Development of High-Level Carbapenem Resistance inKlebsiella pneumoniaeAmong Patients with Prolonged Hospitalization and Carbapenem Exposure

Carbapenem resistance in extensively drug-resistant Salmonella enterica serovar Agona and AmpC β-lactamase-producing S. Infantis

IMPORTANCE

Carbapenem resistance arising from the loss of porins is commonly observed in extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase-producing strains of certain Enterobacteriaceae genera, including Klebsiella pneumoniae, Escherichia coli, and Pseudomonas aeruginosa. However, this resistance mechanism is rarely reported in the Salmonella genus. To address this knowledge gap, our study offers genetic evidence demonstrating that the loss of two specific porins (OmpC_378 and OmpD) is crucial for the development of carbapenem resistance in Salmonella ESBL and AmpC β-lactamase-producing strains. Furthermore, our findings reveal that most Salmonella serovars carry seven porin parathologs, with OmpC_378 and OmpD being the key porins involved in the development of carbapenem resistance in Salmonella strains.

Klebsiella pneumoniae Harboring Carbapenemase Genes in Taiwan: Its Evolution over 20 Years, 1998-2019

Klebsiella pneumoniae (K. pneumoniae) is an important pathogen causing various types of human infections in Taiwan. Carbapenemases have increasingly been reported in Enterobacterales in the past two decades. Carbapenemase-producing K. pneumoniae (CPKP), a major resistance concern that has emerged during the last decade, has become a global threat, with its related infections associated with high morbidity and mortality; however, therapeutic options for CPKP-associated infections are limited. Carbapenemases - including K. pneumoniae carbapenemases (KPC)-2, New Delhi metallo-β-lactamase (NDM)-1, Verona integron-encoded metallo-β-lactamase (VIM)-1, imipenemase (IMP)-1, and oxacillinase (OXA)-48 - have been reported worldwide, with a marked prevalence in different countries or areas of the world. Understanding the epidemiology of carbapenemase producers is important for the prevention of their expansion. This review examined the evolution of CPKP in the last two decades to better understand the role of CPKP in Taiwan. It discovered that the endemicity has changed from IMP-8, NDM-1 and VIM-1 to the most common KPC-2 and rapidly emerging OXA-48. Resistance epidemiology, genetic background, virulence factors, therapy, and outcomes are discussed in this paper.

Infection caused by Klebsiella pneumoniae ST11 in a patient after craniectomy

Klebsiella pneumoniae infections have always been an important problem in public health, but today, the increasing resistance of these bacteria to antibiotics due to β-lactamases production has renewed interest in K. pneumoniae infections. The aim of the study was to present a case of a neurosurgical patient with multidrug-resistant K. pneumoniae ST11 infection after craniectomy. Four K. pneumoniae isolates from various clinical materials of the patient undergone identification and susceptibility testing with the Vitek2 system. Tests for β-lactamases production were performed according to EUCAST guidelines. Strains were analyzed for bla genes responsible for β-lactamase production (bla_TEM, bla_SHV, bla_CTX-M, bla_VIM, bla_IMP, bla_NDM, bla_KPC, bla_OXA-48) using PCR. Moreover, the genetic relatedness of these isolates was determined by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). All tested strain presented multidrug resistance. The highest susceptibility was observed for imipenem, meropenem, and ertapenem. The strain isolated from the nervous system was ESBL-positive with bla_SHV-11, bla_TEM-1, and bla_CTX-M-15 genes. Additionally, the strain from urine was bla_KPC-3-positive. Molecular typing revealed that all strains belonged to the same clone and identified two PFGE profiles. The analysis of MLST allelic profile showed that tested K. pneumoniae strains belonged to ST11. Identification of ST11 K. pneumoniae as etiological factor of infection unfavorably impacts on prognosis among neurosurgical patient after craniectomy.

