Outbreak of ceftazidime-resistant Klebsiella pneumoniae in a pediatric hospital in Warsaw, Poland: clonal spread of the TEM-47 extended-spectrum beta-lactamase (ESBL)-producing strain and transfer of a plasmid carrying the SHV-5-like ESBL-encoding gene

High Prevalence of blaOXA-48 and blaNDM-Producing Carbapenem-Resistant Klebsiella pneumoniae Isolated from Clinical Samples in Shahid Rajaei Hospital in Tehran, Iran

Background: Due to the increasing antibiotic resistance, treating infections caused by Klebsiella pneumoniae has become more challenging. Objectives: The present study aimed to investigate the prevalence of blaOXA-48 and blaNDM producing carbapenem-resistant K. pneumoniae isolated from clinical samples in Shahid Rajaei hospital in Tehran, Iran. Methods: Various clinical samples were collected from 1,186 patients admitted with open heart surgery in two wards (ICU and surgery) in Shahid Rajaei Heart Hospital in Tehran, Iran. Klebsiella pneumoniae isolates were identified by standard microbiologic tests. Antimicrobial susceptibility of isolates were determined by disk diffusion and E-test methods. A modified carbapenem inactivation method (mCIM) was performed to detect the presence of carbapenemase. Antibiotic resistance genes were detected using conventional polymerase chain reaction (PCR) by primers targeting blaOXA-48, blaSPM, blaIMP, blaVIM, and blaNDM genes. Results: A total of 131 clinical isolates of K. pneumoniae were isolated and 45.8% (60/131) of them were resistant to carbapenem. Klebsiella pneumoniae isolates showed the highest resistance rate (100%) to ceftriaxone, ceftazidime, cefazolin, and cefepime and the maximum sensitivity to tigecycline (96.7%). The carbapenemase-encoding blaOXA-48 and blaNDM-1 genes were detected in 96.7% and 66.7% of isolates, respectively. Eight different clusters of the isolates, considering a ≥ 80% homology cut-off, were shown with the same rep-PCR pattern. Clusters A, B, C, D, E, F, G, and H included 20, 11, 7, 6, 6, 3, 2, and 2 members, respectively. Conclusions: The RAPD-PCR method reveals the clonal relationship between isolates and may help improve infection control procedures.

Evolution of Beta-Lactamases in Urinary Klebsiella pneumoniae Isolates from Croatia; from Extended-Spectrum Beta-Lactamases to Carbapenemases and Colistin Resistance

K. pneumoniae isolates often harbor various antibiotic resistance determinants including extended-spectrum β-lactamases (ESBLs), plasmid-mediated AmpC β-lactamases (p-Amp-C) and carbapenemases. In this study we analyzed 65 K. pneumoniae isolates obtained from urinary tract infections in the outpatients setting, with regard to antibiotic susceptibility, β-lactamase production, virulence traits and plasmid content.Antibiotic susceptibility was determined by broth microdilution method. PCR was applied to detect genes encoding ESBLs, p-Amp-C and carbapenemases and plasmid incompatibility groups. Phenotypic methods were applied to characterize virulence determinants. Increasing resistance trend was observed for amoxicillin/clavulanate, imipenem, meropenem and ciprofloxacin. The study showed that ESBLs belonging to the CTX-M family, conferring high level of resistance to expanded-spectrum cephalosporins (ESC) were the dominant resistance trait among early isolates (2013 to 2016) whereas OXA-48 carbapenemase, belonging to class D, emerged in significant numbers after 2017. OXA-48 producing organisms coharbored ESBLs. KPC-2 was dominant among isolates from Dubrovnik in the recent years. Colistin resistance was reported in three isolates. Inc L/M was the dominant plasmid in the later period, encoding OXA-48. Hyperviscosity was linked to KPC positivity and emerged in the later period. This report describes evolution of antibiotic resistance in K. pneumoniae from ESBLs to carbapenemases and colistin resistance. The study demonstrated the ability of K. pneumoniae to acquire various resistance determinants, over time. The striking diversity of the UTI isolates could result from introduction of the isolates from the hospitals, transfer of plasmids and multidirectional evolution.

Mechanisms of Resistance in Gram-Negative Urinary Pathogens: From Country-Specific Molecular Insights to Global Clinical Relevance

Urinary tract infections (UTIs) are the most frequent hospital infections and among the most commonly observed community acquired infections. Alongside their clinical importance, they are notorious because the pathogens that cause them are prone to acquiring various resistance determinants, including extended-spectrum beta-lactamases (ESBL); plasmid-encoded AmpC β-lactamases (p-AmpC); carbapenemases belonging to class A, B, and D; qnr genes encoding reduced susceptibility to fluoroquinolones; as well as genes encoding enzymes that hydrolyse aminoglycosides. In Escherichia coli and Klebsiella pneumoniae, the dominant resistance mechanisms are ESBLs belonging to the CTX-M, TEM, and SHV families; p-AmpC; and (more recently) carbapenemases belonging to classes A, B, and D. Urinary Pseudomonas aeruginosa isolates harbour metallo-beta-lactamases (MBLs) and ESBLs belonging to PER and GES families, while carbapenemases of class D are found in urinary Acinetobacter baumannii isolates. The identification of resistance mechanisms in routine diagnostic practice is primarily based on phenotypic tests for the detection of beta-lactamases, such as the double-disk synergy test or Hodge test, while polymerase chain reaction (PCR) for the detection of resistance genes is mostly pursued in reference laboratories for research purposes. As the emergence of drug-resistant bacterial strains poses serious challenges in the management of UTIs, this review aimed to appraise mechanisms of resistance in relevant Gram-negative urinary pathogens, to provide a detailed map of resistance determinants in Croatia and the world, and to discuss the implications of these resistance traits on diagnostic approaches. We summarized a sundry of different resistance mechanisms among urinary isolates and showed how their prevalence highly depends on the local epidemiological context, highlighting the need for tailored interventions in the field of antimicrobial stewardship.

Gram-negative bacteria as causative agents of ventilator-associated pneumonia and their respective resistance mechanisms

Ventilator-associated pneumonia (VAP) is a serious and common complication in patients admitted to intensive care unit (ICU) and contributes to mortality. Multidrug Gram-negative bacteria such as Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae are frequently associated with VAP in ICU. A prospective study was set up in three ICUs of the University Hospital Center Zagreb and one ICU in General Hospital Pula from September 2017 to March 2018. Antibiotic susceptibility was determined by broth microdilution method. Production of extended-spectrum β-lactamases (ESBLs) was determined by double-disk synergy test and carbapenemases by Hodge and carbapenem inactivation method (CIM). The genes encoding ESBLs, carbapenemases of class A, B and D and qnr genes were determined by PCR. In total 97 Gram-negative bacteria isolates were analyzed. P. aeruginosa demonstrated high resistance rates for imipenem and meropenem with 74% and 68% of resistant strains, respectively. Moderate resistance rates were observed for ceftazidime andpiperacillin/tazobactam, ciprofloxacin and gentamicin (44%). All except three A. baumannii isolates, were resistant to carbapenems and to all other antibiotics apart from colistin and amikacin. Eight A. baumannii isolates were positive for bla_OXA-23 and 12 for bla_OXA-24 genes. Four K. pneumoniae and two E. cloacae strains were ESBL positive and harboured group 1 of CTX-M β-lactamases. Three P. mirabilis strains were positive for plasmid-mediated ampC β-lactamase of CMY family. Two carbapenem-resistant K. pneumoniae harboured OXA-48 and one carbapenem-resistant E. cloacae VIM-1. A high proportion of multidrug-resistant P. aeruginosa, K. pneumoniae and extensively resistant A. baumannii was reported. Acquired resistance mechanisms, mainly production of carbapenemases and ESBLs were dominant in A. baumannii and K. pneumoniae, respectively. Resistance of P. aeruginosa isolates was more likely due to upregulation of efflux pumps or porin loss. A marked diversity of β-lactamases was identified in Enterobacteriaceae.

