Prevalence of Ambler class A and D beta-lactamases among clinical isolates of Pseudomonas aeruginosa in Korea

Integron-borne transmission of VEB-1 extended-spectrum β-lactamase in Pseudomonas aeruginosa in a tertiary care hospital in India

A total 14 clinical isolates of Pseudomonas aeruginosa that produced VEB-1 and were susceptible only to polymyxin B were recovered from hospitalized patients. VEB-1 was located within variable regions of the class 1 integron, flanked by resistant genes, and was horizontally transferable as well as carried within the IncP-type plasmid. We conclude that the IncP-type plasmid is responsible for the horizontal transmission of VEB-1-mediated expanded-spectrum cephalosporin resistance in this medical center.

Acquired Class D β-Lactamases

The Class D β-lactamases have emerged as a prominent resistance mechanism against β-lactam antibiotics that previously had efficacy against infections caused by pathogenic bacteria, especially by Acinetobacter baumannii and the Enterobacteriaceae. The phenotypic and structural characteristics of these enzymes correlate to activities that are classified either as a narrow spectrum, an extended spectrum, or a carbapenemase spectrum. We focus on Class D β-lactamases that are carried on plasmids and, thus, present particular clinical concern. Following a historical perspective, the susceptibility and kinetics patterns of the important plasmid-encoded Class D β-lactamases and the mechanisms for mobilization of the chromosomal Class D β-lactamases are discussed.

Spread of extended-spectrum β-lactamase genes of blaOXA-10, blaPER-1 and blaCTX-M in Pseudomonas aeruginosa strains isolated from burn patients

BACKGROUND

Pseudomonas aeruginosa is resistant to many antibiotics due to production of different classes of extended spectrum β-lactamases (ESBLs). Prevalence of ESBLs among P. aeruginosa has been increased in recent years, demonstrate a serious health problem especially in burn units worldwide.

OBJECTIVE

Present study was designed to determine the ESBL producing strains and identify the genes encoding three different ESBLs of bla PER-1, bla OXA-10 and bla CTX-M genes in P. aeruginosa isolates from burn patients.

METHODS

In total 185 clinical isolates of P. aeruginosa were collected from infectious wounds of hospitalized burn patients. Antimicrobial susceptibility testing and phenotypic detection of ESBL were performed by disk diffusion method and Double disk Synergy Test (DDST). Polymerase Chain Reaction (PCR) was done for detection of bla OXA-10, bla PER-1 and bla CTX-M ESBL encoding genes.

RESULTS

In total, 176 (95.13%) isolates were multidrug resistant. The DDST demonstrated 96 (51.9%) isolates as putative ESBL producers with 100% or highly resistance to ofloxacin, cephalexin, aztreonam (97.57%) and ceftriaxone (91.6%). By PCR amplification, bla PER-1, bla OXA-10 and bla CTX-M genes were detected in 52 (54.16%), 66 (68.75%) and 1 (1.04%) isolates of ESBL producers respectively. Forty-three isolates (44.79%) were simultaneously positive for both bla OXA-10 and bla PER-1 related genes.

CONCLUSION

The rate of ESBL producing P. aeruginosa was notable in present study. Since there are only limited effective antibiotics against the bacterium, therefore all isolates must be investigated by antimicrobial susceptibility testing, which limits resistance development in burn units and helps the management of treatment strategy.

Antimicrobial resistance pattern and their beta-lactamase encoding genes among Pseudomonas aeruginosa strains isolated from cancer patients

This study was designed to investigate the prevalence of metallo-β-lactamases (MBL) and extended-spectrum β -lactamases (ESBL) in P. aeruginosa isolates collected from two different hospitals in Cairo, Egypt. Antibiotic susceptibility testing and phenotypic screening for ESBLs and MBLs were performed on 122 P. aeruginosa isolates collected in the period from January 2011 to March 2012. MICs were determined. ESBLs and MBLs genes were sought by PCR. The resistant rate to imipenem was 39.34%. The resistance rates for P. aeruginosa to cefuroxime, cefoperazone, ceftazidime, aztreonam, and piperacillin/tazobactam were 87.7%, 80.3%, 60.6%, 45.1%, and 25.4%, respectively. Out of 122 P. aeruginosa, 27% and 7.4% were MBL and ESBL, respectively. The prevalence of bla(VIM-2), bla(OXA-10(-)), bla(VEB-1), bla(NDM(-)), and bla(IMP-1)-like genes were found in 58.3%, 41.7%, 10.4%, 4.2%, and 2.1%, respectively. GIM-, SPM-, SIM-, and OXA-2-like genes were not detected in this study. OXA-10-like gene was concomitant with VIM-2 and/or VEB. Twelve isolates harbored both OXA-10 and VIM-2; two isolates carried both OXA-10 and VEB. Only one strain contained OXA-10, VIM-2, and VEB. In conclusion, bla(VIM-2)- and bla(OXA-10)-like genes were the most prevalent genes in P. aeruginosa in Egypt. To our knowledge, this is the first report of bla(VIM-2), bla(IMP-1), bla(NDM), and bla(OXA-10) in P. aeruginosa in Egypt.