In vitro activity of flomoxef against extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae in Korea

To find an alternative regimen for the treatment of extended-spectrum β-lactamase (EBSL)-producing Enterobacteriaceae infections, we examined the in vitro activity of flomoxef against Escherichia coli and Klebsiella pneumoniae having CTX-M-1 group and/or CTX-M-9 group ESBLs. Boronic acid disk methods and polymerase chain reaction amplification were used to detect for ESBL, and AmpC β-lactamase and AmpC β-lactamase co-producers were excluded. Minimum inhibitory concentrations (MICs) were determined for flomoxef by broth microdilution. One hundred seventy-six isolates (E. coli, n = 93 and K. pneumoniae, n = 83) were analyzed for susceptibility test. A total of 94.3% (166/176) of isolates were susceptible to flomoxef (MIC₅₀/MIC₉₀ were 0.5/8 μg/mL); 98.9% of the ESBL-producing E. coli (MIC₅₀/MIC₉₀ were 1/4 μg/mL) and 89.2% of the ESBL-producing K. pneumoniae (MIC₅₀/MIC₉₀ were 0.5/16 μg/mL) were susceptible to flomoxef. Flomoxef has good in vitro activity against ESBL-producing E. coli and K. pneumoniae and could be considered as an alternative for infections caused by these organisms.

Molecular epidemiology of the emerging ceftriaxone resistant non-typhoidal Salmonella in southern Taiwan

BACKGROUND/PURPOSE

The increasing trend of ceftriaxone resistant non-typhoidal Salmonella (NTS) worldwide is of serious concern, however, data is lacked in southern Taiwan.

METHODS

Salmonella isolates were collected at a regional hospital in Kaohsiung during 2004-2013. Ceftriaxone resistant NTS isolates were further characterized for beta-lactamases, typed by pulsed field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and their plasmids were analyzed by PCR replicon typing and plasmid mutilocus sequence typing.

RESULTS

Among 528 NTS isolates, the most common serogroup is serogroup B (44.9%), followed by serogroup D, and serogroup C. Eleven (2.1%) isolates were resistant to ceftriaxone and were distributed in three peak periods (2010, 2011, and 2013). PFGE and MLST revealed the ten serogroup B isolates were of two clones. Beta-lactamase genes were detected in 10 of the 11 isolates, including CMY-2 (5 isolates), TEM-1 (2), CTX-M-14 (1), and 2 isolates carried both TEM-1 and CMY-2. Plasmid incompatibility types were identified in 9 (81.8%) isolates; three were IncI1, three was IncHI2, one was IncFIB and two had both replicons of IncI1 and IncHI2. The only ESBL gene bla_CTM-X-14 was found in an isolate with plasmid belonged to IncHI2, which has not been reported in NTS in Taiwan before. Most MLST types and plasmid MLST types of NTS isolates in this study are different from those in northern Taiwan.

CONCLUSION

Though clonal spread of ceftriaxone resistant NTS was suggested by PFGE and MLST, plasmid characterization and beta-lactamase detection revealed their plasmid types and beta-lactamase types were different.

Antimicrobial Stewardship Opportunities in Critically Ill Patients with Gram-Negative Lower Respiratory Tract Infections: A Multicenter Cross-Sectional Analysis

INTRODUCTION

Lower respiratory tract infections (LRTIs) are a major cause of morbidity and death. Because of changes in how LRTIs are defined coupled with the increasing prevalence of drug resistance, there is a gap in knowledge regarding the current burden of antimicrobial use for Centers for Disease Control and Prevention (CDC)-defined LRTIs. We describe the infection characteristics, antibiotic consumption, and clinical and economic outcomes of patients with Gram-negative (GN) LRTIs treated in intensive care units (ICUs).

METHODS

This was a retrospective, observational, cross-sectional study of adult patients treated in ICUs at two large academic medical centers in metropolitan Detroit, Michigan, from October 2013 to October 2015. To meet the inclusion criteria, patients must have had CDC-defined LRTI caused by a GN pathogen during ICU stay. Microbiological assessment of available Pseudomonas aeruginosa isolates included minimum inhibitory concentrations for key antimicrobial agents.

RESULTS

Four hundred and seventy-two patients, primarily from the community (346, 73.3%), were treated in medical ICUs (272, 57.6%). Clinically defined pneumonia was common (264, 55.9%). Six hundred and nineteen GN organisms were identified from index respiratory cultures: P. aeruginosa was common (224, 36.2%), with 21.6% of these isolates being multidrug resistant. Cefepime (213, 45.1%) and piperacillin/tazobactam (174, 36.8%) were the most frequent empiric GN therapies. Empiric GN therapy was inappropriate in 44.6% of cases. Lack of in vitro susceptibility (80.1%) was the most common reason for inappropriateness. Patients with inappropriate empiric GN therapy had longer overall stay, which translated to a median total cost of care of $79,800 (interquartile range $48,775 to $129,600) versus $68,000 (interquartile range $38,400 to $116,175), p = 0.013. Clinical failure (31.5% vs 30.0%, p = 0.912) and in-hospital all-cause mortality (26.4% vs 25.9%, p = 0.814) were not different.