Prevalence of Resistance to β-Lactam Antibiotics and bla Genes Among Commensal Haemophilus parainfluenzae Isolates from Respiratory Microbiota in Poland

(1) Background: Beta-lactams are the most frequently used antimicrobials, and are the first-line drugs in many infectious diseases, e.g., pneumonia, otitis media. Due to this fact, various bacteria have developed resistance to this group of drugs. (2) Methods: Eighty-seven Haemophilus parainfluenzae isolates were obtained from adults 18–70 years old in eastern Poland. The presence of 10 bla genes and 2 substitutions in ftsI reported as the most frequent in H. parainfluenzae were analyzed. (3) Results: Among 57 beta-lactam-resistant isolates, 63.2% encoded bla genes; bla_TEM-1 predominated (54.4%), followed by bla_OXA (19.3%), bla_DHA (12.3%), bla_SHV (10.5%), bla_GES (7.0%), bla_CMY (5.3%), bla_VEB (1.8%) and bla_ROB-1 (1.8%). Lys-526 was the most common substitution in ftsI gene. The resistance genotypes were as follows: gBLNAS (17.5%), low-gBLNAR I (1.8%), low-gBLNAR II (1.8%), gBLNAR II (15.8%), gBLPAS (15.8%), gBLPAR (19.3%), gBLPBS I (8.8%) and gBLPBS II (1.8%); (4) Conclusions: This has been the first study to report on the high diversity of bla genes in H. parainfluenzae isolates in Poland. High sensitivity and specificity of benzylpenicillin test, as well as PCR of bla genes were shown, indicating that these methods may be useful as tools for the rapid screening of beta-lactamase prevalence and resistance to beta-lactams among H. parainfluenzae isolated from respiratory microbiota.

Molecular Epidemiology of Extended-Spectrum β-Lactamase-Producing Escherichia coli Pathotypes in Diarrheal Children from Low Socioeconomic Status Communities in Bihar, India: Emergence of the CTX-M Type

Background

Childhood diarrheal diseases remain highly endemic in India, but the emergence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli among children with diarrhea in Bihar remains elusive. In this study, we determine and characterize ESBL-producing E coli pathotypes among hospitalized diarrheal preschool children living in low socioeconomic level communities in Bihar, India.

Materials and methods

The stool samples were collected everyday throughout the year for 2 consecutive years. In our study, we collected stool samples randomly from every fifth patient. Stool samples were collected from a total of 633 randomly selected diarrheal children (age: 0-60 months) belonging to 17 communities and screened for identification of virulent diarrheagenic E coli (DEC) pathotype (viz, enteropathogenic E coli [EPEC], enteroaggregative E coli [EAEC], enterotoxigenic E coli [ETEC], enteroinvasive E coli [EIEC], and enterohemorrhagic E coli [EHEC]) by a multiplex polymerase chain reaction (PCR) assay. Furthermore, ESBLs were screened by conventional antibiotic resistance pattern testing and later characterized for the presence of β-lactamase (bla) genes by PCR and DNA sequencing.

Results

Diarrheagenic E coli was detected in 191 cases (30.2%) of the total 633 diarrheic children. Maximum occurrence of DEC was found in ≤12 months age group (72.7%) with prevalence of the EAEC pathotype. Most isolates were resistant to ampicillin, ciprofloxacin, piperacillin, levofloxacin, ceftazidime, cefotaxime, ceftriaxone, and gentamicin, whereas over 96% of them were sensitive to amikacin. About 37.6% of total 191 DEC isolates were ESBL producers (n = 72), being prevalent among ETEC (n = 35; 18.32%), followed by EPEC (n = 21; 10.9%), EAEC (n = 13; 6.8%), and EIEC (n = 3; 1.57%). Interestingly, the commonest β-lactamase was CTX-M type (bla_CTX-M) in 86.1% (n = 62) of the ESBL isolates, followed by bla_SHV (n = 49; 68%), bla_TEM (n = 37; 51.8%), and bla_OXA (n = 21; 29.1%) determinants. Resistance of ESBL isolates was mostly related to ampicillin (100%), ceftriaxone (98.1%), cefotaxime (92.4%), gentamicin (74.1%), and levofloxacin (73.2%), whereas best antimicrobial activities were observed for piperacillin-tazobactam, amikacin, meropenem, and imipenem.

Conclusions

This study revealed that EAEC (72.1%) is the predominant pathotype in Bihar, significantly high in ≤12 months age group children (P = .04). Moreover, the widespread prevalence of ESBLs in children, especially the CTX-M type, is of great concern, which requires monitoring of infection control measures through efficient antimicrobial management and detection of ESBL-producing isolates.

CTX-M-type extended-spectrum β-lactamase-producing Klebsiella pneumoniae isolated from cases of bovine mastitis in Japan

Three Klebsiella pneumoniae isolates producing extended-spectrum beta-lactamase (ESBL) were obtained from three dairy cows with clinical mastitis in two farms in western Japan. Two of the 3 isolates from cows in different farms were able to transfer plasmids carrying the blaCTX-M-2 gene to Escherichia coli recipient. Pulsed-field gel electrophoresis (PFGE) patterns of the 2 isolates were different from each other, although restricted-fragment patterns of the two conjugative plasmids were similar to each other. Additionally, PCR-based replicon typing revealed that both the plasmids belonged to type Inc.T. These results suggest that ESBL-encoding genes can be distributed in bacteria on dairy farms through the plasmids.

Development of an optimized random amplified polymorphic DNA protocol for fingerprinting of Klebsiella pneumoniae

AIMS

To develop an optimized random amplified polymorphic DNA (RAPD) protocol for fingerprinting clinical isolates of Klebsiella pneumoniae.

METHODS AND RESULTS

Employing factorial design of experiments, repeatable amplification patterns were obtained for 54 nosocomial isolates using 1 μmol 1(-1) primer, 4 mmol 1(-1) MgCl(2), 0·4 mmol 1(-1) dNTPs, 2·5 U Taq DNA polymerase and 90 ng DNA template in a total volume of 25 μl. The optimum thermocycling program was: initial denaturation at 94°C for 4 min followed by 50 cycles of 1 min at 94°C, 2 min at 34°C, 2 min at 72°C and a final extension at 72°C for 10 min. The optimized RAPD protocol was highly discriminatory (Simpson's diversity index, 0·982), and all isolates were typable with repeatable patterns (Pearson's similarity coefficient ≈ 100%). Seven main clusters were obtained on a similarity level of 70% and 32 distinct clusters on a similarity level of 85%, reflecting the heterogeneity of the isolates.

CONCLUSIONS

Systematic optimization of RAPD generated reliable DNA fingerprints for nosocomial isolates of K. pneumoniae.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report on RAPD optimization based on factorial design of experiments for discrimination of K. pneumoniae.

Molecular characterization and epidemiology of extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae isolates in the United Arab Emirates

OBJECTIVES

The aim of this prospective study was to assess the extent of dissemination of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae at the hospital level in the United Arab Emirates (UAE).

