Molecular epidemiology and antimicrobial susceptibility of extended- and broad-spectrum β-lactamase-producing Klebsiella pneumoniae isolated in Portugal

Extended-spectrum beta-lactamase-producing Klebsiella pneumoniae and risk factors associated with high total bacterial count in bulk tank milk from dairy farms in Colombia

The objective of the study was to evaluate the frequency and genetic characteristics of ESBL-producing Escherichia coli and Klebsiella spp. and the risk factors associated with a high total bacterial count in bulk tank milk samples of dairy farms in three municipalities of the Antioquia Department, Colombia. Fifteen samples were positive for E. coli and Klebsiella spp. Subsequent analysis of the 16 S rRNA gene sequences confirmed these isolates included E. coli (n = 3), K. oxytoca (n = 11), and K. pneumoniae (n = 1). None of the isolates was positive for ESBL identification by phenotypic methods, but the only the isolate of K. pneumoniae was positive for the blaSHV61 gene by sequence analysis. The antibiotic susceptibility evaluation for all Klebsiella spp. isolates identified resistance to fosfomycin (50%; 6/12) and ampicillin (100%; 12/12). While most of the herds maintain adequate hygienic quality, specific risk factors such as having more than 60 milking cows, frequent changes in milkers, milking in paddocks, and using a chlorinated product for pre-dipping have been identified as associated with a high total bacterial count > 100,000 CFU/mL in bulk tank milk. However, certain variables including the milker being the owner of the animals and the proper washing and disinfection of the milking machine contribute to maintain a high level of hygiene and quality in the raw milk stored in the tanks. In conclusion, the frequency of ESBL producers was relatively low, with only K. pneumoniae testing positive for the blaSHV ESBL type. The presence of these bacteria in milk tanks represents a potential risk to public health for consumers of raw milk and its derivatives.

Characterization of Carbapenemase- and ESBL-Producing Gram-Negative Bacilli Isolated from Patients with Urinary Tract and Bloodstream Infections

A total of 199 Gram-negative bacterial isolates from urinary tract infections and 162 from bloodstream infections were collected from 12 healthcare systems throughout the United States between May 2021 and August 2022. The isolates, phenotypically non-susceptible to 2nd or 3rd generation cephalosporins or carbapenems, were characterized through antimicrobial susceptibility testing and whole genome sequence analysis to obtain a broad snapshot of beta-lactamase-mediated resistance among these two sample types. Overall, 23 different carbapenemase genes were detected among 13 species (20.5% of isolates). The blaKPC-3 and blaKPC-2 subtypes were the most common carbapenemase genes identified, followed by blaNDM and the co-carriage of two different blaOXA carbapenemases by Acinetobacter baumannii isolates. All carbapenemase-producing A. baumannii isolates were mCIM negative. Extended-spectrum beta-lactamase genes were identified in 66.2% of isolates; blaCTX-M-15 was the most common. AmpC genes, both plasmid and chromosomal, were detected in 33.2% of isolates. Importantly, 2.8%, 8.3%, and 22.2% of blaKPC-positive organisms were susceptible to ertapenem, imipenem, and meropenem, respectively. The correlation between broth microdilution and disk diffusion results was high for most drugs except cefepime, where the detection of resistance was statistically lower by disk diffusion. Thus, there were gaps in the accuracy of susceptibility testing for some mechanisms of resistance.

Epidemiology of carbapenem-resistant Klebsiella pneumoniae ST15 of producing KPC-2, SHV-106 and CTX-M-15 in Anhui, China

Background:

It is well known that carbapenem-resistant Klebsiella pneumoniae (CRKP) has become a more problematic public health issue due to its widespread spread worldwide. In China, ST11-type CRKP is the most prevalent CRKP, but ST15-type CRKP, a recently prevalent high-risk clone, has emerged widely throughout China, posing a serious public health risk. Therefore, we conducted an epidemiological of an outbreak of ST15 CRKP of producing CTX-M-15, KPC-2 and SHV-106 in a tertiary hospital in Anhui, China, to Understanding the potential risks of the current STT15 CRKP outbreak.

Results:

From July 2021 to December 2021, 13 ST15 CRKP isolates were identified by collecting non-repeated clinical multidrug-resistant isolates, with all capsular typing of serotype KL19. All ST15 CRKP isolates were resistant to cephalosporins, carbapenems and quinolones, but were sensitive to amikacin, tigecycline and polymyxin B. In addition, isolates carried bla_SHV−106 (100%), bla_KPC−2 (69%), bla_CTX−M−15 (69%), bla_TEM−1B (69%), bla_OXA−1 (62%) and bla_LAP−2 (8%), as well as iron chelators (iutA, ybt, fyuA, ent, fepA, irp1, irp2, 100%) were detected. In phenotyping experiments, all ST15 CRKP exhibited lower growth rates than NTUH-K2044, and all ST15 CRKP did not exhibit mucoviscositty characteristics. However, in the Galleria mellonella infection model, isolates 21081212, 21081241 and 21091216 were more lethal than the hypervirulent isolates NTUH-K2044. Sequencing results showed that the genetic environment surrounding the genes bla_SHV−106, bla_KPC−2, bla_CTX−M−15, bla_OXA−1 and bla_TEM−1B were all identical in the ST15 CRKP isolates. Phylogenetic analysis showed that 13 ST15 CRKP isolates were divided into three subgroups, and when placed in global analysis, 10 of them were highly homologous to isolates from Jiangsu, two were highly homologous to isolates from Zhejiang, and one was homologous to an isolate from an unlabelled region.

Conclusion:

Our research shows that ST15 CRKP, which carries multiple β-lactamases genes and siderophores-encoding genes, may be evolving to hypervirulence and may have spread widely in localised areas. Therefore, environmental surveillance and clinical infection control in hospitals should be strengthened to prevent further spread of ST15 CRKP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02672-1.