CONCLUSION

Drug-resistant pathogens were frequently found and empiric GN therapy was inappropriate in nearly 50% of cases. Inappropriate therapy led to increased lengths of stay and was associated with higher costs of care.

Antibacterial effect evaluation of moxalactam against extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae with in vitro pharmacokinetics/pharmacodynamics simulation

Objectives

The aim of this study was to evaluate the bactericidal effects of moxalactam (MOX), cefotaxime (CTX), and cefoperazone/sulbactam (CFZ/SBT) against extended-spectrum β-lactamase (ESBL) producing Escherichia coli and Klebsiella pneumoniae, using an in vitro pharmacokinetics (PK)/pharmacodynamics model.

Methods

Two clinical ESBL-producing strains (bla_CTX-M-15 positive E. coli 3376 and bla_CTX-M-14 positive K. pneumoniae 2689) and E. coli American Type Culture Collection (ATCC)25922 were used in the study. The PK Auto Simulation System 400 was used to simulate the human PK procedures after intravenous administration of different doses of MOX, CTX, and CFZ/SBT. Bacterial growth recovery time (RT) and the area between the control growth curve and bactericidal curves (IE) were employed to assess the antibacterial efficacies of all the agents.

Results

The minimum inhibitory concentrations of MOX, CTX, and CFZ/SBT against E. coli ATCC25922, 3376, and 2689 strains were 0.5, 0.5, 0.25; 0.06, >256, 256; and 0.5/0.5, 16/16, 32/32 mg/L. All the agents demonstrated outstanding bactericidal effects against E. coli ATCC25922 (RT >24 h and IE >120 log₁₀ CFU/mL·h⁻¹) with simulating PK procedures, especially in the multiple dose administration models. Against ESBL producers, CTX and CFZ/SBT displayed only weak bactericidal effects, and subsequent regrowth was evident. MOX exhibited potent antibacterial activity against all the strains tested. The values of effective parameters of MOX were much higher than those of CTX and CFZ/SBT (the bacterial RTs with the 3 agents were >24, <4, and <13 h, and the IEs were >110, <10, and <60 log₁₀ CFU/mL·h⁻¹, respectively).

Conclusion

MOX demonstrated excellent bactericidal effect, which is worthy of further exploration to serve as an alternative therapeutic agent against ESBL-producing Enterobacteriaceae.

ST37 Klebsiella pneumoniae: development of carbapenem resistance in vivo during antimicrobial therapy in neonates

Aim: To investigate the mechanism leading to in vivo carbapenem resistance development in Klebsiella pneumoniae. Methods: Carbapenemase was detected using the modified carbapenem inactivation method. β-lactamases resistant genes were identified by PCR and sequencing. Clonal relatedness was evaluated by random amplified polymorphic DNA and multiple locus sequence typing. The relationship between sequence typing and resistant genes was analyzed by using the chi-squared test. Results: All ST37 carbapenem-resistant isolates were blaOXA-1 positive and all ST37 carbapenem-sensitive isolates were blaOXA-1 negative at Stage I. A significant relationship between carbapenem resistance and blaOXA-1 was observed. The blaOXA-1 -positive rate was significantly higher in ST37 K. pneumoniae than others. Conclusion: This is the first study about the development of carbapenem resistance in vivo potentially mediated by blaOXA-1 in ST37 K. pneumoniae among neonates.

Laboratory investigation of a suspected outbreak caused by Providencia stuartii with intermediate resistance to imipenem at a long-term care facility

BACKGROUND

Providencia stuartii survives well in natural environment and often causes opportunistic infection in residents of long-term care facilities (LTCFs). Clinical isolates of P. stuartii are usually resistant to multiple antibiotics. The bacterium is also naturally resistant to colistin and tigecycline. Treatment of infections caused by carbapenem-resistant P. stuartii is challenging.

METHODS

During a 15-month period in 2013-2014, four isolates (P1, P2, and P3B/P3U) of P. stuartii showing intermediate resistance to imipenem were identified at a regional hospital in southern Taiwan. They were identified from three patients (P1-P3) transferred from the same LTCF for the treatment of the infection. Pulsed-field gel electrophoresis was used to genotype the isolates. Resistance genes/plasmids and outer membrane proteins were investigated by polymerase chain reaction and sequence analysis.

