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PubMed1989

In vitro evaluation of BRL 42715, a novel beta-lactamase inhibitor.

The penem BRL 42715, C6-(N1-methyl-1,2,3-triazolylmethylene)penem, is a potent inhibitor of a broad range of bacterial beta-lactamases, including the plasmid-mediated TEM, SHV, OXA, and staphylococcal enzymes, as well as the chromosomally mediated enzymes of Bacteroides, Enterobacter, Citrobacter, Serratia, Morganella, Escherichia, Klebsiella, and Proteus species. The concentration of BRL 42715 needed to reduce the initial rate of hydrolysis of most beta-lactamase enzymes by 50% was less than 0.01 micrograms/ml, which was 10- to 100-fold lower than for other beta-lactamase inhibitors. These potent inhibitory activities were reflected in the low concentrations of BRL 42715 needed to potentiate the antibacterial activity of beta-lactamase-susceptible beta-lactams. Concentrations of 0.25 micrograms/ml or less considerably enhanced the activity of amoxicillin against many beta-lactamase-producing strains. The MIC50 (MIC for 50% of strains tested) of amoxicillin for 412 beta-lactamase-producing members of the family Enterobacteriaceae fell from greater than 128 to 2 micrograms/ml in the presence of 1 microgram of BRL 42715 per ml, whereas 5 micrograms of clavulanic acid per ml brought the MIC50 down to 8 micrograms/ml. Among these 412 strains were 73 Citrobacter and Enterobacter strains, and 1 microgram of BRL 42715 per ml reduced the MIC50 of amoxicillin from greater than 128 to 2 micrograms/ml for the 48 cefotaxime-susceptible strains and from greater than 128 to 8 micrograms/ml for the 25 cefotaxime-resistant strains.

Amoxicillin↗
PubMed1990

In vitro activity of sparfloxacin (CI-978; AT-4140) against clinical isolates from cancer patients.

The in vitro activity of sparfloxacin, a new quinolone, was compared with those of ciprofloxacin and fleroxacin against gram-positive and gram-negative bacteria, greater than 90% of which were isolated from blood culture specimens of cancer patients. Sparfloxacin was extremely active against Acinetobacter species, Aeromonas hydrophila, Citrobacter diversus, Enterobacter species, Escherichia coli, Klebsiella species, Proteus vulgaris, and Serratia marcescens (inhibiting greater than 90% of these isolates at a concentration of 0.5 microgram/ml) and moderately active against Pseudomonas species, other Proteus species, and Citrobacter freundii. Sparfloxacin inhibited greater than 90% of staphylococci (including methicillin-resistant and coagulase-negative strains) at a concentration of 0.12 microgram/ml and greater than 90% of streptococci (including Streptococcus pneumoniae) at a concentration of 1.0 microgram/ml. It was also active against Bacillus cereus, Enterococcus species, and Corynebacterium jeikeium, organisms that have become fairly common in cancer patients.

Anti-Infective Agents↗
PubMed1990

In vitro activity of Ro 23-9424, a dual-action cephalosporin, compared with activities of other antibiotics.

The in vitro activity of Ro 23-9424, which is desacetyl-cefotaxime linked to fleroxacin, was compared with the activities of cefotaxime, desacetyl-cefotaxime, fleroxacin, ofloxacin, and ciprofloxacin. It inhibited the majority of members of the family Enterobacteriaceae, except for some Serratia marcescens, Citrobacter freundii, and Enterobacter cloacae strains, at less than or equal to 0.25 microgram/ml and had an MIC for 90% of strains tested (MIC90) of 8 micrograms/ml against Pseudomonas aeruginosa. Most group A, B, C, and G streptococci and Streptococcus pneumoniae were inhibited at less than or equal to 0.25 microgram/ml. Ninety percent of the staphylococci were inhibited at less than or equal to 4 micrograms/ml, except for some methicillin-resistant Staphylococcus aureus isolates. The MIC90S of Ro 23-9424 for Enterococcus faecalis and Listeria monocytogenes were greater than or equal to 16 micrograms/ml. Ninety percent of Clostridium perfringens isolates were inhibited by less than or equal to 2 micrograms/ml, whereas Bacteroides fragilis had an MIC90 of 32 micrograms/ml. There was a minimal inoculum size effect. The MICs and MBCs were either identical or within a twofold dilution. The MICs of Ro 23-9424 for Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, Enterobacter cloacae, Citrobacter freundii, Pseudomonas aeruginosa, and Staphylococcus aureus increased 16- to 128-fold after 2 weeks of transfer in the presence of Ro 23-9424, showing that the presence of two agents does not prevent resistance.

