Chromogenes Strains Research Articles

Phenotypic and genotypic assessment of iron acquisition in diverse bovine-associated non-aureus staphylococcal strains

Although the role of iron in bacterial infections has been well described for Staphylococcus (S.) aureus, iron acquisition in (bovine-associated) non-aureus staphylococci and mammaliicocci (NASM) remains insufficiently mapped. This study aimed at elucidating differences between four diverse bovine NASM field strains from two species, namely S. chromogenes and S. equorum, in regards to iron uptake (with ferritin and lactoferrin as an iron source) and siderophore production (staphyloferrin A and staphyloferrin B) by investigating the relationship between the genetic basis of iron acquisition through whole genome sequencing (WGS) with their observed phenotypic behavior. The four field strains were isolated in a previous study from composite cow milk (CCM) and bulk tank milk (BTM) in a Flemish dairy herd. Additionally, two well-studied S. chromogenes isolates originating from a persistent intramammary infection and from a teat apex were included for comparative purpose in all assays. Significant differences between species and strains were identified. In our phenotypical iron acquisition assay, while lactoferrin had no effect on growth recovery for all strains in iron deficient media, we found that ferritin served as an effective source for growth recovery in iron-deficient media for S. chromogenes CCM and BTM strains. This finding was further corroborated by analyzing potential ferritin iron acquisition genes using whole-genome sequencing data, which showed that all S. chromogenes strains contained hits for all three proposed ferritin reductive pathway genes. Furthermore, a qualitative assay indicated siderophore production by all strains, except for S. equorum. This lack of siderophore production in S. equorum was supported by a quantitative assay, which revealed significantly lower or negligible siderophore amounts compared to S. aureus and S. chromogenes. The WGS analysis showed that all tested strains, except for S. equorum, possessed complete staphyloferrin A (SA)-synthesis and export operons, which likely explains the phenotypic absence of siderophore production in S. equorum strains. While analyzing the staphyloferrin A and staphyloferrin B operon landscapes for all strains, we noticed some differences in the proteins responsible for iron acquisition between different species. However, within strains of the same species, the siderophore-related proteins remained conserved. Our findings contribute valuable insights into the genetic elements associated with bovine NASM pathogenesis.

Increased piglet losses upon exudative epidermitis - a case report

A massive outbreak of exudative epidermitis (EE) occurred on a Western German piglet producing farm with 350 productive sows. Gilts are produced on site. In one group of piglets, more than 50% of suckling and nursery piglets were clinically affected; furthermore, gilts as well as sows showed localized blackish-squamous skin lesions in the neck area. Generalized infection in suckling and nursery piglets resulted in mortality rates of up to 10% per weaning group. Swabs of moist, affected areas of skin taken on the farm in addition to swab and organ samples collected during necropsy were examined via bacterial cultivation. Both Staphylococcus (St.) hyicus and St. chromogenes strains were detected in affected skin lesions, with St. hyicus also present in systemic localizations. Further characterization of the St. hyicus strains identified ExhA and SHETA as toxins involved, and isolates showed resistance to penicillin and aminopenicillin. In the short term, antibiotic treatment with trimethoprim-sulfadiazine of the whole age group combined with individual treatment of severely affected animals as well as washing with an iodine-containing solution improved the clinical signs. In order to reduce the antibiotic use, an autogenous vaccine against the isolated St. hyicus and St. chromogenes strains for gilts and sows was produced and applied as a basic immunization twice before farrowing. In addition, external and internal biosecurity was evaluated and adjusted using an objective questionnaire (Bio-check.UGentTM). The combination of taken measures resulted in a long-term improvement of the overall health status. Several months after the severe EE outbreak, the sporadic occurrence of new EE cases in individual piglets could be controlled by the adjustment of the autogenous vaccine with an additional St. hyicus isolate. The case report illustrates how the combination of continuous monitoring, individual and group antibiotic treatment, biosecurity evaluation, and the use of appropriate immune prophylaxis can improve the clinical picture of EE.