RESULTS

Isolates P1 and P3B/P3U demonstrated similar pulsotypes. All isolates were found to have resistance genes (bla_CMY-2, qnrD1, aac(6')-Ib-cr) carried on nonconjugative IncA/C plasmids of different sizes. A single point mutation was identified in the chromosomal gyrA (Ser83Ile) and parC (Ser84Ile) genes of all isolates. Various point mutations and insertion/deletion changes were found in their major outer membrane protein gene ompPst1.

CONCLUSIONS

Isolates of similar pulsotypes could appear after 15 months and caused urosepsis in another resident of the same LTCF. The bacterium may have persisted in the environment and caused opportunistic infection. As LTCF residents are usually vulnerable to infections, surveillance of multidrug-resistant organisms and infection control intervention that have been established in acute-care hospitals to control infections by resistant organisms are apparently as essential in LTCFs.

Outbreak of KPC-3 Producing Carbapenem-Resistant Klebsiella pneumoniae in a US Pediatric Hospital

BACKGROUND

The increase in carbapenem-resistant Enterobacteriaceae (CRE) infections is a critical public health issue. We recently experienced the largest single-center pediatric outbreak of carbapenem-resistant Klebsiella pneumoniae (CRKP) at our hospital. The objective of this study was to describe the molecular epidemiology of this outbreak before and after infection-prevention interventions.

METHODS

All positive cultures and associated clinical conditions were reviewed to determine whether health care-associated infections (HAIs) exist. HAIs were defined using Centers for Disease Control and Prevention guidelines. CRKP isolates were collected and screened for the presence of β-lactamase genes. Strain relatedness of CRKP isolates was determined by field-inversion gel electrophoresis (FIGE) and multilocus sequence typing (MLST). Polymerase chain reaction (PCR) amplification and sequencing of blaTEM, blaSHV, and blaKPC genes were performed on representative isolates.

RESULTS

During March-July 2010, 18 CRKP isolates were recovered from 15 unique patients. Six isolates were considered HAIs; all were central-line-associated bloodstream infections. All isolates testing positive by PCR for blaKPC were found to carry KPC-3 in transposon Tn4401 isotype "b." FIGE revealed 2 prevalent patterns (accounting for 10 and 3 CRKP isolates, respectively) that MLST demonstrated to consist entirely of strains from ST730; the remaining FIGE types corresponded to ST14, ST15, and ST1559 (a single-locus variant of ST730), with these alternate backgrounds appearing later in the outbreak. New CRKP cases decreased after the implementation of infection-control interventions. All isolates were ciprofloxacin sensitive.

CONCLUSIONS

Molecular analyses document the introduction of a KPC-3-producing CRKP clone into our hospital setting, though some isolates appear to have other mechanisms of carbapenem resistance. The transition to a polyclonal epidemiology suggests that the initial outbreak was due to nosocomial spread of a single ST730 clone, while latter isolates may have been secondary to the introduction of a blaKPC-3/Tn4401 isotype "b"-containing plasmid into other K pneumoniae strain backgrounds versus new carbapenemase-producing bacteria.

Risk factors for acquisition of carbapenem resistant Enterobacteriaceae in an acute tertiary care hospital in Singapore

Background

Carbapenem resistant Enterobacteriaceae (CRE) is increasingly reported worldwide. A similar increase is seen in Singapore since identification of its first case in 2008. The aim of this study was to identify local risk factors for carriage of CRE in patients from an acute tertiary care hospital in Singapore.

Method

A matched case-control study was conducted on inpatients treated from January 1, 2011 till December 31, 2013. Two hundred and three cases of CRE infection or colonization were matched with 203 controls. CRE types were identified by PCR. Statistical analysis of data including a multivariate logistic regression analysis was done using SPSS 21.0.