Anti-Bacterial Agents↗
PubMed1991

In vitro activity and beta-lactamase stability of GR69153, a new long-acting cephalosporin.

GR69153, a new parenteral cephalosporin, inhibited 90% of Escherichia coli, Klebsiella oxytoca, Proteus mirabilis, Citrobacter diversus, shigellae, and salmonellae at less than 0.25 micrograms/ml (MIC90). It had activity comparable to those of ceftazidime, cefpirome, cefepime, and E-1040. Against cephalosporinase-producing Enterobacter cloacae, Citrobacter freundii, and Serratia marcescens, MICs ranged from 0.12 to greater than 32 micrograms/ml, and cefpirome and cefepime were the most active agents against these species. Pseudomonas aeruginosa was highly susceptible to GR69153, and for this organism the MIC90 was less than or equal to 2 micrograms/ml, which was similar to the E-1040 MIC90, but most Pseudomonas cepacia and Xanthomonas maltophilia isolates were resistant. GR69153 inhibited Haemophilus influenzae and Moraxella branhamella at less than or equal to 0.5 micrograms/ml. For Staphylococcus aureus GR69153 MICs were similar to those of ceftazidime and E-1040. Enterococci and listeriae were resistant to GR69153, but Streptococcus pyogenes and Streptococcus pneumoniae were inhibited by 0.5 micrograms/ml. The activity of GR69153 was not affected by serum. GR69153 was not inactivated by the beta-lactamases of Staphylococcus aureus, TEM-1, TEM-2, SHV-1, and BRO-1, but it was hydrolyzed by TEM-3, TEM-9, and morganellae. GR69153 had overall activity comparable to those of commercially available parenteral cephalosporins or those found in clinical investigations. It is more active against bacteroides than most available aminothiazolyl parenteral cephalosporins are. GR69153 is hydrolyzed by the new plasmid beta-lactamases, and thus, its primary value may be related to its pharmacological properties.

Cephalosporins↗
PubMed1997

Antibacterial activity of BMS-180680, a new catechol-containing monobactam.

The in vitro activities of a new catechol-containing monobactam, BMS-180680 (SQ 84,100), were compared to those of aztreonam, ceftazidime, imipenem, piperacillin-tazobactam, ciprofloxacin, amikacin, and trimethoprim-sulfamethoxazole. BMS-180680 was often the most active compound against many species of the family Enterobacteriaceae, with MICs at which 90% of the isolates were inhibited (MIC90s) of < or = 0.5 microg/ml for Escherichia coli, Klebsiella spp., Citrobacter diversus, Enterobacter aerogenes, Serratia marcescens, Proteus spp., and Providencia spp. BMS-180680 had moderate activities (MIC90s of 2 to 8 microg/ml) against Citrobacter freundii, Morganella morganii, Shigella spp., and non-E. aerogenes Enterobacter spp. BMS-180680 was the only antibiotic evaluated that was active against >90% of the Pseudomonas aeruginosa (MIC90, 0.25 microg/ml), Burkholderia cepacia, and Stenotrophomonas maltophilia (MIC90s, 1 microg/ml) strains tested. BMS-180680 was inactive against most strains of Pseudomonas fluorescens, Pseudomonas stutzeri, Pseudomonas diminuta, and Burkholderia pickettii. BMS-180680 was moderately active (MIC90s of 4 to 8 microg/ml) against Alcaligenes spp. and Acinetobacter lwoffii and less active (MIC90, 16 microg/ml) against Acinetobacter calcoaceticus-Acinetobacter baumanii complex. BMS-180680 lacked activity against gram-positive bacteria and anaerobic bacteria. Both tonB and cir fiu double mutants of E. coli had greatly decreased susceptibility to BMS-180680. Of the TEM, PSE, and chromosomal-encoded beta-lactamases tested, only the K1 enzyme hydrolyzed BMS-180680 to any measurable extent. Like aztreonam, BMS-180680 bound preferentially to penicillin-binding protein 3. The MICs of BMS-180680 were not influenced by the presence of hematin or 5% sheep blood in the test medium or with incubation in an atmosphere containing 5% CO2. BMS-180680 MICs obtained under strict anaerobic conditions were significantly higher than those obtained in ambient air.

