Detection of extended broad-spectrum beta-lactamases in Enterobacteriaceae in four French hospitals

Patterns of Antibiotic Resistance in Enterobacteriaceae Isolates from Broiler Chicken in the West Region of Cameroon: A Cross-Sectional Study

Background. The emergence of multidrug-resistant food-borne pathogens of animal origin including Enterobacteriaceae is a growing concern. Identifying and monitoring resistance in isolates from human-related environments are of clinical and epidemiological significance in containing antimicrobial resistance. This study aimed to contribute towards the fight against antibiotic resistance and ameliorate the management/treatment of Enterobacteriaceae-linked diseases in Cameroon. Methods. Cloacal swabs from healthy broilers were enriched in buffered-peptone-water and cultured on EMB agar. Antibiotic susceptibility was tested on Mueller-Hinton-Agar by disc diffusion. Plasmid-borne genes for extended-spectrum beta lactamase (ESBL) and resistance to Quinolones (PMQR) and Aminoglycosides were detected by standard endpoint polymerase chain reaction (PCR). Results. A total of 394 isolates were identified belonging to 12 Enterobacteriaceae genera, the most prevalent were Escherichia coli (81/394 = 20.56%), Salmonella spp (74/394 = 18.78%), and Klebsiella spp (39/394 = 9.90%) respectively. Overall, 84/394 (21.32%) were ESBL producers, 164/394 (41.62%) were resistant to quinolones, 66/394 (16.75%) resistant to aminoglycosides with 44.0% (173/394) expressing MDR phenotype. Poor hygiene practice (OR 2.55, 95% CI: 1.67, 3.89, $p=0.001$ ) and rearing for >45 days, (OR = 7.98, 95% CI: 5.05, 12.6, $p=0.001$ ) were associated with increased carriage of MDR. Plasmid-borne resistance genes were detected in 76/84 (90.48%) of ESBL-producing isolates, 151/164 (92.07%) quinolone resistant isolates and 59/66 (89.39%) aminoglycoside resistant isolates with co-occurrence of two or more genes per isolate in 58/84 (69.05%) of ESBLs, 132/164 (80.49%) of quinolone resistant isolates and 28/66 (42.42%) of aminoglycoside resistant isolates. Conclusion. This study found high carriage and widespread distribution of Enterobacteriaceae with ESBL and MDR in broiler chicken in the West Region of Cameroon. Most PMQR genes in bacteria were found at levels higher than is seen elsewhere, representing a risk in the wider human community.

Review of phenotypic assays for detection of extended-spectrum β-lactamases and carbapenemases: a microbiology laboratory bench guide

Background

Infections caused by gram-negative antibiotic-resistant bacteria continue to increase. Despite recommendations by the Clinical Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) with regards to detection of antibiotic degrading enzymes secreted by these bacteria, the true prevalence of extended-spectrum β-lactamase (ESBL) and carbapenemase producers remains a difficult task to resolve. Describing of previously designed phenotypic detection assays for ESBLs and carbapenemases in a single document avails a summary that allows for multiple testing which increases the sensitivity and specificity of detection.

Methods and aims

This review, therefore, defined and classified ESBLs and carbapenemases, and also briefly described how the several previously designed phenotypic detection assays for the same should be performed.

Conclusion

Extended-spectrum β-lactamase and carbapenemase detection assays, once performed correctly, can precisely discriminate between bacteria producing these enzymes and those with other mechanisms of resistance to β-lactam antibiotics.

OXA-1 β-lactamase and non-susceptibility to penicillin/β-lactamase inhibitor combinations among ESBL-producing Escherichia coli

Background

ESBL-producing Escherichia coli have expanded globally since the turn of the century and present a major public health issue. Their in vitro susceptibility to penicillin/inhibitor combinations is variable, and clinical use of these combinations against ESBL producers remains controversial. We hypothesized that this variability related to co-production of OXA-1 penicillinase.

Methods

During a national study we collected 293 ESBL-producing E. coli from bacteraemias, determined MICs by BSAC agar dilution, and undertook genomic sequencing with Illumina methodology.

Results

The collection was dominated by ST131 (n = 188 isolates, 64.2%) and blaCTX-M-15 (present in 229 isolates, 78.2%); over half the isolates (159/293, 54.3%) were ST131 with blaCTX-M-15. blaOXA-1 was found in 149 ESBL producers (50.9%) and blaTEM-1/191 in 137 (46.8%). Irrespective of whether all isolates were considered, or ST131 alone, there were strong associations (P < 0.001) between co-carriage of blaOXA-1 and reduced susceptibility to penicillin/inhibitor combinations, whereas there was no significant association with co-carriage of blaTEM-1/191. For piperacillin/tazobactam the modal MIC rose from 2 mg/L in the absence of blaOXA-1 to 8 or 16 mg/L in its presence; for co-amoxiclav the shift was smaller, from 4 or 8 to 16 mg/L, but crossed the breakpoint. blaOXA-1 was strongly associated with co-carriage also of aac(6')-Ib-cr, which compromises amikacin and tobramycin.

Conclusions

Co-carriage of OXA-1, a penicillinase with weak affinity for inhibitors, is a major correlate of resistance to piperacillin/tazobactam and co-amoxiclav in E. coli and is commonly associated with co-carriage of aac(6')-Ib-cr, which narrows aminoglycoside options.

Interspecies plasmid transfer appears rare in sequential infections with extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae

From a cohort of 1836 Swedish patients infected with ESBL-producing Enterobacteriaceae (EPE) during 2004-2014, 513 patients with recurrent EPE infection were identified. Only in 14 of the 513 patients was a change of species (ESBL-E. coli to ESBL-K. pneumoniae or vice versa) found between the index and subsequent infection. Eleven sequential urine isolates from 5 of the 14 patients were available for further analysis of possible transfer of ESBL-carrying plasmids. The plasmid content was studied using optical DNA mapping (ODM), PCR-based replicon typing, and ESBL gene sequencing. ODM allowed us to directly compare whole plasmids between isolates and found similar ESBL-carrying plasmids in 3 out of the 5 patients. The ODM results and the rarity in shift of species between ESBL-E. coli and ESBL-K. pneumoniae imply that in recurrent EPE infections interspecies plasmid transfer is uncommon.

Rapid Tracing of Resistance Plasmids in a Nosocomial Outbreak Using Optical DNA Mapping

Resistance to life-saving antibiotics increases rapidly worldwide, and multiresistant bacteria have become a global threat to human health. Presently, the most serious threat is the increasing spread of Enterobacteriaceae carrying genes coding for extended spectrum β-lactamases (ESBL) and carbapenemases on highly mobile plasmids. We here demonstrate how optical DNA maps of single plasmids can be used as fingerprints to trace plasmids, for example, during resistance outbreaks. We use the assay to demonstrate a potential transmission route of an ESBL-carrying plasmid between bacterial strains/species and between patients, during a polyclonal outbreak at a neonatal ward at Sahlgrenska University Hospital (Gothenburg, Sweden). Our results demonstrate that optical DNA mapping is an easy and rapid method for detecting the spread of plasmids mediating resistance. With the increasing prevalence of multiresistant bacteria, diagnostic tools that can aid in solving ongoing routes of transmission, in particular in hospital settings, will be of paramount importance.

A randomized open label study of 'imipenem vs. cefepime' in spontaneous bacterial peritonitis

BACKGROUND & AIMS

Spontaneous bacterial peritonitis (SBP), in the presence of bacterial resistance or failure of third generation cephalosporins (3rd GC) has poor outcome. Empirical antibiotic(s) options are limited in these scenarios.

