Oxidase-negative Strains Research Articles

Arthrobacter caoxuetaonis sp. nov., Arthrobacter zhangbolii sp. nov. and Arthrobacter gengyunqii sp. nov., isolated from Marmota himalayana faeces from Qinghai-Tibet Plateau.

Six aerobic or facultative anaerobic, motile, Gram-stain-positive, catalase-positive and oxidase-negative strains (zg-Y453T, zg-Y324, zg-Y462T, zg-Y411, zg-Y809T and zg-Y786) were isolated from different faecal samples of Marmota himalayana from the Qinghai-Tibet Plateau. Pale yellow, round, raised and moist colonies appeared 48 h after incubation at 28 °C on brain-heart infusion plates supplemented with 5 % defibrinated sheep blood. According to the 16S rRNA gene sequence alignment, two strain pairs (zg-Y453T/zg-Y324 and zg-Y462T/zg-Y411) shared the highest similarities to Arthrobacter luteolus (99.5 and 99.2 %), and the other one (zg-Y809T/zg-Y786) to Arthrobacter citreus (99.5 %). Results of phylogenetic analysis based on the 16S rRNA gene and genome sequences showed that these six strains represented three separate species within the genus Arthrobacter. The average nucleotide identity and digital DNA-DNA hybridization values between the three novel type strains (zg-Y453T/zg-Y462T/zg-Y809T) and other known species in this genus were all below respective thresholds (70.2-81.5/19.6-24.2 %, 70.6-81.8/19.8-25.0 %, and 70.4-88.2/19.9-35.3 %). Although phylogenetically related, there were obvious chemotaxonomic and phenotypic differences: strain pair zg-Y462T/zg-Y411 had anteiso-C15 : 0 as the only major fatty acid; the three novel species had different dominant quinones, MK-8(H2) in strains zg-Y462T/zg-Y809T (74.8/81.1 %) and MK-8(H2)/MK-9(H2) (43.1/53.0 %) in zg-Y453T; similarly, the ability to reduce nitrate in strains zg-Y453T and zg-Y462T could differentiate them from zg-Y809T. All strains had diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol, but differed slightly in the types of unidentified glycolipids, phospholipids and lipids. Based on the results of these polyphasic taxonomic analyses, three novel species within the genus Arthrobacter are proposed, namely Arthrobacter caoxuetaonis sp. nov. (type strain, zg-Y453T=GDMCC 1.2809T=JCM 35173T), Arthrobacter zhangbolii sp. nov. (type strain, zg-Y462T=GDMCC 1.2880T=JCM 35170T) and Arthrobacter gengyunqii sp. nov. (type strain, zg-Y809T=GDMCC 1.2808T=JCM 35168T).

Acinetobacter lanii sp. nov., Acinetobacter shaoyimingii sp. nov. and Acinetobacter wanghuae sp. nov., isolated from faeces of Equus kiang.

Six aerobic, non-motile, non-haemolytic, Gram-stain-negative, oxidase-negative strains (185T, 187, 323-1T, 194, dk386T and dk771) were recovered from different faecal samples of Equus kiang on the Qinghai-Tibet Plateau. In the 16S rRNA gene sequences, one strain pair, 185T/187, shared highest similarity to Acinetobacter equi 114T (97.9 %), and the other two (323-1T/194 and dk771T/dk386) to Acinetobacter harbinensis CGMCC 1.12528T (98.6 and 97.0 %, respectively). Phylogenomic tree analysis showed that these six strains formed three separate clades in the genus Acinetobacter. Digital DNA-DNA hybridization values of each pair of the isolates with all members of the genus Acinetobacter were far below 70 %. The main cellular fatty acids of all six strains were C18 : 1 ω9c, C16 : 0 and summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c). Q-9 was the predominant respiratory quinone for strains 185T, 323-1T and dk386T. The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. Based on the genotypic, phenotypic and biochemical analyses, these six strains represent three novel species of the genus Acinetobacter, for which the names Acinetobacter lanii sp. nov., Acinetobacter shaoyimingii sp. nov. and Acinetobacter wanghuae sp. nov. are proposed. The type strains are 185T (=CGMCC 1.13636T=JCM 33607T), 323-1T (=CGMCC 1.13940T=JCM 33608T) and dk386T (=CGMCC 1.16589T=JCM 33592T), respectively.

Characterization of three strains of Capnocytophaga canis isolated from patients with sepsis.