Molecular genetic characteristics of resistome and virulome of carbapenem-resistant Klebsiella pneumoniae clinical strains

The characteristics of resistome and virulome structure of four carbapenem-resistant Klebsiella pneumoniae clinical strains are present in the work. Two strains belonged to the sequence-type ST395, one strain - ST2262, one strain - to the new sequence-type 5816. The genes of fimbriae, enterobactin, beta-lactamase SHV type, resistance to fosfomycin fosA and transport of fluoroquinolones oqxAB in all Klebsiella strains chromosome structure were identified. The determinants of yersineobactin and aerobactin are enriched the virulome of ST395 NNKP315 and NNKP343 strains. The aerobactin genes are located on IncHI1B plasmids (IncHI1B/FIB) which highly homologous to the virulence pLVPK and pK2044 plasmids. IncR, IncL, IncQ plasmids carrying blaOXA-48, blaCTX-M-15, blaOXA-1, blaTEM-1, qnrS1, tetA, sul1, dfrA1, aac(6 ')-Ib-cr, catA1, catB3 etc. were identified in these strains. As a result of in silico analysis, an assumption about the localization of the blaOXA-48 in the structure of the IncHI1B plasmid of NNKP315 strain was made. This plasmid also contains the aminoglycosidases genes inserted into a class 1 integron In822. The mutations were found in the porin proteins OmpK35, OmpK36 and OmpK37 genes, which increases the carbapenem resistance. The virulome of NNKP16 (ST2262) strain additionally includes of the iron utilization system kfuABC chromosomal genes, and the virulome of NNKP15 (ST5816) strain contains of the capsular polysaccharide kvgAS and microcin E492 genes. Additional determinants of resistance were not identified in the resistome structure of K. pneumoniae NNKP16 and only the blaCTX-M-15 gene was found in the NNKP15 strain. The absence of acquired resistance genes seems to be due to the presence of the type I-E CRISPR-Cas system. Multiple drug resistance of the studied strains is associated with mutations identified in the gene structure of porin proteins OmpK36 and OmpK37, as well as the activity of efflux systems. It was showed the stop codon formation in the nucleotide sequence of the regulatory gene ramR to both strains, which can potentially provide overexpression of AcrAB efflux proteins.

Extended-spectrum β-lactamases: an update on their characteristics, epidemiology and detection

Extended-spectrum β-lactamase (ESBL)-producing Gram-negative pathogens are a major cause of resistance to expanded-spectrum β-lactam antibiotics. Since their discovery in the early 1980s, they have spread worldwide and an are now endemic in Enterobacterales isolated from both hospital-associated and community-acquired infections. As a result, they are a global public health concern. In the past, TEM- and SHV-type ESBLs were the predominant families of ESBLs. Today CTX-M-type enzymes are the most commonly found ESBL type with the CTX-M-15 variant dominating worldwide, followed in prevalence by CTX-M-14, and CTX-M-27 is emerging in certain parts of the world. The genes encoding ESBLs are often found on plasmids and harboured within transposons or insertion sequences, which has enabled their spread. In addition, the population of ESBL-producing Escherichia coli is dominated globally by a highly virulent and successful clone belonging to ST131. Today, there are many diagnostic tools available to the clinical microbiology laboratory and include both phenotypic and genotypic tests to detect β-lactamases. Unfortunately, when ESBLs are not identified in a timely manner, appropriate antimicrobial therapy is frequently delayed, resulting in poor clinical outcomes. Several analyses of clinical trials have shown mixed results with regards to whether a carbapenem must be used to treat serious infections caused by ESBLs or whether some of the older β-lactam-β-lactamase combinations such as piperacillin/tazobactam are appropriate. Some of the newer combinations such as ceftazidime/avibactam have demonstrated efficacy in patients. ESBL-producing Gram-negative pathogens will continue to be major contributor to antimicrobial resistance worldwide. It is essential that we remain vigilant about identifying them both in patient isolates and through surveillance studies.

Multidrug-resistant Klebsiella pneumoniae: mechanisms of resistance including updated data for novel β-lactam-β-lactamase inhibitor combinations

Introduction: Multi-drug-resistant Klebsiella pneumoniae is currently one of the most pressing emerging issues in bacterial resistance. Treatment of K.pneumoniae infections is often problematic due to the lack of available therapeutic options, with a relevant impact in terms of morbidity, mortality and healthcare-associated costs. Soon after the launch of Ceftazidime-Avibactam, one of the approved new β-lactam/β-lactamase inhibitor combinations, reports of ceftazidime-avibactam-resistant strains developing resistance during treatment were published. Being a hospital-associated pathogen, K.pneumoniae is continuously exposed to multiple antibiotics resulting in constant selective pressure, which in turn leads to additional mutations that are positively selected.Areas covered: Herein the authors present the K.pneumoniae mechanisms of resistance to different antimicrobials, including updated data for ceftazidime-avibactam.Expert opinion: K.pneumoniae is a nosocomial pathogen commonly implicated in hospital outbreaks with a propensity for antimicrobial resistance toward mainstay β-lactam antibiotics and multiple other antibiotic classes. Following the development of drug resistance and understanding the mechanisms involved, we can improve the efficacy of current antimicrobials, by applying careful stewardship and rational use to preserve their potential utility. The knowledge on antibiotic resistance mechanisms should be used to inform the design of novel therapeutic agents that might not be subject to, or can circumvent, mechanisms of resistance.

Multidrug-resistant Klebsiella pneumoniae harboring extended spectrum β-lactamase encoding genes isolated from human septicemias

Klebsiella pneumoniae is a major pathogen implicated in nosocomial infections. Extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae isolates are a public health concern. We aim to characterize the type of β-lactamases and the associated resistance mechanisms in ESBL-producing K. pneumoniae isolates obtained from blood cultures in a Portuguese hospital, as well as to determine the circulating clones. Twenty-two cefotaxime/ceftazidime-resistant (CTX/CAZ^R) K. pneumoniae isolates were included in the study. Identification was performed by MALDI-TOF MS and the antimicrobial susceptibility testing by disk-diffusion. The screening test for ESBL-production was performed and ESBL-producer isolates were further characterized. The presence of different beta-lactamase genes (bla_CTX-M, bla_SHV, bla_TEM, bla_KPC, bla_NDM,bla_VIM,bla_OXA-48,bla_CMY-2, bla_DHA-1,bla_FOX,bla_MOX, and bla_ACC) was analyzed by PCR/sequencing in ESBL-producer isolates, as well as the presence of other resistance genes (aac(6’)-Ib-cr, tetA/B, dfrA, qnrA/B/S, sul1/2/3) or integron-related genes (int1/2/3). Multilocus-sequence-typing (MLST) was performed for selected isolates. ESBL activity was detected in 12 of the 22 CTX/CAZ^RK. pneumoniae isolates and 11 of them carried the bla_CTX-M-15 gene (together with bla_TEM)_, and the remaining isolate carried the bla_SHV-106 gene. All the bla_CTX-M-15 harboring isolates also contained a bla_SHV gene (bla_SHV-1, bla_SHV-11 or bla_SHV-27 variants). Both bla_SHV-27 and bla_SHV-106 genes correspond to ESBL-variants. Two of the CTX-M-15 producing isolates carried a carbapenemase gene (bla_KPC2/3 and bla_OXA-48) and showed imipenem resistance. The majority of the ESBL-producing isolates carried the int1 gene, as well as sulphonamide-resistance genes (sul2 and/or sul3); the tetA gene was detected in all eight tetracycline-resistant isolates. Three different genetic lineages were found in selected isolates: ST348 (one CTX-M-15/TEM/SHV-27/KPC-2/3-producer isolate), ST11 (two CTX-M-15/TEM/SHV-1- and CTX-M-15-TEM-SHV-11-OXA-48-producer isolates) and ST15 (one SHV-106/TEM-producer isolate). ESBL enzymes of CTX-M-15 or SHV-type are detected among blood K. pneumoniae isolates, in some cases in association with carbapenemases of KPC or OXA-48 type.

