Characterization of nonfermentative nonfastidious gram negative bacteria encountered in medical bacteriology

Recurrent Stenotrophomonas maltophilia bacteremia after iliac crest bone graft harvest

We describe a rare case of recurrent Stenotrophomonas maltophilia bacteremia in a previously healthy 45-year-old man. The infection was caused by osteomyelitis at the site of an iliac crest bone graft harvest. A genetic analysis using enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) revealed that the blood isolates and pathogens obtained from the surgical wound were identical. Initial treatment with levofloxacin and cefozopran was ineffective, but the patient's infection was successfully treated by long-term administration of latamoxef and trimethoprim-sulfamethoxazole. The present case suggests that attention should be given to the possibility of S. maltophilia infection in any situations.

Cloning of a Gene Cluster from Cellvibrio mixtus which Codes for Cellulase, Chitinase, Amylase, and Pectinase

The soil isolate Cellvibrio mixtus UQM2294 degraded a variety of polysaccharides including microcrystalline cellulose. Among 6,000 cosmid clones carrying C. mixtus DNA, constructed in Escherichia coli with pHC79, 50 expressed the ability to degrade one or more of the following substrates: carboxymethyl cellulose, chitin, pectin (polygalacturonic acid), cellobiose, and starch. These degradative genes are encoded in a single 94.1-kilobase segment of the C. mixtus genome; a preliminary order of the genes is starch hydrolysis, esculin hydrolysis, cellobiose utilization, chitin hydrolysis, carboxymethyl cellulose hydrolysis, and polygalacturonic acid hydrolysis. A restriction endonuclease cleavage map was constructed, and the genes for starch, carboxymethyl cellulose, cellobiose, chitin, and pectin hydrolysis were subcloned.

A survey of the microbiological quality of bottled water sold in the UK and changes occurring during storage

Eight brands of domestic and imported bottled water were microbiologically analysed within three hours of purchase at a local supermarket. Viable numbers of microorganisms were estimated on Plate Count Agar (PCA) and PCA diluted to quarter and tenth strengths (1/4 PCA and 1/10 PCA) and incubated at temperatures of 10, 15, 25 and 37 degrees C. Plate count agar diluted to 1/4 and 1/10 incubated at 25 degrees C yielded the highest initial counts, up to 10(4) cfu ml(-1). Pseudomonas spp. was the predominant species. After 6 months of storage at room temperature (18-25 degrees C), few quantitative and qualitative differences were found in the microflora.

Microbiological and clinical aspects of infection associated with Stenotrophomonas maltophilia

The gram-negative bacterium Stenotrophomonas maltophilia is increasingly recognized as an important cause of nosocomial infection. Infection occurs principally, but not exclusively, in debilitated and immunosuppressed individuals. Management of S. maltophilia-associated infection is problematic because many strains of the bacterium manifest resistance to multiple antibiotics. These difficulties are compounded by methodological problems in in vitro susceptibility testing for which there are, as yet, no formal guidelines. Despite its acknowledged importance as a nosocomial pathogen, little is known of the epidemiology of S. maltophilia, and although it is considered an environmental bacterium, its sources and reservoirs are often not readily apparent. Molecular typing systems may contribute to our knowledge of the epidemiology of S. maltophilia infection, thus allowing the development of strategies to interrupt the transmission of the bacterium in the hospital setting. Even less is known of pathogenic mechanisms and putative virulence factors involved in the natural history of S. maltophilia infection and this, coupled with difficulties in distinguishing colonization from true infection, has fostered the view that the bacterium is essentially nonpathogenic. This article aims to review the current taxonomic status of S. maltophilia, and it discusses the laboratory identification of the bacterium. The epidemiology of the organism is considered with particular reference to nosocomial outbreaks, several of which have been investigated by molecular typing techniques. Risk factors for acquisition of the bacterium are also reviewed, and the ever-expanding spectrum of clinical syndromes associated with S. maltophilia is surveyed. Antimicrobial resistance mechanisms, pitfalls in in vitro susceptibility testing, and therapy of S. maltophilia infections are also discussed.