Bovine-associated staphylococci and mammaliicocci trigger T-lymphocyte proliferative response and cytokine production differently

We examined whether distinct staphylococcal and mammaliicoccal species and strains trigger B- and T-lymphocyte proliferation and interleukin (IL)-17A and interferon (IFN)-γ production by peripheral blood mononuclear cells in nulliparous, primiparous, and multiparous dairy cows. Flow cytometry was used to measure lymphocyte proliferation with the Ki67 antibody, and specific monoclonal antibodies were used to identify CD3, CD4, and CD8 T lymphocyte and CD21 B lymphocyte populations. The supernatant of the peripheral blood mononuclear cell culture was used to measure IL-17A and IFN-γ production. Two distinct, inactivated strains of bovine-associated Staphylococcus aureus [one causing a persistent intramammary infection (IMI) and the other from the nose], 2 inactivated Staphylococcus chromogenes strains [one causing an IMI and the other from a teat apex), as well as an inactivated Mammaliicoccus fleurettii strain originating from sawdust from a dairy farm, and the mitogens concanavalin A and phytohemagglutinin M-form (both specifically to measure lymphocyte proliferation) were studied. In contrast to the "commensal" Staph. aureus strain originating from the nose, the Staph. aureus strain causing a persistent IMI triggered proliferation of CD4+ and CD8+ subpopulations of T lymphocytes. The M. fleurettii strain and the 2 Staph. chromogenes strains had no effect on T- or B-cell proliferation. Furthermore, both Staph. aureus and Staph. chromogenes strains causing persistent IMI significantly increased IL-17A and IFN-γ production by peripheral blood mononuclear cells. Overall, multiparous cows tended to have a higher B-lymphocyte and a lower T-lymphocyte proliferative response than primiparous and nulliparous cows. Peripheral blood mononuclear cells of multiparous cows also produced significantly more IL-17A and IFN-γ. In contrast to concanavalin A, phytohemagglutinin M-form selectively stimulated T-cell proliferation.

Chromogenic Escherichia coli reporter strain for screening DNA damaging agents

The presence of pollutants in soil and water has given rise to diverse analytical and biological approaches to detect and measure contaminants in the environment. Using bacterial cells as reporter strains represents an advantage for detecting pollutants present in soil or water samples. Here, an Escherichia coli reporter strain expressing a chromoprotein capable of interacting with soil or water samples and responding to DNA damaging compounds is validated. The reporter strain generates a qualitative signal and is based on the expression of the coral chromoprotein AmilCP under the control of the recA promoter. This strain can be used simply by applying soil or water samples directly and rendering activation upon DNA damage. This reporter strain responds to agents that damage DNA (with an apparent detection limit of 1 µg of mitomycin C) without observable response to membrane integrity damage, protein folding or oxidative stress generating agents, in the latter case, DNA damage was observed. The developed reporter strain reported here is effective for the detection of DNA damaging agents present in soils samples. In a proof-of-concept analysis using soil containing chromium, showing activation at 15.56 mg/L of Cr(VI) present in soil and leached samples and is consistent with Cr(III) toxicity at high concentrations (130 µg). Our findings suggest that chromogenic reporter strains can be applied for simple screening, thus reducing the number of samples requiring analytical techniques.

Randomly amplified polymorphic DNA analysis of Staphylococcus chromogenes isolated from bovine and bubaline mastitis in Karnataka.