Anti-Bacterial Agents↗
PubMed2000

Levofloxacin pharmacokinetics and serum bactericidal activities against five enterobacterial species.

After oral administration of 500 mg of levofloxacin to 12 volunteers, we investigated the pharmacokinetics and serum bactericidal activities (SBAs) against five strains of members of the family Enterobacteriaceae. Pharmacokinetic data were as follows: maximum concentration in serum, 6.36 +/- 0.57 mg/liter; area under the concentration-time curve, 43.6 +/- 6.23 mg. h/liter; elimination half-life 4.23 +/- 0.87 h. SBAs were present for 24 h against Escherichia coli and Citrobacter freundii. The SBAs at 1, 12, and 24 h after administration against E. coli were 1:108, 1:29, and 1:7, respectively, and those against Citrobacter freundii were 1:74, 1:25, and 1:7, respectively. The SBAs were present for 12 h against the other three organisms tested. The SBAs against Serratia marcescens were 1:28 and 1:9 at 1 and 12 h, respectively; the SBAs against Klebsiella pneumoniae were 1:25 and 1:7 at 1 and 12 h, respectively; and the SBAs against Enterobacter cloacae were 1:24 and 1:10 at 1 and 12 h, respectively.

Adult↗
PubMed1976

Observations on brilliant green agar with H2S indicator.

Several formulations of brilliant green agar with an added H2S indicator were evaluated. Results were optimum with variations of a basic formula consisting of 40 g of tryptic soy agar (Difco), 8 g of lactose, 8 g of sucrose, 80 mg of phenol red, 1 g of sulfanilamide, 1.5 g of ferric ammonium citrate, 5 g of sodium thiosulfate pentahydrate, and 7 mg of brilliant green dye per liter. Brilliant green dye was added after sterilization of the other components This formulation supported good growth of all of 39 strains of Salmonella tested. Normal biochemical types formed pink colonies with black centers, and an H2S-negative S. choleraesuis formed pink colonies without black centers. Of other bacteria tested, only Enterobacter, Klebsiella, and a few Citrobacter strains showed significant growth in 24 h. When lactose was omitted from the formulation, a lactose-fermenting strain formed pink colonies with black centers, and differentiation of Salmonella from the Enterobacter-Klebsiella groups was equally good. Addition of xylose (4.0 g) and L-lysine hydrochloride (5.4 g) to the above formulation improved differentiation between Salmonella and the few Citrobacter strains that grew and produced more intense blackening in Salmonella colonies. Addition of an H2S indicator to brilliant green agar formulations aided in identification of Salmonella colonies, especially in mixtures with other bacteria. These media were judged to give better differentiation of salmonellae from other bacteria than Hektoen agar with added novobiocin (10 mg/liter).

Agar↗
PubMed1976

Acetylene reduction (nitrogen fixation) by enterobacteriaceae isolated from paper mill process waters.

