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PubMed1997

Infectious crystalline keratopathy caused by gram-negative bacteria.

PURPOSE: To identify the characteristics and outcomes of infectious crystalline keratopathy caused by gram-negative bacteria. METHODS: We reviewed all patients treated at a university eye center for infectious crystalline keratopathy from 1978 through 1995 and performed a nested case-comparison study by comparing patients with keratitis caused by gram-negative rods and those with keratitis caused by gram-positive cocci. RESULTS: Eighteen patients (mean age +/- SD, 59 +/- 17 years) displayed unilateral culture-positive infectious crystalline keratopathy. Among 18 eyes with crystalline keratopathy, five occurrences (28%) were caused by gram-negative rods (Acinetobacter lwoffi, Citrobacter koseri, Enterobacter aerogenes, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia), 10 (55%) were caused primarily by gram-positive cocci, and three (17%) were caused primarily by yeasts. Four cases grew two different isolates. No significant difference in predisposing factors, clinical appearance, or visual outcome was found between infections caused by gram-negative bacteria and those caused by gram-positive bacteria. CONCLUSIONS: Gram-negative bacteria can cause infectious crystalline keratopathy but have no distinguishing features from infectious crystalline keratopathy caused by streptococci and other gram-positive bacteria. Appropriate laboratory evaluation is therefore necessary to guide specific antimicrobial therapy.

Aged↗

PubMed1988

Cefotetan: a review of the microbiologic properties and antimicrobial spectrum.

Cefotetan (formerly ICI 156834 and YM09330) is a 7-methoxy cephalosporin possessing some advantageous antimicrobial spectrum, safety, and pharmacokinetic characteristics compared with other so-called second-generation cephalosporins. The published literature was reviewed and the cefotetan quantitative susceptibility testing data from nearly 31,000 isolates was tabulated. Against 15,769 enteric bacilli, cefotetan was observed to have a potency and spectrum more closely resembling a third-generation cephalosporin and markedly superior to cefoxitin. The mean of all MIC 90s reported for the Enterobacteriaceae ranged from 0.06 to 13 micrograms/ml except for citrobacter species, E. cloacae, Enterobacter species, and C. freundii. The mean MIC 50 for all 22 recorded species was in the susceptible range. Cefotetan was very effective against B. catarrhalis, H. influenzae, and pathogenic Neisseria species. However, cefotetan and cefoxitin were not active against Pseudomonas species, Acinetobacter species, and some rarely isolated species. Cefotetan was moderately active against the staphylococci (mean MIC 50, 7.6 to 26 micrograms/ml) and streptococci (mean MIC 50, 0.9 to 6.6 micrograms/ml). The coagulase-negative staphylococcus species generally had higher cefotetan and cefoxitin minimum inhibitory concentrations compared with the S. aureus isolates. Oxacillin-resistant staphylococci were resistant to cefotetan. The enterococci, JK group diphtheroids, Corynebacterium species, and L. monocytogenes isolates were resistant. A review of 4,751 strict anaerobes showed cefotetan to have a very comparable activity and spectrum to cefoxitin. The 1,291 B. fragilis strains had a mean MIC 50 and MIC 90 of 5.4 and 23 micrograms/ml, respectively. These values were slightly superior to cefoxitin when tested in parallel. More elevated minimum inhibitory concentrations were observed for other B. fragilis group species for cefoxitin and cefotetan. The mean cefotetan MIC 90 for all other anaerobic bacteria except the Eubacterium species and Lactobacillus species predict favorable clinical efficacy. The beta-lactamase stability of cefotetan is very similar to that of other 7-methoxy cephalosporins. Cefotetan also inhibits Type Ia cephalosporinases with high enzyme affinity and is an inducer of these beta-lactamases, although cefotetan is not rapidly hydrolyzed. Synergy between cefotetan and numerous other antibiotics has been reported, but antagonism has also been occasionally observed.

Bacteria, Anaerobic↗

PubMed1986

Ultrasonic irradiation of bacterial polysaccharides. Characterization of the depolymerized products and some applications of the process.

