Evolution and dissemination of extended-spectrum β-lactamase-producing Klebsiella pneumoniae: Epidemiology and molecular report from the SENTRY Antimicrobial Surveillance Program (1997–2003)

Organic Extract of Justicia pectoralis Jacq. Leaf Inhibits Interferon-γ Secretion and Has Bacteriostatic Activity against Acinetobacter baumannii and Klebsiella pneumoniae

Justicia pectoralis Jacq. (Acanthaceae) leaves currently found in the Brazilian north-east are widely used to treat diabetes, menstrual pains, asthma, and other disorders. This work aimed to identify the phytochemical characterization and biological activities of J. pectoralis leaf extracts. The plant material was ground and the crude extracts were obtained with water or acetone: water (7:3 v/v), yielding aqueous (JPA), and organic (JPO) extracts. Phytochemical characterization was performed by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). Cytotoxicity was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay and trypan blue (TB) exclusion assay in peripheral blood mononuclear cells (PBMCs), BALB/c splenocytes, and neoplastic cells (TOLEDO, K562, DU-145, and PANC-1) at 1, 10, and 100 μg/mL. Antibacterial activity was evaluated using the microdilution test to obtain the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Cytokines, IFN-γ, and IL-17A from culture supernatants of BALB/c mice splenocytes were measured by sandwich ELISA. In the TLC analysis, both JPA and JPO extracts presented coumarin and flavonoids. In addition, HPLC was able to identify coumarin, apigenin, and ellagic acid in both extracts. JPO IC₅₀ was 57.59 ± 1.03 μg/mL (MTT) and 69.44 ± 8.08 μg/mL (TB) in TOLEDO. MIC value of JPO against Acinetobacter baumannii and Klebsiella pneumoniae was 500 μg/mL. JPO (100 μg/mL) significantly inhibited IFN-γ levels (p=0.03). J. pectoralis is a potential candidate to be further investigated as an IFN-γ inhibitory agent and against Acinetobacter baumannii and Klebsiella pneumoniae.

First Report of SHV-148-Type ESBL and CMY-42-Type AmpC β-Lactamase in Klebsiella pneumoniae Clinical Isolates in Tunisia

Extended-spectrum beta-lactamase producing Enterobacteriaceae present a real problem worldwide. We aimed to investigate the molecular mechanisms of resistance to antibiotics among Klebsiella pneumoniae clinical isolates collected from a Hospital in the southeast of Tunisia. Eighteen cephalosporin-resistant K. pneumoniae were recovered between April 2015 and August 2016. Molecular characterization of antimicrobial resistance encoding genes was performed by PCR and sequencing. Results revealed several types of Ambler class A β-lactamase encoding genes among our isolates: [blaCTXM-15 (15), blaSHV-28 (6), blaSHV-1 (2), blaSHV-148 (1), blaSHV-61 (1), blaSHV-76 (1), blaSHV-186 (1), blaTEM-1 (8)]. The association of blaOXA-1 was observed in nine isolates. However, the class C β-lactamase encoding genes were detected in four isolates [blaCMY-4 (2), blaCMY-42 (1), blaACT-35 (1)]. Molecular typing of K. pneumoniae isolates by pulsed-field gel electrophoresis showed 16 unrelated pulsotypes proving a high diversity among our isolates. Our study provides new epidemiological information showing a huge diversity of β-lactamase encoding genes among our isolates. In fact, this is the first report of SHV-76, SHV-148, and SHV-186 in Tunisia. This is also the first report of CMY-42 and ACT-35 producing K. pneumoniae in our country.

Peptide nucleic acids (PNAs): currently potential bactericidal agents

In recent years, the emergence of ESBL-producing and multi-drug resistant bacteria have been increased and designing novel components is necessary for confrontation these bacteria. Peptide nucleic acids (PNAs) are one of the synthetic components that bind to single strand DNA and RNA. Applications of these components are wide while, and one of the important applications of these components is inhibition of gene expression and knock downing the target gene follow as inhibition of bacterial growth. For PNA targeting gene, peptide-PNAs (PPNA) activity cannot be occurred without sequence homology, at the same time, it has been affected by sequence-based specific target and dose-dependent-based manner. Choosing the conserved sequence in different bacterial genus can provide broad-spectrum antimicrobial activity. In this review article, we studied several research papers and extract PNA targeting genes that cause gene knock down and inhibition of bacterial growth. Some novel opportunities for advancement and the design ultra-narrow-spectrum antimicrobial drugs against multi-drug can be accessible by utilizing PNA against necessary genes of pathogens. These results open novel vision for therapeutic intervention. Future researches are required to evaluate the safety, toxicity and pharmacokinetics properties of PPNAs in order to be utilized in clinical treatment.

