Comparative in vitro activity of first, second and third generation cephalosporins

Minimum inhibitory concentrations (MIC) were determined against 662 recent clinical isolates for eight cephalosporins representing first, second and third generation compounds. All four third-generation cephalosporins tested (cefoperaxone, cefotaxime, ceftazidime and moxalactam) were significantly more active against aerobic gram-negative bacteria than the older compounds (cephalothin, cefamandole, cefoxitin, and cefuroxime). Cefotaxime and moxalactam were most active against Enterobacteriaceae with extremely low MIC-values. Ceftazidime was definitely most active against Pseudomonas aeruginosa with more than 90% of strains inhibited at 4 micro g/ml. MIC-values for cefotaxime against Staphylococcus aureus were for all strains 1-2 micro g/ml, slightly higher for cefoperazone, while the effect of ceftazidime and moxalactam was more limited. All third generation cephalosporins demonstrated efficiency against Streptococcus pyogenes, cefotaxime being most active and moxalactam least active, but were essentially ineffective against Streptococcus faecalis. Moxalactam demonstrated higher activity against Bacteroides fragilis than other second and third generation cephalosporins including cefoxitin. Previous studies have demonstrated a very high activity of all third generation cephalosporins against Haemophilus influenzae and Neisseria gonorrhoeae, including beta-lactamase producing strains.     

Identifi cation of antibiotics that are effective 2 in eliminatingAgrobacterium tumefaciens

An assay was performed to identify the antibiotics that are most effective againstAgrobacterium tumefaciens strains EHA101 and LBA4404, and to determine if these antibiotics inhibited tobacco callus and shoot formation. We tested ten antibiotics: cefotaxime, carbenecillin, erythromycin, spectinomycin, polymixin B, chloramphenicol, methicillin, Augmentin 500, Augmentin 250, and moxalactam. The effectiveness of each antibiotic against the two strains was determined by measuring the zones of inhibition of bacterial growth in a disk-diffusion assay. The five antibiotics that generated the largest zones of inhibition for each strain were assayed to determine their effects on callus formation. Cefotaxime was the most active antibiotic tested against strain LBA4404, and moxalactam was the most effective antibiotic against EHA101. Both cefotaxime and moxalactam had little or no effect on callus development.     

Analysis of antibiotic resistance and virulence patterns in Klebsiella pneumoniae isolated from human urinary tract infections in India

In this study, 504 urine samples collected from patients suffering from urinary tract infection (UTIs) were screened for the presence of Klebsiella pneumoniae. The overall occurrence of Klebsiella spp. and K. pneumoniae was found to be 23·2% (117/504) and 16·8% (85/504) respectively. Antibiotic susceptibility testing of 85 K. pneumoniae isolates was carried out by disc diffusion which revealed alarming levels of antibiotic resistance (ABR). Antimicrobial resistance was prominently observed against cefpodoxime (76·47%) followed by ampicillin (70·59%), ceftriaxone (52·94%), cefoxitin (50·59%), amoxyclav (48·24%), ofloxacin (45·88%), cefotaxime (44·71%), cefepime (43·53%) and doxycycline hydrochloride (40%). A small percentage of strains also exhibited resistance to other antimicrobials in the range of 7–35%. Around 77·6% of the isolates were found to be resistant to three or more antibiotic classes and 66·7% of the isolates had multiple antibiotic resistance index values >0·2. Screening of virulence genes in 85 K. pneumoniae isolates revealed that uge gene was the most predominant (11/85, 12·9%), followed by rmpA (9/85, 10·5%), kfu (4/85, 4·7%) and aerobactin genes (2/85, 2·35%). Further, the overall percentage of biofilm producers were found to be 17·65% (15/85). This study warrants hospitals and health care centres to reduce misuse of antibiotics and manage UTI with appropriate treatment after performing antibiotic susceptibility testing.     