Capnocytophaga canimorsus and Capnocytophaga cynodegmi, both commensal bacteria in the oral cavities of dogs and cats, are zoonotic pathogens. In particular, C. canimorsus causes sepsis and fatal septic shock. Recently, a novel Capnocytophaga species, C. canis, was isolated from the oral cavities of healthy dogs. It is reportedly oxidase-negative and therefore considered avirulent in humans. In the present study, three strains of C. canis were isolated from Japanese patients with sepsis. All three strains, HP20001, HP33001 and HP40001, were oxidase-positive. Nucleotide sequence identities of the 16S rRNA gene of the three strains to the C. canimorsus type strain ATCC35979, C. cynodegmi type strain ATCC49044 and C. canis type strain LMG29146 were 96.9-97.0%, 96.9-97.0% and 99.7-99.8%, respectively. Multi-locus sequence analysis based on seven house-keeping genes, dnaJ, fumC, glyA, gyrB, murG, trpB and tuf, revealed that the oxidase-positive C. canis strains isolated in Japan and oxidase-negative strains of C. canis from canine oral cavities in Switzerland were clustered in different genetic subgroups. These results indicate that the virulence of C. canis strains in humans is associated with oxidase activity.

Corynebacterium defluvii sp. nov., isolated from Sewage.

A Gram-positive, aerobic, non-motile, rod-shapeds, catalase-positive, and oxidase-negative strain, designated Y49T, was isolated from sewage collected from Jilin Agricultural University, China. It grew at 20-40°C (optimum at 30°C), at pH 6.0-8.0 (optimum at 7.0) and at 0-1.0% sodium chloride (optimum at 0%). The major isoprenoid quinone was menaquinone-8 (MK-8) and the polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmethylethanolamine, four unidentified lipids, and two unidentified aminolipids. The peptidoglycan was meso-diaminopimelic acid. The cell-wall sugars were galactose, arabinose, and glucose. The fatty acids were C9:0, C16:0, C16:1 ω9c, C17:1 ω9c, C18:3 ω6c (6,9,12), C18:1 ω9c, and C18:0. The DNA G+C content was 51.4 mol%. Based on the 16S rRNA gene sequence analysis, the nearest phylogenetic neighbors of strain Y49T were Corynebacterium efficiens DSM 44549T (97.5%), Corynebacterium callunae DSM 20147T (97.2%), Corynebacterium deserti GIMN 1.010T (96.8%), Corynebacterium glutamicum ATCC 13032T (96.4%), and other species belonging to this genus (92.3-95.4%). The DNA-DNA relatedness value between strain Y49T and C. efficiens DSM 44549T, C. callunae DSM 20147T, C. deserti GIMN1.010T, and C. glutamicum ATCC 13032T was 25.5±2.0%, 21.1±1.0%, 16.5±0.5%, and 13.5±0.9%, respectively. Based on the phylogenetic analysis, chemotaxonomic data, physiological characteristics and DNA-DNA hybridization data, strain Y49T represents a novel species of the genus Corynebacterium, for which the name Corynebacterium defluvii sp nov. is proposed. The type strain is Y49T (= KCTC 39731T =CGMCC 1.15506T).

Halodesulfovibrio spirochaetisodalis gen. nov. sp. nov. and reclassification of four Desulfovibrio spp.