METHODS

Consecutive cirrhotics with SBP because of hospital acquired SBP (>48 h of admission), microbial resistance or non-response (no resolution of SBP at 48 h) were randomized to Cefepime (n = 88) or Imipenem (n = 87) plus standard medical therapy. We assessed for 'response at 48 h' (reduction in ascitic fluid absolute neutrophil count (ANC) by >25% at 48 h), resolution of SBP (<250 cu/mm ANC at day 5) and their clinical outcome.

RESULTS

Of 957 paracentesis in 1200 hospitalized cirrhotics, 253 (26.4%) had SBP and 175 (69.6%) were randomized. Baseline parameters were comparable in two groups. Response at 48 h (58.6% vs. 51.7%; P = 0.4) and resolution of SBP in those with response at 48 h were comparable with no difference in mortality at week 2, month 1 and 3. Patients with 'No response at 48 h' had higher mortality compared with responders (73.8% vs. 25%; P < 0.001). Resolution of SBP was associated with 'response at 48 h' and septic shock, latter being main pre-terminal event. AKI at enrolment [Hazard ratio (HR), 2.6], pneumonia [HR, 2.9], septic shock [HR, 2.2] and response at 48 h [HR, 4.6] predicted poor outcome.

CONCLUSIONS

In hospitalized cirrhotics with SBP and risk factors for treatment failure, cefepime showed comparable efficacy and survival to imipenem. Non-response to therapy at 48 h is a reliable predictor of treatment failure and mortality. Antibiotic combinations and novel options are needed for these patients.

Antimicrobial resistance of bacterial enteropathogens isolated from stools in Madagascar

Background

Diarrheal diseases are a major public health problem in developing countries, and are one of the main causes of hospital admissions in Madagascar. The Pasteur Institute of Madagascar undertook a study to determine the prevalence and the pathogenicity of bacterial, viral and protozoal enteropathogens in diarrheal and non-diarrheal stools of children aged less than 5 years in Madagascar. We present here the results of the analysis of antimicrobial susceptibility of the bacteria isolated during this study.

Methods

The study was conducted in the community setting in 14 districts of Madagascar from October 2008 to May 2009. Conventional methods and PCR were used to identify the bacteria; antimicrobial susceptibility was determined using an agar diffusion method for enterobacteriaceae and MICs were measured by an agar dilution method for Campylobacter sp. In addition to the strains isolated during this study, Salmonella sp and Shigella sp isolated at the Pasteur Institute of Madagascar from 2005 to 2009 were included in the analysis to increase the power of the study.

Results

Twenty-nine strains of Salmonella sp, 35 strains of Shigella sp, 195 strains of diarrheagenic E. coli, 203 strains of C. jejuni and 71 strains of C. coli isolated in the community setting were tested for antibiotic resistance. Fifty-five strains of Salmonella sp and 129 strains of Shigella sp isolated from patients referred to the Pasteur Institute of Madagascar were also included in the study. Many E. coli and Shigella isolates (around 80%) but fewer Salmonella isolates were resistant to ampicillin and trimethoprim/sulfamethoxazole. A small proportion of strains of each species were resistant to ciprofloxacin and only 3% of E. coli strains presented a resistance to third generation cephalosporins due to the production of extended-spectrum beta-lactamases. The resistance of Campylobacter sp to ampicillin was the most prevalent, whereas less than 5% of isolates were resistant to each of the other antibiotics.

Conclusion

The highest prevalence of antimicrobial resistance was to ampicillin and trimethoprim/sulfamethoxazole. Antibiotic treatment is not recommended for children with diarrhea in Madagascar and the emphasis should be placed on oral rehydration.

Sub-typing of extended-spectrum-β-lactamase-producing isolates from a nosocomial outbreak: application of a 10-loci generic Escherichia coli multi-locus variable number tandem repeat analysis

Extended-spectrum β-lactamase producing Escherichia coli (ESBL-E. coli) were isolated from infants hospitalized in a neonatal, post-surgery ward during a four-month-long nosocomial outbreak and six-month follow-up period. A multi-locus variable number tandem repeat analysis (MLVA), using 10 loci (GECM-10), for ‘generic’ (i.e., non-STEC) E. coli was applied for sub-species-level (i.e., sub-typing) delineation and characterization of the bacterial isolates. Ten distinct GECM-10 types were detected among 50 isolates, correlating with the types defined by pulsed-field gel electrophoresis (PFGE), which is recognized to be the ‘gold-standard’ method for clinical epidemiological analyses. Multi-locus sequence typing (MLST), multiplex PCR genotyping of bla_CTX-M, bla_TEM, bla_OXA and bla_SHV genes and antibiotic resistance profiling, as well as a PCR assay specific for detecting isolates of the pandemic O25b-ST131 strain, further characterized the outbreak isolates. Two clusters of isolates with distinct GECM-10 types (G06-04 and G07-02), corresponding to two major PFGE types and the MLST-based sequence types (STs) 131 and 1444, respectively, were confirmed to be responsible for the outbreak. The application of GECM-10 sub-typing provided reliable, rapid and cost-effective epidemiological characterizations of the ESBL-producing isolates from a nosocomial outbreak that correlated with and may be used to replace the laborious PFGE protocol for analyzing generic E. coli.

Polymorphonuclear counts in ascitic fluid and microorganisms producing spontaneous bacterial peritonitis: an under-recognized relationship

BACKGROUND AND AIMS. In cirrhotic patients with spontaneous bacterial peritonitis (SBP) higher polymorphonuclear (PMN) count in ascitic fluid have been reported in infections caused by Gram-negative bacilli (GNB) as opposed to Gram-positive cocci (GPC). However, the influence of other associated factors on the PMN count, such as the specific microorganism causing the episode of SBP, has not been well established. METHODS. Retrospective observational study of 194 episodes of positive ascitic and/or blood culture SBP in 159 patients with liver cirrhosis (2001-2009). Parameters associated with PMN count in ascitic fluid at diagnosis were evaluated. RESULTS. The multivariate analysis (model 1) showed that a virulent etiology of the infection [coefficient 3.941 (95% confidence interval (95 CI): 0.421-7.461)] and the model for end-stage liver disease (MELD) score [coefficient 0.196 (95 CI: 0.007-0.384)] were positively associated with the PMN count in ascites, while a nosocomial acquisition was inversely associated [coefficient -3.546 (95 CI: -6.855 - -0.238)]. A nonsignificant trend toward higher PMN count was found in GNB versus GPC, but there were differences between groups of microorganisms: pyogenic streptococci [median (p25-p75): 3211 (1615-8004)], Enterobacteriaceae [2958 (917-7690)], Vibrionaceae [9215 (375-17280)], nonfermenting GNB [1384 (565-3865)], viridans group streptococci [1044 (503-2354)] and enterococci [1050 (476-4655)](p = 0.005). No clear cut-offs of ascitic PMN count predicting a particular etiology could be calculated out of these data. CONCLUSIONS. In cirrhotic patients with SBP, the causing microorganism, the place of acquisition of the infection and the host liver condition were the main factors determining PMN count in ascitic fluid. Third-generation cephalosporin resistance was associated with low PMN count probably because this group included bacteria with inherent low virulence.