Results

CREs were commonly seen in Klebsiella pneumoniae (42.2 %), Escherichia coli (24.3 %) and Enterobacter cloacae complex (17.2 %) in the 268 isolates. NDM-1 was the commonest CRE type seen (44.4 %), followed by KPC (39.9 %) whilst OXA-48 only constituted (7.8 %). Univariate analysis identified key risk factors associated with CRE as history of previous overseas hospitalization (OR: 33.667; 95 % CI: 4.539-259.700), admission to ICU (OR: 11.899; 95 % CI: 4.986-28.399) and HD/ICA (OR: 6.557; 95 % CI: 4.057-10.596); whilst a multivariate analysis revealed exposure to antibiotics penicillin (OR: 4.640; 95 % CI: 1.529-14.079] and glycopeptide (OR: 5.162; 95 % CI: 1.377-19.346) and presence of central line device (OR: 3.117; 95 % CI: 1.167-8.330) as significant independent predictors.

Conclusions

The identification of risk factors amongst our local population helped to refine the criteria used for target active surveillance screening for CRE amongst inpatients at time of hospital admission.

In Vitro Activity of Imipenem and Colistin against a Carbapenem-Resistant Klebsiella pneumoniae Isolate Coproducing SHV-31, CMY-2, and DHA-1

We investigated the synergism of colistin and imipenem against a multidrug-resistant K. pneumoniae isolate which was recovered from a severe hip infection. PCR and DNA sequencing were used to characterize the outer membrane porin genes and the resistance genes mediating the common β-lactamases and carbapenemases. Synergism was evaluated by time-kill studies. The bla_SHV-31, bla_CMY-2, and bla_DHA-1 were detected. Outer membrane porin genes analysis revealed loss of ompK36 and frame-shift mutation of ompK35. The common carbapenemase genes were not found. Time-kill studies demonstrated that a combination of 1x MIC of colistin (2 mg/L) and 1x MIC of imipenem (8 mg/L) was synergistic and bactericidal but with inoculum effect. Bactericidal activity without inoculum effect was observed by concentration of 2x MIC of colistin alone or plus 2x MIC of imipenem. In conclusion, colistin plus imipenem could be an alternative option to treat carbapenem-resistant K. pneumoniae infections.

Multi-drug carbapenem-resistant Klebsiella pneumoniae infection carrying the OXA-48 gene and showing variations in outer membrane protein 36 causing an outbreak in a tertiary care hospital in Riyadh, Saudi Arabia

OBJECTIVES

To investigate the genes of antibiotic resistance among isolates from the first reported carbapenem-resistant Klebsiella pneumoniae (CRKP) outbreak in a tertiary care hospital, Riyadh, Saudi Arabia.

METHODS

Antimicrobial susceptibility testing was performed on bacterial isolates using the Microscan Walkaway system (Siemens, Germany) and was confirmed by Etest (AB Biodisk, Sweden). bla-CTX-M, -SHV, -TEM, -OXA-48, OXA-A,B,C,D, -KPC, -NDM, -VIM, -IMP, integron 1, and outer membrane proteins(Omp)-35 and Omp-36 were investigated by PCR amplification and direct sequencing of PCR products. Isolates were sequence-typed by multilocus sequence typing (MLST).

RESULTS

All isolates were resistant to cefotaxime, ceftazidime, cefepime, ciprofloxacin, and piperacillin-tazobactam, and 91% (21 out of 23) were resistant to amikacin and gentamicin. All isolates except two from a single patient were resistant to one of the carbapenems. CTX-M and SHV genes were detected in all isolates, CTX-M-15 and SHV-1 types being predominant among these extended-spectrum beta-lactamases (ESBLs). TEM-1 was found in all except one isolate (isolate 3). Significantly, the OXA-48 gene was also found in all isolates. OXA-D-gene was found in three out of 23 isolates. KPC, NDM, OXA-A, -B, -C, VIM, and IMP genes were absent in all isolates. Disruption of the Omp-36 gene due to insertion of transposon IS903 and/or IS4 was detected in four out of 23 isolates, and some unique variations were also observed in this gene, including an insertion of two amino acids in the L3 region of Omp-36 in one isolate (isolate 3) and a mutation resulting in a premature stop codon in another isolate (isolate 25). MLST revealed ST29 to be the predominant sequence type (17 out of 23 isolates, 74%). Three were ST709 and one each was ST37 and ST111; one isolate had an unknown ST.