An antibiotic-producing, obligate anaerobic, Gram-stain-negative, catalase- and oxidase-negative strain (JC271T) was isolated from a marine habitat and identified, based on 16S rRNA gene sequence analysis, as a novel member of the family Desulfovibrionaceae. The closest phylogenetic relatives of strain JC271T were found to be Desulfovibrio marinisediminis C/L2T (99.2 %), Desulfovibrio acrylicus W218T (98.7 %), Desulfovibrio desulfuricans subsp. aestuarii (98.6 %), Desulfovibrio oceani subsp. oceani (98.0 %), Desulfovibrio oceani subsp. galatae (98.0 %) and other members of the genus Desulfovibrio (≤91.9 %). To resolve its full taxonomic position, the genomic sequence of strain JC271T was compared to available genomes of the most closely related phylogenetic members. Average Nucleotide Identity scores and DNA-DNA hybridization values confirmed that strain JC271T represents a novel genomic species. Iso-C17 : 0, iso-C17 : 1ω9c, and iso-C15 : 0 were found to be the major (comprising >10 % of the total present) fatty acids of strain JC271T. Phosphatidylglycerol, phosphatidylethanolamine and unidentified lipids (L1-8) were the polar lipids identified. The G+C content of strain JC271T was 46.2 mol%. Integrated genomic and phenotypic data supported the classification of strain JC271T as a representative of a novel genus, for which the name Halodesulfovibrio spirochaetisodalis gen. nov., sp. nov. is proposed. The type strain is JC271T (=KCTC 15474T=DSM 100016T). It is also proposed that Desulfovibrio acrylicus W218T is the latter heterotypic synonym of Desulfovibrio desulfuricans subsp. aestuarii Sylt 3T. Desulfovibrio desulfuricans subsp. aestuarii Sylt 3T should also be elevated as Halodesulfovibrio aestuarii comb. nov. and Desulfovibrio marinisediminisreclassified as Halodesulfovibrio marinisediminis comb. nov. Desulfovibrio oceani subsp. oceanishould be reclassified as Halodesulfovibrio oceani subsp. oceani comb. nov. and Desulfovibrio oceani subsp. galateae as Halodesulfovibrio oceani subsp. galateae comb. nov.

Lysobacter rhizophilus sp. nov., isolated from rhizosphere soil of mugunghwa, the national flower of South Korea

A Gram-staining-negative, aerobic, motile, rod-shaped, catalase- and oxidase-negative strain with one polar flagellum, designated THG-YS3.6T, was isolated from rhizosphere soil of a mugunghwa flower collected from Kyung Hee University, Yongin, South Korea. Growth occurred at 10-37 °C (optimum 25-30 °C), at pH 6-8 (optimum 7.0) and with 0-2.0 % NaCl (optimum 1 %). The isoprenoid quinone was ubiquinone-8 (Q-8). The major cellular fatty acids were iso-C11 : 0, iso-C11 : 0 3-OH, iso-C15 : 0, iso-C16 : 0, C16 : 1ω7c alcohol, C16 : 0, iso-C17 : 0 and summed feature 9 (iso-C17 : 1ω9c and/or C16 : 0 10-methyl). The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylethanolamine, one unknown phospholipid, one unknown lipid and three unknown aminolipids. The DNA G+C content of strain THG-YS3.6T was 65.3 mol%. Based on 16S rRNA gene sequence analysis, the nearest phylogenetic neighbours of strain THG-YS3.6T were identified as Lysobacter yangpyeongensis KACC 11407T (98.7 %), Lysobacter oryzae KCTC 22249T (98.0 %), Lysobacter niabensis KACC 11587T (97.6 %) and Lysobacter terrae KACC 17646T (97.1 %). The DNA-DNA relatedness values between strain THG-YS3.6T and L. yangpyeongensis KACC 11407T, L. oryzae KCTC 22249T, L. niabensis KACC 11587T and L. terrae KACC 17646T were 53.8±1.0 %, 12.9±1.2 %, 10.9±0.6 % and 7.0±1.9 %, respectively. On the basis of the phylogenetic analysis, chemotaxonomic data, physiological characteristics and DNA-DNA hybridization data, strain THG-YS3.6T represents a novel species of the genus Lysobacter, for which the name Lysobacter rhizophilus sp. nov. is proposed. The type strain is THG-YS3.6T (=KCTC 52082T=CCTCC AB 2015358T).

Lampropedia cohaerens sp. nov., a biofilm-forming bacterium isolated from microbial mats of a hot water spring, and emended description of the genus Lampropedia.

A biofilm-forming, Gram-stain-negative, aerobic, catalase-positive but oxidase-negative strain, designated CT6T, was isolated from the microbial mats (∼45 °C) of a hot water spring, located within the Himalayan ranges at Manikaran, Himachal Pradesh, India. Strain CT6T formed white, smooth colonies with irregular margins. Transmission electron microscopy revealed coccoid, non-flagellated cells with wavy boundaries. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain CT6T belongs to the genus Lampropedia with a sequence similarity value of 95.4 % to the sole member of this genus, Lampropedia hyalina ATCC 11041T. Strain CT6T was found to have phosphatidylethanolamine and phosphatidylglycerol as the major polar lipids. The major cellular fatty acids were C16 : 0, summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), C14 : 0, C19 : 0ω8c cyclo and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The major respiratory quinone was ubiquinone-8. The major polyamines were putrescine, spermidine and the betaproteobacterial-specific 2-hydroxyputrescine. The DNA G+C content was 63.5 mol%. Based on the genotypic, phenotypic, physiological and biochemical data, strain CT6T is considered to represent a novel species of the genus Lampropedia, for which the name Lampropedia cohaerens sp. nov. is proposed ( = DSM 100029T = KCTC 42939T = MCC 2711T).