Epidemiology of β-Lactamase-Producing Pathogens

β-Lactam antibiotics have been widely used as therapeutic agents for the past 70 years, resulting in emergence of an abundance of β-lactam-inactivating β-lactamases. Although penicillinases in Staphylococcus aureus challenged the initial uses of penicillin, β-lactamases are most important in Gram-negative bacteria, particularly in enteric and nonfermentative pathogens, where collectively they confer resistance to all β-lactam-containing antibiotics. Critical β-lactamases are those enzymes whose genes are encoded on mobile elements that are transferable among species. Major β-lactamase families include plasmid-mediated extended-spectrum β-lactamases (ESBLs), AmpC cephalosporinases, and carbapenemases now appearing globally, with geographic preferences for specific variants. CTX-M enzymes include the most common ESBLs that are prevalent in all areas of the world. In contrast, KPC serine carbapenemases are present more frequently in the Americas, the Mediterranean countries, and China, whereas NDM metallo-β-lactamases are more prevalent in the Indian subcontinent and Eastern Europe. As selective pressure from β-lactam use continues, multiple β-lactamases per organism are increasingly common, including pathogens carrying three different carbapenemase genes. These organisms may be spread throughout health care facilities as well as in the community, warranting close attention to increased infection control measures and stewardship of the β-lactam-containing drugs in an effort to control selection of even more deleterious pathogens.

Outbreak of KPC-2-producing Klebsiella pneumoniae endowed with ceftazidime-avibactam resistance mediated through a VEB-1-mutant (VEB-25), Greece, September to October 2019

From September to October 2019, seven patients colonised or infected with a ceftazidime-avibactam (CZA)-resistant Klebsiella pneumoniae carbapenemase (KPC)-2-producing K. pneumoniae were detected in two intensive care units of a Greek general hospital. The outbreak strain was sequence type (ST)147 and co-produced KPC-2 and the novel plasmid-borne Vietnamese extended-spectrum β-lactamase (VEB)-25 harbouring a K234R substitution associated with CZA resistance. Epidemiological investigations revealed that the resistance was probably acquired by horizontal transmission independently from previous CZA exposure.

Spreading of extended-spectrum β-lactamase-producing Escherichia coli ST131 and Klebsiella pneumoniae ST11 in patients with pneumonia: a molecular epidemiological study

Supplemental Digital Content is available in the text

Background:

Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) are the important pathogens causing pneumonia. This study aimed to investigate the clinical characteristics and molecular epidemiology of ESBL-producing E. coli and K. pneumoniae causing pneumonia at a large teaching hospital in China.

Methods:

We collected patient's clinical data and ESBL-producing E. coli and K. pneumoniae strains causing pneumonia (from December 2015 to June 2016) at a hospital in Wuhan. The susceptibilities, multi-locus sequence typing, homologous analysis, ESBL genes by polymerase chain reaction and sequencing were determined.

Results:

A total of 59 ESBL-producing strains (31 E. coli and 28 K. pneumoniae) isolated from patients with pneumonia were analyzed. The majority of strains were isolated from patients were with hospital-acquired pneumonia (37/59, 62.7%), followed by community-acquired pneumonia (13/59, 22.0%), and ventilator-related pneumonia (9/59, 15.3%). The E. coli ST131 (9 isolates, 29.0%) and K. pneumoniae ST11 (5 isolates, 17.9%) were the predominant sub-types. The most prevalent ESBL gene was CTX-M-14, followed by SHV-77, CTX-M-3, SHV-11, and CTX-M-27. At least 33 (55.9%) of the ESBL-producing strains carried two or more ESBL genes. The ISEcp1 and IS26 were found upstream of all blaCTX-M (CTX-Ms) and of most blaSHV (SHVs) (57.6%), respectively. Moreover, three ESBL-producing K. pneumoniae ST11 strains which were resistant to carbapenems carried the bla_NDM-1 and bla_KPC-2, two of which also bearing bla_OXA-48 were resistant to all antibiotics (including Tigecycline).

Conclusions:

Hospital-acquired pneumonia is more likely correlated with ESBL-producing E. coli and K. pneumoniae. ESBL-producing E. coli ST131 and multi-drug resistance ESBL-producing, as well as New Delhi metallo-β-lactamase-1 (NDM-1) and Klebsiella pneumoniae carbapenemases-2 (KPC-2) bearing K. pneumoniae ST11 are spreading in patients with pneumonia in hospital.

Prevalence and diversity of blaTEM, blaSHV and blaCTX-M variants among multidrug resistant Klebsiella spp. from an urban riverine environment in India

In the present study, we have investigated prevalence and diversity of ESBL genes among Klebsiella isolates obtained from highly polluted stretch of river Yamuna, India. Phenotypic screenings of 116 Klebsiella isolates revealed ~30% were positive for ESBL production. Antibiotic profiling showed multidrug resistance phenotype among 90% isolates. Prevalence of blaTEM, blaSHV and blaCTX-M genes were found to be 57, 54 and 48% respectively. Furthermore, we identified eight variants of blaSHV (SHV-1, SHV-11, SHV-27, SHV-28, SHV-38, SHV-61, SHV-144, SHV-148), three each of blaTEM (TEM-1, TEM-116, TEM-206) and blaCTX-M (CTX-M-15, CTX-M-55, CTX-M-188) among Klebsiella spp. Co-occurrence of blaTEM, blaSHV and blaCTX-M (any two or all three) was observed among 45% Klebsiella isolates. Occurrence of blaCTX-M-188 and blaTEM-206 in environmental isolates of K. pneumoniae has not been reported earlier. Identification of blaTEM-206, blaSHV-27 and blaSHV-144 from Klebsiella spp. and blaTEM-116 from K. quasipneumoniae and K. variicola is the first report from India.