Molecular cloning, expression, and characterization of endoglucanase genes from Fibrobacter succinogenes AR1

A cosmid gene library was constructed in Escherichia coli from genomic DNA isolated from the ruminal anaerobe Fibrobacter succinogenes AR1. Clones were screened on carboxymethyl cellulose, and 8 colonies that produced large clearing zones and 25 colonies that produced small clearing zones were identified. Southern blot hybridization revealed the existence of at least three separate genes encoding cellulase activity. pRC093, which is representative of cosmid clones that produce large clearing zones, was subcloned in pGem-1, and the resulting hybrid pRCEH directed synthesis of endoglucanase activity localized on a 2.1-kb EcoRI-HindIII insert. Activity was expressed from this fragment when it was cloned in both orientations in pGem-1 and pGem-2, indicating that F. succinogenes promoters functioned successfully in E. coli. A high level of endoglucanase activity was detected on acid-swollen cellulose, ball-milled cellulose, and carboxymethyl cellulose; and a moderate level was detected on filter paper, Avicel, lichenan, and xylan. Most activity (80%) was localized in the periplasm of E. coli, with low but significant levels (16%) being detected in the extracellular medium. The periplasmic endoglucanase had an estimated molecular weight of 46,500, had an optimum temperature of 39 degrees C, and exhibited activity over a broad pH range, with a maximum at pH 5.0.

Heterotrophic plate counts and the isolation of bacteria from mineral waters on selective and enrichment media

The heterotrophic plate counts of 15 brands of bottled non-carbonated mineral waters were examined and found to be generally high and variable. Four selective or enrichment media for the enumeration of coliforms (m-Endo LES and m-lauryl sulphate agar) and Pseudomonas aeruginosa (cetrimide-nalidixic acid agar and malachite green broth) were used to isolate several species of Gram-negative bacteria. Strains identified as CDC gr IVc-2 and Comamonas (Ps.) acidovorans were the two most commonly isolated. Considerable variation in populations was seen between the brands, as well as between two batches of the same mineral water.

Genes from Cellvibrio mixtus encoding beta-1,3 endoglucanase

Two genes encoding beta-1,3 glucanase activity were cloned from the gram-negative soil bacterium Cellvibrio mixtus. The two clones, designated cwd (cell wall degradation) and lam (laminarin degradation), had distinct endonuclease restriction patterns and encoded enzymes with distinct substrate specificities. The 3.7-kilobase cwd insert encoded an enzyme which degraded yeast cell walls as well as the soluble beta-1,3 glucan laminarin and the insoluble beta-1,3 glucans zymosan and pachyman. The 1.8-kilobase lam insert encoded an enzyme which degraded laminarin only. Both enzymes degraded laminarin in an endohydrolytic manner to yield laminarobiose, laminarotriose, and laminarotetraose as major end products. Radiolabeled translation products of the cwd and lam transcripts were identified.

A study of the value of electrophoretic and other techniques for typing Acinetobacter calcoaceticus

Forty-four isolates of Acinetobacter calcoaceticus var anitratus collected during hospital outbreaks were studied using polyacrylamide gel electrophoresis (PAGE), plasmid analysis, antibiograms and biochemical tests to determine their degree of similarity. Reproducibility tests were also carried out on the PAGE and biochemical techniques to determine their validity when used to compare bacteria of the same type isolated intermittently. PAGE data was analysed densitometrically and isolates compared using a similarity matrix. All methods were able to subdivide the isolates, but results did not always correlate well between methods. Reproducibility data indicated that careful attention to technique is required when organisms are examined by PAGE sequentially. Results suggest that no single biotyping technique is likely to be adequate and that electrophoretic, biochemical and antibiogram data may complement one another and other epidemiological data in the typing of these organisms.

Identification of dimethyl disulfide-forming bacteria isolated from activated sludge

Twenty-four strains with high dimethyl disulfide (DMDS)-forming ability were isolated from activated sludge and identified to the genus level. These bacteria were classified into four groups (A, B, C, and D) by the API ZYM System (API System S.A., Montalieu, France). Group A (three strains) was identified as genus Lactobacillus by the API 20B System, by the method of Cowan and Steel, and by production of lactic acid as confirmed by gas-liquid chromatography. Group B (eight strains) was identified as genus Corynebacterium by API 20B and the Cowan and Steel method. Group C (one strain) was suggested to belong to genus Corynebacterium by the API 20B System. Group D (12 strains) was identified as genus Pseudomonas or Alcaligenes by the API 20B System, as genus Alcaligenes by the Cowan and Steel method, and as Achromobacter group Vd by the API 20NE System. However, on the basis of guanine-plus-cytosine contents in DNA and form of flagella, these strains were identified as genus Pseudomonas. Formation of DMDS from DL-methionine and S-methyl-L-cysteine was tested. DMDS-forming bacteria isolated from activated sludge formed DMDS from both precursors. In genus Pseudomonas, P. aeruginosa could not form DMDS from either precursor, but P. acidovorans, P. alcaligenes, P. pseudoalcaligenes, and P. testosteroni formed DMDS. In genus Alcaligenes, A. denitrificans subsp. xylosoxydans, A. denitrificans subsp. denitrificans, A. faecalis, and A. odorans formed DMDS from both precursors. Achromobacter group Vd formed DMDS from S-methyl-L-cysteine, but could not from DL-methionine.