MATERIALS AND METHODS

A total of 662 Escherichia coli and Klebsiellapneumoniae samples were collected from three UAE hospitals between January and December 2008. ESBL screening and confirmatory test for ESBL phenotype were conducted using the VITEK system. Molecular typing was performed using specific primers and then sequencing.

RESULTS

A total of 240 (36%) samples were identified as ESBL producers, including both E. coli (n = 150) and K. pneumoniae (n = 90). All of these isolates were resistant to cefazoline and cefotaxime, but remained susceptible to imipenem. Molecular analysis revealed that, of the 240 ESBL producers, 228 carried the ESBL bla genes. A majority of the strains 199 (87%) expressed the CTX-M-15 gene. The SHV-28 gene was detected in 29 (13%) of the strains.

CONCLUSION

The present study highlighted the emergence and dissemination of CTX-M-15-producing E. coli and K. pneumoniae in the UAE. This is the first report of SHV-28-producing Enterobacteriaceae in the country.

Characterization of extended-spectrum beta-lactamases in Enterobacteriaceae causing nosocomial infections in a Zagreb University Hospital

The bacteria producing extended-spectrum beta-lactamases (ESBLs) are increasingly reported. production of ESBLs by Gram-negative bacteria is the major mechanism of resistance to oxymino-cephalosporins and aztreonam. the aim of the present study was to characterize ESBLs produced by Enterobacteriaceae, collected during 2003-2005 in a University Hospital in Zagreb, and to determine the risk factors associated with nosocomial infections due to them. 76 isolates of Enterobacteriaceae were included in the study. Antibiotic susceptibility testing was performed by disk-diffusion and broth microdilution method according to CLSI. beta-lactamases were characterized by PCR and sequencing of bla(ESBL )genes. plasmids were extracted by alkaline lysis method and digested with EcoRI enzyme. Most of the strains displayed CAZ phenotype meaning a higher level of resistance to ceftazidime compared to cefotaxime and ceftriaxone. 50 strains produced SHV-ESBL, 28 tem and 8 CTX-M beta-lactamase. Sequencing of bla(SHV )genes from representative strains revealed SHV-5 beta-lactamase in 6 strains whereas sequencing of bla(CTX-M )genes identified CTX-M-3 beta-lactamase in 3 and CTX-M-15 in 5 strains. Strains were assigned to groups from A to f according to plasmid fingerprinting. The spread of SHV-5-producing strains throughout the hospital units could be due to selective pressure of ceftazidime which is widely prescribed in our hospital thus favoring survival of strains possessing a mutation at the Ambler position 240 responsible for ceftazidime and aztreonam resistance.

Cluster of bloodstream infections caused by KPC-2 carbapenemase-producing Klebsiella pneumoniae in Manhattan

BACKGROUND

Carbapenems are considered the agents of choice for treatment of serious infections caused by resistant gram-negative organisms. A new group of class A beta-lactamases, known as KPC-type carbapenemases, has recently been described and poses a serious clinical challenge.

METHODS

Seven patients with bloodstream infections caused by Klebsiella pneumoniae isolates with decreased susceptibility to carbapenems were identified between January and April 2005 in the intensive care units of a hospital in Manhattan. Isolate identification and susceptibility testing were performed according to National Committee for Clinical Laboratory Standards methodology. All isolates were ribotyped and screened for (bla)KPC by polymerase chain reaction. The polymerase chain reaction product underwent nucleotide sequencing for one of the isolates. Medical records were reviewed retrospectively.

RESULTS

Six isolates were carbapenem-resistant with minimum inhibitory concentrations for imipenem of >8microg/mL. Ribotyping showed that all isolates belonged to a single clone. All isolates possessed (bla)KPC and nucleotide sequencing identified the allelic type KPC-2. Patients' median age was 68 years. The median duration of hospitalization was 25.5 days before the first positive blood culture. Five of 6 patients received previous broad-spectrum beta-lactam antibiotics but none received prior carbapenems. Five of 6 isolates were susceptible to polymyxin B. Three of the 5 patients were treated with polymyxin B and 1 survived. Overall, only 2 of the 6 patients survived.

CONCLUSION

This report describes the first outbreak of KPC-2 carbapenemase-producing K pneumoniae bloodstream infections in a hospital in Manhattan.

Molecular epidemiology and risk factors of bloodstream infections caused by extended-spectrum beta-lactamase-producing Klebsiella pneumoniae A case-control study

OBJECTIVES

To study the prevalence, risk factors, outcome, and molecular epidemiology in patients with bacteremia caused by extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae (Kp) (cases), in comparison with patients with bacteremia caused by a susceptible Kp (controls).

METHODS

This was a retrospective case-control study including all episodes of Kp bacteremia for the period 1993 to 2002 at a referral hospital for adults in Mexico. ESBL production was tested for by E-test. All isolates were typed by pulsed field gel electrophoresis (PFGE). A subset of isolates underwent plasmid analysis, conjugal transfer of cefotaxime resistance to Escherichia coli J53-2, isoelectric focusing bioassay, colony-blot hybridization, PCR, and sequencing.

RESULTS

Of the 121 patients with bacteremia due to Kp included in the study, 17 (14.0%) had an ESBL-Kp isolate (cases). Multivariate analysis identified prior use of cephalosporins (OR 7.6, 95% CI 1.1-53.5; p=0.039) and stay in the intensive care unit (ICU; OR 5.6, 95% CI 1.1-27.9; p=0.033) as significant risk factors. No differences were observed in hospital stay or mortality after the event. Multi-drug resistance was more frequent in ESBL-Kp. There was no clonal predominance. A distinct beta-lactamase profile was identified, which included a combination of TEM-1 (pI 5.4) and SHV-5 (pI 8.2) in 13/17 ESBL-Kp isolates. Cefotaxime resistance was transferred by conjugation in 14/17 isolates with a >120-kb plasmid encoding ESBL.

CONCLUSIONS

The prevalence of ESBL-Kp was found to be lower than that previously reported in Latin America. ESBL-Kp bacteremia was not associated with a worse clinical outcome. We were able to identify a plasmid-mediated horizontal dissemination over the 10-year period.

First characterization in Tunisia of a TEM-15, extended-spectrum beta-lactamase-producing Klebsiella pneumoniae isolate

Klebsiella pneumoniae CH0905 strain exhibiting high-level cefotaxime resistance was isolated from a stool culture in the intensive care unit. The resistance gene responsible was shown to be located on a conjugative 60-kb plasmid designated pCH0905. The minimum inhibitory concentration (MIC) values for cefotaxime and ceftazidime of the original isolate and the transconjugates were 256 mug/ml. Isoelectric focusing of a protein preparation from the K. pneumoniae strain showed beta-lactamases with the pI values of 7.6 and 6.3. A 1,080-bp fragment amplified with PCR was cloned into the pGEM-T Easy vector. The nucleotide sequence of the complete 1,080 bp was determined. Sequence analysis revealed that the bla(TEM) gene of pCH0905 differed from bla(TEM-1) by two mutations, leading to the following amino acid substitutions: the glutamic acid residue at position 104 by lysine and the glycine residue at position 238 by serine (Ambler numbering). The association of these two mutations was described previously in TEM-15 beta-lactamase, but this is the first detection of this enzyme in Tunisia.