Risk factors for resistance to ceftriaxone and its impact on mortality in community, healthcare and nosocomial spontaneous bacterial peritonitis

BACKGROUND & AIMS

The recent emergence of third-generation cephalosporin resistance in spontaneous bacterial peritonitis is of great concern, although neither the risk factors for resistance nor its real impact on mortality have been well defined.

METHODS

We conducted a retrospective study of all spontaneous bacterial peritonitis episodes with positive blood and/or ascitic culture at our center (2001-2009). Episodes were classified according to the place of acquisition: community, healthcare system, or nosocomial.

RESULTS

Two hundred and forty-six episodes were analyzed in 200 patients (150 males, 57.3 years): 34.6% community-acquired, 38.6% healthcare system-acquired, and 26.8% nosocomially-acquired. Third-generation cephalosporin resistance occurred in 21.5% (7.1% community-acquired, 21.1% healthcare system-acquired, 40.9% nosocomially-acquired). These resistant cases were categorized as extended-spectrum β-lactamase-producing Gram-negative bacilli, other resistant Gram-negative bacilli, and Enterococci. Risk factors for resistance were previous use of cephalosporins, diabetes mellitus, upper gastrointestinal bleeding, nosocomial acquisition, and a low polymorphonuclear count in ascites. Regarding third-generation cephalosporin resistance, adequate empirical treatment was 80.7%. Independent predictors of mortality were nosocomial acquisition, poor hepato-renal function, immunosuppressive therapy, a marked inflammatory response during the episode and either third-generation cephalosporin-resistance or low rates of adequate empirical treatment.

CONCLUSIONS

The risk of third-generation cephalosporin resistance was particularly high in nosocomially-acquired episodes of spontaneous bacterial peritonitis, but also occurred in healthcare system-acquired cases. The extent of resistance and the adequacy of empirical antibiotics had a significant effect on mortality along with the patient's hepato-renal function. These data can help determine the most suitable empirical antimicrobial treatments in these patients.

Rectal carriage of extended-spectrum beta-lactamase-producing gram-negative bacilli in community settings in Madagascar

Background

Extended-spectrum ß-lactamase-producing Enterobacteria (ESBL-PE) emerged at the end of the 1980s, causing nosocomial outbreaks and/or hyperendemic situations in hospitals and long-term care facilities. In recent years, community-acquired infections due to ESBL-PE have spread worldwide, especially across developing countries including Madagascar.

Objectives

This study aimed to determine the prevalence and risk factors of intestinal carriage of ESBL-PE in the community of Antananarivo.

Methods

Non-hospitalized patients were recruited in three health centers in different socio economic settings. Fresh stool collected were immediately plated on Drigalski agar containing 3 mg/liter of ceftriaxone. Gram-negative bacilli species were identified and ESBL production was tested by a double disk diffusion (cefotaxime and ceftazidime +/− clavulanate) assay. Characterization of ESBLs were perfomed by PCR and direct sequencing . Molecular epidemiology was analysed by Rep-PCR and ERIC-PCR.

Results

484 patients were screened (sex ratio  = 1.03, median age 28 years). 53 ESBL-PE were isolated from 49 patients (carrier rate 10.1%). The isolates included Escherichia coli (31), Klebsiella pneumoniae (14), Enterobacter cloacae (3), Citrobacter freundii (3), Kluyvera spp. (1) and Pantoae sp.(1). In multivariate analysis, only the socioeconomic status of the head of household was independently associated with ESBL-PE carriage, poverty being the predominant risk factor.

Conclusions

The prevalence of carriage of ESBL in the community of Antananarivo is one of the highest reported worldwide. This alarming spread of resistance genes should be stopped urgently by improving hygiene and streamlining the distribution and consumption of antibiotics.

Infections due to Escherichia coli producing extended-spectrum beta-lactamase among hospitalised patients: factors influencing mortality

We performed a retrospective matched-cohort study to determine the risk factors for mortality among patients with Escherichia coli infections. From January 1996 to December 2003, 100 hospitalised patients with extended-spectrum beta-lactamase (ESBL)-producing E. coli infections were compared with patients not infected with ESBL-producing E. coli. These patients were selected according to the same site of infection and the closest date of admission. Comparison of the two groups showed that empirical antibiotic therapy was more often inadequate in patients infected with ESBL-producing E. coli (44% vs 15%; P<0.01), and that early mortality (16% vs 6%; P=0.02) and overall mortality (25% vs 11%; P=0.01) were also significantly higher in patients with ESBL-producing E. coli infections. A multivariate model identified the urinary tract focus as the only independent risk factor influencing early mortality for E. coli infections [odds ratio (OR): 0.1; 95% confidence interval (CI): 0.03-0.7; P=0.01]. All 12 patients with ESBL-producing E. coli urinary tract infections treated initially with an oxyimino-beta-lactam survived. Subsequent analysis of the factors influencing early mortality in the cohort of 130 patients with a non-urinary E. coli infection found inadequate empirical antibiotic therapy as an independent risk factor for mortality only for non-urinary E. coli infections (adjusted OR: 3.0; 95% CI: 1.0-8.6; P=0.03). The study showed that hospitalised patients with ESBL-producing E. coli infections more often receive inadequate empiric antibiotic therapy and have a higher mortality rate than those infected with non-ESBL-producing strains. The site of infection strongly influences mortality. The administration of inadequate empirical antibiotic therapy is independently associated with higher mortality only among patients with non-urinary tract infections.

Association of broad-spectrum antibiotic use with faecal carriage of oxyiminocephalosporin-resistant enterobacteriaceae in an intensive care unit

The link between administration of antibiotics and detection of third-generation-cephalosporin-resistant (TGCR) enterobacteriaceae in faeces was studied in patients in a burns intensive care unit (ICU). The presence of extended-spectrum beta-lactamase producers was also determined in these isolates. At least two rectal swab samples were taken from 43 of 72 patients admitted to the ICU from January 1998 to June 1999. Antibiotic resistance tests were performed for all isolated enterobacteriaceae using the methods of the National Committee for Clinical Laboratory Standards. Only 10 out of 30 antibiotic-treated patients showed TGCR enterobacteriaceae in faeces. Fisher's exact test showed a relationship between the administration of oxyiminocephalosporins (third-generation cephalosporins) (P=0.002) or carbapenems (P=0.003) and the isolation of TGCR enterobacteriaceae from faeces. The administration of oxyiminocephalosporins led to the selection of resistant strains in the faecal flora.

Risk-factors for acquisition of extended-spectrum β-lactamase-producing Escherichia coli among hospitalised patients

Between 1996 and 2002, 103 hospitalised patients yielding one or more clinical isolates of extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-EC) were identified. A significant increase was observed in the incidence of ESBL-EC colonisation or infection during the study period (1.65 episodes/100 000 patient-days in 1996 to 12.6 episodes/100 000 patient-days in 2002; p 0.01). Infection developed in 70 (68%) patients (75 episodes), with surgical site (44%) and urinary tract (17%) infections being the most frequent. Pulsed-field gel electrophoresis showed extensive clonal diversity among the isolates. A case-control study and multivariate analysis identified female gender (OR 2.1; p 0.01), use of a nasogastric tube (OR 3.5; p 0.001) and previous antibiotic therapy (OR 3.9; p < 0.001) as independent variables associated with acquisition of ESBL-EC. The study demonstrated a progressive increase in the number of ESBL-EC isolates in a non-epidemic setting. Most cases of ESBL-EC colonisation or infection occurred in hospitalised patients exposed to invasive procedures and antibiotic pressure.