Using selective media containing galactitol, over 130 Enterobacteriaceae have been isolated from paper mill process waters collected from different localities. These bacteria were extensively characterized and tested for acetylene-reducing (nitrogen-fixing) activity under anaerobic conditions. High activity was found in representatives of Klebsiella pneumoniae, Enterobacter aerogenes, Enterobacter cloacae, Erwinia herbicola, Citrobacter freundii, Citrobacter intermedius, and Escherichia coli. Under argon, nitrogenase synthesis was generally not repressed by 5 mM l-glutamate, l-aspartate, l-leucine or Casamino Acids (0.5 g/liter). In many strains, both the specific activities (nanomoles of C(2)H(4) per minute per milligram of protein) and the activities (nanomoles of C(2)H(4) per minute) had considerably declined after 24 h. In three selected strains, activity in intact cells grown under nitrogen was unaffected by the presence during assay of 10 mM l-amino acids or ammonium acetate. All of the strains examined were tolerant towards inactivation of nitrogen-fixing activity by 1.8% (vol/vol) oxygen during assay, and inactivation by up to 10% oxygen was partly reversible. Representatives of the six taxa synthesized nitrogenase in stirred aerobic cultures, though the protein concentrations attained were lower than under anaerobic conditions. It seems reasonable to suggest that under natural conditions, nitrogen fixation is able to contribute significantly to the nitrogen economy of the cells.

Journal Article↗
PubMed1978

Heterotrophic bacteria present in hindguts of wood-eating termites [Reticulitermes flavipes (Kollar)].

Strict anaerobic culture techniques were used to quantitate heterotrophic bacteria present in hindguts of Reticulitermes flavipes. The grand mean number of viable cells per hindgut was 0.4 X 10(5) (first-instar larvae), 1.3 X 10(5) (third-instar larvae), 3.5 X 10(5) (workers), and 1.5 X 10(5) (soldiers). Of a total of 344 isolates, 66.3% were streptococci that were always obtained regardless of the origin of termites, their developmental stage or caste, or their length of captivity. Most of the remaining isolates were strains of Bacteroides and Enterobacteriaceae. A small percentage were strains of Lactobacillus, Fusobacterium, and unidentified anaerobic gram-positive rods. Recovery of bacteria from worker hindguts was 13.0% of the direct microscopic count. Isolations performed aerobically failed to reveal strict aerobes. Attempts to isolate cellulolytic bacteria were uniformly unsuccessful. Of 145 streptococcal strains isolated from freshly collected termites, almost all were Streptococcus lactis and S. cremoris. Enterobacteriaceae isolates from the same termite specimens were indole-positive Citrobacter, citrate-negative Citrobacter, and Enterobacter cloacae. The possibility of in situ interspecies lactate transfer, between lactate producers (e.g., streptococci) and lactate fermenters (Bacteroides), is discussed.

Anaerobiosis↗
PubMed1979

Comparison of EC broth and medium A-1 for the recovery of Escherichia coli from frozen shucked snow crab.

Two variations of the multiple-tube fermentation technique were used to enumerate fecal coliforms in commercially processed, frozen crab meat. These were the EC confirmation test and a more rapid method that requires medium A-1. The method with medium A-1 was more specific than the EC confirmation test for detecting Escherichia coli type 1. E. coli was isolated from 84% of the positive medium A-1 tubes, whereas it was isolated from only 64% of the positive tubes of EC broth. When samples of crab meat were inoculated with known amounts of E. coli, better estimates of the known numbers were obtained by the medium A-1 method. Several species of nonfecal coliforms were isolated from cultures in EC broth. These belonged to the genera Klebsiella, Citrobacter, Enterobacter, and Serratia. Apparently these strains were naturally adapted to growth at an elevated temperature because the majority were able to grow at 44.5 degrees C when retested in EC broth. Fewer species of nonfecal coliforms were isolated from medium A-1. Those that were isolated belonged to the genera Citrobacter and Enterobacter.

Brachyura↗
PubMed1993

Specific detection of Salmonella spp. by multiplex polymerase chain reaction.

