Ecological Characterisation of the Colonic Microbiota in Arctic and Sub-Arctic Seals

Dominant colonic bacteria in wild hooded (n = 9), harbour (n = 1) and grey (n = 1) seals were identified using 16S rRNA gene clone libraries (313 clones), revealing 52.7% Bacteroidetes, 41.5% Firmicutes, 4.5% Proteobacteria and 1.0% Fusobacteria. Thirty (77%) of the 39 phylotypes identified were novel, showing <97% sequence similarity to their nearest cultivated relatives. Mean colonic bacterial cell density, determined by real-time PCR, was high (12.8 log₁₀ cells/g wet wt) for the hooded seals, while the number of methanogenic Archea was low (4.0 log₁₀ cells/g wet wt). The level of ampicillin (amp^r) and tetracycline-resistant (tet^r) isolates was investigated by cultivation. Aerobic amp^r isolates were only detected in colon contents from four hooded seals, whereas aerobic tet^r isolates were found in seven of the nine hooded seals. These data provide novel insight to the gut microbiota of Arctic and sub-Arctic seals living in the wild.     

Plasmid-mediated drug resistance of shigellae in Kuwait

Of 153 clinical isolates of shigellae examined, 64.7% belonged toShigella flexneri, 18.9% toSh. sonnei, 11.8% toSh. boydii and 4.6% toSh. dysenteriae. Part of these isolates were resistant to sulfamethoxazole and streptomycin (88.2% each), ampicillin (66.70, tetracycline (63.40 and co-trimoxazole (43.10, with levels of resistance (MIC₅₀ and MIC₉₀) being invariably high. Resistance to three or more drugs (multidrug resistance) was seen in 77.8% of the isolates. All the 25 strains examined for transfer of resistance contained R-plasmids, both autotransferable and non-autotransferable (mobilized by transfer factor X). The frequency of transfer of different r-determinants varied from 2.7 · 10^–8 to 1.4 · 10.     

Impact of Three Ampicillin Dosage Regimens on Selection of Ampicillin Resistance in Enterobacteriaceae and Excretion of blaTEM Genes in Swine Feces

The aim of this study was to assess the impact of three ampicillin dosage regimens on ampicillin resistance among Enterobacteriaceae recovered from swine feces by use of phenotypic and genotypic approaches. Phenotypically, ampicillin resistance was determined from the percentage of resistant Enterobacteriaceae and MICs of Escherichia coli isolates. The pool of ampicillin resistance genes was also monitored by quantification of bla_TEM genes, which code for the most frequently produced β-lactamases in gram-negative bacteria, using a newly developed real-time PCR assay. Ampicillin was administered intramuscularly and orally to fed or fasted pigs for 7 days at 20 mg/kg of body weight. The average percentage of resistant Enterobacteriaceae before treatment was between 2.5% and 12%, and bla_TEM gene quantities were below 10⁷ copies/g of feces. By days 4 and 7, the percentage of resistant Enterobacteriaceae exceeded 50% in all treated groups, with some highly resistant strains (MIC of >256 μg/ml). In the control group, bla_TEM gene quantities fluctuated between 10⁴ and 10⁶ copies/g of feces, whereas they fluctuated between 10⁶ to 10⁸ and 10⁷ to 10⁹ copies/g of feces for the intramuscular and oral routes, respectively. Whereas phenotypic evaluations did not discriminate among the three ampicillin dosage regimens, bla_TEM gene quantification was able to differentiate between the effects of two routes of ampicillin administration. Our results suggest that fecal bla_TEM gene quantification provides a sensitive tool to evaluate the impact of ampicillin administration on the selection of ampicillin resistance in the digestive microflora and its dissemination in the environment.     

Isolation and Characterization of Endophytic Colonizing Bacteria from Agronomic Crops and Prairie Plants

