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PubMed1980

[Comparison of Micro-ID, API 20 E and a conventional technique for the identification of Enterobacteriaceae].

A new system, Micro-ID, for the identification of Enterobacteriaceae is described. 100 strains of Enterobacteriaceae (Table I) are identified by Micro-ID and the identifications are compared with the identifications performed by conventional techniques and by the API 20 E system. There is a total agreement between Micro-ID and conventional techniques on 96.5% and between API 20 E and conventional techniques on 90% (Tables II and III). The differences in the reactions between the systems are discussed and explained. It is concluded, that the Micro-ID and the API 20 E both are very suitable for the identification of Enterobacteriaceae.

Bacteriological Techniques↗
PubMed1981

Beta-glucuronidase activity in Enterobacteriaceae.

Beta-glucuronidase activity has been investigated in 1,221 Enterobacteriaceae strains. The test, using p-nitrophenyl-beta-D-glucuronide (pNPGlcU) agar culture, can be included easily in the routine Enterobacteriaceae biochemical assays. The test is discriminating for Enterobacteriaceae genera and species and useful for identification of some monophasic serotypes of Salmonella.

Enterobacteriaceae↗
PubMed1994

[Evaluation of the usefulness of commercial systems Quantum II and Rapid ID 32E for quick identification of rods from the Enterobacteriaceae family].

The usefulness of the commercial systems Quantum II (Abbott) and Rapid ID 32 E (bioMérieux) for quick identification of Enterobacteriaceae has been evaluated. The study was carried out on strains representing 12 genera of Enterobacteriaceae identified with the aid of classical biochemical tests. The Quantum II system was evaluated in 1985 using 386 strains and the Rapid ID 32 E system in 1992 using 106 strains. When the Quantum II system was used, 237(61.4%) strains were classified correctly in the species, 58(15.0%) were unidentified and 91(23.6%) were identified incorrectly. The Rapid ID 32 E system made possible correct identification of 63(59.4%) strains to the species (in the case of Salmonella rods to the subgenus) and 80(75.5%) strains to the genus. Incorrect identification results were most often obtained in the case of Shigella and Yersinia rods, Salmonella rods of subgenus I fermenting lactose and Enterobacter. The results show that complying with inoculum tests (0.5 according to the McFarland scale) as recommended by the manufacturer and a four-hour incubation, when investigating some Enterobacteriaceae strains which multiply more slowly or exhibit a weaker metabolic activity, does not ensure optimal conditions for the appearance of a set of biochemical features essential for strain identification.

Bacterial Typing Techniques↗
PubMed1976

[Assaying the Enterobacteriaceae contents of fishmeal as criterion for absence of Salmonellae (author's transl)].

1. During comparison of different test systems for examination on salmonellae the routine method revealed only 2 of 35 fishmeal consignments as positive. In second streaks after 48 hours on selective media 5 more consignments were discovered to contain samonellae. Using pre-enrichment culture gave evidence for 11 positive consignments altogether. 2. The pre-enrichment method led to about 20 times higher yields in isolating enterobacteriaceae than the usual enrichment method. 3. Neither salmonellae nor enterobacteriaceae statistically showed uniform distribution in fishmeal. In addition, with the aid of the variance test of homogenity, an extremely heterogeneous ratio of the both germ types to each other was proved. Consequently, assaying the enterobacteriaceae contents is not suitable to draw any reliable conclusions upon the salmonellae contents of fishmeal. 4. Assuming a constant contamination rate of 400.000 salmonella units in consignments of 100 tons and testing them by the required 47 random samples, it can be deduced from probability calculus that only about 1 per cent of a larger number of consignments will fail to be recognized as positive. This risk of acceptance increases progressively with diminishing rate of salmonella contamination. Thus about 80 per cent of consignments containing even as much as 20.000 salmonella units will be accepted as "false negatives". 5. Because of the usually low contamination rates of fishmeal it is an erroneous idea to increase the efficiency of assay by modifying the sample sizes in relation to the shipping weight. For this reason the orders for fishmeal examination in the Federal Republic of Germany should be revised. It is suggested to take at least the number of samples required hitherto for consignments of 100 tons. By this without doubt the risk of accepting "false negatives" can be reduced significantly, but it remains still impossible to recognite every contaminated fishmeal consignment and to stop its acceptance by bacteriological examination. 6. From practical examinations and theoretical considerations it is derivable that one has either to tolerate a low degree of salmonella contamination which hygienically may be without any importance or to treat every imported fishmeal by irradiation or heat pelleting.