Ozonation and UV254nm radiation for the removal of microorganisms and antibiotic resistance genes from urban wastewater

Conventional wastewater treatment has a limited capacity to reduce antibiotic resistant bacteria and genes (ARB&ARG). Tertiary treatment processes are promising solutions, although the transitory inactivation of bacteria may select ARB&ARG. This study aimed at assessing the potential of ozonation and UV_254nm radiation to inactivate cultivable fungal and bacterial populations, and the selected genes 16S rRNA (common to all bacteria), intI1 (common in Gram-negative bacteria) and the ARG vanA, bla_TEM, sul1 and qnrS. The abundance of the different microbiological parameters per volume of wastewater was reduced by ∼2 log units for cultivable fungi and 16S rRNA and intI1 genes, by∼3-4 log units, for total heterotrophs, enterobacteria and enterococci, and to values close or below the limits of quantification for ARG, for both processes, after a contact time of 30min. Yet, most of the cultivable populations, the 16S rRNA and intI1 genes as well as the ARG, except qnrS after ozonation, reached pre-treatment levels after 3days storage, suggesting a transitory rather than permanent microbial inactivation. Noticeably, normalization per 16S rRNA gene evidenced an increase of the ARG and intI1 prevalence, mainly after UV_254nm treatment. The results suggest that these tertiary treatments may be selecting for ARB&ARG populations.

Instant Typing Is Essential to Detect Transmission of Extended-Spectrum Beta-Lactamase-Producing Klebsiella Species

BACKGROUND

Infections with multidrug-resistant (MDR) microorganisms are an increasing threat to hospitalized patients. Although rapid typing of MDR microorganisms is required to apply targeted prevention measures, technical barriers often prevent this. We aimed to assess whether extended-spectrum beta-lactamase (ESBL)-producing Klebsiella species are transmitted between patients and whether routine, rapid typing is needed.

METHODS

For 43 months, the clonality of all ESBL-producing Klebsiella isolates from patients admitted to Erasmus MC University Medical Center in Rotterdam, the Netherlands was assessed with Raman spectroscopy. A cluster was defined as n ≥ 2 patients who had identical isolates. Primary patients were the first patients in each cluster. Secondary patients were those identified with an isolate clonally related to the isolate of the primary patient.

RESULTS

Isolates from 132 patients were analyzed. We identified 17 clusters, with 17 primary and 56 secondary patients. Fifty-nine patients had a unique isolate. Patients (n = 15) in four out of the 17 clusters were epidemiologically related. Ten of these 15 patients developed an infection.

CONCLUSIONS

Clonal outbreaks of ESBL-producing Klebsiella species were detected in our hospital. Theoretically, after Raman spectroscopy had detected a cluster of n ≥ 2, six infections in secondary patients could have been prevented. These findings demonstrate that spread of ESBL-producing Klebsiella species occurs, even in a non-outbreak setting, and underscore the need for routine rapid typing of these MDR bacteria.

Genetic characterization of fluoroquinolone resistant Escherichia coli from urban streams and municipal and hospital effluents

Escherichia coli with reduced susceptibility to ciprofloxacin, isolated from urban streams, wastewater treatment plants and hospital effluent between 2004 and 2012, were compared based on multilocus sequence typing (MLST), quinolone and beta-lactam resistance determinants and plasmid replicon type. Isolates from the different types of water and isolation dates clustered together, suggesting the persistence and capacity to propagate across distinct aquatic environments. The most prevalent MLST groups were ST10 complex and ST131. Almost all isolates (98%) carried mutations in the chromosomal genes gyrA and/or parC, and 10% possessed the genes qepA, aac(6('))-Ib-cr and/or qnrS1. Over 80% of the isolates were resistant to three or more classes of antibiotics (MDR ≥ 3). The most prevalent beta-lactamase encoding gene was blaTEM, followed by blaCTX-M-15, co-existing with plasmid mediated quinolone resistance. The plasmid replicon types of the group IncF were the most prevalent and distributed by different MLST groups. The genes aac(6('))-Ib-cr and/or qnrS1 could be transferred by conjugation in combination with the genes blaTEM,blaSHV-12 or blaOXA-1 and the plasmid replicon types I1-Iγ, K, HI2 and/or B/O. The potential of multidrug resistant E. coli with reduced susceptibility to ciprofloxacin, harboring mobile genetic elements and with ability to conjugate and transfer resistance genes, to spread and persist across different aquatic environments was demonstrated.