Endophytic bacteria reside within plant hosts without causing disease symptoms. In this study, 853 endophytic strains were isolated from aerial tissues of four agronomic crop species and 27 prairie plant species. We determined several phenotypic properties and found approximately equal numbers of gram-negative and gram-positive isolates. In a greenhouse study, 28 of 86 prairie plant endophytes were found to colonize their original hosts at 42 days postinoculation at levels of 3.5 to 7.7 log₁₀ CFU/g (fresh weight). More comprehensive colonization studies were conducted with 373 corn and sorghum endophytes. In growth room studies, none of the isolates displayed pathogenicity, and 69 of the strains were recovered from corn or sorghum seedlings at levels of 8.3 log₁₀ CFU/plant or higher. Host range greenhouse studies demonstrated that 26 of 29 endophytes were recoverable from at least one host other than corn and sorghum at levels of up to 5.8 log₁₀ CFU/g (fresh weight). Long-range dent corn greenhouse studies and field trials with 17 wild-type strains and 14 antibiotic-resistant mutants demonstrated bacterial persistence at significant average colonization levels ranging between 3.4 and 6.1 log₁₀ CFU/g (fresh weight) up to 78 days postinoculation. Three prairie and three agronomic endophytes exhibiting the most promising levels of colonization and an ability to persist were identified as Cellulomonas, Clavibacter, Curtobacterium, and Microbacterium isolates by 16S rRNA gene sequence, fatty acid, and carbon source utilization analyses. This study defines for the first time the endophytic nature of Microbacterium testaceum. These microorganisms may be useful for biocontrol and other applications.     

Resistance to Antimicrobial Agents in Lactobacilli Isolated from Caper Fermentations

A collection of lactobacilli comprising species of Lactobacillus plantarum (43 isolates), Lactobacillus brevis (9 isolates) and Lactobacillus fermentum (6 isolates) obtained from spontaneous fermentations of capers (the fruits of Capparis spinosa) were investigated for resistance to antimicrobial agents. All isolates were resistant to vancomycin and teicoplanin (MIC > 16 μg/ml). Resistance to ciprofloxacin (MIC > 2 μg/ml) was detected in all isolates of L. brevis and L. fermentum as well as in most isolates of L. plantarum, whilst resistance to levofloxacin showed a much lower incidence. Among L. plantarum and L. brevis isolates, low levels of resistance to tetracycline and/or nitrofurantoin were detected. Higher resistance levels were also detected in some isolates. Resistance to penicillin and rifampicin were also detected among L. plantarum isolates. All isolates were sensitive to ampicillin, erythromycin, chloramphenicol, gentamicin, streptomycin, and quinupristin/dalfopristin.     

Cultural,morphological and bio-chemical variability of different isolates of Colletotrichum truncatum causing anthracnose of greengram

A laboratory experiment was conducted to study the variability among the eight isolates of Colletotrichum truncatum of greengram collected from different locations on the basis of cultural, morphological and biochemical characteristics by using nine different culture media viz., Potato Dextrose Agar (PDA), Potato Carrot Agar (PCA), Oat Meal Agar (OMA), Corn Meal Agar (CMA), Carrot Agar (CA), Sabouraud’s Agar (SA), Czapek’s Dox Agar (CDA), Richard’s Agar (RA) and V₈ Juice Agar. Colony colour varied in different media from white or white with light brown centres which later changed to black or dark to light brown with increase in the age of the fungal cultures. Mostly, the colonies had fluffy or cottony mycelial growth with slight variations and regular to irregular white margin. PDA, PCA, CA and RA produced maximum mycelial growth (90?mm) at 10 DAI (days after inoculation). Minimum growth was observed on SA (69.56?mm) and V₈ juice agar media (55.42?mm) and their difference was statistically significant. Morphological variability among the isolates was studied by comparing their conidial length, breadth and length and breadth of setae and their differences were statistically significant. Biochemical variability among the isolates was based on α- and β-esterase and peroxidise profiling. Positive activity was observed for both α- and β-esterase. α-Esterase enzyme showed the highest enzyme activity in terms of maximum numbers of banding loci among the three isozymes tested. The findings of the present study clearly revealed that cultural, morphological and biochemical variability did exist among the different isolates of C. truncatum.     

Transfer of ampicillin resistance from Salmonella Typhimurium DT104 to Escherichia coli K12 in food