In vitro effect of subinhibitory concentrations of antibiotics on biofilm formation by clinical strains of Salmonella enterica serovar Typhimurium isolated in Slovakia

Aims: In this study, we examined the biofilm formation of 75 Salmonella enterica serovar Typhimurium (Salm. Typhimurium) human clinical isolates and the effect of subinhibitory concentrations (sub-MICs) of gentamicin, ciprofloxacin and cefotaxime on biofilm formation and exopolysaccharides (EPS) production. Methods and Results: Quantification of biofilm formation and EPS production were carried out using a modified microtitre plate assay and spectrophotometric method, respectively. The results indicate that 38 isolates (50·7%), which are predominantly of DT104 phage type, presented as the strong biofilm producers in vitro on plastic surface. When strains with the highest biofilm-forming capacity were grown in the presence of sub-MICs of gentamicin and ciprofloxacin, the inhibition of biofilm formation and EPS production was observed. In contrast, cefotaxime at 1/2 MIC (0·039 μg ml⁻¹) was able to significantly induce the production of biofilm as well as EPS in three isolates with nontypable and DT104 phage type, respectively. Conclusions: These results clearly indicate that all the three antibiotics tested are able to interfere with biofilm formation and EPS production by Salm. Typhimurium isolates. Significance and Impact of the Study: The current study demonstrated that cefotaxime at sub-MIC can be beneficial for the behaviour of pathogen Salm. Typhimurium in vitro.     

Chromium-resistant bacteria and cyanobacteria: impact on Cr(VI) reduction potential and plant growth

Two chromium-resistant bacterial strains, Bacillus cereus S-6 and Ochrobactrum intermedium CrT-1, and two cyanobacterial strains, Oscillatoria sp. and Synechocystis sp., were used in this study. At initial chromate concentrations of 300 and 600 μg K₂CrO₄ mL⁻¹, and an inoculum size of 9.6×10⁷ cells mL⁻¹, B. cereus S-6 completely reduced Cr(VI), while O. intermedium CrT-1 reduced Cr(VI) by 98% and 70%, respectively after 96 h. At 100 μg K₂CrO₄ mL⁻¹, Synechocystis sp. MK(S) and Oscillatoria sp. BJ2 reduced 62.1% and 39.9% of Cr(VI), respectively, at 30°C and pH 8. Application of hexavalent chromate salts adversely affected wheat seedling growth and anatomical characters. However, bacterial inoculation alleviated the toxic effects, as reflected by significant improvements in growth as well as anatomical parameters. Cyanobacterial strains also led to some enhancement of various growth parameters in wheat seedlings.

     

苏北地区规模化猪场产肠毒素大肠杆菌的分离鉴定及灭活疫苗效果评估

[目的]产肠毒素大肠杆菌(Enterotoxigenic Escherichia coli,ETEC)是引起仔猪腹泻的重要病原菌,本研究通过调查苏北地区规模化猪场ETEC的流行情况,分析其生物学特性,研制具有免疫保护效果的优势血清型菌株的灭活疫苗,以期对苏北地区ETEC的防控提供参考。[方法]从苏北地区规模化猪场采集3-30日龄的仔猪新鲜粪样、肛拭子及小肠组织样,分离出ETEC,对分离菌株进行血清型鉴定、耐药性测定、小鼠致病力测定;最后通过动物免疫试验研究优势血清型菌株灭活疫苗对小鼠的免疫保护效果。[结果]从21个规模化猪场采集病料562份,通过PCR鉴定及测序得到141株ETEC;血清凝集试验鉴定出85株菌的O抗原血清型,其中08、0101和0128为优势血清型,占定型菌株的61.2%(52/85),其他血清型包括09、03、020、0148、0149等;分析141株ETEC对14种常见抗生素的耐药情况,得出分离株对新霉素、红霉素、四环素、庆大霉素、强力霉素、阿莫西林、甲氧苄啶/磺胺甲恶唑高度耐药,耐药率均高达80%以上;对恩诺沙星敏感性较高,敏感率达50.4%(71/141);对多粘菌素B和头孢噻肟中介耐药,占比分别为66%(93/141)和51.8%(73/141);多重耐药现象严重,其中10重耐药的菌株占比最大,为19%(27/141);小鼠攻毒试验测得08血清型强毒株YC-6的半数致死量(median lethal dose,LD50)为1.4×10^7 CFU/只,最低致死量(minimum lethal dose,MLD)为3×10^7 CFU/只;08血清型强毒株YC-6和0101血清型强毒株LYG-3制备的单价灭活疫苗对小鼠的保护率均达到100%,因此利用08血清型强毒株YC-6和0101血清型强毒株LYG-3研制二价灭活疫苗,结果显示该二价疫苗对感染不同血清型ETEC小鼠的保护率在83%以上。[结论]本研究通过对苏北地区ETEC的流行病学调查,得出其优势血清型,并研制出针对对优势血清型免疫保护效果较好的二价灭活疫苗,给临床ETEC的监测和防控提供参考。     