Bacteriological Techniques↗
PubMed1993

[Molecular characterization of the transferable resistance to amikacin in Enterobacteriaceae strains isolated from hospital infections].

Sixty-three amikacin resistant strains of Enterobacteriaceae isolated in three hospitals from Santiago, between 1988 and 1990 were included in this study. The strains were multiresistant and harbored 1-5 plasmids. Fifty six isolates (88.9%) transferred amikacin resistance to E coli C600 receptor strain by conjugation. The transconjugants acquired a 11 kilobase-pair or a larger plasmid. The plasmids also encoded resistance to kanamycin, tobramycin, streptomycin and ampicillin. A DNA probe from the gene AAC (6')-I encoding an aminoglycoside 6'-N-acetyltransferase, AAC (6')-I hybridized in Southern blot with plasmid DNA of the 10 Enterobacteriaceae strains tested, but not with the plasmid DNA of 8 amikacin resistant clinical strains of A baumannii. The results indicate that amikacin resistance in Enterobacteriaceae is due mainly to conjugative plasmids encoding an AAC (6')-I.

Amikacin↗
PubMed1996

The adherence of oral isolates of Enterobacteriaceae to HeLa cells. An in vitro method using image analysis.

An in vitro model and an image analysis were designed to improve on existing quantification methods in the assessment of the adherence of Enterobacteriaceae to human epithelial cell monolayers. Adherence to HeLa cell monolayers of three oral isolates and one type strain from each of four species of Enterobacteriaceae over two incubation time periods was examined. Correction for actual cell area and a cube root transformation of the data to stabilize variance were applied. While behaviour varied between strains within species, E. cloacae was the most, and K. pneumoniae the least, adherent species irrespective of the incubation period. Increasing the incubation period from 30 min to 60 min resulted in greater adherence for E. cloacae, E. coli, and C. freundii, but not K. pneumoniae strains. The method permits the reliable measurement and valid analysis of the adherence of Enterobacteriaceae to cultured epithelial cell monolayers.

Cell Adhesion↗
PubMed1996

In vitro activity of fourth generation cephalosporins against enterobacteriaceae producing extended-spectrum beta-lactamases.

The in vitro activity of fourth generation cephalosporins against Enterobacteriaceae that produce extended-spectrum beta-lactamases (ESBLs) has not been extensively studied. From an examination of the data available in the published literature and from studies performed in the author's laboratory, several trends are apparent. Introduction of any ESBL into Escherichia coli significantly reduces activity. The precise impact of an ESBL on activity varies greatly with the specific ESBL present. Derivatives of SHV-1 tend to decrease activity more than derivatives of TEM-1 or TEM-2 although there is great variation within both of the major types of ESBLs. Activity of fourth generation cephalosporins against clinical isolates of ESBL-producing Enterobacteriaceae is significantly greater than that of ceftazidime. However, cefotaxime shows activity similar to that of fourth generation cephalosporins against certain strains. The value of fourth generation cephalosporins in treating infections due to ESBL-producing Enterobacteriaceae is currently unknown as there are no clinical data available that address this issue.

Cephalosporins↗
PubMed1995

[Evaluation of the usefulness of tests for production of Beta-D-glucuronidase and propylene glycol utilization for the differentiation of enterobacteriaceae rods].

The aim of the study was to inquire about the diagnostic usefulness of determining the activity of glucuronidase and utilisation of propylene glycol in Enterobacteriaceae rods. The study included 1511 strains: 411- E. coli, 278 - Klebsiella, 231 - Salmonella, 159 - Yersinia, 97 - Citrobacter, 75 - Shigella and 260 strains representing 6 other kinds of enteric rods. Determination was performed in a liquid medium containing in 1 ml 25 mcg MUG and 100 mcg ONPG. Propylene glycol (PG) utilisation was observed in peptone water with 2% of the substrate and with the Andrade indicator. In comparative tests Rambach commercial medium and MacConkey agar from the Fluorocult series were used. In the test with MUG a positive result was obtained from 81.8% E. coli, 65% - Shigella and 13% - Salmonella subgenus I. Only exceptionally was this test positive with Providencia, Enterobacter and Yersinia strains (1-5%) but negative with Citrobacter, Klebsiella, Serratia, Hafnia, Proteus and Morganella strains. Glucuronidase production is not sufficiently characteristic of E. coli strains isolated from humans to be the only basis for the preliminary differentiation of these rods from other Enterobacteriaceae. The test with ONPG was positive from 95-100% E. coli, Yersinia, Citrobacter, Klebsiella, Enterobacter and Hafnia strains; 61% - Shigella, 9% - Salmonella and 3% - Providencia, but negative with Serratia, Proteus and Morganella strains. Propylene glycol was decomposed by 74% Salmonella strains of subgenus I, 65-94% - Klebsiella, Yersinia and Citrobacter. Shigella, Enterobacter, Serratia, Proteus, Providencia and Morganella rods did not decompose propylene glycol. Evidence that among strains non-decomposing propylene glycol were all the studied S. typhi, S. paratyphi A, S. paratyphi C, S. choleraesuis, S. virchow and S. gallinarum strains as well as a significant percentage of strains representing 8 other Salmonella serotypes frequently detected allows to believe that the use of activity against propylene glycol even simultaneously with the test for galactosidase as basis for the differentiation of Salmonella rods of subgenus I from other Enterobacteriaceae can lead to errors already at the onset of diagnostic procedure.