Epidemiology of SHV-type β-lactamase-producing Klebsiella spp. from outbreaks in five geographically distant Hungarian neonatal intensive care units: widespread dissemination of epidemic R-plasmids

One hundred and twenty-six extended-spectrum beta-lactamase-producing clinical isolates of Klebsiella spp. were collected in 1998, 2002 and 2003 from seven outbreaks in neonatal intensive care units (NICUs) of five Hungarian county and teaching hospitals. The isolates were multidrug resistant but were susceptible to ciprofloxacin. Pulsed-field gel electrophoresis revealed the existence of 12 distinct genetic clones, 10 of which proved epidemic in the studied NICUs. All isolates harboured plasmids ranging from 2.3 kb to 228 kb, representing 12 diverse plasmid profiles. Sequence analysis of SHV-specific polymerase chain reaction products from 13 representative isolates detected the bla(SHV-2a) gene in three and the bla(SHV-5) gene in seven epidemic clones, respectively. In the majority of isolates the bla(SHV) genes were on transferable plasmids of 94kb. EcoRI and PstI digestion of plasmid DNA from transconjugants revealed identical or closely related restriction patterns in nine bla(SHV-5)-harbouring R-plasmids and in two bla(SHV-2a)-harbouring R-plasmids carried by strains obtained from geographically distant NICUs. Endemic clones in individual wards or epidemic clones affecting multiple healthcare facilities were not found. However, similarities observed in the size and restriction pattern of the plasmids hints at the multiple transfer of epidemic R-plasmids responsible for a sequence of outbreaks in Hungary.

Enterobacteriaceae

This review summarises the changing epidemiology of resistance to cephalosporins and fluoroquinolones among the Enterobacteriaceae since the 1980s and its potential impact on prescribing choices now and in the immediate future. Whilst multiresistant Enterobacteriaceae are not a novel problem for high-risk hospital units, such as intensive care, the emergence of Escherichia coli co-expressing extended-spectrum beta-lactamases, such as CTX-M types, along with fluoroquinolone resistance in the community is starting to impact in situations where cephalosporins and ciprofloxacin were seen as reliable first-line choices. The reduction in effective options to treat these infections, particularly of the urinary tract and bacteraemia, is likely to result in increased prescribing of carbapenems, thus generating further selective pressure for carbapenemases and other mechanisms of carbapenem resistance in the future.

Widespread transfer of resistance genes between bacterial species in an intensive care unit: implications for hospital epidemiology

A transferable plasmid encoding SHV-12 extended-spectrum beta-lactamase, TEM-116, and aminoglycoside resistance was responsible for two sequential clonal outbreaks of Enterobacter cloacae and Acinetobacter baumannii bacteria. A similar plasmid was present among isolates of four different bacterial species. Recognition of plasmid transfer is crucial for control of outbreaks of multidrug-resistant nosocomial pathogens.

Prolonged outbreak of infection due to TEM-21-producing strains of Pseudomonas aeruginosa and enterobacteria in a nursing home

Over a 6-year period, 24 extended-spectrum beta-lactamase (ESBL)-producing isolates of Pseudomonas aeruginosa were collected from 18 patients living in a nursing home. These isolates had a delayed development of a red pigment and exhibited a similar antibiotype (resistance to all beta-lactams except for imipenem and to gentamicin, tobramycin, netilmicin, ciprofloxacin, and rifampin) associated with the production of the TEM-21 beta-lactamase and a type II 3'-N-aminoglycoside acetyltransferase [AAC(3)-II] enzyme. Surprisingly, serotyping showed that these isolates belonged to four successive serotypes (P2, P16, P1, and PME), although molecular typing by PCR methods and pulsed-field gel electrophoresis yielded identical or similar profiles. Moreover, in all isolates the bla(TEM-21) gene was part of a chromosomally located Tn801 transposon truncated by an IS6100 element inserted within the resolvase gene, and the aac(3)-II gene was adjacent to this structure. During the same period, 17 ESBL-producing isolates of enterobacteria were also collected from 10 of these patients. These isolates harbored a similar large plasmid that contained the bla(TEM-21) and the aac(3)-II genes and that conferred additional resistance to sulfonamides and chloramphenicol, as well as to kanamycin, tobramycin, netilmicin, and amikacin, conveyed by an AAC(6')-I enzyme. The bla(TEM-21) gene was part of the Tn801 transposon disrupted by IS4321. Thus, a single clone of P. aeruginosa that had undergone a progressive genetic drift associated with a change in serotype appeared to be responsible for an outbreak of nosocomial infections in a nursing home. This strain has probably acquired the bla(TEM-21)-encoding plasmid that was epidemic among the enterobacteria at the institution, followed by chromosomal integration and genomic reorganization.

Countrywide spread of community- and hospital-acquired extended-spectrum beta-lactamase (CTX-M-15)-producing Enterobacteriaceae in Lebanon

A prospective study was carried out to assess the extent of carriage of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae at both hospital and community levels in Lebanon. A total of 1,442 fecal samples were collected from hospital-based patients and 58 from health care workers of six Lebanese tertiary care general hospitals located in different areas of Lebanon between January and March 2003. A total of 382 fecal samples were also collected from healthy subjects between April and June 2003. The samples analysis led to the identification of 118 strains as ESBL producers based on the synergistic effects between clavulanate and selected beta-lactams (ceftazidime and cefotaxime). These strains were isolated from 72 subjects: 61 patients, 2 health care workers, and 9 healthy subjects. One representative strain per subject was selected, and a total of 72 nonduplicate ESBL producers, including a high majority of Escherichia coli (n = 56), Klebsiella pneumoniae (n = 9), Enterobacter cloacae (n = 6), and Citrobacter freundii (n = 1), were characterized. The molecular analysis revealed that the majority of the strains (83%) express CTX-M-15 ESBL (pI 8.6). SHV-5a ESBL (pI 8.2) was produced by 18% of the strains. DNA macrorestriction analysis of ESBL-producing E. coli presented 38 different genotypes, revealing the absence of clonal link among these strains. In addition to the fact that the present study highlights the emergence and the countrywide dissemination of CTX-M-15-producing E. coli in Lebanon, it represents the first report of an SHV-5a-producing C. freundii.

Survey of Enterobacteriaceae producing extended-spectrum beta-lactamases in a Slovak hospital: dominance of SHV-2a and characterization of TEM-132

Eighty-five extended-spectrum beta-lactamase-producing Enterobacteriaceae from a Slovak hospital have been studied. SHV-2a was predominant, but other variants have been detected, namely, SHV-5, SHV-12, TEM-12, TEM-15, and TEM-132, which differed from TEM-1 by amino acid substitutions R164H, E240K, and I173V and had kinetic properties similar to those of TEM-28.

Occurrence and regional distribution of SHV-type extended-spectrum beta-lactamases in Hungary

In order to determine the presence and geographical distribution of SHV-type extended-spectrum beta-lactamase genes among Enterobacteriaceae strains in Hungary, isolates from 25 microbiology laboratories throughout the country were collected between January 2002 and August 2003 and examined. Sequencing of the genes showed that SHV-5 and SHV-2a are the dominant SHV-types in extended-spectrum beta-lactamase-producing Enterobacteriaceae strains in this country. The SHV-2 gene, which is prevalent in many European countries, was not detected, but one isolate carried the SHV-12 gene. The results show that these genes are circulating among Enterobacteriaceae strains in Hungary and indicate that strict infection control measures are warranted in order to prevent their spread.