Isolation and pathogenicity of some South African entomopathogenic fungi (Ascomycota) against eggs and larvae of Cydia pomonella (Lepidoptera: Tortricidae)

Virulent entomopathogenic fungal strains against Cydia pomonella (Lepidoptera: Tortricidae) were isolated and identified in the Western Cape Province of South Africa. Thirty-nine isolates belonging to six species were obtained using the insect bait method. Generally, Metarhizium robertsii (Ascomycota: Hypocreales) was the most frequently encountered species representing 51% of the total number of isolates collected from the soil samples. This is the first report of M. robertsii from southern Africa. Mortality data from an immersion bioassay indicated that the 39 fungal isolates were pathogenic against fifth instar larvae of C. pomonella inducing 47–85% insect mortalities. Two M. robertsii strains, MTL151 and GW461, induced 85% larval mortality and were selected for further evaluations. The exposure of freshly laid eggs to wax papers that were pre-treated with fungal spores ranging from 10³ to 10⁸ spores ml^?1 of MTL151 and GW461 resulted in a significant reduction of egg hatchabilities, from 95 to 66% and 93 to 71%, respectively as spore concentration increased. First instar larval neonates were exposed to apples that were pre-sprayed topically with varied conidia suspensions (10³?10⁸ spores ml^?1). The mean percentage of participating apples with larvae in their cores/flesh significantly reduced from 53 to 10% (MTL151) and 76 to 10% (GW461) of 10 apples, and a concurrent decrease in the incidence of apple fruit rot was observed as conidia concentration increased. Up to 90% of apples treated with 1 × 10⁸ spores ml^?1 had no larvae present in their cores and this result compared favourably with the commercial pesticide Fruitfly®, containing the active ingredient cypermethrin (20 g/l) used at a recommended dose of 0.25 ml/250 ml of water.     

High levels of multiple metal resistance and its correlation to antibiotic resistance in environmental isolates of Acinetobacter

Forty strains of Acinetobacter were isolated from different environmental sources. All the strains were classified into four genospecies, i.e. A. baumannii (33 isolates), A. calcoaceticus (three isolates), A. junii (three isolates) and A. genospecies3 (one isolate). Susceptibility of these 40 strains to salts of 20 heavy metals and 18 antibiotics was tested by the agar dilution method. All environmental isolates of Acinetobacter were resistant to multiple metal ions (minimum 13 metal ions) while all but one of the strains were resistant to multiple antibiotics (minimum four antibiotics). The maximum number of strains were found to be sensitive to mercury (60% strains) while all strains were resistant to copper, lead, boron and tungsten even at 10 mm concentration. Salts of these four metal ions may be added to the growth medium to facilitate selective isolation of Acinetobacter. Rifampicin and nalidixic acid were the most toxic antibiotics, inhibiting 94.5 and 89.5% of the acinetobacters, respectively. A. genospecies3 was found to be the most resistant species, tolerating high concentrations of all the 20 metal ions and also to a greater number of antibiotics than any other species of Acinetobacter tested. An inhibitory concentration (10 mm) of Ni²⁺ and Zn²⁺ was observed to inhibit the growth of all of the clinical isolates but allowed the growth of the environmental isolates, facilitating the differentiation between pathogenic and non-pathogenic acinetobacters.     