Three sets of oligonucleotide primers were used in the polymerase chain reaction (PCR) assay to detect Salmonella species. phoP primers specific to the phoP/phoQ loci of coliform pathogenic bacteria such as Salmonella, Shigella, Escherichia coli, and Citrobacter species served as presumptive indicators of enteric bacteria. In addition to the phoP primers, the Hin and the H-1i primers, which targeted a 236-bp region of hin/H2 and a 173-bp region of the H-1i flagellin gene, respectively, were used. Both Hin and H-1i primers are specific to motile Salmonella species and are not present in Shigella, E. coli, or Citrobacter species. Thus, by multiplex PCR amplification, Salmonella species including Salmonella typhi, Salmonella typhimurium, Salmonella paratyphi A, and Salmonella enteritidis can be specifically detected. Optimal reaction conditions have been described to demonstrate this specific, sensitive detection of Salmonella species. By using agarose gel electrophoresis for detection of the PCR-amplified products, the sensitivity of detection was 10(2) CFU after 25 cycles of PCR and 1 (10(0)) CFU after a 50-cycle double PCR. The efficacy of these primers was demonstrated on environmental isolates which had previously been confirmed as Salmonella species by the use of conventional cultural techniques. In addition, positive amplifications resulted from Salmonella species in environmental samples including soil and water.

Animals↗
PubMed2003

Similarity of tetracycline resistance genes isolated from fish farm bacteria to those from clinical isolates.

Tetracycline-resistant (Tet(r)) bacteria were isolated from fishes collected at three different fish farms in the southern part of Japan in August and September 2000. Of the 66 Tet(r) gram-negative strains, 29 were identified as carrying tetB only. Four carried tetY, and another four carried tetD. Three strains carried tetC, two strains carried tetB and tetY, and one strain carried tetC and tetG. Sequence analyses indicated the identity in Tet(r) genes between the fish farm bacteria and clinical bacteria: 99.3 to 99.9% for tetB, 98.2 to 100% for tetC, 99.7 to 100% for tetD, 92.0 to 96.2% for tetG, and 97.1 to 100% for tetY. Eleven of the Tet(r) strains transferred Tet(r) genes by conjugation to Escherichia coli HB-101. All transconjugants were resistant to tetracycline, oxycycline, doxycycline, and minocycline. The donors included strains of Photobacterium, Vibrio, Pseudomonas, Alteromonas, Citrobacter, and Salmonella spp., and they transferred tetB, tetY, or tetD to the recipients. Because NaCl enhanced their growth, these Tet(r) strains, except for the Pseudomonas, Citrobacter, and Salmonella strains, were recognized as marine bacteria. Our results suggest that tet genes from fish farm bacteria have the same origins as those from clinical strains.

Animals↗
PubMed1972

Selective medium for hydrogen sulfide production by salmonellae.

Triple Sugar Iron Agar does not reveal hydrogen sulfide production by all Salmonella organisms nor does it permit clear-cut separation of those nonsalmonellae which produce H(2)S. Numerous media with varied combinations of nutrients, inhibitors, selective agents, pH levels, and metal salts were tested for H(2)S production of cultures of Salmonella, Citrobacter, Edwardsiella, Arizona, Proteus, Providencia, Klebsiella, and Enterobacter. An agar medium has been devised which promotes growth and H(2)S production (generally within 6 hr) by Salmonella, Arizona, and Edwardsiella but which inhibits hydrogen sulfide production or growth of all other gram-negative organisms tested (including Citrobacter) or inhibits both. The use of this medium should facilitate the selection and identification of Salmonella.

Agar↗
PubMed1976

Kinetic properties of Serratia marcescens adenosine 5'-diphosphate glucose pyrophosphorylase.