CONCLUSIONS

This is probably the first reported outbreak of multidrug/carbapenem-resistant Klebsiella infection involving the OXA-48 gene from Saudi Arabia. Although the presence of ESBLs such as OXA, CTX-M, TEM, and SHV are predictable reasons for resistance, variations in the Omp-36 gene might also have precipitated this phenomenon. Disruption of the Omp-36 sequence by large insertional elements, the insertion of two amino acids in a very crucial part of this protein, and the presence of a premature stop codon in one isolate might have rendered this protein incomplete and non-functional. The study also demonstrated that more than one type of clone was responsible for this reported apparent outbreak and that ST29, a clone not reported from this region before, was the major clone responsible.

French regional surveillance program of carbapenemase-producing Gram-negative bacilli: results from a 2-year period

In February 2011, the CARB-LR group was created as a sentinel laboratory-based surveillance network to control the emergence of carbapenem-resistant Gram-negative bacilli (CR GNB) in a French Southern Region. We report the epidemiological results of a 2-year study. All the Gram-negative bacilli isolates detected in the different labs (hospital and community settings) of a French Southern Region and with reduced susceptibility to ertapenem and/or imipenem were characterised with regard to antibiotic resistance, bla genes content, repetitive sequence-based polymerase chain reaction (rep-PCR) profiles and multilocus sequence typing (MLST). A total of 221 strains were analysed. Acinetobacter baumannii was the most prevalent carbapenemase-producing bacteria, with a majority of OXA-23 producers (n = 37). One isolate co-produced OXA-23 and OXA-58 enzymes. Klebsiella pneumoniae was the most frequent carbapenemase-producing Enterobacteriaceae (CPE) (OXA-48 producer: n = 29, KPC producer: n = 1), followed by Escherichia coli (OXA-48 producer: n = 8, KPC producer: n = 1) and Enterobacter cloacae (OXA-48 producer, n = 1). One isolate of Pseudomonas aeruginosa produced a VIM-1 carbapenemase. A clonal diversity of carbapenemase-producing K. pneumoniae and E. coli was noted with different MLSTs. On the other hand, almost all OXA-23-producing A. baumannii strains belonged to the widespread ST2/international clone II. The link between the detection of CR GNB and a foreign country was less obvious, suggesting the beginning of a local cross-transmission. The number of CR GNB cases in our French Southern Region has sharply increased very recently due to the diffusion of OXA-48 producers.

Phenotypic and molecular characterization of multidrug resistant Klebsiella pneumoniae isolated from a university teaching hospital, China

The multidrug-resistant rate of Klebsiella pneumoniae has risen rapidly worldwide. To better understand the multidrug resistance situation and molecular characterization of Klebsiella pneumoniae, a total of 153 Klebsiella pneumoniae isolates were collected, and drug susceptibility test was performed to detect its susceptibility patterns to 13 kinds of antibiotics. Phenotypic tests for carbapenemases ESBLs and AmpC enzyme-producing strains were performed to detect the resistance phenotype of the isolates. Then PCR amplification and sequencing analysis were performed for the drug resistance determinants. The results showed that 63 strains harbored bla_CTX-M gene, and 14 strains harbored bla_DHA gene. Moreover, there were 5 strains carrying bla_KPC gene, among which 4 strains carried bla_CTX-M, bla_DHA and bla_KPC genes, and these 4 strains were also resistant to imipenem. Our data indicated that drug-resistant Klebsiella pneumoniae were highly prevalent in the hospital. Thus it is warranted that surveillance of epidemiology of those resistant isolates should be a cause for concern, and appropriate drugs should be chosen.

The high incidence of carbapenem-resistant Klebsiella pneumoniae in urine from elderly hospital patients may facilitate the spread of resistant strains to the community

Almost all European countries are affected by the expansion of carbapenem-resistant Enterobacteriaceae occurring during recent years. In the two hospitals of Verona, Italy, the incidence of carbapenem-nonsusceptible Klebsiella pneumoniae (CNSKP) began to increase by the first months of 2011, reached a peak in the summer of the same year, and currently is around 30%. Contrary to what was reported by other hospitals and although significant percentages of CNSKP were detected in respiratory samples, blood and pus, urine from hospitalized patients, mainly geriatrics, are the clinical samples with the highest incidence of these strains. Elder patients are frequently transferred from the hospital to their own homes or long-term care facilities and vice-versa. Moreover, urinary tract infections are not considered as a severe pathology and frequently is asymptomatic in elderly. For these reasons, the presence of carbapenem non-susceptible bacteria in the urinary tract of geriatric patients might be an underestimated cause of multiresistant strain spreading to the non-hospitalized population and the community.