Variation of Fungicide Resistance in Czech Populations of Pseudoperonospora cubensis

During the growing seasons between the years 2001 and 2004, 98 isolates of Pseudoperonospora cubensis from nine regions of Czech Republic were collected and screened for tolerance/resistance to the three frequently used fungicides (propamocarb, fosetyl‐Al, metalaxyl). Fungicides were tested in five different concentrations, using a floating disc bioassay. Fungicide effectiveness varied considerably. Propamocarb appeared most effective and all the isolates collected in the years 2001–2003 were found sensitive to all tested concentrations [607–9712 μg active ingredient (a.i.)/ml]. In 2004, some strains with increased resistance to propamocarb were detected. These strains were characterized by tolerance at the lowest concentrations (607 μg a.i./ml, eventually on 1214 μg a.i./ml); however, they were controlled by 2428 μg a.i./ml. Fosetyl‐Al was effective at the recommended concentration of 1600 μg a.i./ml against all isolates. However, the occurrence of isolates (collected in 2001) which sporulated at low concentrations (400 and 800 μg a.i./ml) indicated that the selection for tolerance occurs in the pathogen population. Nevertheless, this phenomenon was not confirmed with the P. cubensis isolates collected between the years 2002 and 2004. Metalaxyl was found ineffective, because 97% of the isolates showed the resistance to the recommended concentration (200 μg a.i./ml), and the other 3% of isolates expressed tolerant response. The majority of the isolates showed profuse and/or limited sporulation at higher concentrations (400 and 800 μg a.i./ml). A substantial shift to highly metalaxyl resistant strains was evident in the Czech P. cubensis populations during 2001–2004.     

Characteristics of clinical<Emphasis Type="Italic">Acinetobacter</Emphasis> spp. strains

Resistance to 13 antimicrobial agents, resistance to the bactericidal activity of human serum, hydrophobic properties, lipolytic activity and production of histamine were determined in a total of 50 clinicalAcinetobacter spp. strains (A. baumannii, A. lwoffii, A. calcoaceticus, A. haemolyticus). None of the tested isolates showed resistance to meropenem and none ofA. lwoffii, A. calcoaceticus andA. haemolyticus strains were resistant to amikacin. Forty-six strains (92 %) manifested resistance to ampicillin, 90 % to cefuroxime, 68 % to ciprofloxacin, 58 % to piperacillin, gentamicin and cotrimaxazole, 50 % to cefotaxime, 44 % to amikacin, 42 % to ceftazidime, 38 % to piperacillin/tazobactam, 24 % to netilmicin and 16 % to ampicillin/sulbactam. In particular,A. baumannii andA. calcoaceticus strains showed considerable antibiotic resistance. Thirty-one isolates (62 %) showed serum resistance; intermediate sensitivity was found in 19 isolates (38 %). The majority of the strains (72 %) demonstrated a strongly hydrophobic character; 16 % of isolates exhibited moderate hydrophobic properties. All strains showed lipolytic activity; production of histamine was detected in 14 of 43 strains examined.     

Isolation of algicidal compounds from the red alga <Emphasis Type="Italic">Corallina pilulifera</Emphasis> against red tide microalgae

We determined the structure of two compounds, namely, 5,8,11,14,17-eicosapentaenoic acid (EPA) and di-n-octylphthalate (DnOP), which have algicidal activity against the toxic dinoflagellate, Cochlodinium polykrikoides. The polyunsaturated fatty acid EPA and the anthropogenic DnOP were isolated from the MeOH extract of the red alga Corallina pilulifera. We also found that a commercial EPA has algicidal activity identical to that of the EPA purified from C. pilulifera. At low inoculum (5.0 × 10² cells mL⁻¹), the highest algicidal activity of a commercial EPA exhibited approximately 92.6% algicidal activity after 1 h and 96.8% after 6 h treatment at 6 μg mL⁻¹, respectively. At high inoculum (1.0 × 10⁴ cells mL⁻¹), the strongest algicidal activity of EPA showed 69.5% after 1 h and 75.5% algicidal activity after 6 h treatment at 6 μg mL⁻¹, respectively. However, EPA did not show algicidal activity against several microalgae used in aquaculture such as Pavlova lutheri, Tetraselmis suecica, Isochrysis galbana, and Nannochloris oculata for 6 h treatment at 6 μg mL⁻¹. The algicidal activity of the five red tide strains to EPA (3 μg mL⁻¹) showed about 86.6%, 86.6%, and 67.3% algicidal activity against Skeletonema costatum, Chaetoceros curvisetus, and C. polykrikoides after 1 h treatment at low inoculum (5.0 × 10² cells mL⁻¹), respectively, but not against Prorocentrum minimum and Scrippsiella trochoidea. We concluded that EPA might be useful as a controlling agent of harmful algal blooms.     