Detection of extended-spectrum beta-lactamase-producing, multidrug-resistant environmental isolates of Escherichia coli that bind to human bladder cells

Compared to the number of studies examining extended-spectrum beta-lactamase (ESBL)-producing clinical isolates, environmental ESBL-producers have not been studied extensively. To investigate environmental ESBL-producing Escherichia coli, 22 cephalothin-resistant E. coli were isolated from Han River in Seoul, Korea. These isolates were resistant to ampicillin, cephalothin, and gentamicin, and 14 isolates among these were resistant to norfloxacin. All of these isolates produce AmpC and CMY, OXA, or TEM as determined by isoelectric point focusing (IEF) gel electrophoresis and PCR. One isolate (57-214) producing AmpC and OXA was resistant to all antibiotics (ampicillin, cephalothin, norfloxacin, gentamicin, cefotaxime, ceftazidime) tested in this study. Six isolates, including isolate 57-214, could adhere to T24 human bladder cells, and these isolates were not related to each other as shown with random amplified polymorphic DNA (RAPD). Results showed that environmental ESBL-producing E. coli is able to colonize in bladder cells and directly cause antibiotic-resistant urinary tract infection.

[Risk factors associated with ceftazidime-resistant Klebsiella pneumoniae infection]

INTRODUCTION

Risk factors associated with ceftazidime-resistant Klebsiella pneumoniae (CAZ-R Kp) infection may vary among hospitals and in the same hospital at different time points. Knowledge of these factors is required to establish suitable infection control programs.

METHODS

A case-control study was conducted to assess risk factors for CAZ-R Kp infection. Thirty-two cases were compared with 28 controls admitted to a 200-bed general hospital during 1999 and 2000.

RESULTS

In the univariate analysis Kp CAZ-R isolates were significantly associated with nosocomial acquisition (OR 5 17.40), prior antibiotic use (OR 5 14.94), particularly ciprofloxacin use (OR 5 5), and hospitalization stay of more than 6 days (OR 5 6.72). Significantly associated variables in the logistic regression analysis included nosocomial acquisition (OR 5 9.29), prior antibiotic use (OR 5 6.21), and particularly, ciprofloxacin use (OR 5 10.84).

CONCLUSIONS

Efforts toward more rational overall antibiotic use and particularly ciprofloxacin use, combined with infection control measures are necessary to decrease the prevalence of CAZ-R Kp in our hospital.

Transferable plasmid mediating resistance to multiple antimicrobial agents in Klebsiella pneumoniae isolates in Greece

OBJECTIVE

To investigate the underlying resistance mechanisms in 10 Klebsiella pneumoniae isolates.

METHODS

Ten K. pneumoniae strains according to distinct bacteriocin typing and REP-PCR, were examined for their plasmid content, their ability to transfer their resistance to aminoglycosides and third-generation cephalosporins, and their production of aminoglycoside-modifying enzymes and beta-lactamases.

RESULTS

Transfer of resistance to the above-mentioned antibiotics as well as to co-trimoxazole and tetracycline in Escherichia coli strain RC 85 at a frequency of 5-106 was achieved for all strains by conjugation. Similar strains harbor a self-transferable multiresistant plasmid (80 kb) with similar EcoRI and HindIII restriction patterns. This plasmid encodes an extended-spectrum beta-lactamase which confers high-level resistance to third-generation cephalosporins and aztreonam. It produces SHV-5 beta-lactamase, as demonstrated by isoelectric focusing and DNA sequencing. Aminoglycoside resistance was co-transferred, and AAC(6')-I, mediating resistance to gentamicin, tobramycin, netilmicin and amikacin, and AAC(3)-I, mediating resistance to gentamicin and sisomycin, were encoded in all isolates and their transconjugants, while APH(3')-I, mediating resistance to kanamycin and neomycin, was encoded in seven strains.

CONCLUSIONS

It appears that a multiresistant transferable plasmid encoding the SHV-5 beta-lactamase, causing unusually high resistance to ceftazidime and aztreonam, and the combination AAC(6')-I + AAC(3)-I of acetylating enzymes causing, also resistance to all clinically available aminoglycosides, is established in K. pneumoniae in Greece.

A simple and reliable method to screen isolates of Escherichia coli and Klebsiella pneumoniae for the production of TEM- and SHV-derived extended-spectrum beta-lactamases

OBJECTIVE: To evaluate which of 24 beta-lactams used in susceptibility tests best discriminated between strains of Klebsiella pneumoniae and Escherichia coli that produce extended spectrum beta-lactamases (ESBLs) from strains that produce older, more familiar, plasmid-mediated beta-lactamases such as TEM-1 and SHV-1. METHODS: Susceptibility to the 24 beta-lactam agents was determined by agar dilution and disk diffusion methodologies, using 27 strains of K. pneumoniae and E. coli that produced 22 different older plasmid-mediated beta-lactamases and 28 strains that produced 17 different ESBLs. RESULTS: In general, strains that produced ESBLs were intermediate or resistant to cefpodoxime, whereas those that produced other beta-lactamases were susceptible to this agent. The agar dilution test exhibited 96% sensitivity and 100% specificity in discriminating these two groups of organisms. The disk diffusion test exhibited 100% sensitivity and 96% specificity. All other beta-lactam agents tested were inferior discriminators between the two groups of organisms. CONCLUSIONS: Agar dilution and disk diffusion tests with cefpodoxime can be used to discriminate strains of K. pneumoniae and E. coli that produce ESBLs from those that produce older, plasmid-mediated beta-lactamases.

Molecular epidemiology of an outbreak of Serratia marcescens in a neonatal intensive care unit

OBJECTIVE

To investigate and control a biphasic outbreak of Serratia marcescens in a neonatal intensive care unit (NICU).

DESIGN

Epidemiological and laboratory investigation of the outbreak.

SETTING

The NICU of the 1,470-bed teaching hospital of the University "Federico II," Naples, Italy.

PATIENTS

The outbreak involved 56 cases of colonization by S marcescens over a 15-month period, with two epidemic peaks of 6 and 3 months, respectively. Fourteen (25%) of the 56 colonized infants developed clinical infections, 50% of which were major (sepsis, meningitis, or pneumonia).

METHODS

Epidemiological and microbiological investigations, analysis of macrorestriction pattern of genomic DNA through pulsed-field gel electrophoresis (PFGE) of clinical and environmental isolates, and institution of infection control measures.

RESULTS

Analysis of macrorestriction patterns of genomic DNA by PFGE demonstrated that the vast majority of S marcescens isolates, including three environmental strains isolated from two handwashing disinfectants and the hands of a nurse, were of the same clonal type. The successful control of the outbreak was achieved through cohorting of noncolonized infants, isolation of S marcescens-infected and -colonized infants, and an intense educational program that emphasized the need for adherence to glove use and handwashing policies. The NICU remained open to new admissions.

CONCLUSIONS

Outbreaks caused by S marcescens are very difficult to eradicate. An infection control program that includes molecular typing of microorganisms and the proper dissemination among staff members of the typing results is likely to be very effective in reducing NICU-acquired infections and in controlling outbreaks caused by S marcescens, as well as other multiresistant bacteria.