Antimicrobial Activity of Methanolic Extract and Ether Extract of Ageratum conyzoides

Ageratum conyzoides, a weed prevalent in India, is known for its several therapeutic uses to control infections. In the present study we compared the antimicrobial potential of its ether extract and methanolic extract with ciprofloxacin on 294 strains of Gram positive bacteria (GPBs), 575 strains of Gram negative bacteria (GNBs), 15 yeast and 5 mould strains of clinical and nonclinical origin belonging to 49 genera and more than 155 species using disc diffusion assay. The microbial strains in the study were isolated from samples of abiotic (41) and biotic (101) environment, foods (81), clinically sick (441), dead (108) and healthy (75) animals and human beings, and 42 were reference strains. The study revealed that there was no appreciable difference in antimicrobial activity of ether extract (ACEE) or methanolic extract (ACME) of A. conyzoides. A total of 214 (24.1%) strains were sensitive to ACME while of the 697 strains tested for ciprofloxacin 551 (79.1%) were sensitive. Sensitivity to ACME among 294 GPBs (44.9%) was significantly (p<0.0001) higher than among 575 strains of GNBs (12.4%). There was no significant difference among GPBs and GNBs for ciprofloxacin (one of the most commonly used antibiotics in India) sensitivity, but oxidase negative GNBs (385) as well as GPBs (238) were about two times more commonly sensitive to ciprofloxacin than 190 oxidase positive GNBs (p = 0.001) and 56 oxidase positive GPBs (p, 0.03), respectively. For ACME oxidase positive strains had 2.4 times more odds (p < 0.0001) in their favour of being sensitive to ACME (53.4%) than oxidase negative strains (18.6%). The most sensitive strains to ACME belonged to oxidase positive GPBs (62.5%) followed by oxidase negative GPBs (40.8%), oxidase positive GNBs (27.4%) and oxidase negative GNBs (4.9%). All Aeromonas, Alcaligenes, Klebsiella, and Proteus species strains were resistant to ACME irrespective of source of isolation or association with illness. In contrast, majority of the strains of Burkholderia (76.9%), Bacillus (66.7%) and Brucella (53.8%) species were sensitive to ACME. The study revealed that A. conyzoides might be containing useful antimicrobial component(s) more active against oxidase positive potentially pathogenic strains often associated with systemic and deadly infections in animals as well as in humans.

A method for the rapid detection and identification of halo blight pathogen on common bean

A diagnostic method based on nested-PCR, followed by ELISA and conventional bacteriology tests, for the rapid and reliable detection of halo blight pathogen Pseudomonas savastanoi pv. phaseolicola (Psp) collected from infected bean leaves and seeds is described. Psp formed white, small and flat colonies on nutrient agar medium, creamy white, flat and circular on Milk-Tween agar medium and light yellow, convex and shiny on modified sucrose peptone agar medium. Eighteen Gram-negative, catalase-positive and oxidase-negative strains were subjected to nested PCR with primers P 5.1/P 3.1 and P 5.2/P 3.2, which directed the amplification of the 450 bp target DNA fragment in all tested strains. According to the results of DAS- and PTA-ELISA with respect to reactivity to specific antibodies, all analyzed strains belonged to Psp bacterium. Pathogenicity was tested on bean pods and cotyledon leaves, on which greasy spots were formed. Psp did not cause hypersensitive reaction on the leaves of tobacco and geranium. Strains produced levan, fluorescent pigment, oxidative metabolism of glucose, did not reduce nitrate, did not produce indole and H2S, did not hydrolyze starch, gelatin and esculin; they produced acid from glucose, mannose, sucrose and glycerol, and did not produce acid from maltose, starch, esculin, dulcite, sorbitol, inositol and erythritol. <br><br><font color="red"><b> This article has been retracted. Link to the retraction <u><a href="http://dx.doi.org/10.2298/ABS150609074E">10.2298/ABS150609074E</a><u></b></font>

Campylobacter rectus and Campylobacter gracilis Isolated from Human Periodontal Pockets