The regulatory properties of partially purified adenosine 5'-diphosphate-(ADP) glucose pyrophosphorylase from two Serratia marcescens strains (ATCC 274 and ATCC 15365) have been studied. Slight or negligible activation by fructose-P2, pyridoxal-phosphate, or reduced nicotinamide adenine dinucleotide phosphate (NADPH) was observed. These compounds were previously shown to be potent activators of the ADPglucose pyrophosphorylases from the enterics, Salmonella typhimurium, Enterobacter aerogenes, Enterobacter cloacae, Citrobacter freundii, Escherichia aurescens, Shigella dysenteriae, and Escherichia coli. Phosphoenolpyruvate stimulated the rate of ADPglucose synthesis catalyzed by Serratia ADPglucose pyrophosphorylase about 1.5- to 2-fold but did not affect the S0.5 values (concentration of substrate required for 50% maximal stimulation) of the substrates, alpha-glucose-1-phosphate, and adenosine 5'-triphosphate. Adenosine 5'-monophosphate (AMP), a potent inhibitor of the enteric ADPglucose pyrophosphorylase, is an effective inhibitor of the S. marcescens enzyme. ADP also inhibits but is not as effective as AMP. Activators of the enteric enzyme counteract the inhibition caused by AMP. This is in contrast to what is observed for the S. marcescens enzyme. Neither phosphoenolpyruvate, fructose-diphosphate, pyridoxal-phosphate, NADPH, 3-phosphoglycerate, fructose-6-phosphate, nor pyruvate effect the inhibition caused by AMP. The properties of the S. marcescens HY strain and Serratia liquefaciens ADPglucose pyrophosphorylase were found to be similar to the above two S. marcescens enzymes with respect to activation and inhibition. These observations provide another example where the properties of an enzyme found in the genus Serratia have been found to be different from the properties of the same enzyme present in the enteric genera Escherichia, Salmonella, Shigella, Citrobacter, and Enterobacter.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1986

Conservation of DNA sequences for plasmid-mediated citrate utilization within the enterobacteria.

Southern blot DNA-DNA hybridization experiments with a cloned Cit+ DNA fragment as a probe showed that the plasmid-mediated Cit+ determinants from four Cit plasmids (R726, pOH3001, pOH3035, and pOH30221) were all homologous. Sequences homologous to the plasmid-borne Cit+ gene were also found in total bacterial DNA isolated from Salmonella paratyphi B, Salmonella enteritidis, Salmonella typhimurium LT-2, Citrobacter freundii, ATCC 8090, Citrobacter amalonaticus ATCC 25405, Klebsiella pneumoniae I and IID 977, and Enterobacter aerogenes ATCC 13048. The DNA digest from C. amalonaticus ATCC 25405 contained a 1.4-kilobase BamHI-HincII DNA fragment that was strongly homologous with and identical in size to the plasmid Cit+ probe.

Base Sequence↗
PubMed1991

Evolution of the ferric enterobactin receptor in gram-negative bacteria.

Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis of iron-deficient and replete cell envelopes, 59Fe-siderophore uptake studies, and Western immunoblots and cytofluorimetric analyses with monoclonal antibodies (MAbs), we surveyed a panel of gram-negative bacteria to identify outer membrane proteins that are structurally related to the Escherichia coli K-12 ferric enterobactin receptor, FepA. Antibodies within the panel identified FepA epitopes that are conserved among the majority of the bacteria tested, as well as epitopes present in only a few of the strains. In general, epitopes of FepA that are buried in the outer membrane bilayer were more conserved among gram-negative bacteria than epitopes that are exposed on the bacterial cell surface. The surface topology and tertiary structure of FepA are quite similar in E. coli and Shigella flexneri but differ in Salmonella typhimurium. Of the 18 different genera tested, 94% of the bacteria transported ferric enterobactin, including members of the previously unrecognized genera Citrobacter, Edwardsiella, Enterobacter, Haemophilus, Hafnia, Morganella, Neisseria, Proteus, Providencia, Serratia, and Yersinia. The ferric enterobactin receptor contains at least one buried epitope, recognized by MAb 2 (C. K. Murphy, V. I. Kalve, and P. E. Klebba, J. Bacteriol. 172:2736-2746, 1990), that is conserved within the structure of an iron-regulated cell envelope protein in all the bacteria that we have surveyed. With MAb 2, we identified and determined the Mr of cell envelope antigens that are immunologically related to E. coli FepA in all the gram-negative bacteria tested. Collectively, the library of anti-FepA MAbs showed unique patterns of reactivity with the different bacteria, allowing identification and discrimination of species within the following gram-negative genera: Aeromonas, Citrobacter, Edwardsiella, Enterobacter, Escherichia, Haemophilus, Hafnia, Klebsiella, Morganella, Neisseria, Proteus, Providencia, Pseudomonas, Salmonella, Serratia, Shigella, Vibrio, and Yersinia.