The patterns and transmissibility of antibiotic resistance among clinical strains of Pseudomonas aeruginosa.

Four hundred and ninety-eight predominantly pyocin-type 10 clinical strains of Pseudomonas aeruginosa were analyzed for resistance to carbenicillin, cefoperazone, cefotaxime, ceftazidime, gentamicin, amikacin and netilmicin. Based on NCCLS-recommended MIC breakpoints, 245 strains were found to be resistant, of which 41.6% were resistant to carbenicillin, 38% to gentamicin, 37.8% to netilmicin, 26.3% to cefoperazone, 17.9% to cefotaxime, 0.6% to amikacin and none to ceftazidime. Quadruple resistance to carbenicillin, cefoperazone, gentamicin and netilmicin was the most frequent pattern observed. Resistance to older antibiotics (kanamycin, streptomycin and tetracycline) and to mercuric chloride were also common. Conjugation experiments suggested that self-transmissible and non-transmissible plasmids occurred in at least 66 strains.     

A new microbial consortia containing entomopathogenic fungus,Beauveria bassiana and plant growth promoting rhizobacteria,Pseudomonas fluorescens for simultaneous management of leafminers and collar rot disease in groundnut

The virulence of 20 isolates of Beauveria bassiana (Balsamo) Vuillemin to larvae of the leafminer, Aproaerema modicella, was tested in the laboratory. Leafminer larvae were sprayed with a standard concentration of 1×10⁸ condia/mL of each B. bassiana isolate. All the B. bassiana isolates tested were pathogenic to A. modicella and the mortality varied between 16.7 and 68.9%. Beauveria bassiana isolate B2 was found to be the most virulent followed by isolate B4 which resulted in 59% mortality. Beauveria isolate B2 was selected for dose–response mortality studies with four different doses (1×10², 1×10⁴, 1×10⁶ and 1×10⁸ conidia/mL). Among the various doses tested, 1×10⁸ conidia/mL produced the highest mortality (70.7%). In addition, morphogenesis of the insect pest in all stages, larval, pupal and adult was greatly affected due to fungal infection. Further, B. bassiana isolate B2 and two Pseudomonas fluorescens strains, TDK1 and Pf1 were tested alone and in combination for suppression of groundnut leafminer and collar rot disease and promotion of plant growth and yield both under glasshouse and field conditions. The mixture of B. bassiana and P. fluorescens strains significantly reduced the leafminer and collar rot disease incidences when applied as talc-based formulation through seed, soil and foliar application under glasshouse and field conditions.     

Analysis of pristinamycin-resistant Staphylococcus epidermidis isolates in the Tunisian Bone Marrow Transplant Center

Aims: We report the analysis of genetic determinants conferring resistance to pristinamycin in Staphylococcus epidermidis strains and epidemiology typing of these strains by pulsed‐field gel electrophoresis. Methods and Results: Staphylococcus epidermidis (346 isolates) were searched for strains with pristinamycin resistance. Pristinamycin‐resistant strains (seven isolates) were isolated in five patients with haematological cancer in the Bone Marrow Transplant Centre of Tunisia in 2002. Resistance to pristinamycin was observed in 2% of isolates. The seven pristinamycin‐resistant strains shared resistance to oxacillin (MIC = 8–512 μg ml^?1), gentamicin (MIC = 16–512 μg ml^?1), erythromycin (MIC > 1024 μg ml^?1), lincomycin (MIC > 1024 μg ml^?1), pristinamycin (MIC = 4–16 μg ml^?1) and rifampin (MIC = 128–256 μg ml^?1). erm genes were amplified: ermA from six strains and ermC from one. vga gene encoding streptogramins A resistance (pristinamycin résistance) was amplified from all strains and typed as vgaA by analysis after electrophoresis of restriction profiles of vga amplicons (two fragments with Sau3A of 164 and 378 bp; one fragment with EcoRI). Pulsed‐field gel electrophoresis (PFGE) of SmaI chromosomal DNA digests of the seven S. epidermidis isolates divided them into two distinct pattern types: pulsed‐field type A (classified from A1 to A6 subtypes) and type B. The six strains harbouring ermA genes belonged to the PFGE type A while the strain harbouring ermC genes belonged to the PFGE type B. We characterized an epidemic strain carrying the vgaA and ermA genes responsible for the outbreak. Conclusions: Two clones of pristinamycin‐resistant S. epidermidis were isolated in our patients. One of them, isolated in all patients, had expanded over six months suggesting acquisition by cross‐contamination. Significance and Impact of the study: Increasing isolation of pristinamycin resistant S. epidermidis strains is an alarming indicator of nosocomial dissemination. The vector will be determined to establish a system of epidemiological surveillance.     