Background and Aim:In recent times, non-aureus staphylococci (NAS) have emerged as the major organisms isolated from mastitis cases in dairy animals, with a predominance of Staphylococcus epidermidis and Staphylococcus chromogenes. As compared to Staphylococcus aureus, much less is known about the molecular types or the spatiotemporal epidemiology of these NAS species. In the present study, randomly amplified polymorphic DNA (RAPD) was employed to detect genetic polymorphisms, intraspecies diversity, and epidemiology of S. chromogenes strains (n=37) isolated from bovine and bubaline mastitis cases in the state of Karnataka.Materials and Methods:Thirty-seven S. chromogenes isolates (14 from bovines and 23 from bubaline) isolated from subclinical mastitis cases, from organized and unorganized sectors, were subjected to RAPD typing. Further, methicillin resistance was determined by cefoxitin disk diffusion method.Results:The amplified DNA fragments ranged from 150 to 3000 base pairs and yielded several RAPD profiles. Further analysis using Digital Image Correlation Engine correlation coefficient and UPGMA method showed that the 37 isolates could be classified into 12 distinct RAPD types (A to L) at 62% similarity (D=0.889). Four of the most predominant RAPD types, B, A, C, and E, in that order, and together, represented 65% of the isolates. High diversity was observed among the isolates both within farms and between geographic locations. Most of the isolates exhibited methicillin resistance. This is the first such report from India.Conclusion:In the absence of defined multilocus sequence type protocols or sufficient sequences available in the public domain, RAPD can be employed to determine genetic diversity of S. chromogenes isolates.

Local host response following an intramammary challenge with Staphylococcus fleurettii and different strains of Staphylococcus chromogenes in dairy heifers.

Coagulase-negative staphylococci (CNS) are a common cause of subclinical mastitis in dairy cattle. The CNS inhabit various ecological habitats, ranging between the environment and the host. In order to obtain a better insight into the host response, an experimental infection was carried out in eight healthy heifers in mid-lactation with three different CNS strains: a Staphylococcus fleurettii strain originating from sawdust bedding, an intramammary Staphylococcus chromogenes strain originating from a persistent intramammary infection (S. chromogenes IM) and a S. chromogenes strain isolated from a heifer’s teat apex (S. chromogenes TA). Each heifer was inoculated in the mammary gland with 1.0 × 106 colony forming units of each bacterial strain (one strain per udder quarter), whereas the remaining quarter was infused with phosphate-buffered saline. Overall, the CNS evoked a mild local host response. The somatic cell count increased in all S. fleurettii-inoculated quarters, although the strain was eliminated within 12 h. The two S. chromogenes strains were shed in larger numbers for a longer period. Bacterial and somatic cell counts, as well as neutrophil responses, were higher after inoculation with S. chromogenes IM than with S. chromogenes TA. In conclusion, these results suggest that S. chromogenes might be better adapted to the mammary gland than S. fleurettii. Furthermore, not all S. chromogenes strains induce the same local host response.

Technical note: A pilot study using a mouse mastitis model to study differences between bovine associated coagulase-negative staphylococci

Coagulase-negative staphylococci (CNS) are a group of bacteria classified as either minor mastitis pathogens or commensal microbiota. Recent research suggests species- and even strain-related epidemiological and genetic differences within the large CNS group. The current pilot study investigated in 2 experiments whether a mouse mastitis model validated for bovine Staphylococcus aureus can be used to explore further differences between CNS species and strains. In a first dose titration experiment, a low inoculum dose of S. aureus Newbould 305 (positive control) was compared with increasing inoculum doses of a Staphylococcus chromogenes strain originating from a chronic bovine intramammary infection to a sham-inoculated mammary glands (negative control). In contrast to the high bacterial growth following inoculation with S. aureus, S. chromogenes was retrieved in very low levels at 24 h postinduction (p.i.). In a second experiment, the inflammation inflicted by 3 CNS strains was studied in mice. The host immune response induced by the S. chromogenes intramammary strain was compared with the one induced by a Staphylococcus fleurettii strain originating from cow bedding sawdust and by a S. chromogenes strain originating from a teat apex of a heifer. As expected, at 28 and 48 h p.i., low bacterial growth and local neutrophil influx in the mammary gland were induced by all CNS strains. As hypothesized, bacterial growth p.i. was the lowest for S. fleurettii compared with that induced by the 2 S. chromogenes strains, and the overall immune response established by the 3 CNS strains was less pronounced compared with the one induced by S. aureus. Proinflammatory cytokine profiling revealed that S. aureus locally induced IL-6 and IL-1β but not TNF-α, whereas, overall, CNS-inoculated glands lacked a strong cytokine host response but also induced IL-1β locally. Compared with both other CNS strains, S. chromogenes from the teat apex inflicted a more variable IL-1β response characterized by a more intense local reaction in several mice. This pilot study suggests that an intraductal mouse model can mimic bovine CNS mastitis and has potential as a complementary in vivo tool for future CNS mastitis research. Furthermore, it indicates that epidemiologically different bovine CNS species or strains induce a differential host innate immune response in the murine mammary gland.