Antimicrobial resistance pattern and their beta-lactamase encoding genes among Pseudomonas aeruginosa strains isolated from cancer patients

This study was designed to investigate the prevalence of metallo-β-lactamases (MBL) and extended-spectrum β -lactamases (ESBL) in P. aeruginosa isolates collected from two different hospitals in Cairo, Egypt. Antibiotic susceptibility testing and phenotypic screening for ESBLs and MBLs were performed on 122 P. aeruginosa isolates collected in the period from January 2011 to March 2012. MICs were determined. ESBLs and MBLs genes were sought by PCR. The resistant rate to imipenem was 39.34%. The resistance rates for P. aeruginosa to cefuroxime, cefoperazone, ceftazidime, aztreonam, and piperacillin/tazobactam were 87.7%, 80.3%, 60.6%, 45.1%, and 25.4%, respectively. Out of 122 P. aeruginosa, 27% and 7.4% were MBL and ESBL, respectively. The prevalence of bla(VIM-2), bla(OXA-10(-)), bla(VEB-1), bla(NDM(-)), and bla(IMP-1)-like genes were found in 58.3%, 41.7%, 10.4%, 4.2%, and 2.1%, respectively. GIM-, SPM-, SIM-, and OXA-2-like genes were not detected in this study. OXA-10-like gene was concomitant with VIM-2 and/or VEB. Twelve isolates harbored both OXA-10 and VIM-2; two isolates carried both OXA-10 and VEB. Only one strain contained OXA-10, VIM-2, and VEB. In conclusion, bla(VIM-2)- and bla(OXA-10)-like genes were the most prevalent genes in P. aeruginosa in Egypt. To our knowledge, this is the first report of bla(VIM-2), bla(IMP-1), bla(NDM), and bla(OXA-10) in P. aeruginosa in Egypt.

Diversity of β-lactamases produced by imipenem resistant, Pseudomonas aeruginosa isolates from the bloodstream

INTRODUCTION

The emergence of imipenem non-susceptible Pseudomonas aeruginosa isolates is a matter of great concern because these isolates can become resistant to all available antibiotics. This study conducted to characterize β-lactamase genes in imipenem resistant P. aeruginosa isolates from bloodstream.

METHODS

56 non-duplicate clinical isolates of P. aeruginosa were collected in Tehran hospitals. Antibacterial susceptibility was determined by disk diffusion and MIC methods. ESBL and MBL production was confirmed by combined disk. β-Lactamase classes A, B and D genes were identified by PCR.

RESULTS

Seventeen (30.3%) isolates were imipenem resistant for which 16 isolates simultaneously were resistant to all tested antibiotics. While among 39 imipenem susceptible isolates, only two isolates were resistant to all tested antibiotics. In imipenem resistant isolates, blaTEM, blaSHV and blaOXA-10 were found in 41.1% of isolates and blaVIM, blaIMP and blaPER were identified in 47%, 11.7% and 5.8% of isolates respectively, while in imipenem susceptible isolates, blaTEM, blaSHV and blaOXA-10 were determined in 2.5%, 7.6% and 33.3% of isolates, respectively. The imipenem resistant isolates had been recovered mostly (67.7%) from patients in the Burn hospital.

CONCLUSION

The result of this study indicated the emergence of multidrug resistant MBL and non-MBL producing P. aeruginosa, particularly in the Burn hospital and blaVIM was dominant β-lactamase genes in imipenem resistant isolates. The isolation of carrier patients may lead to prevent a further dissemination.