Evolution of TEM-type extended-spectrum beta-lactamases in clinical Enterobacteriaceae strains in Poland

Seventeen extended-spectrum beta-lactamase (ESBL)-producing isolates of the family Enterobacteriaceae recovered from 1998 to 2000 in hospitals of five different cities in Poland were analyzed. They expressed several TEM-type ESBLs, TEM-4, TEM-29, TEM-85, TEM-86, TEM-93, and TEM-94. TEM-85 (L21F, R164S, E240K, T265M), TEM-86 (L21F, R164S, A237T, E240K, T265M), TEM-93 (M182T, G238S, E240K), and TEM-94 (L21F, E104K, M182T, G238S, T265M) were identified for the first time. Including the enzymes described earlier, TEM-47, TEM-48, TEM-49, and TEM-68, the group of known ESBLs of the TEM family produced by enterobacteria in Polish hospitals has increased to 10 variants. Comparative sequence analysis of the genes coding for all these beta-lactamases revealed a view of their possible evolution, which, apart from the gradual acquisition of various mutations, could also have involved recombination events. Two different bla(TEM-1) gene alleles were precursors of the ESBL genes: bla(TEM-1A), which was the ancestor of bla(TEM-93), and bla(TEM-1F), from which all the remaining genes originated. The evolution of the bla(TEM-1F)-related genes most probably consisted of three major separate lineages, one of which, including bla(TEM-4), bla(TEM-47), bla(TEM-48), bla(TEM-49), bla(TEM-68), and bla(TEM-94), was highly structured itself and could have been initiated by the bla(TEM-25) gene, identified exclusively in France so far. Plasmid fingerprinting analysis revealed a high degree of diversity of plasmids carrying related bla(TEM) genes, which suggested either the intense diversification or transposition of bla(TEM) genes between different plasmids or some contribution of convergent evolution. The results of this study clearly demonstrate that the environment of Polish hospitals has been highly favorable for the rapid evolution of ESBLs.

Increased mortality associated with a clonal outbreak of ceftazidime-resistant Klebsiella pneumoniae: a case-control study

OBJECTIVES

To determine risk factors for ceftazidime-resistant Klebsiella pneumoniae infection and the effect of ceftazidime-resistant K. pneumoniae infection on mortality during an isolated outbreak.

DESIGN

Case-control investigation using clinical and molecular epidemiology and prospective analysis of infection control interventions.

SETTING

Surgical intensive care unit of a university-affiliated community hospital.

PATIENTS

Fourteen case-patients infected with ceftazidime-resistant K. pneumoniae and 14 control-patients.

RESULTS

Ten of 14 case-patients had identical strains by pulsed-field gel electrophoresis. Broad-spectrum antibiotic therapy before admission to the unit was strongly predictive of subsequent ceftazidime-resistant K. pneumoniae infection. In addition, patients with ceftazidime-resistant K. pneumoniae infection experienced increased mortality (odds ratio, 3.77).

CONCLUSIONS

Cephalosporin restriction has been shown to decrease the incidence of nosocomial ceftazidime-resistant K. pneumoniae. However, isolated clonal outbreaks may occur due to lapses in infection control practices. Reinstatement of strict handwashing, thorough environmental cleaning, and repeat education led to termination of the outbreak. A distinct correlation between ceftazidime-resistant K. pneumoniae infection and mortality supports the important influence of antibiotic resistance on the outcome of serious bacterial infections.

Extended-spectrum β-lactamase-conferring transferable resistance to different antimicrobial agents inEnterobacteriaceae isolated from bloodstream infections

Twenty (18.5%) out of 108 clinical isolates of the family Enterobacteriaceae responsible for bloodstream infection were extended-spectrum beta-lactamase (ESBL)-positive in two screening tests, the double disk synergy test and the Oxoid Combination Disk method. Eleven out of the 20 ESBL-positive isolates transferred oxyimino-beta-lactam resistance to E. coli K12 C600 recipient strain with a frequency of 10(-8) - 10(-1) per donor cell. PCR analysis revealed that the majority of the transconjugants (9 of 11) express CTX-M-type beta-lactamases. Donor strains and their transconjugants displayed susceptibility patterns typical of ESBL producers. They were resistant to oxyimino-beta-lactams but susceptible to clavulanic acid and carbapenems. Resistances to aminoglycosides, tetracycline and mercuric chloride were, in some cases, co-transferred with oxyimino-beta-lactam resistance, suggesting that various resistance determinants were carried by the same conjugative plasmids.

Characteristics, epidemiology and clinical importance of emerging strains of Gram-negative bacilli producing extended-spectrum beta-lactamases

Beta-lactam antimicrobial agents represent the most common treatment for bacterial infections and continue to be the leading cause of resistance to beta-lactam antibiotics among Gram-negative bacteria worldwide. The persistent exposure of bacterial strains to a multitude of beta-lactams has induced dynamic and continuous production and mutation of beta-lactamases in these bacteria, expanding their activity even against the newly developed beta-lactam antibiotics. These enzymes are known as extended-spectrum beta-lactamases (ESBLs). The majority of ESBLs are derived from the widespread broad-spectrum beta-lactamases TEM-1 and SHV-1. There are also new families of ESBLs, including the CTX-M and OXA-type enzymes as well as novel unrelated beta-lactamases. In recent years, there has been an increased incidence and prevalence of ESBLs. ESBLs are mainly found in strains of Escherichia coli and Klebsiella pneumoniae but have also been reported in other Enterobacteriaceae strains and Pseudomonas aeruginosa. Infections with ESBL-producing bacterial strains are encountered singly or in outbreaks, especially in critical care units in hospitals, resulting in increasing cost of treatment and prolonged hospital stays. Not only may nursing home patients be an important reservoir of ESBL-containing multiple antibiotic-resistant organisms, but ambulatory patients with chronic conditions may also harbor ESBL-producing organisms.

Molecular biology of extended-spectrum beta-lactamase-producing Enterobacteriaceae responsible for digestive tract colonization

Twenty-nine extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae strains (14 Klebsiella pneumoniae, 10 Escherichia coli and five Citrobacter diversus) isolated from April to July 1996 from faecal carriers in a surgical intensive care unit at the university hospital of Casablanca (Morocco) were studied. Plasmid content and DNA macrorestriction polymorphism determined by pulsed-field gel electrophoresis (PFGE) were used to compare the strains. Restriction profiles of total genomic DNAs cleaved by XbaI and compared by PFGE revealed nine, four and two clones in K. pneumoniae, E. coli and C. diversus, respectively. Plasmid profile analysis of ESBL-producing strains of K. pneumoniae showed that only seven of 14 isolates had a plasmid; four different plasmid profiles were observed. Three different plasmid profiles were observed in E. coli and two in C. diversus. Plasmids responsible for ESBL production could be transferred by conjugation to E. coli K(12) J53-2 from all E. coli isolates and from four of seven K. pneumoniae. No plasmid transfer could be obtained from C. diversus strains. Restriction enzyme digests of plasmids from transconjugants (four transconjugants of K. pneumoniae and five transconjugants of E. coli) showed different patterns. In the surgical intensive care unit where the survey was conducted, the dissemination of ESBLs was due to a mix of strain spread and strain diversity rather than to plasmid dissemination.