Aims: To investigate the transfer of antibiotic resistance from a donor Salmonella Typhimurium DT104 strain to a recipient Escherichia coli K12 strain. Methods and Results: Mating experiments were conducted in broth, milk and ground meat (beef) at incubation temperatures of 4, 15, 25 and 37°C for 18 and 36 h. Ampicillin‐resistance transfer was observed at similar frequencies in all transfer media at 25 and 37°C (10^?4 to 10^?5 log₁₀ CFU ml g^?1, transconjugants per recipient) for 18 h. At 15°C, transfer was observed in ground meat in the recipient strain (10^?6, log₁₀ CFU g^?1, transconjugants per recipient), but not in broth or milk. At 4°C, transfer did not occur in any of the examined mediums. Further analysis of the E. coli K12 nal^R transconjugant strain revealed the presence of a newly acquired plasmid (21 kbp) bearing the β‐lactamase gene bla_TEM. Transconjugants isolated on the basis of resistance to ampicillin did not acquire any other resistant markers. Conclusion: This study demonstrates the transfer of antibiotic resistance in food matrices at mid‐range temperatures. Significance and Impact of the Study: It highlights the involvement of food matrices in the dissemination of antibiotic‐resistant genes and the evolution of antibiotic‐resistant bacteria.     

Ubiquinone systems in fungi. V. Distribution and taxonomic implications of ubiquinones in Eurotiales, Onygenales and the related plectomycete genera, except for Aspergillus, Paecilomyces, Penicillium, and their related teleomorphs

The ubiquinone (coenzyme Q) systems were determined for 176 teleomorphic isolates, 14 anamorphic isolates, and three samples of fruit-bodies of Dendrosphaera eberhardtii, which belonged to Eurotiales, Onygenales, and related taxa. In Eurotiales, Ascosphaera had Q-9, whereas Bettsia had Q-10. All isolates of Monascaceae had the Q-10 system, whereas those of four genera of Pseudeurotiaceae had the Q-10(H₂) system. The Q-10(H₂) system was found in genera of Trichocomaceae, except for Aspergillus, Penicillium, Paecilomyces, and their related taxa. However, Thermoascus had the Q-9 system. In Onygenales, members of Arthrodermataceae had Q-9, and those of Gymnoascaceae had Q-10(H₂). Isolates of Myxotrichaceae were characterized by Q-10(H₂) with few exceptions, which had Q-10. The quinones of Onygenaceae belonged to complex systems, i.e., Q-9, 0-10 and 0-10(H₂), and a combination of two systems. Families Onygenaceae and Trichocomaceae are likely a phylogenetic heterogeneity. Ubiquinone analysis provides a very useful criterion of great promise for classifying eurotialean taxa and also for identifying their isolates.     

Isolation and Identification of Ruminal Methanogens from Grazing Cattle

To obtain information on the diversity of ruminal methanogens in grazing animals, three ruminal methanogens from grazing cattle were characterized and identified. Two of the isolates were rod-shaped, with one staining Gram-positive and being non-motile (BRM9), and the other (BRM16) staining Gram-negative and being motile. These isolates grew only on H₂/CO₂ and formate, and optimally at 38°C and pH 6.5–7.0. The third isolate (CM1) was non-motile, pseudosarcina-shaped, and grew on H₂/CO₂, acetate, and methyl-containing compounds, with optimal growth at 40°C and pH 6.5. DNA was prepared from the three isolates, and their 16S rRNA genes were sequenced. Phenotypic data and comparisons of nearly complete 16S rDNA sequences showed that BRM9, BRM16, and CM1 are strains of Methanobacterium formicicum, Methanomicrobium mobile, and Methanosarcina barkeri respectively. To the best of our knowledge, this is the first information on ruminal methanogens in cattle maintained under grazing management. Received: 26 October 1999 / Accepted: 22 November 1999     

Antimicrobial resistance patterns and characterization of integrons of <Emphasis Type="Italic">Shigella sonnei</Emphasis> isolates in Seoul, 1999–2008

A total of 66 Shigella sonnei isolates from 1999 to 2008 in Seoul was analyzed for their antimicrobial resistance, carriage of integron, and the patterns of Pulsed-field gel electrophoresis (PFGE). A high level of antimicrobial resistance to streptomycin (100%), trimethoprim/sulfamethoxazole (95%), tetracycline (94%), nalidixic acid (65%), and ampicillin (41%) was observed among S. sonnei isolates. Fourteen profiles of antimicrobial resistance were identified with the most common resistance profile being nalidixic acid, streptomycin, tetracycline, and trimethoprim/sulfamethoxazole (35%). PCR and DNA sequencing analysis revealed the presence of class 2 integron in all isolates, and class 1 and 2 integrons in 7 isolates. The class 2 integron carried two types of gene cassettes. One cassette array was dfrI, sat2, and aadA1 (91%), and the other was dfr1 and sat1 (8%). dfrA12 and aadA2 gene cassette was found in one isolate containing class 1 integron. PFGE was carried out to examine the genetic relatedness among isolates. All isolates except for one showed similar PFGE patterns (similarity of 80.1%). These results suggest that the S. sonnei isolated during 1999–2008 in Seoul have similar lineages that have not undergone evolutionary changes with time.     