Antimicrobial Resistance Patterns and Prevalence of blaPER-1 and blaVEB-1 Genes Among ESBL-producing Pseudomonas aeruginosa Isolates in West of Iran

BACKGROUND

Pseudomonas aeruginosa is a leading cause of nosocomial infections worldwide. Resistance of P. aeruginosa strains to the broad-spectrum cephalosporins may be caused by extended-spectrum β-lactamases (ESBLs).

OBJECTIVES

The aim of this study was to determine the antimicrobial resistance patterns and prevalence of PER-1 and VEB-1 type genes among ESBL producing strains of P. aeruginosa.

MATERIAL AND METHODS

A total of 106 P. aeruginosa isolates were collected from two university hospitals in Hamadan, Iran, during a7-month study (2009). The antimicrobial susceptibility of isolates was determined by disc diffusion method and interpreted according to the clinical and laboratory standards institute (CLSI) recommendations. Production of ESBL was determined by combined disk test and presence of PER-1 and VEB-1 type ESBL genes was identified by PCR.

RESULTS

The resistance against broad-spectrum cephalosporins and monobactames were: cefepime (97%), cefotaxime (92.5%) ceftazidime (51%), and aztreonam (27%). Ciprofloxacin (91.5%), imipenem (84.9%) and meropenem (82.1%) were the most effective anti-pseudomonas agents in this study. The results revealed that 88.7% of the isolates were multidrug resistant, 58.25% of those were ESBL positive. Sixteen (26.6%), 9 (15%) and 3 (5%) strains among ESBL-producing strains contained blaPER-1, blaVEB and blaPER-1-blaVEB, respectively.

CONCLUSIONS

This study highlighted the need to establish antimicrobial resistance surveillance networks for P. aeruginosa to determine the appropriate empirical treatment regimens. The high prevalence of multidrug resistance and production of ESBLs in P. aeruginosa isolates confirms the necessity of protocols considering these issues in the hospitals.

Detection of SHV type Extended-Spectrum B-lactamase and Risk Factors in Pseudomonas aeruginosa Clinical Isolates

OBJECTIVE

Pseudomonas aeruginosa is one of the most important causes of nosocomial infections and can acquire resistant to many antimicrobials, including β-lactams. The aim of this study was to detect the prevalence of SHV type extended-spectrum beta-lactamase (ESBL), antimicrobial resistance patterns of the P. aeroginusa and risk factors in hospitalized patients in two teaching hospitals in Sanandaj, Iran.

METHODOLOGY

123 P. aeruginosa were isolated from various clinical specimens. All samples were prepared for double-disk synergy test on the isolates for detection of ESBL. SHV was confirmed by PCR method. Risk factors were evaluated for infection due to P. aeruginosa.

RESULTS

The incidence of multiple drug resistance (MDR) in P. aeroginusa isolates was 3.85%. The prevalence of ESBL-SHV gene was 10.57%. Days of hospitalization (OR=14.34 CI95% 2.87-25.8), ICU hospitalization (OR=3.4 CI95% 1.24- 9.29), presence of catheter (OR=3.63 CI 95% 1.34-9.84), use of antimicrobials within previous two weeks (OR=5.51 CI95% 1.85-16.43) and use of ventilator (OR=3.7557 CI95%1.29-9) were risk factors for Pseudomonas nosocomial infection SHV positive ESBL.

CONCLUSION

In this study Prevalence of ESBL, SHV gene and MDR in P. aeroginosa infection was lower than the prevalence reported from other studies in Iran and this indicated appropriate antimicrobial managements strategies and infection control. In addition, our research data indicate that risk factors such as use of ventilator, use of antimicrobials and ICU hospitalization can be effective in managing Pseudomonas infection.

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.

Containment of an outbreak of KPC-3-producing Klebsiella pneumoniae in Italy

From March 2009 to May 2009, 24 carbapenem-resistant Klebsiella pneumoniae isolates were recovered from 16 patients hospitalized in an Italian intensive care unit (ICU). All isolates contained KPC-3 carbapenemase and belonged to a single pulsed-field gel electrophoresis (PFGE) clone of multilocus sequence type 258 (designated as ST258). A multimodal infection control program was put into effect, and the spread of the KPC-3-producing K. pneumoniae clone was ultimately controlled without closing the ICU to new admissions. Reinforced infection control measures and strict monitoring of the staff adherence were necessary for the control of the outbreak.