Resistance mechanisms and population structure of highly drug resistant Klebsiella in Pakistan during the introduction of the carbapenemase NDM-1

Klebsiella pneumoniae is a major threat to public health with the emergence of isolates resistant to most, if not all, useful antibiotics. We present an in-depth analysis of 178 extended-spectrum beta-lactamase (ESBL)-producing K. pneumoniae collected from patients resident in a region of Pakistan, during the period 2010-2012, when the now globally-distributed carbapenemase bla-NDM-1 was being acquired by Klebsiella. We observed two dominant lineages, but neither the overall resistance profile nor virulence-associated factors, explain their evolutionary success. Phenotypic analysis of resistance shows few differences between the acquisition of resistance genes and the phenotypic resistance profile, including beta-lactam antibiotics that were used to treat ESBL-positive strains. Resistance against these drugs could be explained by inhibitor-resistant beta-lactamase enzymes, carbapenemases or ampC type beta-lactamases, at least one of which was detected in most, but not all relevant strains analysed. Complete genomes for six selected strains are reported, these provide detailed insights into the mobile elements present in these isolates during the initial spread of NDM-1. The unexplained success of some lineages within this pool of highly resistant strains, and the discontinuity between phenotypic resistance and genotype at the macro level, indicate that intrinsic mechanisms contribute to competitive advantage and/or resistance.

Pulsed-Field Gel Electrophoresis Used for Typing of Extended-Spectrum-β-Lactamases- Producing Escherichia coli Isolated from Infant ҆S Respiratory and Digestive System

Escherichia coli infections are becoming increasingly difficult to treat because of emerging antimicrobial resistance, mostly to expanded-spectrum cephalosporins, due to the production of extended-spectrum β-lactamases (ESBLs).Despite extensive studies of ESBL- producing E.coli in adult patients, there is a lack of information about the epidemiology and spread of ESBL organisms in pediatric population. The aim of this study was to examine the gastrointestinal tract as an endogenous reservoir for the respiratory tract colonization with ESBL- E. coli in children, hospitalized because of the severity of the respiratory illness. The study group consists of 40 children with ESBL-producing E. coli strains isolated from the sputum and from the rectal samples. A control group of 15 E. coli isolated from rectal swabs of healthy children were included in the analysis. The comparison of the strains was done by using antimicrobial susceptibility patterns of the stains, and pulsed field gel electrophoresis was performed for molecular typing, using XbaI digestion. 90% of the compared pairs of strains in the study group were with identical antimicrobial susceptibility patterns and indistinguishable in 79.2% by the obtained PFGE – profiles.33.3% (5/15) of confirmed E. coli strains from the control group were found to be ESBL – producers. Resulting band profiles of all isolates demonstrated presence of 12 pulsotypes, with 100% similarity within the pulsotypes. Although, some isolates obtained from different patients were genetically indistinguishable, these strains were not hospital acquired, as none of the patients satisfied the criteria for hospital acquired pneumonia, and there was a lack of an obvious transmission chain. All ESBL –E. coli isolated from sputum in clinical cases were obtained from patients under the age of one. According to the resistance profile of the compared pairs and the PFGE comparison of all isolates, it can be concluded that the gastrointestinal tract is the main reservoir of ESBL-E. coli. Small age in infants is a risk factor for translocation of bacteria, enabling the colonization of the respiratory tract.

Prevalence and mechanisms of extended-spectrum cephalosporin resistance in clinical and fecal Enterobacteriaceae isolates from dogs in Ontario, Canada

There is little information on the genetic basis of resistance to the critically important extended-spectrum cephalosporins (ESCs) in Enterobacteriaceae from dogs in Canada. This study assessed the frequency of ESC resistance in Enterobacteriaceae isolated from dogs in Ontario and the distribution of major ESC resistance genes in these bacteria. A total of 542 Enterobacteriaceae were isolated from 506 clinical samples from two diagnostic laboratories in Ontario. Eighty-eight ESC-resistant Enterobacteriaceae and 217 Escherichia coli were isolated from 234 fecal samples from dogs collected at leash-free dog parks. These fecal isolates were tested for ESC resistance along with the clinical isolates. Isolates with reduced ESC susceptibility were screened for bla_CMY, bla_CTX-M, and bla_SHV, and all CTX-M-positive isolates underwent whole-genome sequencing. The prevalence of ESC resistance in clinical Enterobacteriaceae was 10.4%. The average frequency of fecal carriage of ESC-resistant Enterobacteriaceae in healthy dogs was 26.5%. The majority of ESC-resistant isolates were E. coli and the other major Enterobacteriaceae carrying ESC resistance genes were Klebsiella pneumoniae and Proteus mirabilis. The results show that the same ESC resistance genes can be found in clinical and fecal Enterobacteriaceae in dogs. The identified E. coli sequence types (including ST131 and ST648) and CTX-M variants (including CTX-M-14, -15, and -27) support the hypothesis of transfer of resistant bacteria between humans and dogs. CTX-M-1 was frequently found in canine fecal Enterobacteriaceae, while it is still rare in human Enterobacteriaceae in Canada, thus suggesting transfer of resistant bacteria to dogs from food animals or other sources.

A Review of SHV Extended-Spectrum β-Lactamases: Neglected Yet Ubiquitous

β-lactamases are the primary cause of resistance to β-lactams among members of the family Enterobacteriaceae. SHV enzymes have emerged in Enterobacteriaceae causing infections in health care in the last decades of the Twentieth century, and they are now observed in isolates in different epidemiological settings both in human, animal and the environment. Likely originated from a chromosomal penicillinase of Klebsiella pneumoniae, SHV β-lactamases currently encompass a large number of allelic variants including extended-spectrum β-lactamases (ESBL), non-ESBL and several not classified variants. SHV enzymes have evolved from a narrow- to an extended-spectrum of hydrolyzing activity, including monobactams and carbapenems, as a result of amino acid changes that altered the configuration around the active site of the β -lactamases. SHV-ESBLs are usually encoded by self-transmissible plasmids that frequently carry resistance genes to other drug classes and have become widespread throughout the world in several Enterobacteriaceae, emphasizing their clinical significance.