Antibiotic resistance of <Emphasis Type="Italic">Stenotrophomonas maltophilia</Emphasis> strains isolated from captive snakes

The minimum inhibitory concentrations (MICs) of 24 antibiotics were determined for 45 Stenotrophomonas maltophilia strains by the microdilution method at 37 and 30 °C (after 24 h and 48 h of incubation). The isolates were obtained from mouth swabs and pus of 116 captive snakes whereas the identical strains (based on PFGE) of the same origin were discarded. At 37 °C, the isolates showed a low frequency of resistance to levofloxacin (0 and 8.9 % of resistant strains after 24 and 48 h, MICs₅₀ 0.5 and 1 mg/L, MICs₉₀ 1 and 2 mg/L) and cotrimoxazole (2.2 % of resistant strains for 24 and 48 h, MICs₅₀ 4 mg/L for both time periods, MICs₉₀ 4 and 8). At 30 °C, the most effective drugs were also cotrimoxazole (2.2 and 6.7 %, MICs₅₀ 4 and 8, MICs₉₀ 8 and 32) and levofloxacin (8.9 and 46.7 %, MICs₅₀ 1 and 2, MICs₉₀ 2 and 4). The isolates were either identically or more susceptible to antibiotics than strains acquired from patients hospitalized at Olomouc University Hospital (the same region) with the exception of ciprofloxacin, cefoperazone, cefoperazone/sulbactam and ceftazidime.     

Antimicrobial susceptibility, β-lactamase and enterotoxin production in <Emphasis Type="Italic">Bacillus cereus</Emphasis> isolates from clinical and food samples

The antimicrobial susceptibility of 30 clinical and 30 food Bacillus cereus isolates was determined. All isolates were susceptible to streptomycin, ciprofloxacin and gentamicin, 90 % of them to clindamycin and vancomycin, and 67 % to erythromycin. All isolates were resistant to amoxicillin with clavulanic acid, ampicillin, cefotaxime, ciprofloxacin, cloxacillin, cefotaxime with clavulanic acid and penicillin. The MIC values (determined by E-tests) were 48–256 mg/L for ampicillin, 0.19–1.5 mg/L for gentamicin, 0.125–1.0 mg/L for clindamycin, 0.047–4.0 mg/L for erythromycin and 1.5–16 mg/L for vancomycin. The MICs 4.6–18.75 g/L were observed for penicillin using the microdilution method. The presence of metallo-β-lactamases was detected by E-test for 100 % of strains. Nonhemolytic diarrheal enterotoxin (NHE) was produced by 98.3 % of strains, while 31.7 % of them produced hemolytic diarrheal enterotoxin (HBL). Clinical isolates produced 10 % more HBL than food isolates. The psychrotrophic strains isolated from food samples produced NHE at 6.5 °C in 73 % of cases.     

Competition studies withRhizobium trifolii in laboratory experiments

Summary Competition studies were carried out in soil cores by comparing the nodule forming ability of antibiotic resistance marked strains, inoculated at three inoculum levels onTrifolium repens versus an effective indigenous Rhizobium population of 1.5×10⁵/gm. It was seen that the indigenous marked isolate G1067 formed a high proportion of nodules sampled (>90%) at all three inoculum levels (10⁵, 10⁷ and 10⁹ cells/seed) wherein the introduced foreign strain G1032 formed >50% of the nodules at the highest inoculum level.In a test tube experiment, competition for nodule sites was examined by inoculating mixtures of twoR. trifolii strains at different input levels on two cultivars ofTrifolium repens var. Huia and Titan. It was seen that G1032 was less competitive than G1006 and G1067 on cv. Huia but was more competitive on cv. Titan than the other two strains.     