An outbreak of hospital-acquired Klebsiella pneumoniae bacteraemia, including strains producing extended-spectrum beta-lactamase

This study describes the clinical outcome of an outbreak of extended-spectrum beta-lactamase producing Klebsiella pneumoniae (ESBL-KP) bacteraemia. Ninety-two episodes of hospital-acquired K. pneumoniae bacteraemia were studied, 49 ESBL-KP and 43 non-ESBL-KP, from May 1993 to June 1995. Of these, 44 (90%) episodes of ESBL-KP vs. 20 (46%) episodes of non-ESBL-KP occurred in intensive care unit (ICU) patients. The incidence of K. pneumoniae bacteraemia (mainly due to ESBL-KP) increased in the ICU during the outbreak. A significant association was found between intravascular catheter-related bacteraemia and isolation of ESBL-KP [27 (56%) in the ESBL-KP group vs. 13 (30%) in the non-ESBL-KP group;P= 0.01]. The worst prognostic features were identified as age > 65 years (P= 0.02), septic shock (P< 0.001) and secondary bacteraemia (P= 0.04). High rates of resistance to beta-lactam/beta-lactamase inhibitors observed in our ESBL-KP isolates, as well as variable activity of aminoglycosides, restricts the empirical use of these antibiotics. Carbapenems should be the treatment of choice since they are uniformly active against these strains. Our study shows that ESBL-KP bacteraemia occurring in an epidemic ICU setting is mainly catheter-related. We did not find ESBL strains to be associated with a significantly poor outcome.

Control of a prolonged outbreak of extended-spectrum beta-lactamase-producing enterobacteriaceae in a university hospital

Extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBLPE) were isolated from clinical specimens from 130 to 140 patients/year in 1989-1991 in our hospital. In February 1992, a control program was initiated: screening tests in 3 intensive care units (ICUs) and contact-isolation precautions in all units. The septic surgical unit served as an isolation ward for surgical patients from whom ESBLPE was isolated. In 1992, the incidence of ESBLPE acquisition failed to decrease, and most acquisitions occurred in 3 ICUs. Critical evaluation of implementation of isolation procedures in these ICUs prompted corrective measures for barrier precautions. The incidence of acquired cases subsequently decreased, and a second evaluation determined that these measures had been correctly applied. The incidence of acquired cases in the septic surgical unit was lower than those in the other units. Decreases were also found in the incidence of acquisition of other hand-transmitted multidrug-resistant organisms. Barrier precautions, screening tests for ICU patients, and grouping of cohorts after ICU discharge are effective in controlling the spread of multidrug-resistant microorganisms by cross-contamination. The outbreak was effectively controlled without restricting antimicrobial use.

Use of microdilution panels with and without beta-lactamase inhibitors as a phenotypic test for beta-lactamase production among Escherichia coli, Klebsiella spp., Enterobacter spp., Citrobacter freundii, and Serratia marcescens

Over the past decade, a number of new beta-lactamases have appeared in clinical isolates of Enterobacteriaceae that, unlike their predecessors, do not confer beta-lactam resistance that is readily detected in routine antibiotic susceptibility tests. Because optimal methodologies are needed to detect these important new beta-lactamases, a study was designed to evaluate the ability of a panel of various beta-lactam antibiotics tested alone and in combination with beta-lactamase inhibitors to discriminate between the production of extended-spectrum beta-lactamases, AmpC beta-lactamases, high levels of K1 beta-lactamase, and other beta-lactamases in 141 isolates of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, Enterobacter aerogenes, Citrobacter freundii, and Serratia marcescens possessing well-characterized beta-lactamases. The microdilution panels studied contained aztreonam, cefpodoxime, ceftazidime, cefotaxime, and ceftriaxone, with and without 1, 2, and 4 microg of clavulanate per ml or 8 microg of sulbactam per ml and cefoxitin and cefotetan with and without 8 microg of sulbactam per ml. The results indicated that a minimum panel of five tests would provide maximum separation of extended-spectrum beta-lactamase high AmpC, high K1, and other beta-lactamase production in Enterobacteriaceae. These included cefpodoxime, cefpodoxime plus 4 microg of clavulanate per ml, ceftazidime, ceftriaxone, and ceftriaxone plus 8 microg of sulbactam per ml. Ceftriaxone plus 2 microg of clavulanate per ml could be substituted for cefpodoxime plus 4 microg of clavulanate per ml without altering the accuracy of the tests. This study indicated that tests with key beta-lactam drugs, alone and in combination with beta-lactamase inhibitors, could provide a convenient approach to the detection of a variety of beta-lactamases in members of the family Enterobacteriaceae.

Extended-spectrum beta-lactamases in clinical isolates of Klebsiella pneumoniae from Zagreb, Croatia

Forty clinical isolates of Klebsiella pneumoniae, from various clinical specimens, with reduced susceptibility to ceftazidime, were tested for extended-spectrum beta-lactamase (ESBL) production. ESBL production was demonstrated by an 8-fold reduction in the minimum inhibitory concentration (MIC) of ceftazidime combined with clavulanate (2 mg/L) compared to ceftazidime alone in all strains. The aim of this investigation was the biochemical and molecular characterization of the ESBL produced by K. pneumoniae strains and their Escherichia coli transconjugants. Transfer of ceftazidime resistance was demonstrated in 23 of 40 strains. Thirteen strains produced an ESBL with the isoelectric point of 8.2 which was encoded by a self-transferable multiresistance plasmid of 150 kb. The substrate profile was similar to that of the SHV-5 isolated initially in Chile. Seven of these 12 strains had an additional TEM beta-lactamase. Six isolates and their transconjugants produced a plasmid-encoded ESBL with an isoelectric point close to 5.4. The remaining 21 strains produced an ESBL with an isoelectric point of 7.6 (thus probably SHV-2) which was encoded on a plasmid transferable to E. coli in 4 strains only. Four of those strains possessed an additional plasmid encoded TEM beta-lactamase with an isoelectric point close to 5.4. The transconjugants harbored a multiresistance plasmid of 150 kb. Thus SHV-2 and SHV-5 enzymes appear to have been the most common ESBLs in K. pneumoniae from Zagreb during 1994-1995.

Molecular epidemiology as an effective tool in the surveillance of infections in the neonatal intensive care unit

OBJECTIVES

nosocomial infections result in considerable morbidity and mortality in Neonatal Intensive Care Units (NICUs). The aim of this study was to investigate the usefulness of the molecular epidemiology approach in the surveillance and control of infections in the NICU.

METHODS

a 1-year prospective surveillance of nosocomial infections in a NICU was performed using traditional epidemiological methods as well as molecular typing of micro-organisms.

RESULTS

the nosocomial infection rate among the 343 newborns was 24.8%. The risk of infection was associated with low birth weight, prolonged length of stay, empiric antibiotic treatment and nasopharyngeal colonization. Four pathogens (Klebsiella pneumoniae, methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE) and methicillin-sensitive Staphylococcus aureus (MSSA) were responsible for more than 80% of the infections. Extended-spectrum beta-lactamase-producing (ESBL) K. pneumoniae and MRSA infections constituted outbreaks caused by a single clone, whereas MRSE and MSSA infections did not represent outbreaks but rather a series of sporadic infections caused by different strains.

CONCLUSIONS

molecular epidemiology techniques are powerful tools that can elucidate modes of spread and reservoirs of infection in the NICU and identify effective measures to control epidemic or endemic situations.