Identification of Yellow-Pigmented Bacteria Isolated from Hospital Tap Water in Japan and Their Chlorine Resistance

Twenty-five yellow chromogenic strains isolated from hospital tap water samples collected nationwide were identified by partial 16S rDNA sequencing. In addition, the chlorine resistance of the isolates was experimentally investigated. The results showed that of the strains tested, 12 strains (48.0%) were Sphingomonas ursincola/natatoria, which was most frequently identified, followed by 2 strains (8.0%) of Mycobacterium frederiksbergense and 1 strain (4.0%) each of Sphingomonas adhaesiva, Sphingopyxis witflariensis and Porphyrobacter donghaensis. The other strains were not identified clearly but they belonged to the order of Alphaproteobacteria. On the other hand, the identification results by sequencing and biochemical property testing were not consistent in any of the strains, showing that it was difficult to accurately identify the yellow chromogenic bacteria in tap water based on only their biochemical properties. When the 25 isolates were exposed to 0.1 mg/l residual free chlorine for 1 minute, 22 isolates (88.0%) survived. When the CT (Concentration Time) value killing 99.99% of the bacteria was investigated in 6 of these survivors, M. frederiksbergense (Y-1 strain) was most resistant to chlorine with the CT value of 32 mg x min/l, followed by S. ursincola/natatoria (Y-7 strain) with the CT value of 3.3 mg x min/l. The CT values of Y-5 (Sphingomonas sp.), Y-27 (S. ursincola/natatoria) and Y-21 (Asticacaulis sp.) were within the range of 0.9-0.1 mg x min /l. Of the 6 strains, S. adhaesiva (Y-10) showed the weakest resistance with the CT value of 0.03 mg x min/l. It was clarified that most yellow chromogenic bacteria isolated from hospital tap water were Sphingomonas spp., and these bacteria were experimentally resistant to chlorine.

Identification and antimicrobial susceptibility of Staphylococcus chromogenes isolates from intramammary infections of dairy cows

Staphylococcus chromogenes is a highly prevalent species in subclinical mastitis with a well-established impact on somatic cell count. Few data are available on its antimicrobial susceptibility. The objective of this study was three-fold: (1) to evaluate simple identification tests by comparing them with a genomic method; (2) to determine minimal inhibitory concentrations (MICs) of different antibiotics; (3) to search for the presence of important resistance mechanisms and resistance-determining genes. Seventy-three staphylococcal strains, all collected on different dairy farms, were tentatively identified as S. chromogenes based on their lack of hemolysis and their characteristic intermediate DNase activity. The identification of 70 strains was confirmed as S. chromogenes by tRNA intergenic spacer PCR (tRNA PCR). Three strains were identified as S. sciuri, a species that is naturally cloxacillin- and lincomycin-resistant. All 70 S. chromogenes strains were found to be normally susceptible to neomycin, gentamicin, erythromycin, enrofloxacin, and to penicillinase-stable penicillins and cephalosporins, represented in this study by cloxacillin. The latter result was confirmed by the absence of the mecA gene in each of 13 strains in which this gene was searched for. Twenty-seven (38%) strains were penicillinase producers. Three lincomycin-resistant S. chromogenes strains were found to carry the linA gene. It was concluded that S. chromogenes can be identified reliably in routine mastitis bacteriology, and that the only resistance of importance is against penicillinase-susceptible penicillins.

Pulsed-Field Gel Electrophoresis of Staphylococcus hyicus and Staphylococcus chromogenes Genomic DNA and Its Taxonomic, Epidemiologic and Ecologic Applications in Veterinary Medicine.