The prevalence of aminoglycoside-modifying enzyme genes (aac (6')-I, aac (6')-II, ant (2")-I, aph (3')-VI) in Pseudomonas aeruginosa

INTRODUCTION

Pseudomonas aeruginosa (P. aeruginosa) is one of the primary opportunistic pathogens responsible for nosocomial infections. Aminoglycosides are an import ant component of antipseudomonal chemotherapy. The inactivation of drugs by modifying enzymes is the most common mechanism of aminoglycoside resistance.

OBJECTIVES

The inactivation of aminoglycosides by modifying enzymes is the primary resistance mechanism employed by P. aeruginosa. The aim of the present study was to investigate the occurrence of aminoglycoside resistance and the prevalence of four import ant modifying enzyme genes (aac (6')-I, aac (6')-II, ant (2")-I, aph (3')-VI) in P. aeruginosa in Iran.

METHODS

A total of 250 clinical isolates of P. aeruginosa were collected from several hospitals in seven cities in Iran. Antimicrobial susceptibility tests (using the disk diffusion method and E-tests) were performed for all 250 isolates. In addition, all isolates were screened for the presence of modifying enzyme genes by polymerase chain reaction.

RESULTS

The resistance rates, as determined by the disk diffusion method, were as follows: gentamicin 43%, tobramycin 38%, and amikacin 24%. Of the genes examined, aac (6')-II (36%) was the most frequently identified gene in phenotypic resist ant isolates, followed by ant (2")-I, aph (3')-VI, and aac (6')-I.

CONCLUSIONS

Aminoglycoside resistance in P. aeruginosa remains a significant problem in Iran. Therefore, there is considerable local surveillance of aminoglycoside resistance.

Prevalence of ESBLs genes among multidrug-resistant isolates of Pseudomonas aeruginosa isolated from patients in Tehran

Drug susceptibility testing and PCR assay were used to determine the antibiotic susceptibility patterns and prevalence of genes encoding five different extended spectrum betalactamases (ESBLs) (PER, VEB, SHV, GES, and TEM) among 600 isolates of Pseudomonas aeruginosa cultured from patients at two hospitals in Tehran. Susceptibility of isolates to 12 different antibiotics was tested using disk diffusion method. The MICs for ceftazidime and imipenem were also determined using microbroth dilution assay. Isolates showing MICs >or=16 for ceftazidime were subjected to PCR targeting bla(SHV), bla(PER), bla(GES), bla(VEB), and bla(TEM) genes that encode ESBL. The rates of resistance were as follows: tetracycline (92%), carbenicillin (62%), cefotaxime (56%), ceftriaxon (53%), piperacilin (46%), gentamicin (31%), piperacilin/tazobactam (28%), ceftazidime (25%), amikacin (23%), ciprofloxacin (19.5%), and imipenem (6%). Thirty-nine percent of isolates (n = 234) showed MICs >or=16 microg/ml for ceftazidime, and 5.45% showed MICs >or=16 microg/ml for imepenem. The imipenem-resistant isolates showed high rate of susceptibility to colistin (89%) and polymixin B (95.5%). The frequency of bla(VEB), bla(SHV), bla(PER), bla(GES), and bla(TEM) among the ESBL isolates (MIC >or=16) were 24%, 22%, 17%, 0%, and 9%, respectively. Isolates containing bla(VEB) were resistant to almost all tested antibiotics except imepenem. This is the first report on the existence of bla(VEB), and bla(PER) in Iran. Colistin and polymixin B are highly potent against the imipenem-resistant isolates of P. aeruginosa.

Emergence of SHV-2a extended-spectrum beta-lactamases in clinical isolates of Pseudomonas aeruginosa in a university hospital in Tunisia

Extended-spectrum beta-lactamases (ESBLs) in Pseudomonas aeruginosa are increasingly reported worldwide. In our study, a total of 70 clinical isolates of multidrug-resistant P. aeruginosa were studied. Isoelectric focusing electrophoresis, PCR, and PCR product sequencing were designed to characterize the contained ESBLs. The Double Disk Synergy Test in Cloxacillin (250 microg/ml)-containing Mueller-Hinton agar plates with a 20 mm distance between disks was the most reliable ESBL-screening method. Seven out of 70 multidrug-resistant P. aeruginosa clinical isolates were positive for ESBL and have the bla(SHV-2a) ESBL gene. The bla(SHV-2a)-positive isolates were clonally related according to Enterobacterial Repetetive Intergenic Consensus-PCR (ERIC-PCR) results. The bla(SHV-2a) gene was found to be chromosomally located, and the flanking IS26 sequence in the immediate upstream region of the bla(SHV-2a) gene was detected in all SHV-2a-producing isolates. This is the first report of SHV-2a-producing P. aeruginosa isolates from Tunisia.