Ultrasonic irradiation (u.i.) has been used to depolymerize biopolymers including DNA, dextran, and the Vi capsular polysaccharide from Citrobacter freundii. Representative bacterial polysaccharides were subjected to u.i. and the effect of this energy upon their molecular weight and chemical structure was characterized. U.i. depolymerized a neutral polysaccharide (dextran) and acidic polysaccharides containing either a phosphoric diester linkage [Haemophilus influenzae type b (Hib) and pneumococcus types 6A and 6B] or a uronic acid moiety (pneumococcus type 9N). Prolonged u.i. depolymerized all the polysaccharides to a finite and similar molecular mass (approximately 50 000 daltons). The rate of depolymerization induced by u.i. depended on the viscosity of the solvent and the concentration of the polysaccharide. 13C-N.m.r. data of the native Hib polysaccharide and its depolymerized products indicated that u.i. did not alter the chemical structure of the repeating units. Determination of the monophosphate terminal residues by 31P-n.m.r. spectroscopy and of the reducing end groups by the Park-Johnson reaction indicated that both the phosphoric diester and the glycosidic linkages were cleaved. The Vi polysaccharide, prepared as an investigational vaccine, could not be analyzed for its chemical structure by 13C-n.m.r. spectroscopy owing to its high viscosity but depolymerization by u.i. permitted this analysis. The finite molecular weight of the products observed after prolonged u.i. is best explained by the postulation that the mechanical torque necessary to rupture the linkages is dependent upon the length of the polysaccharide. The method of u.i. for depolymerization is useful for the preparation of homogeneous, low-molecular-weight polysaccharides without alteration of the chemical structure of the repeating units.

Carbohydrates↗

PubMed1987

Bacterial survey of well water--Tehran, Iran.

One hundred twenty-one wells throughout the city of Tehran were monitored during the four seasons of the year for the presence of bacterial indicators of fecal pollution. None of the sites monitored was connected to Tehran's main water distribution system but represented drinking water sources for small communities, individual factories, hospitals, etc. Only 17 samples showed no indication of fecal bacterial contamination throughout the study. The remaining sites were positive for at least one of the following at some season of the year: Escherichia coli, Shigella sp., Citrobacter sp., Klebsiella-Enterobacter group, Clostridium perfringens, or Streptococcus faecalis.

Enterobacteriaceae↗

PubMed1993

Gram-negative enteric bacillary meningitis: a twenty-one-year experience.

We reviewed our experience with gram-negative enteric bacillary meningitis in neonates and infants from 1969 through 1989. Ninety-eight patients were identified. Their ages were from 1 day to 2 years with a median of 10 days. In 25 patients (26%), predisposing factors were identified, the most common of which were neural tube defects and urinary tract anomalies. The causative agents were Escherichia coli (53%), Klebsiella-Enterobacter species (16%), Citrobacter diversus (9%), Salmonella species (9%), Proteus mirabilis (4%), Serratia marcescens (3%), Bacteroides fragilis (3%), and Aeromonas species (2%). At the time of diagnosis, Gram-stained smears of cerebrospinal fluid revealed gram-negative bacilli in 61% of patients. The causative organism was cultured from blood obtained from 55% of patients, and 21% had positive urine culture results. The cerebrospinal fluid leukocyte counts ranged from 0 to 80,600 cells/mm3, and the cerebrospinal fluid/serum glucose concentration ratio was less than 0.5 in 72% of patients. Antimicrobial regimens varied greatly. After initiation of antibiotic therapy, an average of 3 days was needed for eradication of bacteria from cerebrospinal fluid. The case-fatality rate was 17%, and 61% of survivors had long-term sequelae that included seizure disorders, hydrocephalus, physical disability, developmental delay, and hearing loss.

Anti-Bacterial Agents↗

PubMed2006

[Clinical results of resection arthroplasty for infected shoulder arthroplasty].