High Diversity of CTX-M Extended-Spectrum β-Lactamases in Municipal Wastewater and Urban Wetlands

The CTX-M-type extended-spectrum β-lactamases (ESBLs) present a serious public health threat as they have become nearly ubiquitous among clinical gram-negative pathogens, particularly the enterobacteria. To aid in the understanding and eventual control of the spread of such resistance genes, we sought to determine the diversity of CTX-M ESBLs not among clinical isolates, but in the environment, where weaker and more diverse selective pressures may allow greater enzyme diversification. This was done by examining the CTX-M diversity in municipal wastewater and urban coastal wetlands in southern California, United States, by Sanger sequencing of polymerase chain reaction amplicons. Of the five known CTX-M phylogroups (1, 2, 8, 9, and 25), only genes from groups 1 and 2 were detected in both wastewater treatment plants (WWTPs), and group 1 genes were also detected in one of the two wetlands after a winter rain. The highest relative abundance of blaCTX-M group 1 genes was in the sludge of one WWTP (2.1 × 10(-4) blaCTX-M copies/16S rRNA gene copy). Gene libraries revealed surprisingly high nucleotide sequence diversity, with 157 new variants not found in GenBank, representing 99 novel amino acid sequences. Our results indicate that the resistomes of WWTPs and urban wetlands contain diverse blaCTX-M ESBLs, which may constitute a mobile reservoir of clinically relevant resistance genes.

Occurrence of ESBL-Producing Escherichia coli in Livestock and Farm Workers in Mecklenburg-Western Pomerania, Germany

In recent years, extended-spectrum β-lactamases (ESBL) producing bacteria have been found in livestock, mainly as asymptomatic colonizers. The zoonotic risk for people working in close contact to animal husbandry has still not been completely assessed. Therefore, we investigated the prevalence of ESBL-producing Escherichia spp. in livestock animals and workers to determine the potential risk for an animal-human cross-transmission.In Mecklenburg-Western Pomerania, northeast Germany, inguinal swabs of 73 individuals with livestock contact from 23 different farms were tested for ESBL-producing Escherichia spp. Two pooled fecal samples per farm of animal origin from 34 different farms (17 pig farms, 11 cattle farms, 6 poultry farms) as well as cloacal swabs of 10 randomly selected broilers or turkeys were taken at each poultry farm. For identification, selective chromogenic agar was used after an enrichment step. Phenotypically ESBL-producing isolates (n = 99) were tested for CTX-M, OXA, SHV and TEM using PCR, and isolates were further characterized using multilocus sequence typing (MLST). In total, 61 diverse isolates from different sources and/or different MLST/PCR results were acquired. Five farm workers (three from cattle farms and two from pig farms) harbored ESBL-producing E. coli. All human isolates harbored the CTX-M β-lactamase; TEM and OXA β-lactamases were additionally detected in two, resp. one, isolates. ESBL-producing Escherichia spp. were found in fecal samples at pig (15/17), cattle (6/11) and poultry farms (3/6). In total, 70.6% (24/36) of the tested farms were ESBL positive. Furthermore, 9 out of 60 cloacal swabs turned out to be ESBL positive. All isolated ESBL-producing bacteria from animal sources were E. coli, except for one E. hermanii isolate. CTX-M was the most prevalent β-lactamase at cattle and pig farms, while SHV predominated in poultry. One human isolate shared an identical MLST sequence type (ST) 3891 and CTX-M allele to the isolate found in the cattle fecal sample from the same farm, indicating a zoonotic transfer. Two other pairs of human-pig and human-cattle E. coli isolates encoded the same ESBL genes but did not share the same MLST ST, which may indicate horizontal resistance gene transfer. In summary, the study shows the high prevalence of ESBL-producing E.coli in livestock in Mecklenburg- Western Pomerania and provides the risk of transfer between livestock and farm workers.

Molecular Analysis of Antibiotic Resistance Determinants and Plasmids in Malaysian Isolates of Multidrug Resistant Klebsiella pneumoniae

Infections caused by multidrug resistant Klebsiella pneumoniae have been increasingly reported in many parts of the world. A total of 93 Malaysian multidrug resistant K. pneumoniae isolated from patients attending to University of Malaya Medical Center, Kuala Lumpur, Malaysia from 2010-2012 were investigated for antibiotic resistance determinants including extended-spectrum beta-lactamases (ESBLs), aminoglycoside and trimethoprim/sulfamethoxazole resistance genes and plasmid replicons. CTX-M-15 (91.3%) was the predominant ESBL gene detected in this study. aacC2 gene (67.7%) was the most common gene detected in aminoglycoside-resistant isolates. Trimethoprim/sulfamethoxazole resistance (90.3%) was attributed to the presence of sul1 (53.8%) and dfrA (59.1%) genes in the isolates. Multiple plasmid replicons (1-4) were detected in 95.7% of the isolates. FIIK was the dominant replicon detected together with 13 other types of plasmid replicons. Conjugative plasmids (1-3 plasmids of ~3-100 kb) were obtained from 27 of 43 K. pneumoniae isolates. An ESBL gene (either CTX-M-15, CTX-M-3 or SHV-12) was detected from each transconjugant. Co-detection with at least one of other antibiotic resistance determinants [sul1, dfrA, aacC2, aac(6ˊ)-Ib, aac(6ˊ)-Ib-cr and qnrB] was noted in most conjugative plasmids. The transconjugants were resistant to multiple antibiotics including β-lactams, gentamicin and cotrimoxazole, but not ciprofloxacin. This is the first study describing the characterization of plasmids circulating in Malaysian multidrug resistant K. pneumoniae isolates. The results of this study suggest the diffusion of highly diverse plasmids with multiple antibiotic resistance determinants among the Malaysian isolates. Effective infection control measures and antibiotic stewardship programs should be adopted to limit the spread of the multidrug resistant bacteria in healthcare settings.