Outer membrane profiles of clonally related Klebsiella pneumoniae isolates from clinical samples and activities of cephalosporins and carbapenems

Fifteen isolates of Klebsiella pneumoniae producing extended-spectrum beta-lactamases (ESBLs) isolated during a nosocomial outbreak were studied. The strains belonged to the same clonal type, as shown by pulsed-field gel electrophoretic analysis of chromosomal DNA. All the isolates were resistant to extended-spectrum cephalosporins, aztreonam, gentamicin, and fluoroquinolones and were susceptible to carbapenems, tobramycin, netilmicin, and amikacin. None of the isolates expressed the OmpK36 porin. Eight isolates, for which the MICs of cefoxitin were > or = 64 micrograms/ml, showed a diminished level or no expression of a 35-kDa porin. The MICs of meropenem, cefotaxime, and cefpirome were three to eight times higher for porin-deficient isolates than for isolates expressing the 35-kDa porin, but the MICs of imipenem increased two times for porin-deficient isolates compared to those for isolates expressing the porin. This MIC increase reverted to a level similar to that for the parental strain when porin-deficient isolates were transformed with the gene coding for the K. pneumoniae porin OmpK36. It is concluded that the high level of resistance to cefoxitin and the increase in the MICs of meropenem, cefotaxime, and cefpirome for the ESBL-producing K. pneumoniae isolates studied are associated with porin deficiency.

Epidemiology and successful control of a large outbreak due to Klebsiella pneumoniae producing extended-spectrum beta-lactamases

An outbreak due to extended-spectrum beta-lactamase-producing Klebsiella pneumoniae (ESBL-KP) was detected from May 1993 to June 1995. A total of 145 patients, particularly patients in intensive care units (ICUs) (107 patients [72%]), were colonized or infected. Infection developed in 92 (63%) patients, and primary bacteremia caused by ESBL-KP was the most frequent infection (40 of 92 patients [43%]). A single clone of ESBL-KP was identified by pulsed-field gel electrophoresis analysis throughout the whole period, and no molecular epidemiological relationship could be found between the epidemic strain and non-ESBL-KP isolates. To determine risk factors for ESBL-KP infection weekly rectal swabs were obtained in three serial incidence surveys (470 patients); the probabilities of carriage of ESBL-KP in the digestive tract were 33% (October and November 1993), 40% (May and June 1994), and 0% (October and November 1995) at 10 days of ICU admission. A logistic regression model identified prior carriage of ESBL-KP in the digestive tract (odds ratio, 3.4; 95% confidence interval 1.1 to 10.4) as an independent variable associated with ESBL-KP infection. A statistically significant correlation was observed between the restricted use of oxyimino-beta-lactams (189 defined daily doses [DDD]/ 1,000 patient-days to 24 DDD/1,000 patient-days) and the trends of ESBL-KP infection (r = 0.7; P = 0.03).

Oropharyngeal or gastric colonization and nosocomial pneumonia in adult intensive care unit patients. A prospective study based on genomic DNA analysis

Colonization of the digestive tract has been supposed to be the source of many hospital-acquired infections, especially nosocomial pneumonia. To assess the relationship between oropharyngeal and gastric colonization and subsequent occurrence of nosocomial pneumonia, we prospectively studied 86 ventilated, intensive care unit (ICU) patients. Oropharyngeal or gastric colonizations were detected and quantified on admission and twice weekly during ICU stay. When nosocomial pneumonia was suspected on clinical grounds (new chest X-ray infiltrate and purulent tracheal secretions), diagnosis was assessed on fiberoptic bronchoscopy with quantitative cultures of a protected specimen brush sampling and/or a plugged telescoping catheter sampling yielding > or = 10(3) cfu/ml of at least one microorganism. Bacterial strains responsible for colonization and infection (Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacteriaceae, and Staphylococcus aureus) were compared using pulsed-field electrophoresis. A total of 31 cases (36%) of pneumonia were diagnosed. Oropharyngeal colonization, detected either on admission or from subsequent samples, was a predominant factor of nosocomial pneumonia as compared with gastric colonization. For instance, oropharyngeal colonization with A. baumannii yielded a 7.45-fold estimated increased risk of pneumonia as compared with patients not yet or not identically colonized (p = 0.0004). DNA genomic analysis demonstrated that an identical strain was isolated from oropharyngeal or gastric samples and bronchial samples in all but three cases of pneumonia, due to S. aureus. These findings provide better knowledge of the pathophysiology of nosocomial pneumonia in mechanically ventilated patients.

Relationship between adhesion to intestinal Caco-2 cells and multidrug resistance in Klebsiella pneumoniae clinical isolates

Klebsiella pneumoniae is an opportunistic gram-negative pathogen involved in outbreaks of nosocomial infections in intensive care units. Strains are resistant to multiple antibiotics, and 15 to 30% of them are also resistant to the broad-spectrum cephalosporins by the production of R plasmid-encoded extended-spectrum beta-lactamases. Because the gastrointestinal tracts of patients have been shown to be the reservoir for nosocomial strains of K. pneumoniae, we looked for a correlation between antibiotic resistance and adhesion of K. pneumoniae strains to intestinal cells. We investigated adhesion to the human intestinal epithelial Caco-2 cell line of 61 clinical K. pneumoniae strains isolated in hospitals in Clermont-Ferrand, France. None of the strains tested expressed the previously described adhesive factors CF29K and KPF-28. Adhesive properties were found for 42.6% of the strains tested (26 strains). Just 7.7% (2 strains) of the 26 strains producing only the chromosomally encoded SHV-1 beta-lactamase adhered to the Caco-2 cell line, whereas 68.5% (24 strains) of the 35 strains producing a plasmid-encoded beta-lactamase were adherent. All the adherent strains, and even the two strains producing only the SHV-1 enzyme, harbored at least one self-transmissible R plasmid. At variance for CAZ-1/TEM-5 or CAZ-5/SHV-4 beta-lactamase-producing K. pneumoniae strains, curing and mating experiments demonstrated that the self-transmissible R plasmids encoding the TEM-1, CTX-1/TEM-3, CAZ-2/TEM-8, CAZ-6/TEM-24, or CAZ-7/TEM-16 beta-lactamase were not involved in the adhesion of K. pneumoniae strains to intestinal epithelial cells. Nevertheless, there was an association of multiple antibiotic resistance, including resistance to extended-spectrum cephalosporins, and adhesive properties in K. pneumoniae clinical isolates.

Epidemiological typing of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae isolates responsible for five outbreaks in a university hospital

Thirty-seven isolates of extended-spectrum beta-lactamase-producing (ESBL) Klebsiella pneumoniae implicated in five nosocomial outbreaks (I-V) on three distinct wards of our hospital were compared using capsular typing, biotyping, antibiotyping, enzyme electrophoresis typing and DNA macrorestriction analysis with Xba I resolved by pulsed-field gel electrophoresis. The isolates from each outbreak had common phenotypic and genotypic characteristics indicating that they were related epidemiologically. Isolates from outbreaks I (four patients) and V (13 patients), although they occurred in two different wards (neurology and surgery) and three years apart, produced the same ESBL with a pI of 7.8 (SHV-4) and were of serotype K25. The Xba I patterns were closely related. The isolates of outbreaks II (seven patients), III (four patients) and IV (seven patients), which occurred in a single surgical intensive care unit, produced an ESBL with a pI of 6.3 (TEM-3). Isolates from outbreaks III and IV, which occurred six months apart, were of serotype K68 and had similar Xba I patterns suggesting that the two outbreaks were due to a single strain which persisted endemically in the ward. The isolates from outbreak II were of serotype K62, and had distinct characteristics from the two later outbreaks. The Xba I patterns of the isolates from outbreaks "I and V', II and "III and IV' had Dice similarity coefficients under 40% showing that the three groups were genetically distant. DNA macrorestriction analysis was a useful complement to phenotypic methods for identifying K. pneumoniae strains responsible for outbreaks harbouring a common ESBL.