We previously isolated 40 predominant strains of bacteria, the characteristics of which resembled Wolinella (presently Campylobacter), among 422 isolates from seven human periodontal pockets; however, at that time, exact identification was not possible by conventional microbiological and biochemical tests because the criteria were ambiguous. Therefore, in the present study we aimed to clarify the classifications of the 17 representative strains by polymerase chain reaction (PCR) using a species-specific primer, 16S rDNA sequence similarity, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and Western immunoblotting. We also aimed to describe each strain's biochemical characteristics in detail. All of the 17 isolates studied were asaccharolytic, positive in nitrate reduction and arylsulfatase activity, negative in catalase and urease, and produced succinate as an end product of formate and fumarate for growth. Of the 17, 13 strains were identified as C. rectus, and 4 were oxidase negative strains (C. gracilis). Three of the C. gracilis strains were cocobacilli, which were morphologically different from the previously established strains. Evidence suggests that Campylobacter isolates from periodontal pockets in our previous work may be primarily C. rectus and secondarily C. gracilis.

Acinetobacter spp. and other non-fermentative pathogens causing nosocomial bacteremias

Members of the genus Acinetobacter were first described by Morax in France and Axenfeld in Germany in 1896, and became initially known as the Morax-Axenfeld bacillus. Over the years some 15 different generic names have been used to describe this microorganism, the most common being: Bacterium antitrutum, Herella va@nicola, Mima polymorpha, Achrornobacter, Alcaligenes, BSl/t: Moraxella lwofii, etc. Baumann, Doudoroff and Stainer in 1968 showed clearly that the oxidase-negative strains which were later given the name Acinetobacter differed from the oxidase-positive strains which were later given the name Moraxella. Today, modern niolecular taxonomic methods have resulted in a new classification comprising at least 19 DNA-DNA homology groups ofwhich, to date, seven have been given species names.

Molecular and phenotypic methods for the characterization of atypical Aeromonas salmonicida

Atypical Aeromonas salmonicida form a taxonomically diverse group among the psychrophilic A. salmonicida. Characteristics of 53 atypical A. salmonicida strains originating from Finland, Denmark, Norway and Sweden were studied using 60 phenotypic tests. Ribopattern analysis and plasmid profiles were used as genetic methods. The production of brown pigment on the furunculosis agar containing l-tyrosine divided the atypical oxidase-positive strains into two groups: pigment-producing ( n = 35) and achromogenic ( n = 16). PstI differentiated all the atypical A. salmonicida from A. salmonicida subsp. salmonicida. Combined ribopattems ClaI/ PstI divided pigment producing atypical strains into four major groups B/B, G/G, G/T, F/F. Most of the achromogenic oxidase-positive strains belonged to two major groups H/H or U/U. Cluster analysis of ribopatterns and plasmid profile analysis also supported the division of atypical oxidase-positive A. salmonicida into pigment-producing and achromogenic groups. The oxidase-negative strains formed a distinct group which differed from oxidase-positive atypical A. salmonicida type biochemically and in terms of ribopatterns. Our results also support the use of ribopattern analysis as a valid method to study the epidemiology of infections caused by atypical A. salmonicida on fish farms.

AtypicalAeromonas salmonicidaAssociated with Ulcerated Flatfish Species in the Baltic Sea and the North Sea

Abstract Skin ulceration in flatfish is a well-known clinical condition described in several reports since the beginning of the 20th century, but its etiology has not been fully described. In the present study European flounder Platichthys flesus, dab Limanda limanda, and plaice Pleuronectes platessa were examined for bacteria. The fish were from the southern Baltic Sea off the German and Danish coasts and from the North Sea off the Danish coast. Slow-growing, pinpoint colonies were isolated from skin ulcers of 73% of the fish examined. In one case, similar colonies were also isolated from the kidney. Based on growth characteristics and morphological, biochemical, and serological properties, the isolated bacteria were classified as “atypical” Aeromonas salmonicida. The strains isolated from ulcerated European flounder in this study seemed to be identical to the oxidase-negative strains previously isolated from European flounder off the Finnish coast. The strains isolated from dabs and plaice differed from...

Induction of glucose oxidase, catalase, and lactonase in Aspergillus niger.