Construction of a transposon containing a gene for polygalacturonate trans-eliminase from Klebsiella oxytoca

A DNA fragment containing a Klebsiella oxytoca gene for polygalacturonate trans-eliminase was cloned into the kanamycin resistance transposon Tn5. This new transposon, designated Tn5-Pga+, had a transposition frequency of 1 X 10(-6). The broad host range plasmid pR751::Tn5-Pga+ was conjugally transferred to a variety of genetic backgrounds. The ability to degrade polygalacturonate was expressed in Aeromonas hydrophila, Alcaligenes eutrophus, Azotomonas insolita, Escherichia coli, Pseudomonas putida and Rhodopseudomonas sphaeroides, but not in Zymomonas mobilis.

Comparison of Rapid NFT system and conventional methods for identification of nonsaccharolytic gram-negative bacteria

This study examined the Rapid NFT system (Analytab Products, Plainview, N.Y.) to determine its ability to accurately identify 229 clinical isolates of mostly nonsaccharolytic gram-negative rods. Identifications were classified by the following scheme: correct (corresponding to excellent, very good, good, or acceptable identification as listed in the code book); low discrimination (correct identification among a range of listed possibilities, with additional tests necessary for accurate identification); incorrect. Correct identification was considered correct to species and subspecies for all organisms except Alcaligenes faecalis and "Alcaligenes odorans"; "A. faecalis/odorans" was considered a correct response. By using these criteria, 71.6% of the strains were correctly identified, 17.9% were identified with low discrimination, and 10.5% were incorrectly identified. When consideration was made for incorrect identification resulting from taxonomic problems (e.g., Alcaligenes and Moraxella spp.), incorrect identifications fell to 5.2%. The Rapid NFT system was truly rapid and was easy to use and interpret. Its use of carbon substrate assimilation enables it to provide more accurate identification of medically important nonsaccharolytic bacteria than do other commercially available systems.

Physiological characterization of heterotrophic bacterial communities from selected aquatic environments

Three different biotopes, groundwater, surface water, and activated sludge, were examined and the total colony count on nutrient agar determined. The bacteria that could be isolated from the agar plates were identified and their in vitro activities investigated. Three principal approaches were used: (1) isolates were identified and the results used in a numerical analysis to determine their similarity; (2) the different physiological properties of isolates originating from a single biotope were compiled and used to characterize the community (collective total activity); and (3) the diversity of the physiological properties of the isolates of all populations was determined; on the basis of main characters a "heterotrophic" diversity index was calculated. The possibility of using a polyphasic ecological study to characterize aquatic bacterial communities is considered.

Transposon mutagenesis and cloning analysis of the pathways for degradation of 2,4-dichlorophenoxyacetic acid and 3-chlorobenzoate in Alcaligenes eutrophus JMP134(pJP4)

Plasmid pJP4 permits its host bacterium, strain JMP134, to degrade and utilize as sole sources of carbon and energy 3-chlorobenzoate and 2,4-dichlorophenoxyacetic acid (R. H. Don and J. M. Pemberton, J. Bacteriol. 145:681-686, 1981). Mutagenesis of pJP4 by transposons Tn5 and Tn1771 enabled localization of five genes for enzymes involved in these catabolic pathways. Four of the genes, tfdB, tfdC, tfdD, and tfdE, encoded 2,4-dichlorophenol hydroxylase, dichlorocatechol 1,2-dioxygenase, chloromuconate cycloisomerase, and chlorodienelactone hydrolase, respectively. No function has been assigned to the fifth gene, tfdF, although it may encode a trans-chlorodiene-lactone isomerase. Inactivation of genes tfdC, tfdD, and tfdE, which encode the transformation of dichlorocatechol to chloromaleylacetic acid, prevented host strain JMP134 from degrading both 3-chlorobenzoate and 2,4-dichlorophenoxyacetic acid, which indicates that the pathways for these two substrates utilize common enzymes for the dissimilation of chlorocatechols. Studies with cloned catabolic genes from pJP4 indicated that whereas all essential steps in the degradation of 2,4-dichlorophenoxyacetic acid are plasmid encoded, the conversion of 3-chlorobenzoate to chlorocatechol is specified by chromosomal genes.