Bacterial Rot of Dieffenbachia maculata (Lodd.) G. Don. Caused by Erwinia chrysanthemi

Five bacterial isolates were obtained in a nursery near Gent (Belgium) from diseased Dieffenbachia maculata (Lodd.) G., Don. cv. Compacta, cv. Camillo and cv. Veerle plants. They were identified by API 20E, API 50 CHE and API ZYM systems as Erwinia chrysanthemi. These strains and seven collection strains were pathogenic to all three D. maculata cultivars tested: cv. Camillo, cv. Compacta and cv. Tropic Snow. Inoculation in the stem or petiole was the only effective method for obtaining systemic infection. The petiole appeared to be the part of the plant in which disease developed most readily. Wounding was required for the induction of the disease. Temperatures between 25° and 30° C, a relative air humidity of 75 % or more and low light intensity (0.5 ft-c) favoured the disease, whereas high inoculum sizes (10⁶ or more cells) accelerated and increased it. Histological studies showed tissue degradation in infected areas. Petioles were most severely affected. Transport of bacteria seemed to occur after vessel infection in stem or petiole tissues.     

浙江某市屠宰场猪链球菌血清型、耐药及致病特征

【目的】猪链球菌(Streptococcus suis)是猪的重要病原菌,同时也是人畜共患病原。猪的扁桃体是猪链球菌主要定殖部位之一,是易感猪和人的重要传染源。因此,对屠宰场健康猪进行猪链球菌流行病学调查,具有重要的公共卫生学意义。【方法】本研究自2020年至2021年,从浙江某市屠宰场采集健康猪扁桃体样品,分离鉴定猪链球菌,采用血清型特异性PCR法分型,通过耐药基因检测、药敏试验、斑马鱼毒力实验分析其耐药及致病特征。【结果】131份健康猪扁桃体样品猪链球菌阳性率为62.59%(82/131),共分离猪链球菌68株,其中16型分离率最高,占比16.18%(11/68),其次为31型(11.76%,8/68)、9型(7.35%,5/68)、3型(7.35%,5/68)等。含2种及以上血清型的扁桃体样品占15.85%(13/82)。药敏试验表明,分离株主要对林可酰胺类(100%,68/68)、大环内酯类(98.53%,67/68)、四环素类(100%,68/68)抗生素耐药,所有菌株均属于多药耐药。值得关注的是,有18株菌对青霉素耐药、3株菌对头孢噻肟耐药、2株菌对利福平耐药、11株菌对利...     

New bacilli from shallow hydrothermal vents of Panarea Island (Italy) and their biotechnological potential

Aims: To characterize bacilli isolated from shallow hydrothermal vents of Panarea Island (Italy) and evaluate their biotechnological potential. Methods and Results: Fifteen isolates were characterized by culture and molecular methods. Eleven isolates were thermophilic, six isolates were alkalophilic and four of them were haloalkalophilic. After 16S rRNA gene sequencing, four strains, exhibiting sequence similarity below 95% with deposited strains, may represent novel species of bacilli. One strain was strictly related to Geobacillus subterraneus, but shared phenotypic characteristics for which it could be considered a new strain of this species. Four strains were affiliated with different Bacillus spp. Most isolates produced gelatinase, lipases and amylase, and some were mercury tolerant. Exopolysaccharides (EPS) production was tested adding different sugars (glucose, sucrose, trehalose, fructose, ribose, xylose and mannose, 1% w/v) as a carbon source in a minimal medium. The highest EPS yield (185 mg l^?1) was reached by strain 1A70 utilizing ribose as a carbon source. Conclusions: Novel strains of Geobacillus and indigenous ribotypes of Bacillus with biotechnological potential inhabit shallow vents of Panarea Island. Significance and Impact of the Study: New strains of thermophilic bacilli from Panarea are producers of useful biomolecules for industrial purposes as well as environmental and biotechnological applications.