Surveillance and management of multidrug-resistant microorganisms

Multidrug-resistant organisms are an established and growing worldwide public health problem and few therapeutic options remain available. The traditional antimicrobials (glycopeptides) for multidrug-resistant Gram-positive infections are declining in efficacy. New drugs that are presently available are linezolid, daptomicin and tigecycline, which have well-defined indications for severe infections, and talavancin, which is under Phase III trial for hospital-acquired pneumonia. Unfortunately the therapies available for multidrug-resistant Gram-negatives, including carbapenem-resistant Pseudomonas aeruginosa, Acinetobacter baumannii and Enterobacteriaceae, are limited to only colistin and tigecycline. Both of these drugs are still not registered for severe infections, such as hospital acquired pneumonia. Consequently, as confirmed by scientific evidence, a multidisciplinary approach is needed. Surveillance, infection control procedures, isolation and antimicrobial stewardship should be implemented to reduce multidrug-resistant organism diffusion.

Molecular surveillance and clinical outcomes of carbapenem-resistant Escherichia coli and Klebsiella pneumoniae infections

BACKGROUND/PURPOSE

The emergence of carbapenem-resistant Enterobacteriaceae (CRE) is a cause for great concern. The aim of this study was to evaluate antimicrobial susceptibility, mechanisms of carbapenem-resistance in two members of the Enterobacteriaceae family (Escherichia coli and Klebsiella pneumoniae), and clinical outcomes of their infections.

METHODS

The susceptibility tests of 16 E. coli and 60 K. pneumoniae isolates, collected from 2010 to 2011, were assessed. The minimal inhibitory concentrations of eight antimicrobial agents were assessed by the broth microdilution method according to the recommendations of the Clinical and Laboratory Standards Institute. The detection of beta-lactamase genes was performed by polymerase chain reaction. The genetic relatedness of these isolates was determined by pulsed-field gel electrophoresis (PFGE) fingerprinting.

RESULTS

The carbapenemase genes blaKPC-2 and blaOxA were detected in one and five K. pneumoniae isolates, respectively. The genetic combinations blaSHV-5-blaDHA and blaSHV-5-blaCTx-M-G9 were prevalent in 45% and 26.7% of 60 K. pneumoniae isolates, respectively. The susceptibility rates of 60 K. pneumoniae isolates to colistin and tigecycline were 58.3% and 50.0%, respectively. The 30-day mortality rates of the patients treated with carbapenem, colistin, or tigecycline were as high as 60.6%. Nine clusters of K. pneumoniae isolates were identified by PFGE fingerprinting.

CONCLUSION

The findings of carbapenemase genes in a few isolates and small clusters of CRE indicated the emerging problems in the hospital. The high mortality rates were observed in the patients treated by colistin and tigecycline, although they were the only alternative treatment options for CRE infections. Active surveillance and an effective infection control strategy should be implemented to control the spread of CRE infections.

Overview of the epidemiology and the threat of Klebsiella pneumoniae carbapenemases (KPC) resistance

Klebsiella pneumoniae carbapenemases (KPCs) confer resistance to nearly all β-lactams. This broad-spectrum drug resistance mechanism has rapidly spread in the United States and is reportedly increasing elsewhere in the world. Thus, the emergence of KPC resistance is a major threat to global health. This article reviews the epidemiology and provides an overview of the dissemination of KPC-producing organisms.

Molecular typing and resistance mechanisms of imipenem-non-susceptible Klebsiella pneumoniae in Taiwan: results from the Taiwan surveillance of antibiotic resistance (TSAR) study, 2002-2009

We investigated the molecular mechanisms and clonality of imipenem-non-susceptible Klebsiella pneumoniae isolates collected during a Taiwan national surveillance programme, between 2002 and 2009. Genes for carbapenemases, plasmid-borne ampC-type genes and extended-spectrum β-lactamase (ESBL) genes were analysed by PCR. The major porin channels OmpK35 and OmpK36 were studied by SDS-PAGE. Molecular typing was performed with pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). Our study revealed that all 29 of the isolates tested were ESBL producers. Of the K. pneumoniae isolates collected in Taiwan from 2002 to 2009, most (84.6 %, 11/13) imipenem-resistant (MIC >2 mg l(-1)) isolates carried the bla(IMP-8) gene. Isolates with an imipenem MIC of 2 mg l(-1) produced ESBLs with or without DHA-1 in combination with OmpK35/36 loss. PFGE analysis revealed that six small clusters of isolates were clonally related. The MLST grouping results were in concordance with the PFGE results. The predominant sequence types (ST) were ST11, ST48 and ST101. Two novel STs, ST1033 and ST1034, were found. The dominant clone in Taiwan, ST11, has been reported worldwide to be associated with various resistance mechanisms.