PURPOSE OF THE STUDY: Infection is a rare complication of shoulder arthroplasty. Various therapeutic solutions have been proposed: antibiotics alone, one-stage or two-stage reimplantation, surgical or arthroscopic cleaning without prosthesis removal, scapulohumeral arthrodesis or simple arthroscopic resection. We evaluated the mid-term clinical outcome after resection arthroplasty for the treatment of infected shoulder arthroplasty. MATERIAL AND METHODS: The series included ten infected arthroplasties in ten patients. Mean duration of implantation was two years seven months (range nine months to five years). Bacteriological diagnosis was established from intraoperative articular samples or systematic samples taken during surgical revision procedures: meti-S Staphylococcus aureus strains (n=4), coagulase-negative Staphylococcus (n=5 including three S. epidermidis) Streptococcus mitis (n=1) and Citrobacter koseri (n=1). The mean Constant score before revision was 58 (range 23-77). Subjective patient satisfaction before surgical revision was rated good in six cases, fair in one and poor in three. Surgery associated removal of the implant, complete resection of the cement, resection of the fistular tracts, wide debridement of infected tissues and total synovectomy. RESULTS: Patients were seen at an average follow-up of three years eight months. The objective functional outcome measured with the Constant score was only fair, 28 points (range 20.6-36), and corresponded to a loss of 29 points compared with the preoperative score. This was explained mainly by lower scores for joint motion, function and muscle force but with persistently satisfactory scores for pain. All patients remained pain-free (daytime and nighttime). Patient satisfaction was rated good for two, fair for five and mediocre for three. Clinical and biological proof of eradicated infection was obtained in all patients. DISCUSSION: Infection remains a serious devastating problem for shoulder arthroplasty with an important functional impact. Resection only has a modest clinical effect. Precise identification of the causal germ with institution of adapted antibiotic therapy is required for eradication of the infection. Early diagnosis is probably the most important parameter affecting clinical outcome and surgical options. Functional results after resection arthroplasty are modest. This procedure should be reserved for patients with reduced functional demands. Improved management of the infectious load and reduction of diagnostic delay should help improve functional outcome and favor use of stow-stage procedures for reinsertion.

Aged↗

PubMed2001

The ecology of "fecal indicator" bacteria commonly found in pulp and paper mill water systems.

Coliform bacteria have long been used to indicate fecal contamination of water and thus a health hazard. In this study, the in-mill water and external effluent treatment systems of seven typical Canadian pulp and paper mills were all shown to support the growth of numerous coliforms, especially Klebsiella Spp., Escherichia coli. Enterobacter spp., and Citrobacter spp. In all mills and most sampled locations, klebsiellas were the predominant coliforms. Although all but one of the mills had no sewage input and most disinfected their feed (input) water, all contained the most typical fecal indicator bacterium, E. coli. Many of the mill coliforms were classified as fecal coliforms by standard "MPN" and metabolic tests, but this was shown to be due to their thermotolerance, not their origin. Mill coliforms were shown not to be just simple transients from feedwater or furnish (wood), but to be continuously growing, especially in some of the primary clarifiers. Isolated mill coliforms grew very well on a sterilized raw combined mill effluent. The fecal streptococci (enterococci), alternative indicators of fecal health hazards, were common in all mills in the absence of sewage. Ten strains of E. coli isolated from four mills were all shown to be non-toxigenic strains of harmless serotypes. No salmonellas were found. Therefore, the use of total coliform, fecal coliform, enterococci, or E. coli counts as indicators of fecal contamination, and thus of health hazard in pulp and paper mill effluents or biosolids (sludges) known to be free of fecal input is invalid.

Bioreactors↗

PubMed1999

Gram-negative bacillary meningitis in adult post-neurosurgical patients.

BACKGROUND: To assess the clinical features and therapeutic outcomes of gram-negative bacillary meningitis (GNBM) in adult postneurosurgical patients. METHODS: Thirty adult patients with GNBM were included in this study. Their clinical features, laboratory data, prognostic factors, and therapeutic outcome were analyzed. The patients were 22 males and 8 females, aged 17-72 years. Seven had community-acquired infections and 23 had nosocomial infections. Two patients were associated with brain abscess. RESULTS: The pathogens found in the 30 GNBM patients were Pseudomonas aeruginosa, Klebsiella species, Escherichia coli, Acinetobacter baumannii, and some rare pathogens including Citrobacter freundii, Serratia marcescens, Enterobacter cloacae, and Proteus mirabilis. Among these 30 patients, 8 patients with third-generation cephalosporin-resistant GNBM were identified since 1994; all infections were nosocomially acquired. Appropriate antibiotics were given to 22 patients. Eight patients did not receive appropriate antibiotic therapy. All eight died. The mortality rate in those treated with appropriate antibiotics was 14%. CONCLUSIONS: There has been an increase of GNBM in postneurosurgical patients in recent years. In addition, the emergence of strains resistant to third-generation cephalosporins in this specific group of patients has also been noted in recent years, and has become a great therapeutic challenge. We noted many prognostic factors in postneurosurgical patients in this study; however, appropriate antibiotic therapy and initial consciousness level are the most significant ones. Therefore, in cases of postneurosurgical patients with nosocomially acquired GNBM, the possibility of third-generation cephalosporin resistance should be strongly suspected. Early initiation of appropriate antibiotic therapy is needed in this potentially fatal disease.