Molecular epidemiology of Serratia marcescens in two hospitals in Gdańsk, Poland, over a 5-year period

The history of the Serratia marcescens population in two hospitals in Danzig, Poland, over a 5-year period was analyzed in a study that combined MIC evaluation, typing by randomly amplified polymorphic DNA (RAPD) analysis and pulsed-field gel electrophoresis, and analysis of extended-spectrum beta-lactamases (ESBLs). We analyzed 354 isolates collected from 341 patients in two teaching hospitals in Danzig, Poland, from 1996 to 2000. The antimicrobial susceptibility profiles varied greatly, and for resistance to newer beta-lactams, probable AmpC cephalosporinase derepression and ESBL production occurred in about 23 and 19% of the isolates, respectively. RAPD typing, by which 69 types were discerned altogether, revealed a high degree of clonal diversity among the populations. However, the four most prevalent types were highly predominant, grouping approximately 71% of the isolates studied. These clones were observed in the two hospitals and were strong contributors to both outbreaks and the background of endemicity of the S. marcescens infections. Some of the strains that were not so widely spread (12 RAPD types; approximately 14% of the isolates) were responsible for several smaller outbreaks, and the remaining isolates represented unique RAPD types (53 types; approximately 15% of the isolates) and were probably sporadic introductions from other environments. ESBLs were identified in several different clones, and some of these had most likely already been introduced into the hospitals as ESBL producers, whereas the others acquired the ESBL-encoding genes from other enterobacterial strains in these environments. The CTX-M-3 enzyme, which is widely observed in Poland, was the most common ESBL type among the S. marcescens isolates, followed by TEM-47 and SHV-5. The complex epidemiology of ESBLs, especially in 1999 and 2000, must have arisen from the introduction of ESBL producers from other centers, their clonal dissemination, and the constant penetration of the S. marcescens populations with plasmids with ESBL genes. Multiple S. marcescens isolates were obtained from 11 patients, who probably represented both patients with recolonizations and reinfections and patients with recurrences of infections with the evolution of the strain's susceptibility.

Analysis of three outbreaks due to Klebsiella species in a neonatal intensive care unit

OBJECTIVE

To investigate the clinical, microbiological, and epidemiologic features of three outbreaks caused by Klesiella during 3 years.

SETTING

Neonatal intensive care unit of a university hospital.

PATIENTS

Thirty affected neonates.

METHODS

Data were collected through chart reviews and conversations with physicians. Screening samples were obtained from the staff, the neonates, and the environment. Antibiogram typing and arbitrarily primed polymerase chain reaction-based fingerprinting were used to type the strains.

RESULTS

The first outbreak had 13 K. pneumoniae strains isolated. The second outbreak had 10 K. oxytoca strains isolated. The third outbreak had 20 K. pneumoniae strains isolated. More than half of the patients had low birth weights, were premature, and underwent mechanical ventilation and intravenous catheterization. Approximately three-fourths of the patients died. The isolates tested were completely susceptible to meropenem, cefoxitin, and ciprofloxacin and were resistant to cephalothin. More than half of these strains were resistant to many beta-lactam antibiotics, amikacin, and trimethoprim/sulfamethoxazole. Typing procedures yielded 3 antibiotypes and 3 genotypes among the isolates of the first outbreak, 3 antibiotypes with 1 subtype and 2 genotypes with 1 subtype in the second outbreak, and 2 antibiotypes and 2 genotypes in the third outbreak.

CONCLUSIONS

Klebsiella outbreaks mainly affected premature neonates with intravenous catheters, mechanical ventilation, or both. The high mortality rate (76.7%) was notable. Resistance to multiple antibiotics, but mainly to broad-spectrum beta-lactam antibiotics, was observed, particularly in K. pneumoniae isolates. Molecular typing indicated that the three outbreaks were not related to one other.

Molecular epidemiology of an outbreak of multiresistant Klebsiella pneumoniae in a Tunisian neonatal ward

During the first quarter of 1996, a major outbreak of clinical infection caused by multiresistant Klebsiella pneumoniae (MRKP) occurred in the neonatal ward of the 'Maternité Wassila Bourguiba' in Tunis, Tunisia. In total, 32 isolates of MRKP, comprising 23 clinical isolates and nine surveillance isolates, were recovered during this period and analysed for epidemiological relatedness. The isolates were compared with 17 other isolates of MRKP that were recovered during 1995. Macrorestriction profiles of total genomic DNA following XbaI restriction endonuclease digestion were analysed by PFGE; this typing classified 56% of the 32 isolates recovered in 1996 into two major clusters. Cluster A included ten isolates from 1996 and three isolates recovered in 1995, whereas cluster B included eight isolates from the outbreak of 1996. The remaining isolates were genetically unrelated to those of clusters A and B; they constituted sporadic strains. The two major clusters were also evident using other molecular typing methods, such as random amplification of polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus (ERIC)-PCR, where isolates of clusters A and B could be identified on the basis of their discriminative patterns. This investigation showed the predominance of two epidemic strains, and illustrated the ease with which MRKP strains can disseminate and persist within a single ward.

Genes encoding TEM-4, SHV-2, and CTX-M-10 extended-spectrum beta-lactamases are carried by multiple Klebsiella pneumoniae clones in a single hospital (Madrid, 1989 to 2000)

Over a 12-year period (1989 to 2000), 159 Klebsiella pneumoniae isolates harboring extended-spectrum beta-lactamases (ESBLs) (4.8% of the total number of K. pneumoniae isolates obtained) were recovered from 58 patients, who were mainly hospitalized in intensive care and surgery units. For 62 representative isolates from 58 patients, 31 clonal types harboring TEM-4 (n = 5), SHV-2 (n = 7), SHV2a (n = 4), SHV-5 (n = 1), CTX-M-10 (n = 13), or CTX-M-9 (n = 1) beta-lactamases were identified by pulsed-field gel electrophoresis. This is the first report to document the presence of the CTX-M-10 or the CTX-M-9 beta-lactamase in K. pneumoniae. These beta-lactamases were previously identified in Escherichia coli isolates from Spain. Only two of five K. pneumoniae TEM-4 clones caused more than a single case of infection, with one of them spreading for 9 months. A single plasmid was detected among these TEM-4 clones. Only two of seven K. pneumoniae clones containing SHV-2 and three of four strains harboring SHV-2a were detected in more than one case of infection. Plasmids encoding SHV-2 or SHV-2a were unrelated. Four of 13 K. pneumoniae CTX-M-10 clones were found in more than one patient, with two of them recovered 2 and 5 years apart. As in the case of the SHV-2 isolates, we were unable to document a common transmissible genetic element that could explain the polyclonal structure of our isolates. Nevertheless, the spread of a single gene may be suggested by the presence of a conserved set of noncoding polymorphisms in the sequences. Most ESBL-producing K. pneumoniae clones were ephemeral, being poorly selected and maintained in the hospital setting, but the genes encoding ESBL persisted successfully over the years that the strains were recovered, probably as a minority gene population in the hospital metagenome.

Evolution and epidemiology of extended-spectrum beta-lactamases (ESBLs) and ESBL-producing microorganisms

The rapid and irrepressible increase in antimicrobial resistance of pathogenic bacteria that has been observed over the last two decades is widely accepted to be one of the major problems of human medicine today. Several aspects of this situation are especially worrying. There are resistance mechanisms that eliminate the use of last-choice antibiotics in the treatment of various kinds of infection. Many resistance mechanisms that emerge and spread in bacterial populations are those of wide activity spectra, which compromise all or a majority of drugs belonging to a given therapeutic group. Some mechanisms of great clinical importance require specific detection procedures, as they may not confer clear resistance in vitro on the basis of the interpretive criteria used in standard susceptibility testing. Finally, multiple mechanisms affecting the same and/or different groups of antimicrobials coexist and are even co-selected in more and more strains of pathogenic bacteria. The variety of beta-lactamases with wide spectra of substrate specificity illustrates very well all the phenomena mentioned above. Being able to hydrolyze the majority of beta-lactams that are currently in use, together they constitute the most important resistance mechanism of Gram-negative rods. Three major groups of these enzymes are usually distinguished, class C cephalosporinases (AmpC), extended-spectrum beta-lactamases (ESBLs) and different types of beta-lactamases with carbapenemase activity, of which the so-called class B metallo-beta-lactamases (MBLs) are of the greatest concern. This review is focused on various aspects of the evolution and epidemiology of ESBLs; it does not cover the problems of ESBL detection and clinical relevance of infections caused by ESBL-producing organisms.