Risk factors for faecal carriage of Klebsiella pneumoniae producing extended spectrum beta-lactamase (ESBL-KP) in the intensive care unit

In the course of an outbreak of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae (ESBL-KP) in an intensive care unit (ICU), we conducted active surveillance to determine the risk factors for ESBL-KP faecal colonization of patients. We used weekly rectal samples during a four-month period. ESBL-KP was found in the faeces of 72 of 188 (38%) patients, and 42 (58%) of them were colonized within the first week of admission to the ICU. The probability of remaining free of faecal colonization was less than 20% at 30 days of ICU admission. The risk factors associated with ESBL-KP faecal colonization were clinical severity score at admission (P = 0.004), arterial catheterization (P = 0.002), total parenteral nutrition (P = 0.04), urinary catheterization (P = 0.01), mechanical ventilation (P < 0.001), and previous antibiotic therapy (P = 0.04). A logistic regression analysis identified duration of urinary catheterization (OR:3.5; 95% CI 1.2-10.3) and mechanical ventilation (OR:4.6; 95% CI 1.1-19.3) as independent risk factors for ESBL-KP faecal colonization. Our results suggest that in an ESBL-KP prevalent environment, manipulations that facilitate cross-infection are the most relevant in the acquisition of the micro-organism and risk increases throughout hospitalization.

Secondary carriage with multi-resistant Acinetobacter baumannii and Klebsiella pneumoniae in an adult ICU population: relationship with nosocomial infections and mortality

A one year prospective, observational survey was performed to evaluate the abnormal carriage of multi-resistant Klebsiella pneumoniae and/ or Acinetobacter baumannii, to determine associated risk factors for carriage, and to correlate the abnormal carriage with infectious morbidity and mortality in the intensive care unit (ICU) of a University Hospital. Two hundred and ninety-eight patients who stayed in the ICU > 48h, and were not neutropenic, were studied. Salivary and rectal samples were obtained on admission and weekly until discharge. Out of 265 evaluable patients, 88 (33%) developed oropharyngeal and/or rectal carriage within a median of nine days. Three factors were significantly associated with abnormal carriage: higher 'severity of illness' score on admission, a threefold increase in ICU stay, and the need for mechanical ventilation. K. pneumoniae or A. baumannii accounted for 57/158 (36%) of all ICU-acquired infections (in 46 patients). They were considered as secondary endogenous infections (SEI) in 42 patients who were previously colonized with the same strains, and developed infection within a median of three days (range 0-68 days). Prolonged stay in ICU was the only factor associated with SEI in the carrier population. Mortality was significantly greater in the carrier group (43 vs 25%, P = 0.0006). Post hoc stratification suggested that abnormal carriage only influenced mortality in patients showing a low severity of illness score on admission to ICU. Abnormal carriage was found in the most severely ill patients, predisposed to secondary nosocomial infections, and could influence mortality in the less severely ill.

Detection of SHV-5 extended-spectrum beta-lactamase in Klebsiella pneumoniae strains isolated in Italy

Thirty-five Klebsiella pneumoniae strains isolated during 1993-1994 in intensive care units of a large Italian hospital were examined for the presence of extended-spectrum beta-lactamases. Five strains showed a high level of simultaneous resistance to beta-lactam agents, including ceftazidime and aztreonam, conferred by a large (130 kb) self-transferable plasmid (in 4 of 5 strains). Isoelectrofocusing and hybridisation studies suggest that these enzymes can be identified as SHV-5 extended-spectrum beta-lactamases. Pulsed-field get electrophoresis analysis showed three different genomic fingerprinting profiles, while plasmid restriction enzyme digestion revealed three different patterns, demonstrating that the diffusion of SHV-5 beta-lactamase is not the result of a single strain or plasmid dissemination.

In vivo acquisition of extended-spectrum beta-lactamase in Salmonella enteritidis during antimicrobial therapy

The recovery of a Salmonella enteritidis strain that acquired resistance to beta-lactams (including cefotaxime), to aminoglycosides and to chloramphenicol subsequent to cefotaxime therapy is reported. This resistance pattern to beta-lactams was due to the presence of an extended-spectrum beta-lactamase. The isoelectric point of this extended-spectrum beta-lactamase was 6.3. The resistance genes were located on a transferable high-molecular-weight plasmid.

Molecular epidemiology of Klebsiella pneumoniae strains that produce SHV-4 beta-lactamase and which were isolated in 14 French hospitals

Preliminary results suggested that the diffusion in France of the SHV-4 extended-spectrum beta-lactamase was probably due to the spread of one single epidemic strain of Klebsiella pneumoniae. In this study, we tested various phenotypic and genotypic markers to compare K. pneumoniae strains producing this enzyme isolated in 14 French hospitals between 1987 and 1989. All of the strains were of the same capsule serotype, K25. Twelve of them were of the same biotype: weak urease activity and no sucrose fermentation. Among the six plasmid profiles observed, one accounted for eight strains. Large plasmids of 170 kb encoding SHV-4 beta-lactamase were present in all strains of K. pneumoniae and could be transferred by conjugation with high frequency to Escherichia coli J53-2 or HB101 from all except one strain. Plasmid EcoRI restriction patterns suggested that these plasmids were closely related and similar to pUD18 encoding SHV-3 beta-lactamase, originally described in France and differing from SHV-4 by one amino acid substitution. Ribotyping with EcoRI and HindIII and genomic fingerprinting with XbaI by pulsed-field gel electrophoresis were concordant and suggested that 12 of the isolates recovered from the 14 hospitals were probably the same strain. Dissemination in France of the SHV-4 extended-spectrum beta-lactamase was thus essentially due to the diffusion of a single K. pneumoniae clone.

Multiply resistant Klebsiella pneumoniae strains from two Chicago hospitals: identification of the extended-spectrum TEM-12 and TEM-10 ceftazidime-hydrolyzing beta-lactamases in a single isolate

Ceftazidime-resistant Klebsiella pneumoniae strains began to appear when ceftazidime usage was increased in two unrelated Chicago hospitals. These strains produced a beta-lactamase with an isoelectric point of 5.6 (RP-5.6) and strong hydrolyzing activity against ceftazidime. Two different restriction digest profiles were associated with the ceftazidime resistance plasmids. A second beta-lactamase with a pI of 5.2 (RP-5.2) was coproduced in two representative strains. The second beta-lactamase hydrolyzed ceftazidime, cefotaxime, and aztreonam with relative hydrolysis rates of < 8% of that observed for benzylpenicillin. Both enzymes were inhibited by clavulanic acid and tazobactam. Nucleotide sequencing of the genes coding for RP-5.2 and RP-5.6 revealed sequences identical to those of the TEM-12 and TEM-10 beta-lactamase genes, respectively. Both genes were derived from a TEM-1 sequence related to that of the gene encoded on the Tn2 transposon. Single point mutations are required to progress from TEM-1 to TEM-12 and from TEM-12 to TEM-10. Extracts from broths grown from single cell isolates of the strain producing TEM-12 and TEM-10 were shown to contain both enzymes. Transconjugants producing either the TEM-12 or the TEM-10 beta-lactamase were obtained. A significant finding was that both enzymes were encoded by plasmids with identical restriction digest patterns. These studies show that mutations leading to extended-spectrum beta-lactamases can occur sequentially in the same organism, with the genes encoding both enzymes maintained stably.