Amino Acid Sequence↗
PubMed1967

Release of surface enzymes in Enterobacteriaceae by osmotic shock.

The process of osmotic shock, which has been used to release degradative enzymes from Escherichia coli, can be applied successfully to other members of the Enterobacteriaceae. Cyclic phosphodiesterase (3'-nucleotidase), 5'-nucleotidase (diphosphate sugar hydrolase), acid hexose phosphatase, and acid phenyl phosphatase are released from Shigella, Enterobacter, Citrobacter, and Serratia strains. Some strains of Salmonella also release these enzymes. Members of Proteus and Providencia groups fail to release enzymes when subjected to osmotic shock and do not show a lag in regrowth, although they do release their acid-soluble nucleotide pools. In contrast to E. coli, release of enzymes from other members of the Enterobacteriaceae studied is affected by growth conditions and strain of organism. None of the organisms was as stable to osmotic shock in exponential phase of growth as was E. coli. Exponential-phase cells of Shigella, Enterobacter, and Citrobacter could be shocked only with 0.5 mm MgCl(2) to prevent irreparable damage to the cells. These observations suggest that this group of degradative enzymes is probably loosely bound to the cytoplasmic membrane through the mediation of divalent cations.

Acid Phosphatase↗
PubMed2006

Evaluation of a new selective chromogenic agar medium for detection of extended-spectrum beta-lactamase-producing Enterobacteriaceae.

A novel chromogenic agar medium (ESBL-Bx; bioMérieux, Marcy l'Etoile, France) was compared to MacConkey agar supplemented with 2 mg ceftazidime/liter (MCKC) for the selective isolation and presumptive identification of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae directly from clinical samples. Of a total of 644 clinical specimens (including 551 fecal samples), 496 yielded no growth and 148 yielded growth on one or both media. Overall, 44 ESBL-producing Enterobacteriaceae strains (Escherichia coli [n=17], Enterobacter aerogenes [n=17], Klebsiella spp. [n=5], and Citrobacter freundii [n=5]) were isolated from 37 specimens by a combination of both methods after 18 to 24 h of incubation. The sensitivities were 97.7 and 84.1% for ESBL-Bx and MCKC, respectively, with 43 ESBL-positive strains isolated as colored colonies from 36 specimens on ESBL-Bx versus 37 ESBL-positive organisms isolated from 32 specimens on MCKC. The specificities by specimens were 89 and 91% for ESBL-Bx and MCKC, respectively. On either one of the two media, natural AmpC-hyperproducing Enterobacter spp. (n=25) and Citrobacter spp. (n=14) were the most common false positives as well as non-ESBL-producing Klebsiella oxytoca (n=18) on ESBL-Bx and Morganella morganii (n=10) on MCKC. We conclude that ESBL-Bx is a sensitive and specific medium for the isolation of ESBL-producing Enterobacteriaceae from clinical samples. The main advantages of ESBL-Bx over MCKC reside in its chromogenic character and its sensitivity and selectivity, which enabled the recovery and presumptive identification of most ESBL-producing Enterobacteriaceae within 24 h and reduced by 27% the need for unnecessary identification and confirmation of ESBL testing when disregarding all colorless colonies growing on this medium.

Agar↗