[Prevalence and risk factors of multi-drug resistant organism colonization among long-term care facilities in Gran Canaria (Spain)]

INTRODUCTION

Multidrug resistant organisms (MDRO) are an important cause of nosocomial infections, with complicated clinical-therapeutic management and elevated morbidity-mortality, and an increase in healthcare costs. In long term care facilities (LTCFs) colonization/infection by MDRO among residents is increasing, and they may act as reservoirs and vehicles for the dissemination and production of outbreaks by resistant strains in acute hospitals. This study aimed at determining the prevalence of carriers of some common MDRO, and identifying factors associated with carrier state.

MATERIAL AND METHODS

A cross-sectional prevalence study was conducted on 235 residents in two LTCFs in the province of Las Palmas de Gran Canaria (Canary Islands, Spain) between October and November of 2012. The presence of MMR was investigated in nasal, pharyngeal and rectal swabs using selective media. Risk factors associated with carrier state were calculated using univariate and multivariate analysis.

RESULTS

More than one-third (36.2%) of residents were found to be carriers of ≥ 1 distinct MDROs. More than one-quarter (26.6%) were carriers of ESBL producing Enterobacteriaceae, and 10.2% were MRSA carriers. Factors found to be associated with colonization by any MDRO were: prior colonization or infection by MDRO, hospitalization in the past 3 months, recurrent infections of the urinary tract, and peripheral arterial disease.

CONCLUSIONS

The prevalence of MDRO in the LTCFs settings studied is greater than that found in the literature, and in particular ESBL producing Enterobacteriaceae. Due to the high prevalence of infection/colonization by MDRO, it is possible that residents of LTCFs could act as important reservoirs of MDRO, and facilitate their spread into the acute care setting.

Study of a Natural Mutant SHV-Type β -Lactamase, SHV-104, from Klebsiella pneumoniae

Klebsiella pneumoniae ML2011, a multiresistant isolate, was isolated from the Military Hospital of Tunis (Tunisia). The determination of the minimal inhibitory concentrations exhibited by K. pneumoniae ML2011 was performed by Etest. The crude extract of the isolates contains four different β-lactamases with pI 5.5, 7.3, 7.6, and 8.6. Only the β-lactamases with pI 7.3 and pI 8.6 were transferred by transformation and conjugation experiment. Molecular characterization of these genes was performed by PCR and sequencing. The chromosomal β-lactamases are TEM (pI 5.5) and SHV-1 (7.6). CTX-M-28 (pI 8.6) and the novel variant of SHV named SHV-104 (pI 7.3) were encoded by bla gene located on a 50 kb highly conjugative plasmid. The SHV-104 β-lactamase was produced in E. coli and purified. Its profile of activity was determined. Compared to SHV-1, SHV-104 contains one mutation, R202S. Their kinetic parameters were similar except for cefotaxime. The analysis of the predicted structure of SHV-104 indicated that the R202S mutation suppresses a salt bridge present in SHV-1. Therefore, the overall flexibility of the protein increased and might improve the hydrolysis of cefotaxime. We can conclude that the multiresistant phenotype of K. pneumoniae ML2011 strain is mainly linked to the production of CTX-M-28 since SHV-104 possesses a narrow spectrum of activity.

Molecular characterization of integrons in clinical isolates of betalactamase-producing Escherichia coli and Klebsiella pneumoniae in Iran

Integrons are considered to play a significant role in the evolution and spread of antibiotic resistance genes. A total of 349 clinical isolates of Escherichia coli and Klebsiella pneumoniae were investigated for molecular characterization of integrons and betalactamases. Antimicrobial susceptibility testing was also performed as the Clinical and Laboratory Standards Institute (CLSI) guidelines. The frequency of extended spectrum betalactamases (ESBL) or metallo-betalactamases (MBL)-producing isolates, patient demographics, and the susceptibility to various antimicrobial agents were described. BlaCTX-M was the most frequently detected betalactamase in all isolates. Moreover, MBL producing K. pneumoniae carried blaIMP and blaVIM at 100 and 41·6%, respectively but no MBL-positive E. coli was detected. Class 1 integrons were more frequent among E. coli and K. pneumoniae isolates in comparison with class 2 integrons and the frequency of intI2 in K. pneumoniae was significantly higher than E. coli isolates. Five different resistance gene arrays were identified among class 1 integrons. Dihydrofolate reductase (dfrA) and aminoglycoside adenyltransferase (aad) gene cassettes were found to be predominant in the class 1 integrons. These results indicate that class 1 integrons are widespread among ESBL-producing isolates of K. pneumoniae and E. coli and appropriate surveillance and control measures are essential to prevent further dissemination of these elements among Enterobacteriaceae in our country.