Detection of VEB-1, OXA-10 and PER-1 genotypes in extended-spectrum beta-lactamase-producing Pseudomonas aeruginosa strains isolated from burn patients

Resistance of Pseudomonas aeruginosa strains to the broad-spectrum cephalosporins may be mediated by the extended-spectrum beta-lactamases (ESBLs). These enzymes are encoded by different genes located on either chromosomes or plasmids. This study aimed to investigate the prevalence of ESBLs and antimicrobial susceptibilities of P. aeruginosa isolated from burn patients in Tehran, Iran. Antimicrobial susceptibility of 170 isolates to cefpodoxime, aztreonam, ciprofloxacin, ofloxacin, ceftazidime, cefepime, imipenem, meropenem, cefotaxime, levofloxacin, piperacillin-tazobactam and ceftriaxone was determined by disc agar diffusion test. Polymerase chain reaction (PCR) amplification of the genes encoding OXA-10, PER-1 and VEB-1 was also performed. All isolates (100%) were resistant to ceftazidime, cefotaxime, cefepime and aztreonam. Imipenem and meropenem were the most effective anti-pseudomonal agents. The results revealed that 148 (87.05%) of the isolates were multidrug resistant and 67 (39.41%) of the isolates were ESBL positive. Fifty (74.62%), 33 (49.25%) and 21 (31.34%) strains among 67 ESBL-producing strains amplified blaOXA-10, blaPER-1 and blaVEB-1 respectively. In conclusion, the high prevalence of multidrug resistance (87.05%) and production of OXA-10, PER-1 and VEB-1 genes in P. aeruginosa isolates in burn patients confirm that protocols considering these issues should be considered in burn hospitals.

[Dissemination of IMP-1 and OXA type beta-lactamase in carbapenem-resistant Acinetobacter baumannii]

BACKGROUND

Acinetobacter baumannii is an aerobic, gram-negative, glucose-nonfermenting bacterium, which has emerged as a serious opportunistic pathogen. In recent years, the increasing instance of carbapenem-resistant A. baumannii producing metallo-beta-lactamases (MBLs) or OXAtype beta-lactamases is causing a serious clinical problem. In this study, we investigated the prevalence of Ambler class A, B, and D beta-lactamases and their extended-spectrum derivatives in carbapenem-resistant A. baumannii isolates.

METHODS

A total of 31 consecutive, non-duplicate, carbapenem-resistant A. baumannii were isolated from three university hospitals in the Chungcheong province of Korea. The modified Hodge and inhibitor-potentiated disk diffusion tests were conducted for the screening of carbapenemase and MBL production, respectively. PCR and DNA sequencing were performed for the detection of beta-lactamase genes. We also employed the enterobacterial repetitive intergenic consensus (ERIC)-PCR method for the epidemiologic study.

RESULTS

Twenty-three of 31 isolates harbored bla(OXA-2)(51.6%), bla(OXA-23)(22.6%), bla(IMP-1)(48.4%),and bla(VIM-2)(3.2%). All of the OXA-2-producing strains also evidenced MBLs. The strains that harbored bla(OXA-23)were isolated only in hospital C, and only in a limited fashion. The ERIC-PCR pattern of the five OXA-23 strains indicated that the isolates were closely related in terms of clonality. The six strains producing IMP-1 isolated from hospital A were confirmed to be identical strains.

CONCLUSIONS

A. baumannii strains harboring IMP-1 or OXA-type beta-lactamases are currently widely distributed throughout the Chungcheong province of Korea. The most notable finding in this study was that a bla(OXA-2)-producing A. baumannii harboring MBL, which has not been previously reported, can also lead to outbreaks.

Occurrence and mechanisms of amikacin resistance and its association with beta-lactamases in Pseudomonas aeruginosa: a Korean nationwide study

OBJECTIVES

We investigated the occurrence and mechanism of amikacin resistance and its association with various beta-lactamase genes in Pseudomonas aeruginosa isolates.