Adolescent↗

PubMed1981

Vi serology in the detection of typhoid carriers.

A new haemagglutination assay for Vi antibodies was evaluated in searches for symptom-free carriers of Salmonella typhi associated with sporadic cases of typhoid fever. The assay differs from previous ones in that a purified (instead of crude) Vi antigen from Citrobacter was used to sensitise the red blood cells. In ten sporadic outbreaks of typhoid stool culture identified seven enteric carriers of S. typhi among the patients' families or other close contacts. All seven carriers had Vi antibodies in titres ranging from 1:40 to 1:2560. Moreover, among thirty-seven stool-culture-negative contacts of patients, only one had Vi antibodies, in a titre of 1:10. Thus, the new assay for Vi antibodies was as sensitive and as specific as faecal culture in detecting symptom-free typhoid carriers. It could become a convenient screening test.

Adolescent↗

PubMed2000

Purification and characterization of the 1-3-propanediol dehydrogenase of Clostridium butyricum E5.

1-3 PPD dehydrogenase (EC 1.1.1.202) was purified to homogeneity from Clostridium butyricum E5 grown anaerobically on glycerol in continuous culture. The native enzyme was estimated by gel filtration to have a molecular weight of 384 200 +/- 31 100 Da; it is predicted to exist as an octamer or a decamer of identical molecular weight subunits. When tested as a dehydrogenase, the enzyme was most active with 1-3 propane diol. In the physiological direction, 3-hydroxypropionaldehyde was the preferred substrate. The apparent K(m) values of the enzyme for 3-hydroxypropionaldehyde and NADH were 0.17 mM and 0.06 mM, respectively. The enzyme requires only Mn(2+) for full activity. The enzyme was found to have properties similar to those reported for Klebsellia pneumoniae, Citrobacter freundii, and Clostridium pasteurianum.

Journal Article↗

PubMed1997

Bacterial strains isolated from eggs and their resistance to currently used antibiotics: is there a health hazard for consumers?

In order to study the putative transfer of antibiotic resistance from poultry to humans, hens' eggs were examined for the presence of various pathogens. Staphylococcus, Enterobacter, Escherichia, Proteus and Pseudomonas spp. were the most frequently isolated genera. Sensitivity tests, performed with the Kirby-Bauer technique, showed the presence of resistant strains of Staphylococcus aureus (to penicillin-G, tetracycline, erythromycin, clindamycin, cefalosporins, oxacillin, gentamycin, chloramphenicol and tobramycin), Enterococcus faecalis (to ampicillin, ciprofloxacin, clindamycin, gentamycin and tetracyclin), Escherichia coli (to tetracycline, erythromycin, ampicillin and cefalosporins), Enterobacter cloacae (to ampicillin, amoxycillin plus clavunalic acid, erythromycin and tetracycline), Pseudomonas stutzeri (to erythromycin and chlorampenicol) and Citrobacter freundii (to ampicillin, amoxycillin plus clavunalic acid, cefalosporins and co-trimoxazole).

Animals↗

PubMed1997

Characterization and amino acid sequence analysis of a new oxyimino cephalosporin-hydrolyzing class A beta-lactamase from Serratia fonticola CUV.

Serratia fonticola CUV produces two isoenzymes (forms I and II) with beta-lactamase activity which were purified by a five-step procedure. The isoenzymes had identical kinetic parameters and isoelectric point (pI = 8.12). They were characterized by a specific activity towards benzylpenicillin of 1650 U/mg. The beta-lactamase hydrolyzed benzylpenicillin, amoxycillin, ureidopenicillins, first- and second-generation cephalosporins. Carboxypenicillins and isoxazolylpenicillins were hydrolyzed to a lesser extent. Towards cefotaxime and ceftriaxone (third-generation cephalosporins), the S. fonticola enzyme exhibited catalytic efficiencies much higher than those of MEN-1 and extended-spectrum TEM derivative beta-lactamases. The beta-lactamase from S. fonticola was markedly inhibited by beta-lactamase inhibitors such as clavulanic acid, sulbactam and tazobactam. The purified isoenzymes were digested by trypsin, endoproteinase Asp-N and chymotrypsin. Amino acid sequence determinations of the resulting peptides allowed the alignment of 267 amino acid residues (Swiss-Prot, accession number P 80545) for form I beta-lactamase. Form II is five residues shorter than form I at its N-terminus. From amino acid sequence comparisons, S. fonticola CUV beta-lactamase was found to share more than 69.3% identity with the chromosomally encoded beta-lactamases of Klebsiella oxytoca, Proteus vulgaris, Citrobacter diversus and the plasmid-mediated enzymes MEN-1 and Toho-1. Therefore, the oxyimino cephalosporin-hydrolyzing beta-lactamase of S. fonticola belongs to Ambler's class A. Contribution of the serine at ABL 237 in the broad-spectrum activity of these beta-lactamases is discussed.