A step towards the discrimination of beta-lactamase-producing clinical isolates of Enterobacteriaceae and Pseudomonas aeruginosa by MALDI-TOF mass spectrometry

Background

Matrix-Assisted Laser-Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS) has already proven to be a powerful tool for species identification in microbiological laboratories. As adequate and rapid screening methods for antibiotic resistance are crucially needed, the present study investigated the discrimination potential of MALDI-TOF MS among extended-spectrum-beta-lactamase (ESBL) or metallo-beta-lactamases- (MBL) producing and the nonproducing strains of Escherichia coli (n=19), Klebsiella pneumoniae (n=19), and Pseudomonas aeruginosa (n=38), respectively.

Material/Methods

We used a MALDI-TOF MS protocol, usually applied for species identification, in order to integrate a screening method for beta-lactamases into the routine species identification workflow. The acquired spectra were analyzed by visual inspection, statistical similarity analysis and support vector machine (SVM) classification algorithms.

Results

Neither visual inspection nor mathematical similarity analysis allowed discrimination between spectra of beta-lactamase-producing and the nonproducing strains, but classification within a species by SVM-based algorithms could achieve a correct classification rate of up to 70%.

Conclusions

This shows that MALDI-TOF MS has definite potential to discriminate antibiotic-resistant strains due to ESBL and MBL production from nonproducing strains, but this performance is not yet sufficiently reliable for routine microbiological diagnostics.

The burden of multidrug-resistant organisms on tertiary hospitals posed by patients with recent stays in long-term acute care facilities

BACKGROUND

Long-term acute care (LTAC) facilities admit patients with complex, advanced disease states. Study aims were to determine the burden posed on hospitals associated with LTAC exposure and analyze the differences between "present on admission" (POA) multidrug-resistant (MDR), gram-negative organisms (GNO) and POA MDR gram-positive organisms (GPO).

METHODS

A multicenter retrospective study was conducted in 13 hospitals from southeast Michigan, from September 1, 2008, to August 31, 2009. Cultures obtained in the first 72 hours of hospitalization (ie, POA) of MDR-GPO and MDR-GNO were reviewed. LTAC exposures in the previous 6 months and direct admission from a LTAC were recorded.

RESULTS

Overall, 5,297 patients with 7,147 MDR POA cultures were analyzed: 2,619 (36.6%) were MDR-GNO, and 4,528 (63.4%) were MDR-GPO. LTAC exposure in the past 6 months was present in 251 (5.2%) infectious episodes and was significantly more common among POA MDR-GNO than MDR-GPO (158 [8.6%] and 94 [3.1%], respectively, odds ratio, 2.87; P < .001). Recent LTAC exposure was strongly associated with both carbapenem-resistant Enterobacteriaceae (CRE) (31.6% of all CRE cases, P < .001) and Acinetobacter baumannii (14.9% of all A baumannii cases, P < .001).

CONCLUSION

Nearly 10% of MDR-GNO POA had recent LTAC exposure. Hospital efforts to control the spread of MDR-GNO should focus on collaborations and communications with referring LTACs and interventions targeted towards patients with recent LTAC exposure.

Diversity and antibiotic resistance of Aeromonas spp. in drinking and waste water treatment plants

The taxonomic diversity and antibiotic resistance phenotypes of aeromonads were examined in samples from drinking and waste water treatment plants (surface, ground and disinfected water in a drinking water treatment plant, and raw and treated waste water) and tap water. Bacteria identification and intra-species variation were determined based on the analysis of the 16S rRNA, gyrB and cpn60 gene sequences. Resistance phenotypes were determined using the disc diffusion method. Aeromonas veronii prevailed in raw surface water, Aeromonas hydrophyla in ozonated water, and Aeromonas media and Aeromonas puntacta in waste water. No aeromonads were detected in ground water, after the chlorination tank or in tap water. Resistance to ceftazidime or meropenem was detected in isolates from the drinking water treatment plant and waste water isolates were intrinsically resistant to nalidixic acid. Most of the times, quinolone resistance was associated with the gyrA mutation in serine 83. The gene qnrS, but not the genes qnrA, B, C, D or qepA, was detected in both surface and waste water isolates. The gene aac(6')-ib-cr was detected in different waste water strains isolated in the presence of ciprofloxacin. Both quinolone resistance genes were detected only in the species A. media. This is the first study tracking antimicrobial resistance in aeromonads in drinking, tap and waste water and the importance of these bacteria as vectors of resistance in aquatic environments is discussed.