One hundred and thirty-eight strains of Staphylococcus hyicus and 21 strains of S. chromogenes isolated from animals were analyzed by pulsed-field gel electrophoresis (PFGE) after restriction endonuclease Smal digestion of chromosomal DNA. Eighty-eight strains of S. hyicus from pigs with or without exudative epidermitis (EE) generated 16 to 26 fragments in the size range of < 1 to 485 kb, and yielded 39 different patterns. With regard to the strains from pigs with EE, PFGE patterns differed according to the country of origin. Outbreaks of EE occurring on four separate pig farms in Japan involved S. hyicus with different PFGE patterns. The PFGE patterns shown by S. hyicus strains from 4 kinds of animals were compared. Strains from pigs differed from those isolated from chickens (n = 45; 18 to 24 fragments of < 1 to 425 kb), cows (n = 3; 17 to 19 fragments of < 1 to 475 kb), and goats (n = 2; 16 or 17 fragments of < 1 to 1,125 kb). Also, each of the chicken, cow and goat strains had a host-specific fragment. The results suggest that PFGE analysis might be a useful marker for distinguishing ecovars within S. hyicus. In contrast, strains of S. chromogenes from pigs and cows generated 17 to 24 fragments ranging from < 1 to 545 kb. The PFGE patterns of S. chromogenes strains were more highly conserved than those of S. hyicus. S. chromogenes strains could be distinguished from S. hyicus strains by fragments within the range of 305 to 545 kb. The results indicate that PFGE analysis could be used to distinguish between S. hyicus and S. chromogenes. We conclude that PFGE analysis is a useful tool not only for species or strain identification but also for epidemiologic or ecologic studies of S. hyicus and S. chromogenes.

Antibacterial Effects of Staphylococcus hyicus and Staphylococcus chromogenes

Skalka B.: Antibacterial Effects of Staphylococcus hyicus and Staphylococcus chromogenes. Acta vet. Bmo, 62, 1993: 39-47. Antibacterial effects of Staphylococcus hyicus (40 strains) and Staphylococcus chromo genes (20 strains) were tested on living and heat-devitalized cells of micrococcal, staphylococcal, streptococcal and corynebacterial indicator strains. All S. hyicus and S. chromo genes strains inhibited the growth of Micrococcus sedentarius and lysed devitalized cells of Micrococcus lylae but did not affect dead cells of M. sedentarius and only few of them inhibited the growth of M. lylae. Only a small number of S. hyicus strains produced intense effects on living indicators and had only very weak effects on their dead cells. The activity of some S. chromogenes strains, observed invariably on living indicators, did not reach the intensity recorded for active S. hyicus strains. Most S. hyicus and S. chromo genes strains were inactive towards the indicators. It is concluded that the antibacterial activity observed in the study should be ascribed to the characteristics of the individual strains and not to the general characteristics of S. hyicus and S. chromo genes species. Staphylococcus hyicus, Staphylococcus chromo genes, antibacterial effects, staphylococcal, micrococcal, streptococcal and corynebacterial indicator strains Staphylococcal exosubstances showing antibacterial activity are represented both by lytic enzymes, lysozyme (Welsch 1959) affecting somemicrococci,lysostaphin (Schindler and Schuhardt 1964) affecting staphylococci, and by substances having bactericidal or bacteriostatic effects, staphylococcins (Fredericq 1946), bacteriocin-like substances (Ivanovics 1962), micrococcins (Su 1948) and antibiotics of low molecular weight (Halbert et a1. 1953). Recently added to the afore-mentioned substances have been exosubstances of the species Staphylococcus hyicus nad Staphylococcus chromo genes. The first report of the antibacterial activity of S. hyicus and S. chromo genes (Balusek and Hajek 1985) described bactericidal and bacteriolytic activity observed in some strains of these two species. The lytic effects in particular then stimulated the interest of further investigators. Miillerand Blobel (1987) reported that a S. hyicus strain produced a bacteriolytic enzyme whose highly purified fractions, LE IlIa and LE IIlb, exerted intense effects on devitalized cells of some streptococci, staphylococci and micrococci. Subsequent studies not only confirm'rd the lytic effects of LE IlIb but also recommended the utilization of this lytic enzyme for extraction of both group and type specific streptococcal antigens (Frede et a1. 1989; Lammler and Wibawan 1990). It was suggested that the production of the lytic enzyme should be regarded as a constant trait of S. hyicus suitable for routine identification of this species (Lammler 1989, 1991a). The production was also described in S. chromogenes and its antigenic identity with the lytic enzyme of S. hyicus was demonstrated (Lammler 1991b). The present study was designed to test the antibacterial effects of S. hyicus and S. chrom()genes on micrococcal, staphylococcal, streptococcal and corynebacterial species with reference to possible practical utilization of these effects. Materials and Methods Culture Media , Brain'Heart Infusion Agar CM 375 (Oxoid Ltd.) and Blood Agar Base No.4 (Imuna) were used. '