Amino Acid Sequence↗

PubMed2003

Development of a rapid 1-h fluorescence-based cytotoxicity assay for Listeria species.

Listeria monocytogenes is cytotoxic to the lymphocyte-origin hybridoma Ped-2E9 cell line. The relative cytotoxicity can be calculated by assaying the release of alkaline phosphatase (ALP) from the infected cell line. In this study, a fluorogenic substrate (4-methylumbelliferyl phosphate, MUP) was used to quantify the ALP activity. The assay is 3.5-fold more sensitive than the colorimetric-based assay and requires only 1 h to differentiate virulent from avirulent strains. In addition to various Listeria species, 27 different common foodborne or clinical microorganisms were tested with the fluorescence-based cytotoxicity assay and only six cultures (Bacillus cereus, Citrobacter freundii, Serratia marcescens, Pseudomonas putida, Corynebacterium glutamicum and Micrococcus luteus) showed cytotoxic effects similar to L. monocytogenes. To use this assay as a confirmatory test for virulent L. monocytogenes suspect strains, pure cultures must be isolated from the sample prior to testing.

Alkaline Phosphatase↗

PubMed2000

Modification of the bile salts-Irgasan-brilliant green agar for enumeration of Aeromonas species from food.

The present study evaluated the productivity of BIBG medium for the isolation of Aeromonas spp. from food and describes a modification of the BIBG medium (mBIBG) (increased pH (8.7), replacement of xylose by soluble starch as a carbon source, decreased concentration of bile salts) to increase its selectivity and electivity. Using the mBIBG medium, growth of the majority of the Enterobacteriaceae (9/10) was suppressed except for Citrobacter freundii. The mBIBG medium supported growth of Pseudomonas species but a clear distinction between Aeromonas and Pseudomonas colonies could be made. Interpretation of the mBIBG medium should be performed after 24 h of incubation. It was noted that three of the 27 Aeromonas strains tested did not develop on the mBIBG medium. The ability or inability to grow on a selective medium is strain-dependent. Enumeration of Aeromonas species (A. hydrophila LMG 3771, A. caviae LMG 3775, A. veronii biovar veronii LMG 9075, A. veronii biovar sobria LMG 13071) from artificially contaminated foods (shrimp, minced meat (beef/pork), precut leek, and shredded carrots) confirmed that the mBIBG medium is suitable for quantitative recovery of aeromonads (ca. 10(2)-10(7) cfu/g) in the presence of a high background flora (10(5)-10(6) cfu/g). Screening of naturally contaminated foods (vegetables, seafood, meat) for the presence of Aeromonas resulted in three out of 14 food samples showing presumptive Aeromonas colonies on mBIBG.

Aeromonas↗

PubMed2000

Assessment of the microbiological quality and wash treatments of lettuce served in University restaurants.

One hundred and forty-four samples of lettuce from 16 University restaurants were analyzed. The mesophilic aerobic counts of all samples ranged from 3.01 to 7.81 log10 CFU g(-1). Results of total coliforms ranged from < 0.47 to > 3.38 log10 most probable number (MPN) g(-1). Of the lettuce samples, 25.7% harbored Escherichia coli, 22.9% Staphylococcus aureus and 84% group D streptococci. Similarly, 10.4% of the samples harbored Aeromonas hydrophila, 2.8% Pseudomonas aeruginosa, and coliforms such as 14.6% Citrobacter freundii, 8.3% Klebsiella pneumoniae, 4.2% Enterobacter cloacae and 1.4% Providencia spp. Salmonella, Shigella and E. coli O157:H7 were not detected. When sodium hypochlorite or potassium permanganate solutions were used in washing procedures, the aerobic microorganisms were reduced by more than two log units, and total coliforms by at least one log.

Food Handling↗

PubMed2001

Evaluation of culture media for enrichment and isolation of Shigella sonnei and S. flexneri.

