal medicine wards (45.8 %) and intensive care units (45.8 %). Most of these strains were isolated from urine. In contrast to ESBL-negative isolates, the ESBL-positive strains displayed multiple drug resistance, namely to quinolones, aminoglycosides and trimethoprim-sulfamethoxazole. No significant resistance to carbapenems was detected. Overall, this study demonstrates the need for a confirmatory test following positive ESBL detection with the VITEK 2 system (panel AST-037), which appears to yield a large number of false-positive results.

[Epidemiological study of Klebsiella spp. uropathogenic strains producing extended-spectrum β-lactamase in a Tunisian university hospital, 2009]

OBJECTIVE

An update on the prevalence of antibiotic resistance in extended-spectrum β-lactamase among urinary strains of Klebsiella spp. isolated from in-come and out-come patients at University Hospital, Mahdia (Tunisia).

PATIENTS AND METHODS

A retrospective survey was made over a period of twelve months (year 2009). It focused on 3564 patients with urinary tract infection confirmed by the Laboratory of Microbiology in the University Hospital, Mahdia.

RESULTS

Klebsiella spp. was involved in 5.5% (198/3564) of all cases of urinary tract infections identified. Klebsiella pneumoniae accounted for 94.9% of all Klebsiella (5.1% for Klebsiella oxytoca). The frequency of Klebsiella spp. resistance to fluoroquinolones was 19.2% and to third generation cephalosporins was 22.7%. Forty strains of Klebsiella spp. producing extended-spectrum β-lactamase witch corresponds to 20.2% of all the Klebsiella. The extended-spectrum β-lactamase strains with resistance to fluoroquinolones were 67.5% (27/40) or 13.6% of all klebsiella (27/198). No strain was resistant to imipenem. The 27 strains multiresistant (ESBL+FQ resistance) are likely to be carriers of plasmids encoding the ESBL and resistance to fluoroquinolones.

CONCLUSION

the resistance of Enterobacteriaceae, including Klebsiella spp, to fluoroquinolones has become a concern both in hospital in community medicine. The advent of this resistance mechanism involves a more rational use of fluoroquinolones, especially as first-line treatment of urinary tract infections.

Rapid functional definition of extended spectrum β-lactamase activity in bacterial cultures via competitive inhibition of fluorescent substrate cleavage

The functional definition of extended-spectrum β-lactamase (ESBL) activity is a clinical challenge. Here we report a rapid and convenient assay of β-lactamase activity through the competitive inhibition of fluorescent substrate hydrolysis that provides a read-out nearly 40× more rapidly than conventional techniques for functional definition. A panel of β-lactam antibiotics was used for competition against β-lactamase enzyme-activated photosensitizer (β-LEAP) yielding a competitive index (C(i)) in 30 min. Significant differences in the relative C(i) values of the panel of β-lactams were determined in vitro for Bacillus cereus penicillinase. Additionally, the relative C(i) values for whole bacterial cell suspensions of B. cereus 5/β were compared with the relative minimal inhibitory concentration (MIC) values and a correlation coefficient of 0.899 was determined. We further demonstrated the ability of β-LEAP to probe the capacity of ceftazidime to inhibit the enzyme activity of a panel of ESBL-producing Escherichia coli. The bacteria were assayed for susceptibility to ceftazidime and the relative MIC values were compared with the relative C(i) values for ceftazidime yielding a correlation coefficient of 0.984. This work demonstrates for the first time the whole cell assay of the competitive inhibition of β-lactamase enzyme activity and derivation of associated constants.