Origin and impact of plasmid-mediated extended-spectrum beta-lactamases

Resistance to oxyimino cephalosporins was originally highlighted by the emergence of plasmid-encoded extended-spectrum beta-lactamases deriving by mutation from TEM-1, TEM-2 and SHV type enzymes (class A). The broader spectrum of resistance produced by these enzymes is related to more amino acid substitutions, but susceptibility to seven alpha-methoxyimino cephalosporins and carbapenems was preserved until recently. Clavulanate-sensitive extended-spectrum beta-lactamases are distributed worldwide, mainly among Klebsiella pneumoniae isolates. Novel clavulanate-sensitive extended-spectrum beta-lactamases deriving from other class A enzymes (e.g. MEN-1 from beta la OXY, OXA-11 in Pseudomonas aeruginosa from PSE-2) have been reported. Recently, clavulanate-resistant extended-spectrum beta-lactamases (class C) were encountered amongst single isolates, mostly Klebsiella pneumoniae. These cephalosporinases or cefamycinases (usually chromosomally mediated) have expanded the spectrum of plasmid-encoded resistance to include seven alpha-methoxyimino cephalosporins. Thus far, only two isolates (1 Pseudomonas aeruginosa, 1 Bacteroides fragilis), both recovered in Japan, with plasmid-mediated resistance to carbapenems have been found.

Molecular epidemiology of plasmid spread among extended broad-spectrum beta-lactamase-producing Klebsiella pneumoniae isolates in a pediatric hospital

Over a 12-month period, 43 children in eight different wards of our hospital (Hôpital Robert Debré) were infected or colonized with Klebsiella pneumoniae strains producing extended broad-spectrum beta-lactamases. The epidemiology of the outbreak was studied by a molecular approach including the determination of the beta-lactamase physicochemical parameters and plasmid profiles, as well as analysis of the restriction fragment length polymorphisms of the rDNA regions (ribotyping). The last approach produced 12 and 5 different patterns with EcoRI and HindIII, respectively, thus identifying 15 different ribotypes among the 43 clinical K. pneumoniae strains. However, 60% of the strains in six wards belonged to only two ribotypes, whereas nine ribotypes were observed only once. Twelve isolates from different wards that were representative of the eight most common ribotypes showed four different beta-lactamase isoelectric focusing patterns and seven different plasmid profiles by direct analysis or after EcoRI digestion. Thus, at least two genetically unrelated strains in the same ward were found to have the same plasmid content. Our results show the complexity of the outbreak, which was associated with patient-to-patient cross-contamination with several epidemic strains with different plasmid contents, interspersed sporadic cases with nonepidemic strains, and the possible spread of a plasmid. The combination of plasmid profile analysis and ribotyping therefore seems to be powerful at deciphering the details of such outbreaks.

Resistance to cefotaxime and seven other beta-lactams in members of the family Enterobacteriaceae: a 3-year survey in France

During the second quarter each of 1988, 1989, and 1990, a French collaborative study group, including 12 university hospital laboratories, surveyed the resistance to beta-lactams of clinical isolates from hospitalized patients: consecutively, 10,641, 10,692, and 9,382 isolates were tested. The distribution of bacterial species over time was similar in each laboratory. The susceptibilities of microorganisms to amoxicillin, ticarcillin, cephalothin, cefoxitin, cefotaxime (CTX), ceftazidime (CAZ), aztreonam (ATM), and imipenem (IPM) were measured by the disk diffusion method in accordance with the recommendations of the Antibiogram Committee of the French Society for Microbiology. Five reference strains were included for quality control. Extended-spectrum beta-lactamases were detected by the synergistic effect of the combination of clavulanic acid-amoxicillin with CTX, CAZ, and ATM in the double-diffusion test. A synergistic effect with CTX, CAZ, and ATM was detected for 1.5% of all strains, mainly those of Klebsiella pneumoniae (13.3%). For this species, the synergy test enabled the detection of roughly 50% of the resistant strains misclassified as susceptible on the basis of interpretative standards. Extended-spectrum beta-lactamases disseminated in 1990 in most enterobacterial species but at a low frequency. Important variations in the percentages of resistant strains were observed in terms of bacterial species, hospitals, and wards. However, when the total number of strains was considered, the percentages of resistance to newer beta-lactams remained low.

Nosocomial outbreak of acute gastroenteritis in a neonatal intensive care unit in Tunisia caused by multiply drug resistant Salmonella wien producing SHV-2 beta-lactamase

In a Tunisian hospital 27 babies, including 12 who were premature, in a single intensive care unit suffered acute gastroenteritis in the period from January to May 1988. The mean age at the onset of gastroenteritis was 8.4 days; nine babies died. Salmonella wien was isolated from stools (all babies) and blood (4 babies). It was also isolated from the stools of one nurse and from a mattress. Twelve of the babies had received cefotaxime, which was successfully replaced by oral colimycin. The outbreak was stopped by the implementation of infection control measures. All isolates of Salmonella wien were of the same biotype, and had the same antibiotic resistance pattern (third generation cephalosporins, monobactams, aminoglycosides, chloramphenicol, trimethoprim and sulphonamides) and plasmid DNA restriction pattern. The isolates were all susceptible to a combination of cefotaxime and clavulanic acid (a beta-lactamase inhibitor), which displayed synergy, suggesting the presence of a beta-lactamase (geometric mean MICs 11.24 micrograms/ml for cefotaxime alone and 0.24 micrograms/ml in combination with 0.1 micrograms/ml potassium clavulanate). All isolates produced TEM-1 and SHV-2 beta-lactamase which was not transferable to Escherichia coli by conjugation. The presence of the SHV-2 enzyme in Salmonella wien may allow it to adapt to newer beta-lactams which is a cause for concern in this hospital.

Outbreak of nosocomial infections due to Klebsiella pneumoniae producing SHV-4 beta-lactamase

One hundred and fifty-four clinical isolates of Klebsiella pneumoniae resistant to broad-spectrum cephalosporins, aztreonam and amikacin were responsible for an outbreak of nosocomial infections lasting eight months in a university hospital in Paris. This outbreak occurred in the intensive care unit (39 patients), haematology units (8 patients) and surgical and medical units (11 patients). Antibiotic resistant strains were isolated from the urinary tract (48%), wound and drainage fluids (21%), respiratory tract (14%), blood (12%) and stools (5%). High resistance to oxyimino-beta-lactams was mediated by a plasmid-encoded beta-lactamase with an isoelectric point of 7.8 (SHV-4). This CAZ-type enzyme conferred a higher level of resistance to ceftazidime and aztreonam (geometric mean MIC 135 mg/l) than to cefotaxime (geometric mean MIC 14 mg/l). All isolates were of the same biotype (weakly urease positive and no sucrose fermentation). Eight Klebsiella pneumoniae strains isolated in different units and at different times of the outbreak were of the same serotype, had common plasmid patterns and harboured a large self-transferable plasmid of about 180 kilobases encoding resistance to penicillins, oxyimino-beta-lactams, aminoglycosides, tetracycline and trimethoprim. These eight large plasmids had indistinguishable EcoRI restriction patterns. These results suggest that a single strain of Klebsiella pneumoniae was responsible for this outbreak.