Prevalence and characterization of extended-spectrum-β-lactamase-producing Escherichia coli and Klebsiella pneumoniae in ready-to-eat vegetables

The objective of this investigation was to determine the prevalence and characteristics of extended-spectrum-β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae in ready-to-eat (RTE) vegetables. A total of 189 RTE vegetable samples (91 sprouts and 98 mixed salads) were collected in a retail market in South Korea from October 2012 to February 2013. The prevalence of ESBL-producing E. coli and K. pneumoniae was 10.1%. Of these, 94.7% were from the sprout samples. All isolates were resistant to cefotaxime, and many of the ESBL producers were also resistant to non-β-lactam antibiotics, including gentamicin, trimethoprim/sulfamethoxazole, and ciprofloxacin (73.7%, 63.2%, and 26.3% respectively). TEM-1, SHV-1, -2, -11, -12, -27, -28 and -61, and CTX-M-14, -15 and -55 β-lactamases were detected alone or in combination. The genetic platforms of all CTX-M producing isolates were ISEcp1-blaCTX-M-orf477 and ISEcp1-blaCTX-M-IS903 in CTX-M groups 1 and 9, respectively. To our knowledge, this is the first report of the prevalence and characterization of ESBL-producing E. coli and K. pneumoniae isolated from RTE vegetables. The results of this study indicate that RTE vegetables, sprouts, in particular, may play a role in spreading antimicrobial resistant bacteria and ESBL genes to humans.

Expansion of ESBL-producing Klebsiella pneumoniae in hospitalized patients: a successful story of international clones (ST15, ST147, ST336) and epidemic plasmids (IncR, IncFIIK)

The aim of this study was to characterize by a multi-level approach extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae isolates other than E. coli from Portuguese hospitals. Eighty-eight ESBL-producing clinical isolates (69 Klebsiella pneumoniae, 13 Enterobacter cloacae complex, 3 Klebsiella oxytoca, 1 Enterobacter asburiae, 1 Proteus mirabilis and 1 Serratia marcescens) recovered from hospitals located in the North (A) or Centre (B, C) regions during two time periods (2006-7 and 2010) were analyzed. Standard methods were used for bacterial identification, antibiotic susceptibility testing, ESBL characterization, clonal (PFGE, MLST) and plasmid (S1-PFGE, I-CeuI-PFGE, replicon typing, hybridization) analysis. Isolates produced mostly CTX-M-15 (47%) or SHV-12 (30%), and less frequently other SHV- (15%; SHV-2, -5, -28, -55, -106) or TEM- (9%; TEM-10, -24, -199)-types, with marked local and temporal variations. The increase of CTX-M-15 and diverse SHV ESBL-types observed in Hospital A was associated with the amplification of multidrug-resistant (MDR) K. pneumoniae epidemic clones (ST15, ST147, ST336). SHV-12 and TEM-type ESBLs were mostly identified in diverse isolates of different Enterobacteriaceae species in Hospitals B and C in 2006-7. Particular plasmid types were linked to blaCTX-M-15 (IncR or non-typeable plasmids), blaSHV-12 (IncR or IncHI2), blaSHV-28/-55/-106 (IncFIIK1 or IncFIIK5), blaTEM-10 (IncL/M) or blaTEM-24 (IncA/C), mostly in epidemic clones. In our country, the amplification of CTX-M-15 and diverse SHV-type ESBL among non-E. coli Enterobacteriaceae is linked to international MDR K. pneumoniae clones (ST15, ST147, ST336) and plasmid types (IncR, IncFIIK). Furthermore, we highlight the potential of IncFIIK plasmids (here firstly associated with blaSHV-2/-28/-55/-106) to disseminate as antibiotic resistance plasmids.

Diversity of extended-spectrum and plasmid-mediated AmpC β-lactamases in Enterobacteriaceae isolates from Portuguese health care facilities

A group of 124 Enterobacteriaceae isolates resistant to third generation cephalosporins, and collected in distinct health care facilities of different Portuguese regions was analysed. The great majority of the isolates were also resistant to fourth generation cephalosporins (83.9%), monobactam (96%), amoxicillin plus clavulanic acid (85.5%), and piperacillin plus tazobactam (66.9%). Overall, 84.7% (105/124) were multidrug resistant. Molecular methods enabled us to identify 86.3% (107/124) extended-spectrum β-lactamases (ESBL) producers, revealing a diversity of class A β-lactamases from different families, like TEM (TEM-1, TEM-10, TEM-24, and TEM-52), SHV (SHV-1, SHV-12, and SHV-28), CTX-M (CTX-M-1, CTX-M-9, CTX-M-14, CTX-M-15, and CTXM-32), and GES (GES-1). We have also detected class C enzymes like plasmid-mediated AmpC β-lactamases (PMAβs, DHA-1, and CMY-2) and chromosomal AmpCs in Enterobacter and Citrobacter spp. The PMAβ genetic context mapping suggests association with mobile elements, plasmid importation and the potential emergence of these β-lactamases. The most prevalent β-lactamase detected was CTX-M-15 (66.1%) and in 41.1% of the isolates it was associated with TEM-, OXA-type β-lactamases and Aac(6)᾿Ib-cr, which might indicate that the respective genotype has settled in our country. Indeed, CTX-M-15 was distributed amongst distinct clinical settings of several health care facilities (93.5%) from various regions. We provide evidence of a concerning clinical situation that includes vast occurrence of ESBLs, the settling of CTX-M β-lactamases, and the report of plasmidic and chromosomal AmpC in Portugal.

Molecular characterization of ESBL-producing Enterobacteriaceae in northern Portugal

Extended-spectrum β-lactamases (ESBLs) prevalence was studied in the north of Portugal, among 193 clinical isolates belonging to citizens in a district in the boundaries between this country and Spain from a total of 7529 clinical strains. In the present study we recovered some members of Enterobacteriaceae family, producing ESBL enzymes, including Escherichia coli (67.9%), Klebsiella pneumoniae (30.6%), Klebsiella oxytoca (0.5%), Enterobacter aerogenes (0.5%), and Citrobacter freundii (0.5%). β -lactamases genes blaTEM, blaSHV, and blaCTX-M were screened by polymerase chain reaction (PCR) and sequencing approaches. TEM enzymes were among the most prevalent types (40.9%) followed by CTX-M (37.3%) and SHV (23.3%). Among our sample of 193 ESBL-producing strains 99.0% were resistant to the fourth-generation cephalosporin cefepime. Of the 193 isolates 81.3% presented transferable plasmids harboring bla ESBL genes. Clonal studies were performed by PCR for the enterobacterial repetitive intragenic consensus (ERIC) sequences. This study reports a high diversity of genetic patterns. Ten clusters were found for E. coli isolates and five clusters for K. pneumoniae strains by means of ERIC analysis. In conclusion, in this country, the most prevalent type is still the TEM-type, but CTX-M is growing rapidly.