克雷伯氏菌属(Klebsiella)细菌比较基因组学分析揭示多复制子抗性质粒介导广泛的抗性基因传播

[目的] 研究克雷伯氏菌与多复制子抗性质粒间的关系,分析细菌携带多复制子质粒对抗生素环境的响应机制。[方法] 以2018-2020年分离的56株不同来源克雷伯氏菌（Klebsiella sp.）分离株为研究对象,利用微量肉汤稀释法评估其多重耐药表型,对分离菌株进行全基因组测序（WGS）,通过细菌全基因组关联分析（BGWAS）技术和比较基因组学方法深入解析多复制子抗性质粒形成的机制。[结果] 耐药表型分析发现野生动物来源的菌株具有更广的耐药谱系,总体Klebsiella sp.对氨苄西林表现出很高的耐药率（80.36%）,尤其是马来穿山甲来源菌株对头孢类抗生素高度耐受,同时对氯霉素、左氧氟沙星和复方新诺明等药物耐受,基因组分析发现这些菌株携带了抗性质粒和更多的抗生素抗性基因。进一步对69个质粒序列分析,发现有28个质粒为多复制子质粒,主要携带bla_CTX-M-15、bla_CTX-M-14、bla_CTX-M-55、bla_OXA-1和bla_TEM-1等β-内酰胺酶基因。细菌携带质粒类型分析认为Klebsiella pneumoniae可能是多复制子质粒的重要宿主,质粒骨架与结构分析发现多复制子质粒多由2个或2个以上单个质粒融合而成,携带此类质粒的菌株不仅获得了更广的耐药表型,而且在全球传播扩散分布逐年增加,因此产生对抗生素环境更强的适应性。[结论] 多重耐药性细菌呈现的表型与携带的多复制子质粒有关,相比较下多复制子质粒比非多复制子质粒有更强的抗性基因携带能力,或许是细菌在强大的抗生素压力下产生的重要响应机制。本研究对于未来探索细菌抗性基因的传播扩散机制具有重要意义。     

苯唑西林敏感、mecA基因阳性的猪源金黄色葡萄球菌的流行、分子分型及耐药性研究

[目的] 为了解我国猪源苯唑西林敏感-mecA阳性金黄色葡萄球菌（Oxacillin-susceptible,mecA-positive Staphylococcus aureus,OS-MRSA）的流行情况、菌株分子特征及耐药性,本研究对我国中西部4个省份（甘肃、陕西、河南和广西）的9个规模化养猪场进行鼻腔拭子样本采集。[方法] 运用PCR扩增nuc和mecA基因及苯唑西林耐药性检测对OS-MRSA菌株进行分离鉴定。然后对分离所得的OS-MRSA菌株进行26种毒素编码基因、16种抗生素耐药性以及spa、MLST和SCCmec分型检测。[结果] 结果表明,采集的884份样本中,67份样本7.6%（67/884）分离到金黄色葡萄球菌,包括50株甲氧西林敏感菌株（Methicillin-sensitive Staphylococcus aureus,MSSA）、8株苯唑西林耐受-mecA阳性金黄色葡萄球菌（Oxacillin-resistant mecA-positive,OR-MRSA）和9株OS-MRSA菌株。26种被检毒素编码基因中有9种毒素编码基因被检出,其中hla基因检出率最高,其次为hld、hlb、hlg、sei、sem、seg、sen和seo。此外,67株分离株中仅有16株携带肠毒素编码基因,其中OR-MRSA和OS-MRSA菌株分别占37.5%（6/16）和50.0%（8/16）,且携带毒素编码基因的菌株克隆型均为ST9-t899。16种所测试抗生素中,菌株对12种抗生素表现为耐药,其中MSSA、OR-MRSA和OS-MRSA分离株分别主要对1-8、10-12和7-11种抗生素耐药。所有分离株共有4种克隆型ST398-t571、ST9-t899、ST398-t034和t11241,其中ST9-t899为MRSA菌株唯一克隆型和ST398-t571为MSSA优势克隆型。除4株分离株未检测到SCCmec分型外,IV_b（76.5%,13/17）是MRSA分离株的唯一分型。[结论] 结果表明,我国猪源MRSA分离株对苯唑西林药物敏感性发生了改变,出现了较多的苯唑西林敏感菌株。此外,MSSA和MRSA分离株优势克隆型分别为ST398-t571和ST9-IVb-t899。研究还发现,克隆型与毒素编码基因有显著相关性,携带毒素编码基因的菌株克隆型均为ST9-t899。通过了解我国猪源MSSA、OR-MRSA和OS-MRSA的流行、分子特征和耐药性,可以为我国猪源金黄色葡萄球菌的防控提供数据支持。     