Differentiation of gram negative rods other than Enterobacteriaceae and Vibrionaceae by a micromethod for determination of carbon substrate assimilation

The assimilation techniques described for taxonomic study are unsuitable for routine diagnosis because of the need for purification and standardization of substrates, the great quantity of medium consumed and difficulties in interpreting the results. A standardized micromethod (API Strip) for the study of carbon substrate assimilation by bacteria has recently been described (Zbl. Bakt. Hyg., I. Abt. Orig. A 255 (1983) 479-488). The prototype gallery used consisted of two strips of 32 microtubes each containing dehydrated carbon substrate. Each strip contained 30 tests plus positive and negative controls. The suspension medium was a synthetic semi-gel. A total of 1046 strains of Gram-negative rods representing 41 species belonging to the genera Pseudomonas, Alcaligenes, Moraxella, Acinetobacter, Flavobacterium and to the EF4 group were tested (Tables 1 to 6). Automatic reading was performed after incubation at 32 degrees C for one day, or two days for slow growing bacteria, using an ATB 1500 reader (API System) linked to a HP 85 microcomputer (Hewlett-Packard). Most species showed typical carbon substrate assimilation patterns allowing their differentiation from other species within each genus. The results obtained with the micromethod agreed in large measure with the nutritional patterns reported by other workers. It should be possible to use these results to construct a set of tests suitable for identifying species of Gram-negative rods other than Enterobacteriaceae and Vibrionaceae.

Evaluation of commercial test systems for the identification of nonfermenters

Three commercially available test systems for the identification of nonfermentative gram-negative rods were compared: API 20NE, flow N/F and Minitek Nonfermenter System. Two hundred strains were identified by conventional means and by each test system. The rate of correct identification of Acinetobacter, Alcaligenes, Flavobacterium and Moraxella strains to genus level and of the other genera to species level was 92% with API 20NE, 84% with flow N/F and 75% with Minitek Nonfermenter System. The need for these kits in the diagnostic hospital laboratory is also discussed.

Characterization of some groups of gram-negative nonfermentative bacteria by the carbon source alkalinization technique

A total of 541 gram-negative nonfermentative bacterial strains comprising 26 species and unclassified groups were characterized by routine diagnostic and carbon substrate alkalinization techniques. These microorganisms were tested for the ability to cause alkalinization of a basal medium on a total of 217 substrates. We found that 58 carbon substrates had some discriminatory potential. We also performed 30 routine diagnostic tests. The results of these studies were evaluated by numerical taxonomy techniques. A cluster analysis of the results by the Jaccard coefficient method identified 30 clusters at the 45% level. We identified 39 tests that separated most of the groups. Groups of similar organisms or organisms that were difficult to identify were analyzed, and tests that were differential were identified. Because of variability within the clusters, further studies utilizing deoxyribonucleic acid-deoxyribonucleic acid homologies should be undertaken.

Characterization of a radiation-resistant Acinetobacter

For characterizing the radiation-resistant Acinetobacter strain FO-1 reported in the previous paper (1980), we investigated the structure of cell wall, the cellular fatty acid composition, and the detailed taxonomic characteristics. The results denoted that the cell division occurred by simple constriction with the formation of a slight septum and the intermediate dense layer between the outer membrane and the plasma membrane was seen, the main components of the cellular fatty acids were oleic acid, palmitic acid, and palmitoleic acid, and that the strain was tolerant to salt and could not produce acids from cellobiose, melibiose, lactose, and ribose.

Distribution in clinical material and identification of Pseudomonas maltophilia

During the 10-year period ending March 1976, 128 (8.5%) of 1506 strains of Gram-negative non-fermentative bacteria submitted to the National Collection of Type Cultures for computer-assisted identification have been strains of Pseudomonas maltophilia. These figures suggest that Ps. maltophilia is both a relatively common species in clinical material in the United Kingdom and also that many laboratories experience difficulty in identifying this species. We report the sources from which our strains were isolated and also characteristics of the species by which it may be recognised. The clinical significance of Ps maltophilia is discussed and also the susceptibility of this species to certain antimicrobial agents.

Isolation and characterization of the pesticide-degrading plasmid pJP1 from Alcaligenes paradoxus

A strain of Alcaligenes paradoxus, unable to degrade phenoxyacetic acid, was shown to degrade two synthetic derivatives of this molecule, the herbicides 2,4-dichlorophenoxyacetic acid and 2-methyl-4-chlorophenoxyacetic acid. The ability to degrade these pesticides is encoded by a 58-megadalton conjugal plasmid, pJP1.