Interplay between mutational and horizontally acquired resistance mechanisms and its association with carbapenem resistance amongst extensively drug-resistant Pseudomonas aeruginosa (XDR-PA)

Between 2003 and 2009, the prevalence of extensively drug-resistant Pseudomonas aeruginosa (XDR-PA) increased significantly in northern Taiwan from 1.0% to 2.1%. Molecular methods were used to investigate the genetic relatedness and carbapenem resistance mechanisms of a collection of 203 non-repetitive XDR-PA isolates available for study. Using pulsed-field gel electrophoresis (PFGE), 52 genotypes were observed; one predominant genotype (pulsotype 1) was found in 57.6% of the isolates. Polymerase chain reaction (PCR), sequencing and quantitative reverse-transcriptase PCR analyses demonstrated that one horizontally acquired mechanism [metallo-β-lactamase (MBL) genes] and two mutational mechanisms (efflux and porins) accounted for the carbapenem resistance. The most predominant horizontally acquired mechanism was carriage of bla_VIM-3, which was found in 61.1% of isolates. Decreased expression of oprD was the most prevalent mutational mechanism and was found in 70.0% of the XDR-PA isolates, whereas overexpression of mexA was found in 27.6% of the isolates. The highlight of this study was the discovery of statistically significant relationships between certain horizontally acquired and mutational resistance mechanisms and their contribution to carbapenem susceptibility. MBL-producers expressed significantly lower MexAB and higher OprD than non-MBL-producers. Amongst isolates without an acquired β-lactamase gene, oprD expression was significantly reduced, whilst expression of efflux pumps was increased. Reduced OprD expression alone or the production of VIM-type MBLs showed similar contributions to a low to intermediate MIC₅₀ (minimum inhibitory concentration for 50% of the organisms) for carbapenems. Isolates with reduced OprD expression that simultaneously harboured bla_VIM exhibited high levels of resistance to carbapenems, which implied that these two mechanisms had a synergistic effect on the MICs.

Spread of ISCR1 elements containing blaDHA-₁ and multiple antimicrobial resistance genes leading to increase of flomoxef resistance in extended-spectrum-beta-lactamase-producing Klebsiella pneumoniae

Increasing resistance to quinolones, aminoglycosides, and/or cephamycins in extended-spectrum-β-lactamase (ESBL)-producing Enterobacteriaceae exacerbates the already limited antibiotic treatment options for infections due to these microbes. In this study, the presence of resistance determinants for these antimicrobial agents was examined by PCR among ESBL-producing Klebsiella pneumoniae (ESBL-KP) isolates that caused bacteremia. Pulsed-field gel electrophoresis was used to differentiate the clonal relationship among the isolates studied. Transferability and the location of the resistance genes were analyzed by conjugation experiments, followed by DNA-DNA hybridization. Among the 94 ESBL-KP isolates studied, 20 isolates of flomoxef-resistant ESBL-KP were identified. They all carried a DHA-1 gene and were genetically diverse. CTX-M genes were found in 18 of the isolates. Among these DHA-1/CTX-M-producing K. pneumoniae isolates, ISCR1 was detected in 13 (72%) isolates, qnr genes (1 qnrA and 17 qnrB genes) were detected in 18 (100%), aac(6')-Ib-cr was detected in 11 (61%), and 16S rRNA methylase (all armA genes) was detected in 14 (78%). Four transconjugants were available for further analysis, and qnrB4, aac(6')-Ib-cr, armA, and bla(DHA-1) were all identified on these self-transferable bla(CTX-M)-carrying plasmids. The genetic environments of ISCR1 associated with armA, bla(DHA-1), and qnrB4 genes in the four transconjugants were identical. Replicon-type analysis revealed a FIIA plasmid among the four self-transferable plasmids, although the other three were nontypeable. The cotransfer of multiple resistance genes with the ISCR1 element-carrying plasmids has a clinical impact and warrants close monitoring and further study.