A simple multiplex PCR for assessing prevalence of extended-spectrum β-lactamases producing Klebsiella pneumoniae in Intensive Care Units of a referral hospital in Shiraz, Iran

OBJECTIVE

To identify three common genes (blaTEM, blaSHV and blaCTX-M) responsible for ESBL production in Klebsiella pneumoniae (K. pneumoniae)isolated from Intensive Care Units of Namazi Hospital, Shiraz, Iran.

METHODS

A total of 60 non-repetitive nosocomial isolates from 60 patients were selected during 2009-2010. The phenotypic identification of ESBL production was confirmed by Double Disk Synergy Test (DDST) according to CLSI guidelines. The ESBL's genotype was then analyzed by multiplex PCR of blaTEM, blaSHV and blaCTX-M genes and DNA sequencing.

RESULTS

The primary susceptibility tests of K. pneumoniae showed that among 10 examined antibiotics, the most resistant and susceptible antibiotics identified in this study were ampicillin and imipenem, respectively. The phenotypic determination of ESBL by DDST showed that 60% (n=36) of isolates produced ESBL. Multiplex PCR of genes among K. pneumoniae isolates showed that 39% (n=18) of them have TEM, 39% (n=18) of them have both CTX-M and TEM and 13% (n=8) of them have TEM, SHV, CTX-M.

CONCLUSIONS

Our findings reveal the high prevalence (60%) of ESBL producing K. pneumoniae from ICU patients along with a new pattern of blaTEMdistribution differ from other countries.

Characterization of novel plasmid-mediated β-lactamases (SHV-167 and ACT-16) associated with New Delhi metallo-β-lactamase-1 harbouring isolates from neonates in India

Neonatal sepsis due to carbapenem-resistant bacteria is difficult to treat due to limited therapeutic options. The detection of the new carbapenemase New Delhi metallo-β-lactamase-1 (NDM-1) from neonates has further complicated the situation (Roy et al., 2011a). The potent metallo-β-lactamase NDM-1 efficiently hydrolyses all classes of β-lactam antibiotics (penicillins, cephalosporins and carbapenems) and is also associated with multiple determinants that enable the bacteria to become resistant to other antibiotic classes (Nordmann et al., 2011). In the presence of NDM-1 other β-lactamases may go unobserved because of the spectrum of activity of NDM-1 against all β-lactam antibiotics. Thus, under the canopy of the NDM-1 these β-lactamases also get the opportunity to spread. This communication reports association of two novel β-lactamases, SHV-type β-lactamase (SHV-167) and AmpC-type β-lactamase (ACT-16), in two NDM-1-carrying Enterobacteriaceae isolated from the blood of two septicaemic neonates admitted to a neonatal intensive care unit.

Increased frequency of integrons and β-lactamase-coding genes among extraintestinal Escherichia coli isolated with a 7-year interval

We analyzed the level of antimicrobial resistance, and the presence of integrons and β-lactamase-coding genes in 69 clinically relevant Escherichia coli strains originating from extraintestinal infections isolated in 1999–2001 and 2008–2010. Comparison of the two groups showed significant differences in drug resistance frequency, and the presence of integron and β-lactamase-coding genes. The frequency of resistance to all antimicrobials beside imipenem, streptomycin, piperacillin/tazobactam, and sulfamethoxazole increased significantly, especially towards aminoglycosides, β-lactams and fluoroquinolones. Similarly, we noticed an increase in the number of strains with integrons from 31.6 to 80.7 %. The presence of integrase genes was associated with elevated frequency of resistance to each antimicrobial tested besides imipenem, piperacillin/tazobactam and ceftazidime. The presence of integrons was also associated with multidrug resistance phenotype. The genetic content of integrons comprised genes determining resistance toward aminoglycosides, sulfonamides and trimethoprim. Moreover, we noticed a significant increase in the frequency of bla_CTX-M β-lactamases, with appearance of bla_CTX-M-15 variant and newer plasmid-encoded β-lactamases like CMY-15 and DHA. The emergence of strains resistant to several classes of antimicrobials and carrying integrons, ESBL and AmpC β-lactamase-coding genes may predict the spread of isolates with limited treatment options.

Epidemiology and genetics of CTX-M extended-spectrum β-lactamases in Gram-negative bacteria

CTX-M enzymes, the plasmid-mediated cefotaximases, constitute a rapidly growing family of extended-spectrum β-lactamases (ESBLs) with significant clinical impact. CTX-Ms are found in at least 26 bacterial species, particularly in Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis. At least 109 members in CTX-M family are identified and can be divided into seven clusters based on their phylogeny. CTX-M-15 and CTX-M-14 are the most dominant variants. Chromosome-encoded intrinsic cefotaximases in Kluyvera spp. are proposed to be the progenitors of CTX-Ms, while ISEcp1, ISCR1 and plasmid are closely associated with their mobilization and dissemination.

Emergence and risk factors of β-lactamase-mediated resistance to oxyimino-β-lactams in Enterobacteriaceae isolates

We studied 193 Enterobacteriaceae isolates presenting diminished susceptibility to oxyimino-cephalosporins recovered in a Portuguese hospital (2004-2008). CTX-M-3 producers, firstly detected in Portugal, were associated with a Klebsiella pneumoniae microepidemic clone. Production of CTX-M-type enzymes (CTX-M-1/-3/-9/-14/-15/-32), age ≥65 years, and nosocomial infection were risk factors for higher nonsusceptibility to oxyimino-β-lactams. CMY-2 and DHA-1 β-lactamases were only identified in 1% of isolates.

Characterization of the inhibitor-resistant SHV β-lactamase SHV-107 in a clinical Klebsiella pneumoniae strain coproducing GES-7 enzyme

The clinical Klebsiella pneumoniae INSRA6884 strain exhibited nonsusceptibility to all penicillins tested (MICs of 64 to >2,048 μg/ml). The MICs of penicillins were weakly reduced by clavulanate (from 2,048 to 512 μg/ml), and tazobactam restored piperacillin susceptibility. Molecular characterization identified the genes bla(GES-7) and a new β-lactamase gene, bla(SHV-107), which encoded an enzyme that differed from SHV-1 by the amino acid substitutions Leu35Gln and Thr235Ala. The SHV-107-producing Escherichia coli strain exhibited only a β-lactam resistance phenotype with respect to amoxicillin, ticarcillin, and amoxicillin-clavulanate combination. The kinetic parameters of the purified SHV-107 enzyme revealed a high affinity for penicillins. However, catalytic efficiency for these antibiotics was lower for SHV-107 than for SHV-1. No hydrolysis was detected against oxyimino-β-lactams. The 50% inhibitory concentration (IC(50)) for clavulanic acid was 9-fold higher for SHV-107 than for SHV-1, but the inhibitory effects of tazobactam were unchanged. Molecular dynamics simulation suggested that the Thr235Ala substitution affects the accommodation of clavulanate in the binding site and therefore its inhibitory activity.