Infection with Pseudomonas maltophilia hospital outbreak due to contaminated disinfectant

Between August, 1973, and May, 1974, Pseudomonas maltophilia was isolated from 63 patients in the King Edward Memorial Hospital for Women, Subiaco, Western Australia. Primary cultures were obtained mainly from specimens of urine from adults, and from intraarterial catheter tips and umbilical swabs from neonates. In most cases the organism appeared to be a contaminant, but in seven it was responsible for infection. The source of the organism was deionized water used for diluting Savlon concentrate (chlorhexidine, 1-5%; cetrimide, 15%). In the 17 months since the method of preparation and distribution of Savlon to the wards was altered, Ps. maltophilia has not been isolated from either clinical specimens or hospital disinfectants.

Multiresistant plasmids from Pseudomonas aeruginosa highly resistant to either or both gentamicin and carbenicillin

High-level resistance to gentamicin and carbenicillin was found in 30 and 10.7%, respectively, of Pseudomonas aeruginosa strains, especially in isolates from urine. In 23 out of 25 strains tested, these resistances were R mediated and linked to multiresistant plasmids, carrying genes for resistances to five other aminoglycosides, tobramycin, kanamycin, neomycin, streptomycin, and spectinomycin, and for resistances to chloramphenicol, tetracycline, sulfonamides, and mercury chloride. Carbenicillin resistance was unstable in Pseudomonas, and in its presence the multiresistant plasmids had a host range extended to the Enterobacteriaceae (group I plasmids). Otherwise they were transferable intragenerically only (group II plasmids). The extended host range plasmids were, as a rule, in fi(-) incompatibility class A-C. Segregants incompatible with both class A-C and P plasmids were detected. The beta-lactamase specified by the carbenicillin marker was of the TEM-like type. Multiple linkages of resistance determinants to the aminoglycosides were concomitantly present in most of the plasmids. Results from the bioassay indicated the presence of at least two aminoglycoside-inactivating enzymes.

Rapid method for identification of gram-negative, nonfermentative bacilli

A rapid system (OA), based on oxidative attack of substrates, was developed for identification of gram-negative, nonfermentative bacillia (NFB). One hundred and twelve strains of NFB from 25 species (representing the genera Pseudomonas, Alcaligenes, Acinetobacter, Bordetella, Flavobacterium, Moraxella, and Xanthomonas) were assayed by OA, buffered single substrate, and oxidative/fermentative methods. The 38 substrates consisted of salts of organic acids, nitrogen-containing compounds, alcohols, and carbohydrates. Ninety-four percent of the test strains were identified by the OA method in 24 h, and 99% were identifiable in 48 h. Reproducibility was 99%. Correlation with buffered single substrate was 98% (all substrates) and 90% with the oxidative/fermentative method (carbohydrates only). Biochemical profiles of all strains are presented, as well as tables showing the most useful tests for identification.

Characteristics of yellow-pigmented nonfermentative bacilli (groups VE-1 and VE-2) encountered in clinical bacteriology

The morphological and physiological characteristics of 20 strains of motile, gram-negative, yellow-pigmented oxidative bacilli (groups VE-1 and VE-2) isolated in clinical bacteriology are described. Electron micrographs demonstrate the polar multitrichous flagella of group VE-1 and polar monotrichous flagella of group VE-2. Data obtained from guanine plus cytosine ratio studies of 56.8% for VE-1 and 68.9% for VE-2 distinguish the two groups of bacteria.

One-tube test for determining oxidative or fermentative metabolism of bacteria

A one-tube test for distinguishing oxidation from fermentation in the metabolism of carbohydrates was examined on 1,200 gram-negative bacilli. There was a 100% correlation between the one-tube method and the standard two-tube procedure.

Short-chain acids of Pseudomonas species encountered in clinical specimens

The short-chain acids of 36 strains of Pseudomonas grown on Trypticase soy agar were determined by gas-liquid chromatography. Distinct acid profiles were observed for each of the eight species tested. Propionic, isobutyric, and isovaleric acids were the principal acids detected in media extracts of P. maltophilia, P. cepacia, P. pseudoalcaligenes, P. diminuta, and P. vesiculare. The presence and relative amounts of the isobutyric and isovaleric acids clearly distinguished P. maltophilia, P. pseudoalcaligenes, and P. cepacia from other species. P. diminuta could be distinguished from P. vesiculare by the production of glutaric acid; P. testosteroni was the only species tested which produced relatively large amounts of phenylacetic acid.