Bacterial Typing Techniques↗
PubMedDate not supplied

[Enterobacteriaceae isolated in eastern Romania: the evolution of ampicillin sensitivity in the 1970-1995 period].

The activity of ampicillin against 3383 Enterobacteriaceae (community and clinical isolates), collected in Eastern Romania, during 25 years was tested. Data were prelucrated by the box-plot method proposed by Simpson and Donnelly. The resistance degree for all species tested has progressively increased. In the studied region Enterobacteriaceae strains maintain their natural sensitivity only exceptionally: e.g., S. typhi and S. java, with limited circulation. Enterobacteriaceae which have contact with the resistance genic reservoir of the colon microbiota during the justified or nonjustified antibiotic treatment development resistance to usual antibiotics in the same ratio as most existent commensals present in this habitat.

Ampicillin↗
PubMed1997

[Evaluation of a new and rapid antibiotic sensitivity method testing for Enterobacteriaceae responsible for urinary infections].

URIFAST Es et Es Plus (International Microbio, Signes, France) are rapid antimicrobial susceptibility testing method in broth medium without using an automatic reader. A screening assay (URIFAST Quatro 1C ou URIFAST Twin 1C) is performed with a 4 or 9 antimicrobial agents with a concentration c' below the low critical concentration (c) defined by the Comité de l'Antibiogramme de la Société Française de Microbiologie (CA-SFM). When a bacterial strain is presumed resistant, an antimicrobial susceptibility test with the two critical concentrations (CA-SFM) can be performed with 5 or 10 antimicrobial agents antibiotiques (URIFAST Twin ABG ou URIFAST ABG). 140 strains of Enterobacteriaceae from urinary tract infections; E. coli (n = 94), P. mirabilis (n = 13), K. pneumoniae (n = 4), K. oxytoca (n = 6), C. diversus (n = 3), P. vulgaris (n = 1), M. morganii (n = 3), C. freundii (n = 4), E. aerogenes (n = 2), E. cloacae (n = 5) and S. marcescens (n = 5); were isolated with CPS ID2 (bioMérieux, Marcy l'Etoile, France). URIFAST results were compared to Rapid ATB Ur et ATB Ur results obtained after reading with ATB expression (bioMerieux). For each discrepancy, the minimal inhibitory concentration (MIC) by agar dilution was used as the reference method. Agreement obtained were 98.57% with Quatro 1C, 98.40% with Twin 1C, 98.14% with Twin ABG and 98.39% with ABG. 94% of beta-lactams susceptible Enterobacteriaceae were detected by the screening tray with the antimicrobial agent concentration c'. URIFAST Es et Es Plus are standardized and easy-to-use methods. Because of their good performances, the URIFAST methods can be used to test antimicrobial susceptibility for Enterobacteriaceae from urinary tract infections.

Enterobacteriaceae↗
PubMed1997

[in vitro activity of carbapenems against Enterobacteriaceae and Pseudomonas aeruginosa hyperproducers of group 1 chromosomal beta-lactamases].