Hospital infection control in Poland

During the last 10 years, as in other areas of the public sector in Poland, the healthcare system has undergone important changes presenting a challenge for medical staff and healthcare managers alike. Since 1997, the Polish Government has undertaken important healthcare reforms. New regulations have introduced decentralization of management and a financing system for hospitals. These changes have provided favourable conditions in which to implement an infection control system for hospitals. The most important recent initiatives are training courses and workshops for hospital staff organized in co-operation with microbiologists and epidemiologists as well as preparation of recommendations and guidelines for hospitals. Several non-governmental organizations have been set up to improve hospital hygiene, infection control and monitoring of antimicrobial resistance.

Extended-spectrum beta-lactamases in the 21st century: characterization, epidemiology, and detection of this important resistance threat

Beta-lactamases continue to be the leading cause of resistance to beta-lactam antibiotics among gram-negative bacteria. In recent years there has been an increased incidence and prevalence of extended-spectrum beta-lactamases (ESBLs), enzymes that hydrolyze and cause resistance to oxyimino-cephalosporins and aztreonam. The majority of ESBLs are derived from the widespread broad-spectrum beta-lactamases TEM-1 and SHV-1. There are also new families of ESBLs, including the CTX-M and OXA-type enzymes as well as novel, unrelated beta-lactamases. Several different methods for the detection of ESBLs in clinical isolates have been suggested. While each of the tests has merit, none of the tests is able to detect all of the ESBLs encountered. ESBLs have become widespread throughout the world and are now found in a significant percentage of Escherichia coli and Klebsiella pneumoniae strains in certain countries. They have also been found in other Enterobacteriaceae strains and Pseudomonas aeruginosa. Strains expressing these beta-lactamases will present a host of therapeutic challenges as we head into the 21st century.

Outbreak of infection with extended-spectrum beta-lactamase-producing Klebsiella pneumoniae in a Mexican hospital

Thirty-one strains of Klebsiella pneumoniae (including 10 duplicates) from 21 septicemic pediatric patients (age, <2 months) were studied during a 4-month period (June to October 1996) in which the fatality rate was 62% (13 of 21). These isolates identified by the API 20E system yielded the same biotype. Pulsed-field gel electrophoresis experiments revealed the same clone in 31 strains. The isolates were multidrug-resistant but were still susceptible to ciprofloxacin, imipenem, and cefoxitin. A 135-kb plasmid was harbored in all of the isolates. No transconjugants were obtained that were resistant to ampicillin, cefotaxime, tetracycline, or gentamicin. Isoelectric focusing for beta-lactamases was performed on all strains, and three bands with pIs of 5.4, 7.6, and 8.2 were obtained. Of these, the pI 8.2 beta-lactamase had an extended-spectrum beta-lactamase phenotype. PCR amplification of both TEM- and SHV-type genes was obtained. The sequence analysis of the SHV PCR product indicated a mutation corresponding to the SHV-5 beta-lactamase.

Coexistence of SHV-4- and TEM-24-producing Enterobacter aerogenes strains before a large outbreak of TEM-24-producing strains in a French hospital

In 1996, a monitoring program was initiated at the teaching hospital of Amiens, France, and carried out for 3 years. All extended-spectrum beta-lactamase (ESBL)-producing Enterobacter aerogenes isolates recovered from clinical specimens were collected for investigation of their epidemiological relatedness by pulsed-field gel electrophoresis and enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) and determination of the type of ESBL harbored by isoelectric focusing and DNA sequencing. Molecular typing revealed the endemic coexistence, during the first 2 years, of two clones expressing, respectively, SHV-4 and TEM-24 ESBLs, while an outbreak of the TEM-24-producing strain raged in the hospital during the third year, causing the infection or colonization of 165 patients. Furthermore, this strain was identified as the prevalent clone responsible for outbreaks in many French hospitals since 1996. This study shows that TEM-24-producing E. aerogenes is an epidemic clone that is well established in the hospital's ecology and able to spread throughout wards. The management of the outbreak at the teaching hospital of Amiens, which included the reinforcement of infection control measures, failed to obtain complete eradication of the clone, which has become an endemic pathogen.

Outbreak of nosocomial infections due to extended-spectrum beta-lactamase-producing strains of enteric group 137, a new member of the family Enterobacteriaceae closely related to Citrobacter farmeri and Citrobacter amalonaticus

A member of the Enterobacteriaceae initially identified as Kluyvera cryocrescens by the MicroScan Gram-Negative Combo 13 panel caused an outbreak of nosocomial infections in four patients (pneumonia, n = 2; urinary tract infection, n = 1; wound infection, n = 1) and urinary tract colonization in one patient. When the strains were tested by the Enteric Reference Laboratory of the Centers for Disease Control and Prevention, biochemical results were most compatible with Yersinia intermedia, Kluyvera cryocrescens, and Citrobacter farmeri but identification scores were low and test results were discrepant. However, when the biochemical test profile was placed in the computer database as a new organism, all strains were identified as the organism with high identification scores (0. 999968 to 0.999997) and no discrepant test results. By 16S rRNA sequence analysis the organism clustered most closely with, but was distinct from, Citrobacter farmeri and Citrobacter amalonaticus. Based on its unique biochemical profile and rRNA sequence, this organism is designated Enteric Group 137. Restriction endonuclease analysis and taxonomic antibiograms of strains causing the outbreak demonstrated a single clone of Enteric Group 137, and antibiotic susceptibility testing revealed the presence of extended-spectrum beta-lactamase (ESBL) resistance. Enteric Group 137 appears to be a new opportunistic pathogen that can serve as a source of ESBL resistance in the hospital.

Multiple-antibiotic resistance mediated by structurally related IncL/M plasmids carrying an extended-spectrum beta-lactamase gene and a class 1 integron

A conjugative IncL/M plasmid (pSEM) conferring resistance to gentamicin, amikacin, kanamycin, sulfonamides, and expanded-spectrum cephalosporins was found in pathogenic strains of Salmonella enterica serotype Typhimurium. Resistance to aminoglycosides was encoded by a sul1-type class 1 integron (In-t3). An extended-spectrum beta-lactamase gene, bla(SHV-5), was identified 3. 5 kb downstream of the integrase (intI1) gene of In-t3. Nucleotide sequence analysis of the 5.3-kb bla(SHV-5)-In-t3 region of pSEM highlighted striking similarities with IncL/M plasmids isolated from nosocomial gram-negative pathogens, conferring resistance to expanded-spectrum cephalosporins and aminoglycosides.