VIM and IMP metallo-β-lactamases and other extended-spectrum β-lactamases in Escherichia coli and Klebsiella pneumoniae from environmental samples in a Tunisian hospital

An extremely drug-resistant Enterobacteriaceae species emerged in Kasserine Hospital, Tunisia between 2009 and 2010 causing a local outbreak. We aimed to characterize extended-spectrum β-lactamase (ESBL) and metallo-β-lactamase (MBL)-producing Enterobacteriaceae from the hospital environment. Swabs were collected from ten different wards from Kasserine Hospital, Tunisia. A total of 46 isolates were cultured onto MacConkey agar supplemented with ceftazidime to select for ESBL-producing Enterobacteriaceae. Identification and susceptibility patterns were performed using Phoenix-automated phenotypic identification criteria. Extended spectrum β-lactamases (ESBLs) were detected using cefepime ESBL E-test. Colony blotting was first used to detect the occurrence of bla(SHV) , bla(CTX-M) , bla(CMY) , bla(IMP) , and bla(VIM) genes. PCR was used to amplify these genes, and the amplicons were sequenced and analyzed. Total DNA was digested with XbaI, and PFGE was used to type the major isolates that produced IMP-1. Among the 46 isolates, 63% were Klebsiella pneumoniae, 13% were Escherichia coli, 8.7% were Proteus mirabilis, 6% were Enterobacter cloaceae, 4.3% were Providencia rettgeri, 2.5% were Serratia marcescens, and 2.5% were Pantoea agglomerans. PCR amplification and DNA sequencing showed that hospital environment isolates produced SHV-125, CTX-M-15, CMY-2 ESBLs, and IMP-1 and VIM-2 MBLs. PFGE typing showed the emergence of IMP-1 MBL-producing K. pneumoniae isolates that were not clonal. In this study, we report the first characterization of IMP-1 and VIM-2 MBL-producing K. pneumoniae and E. coli isolates collected from Kasserine Hospital, Tunisia.

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

OBJECTIVE

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSION

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

Studies on amino acid replacement and inhibitory activity of a beta-lactamase inhibitory peptide

An SHV beta-lactamase gene was amplified from a beta-lactam resistant Klebsiella pneumoniae K-71 genomic DNA. After expression and purification, we demonstrated that peptide P1 could inhibit the hydrolysis activity of both TEM-1 and SHV beta-lactamase in vitro. Three mutations were introduced into P1 in which the first residue S was replaced by F, the 18th residue V was mutated to Y, and the 15th residue Y was substituted with A, C, G, and R to obtain the mutants of P1-A, P1-C, P1-G, and P1-R, respectively. The mutant peptides were purified and their inhibitory constants against TEM-1 and SHV beta-lactamase were determined. All these beta-lactamase inhibitory peptides could inhibit the activity of both beta-lactamases, while the mutant peptides showed stronger inhibitory activities against TEM-1 beta-lactamase than against SHV beta-lactamase. Inhibition data suggested that P1-A improved the beta-lactamase inhibitory activity by over 3-fold compare to P1. When P1-A was incubated with K. pneumoniae K-71 in Luria-Bertani medium containing ampicillin, it showed a much stronger growth of inhibition ratio over P1. This study gives us a good candidate for development of novel beta-lactamase inhibitors.

Potential role of active surveillance in the control of a hospital-wide outbreak of carbapenem-resistant Klebsiella pneumoniae infection

BACKGROUND

The recent emergence of carbapenem resistance among Enterobacteriaceae is a major threat for hospitalized patients, and effective strategies are needed.

OBJECTIVE

To assess the effect of an intensified intervention, which included active surveillance, on the incidence of infection with carbapenem-resistant Klebsiella pneumoniae.

SETTING

Sheba Medical Center, a 1,600-bed tertiary care teaching hospital in Tel Hashomer, Israel.