METHODS

Of the total 250 consecutive, non-duplicated isolates of P. aeruginosa, 55 isolates showed amikacin resistance. PCR amplification of genes for aminoglycoside (AG)-modifying enzymes [aac(3)-I, aac(3)-II/VI, aac(3)-III/IV, aac(6')-I, aac(6')-II, ant(2'')-I, ant(4')-II and aph(3')-VI], 16S rRNA methylases (rmtA, rmtB, rmtC and armA) and class 1 integrons was performed. In addition, we analysed the association of AG resistance genes with various beta-lactamase genes.

RESULTS AND CONCLUSIONS

In Korea, the amikacin resistance rate in P. aeruginosa was high (22%), and it varied among provinces (3.8% to 40%). Four types of AG-modifying enzyme genes [aph(3')-VI, ant(2'')-I, aac(6')-I and aac(3)-II/VI] were found in 48 isolates. Thirty-six strains harboured two or more types of enzymes, of which a combination of aph(3')-VI and ant(2'')-I was the most frequent (24/36 isolates, 66.7%). None harboured aac(3)-I, aac(3)-III/IV, aac(6')-II, ant(4')-II, rmtA, rmtB, rmtC or armA. Forty-two isolates co-harboured beta-lactamase genes (mostly bla(OXA-10)). A class 1 integron was detected in all but one, and all the ant(2'')-I and 26/29 bla(OXA-10) were found in it. In contrast, aph(3')-VI was not found to be associated with the class 1 integron. Considering the possibility of co-selection and dissemination, constant monitoring of resistance evolution is necessary.

Imported PER-1 producing Pseudomonas aeruginosa, PER-1 producing Acinetobacter baumanii and VIM-2-producing Pseudomonas aeruginosa strains in Hungary

Introduction

Pseudomonas aeruginosa and Acinetobacter baumanii are important nosocomial pathogens with wide intrinsic resistance. However, due to the dissemination of the acquired resistance mechanisms, such as extended-spectrum beta-lactamase (ESBL) and metallo beta-lactamase (MBL) production, multidrug resistant strains have been isolated more often.

Case presentation

We report a case of a Hungarian tourist, who was initially hospitalized in Egypt and later transferred to Hungary. On the day of admission PER-1-producing P. aeruginosa, PER-1 producing A. baumannii, SHV-5-producing Klebsiella pneumoniae and VIM-2-producing P. aeruginosa isolates were subcultured from the patient's samples in Hungary. Comparing the pulsed-field gel electrophoresis (PFGE) patterns of the P. aeruginosa strains from the patient to the P. aeruginosa strains occurring in this hospital, we can state that the PER-1-producing P. aeruginosa and VIM-2-producing P. aeruginosa had external origin.

Conclusion

This is the first report of PER-1-producing P. aeruginosa,and PER-1-producing A. baumanii strains in Hungary. This case highlights the importance of spreading of the beta-lactamase-mediated resistance mechanisms between countries and continents, showing the importance of careful screening and the isolation of patients arriving from a different country.

Minor extended-spectrum beta-lactamases

Extended-spectrum beta-lactamases (ESBLs) are usually plasmid-mediated enzymes that confer resistance to a broad range of beta-lactams. Initially, resistance to third-generation cephalosporins in Gram-negative rods was mainly due to the dissemination of TEM- and SHV-type ESBLs, which are point mutants of the classic TEM and SHV enzymes with extended substrate specificity. During the last ten years, CTX-M-type ESBLs have become increasingly predominant, but less frequent class A beta-lactamases have also been described, including SFO, BES, BEL, TLA, GES, PER and VEB types. While several of these latter are rarely identified, or are very localised, others are becoming locally prevalent, or are increasingly isolated worldwide. In addition, mutations can extend the spectrum of some OXA-type beta-lactamases to include expanded-spectrum cephalosporins, and several of these enzymes are considered to be ESBLs.

Problematic clinical isolates of Pseudomonas aeruginosa from the university hospitals in Sofia, Bulgaria: current status of antimicrobial resistance and prevailing resistance mechanisms