Method for in vitro conversion of rough strains of Pseudomonas aeruginosa to smooth strains.

Rough and serologically nontypable strains of Pseudomonas aeruginosa were found to become smooth and typable in vitro when they were maintained in a soft agar containing 0.5% peptone in distilled water and the dried out agar cultures were replenished monthly with a similar peptone solution in distilled water. After about a year, all of the nine rough strains of P. aeruginosa maintained this way became smooth and typable, and their pigmentations also changed significantly. Some melanogenic strains became fluorescine producers, and some weakly chromogenic strains became strong producers of fluorescine and pyocyanin.

Hemolytic Activity of Staphylococcus hyicus and Staphylococcus chromogenes

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The inhibition of Staphylococcus hyicus on a selective medium for staphylococci.

Growth of Staphylococcus hyicus subsp. hyicus and Staph. hyicus subsp. chromogenes strains was found to be severely inhibited when broth cultures of these organisms were streaked on Schleifer and Kramer's staphylococcal (SK) medium. Of the selective agents contained in SK medium, potassium thiocyanate was found to be inhibitory towards both subspecies of Staph. hyicus and sodium azide had an additional inhibitory effect on Staph. hyicus subsp. chromogenes. Of six different media supplements examined, sheep blood and Tween 80 were found to improve the growth of both Staph. hyicus subspecies when added to SK medium. These findings were confirmed in subsequent work where the supplemented SK media were used to isolate potential enterotoxin-producing organisms from simulated raw milk (Staph. aureus, Staph. hyicus subsp. hyicus, Staph. hyicus subsp. chromogenes, Staph. intermedius). SK medium supplemented with sheep blood proved more effective in allowing satisfactory recovery of Staph. aureus, Staph. hyicus subsp. hyicus and Staph. intermedius. However, neither supplement enabled satisfactory recovery of Staph. hyicus subsp. chromogenes to be achieved.

Additional Differentiating Characters of the Two Subspecies of Staphylococcus hyicus

Forty-five strains of Staphylococcus hyicus subsp. hyicus and 36 strains of S. hyicus subsp. chromogenes were examined for bacteriolytic activity with the same assay system previously used in taxonomic studies on staphylococci. The two subspecies differed from each other chiefly in that for optimal lytic activity S. hyicus subsp. hyicus strains required a higher salt concentration in the test medium than S. hyicus subsp. chromogenes strains. The lack of lytic activity on B15TP1 medium was a major difference between S. hyicus and S. aureus, and the lack of activity on TP2P medium was a major difference between S. hyicus and S. intermedius. Penicillin-binding proteins (PBPs) were studied in 40 S. hyicus strains. The S. hyicus subsp. hyicus strains had only one PBP (mol. wt 79 000) while the S. hyicus subsp. chromogenes strains had three distinct PBPs (mol. wts 84 000, 82 000 and 79 000).