DESIGN

Quasi-experimental study.

METHODS

The medical records of all the patients who acquired a carbapenem-resistant K. pneumoniae infection during 2006 were reviewed. An intensified intervention was initiated in May 2007. In addition to contact precautions, active surveillance was initiated in high-risk units. The incidence of clinical carbapenem-resistant K. pneumoniae infection over time was measured, and interrupted time-series analysis was performed.

RESULTS

The incidence of clinical carbapenem-resistant K. pneumoniae infection increased 6.42-fold from the first quarter of 2006 up to the initiation of the intervention. In 2006, of the 120 patients whose clinical microbiologic culture results were positive for carbapenem-resistant K. pneumoniae, 67 (56%) developed a nosocomial infection. During the intervention period, the rate of carbapenem-resistant K. pneumoniae rectal colonization was 9%. Of the 390 patients with carbapenem-resistant K. pneumoniae colonization or infection, 204 (52%) were identified by screening cultures. There were a total of 12,391 days of contact precautions, and of these, 4,713 (38%) were added as a result of active surveillance. After initiation of infection control measures, we observed a significant decrease in the incidence of carbapenem-resistant K. pneumoniae infection.

CONCLUSIONS

The use of active surveillance and contact precautions, as part of a multifactorial intervention, may be an effective strategy to decrease rates of nosocomial transmission of carbapenem-resistant K. pneumoniae colonization or infection.

The current state of multidrug-resistant gram-negative bacilli in North America

Although much of today's media focuses on multidrug-resistant gram-positive bacteria such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus, resistance within gram-negative bacilli continues to rise, occasionally creating situations in which few or no antibiotics that retain activity are available. Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella sp are emerging threats nationally. Although carbapenems are considered the antibiotic class of choice to treat ESBL-producing Enterobacteriaceae, the ability of these organisms to produce carbapenemases has now become apparent in some regions throughout the United States. Although still rare, Klebsiella sp that produce KPC-2 retain susceptibility only to tigecycline, polymyxins, and occasionally aminoglycosides. Multidrug resistance among Pseudomonas aeruginosa and Acinetobacter sp has always been apparent across many hospitals in the United States. Recent surveillance indicates increasing resistance to all currently available antibiotics, including carbapenems, cephalosporins, penicillins, fluoroquinolones, and aminoglycosides. Against many strains, only polymyxins retain activity; however, resistance has also been reported to these agents. Fortunately, resistance mechanisms such as metallo-beta-lactamases are still rare in the United States. As no new antibiotics with novel mechanisms against many of these gram-negative bacilli are expected to be developed in the foreseeable future, careful and conservative use of agents combined with good infection control practices is required.

Emergence of resistant Acinetobacter baumannii in critically ill patients within an acute care teaching hospital and a long-term acute care hospital

BACKGROUND

Acinetobacter baumannii is a gram-negative, coccobacillus found in water and is a significant nosocomial pathogen in hospitals. This report chronicles the appearance in June 2003 of a multidrug-resistant A baumannii (MDR-AB) strain, its dissemination, and interventions used to control it in an acute care hospital (ACH) and long-term acute care facility (LTAC).

METHODS

Molecular typing using pulsed-field gel electrophoresis (PFGE) showed that 88 of 99 strains (89%) gave an identical banding designated as clone A. Eight additional isolates were variants of clone A, and 3 isolates were unrelated.

RESULTS

A baumannii was isolated from 229 patients between January 2003 and December 2004. Of these patients, 151 (66%) were colonized/infected with MDR-AB. Most isolates were resistant to antibiotics except for imipenem and ampicillin/sulbactam. Isolates included 108 (72%) in the respiratory tract, 32 (21%) in wounds, 6 (4%) in blood, and 5 (3%) in urine. Most isolates were found in the LTAC (70 isolates), ICU step-down (27 isolates), and ICU (26 isolates).

CONCLUSION

This epidemiologic history illustrates (1) epidemic clonal spread, (2) target populations, (3) variable monthly prevalence, and (4) intervention outcomes. With intervention, the number of new isolates in the ACH decreased by dedicating an infection control professional to critical care, daily surveillance, isolation of positive MDR-AB patients, universal gloving, and routinely reporting results.