The performance of Gram-negative (GN) broth with (10 microg/ml) and without novobiocin, Shigella broth (SB) with 0.5 and 3.0 microg/ml novobiocin, all incubated at 37 degrees C (SB with 3.0 microg/ml novobiocin also at 42 degrees C) and buffered brilliant green bile glucose (EE) broth with 1.0 microg/ml novobiocin incubated at 37 and 42 degrees C were evaluated for resuscitation and growth of Shigella sonnei and S. flexneri (eight strains; unstressed, chill-stressed and acid-stressed) and non-shigellae (11 strains). GN broth with or without novobiocin supported significantly less growth of Shigella sp. No significant differences in growth of shigellae were obtained between the other culture media. Performance depended more on the Shigella strain used. None of the tested media were significantly superior for suppressing the competitive flora. Electivity and selectivity of MacConkey agar (MAC), tergitol-7 agar (T7), desoxycholate citrate agar (DCA), xylose lysine desoxycholate agar (XLD), Salmonella Shigella agar and Hektoen enteric agar (HEA) were determined by ecometric testing. HEA confirmed to be a high selective medium for both non-shigellae and stressed Shigella sp. Klebsiella sp., Enterobacter sp., Citrobacter sp.. Salmonella sp. and the Escherichia strains can mask the presence of shigellae. In vitro competition experiments and experiments with artificially contaminated foods showed higher resistance of S. sonnei than S. flexneri towards the stress imposed by the food matrix and its indigenous flora. Reliable detection, however, of shigellae in foods with the current enrichment and isolation media was not achieved.

Agar↗

PubMed1998

Enterobacteriaceae found in high numbers in fish, minced meat and pasteurised milk or cream and the presence of toxin encoding genes.

Enterobacteriaceae were found in high numbers after storage at 7 degrees C in 6% of consumers packs of pasteurised milk or cream, in 31% of retailed fish and in 100% of retail packs of minced meat. Seventy two fresh-water fishes, 40 packs of minced meat and 430 milk packs were sampled. One hundred and eighty four isolates were randomly picked from Tryptone glucose extract (TGE) agar (30 degrees C for 3d) or Violet red bile glucose (VRBG) agar (37 degrees C for 1d). In minced meat, Serratia liquefaciens, Hafnia alvei, Rahnella aquatilis were frequently encountered. On fish, the most frequently found species were R. aquatilis, and in milk, the dominating species were S. liquefaciens, H. alvei and R. aquatilis. One to three isolates of Citrobacter freundii were found in all three food categories. Using a polymerase chain reaction (PCR) technique, the gene of Escherichia coli heat-labile toxin (lt) was indicated in one fish isolate of R. aquatilis whereas heat-stable toxin genes (s.t.) were indicated in four H. alvei isolates, two originating from fish and two from minced meat. Positive PCR-reaction for vero cytotoxin genes were found in one H. alvei strain originating from fish (vt1), in two S. liquefaciens strains from minced meat (vt2), and in a C. freundii reference strain. One of the st-positive H. alvei strains from meat harboured the eaeA gene involved in the attaching phenotype of enteropathogenic E. coli.

Animals↗

PubMed2000

A new rapid automated method for the detection of Listeria from environmental swabs and sponges.

Many food and meat processors test environmental swabs and sponges to confirm the absence of Listeria spp. Spectral pattern changes in a liquid growth medium, resulting from esculin hydrolysis by Listeria in contaminated swabs and sponges, were automatically monitored by the BioSys instrument in a semifluid layer (SFL). The blackening of SFL in modified MOX broth resulted in sharply declining curves, which were easily detected by the instrument. The instrument detected all nine strains of Listeria monocytogenes tested. None of the gram negative organisms (Proteus, Escherichia coli, Pseudomonas, Citrobacter and Yersinia) were detected by the system, nor were most gram positive organisms, including Bacillus, Streptococcus, and Lactobacillus strains, Staphylococcus aureus, Enterococcus faecium and E. faecalis, which hydrolyze esculin, produced black colonies on PALCAM and Oxford media and were also detected in the system. A total of 122 sponges and swabs collected at food processing plants were evaluated by this method. Of these, 99 were negative, and 11 were positive. L. innocua was the dominant Listeria species in these environmental samples. Good correlation was obtained between numbers of Listeria and detection times of esculin hydrolysis: 1000 CFU/swab were detected in 10-13 h, whereas 1-10 CFU/swab were detected in less than 22 h. The total assay time was 26 h.

Animals↗