The induction of glucose oxidase, catalase, and lactonase activities was studied both in wild-type and in glucose oxidase regulatory and structural mutants of Aspergillus niger. The structural gene for glucose oxidase was isolated and used for Northern analysis and in transformation experiments using various gox mutations. Wild-type phenotype could be restored in the glucose oxidase-negative mutant (goxC) by transformation with the structural gene. We conclude, therefore, that the goxC marker which is located on chromosome 2 represents the structural gene of glucose oxidase. Glucose and a high oxygen level are necessary for the induction of all three enzyme activities in the wild-type strain and it was shown that both glucose and oxygen effects reflect regulation at the transcriptional level. The goxB mutation results in constitutive expression of all three activities although modulated to some extent by the carbon source. The goxE mutation only has an effect on lactonase and glucose oxidase expression and does not relieve the necessity for a high oxygen level. Catalase and lactonase could not be induced in the glucose oxidase-negative strain (goxC). Addition of H2O2 resulted in the induction of all three enzymes in the wild-type without glucose being present. The H2O2 induction is probably mediated by the goxB product. Besides the H2O2 induction there is still an effect of the carbon source on the induction. A model for induction of glucose oxidase, catalase, and lactonase in A. niger is discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

N,N,N'-N'-Tetramethyl-p-Phenylenediamine-Dependent Cytochrome Oxidase Analyses of Bacillus Species

A total of 342 strains belonging to the genus Bacillus were examined for cytochrome oxidase activity by using a quantitative colorimetric N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) oxidase assay. The following three oxidase reaction groups were identified: (i) a highly oxidase-positive group, whose members oxidized TMPD with specific activities of more than 0.400 μmol/h per mg (dry weight); (ii) an oxidase-negative group, whose members were incapable of oxidizing TMPD (like Escherichia coli); and (iii) an intermediate group of strains designated the oxidase-indeterminate group, whose members oxidized TMPD at rates just slightly higher than the autooxidation rate. Of 293 mesophilic Bacillus strains analyzed 23% were oxidase positive, 47% were oxidase indeterminate, and 30% were oxidase negative. Of 37 thermophilic strains, 68% were highly oxidase positive. All of the psychrophiles tested (13 strains) gave oxidase-indeterminate reactions. Spectral analyses of the membranes of 58 Bacillus strains revealed that there was type c cytochrome(s) in all 39 oxidase-positive and oxidase-indeterminate strains. Cytochrome o was detected in all 58 strains, 27 strains contained cytochromes o and a+a 3, and 9 strains contained cytochromes o, a+a 3, and d. The remaining 22 strains contained cytochrome o exclusively. Analyses of 19 oxidase-negative strains revealed that 17 lacked type c cytochromes; the exceptions were Bacillus megaterium ATCC 14581T (T = type strain) and Bacillus pantothenticus No. 1T. All 19 oxidase-negative strains contained cytochrome o; 11 of these strains also contained cytochromes a+a 3, 4 strains contained cytochromes o, a+a 3, and d, and another 4 strains possessed cytochrome o exclusively as the sole terminal oxidase.

Enterotoxigenic bacteria in food and water from an Ethiopian community.

Food and water samples from an Ethiopian community were screened for the presence of enterotoxin-producing bacteria. Using the Chinese hamster ovary cell assay, 40 of 213 isolates (18.8%) produced heat-labile (LT) enterotoxin. These LT-producing isolates comprised 33 of 177 (18.6%) strains from 24 of 68 food samples (35.3%) and 7 of 36 (19.4%) isolates of 4 of 17 water samples (23.5%). One LT-producing strain each of Salmonella emek and of Shigella dysenteriae was found. Three pseudomonads, all LT producers, produced heat-stable enterotoxin as gauged by the suckling mouse test. Two strains of LT-enterotoxigenic Escherichia coli O68 were found in water samples. No enterotoxigenic E. coli were isolated from food samples, but 13 of the LT-producing strains were Enterobacter, Klebsiella, Serratia, and Proteus species, and 7 food samples yielded more than one species of enterotoxigenic bacterium. Of the enterotoxigenic isolates from food, 15 were oxidase-positive strains of the genera Aeromonas, Pseudomonas, Achromobacter, Flavobacterium, and Vibrio. LT-enterotoxigenic Enterobacter, Acinetobacter, Klebsiella, Proteus, Providencia, and Serratia species represented 20 of the food and water isolates. Culture supernatant fluids of representative strains of oxidase-positive and oxidase-negative species giving positive reactions in Chinese hamster ovary cell tests induced fluid accumulation in rabbit ileal loops. Eight of the food samples and two of the water samples contained more than one isolate or species of enterotoxigenic bacterium. The stability of the LT production by oxidase-positive bacteria and non-E. coli strains was assessed by the rabbit skin and adrenal cell tests after 9 months and 1 year of storage, respectively, in Trypticase soy broth with glycerol at -70 degrees C. Only 33% of the oxidase-positive strains were still LT enterotoxigenic. Of the oxidase-negative strains, 50 and 33% were LT producing at 9 months and 1 year, respectively. None of the E. coli isolates, both enterotoxigenic and nonenterotoxigenic, possessed K88, K99, or colonization factor antigen. The survey demonstrates the presence in food and water of enterotoxigenic bacteria of the same species as those isolated from cases of infantile diarrhea in the same community, although a correlation between these sources and infantile diarrhea remains to be established.