Prevalence and significance of a negative extended-spectrum beta-lactamase (ESBL) confirmation test result after a positive ESBL screening test result for isolates of Escherichia coli and Klebsiella pneumoniae: results from the SENTRY Asia-Pacific Surveillance Program

A negative extended-spectrum beta-lactamase (ESBL) confirmation test result obtained after a positive ESBL screening test result using Clinical and Laboratory Standards Institute methods has been a common occurrence among isolates of Escherichia coli and Klebsiella pneumoniae in the SENTRY Antimicrobial Surveillance Program in the Asia-Pacific region. Among isolates collected between 1998 and 2004 this screen-positive, nonconfirmed profile (failed to show clavulanate synergy) was observed in 8.9% of 4,515 E. coli isolates and 20.3% of 2,303 K. pneumoniae isolates. We then selected 52 E. coli isolates and 68 K. pneumoniae isolates with a negative ESBL confirmation test, as well as comparable number of isolates with confirmed ESBL-positive tests, and examined them for the presence of TEM, SHV, plasmid-borne ampC, and CTX-M genes. We found that 62% of nonconfirming E. coli isolates and 75% of nonconfirming K. pneumoniae harbored a plasmid-borne AmpC enzyme of the CIT or DHA type. The majority of nonconfirming E. coli and K. pneumoniae from the Asia-Pacific region harbor important beta-lactamases, and a positive screening test alone should be sufficient grounds to report resistance to extended-spectrum cephalosporins in this region.

Inhibition of gene expression and growth by antisense peptide nucleic acids in a multiresistant beta-lactamase-producing Klebsiella pneumoniae strain

Klebsiella pneumoniae causes common and severe hospital- and community-acquired infections with a high incidence of multidrug resistance. The emergence and spread of beta-lactamase-producing K. pneumoniae strains highlight the need to develop new therapeutic strategies. In this study, we developed antisense peptide nucleic acids (PNAs) conjugated to the (KFF)(3)K peptide and investigated whether they could mediate gene-specific antisense effects in K. pneumoniae. No outer membrane permeabilization was observed with antisense PNAs when used alone. Antisense peptide-PNAs targeted at two essential genes, gyrA and ompA, were found to be growth inhibitory at concentrations of 20 muM and 40 muM, respectively. Mismatched antisense peptide-PNAs with sequence variations of the gyrA and ompA genes when used as controls were not growth inhibitory. Bactericidal effects exerted by peptide-anti-gyrA PNA and peptide-anti-ompA PNA on cells were observed within 6 h of treatment. The antisense peptide-PNAs specifically inhibited expression of DNA gyrase subunit A and OmpA from the respective targeted genes in a dose-dependent manner. Both antisense peptide-PNAs cured IMR90 cell cultures that were infected with K. pneumoniae (10(4) CFU) in a dose-dependent manner without any noticeable toxicity to the human cells.

What Infection Control Interventions Should Be Undertaken to Control Multidrug-Resistant Gram-Negative Bacteria?

Multidrug-resistant gram-negative bacteria are an emerging problem. The present article addresses 2 relevant questions: (1) should active surveillance be performed to identify patients colonized with multidrug-resistant gram-negative bacteria, and (2) should contact isolation precautions be taken with patients colonized or infected with multidrug-resistant gram-negative bacteria? Data and variables that are needed to scientifically answer these questions are reviewed, as are existing data on Pseudomonas aeruginosa, Enterobacteriaceae (Escherichia coli and Klebsiella species in particular), and Acinetobacter baumannii.

Resistance in gram-negative bacteria: Enterobacteriaceae

The emergence and spread of resistance in Enterobacteriaceae are complicating the treatment of serious nosocomial infections and threatening to create species resistant to all currently available agents. Approximately 20% of Klebsiella pneumoniae infections and 31% of Enterobacter spp infections in intensive care units in the United States now involve strains not susceptible to third-generation cephalosporins. Such resistance in K pneumoniae to third-generation cephalosporins is typically caused by the acquisition of plasmids containing genes that encode for extended-spectrum beta-lactamases (ESBLs), and these plasmids often carry other resistance genes as well. ESBL-producing K pneumoniae and Escherichia coli are now relatively common in healthcare settings and often exhibit multidrug resistance. ESBL-producing Enterobacteriaceae have now emerged in the community as well. Salmonella and other Enterobacteriaceae that cause gastroenteritis may also be ESBL producers, which is of relevance when children require treatment for invasive infections. Resistance of Enterobacter spp to third-generation cephalosporins is most typically caused by overproduction of AmpC beta-lactamases, and treatment with third-generation cephalosporins may select for AmpC-overproducing mutants. Some Enterobacter cloacae strains are now ESBL and AmpC producers, conferring resistance to both third- and fourth-generation cephalosporins. Quinolone resistance in Enterobacteriaceae is usually the result of chromosomal mutations leading to alterations in target enzymes or drug accumulation. More recently, however, plasmid-mediated quinolone resistance has been reported in K pneumoniae and E coli, associated with acquisition of the qnr gene. The vast majority of Enterobacteriaceae, including ESBL producers, remain susceptible to carbapenems, and these agents are considered preferred empiric therapy for serious Enterobacteriaceae infections. Carbapenem resistance, although rare, appears to be increasing. Particularly troublesome is the emergence of KPC-type carbapenemases in New York City. Better antibiotic stewardship and infection control are needed to prevent further spread of ESBLs and other forms of resistance in Enterobacteriaceae throughout the world.