Antibiotic Collateral Damage: Resistance and Antibiotic-Associated Diarrhea

The purpose of this review is to describe dilemmas associated with antibiotic collateral damage and provide clinical pharmacists with information to improve antibiotic utilization. The clinical use of antibiotics has been associated with acquisition and spread of nosocomial pathogens and multidrug-resistant strains, such as extended-spectrum beta-lactamases, AmpC hyper-producers, carbapenemases, and resistant gram-positive organisms. The mobility of plasmid-mediated resistance, such as extended-spectrum beta-lactamases and the more recently isolated Klebsiella pneumoniae carbapenemases, have been well-demonstrated with worldwide distribution across several different species. The challenges surrounding antibiotic-associated diarrhea, particularly Clostridium difficile infection (CDI), continue to evolve with outbreaks of hypervirulent strains linked to the use of less commonly implicated antibiotics. Published literature was searched and reviewed using PubMed. Undesirable attributes related to antibiotic use can have broad consequences in addition to their effect on individual patients. This collateral damage can evolve over time, and prescribers must be aware of current concerns and be diligent in their judicious use of antibiotics.

Comparative genomics of Klebsiella pneumoniae strains with different antibiotic resistance profiles

There is a global emergence of multidrug-resistant (MDR) strains of Klebsiella pneumoniae, a Gram-negative enteric bacterium that causes nosocomial and urinary tract infections. While the epidemiology of K. pneumoniae strains and occurrences of specific antibiotic resistance genes, such as plasmid-borne extended-spectrum β-lactamases (ESBLs), have been extensively studied, only four complete genomes of K. pneumoniae are available. To better understand the multidrug resistance factors in K. pneumoniae, we determined by pyrosequencing the nearly complete genome DNA sequences of two strains with disparate antibiotic resistance profiles, broadly drug-susceptible strain JH1 and strain 1162281, which is resistant to multiple clinically used antibiotics, including extended-spectrum β-lactams, fluoroquinolones, aminoglycosides, trimethoprim, and sulfamethoxazoles. Comparative genomic analysis of JH1, 1162281, and other published K. pneumoniae genomes revealed a core set of 3,631 conserved orthologous proteins, which were used for reconstruction of whole-genome phylogenetic trees. The close evolutionary relationship between JH1 and 1162281 relative to other K. pneumoniae strains suggests that a large component of the genetic and phenotypic diversity of clinical isolates is due to horizontal gene transfer. Using curated lists of over 400 antibiotic resistance genes, we identified all of the elements that differentiated the antibiotic profile of MDR strain 1162281 from that of susceptible strain JH1, such as the presence of additional efflux pumps, ESBLs, and multiple mechanisms of fluoroquinolone resistance. Our study adds new and significant DNA sequence data on K. pneumoniae strains and demonstrates the value of whole-genome sequencing in characterizing multidrug resistance in clinical isolates.

Virulence properties of extended spectrum β-lactamase-producing Klebsiella species in meat samples

The present study was carried out to identify virulence properties (siderophores, serum resistance, and hemolysin) and antibiotic resistance in extended spectrum β-lactamase (ESBL)-producing Klebsiella isolates from 60 calf and chicken meat samples purchased from various supermarkets in Ankara, Turkey. Of the 45 Klebsiella isolates, 24 (53%) were identified as K. oxytoca and 21 (47%) were identified as K. pneumoniae. A high proportion of Klebsiella isolates had virulence factors such as hemolytic activity (67%), siderophore production (44%), and serum resistance (38%). The double-disk synergy test was used to determine ESBL production. ESBL production was detected in 13 (29%) of the 45 Klebsiella isolates. Resistance to 14 antimicrobials was tested in all Klebsiella isolates by the disk diffusion method. All isolates were resistant to two or more antimicrobial agents. All ESBL-producing Klebsiella isolates were highly resistant to cephalosporins and monobactams. Our findings indicate that meat and its products represent potential hazardous sources of multidrug-resistant and virulent Klebsiella species.

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.

Rapid genotyping of Achromobacter xylosoxidans, Acinetobacter baumannii, Klebsiella pneumoniae, Pseudomonas aeruginosa and Stenotrophomonas maltophilia isolates using melting curve analysis of RAPD-generated DNA fragments (McRAPD)

Typing of bacteria is important for monitoring newly emerging pathogens and for examining local outbreaks. We evaluated the randomly amplified polymorphic DNA technique in combination with melting curve analysis (McRAPD) of the amplified DNA fragments to genotype isolates from five Gram-negative species, i.e. Achromobacter xylosoxidans, Acinetobacter baumannii, Klebsiella pneumoniae, Pseudomonas aeruginosa and Stenotrophomonas maltophilia. By determining the melting temperature peaks of the amplified DNA fragments, we were able to distinguish the different genotypes of isolates, as they had been assessed by other genotyping techniques, i.e. agarose gel electrophoresis of RAPD fragments, multilocus sequence typing and/or AFLP™. According to our results, McRAPD may offer the possibility of genotyping a limited number of bacterial isolates, e.g. in case of suspicion of hospital outbreak, via a less costly, more rapid, less laborious and more user-friendly technique than RAPD followed by electrophoresis.

[CTX-M-15-producing Klebsiella pneumoniae: a change in the epidemiology of ESBL]

Klebsiella pneumoniae is frequently involved in nosocomial outbreaks worldwide. High level of resistance is common for these bacteria leading to reduce antibiotic treatments and prolonged hospital stay for patients. Resistance determinants are often located on plasmids. During the 1980-1990s, ESBL encoding genes belonged to the TEM and SHV type. From the early 2000s, a new trend was observed with ESBL of the CTX-M type being increasingly described in K. pneumoniae, and more particularly CTX-M-15.