Resistance to imipenem and meropenem, reported sporadically in Enterobacteriaceae and more frequently in Pseudomonas aeruginosa, can be caused, among other mechanisms, by the combination of changes in permeability and hyperproduction of inducible chromosomal beta-lactamases. In this study, the in vitro activity of imipenem and meropenem was analysed by the agar dilution method against cefotaxime, ceftazidime, and aztreonam resistant clinical strains of Enterobacteriaceae (n = 202) and P. aeruginosa (n = 90). This phenotype is consistent with the hyperproduction of group 1 chromosomal beta-lactamases and was previously determined in stably derepressed mutants in the same species, obtained from strains with inducible beta-lactamase expression by selection with cefotaxime and ceftazidime. Likewise, the activity of imipenem and meropenem against the same number of clinical isolates susceptible to cefotaxime, ceftazidime, and aztreonam was evaluated. In general, imipenem and meropenem showed an excellent activity, which was intrinsically greater for meropenem against Enterobacteriaceae and P. aeruginosa organisms. Nevertheless, imipenem and meropenem activity was slightly affected on cefotaxime, ceftazidime, and aztreonam resistant isolates of E. cloacae (MIC90, 1 and 0.2 microgram/ml, respectively), E. aerogenes (1 and 0.2 microgram/ml), C. freundii (1 and 0.1 microgram/ml), M. morganii (1 and 0.5 microgram/ml), and S. marcescens (4 and 0.5 micrograms/ml). On the other hand, the activity of imipenem and meropenem against ceftazidime and aztreonam resistant isolates of P. aeruginosa was more significantly affected, with MIC90 values of 64 and 16 micrograms/ml, respectively.

Enterobacteriaceae↗
PubMedDate not supplied

Comparison of the VITEK Gram-Negative Identification Card and an enhanced version for identification of Salmonella, Escherichia coli, and other Enterobacteriaceae: method modification.

The VITEK Gram-Negative Identification Card (GNI) was compared to an enhanced version of the test kit, the GNI + Card. The GNI Card is an official AOAC method (991.13) for identification of Salmonella, Escherichia coli, and other Enterobacteriaceae in foods. In this comparison 5 replicates of 124 gram-negative stock culture strains were evaluated to determine equivalency. Isolates were obtained primarily from food sources, with 108 of the isolates representing 15 genera within the family Enterobacteriaceae. Overall agreement between the GNI Card and the GNI + Card was 98.2%. Of the 23 strains of Salmonella tested, the longest identification time for the GNI Card was 10 h, with 43.5% of the strains identifying in 4 h or less. The longest identification time of the same Salmonella strains tested with the GNI + Card was 8 h, with 95.7% of the strains identifying within 4 h. The GNI + Card provided increased speed of identification while retaining the accuracy of the GNI Card. The GNI method for identifying Salmonella, Escherichia coli, and other Enterobacteriaceae was approved as a method modification by AOAC INTERNATIONAL.

Animals↗
PubMed2002

Effect of fermented feed on shedding of Enterobacteriaceae by fattening pigs.

Epidemiological studies showed that the use of fermented feed could significantly reduce Salmonella prevalence in pigs compared to the use of normal feed. Experimental challenge experiments with Salmonella have however never been conducted to reveal the efficacy of fermented feed in reducing Salmonella shedding and/or reducing the number of Salmonella-positive pigs. A longitudinal study was conducted to measure the effect of fermented feed, in particular of its components lactic acid and Lactobacillus plantarum, on gastrointestinal bacterial ecology (Salmonella, Enterobacteriaceae, lactobacilli, volatile fatty acids (VFAs), pH). Seeder pigs were used as a mode for Salmonella transmission within a pig herd. Bacteriological measurements were performed in faeces of the pigs. The results showed that fermented feed affected/reduced the Enterobacteriaceae population in faeces of the pigs. No differences were found in the number of positive pigs infected or in the number of shedding with Salmonella serovar Typhimurium fed fermented feed and between the normal feed group. S. serovar Goldcoast could not establish an infection in the seeder pigs in the fermented feed group as well as in the normal feed group. The pH of the faeces in the fermented feed groups was significantly higher than the pH of the faeces of the normal feed groups. The role of the undissociated form of the faecal VFAs on the significantly lower Enterobacteriaceae number in faeces of the pigs of the fermented feed groups could not be demonstrated because of the significant higher pH in the faeces of the pigs fed fermented feed.

Animal Feed↗
PubMed2004

Prevalence and characterization of integrons in blood culture Enterobacteriaceae and gastrointestinal Escherichia coli in Norway and reporting of a novel class 1 integron-located lincosamide resistance gene.