Resistance in gram-negative bacteria: enterobacteriaceae

The emergence and spread of resistance in Enterobacteriaceae are complicating the treatment of serious nosocomial infections and threatening to create species resistant to all currently available agents. Approximately 20% of Klebsiella pneumoniae infections and 31% of Enterobacter spp infections in intensive care units in the United States now involve strains not susceptible to third-generation cephalosporins. Such resistance in K pneumoniae to third-generation cephalosporins is typically caused by the acquisition of plasmids containing genes that encode for extended-spectrum beta-lactamases (ESBLs), and these plasmids often carry other resistance genes as well. ESBL-producing K pneumoniae and Escherichia coli are now relatively common in healthcare settings and often exhibit multidrug resistance. ESBL-producing Enterobacteriaceae have now emerged in the community as well. Salmonella and other Enterobacteriaceae that cause gastroenteritis may also be ESBL producers, which is of relevance when children require treatment for invasive infections. Resistance of Enterobacter spp to third-generation cephalosporins is most typically caused by overproduction of AmpC beta-lactamases, and treatment with third-generation cephalosporins may select for AmpC-overproducing mutants. Some Enterobacter cloacae strains are now ESBL and AmpC producers, conferring resistance to both third- and fourth-generation cephalosporins. Quinolone resistance in Enterobacteriaceae is usually the result of chromosomal mutations leading to alterations in target enzymes or drug accumulation. More recently, however, plasmid-mediated quinolone resistance has been reported in K pneumoniae and E coli, associated with acquisition of the qnr gene. The vast majority of Enterobacteriaceae, including ESBL producers, remain susceptible to carbapenems, and these agents are considered preferred empiric therapy for serious Enterobacteriaceae infections. Carbapenem resistance, although rare, appears to be increasing. Particularly troublesome is the emergence of KPC-type carbapenemases in New York City. Better antibiotic stewardship and infection control are needed to prevent further spread of ESBLs and other forms of resistance in Enterobacteriaceae throughout the world.

Treatment of infections with ESBL-producing organisms: pharmacokinetic and pharmacodynamic considerations

Susceptibility surveillance investigations have demonstrated an increased incidence of ESBL-producing Gram-negative bacilli. Case cohort studies have suggested clinical relevance associated with ESBL-producing Enterobacteriaciae infection. Yet, current laboratory reporting guidelines classify a large percentage of these organisms in the susceptible category. The regulatory agencies Clinical Laboratory Standards Institute (formly NCCLS) and EUCAST, which oversee these guidelines are in the process of re-evaluating the appropriateness of the current classification system. Pharmacokinetic and pharmacodynamic studies examine the relationship between drug exposure (pharmacokinetics), antibiotic potency (MIC), and treatment efficacy. PK/PD studies and analyses have been useful in demonstrating the relevance of increasingly less susceptible pathogens and specific emerging resistance mechanisms. Recent investigations have examined the impact of ESBL-producing Gram-negative bacilli relative to advanced generation cephalosporin pharmacokinetics. Animal model studies suggest that the pharmacodynamic target associated with efficacy in treatment of ESBL-producing organisms is the same as that in therapy against non-ESBL-producing bacteria (50% T>MIC). Simulation of human pharmacokinetics can predict the likelihood of achieving this PD target with specific cephalosporin dosing regimens. In general, the exposure from usual regimens of the advanced generation cephalosporins would not be anticipated to achieve the PD target for many of the organisms currently classified as susceptible. PK/PD analyses should be useful in re-evaluating current susceptibility breakpoints for ESBL-producing organisms and for optimising drug and regimen choice in treatment of these infections.