Molecular investigation of two clusters of hospital-acquired bacteraemia caused by multi-resistant Klebsiella pneumoniae using pulsed-field gel electrophoresis and in frequent restriction site PCR. Infection Control Group

Two molecular typing methods, DNA macrorestriction analysis with XbaI resolved by pulsed-field gel electrophoresis (PFGE) and infrequent restriction site PCR (IRS-PCR) assay with adapters designed for XbaI and HhaI restriction sites, were used to investigate two clusters of hospital-acquired bacteraemia associated with multi-resistant Klebsiella pneumoniae which occurred in a paediatric intensive care unit (PICU). A total of 56 K. pneumoniae isolates were analysed. These included 10 bacteraemic isolates from eight patients, 26 isolates obtained during an epidemiological survey, and 20 epidemiologically non-related isolates incorporated as controls. One major pattern was demonstrated in 22 of the 56 isolates analysed. These included nine of the 10 bacteraemic isolates, a single rectal isolate, two hand culture isolates and 10 sink isolates. All of these 22 isolates illustrated identical antibiograms, whilst the other 34 isolates shared six antibiograms and 31 unique patterns by either PFGE or IRS-PCR assay. The two clusters of bacteraemia appeared to be outbreaks induced by the same strain of K. pneumoniae which may have utilized sinks as reservoirs and been transmitted through the hands of medical personnel to patients. IRS-PCR demonstrates concordant results with PFGE analysis in studying the genetic relationships among K. pneumoniae isolates, and serves as an excellent epidemiological tool for this bacterium.

A novel complex mutant beta-lactamase, TEM-68, identified in a Klebsiella pneumoniae isolate from an outbreak of extended-spectrum beta-lactamase-producing Klebsiellae

Twenty-two Klebsiella pneumoniae and two K. oxytoca extended-spectrum beta-lactamase (ESBL)-producing isolates were collected in 1996 from patients in two pediatric wards of the University Hospital in Wrocław, Poland. Molecular typing has revealed that the K. pneumoniae isolates represented four different epidemic strains. Three kinds of enzymes with ESBL activity (pI values of 5.7, 6.0, and 8.2) were identified. The pI 6.0 beta-lactamases belonged to the TEM family, and sequencing of the bla(TEM) genes amplified from representative isolates revealed that these enzymes were TEM-47, previously identified in K. pneumoniae isolates from pediatric hospitals in Lódz and Warsaw. One of the TEM-47-producing strains from Wrocław was very closely related to the isolates from the other cities, and this indicated countrywide spread of the epidemic strain. The pI 5.7 beta-lactamase was produced by a single K. pneumoniae isolate for which, apart from oxyimino-beta-lactams, the MICs of beta-lactam-inhibitor combinations were also remarkably high. Sequencing revealed that this was a novel TEM beta-lactamase variant, TEM-68, specified by the following combination of mutations: Gly238Ser, Glu240Lys, Thr265Met, and Arg275Leu. The new enzyme has most probably evolved from TEM-47 by acquiring the single substitution of Arg275, which before was identified only twice in enzymes with inhibitor resistance (IR) activity. TEM-68 was shown to be a novel complex mutant TEM beta-lactamase (CMT-2) which combines strong ESBL activity with relatively weak IR activity and, when expressed in K. pneumoniae, is able to confer high-level resistance to a wide variety of beta-lactams, including inhibitor combinations. This data confirms the role of the Arg275Leu mutation in determining IR activity and documents the first isolation of K. pneumoniae producing the complex mutant enzyme.

Screening and confirmatory testing for extended spectrum beta-lactamases (ESBL) in Escherichia coli, Klebsiella pneumoniae, and Klebsiella oxytoca clinical isolates

Escherichia coli and Klebsiella spp. were screened for ESBL based on routine susceptibility testing results. Isolates with intermediate or resistant susceptibilities for extended spectrum cephalosporins or aztreonam were reported as probable ESBL producers. By using the NCCLS proposed ESBL confirmatory method, we tested 61 screen-positive isolates from 42 patients, 30 randomly selected susceptible isolates, and 12 isolates with previously characterized beta-lactamases. Ceftazidime contributed to 97% of screen-positive isolates, whereas aztreonam added a single patient isolate. An ESBL was confirmed in 86% of K. pneumoniae, 100% of K. oxytoca, and 20% of E. coli screen-positive single patient isolates. None of the susceptible isolates were shown to produce ESBL. Based on these findings a comment regarding the presence of ESBL seems sufficient for Klebsiella spp. but confirmatory testing is indicated for E. coli. 0.25 microg/mL was used to indicate the presence of ESBL, the specificity of the assay increased to 100%. The NCCLS ESBL phenotypic confirmatory method was reproducible and accurate enough to be used in the clinical laboratory.

Bacteremia due to extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in a pediatric oncology ward: clinical features and identification of different plasmids carrying both SHV-5 and TEM-1 genes

Thirteen patients who had 16 episodes of bacteremia were observed between 1993 and 1997 in a pediatric oncology ward with a high background isolation rate of cefotaxime- or aztreonam-resistant gram-negative bacteria. Four blood isolates were Escherichia coli and 12 were Klebsiella pneumoniae, and these isolates harbored extended-spectrum beta-lactamases (ESBLs). All episodes of bacteremia were nosocomial, all except one of the episodes occurred in neutropenic patients, and all patients were treated with piperacillin or ceftazidime with amikacin and cefazolin prior to the onset of bacteremia. Nine of 13 patients were receiving extended-spectrum beta-lactam treatment when the bacteremias caused by ESBL producers occurred. Molecular studies revealed that four K. pneumoniae SHV-2-producing isolates from 1994 were of the same clone. Other ESBL producers, including six that carried both TEM-1 and SHV-5, five that carried SHV-5, and one that carried SHV-2 alone, were unrelated. In conclusion, SHV-5 was present in 11 of the 16 isolates and coexisted with TEM-1 in 6 isolates. Acquisition of resistance genes probably occurred under antibiotic selection pressure. This study highlights the importance of routine checks for and detection of ESBL producers. Effective therapy against ESBL producers should be considered early for children who have malignancies and neutropenia and who are septic, despite treatment with a regimen that includes an extended-spectrum beta-lactam, in a clinical setting of an increased incidence of ESBL-producing bacteria.

Strategies for study of the role of cycling on antimicrobial use and resistance

Resistant bacteria usually are seen first in the intensive care unit and other acute-care areas. Thus, strategies to control these organisms often are first tested in these healthcare settings. Frequent among these strategies are attempts to improve antimicrobial use. One proposed method to decrease resistance in special settings like the intensive care unit is the cycling or rotation of antimicrobials. This intervention must be evaluated in the context of other concomitant attempts to improve antimicrobial usage and must take into account other factors influencing resistance. Until such studies are done, the value of cycling and other efforts to limit prescribers' choices of drugs in endemic settings will be unclear. Studies to evaluate cycling will have to be of large scale to produce useful data. It is unlikely that many hospitals or healthcare systems will have sufficient resources on their own to develop studies of sufficient power to be applied widely. Thus, cooperative studies to provide data on this important issue should be an international priority.

Concurrent outbreaks of extended-spectrum beta-lactamase-producing organisms of the family Enterobacteriaceae in a Warsaw hospital

The increasing use of broader-spectrum cephalosporins in the first half of the 1990s has become one of the major factors responsible for the high rate of selection of extended-spectrum beta-lactamase (ESBL)-producing microorganisms in Polish hospitals. Thirty-five isolates of seven different species of the family Enterobacteriaceae were identified as ESBL producers, over a 4 month period, in one of Warsaw's hospitals between the end of 1996 and the beginning of 1997. Sixteen per cent of all Klebsiella pneumoniae isolates, 16% of Citrobacter freundii isolates and 32% of Serratia marcescens isolates collected by the hospital microbiology laboratory at that time were expressing these enzymes. The majority of these (27 isolates) were found to express CTX-M-type ESBLs (pI 8.4). This outbreak was due to both plasmid dissemination among unrelated strains and clonal spread of some strains in several wards of the hospital. The remaining isolates produced ESBLs (pI 8.2) belonging to the SHV family of beta-lactamases and demonstrated a high degree of genetic diversity.