BACKGROUND: Class 1 integrons contain genetic elements for site-specific recombination, capture and mobilization of resistance genes. Studies investigating the prevalence, distribution and types of integron located resistance genes are important for surveillance of antimicrobial resistance and to understand resistance development at the molecular level. METHODS: We determined the prevalence and genetic content of class 1 integrons in Enterobacteriaceae (strain collection 1, n = 192) and E. coli (strain collection 2, n = 53) from bloodstream infections in patients from six Norwegian hospitals by molecular techniques. Class 1 integrons were also characterized in 54 randomly selected multiresistant E. coli isolates from gastrointestinal human infections (strain collection 3). RESULTS: Class 1 integrons were present in 10.9% of the Enterobacteriaceae blood culture isolates of collection 1, all but one (S. Typhi) being E. coli. Data indicated variations in class 1 integron prevalence between hospitals. Class 1 integrons were present in 37% and 34% of the resistant blood culture isolates (collection 1 and 2, respectively) and in 42% of the resistant gastrointestinal E. coli. We detected a total of 10 distinct integron cassette PCR amplicons that varied in size between 0.15 kb and 2.2 kb and contained between zero and three resistance genes. Cassettes encoding resistance to trimethoprim and aminoglycosides were most common. We identified and characterized a novel plasmid-located integron with a cassette-bound novel gene (linF) located downstream of an aadA2 gene cassette. The linF gene encoded a putative 273 aa lincosamide nucleotidyltransferase resistance protein and conferred resistance to lincomycin and clindamycin. The deduced LinF amino acid sequence displayed approximately 35% identity to the Enterococcus faecium and Enterococcus faecalis nucleotidyl transferases encoded by linB and linB' CONCLUSIONS: The present study demonstrated an overall low and stable prevalence of class 1 integron gene cassettes in clinical Enterobacteriaceae and E. coli isolates in Norway. Characterization of the novel lincosamide resistance gene extends the growing list of class 1 integron gene cassettes that confer resistance to an increasing number of antibiotics.

Journal Article↗
PubMed1993

Adverse perinatal outcome and resistant Enterobacteriaceae after antibiotic usage for premature rupture of the membranes and group B streptococcus carriage.

OBJECTIVE: To report a case series of adverse perinatal outcomes associated with resistant Enterobacteriaceae after antibiotic usage for premature rupture of the membranes (PROM) and group B streptococcus. METHODS: Maternal and neonatal records were reviewed of four cases in which adverse perinatal outcomes occurred from resistant Enterobacteriaceae after antibiotic usage for either PROM or positive group B streptococcal cultures. Information on clinical setting, antibiotic usage, maternal and neonatal complications, and maternal and neonatal cultures was noted. RESULTS: All four cases were complicated by PROM at 25-35 weeks' gestation. Ampicillin or amoxicillin was used in several clinical settings, including therapeutically for the presence of group B streptococcus, presumptively for PROM, and prophylactically pending the results of group B streptococcal cultures. Clinical chorioamnionitis subsequently developed in all four cases, and in two cases the maternal course was prolonged and complicated by persistent fever and the need for therapy for pelvic vein thrombophlebitis. Two neonates died from fulminant clinical sepsis. A third infant, one of a twin gestation, was stillborn, presumably because of sepsis. In three cases, neonatal and placental cultures revealed Escherichia coli resistant to ampicillin; in the fourth case, Klebsiella pneumoniae was identified, with only intermediate sensitivity to ampicillin. CONCLUSION: Resistant Enterobacteriaceae associated with adverse perinatal outcomes may result from the use of antibiotics, such as ampicillin or amoxicillin, after PROM. In deciding whether antibiotic therapy for PROM or group B streptococcal prophylaxis is appropriate, the value of purported benefits must be weighed against presumably infrequent but serious outcomes, including neonatal sepsis and death due to selection or overgrowth of resistant organisms.

Amoxicillin↗
PubMed2000

Enterobacter cowaniisp. nov., a new species of the family Enterobacteriaceae.

The name Enterobacter cowanii sp. nov. is proposed for a group of organisms referred to as NIH Group 42. Members of this species are Gram-negative, motile rods conforming to the definition of the family Enterobacteriaceae. The DNA relatedness of nine strains of NIH Group 42 to the proposed type strain of this species averaged 85% at 70 degrees C, whereas the relatedness to other species within the family Enterobacteriaceae was less than 38%. Because the DNA relatedness (5-38%) is closer to species of the genus Enterobacter than to other species of the family, the members of NIH Group 42 were placed in the genus Enterobacter. The majority of strains of E. cowanii were isolated from clinical specimens. A culture of the type strain (888-76) has been deposited in the Japan Collection of Microorganisms as JCM 10956.