A total of 203 clinical isolates of Pseudomonas aeruginosa was collected during 2001–2006 from five university hospitals in Sofia, Bulgaria, to assess the current levels of antimicrobial susceptibility and to evaluate resistance mechanisms to antipseudomonal antimicrobial agents. The antibiotic resistance rates against the following antimicrobials were: carbenicillin 93.1 %, azlocillin 91.6 %, piperacillin 86.2 %, piperacillin/tazobactam 56.8 %, ceftazidime 45.8 %, cefepime 48.9 %, cefpirome 58.2 %, aztreonam 49.8 %, imipenem 42.3 %, meropenem 45.5 %, amikacin 59.1 %, gentamicin 79.7 %, tobramycin 89.6 %, netilmicin 69.6 % and ciprofloxacin 80.3 %. A total of 101 of the studied P. aeruginosa isolates (49.8 %) were multidrug resistant. Structural genes encoding class A and class D β-lactamases showed the following frequencies: bla VEB-1 33.1 %, bla PSE-1 22.5 %, bla PER-1 0 %, bla OXA-groupI 41.3 % and bla OXA-groupII 8.8 %. IMP- and VIM-type carbapenemases were not detected. In conclusion, the studied clinical strains of P. aeruginosa were problematic nosocomial pathogens. VEB-1 extended-spectrum β-lactamases appear to have a significant presence among clinical P. aeruginosa isolates from Sofia. Carbapenem resistance was related to non-enzymic mechanisms such as a deficiency of OprD proteins and active efflux.

Prevalence and mechanisms of decreased susceptibility to carbapenems in Klebsiella pneumoniae isolates

In this study, we examined the prevalence of and mechanisms of decreased susceptibility to either imipenem or meropenem in Klebsiella pneumoniae isolates. A total of 230 clinical isolates of K. pneumoniae were collected from 13 clinical laboratories from a nationwide distribution. The MICs of imipenem and meropenem were determined by the agar dilution method. To characterize the isolates with decreased susceptibility to carbapenems (MICs of >2 microg/mL), we performed polymerase chain reaction amplification of a variety of beta-lactamase genes, isoelectric focusing, and outer membrane profile analysis using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and mass spectrometry. Three isolates (BD6, BD8, and KN16) exhibited decreased susceptibility to carbapenems with imipenem MICs of 1, 4, and 8 microg/mL and meropenem MICs of 4, 8, and 4, respectively. Isolate BD6 produced bla(TEM-1), bla(SHV-12), and bla(OXA-17); isolate BD8 produced bla(GES-3), bla(SHV-12), and bla(OXA-17); and isolate KN16 produced bla(TEM-11), bla(SHV-12), and bla(DHA-1). In all the 3 isolates, OmpK35 porin was not expressed, and in 1 isolate (KN16), OmpK36 was not expressed either. The prevalence of decreased susceptibility to carbapenems was low (1.3%), and none of them showed overt resistance to carbapenems. Decreased susceptibility to carbapenems can occur in K. pneumoniae when bla(GES-3), bla(TEM-11), bla(SHV-12), bla(OXA-17), and/or bla(DHA-1) are produced in combination with porin loss. In addition, to our knowledge, this is the 1st report of bla(OXA-17) in Enterobacteriaceae.

Detection of extended-spectrum beta-lactamases in clinical isolates of Pseudomonas aeruginosa

With the occurrence of extended-spectrum beta-lactamases (ESBLs) in Pseudomonas aeruginosa being increasingly reported worldwide, there is a need for a reliable test to detect ESBLs in clinical isolates of P. aeruginosa. In our study, a total of 75 clinical isolates of P. aeruginosa were studied. Nitrocefin tests were performed to detect the beta-lactamase enzyme; isoelectric focusing electrophoresis, PCR, and PCR product sequencing were designed to further characterize the contained ESBLs. Various ESBL-screening methods were designed to compare the reliabilities of detecting ESBLs in clinical isolates of P. aeruginosa whose beta-lactamases were well characterized. Thirty-four of 36 multidrug-resistant P. aeruginosa clinical isolates were positive for ESBLs. bla(VEB-3) was the most prevalent ESBL gene in P. aeruginosa in our study. Among the total of 34 isolates that were considered ESBL producers, 20 strains were positive using conventional combined disk tests and 10 strains were positive using a conventional double-disk synergy test (DDST) with amoxicillin-clavulanate, expanded-spectrum cephalosporins, aztreonam, and cefepime. Modifications of the combined disk test and DDST, which consisted of shorter distances between disks (20 mm instead of 30 mm) and the use of three different plates that contained cloxacillin (200 microg/ml) alone, Phe-Arg beta-naphthylamide dihydrochloride (MC-207,110; 20 microg/ml) alone, and both cloxacillin (200 microg/ml) and MC-207,110 (20 microg/ml) increased the sensitivity of the tests to 78.8%, 91.18%, 85.29%, and 97.06%.