Identification of clumping-factor-negative staphylococci isolated from cows’ udders

Identification to species level was attempted on a collection of 954 cultures of catalase-positive, clumping-factor- and beta-haemolysin-negative Gram-positive cocci isolated from teats and milk of cows. Eighty-seven per cent of the strains were identified as Staphylococcus xylosus, S epidermidis, S sciuri, S haemolyticus, S hyicus subsp hyicus and chromogenes, S simulans and S cohnii. Nine per cent of the collection belonged to another group which could not be identified with any of the known Staphylococcus species. Many of the strains of this group and also part of the S epidermidis and S hyicus subsp chromogenes strains examined showed various degrees of growth enhancement on certain media when fatty substances were added. Only nine strains were classified as Micrococcus. A scheme for the identification of coagulase-negative staphylococci from cows' milk is proposed.

A Comparison of Methods and the Validity of Deoxyribonuclease Tests for the Characterization of Staphylococci Isolated from Animals

Strains isolated from pigeons belonging to the coagulase‐positive species Staphylococcus intermedius, coagulase‐negative Staph. hyicus subsp. chromogenes strains from cattle and pigs, and Staph. aureus strains from poultry, gave weakly positive reactions in DNase plate culture tests and heat‐resistant DNase tests. Staph. aureus and Staph. intermedius strains from other sources and coagulase‐negative and coagulase‐positive Staph. hyicus subsp. hyicus strains reacted strongly in these tests. A standardized plate culture test procedure is proposed and the use of DNase tests in the identification of staphylococci isolated from animals is discussed.

Effet de substances tensio-actives sur Mycobacterium tuberculosis et Mycobacterium bovis. Obtention de mycobactéries chromogènes

In 18 strains of M. tuberculosis and M. bovis it has been possible to demonstrate the existence, in pure cultures, of elements able to grow in vitro in scotochromogenic mycobacteria. The experimental method used includes a dispersion, under shaking, of organisms in different surface-active agents. The chromogenic strains isolated during the experimentation are eugonic, and PAS- and INH-resistant. Their experimental virulence is different from that of tubercle bacillus. We discuss the signification of this dissociation phenomenon inductible by surface-active agents.

Studies ofPseudomonas aeruginosaInfections Among Hospitalized Patients

A rapid identification method of glucose nonfermentative gram-negative rods was established and 320 strains isolated were divided into five groups according to their characteristics in pigmentation, acid from glucose, cytochrome oxidase activity and motility. Further characterization of the strains in each group resulted in the identification that the strains in group I were Pseudomonas aeruginosa , strains in group II, P. aeruginosa and Pseudomonas putida. Achromogenic strains of P. aeruginosa were classified into group III, Pseudomonas maltophilia, Pseudomonas alcaligenes and Alcaligenes faecalis into group IV and Acinetobacter calcoaceticus (Acinetobacter anitratus and Achromobacter lwoffii) in group V. When fluorescent pigment production was taken as a standard, 259 out of 263 chromogenic strains were identified as P. aeruginosa and the remaining four were P. putida. Whereas forty-five achromogenic strains included twenty-four A. calcoaceticus, eight P. aeruginosa, six A. faecalis, five P.maltophilia and two P. alcaligenes. From May 1970 to June 1971, 368 strains of glucose nonfermentative rods were isolated from clinical specimens sent to the Central Laboratories of Tohoku University Hospital and three fourth (286/368) of the isolates were P. aeruginosa

XV. Bacteria of two cultivated soils

Summary The bacterial flora of two New Zealand soils under native tussock, introduced pasture, and cultivation for crops is described. Where the change to pasture and cultivation is very recent, there is little change in bacterial numbers but there may be more frequent occurrence of leaf strains in the topsoil until the new vegetation is established. Where the change to pasture and cultivation is well established, there is an increase in numbers associated with an increased amount of organic matter in the soil and a recurrence in the pasture soil of fermenting bacteria present in well established grassland soils. The bacterial flora of the leaves and roots of the tussock and pasture plants was studied and also the air-borne flora. The root flora is similar to the soil flora but with an increased proportion of fermenters. The leaf flora is distinct from the soil and root flora and consists predominantly of chromogenic strains. The air-borne flora, apart from sporogenous types, is similar to the leaf flora.