False-negative oxidase reaction as a result of medium acidification.

Acidification of the culture medium may lead to a false-negative result of the oxidase reaction. Hence, if the medium contained a carbon source or another component that is convertible to acid, a negative oxidase reaction should be considered inconclusive. In order to eliminate false-negative reactions, a reagent freshly adjusted to pH 5-7 might be used; this reagent should be checked on known oxidase-negative strains. However, we recommend that the oxidase test be performed with the normal reagent after (sub)culturing on a non-acidogenic medium.

Characteristics of bacteria of the Mima and Herellea genera (tribe Mimeae, DeBord, 1942). I. Morphobiochemical properties and sensitivity to antibiotics

No presente trabalho, os autores estudaram as propriedades morfo-bioquímicas e a sinsibilidade aos antibióticos de 19 amostras de bactérias dos gêneros Mima e Herellea isoladas de material clínico e identificadas como Mima polymorpha variedade oxidans, Mima polymorpha e Herellea vaginicola. No estudo bioquímico observou-se que Herellea vaginicola foi oxidase negativa e em meio complexo nitrogenado, consistentemente ataca a glicose, galactose, manose, arabinose, xilose, lactose a 10% e irregularmente ataca a ramnose e a celobiose; em base sintética nitrogenada, além das atividades citadas, consistentemente produziu ácido a partir da lactose. Mima polymopha foi oxidase negativa, não apresentando atividade glicidolítica, quer em meio complexo nitrogenado, quer em base sintética nitrogenada. Mima polymorpha var. oxidans, foi oxidase positiva, não revelando nenhuma atividade glicidolítica. Herellea vaginicola e Mima polymorpha mostraram grande sensibilidade à gabromicina, knamicina, neomicina, colistin, sendo que a última também foi muito sensível ao cloranfenicol e rovamicina. Mima polymorpha var. oxidans, apresentou grande sensibilidade à knamicina, neomicina, colistin, cloranfenicol e wintomylon. A sensibilidade das amostras a 1 a 0,1 unidade de penicilina/ml, nas condições ensaiadas no presente trabalho, não foi absoluta, como a observada por Baumann, Doudoroff &amp; Stanier (1968a) que permitisse uma separação entre amostras oxidase positiva e negativa ou uma diferenciação dentro do grupo das bactérias oxidase positiva.

TRANSFORMING ACTIVITIES AND BASE COMPOSITION OF DEOXYRIBONUCLEATES FROM STRAINS OF MORAXELLA AND MIMA.

Fourteen strains of Moraxella and possibly allied organisms were studied: M. liquefaciens, M. bovis, M. nonliquefaciens, oxidase-positive and oxidasenegative strains of Mima polymorpha and Herellea vaginicola. Classical bacteriological characteristics, capacity to undergo genetic transformation (resistance to 500 μg. dihydrostreptomycin/ml.), and DNA base composition were examined. Moraxella nonliquefaciens and Mima polymorpha var. oxidans were transformable (2 strains at frequencies of 1-4%). Attempts to elicit transformation of the remaining organisms were unsuccessful. The ability of DNA preparations from M. polymorpha var. oxidans to elicit high frequencies of transformation of Moraxella nonliquefaciens, and vice versa, indicated their close relationship. Moreover, their DNA base contents were indistinguishable (about 44·4% guanine + cytosine, 6 strains). The G + C contents averaged 43·1% for 3 oxidase-negative Mima polymorpha strains and 39·8% for 2 Herellea vaginicola strains.