Bacterial Typing Techniques↗
PubMed2005

Reevaluation of the cefepime minimal inhibitory concentrations and disk diffusion test zone diameter relationship for a worldwide collection of Enterobacteriaceae enriched for extended-spectrum beta-lactamase-producing organisms.

To reassess the validity of existing susceptibility breakpoint criteria and to propose alternative breakpoint criteria for disk diffusion testing at lower susceptible MIC breakpoints, we analyzed a contemporary global collection of Enterobacteriaceae isolates (350) strains enriched for extended-spectrum beta-lactamase (ESBL) producers (68 strains, 19.4%). The majority of the isolates (88.3% of the entire collection and 83.8% of the ESBL subset) were from bloodstream infections. Cefepime minimal inhibitory concentrations (MICs) were determined by broth microdilution methods and compared with the results obtained from disk diffusion testing for the entire collection of Enterobacteriaceae and for the ESBL subset alone. The regression coefficient was excellent for both scattergrams (r = 0.92-0.94). The intermethod categorical agreement remained excellent for the current breakpoints (susceptible at < or = 8 microg/mL or > or = 18 mm and resistant at > or = 32 microg/mL or < or = 14 mm) published by the National Committee for Clinical Laboratory Standards at 94.0%. The 2 alternative interpretive criteria considered at lower MIC breakpoints (i.e., susceptible as < or = 4 microg/mL and > or = 21 mm and susceptible as < or = 2 microg/mL and > or = 24 mm) did not compromise the intermethod test categorical accuracy, which remained excellent at 96.9% and 94.0%, respectively. Adopting the existing breakpoint criteria that remain accurate for ESBL-producing strains or any one of the above two alternative sets of breakpoint criteria analyzed would be acceptable, with excellent intermethod concordance between the MIC and disk diffusion results.

Anti-Bacterial Agents↗
PubMed2005

Susceptibility testing accuracy of a CTX-M-type extended-spectrum beta-lactamase organism-producing population of Enterobacteriaceae: intermethod analysis for 9 beta-lactams.

To assess the wide geographical applicability of the current and proposed susceptibility breakpoint criteria for 9 beta-lactam antimicrobials, the performance characteristics of 2 standardized methods were analyzed by testing a contemporary collection of 354 isolates of Enterobacteriaceae, enriched (76; 21.5%) for extended-spectrum beta-lactamase (ESBL)-producing strains. Molecular characterization of 57 ESBL strains revealed that majority of the strains (94.7%) were CTX-M type, with a predominance (85.2%) of CTX-M-14 and -3 types, those types prevalent in China. Bloodstream isolates constituted 68.6% of the entire collection. The 9 beta-lactam antimicrobials analyzed were aztreonam, cefepime, cefotaxime, cefotetan, cefoxitin, ceftazidime, ceftriaxone, ceftizoxime, and cefuroxime. Reference broth microdilution minimal inhibitory concentration (MIC) results were compared to those zone diameters obtained by disk diffusion testing. The regression coefficient was acceptable for most antimicrobials, ranging from r = 0.84 (cefotetan) to r = 0.98 (cefotaxime, cefuroxime, and ceftriaxone). Using the current breakpoint criteria, the absolute intermethod categorical agreement was acceptable for 8 of the 9 antimicrobials (not cefoxitin, 85.1%) ranging from 92.6% (cefotaxime) to 97.8% (ceftazidime). Very major (false-susceptible) and major (false-resistant) errors were nil (0.0%) for 5 of the beta-lactams and minor errors ranged from 0.8% (cefotetan) to 14.1% (cefoxitin). The proposed (generally lower) MIC breakpoint criteria also had acceptable intermethod concordance ranging from 91.6% (cefoxitin) to 99.2% (cefotaxime and ceftriaxone). Furthermore, an improvement in the intermethod absolute categorical agreement ranging from +0.8% (ceftazidime) to +6.6% (cefotaxime) was observed for 7 of 9 antimicrobials tested, including the ESBL screening test compounds (aztreonam, ceftazidime, cefotaxime, and ceftriaxone). No modification of the susceptible breakpoint criteria, with removal of the intermediate category, was proposed for cefoxitin and cefuroxime, resulted in a shift of error type from minor to major or very major, but the categorical agreement improved (+ >or=1.2%) for both cephems. In conclusion, our results confirm that both the current and the proposed MIC breakpoint criteria with appropriately selected zone diameter correlates have acceptable intermethod error rates even when tested against an Enterobacteriaceae collection enriched with CTX-M-type ESBL-producing strains that are endemic in locations (China) outside the United States.

Anti-Bacterial Agents↗