Stopped-Flow Measurement of Reaction Rate of Dihydroxyfumaric Acid with 2, 6-Dichlorophenolindophenol

The proline auxotrophic strain of Acetobacter aceti No. 1023 treated with CaCl₂ solution was transformed to the Pro⁺ phenotype at a frequency of up to 10²/μg DNA using chromosomal DNA prepared from the wild type prototrophic strain. The CaCl₂-treated cells of A. aceti No. 1023 could also be rendered competent for uptake of plasmid DNA. In an attempt to produce an appropriate cloning vector for A. aceti, the restriction patterns of the cryptic plasmids, pTA5001 A (23.5 Kb) and pTA5001B (23 Kb), found in A. aceti No. 1023 were determined. A selectable marker (ampicillin resistance) was introduced onto these cryptic plasmids by fusing them to vector pACYC177 from E. coli, using their single restriction site for XhoI. The hybrid plasmids generated could replicate in and confer ampicillin resistance to both A. aceti and E. coli. The maximum transformation frequency for A. aceti No. 1023 with these vectors was 10³/μg DNA.     

Antimicrobial resistance patterns among different Escherichia coli isolates in the Kingdom of Saudi Arabia

Antimicrobial resistance patterns among different Escherichia coli isolates in the Kingdom of Saudi Arabia. This study aimed to investigate the patterns of antimicrobial resistance in E. coli isolated from different samples, and to identify potential pathogenic isolates in Riyadh, Kingdom of Saudi Arabia (KSA). In total, 51 bacterial isolates were recovered from 113 samples of human urine, food (raw meat, raw chicken, raw egg surface, and fresh vegetables), water, and air. Twenty-four E. coli isolates were tested for susceptibility to 26 antibiotics. The air sample isolates were most resistant to amoxicillin, ampicillin, amoxicillin/clavulanic acid, amoxicillin/sulbactam, piperacillin/tazobactam, cefalotin, cefuroxime, cefoxitin, cefixime, nitrofurantoin, and trimethoprim/sulfamethoxazol. The isolates from vegetable samples were resistant to amoxicillin, ampicillin, amoxicillin/clavulanic acid, amoxicillin/sulbactam, cefalotin, cefuroxime, cefoxitin, and cefixime. By contrast, the isolates from the water samples were resistant only to amoxicillin and ampicillin. The isolates from the human urine samples were most frequently resistant to norfloxacin (80%) followed by amoxicillin and ampicillin (70%), trimethoprim/sulfamethoxazole (55%), ciprofloxacin and ofloxacin (50%), cefalotin (30%), cefuroxime, cefixime and cefotaxime (25%), ceftazidime, ceftriaxone, cefepime and aztreonam (20%), amoxicillin/clavulanic acid, piperacillin/tazobactam and gentamicin (10%), and amoxicillin/sulbactam and cefoxitin (5%). Almost all (23/25, 95.8%) (n = 23) of the isolates were multi-drug resistant (MDR) (i.e., resistant to 3 or more classes of antibiotics), and 16.7% (n = 4) of those were positive for extended spectrum β-lactamase (ESBL). Of the 4 ESBL-producers, 3 were positive for blaCTX_-M-15 and blaCTX_-M1_group, 2 were positive for blaCMY_-2, and 1 each was positive for blaCTX_{-M-2 group,} blaSHV, and blaOXA_-47. The quinolone resistance gene qnrS was detected in 25% (n = 6) of the E. coli strains isolated from urine (N = 5) and air (N = 1) samples. The considerable number of antimicrobial resistance genes detected among E. coli isolates tested here is alarming and should raise public health concern.     

Inhibition of Monilinia oxycocci by bacteria isolated from a cranberry marsh

Bacteria inhibitory to Moniliniaoxycocci, the cranberry cotton ball pathogen, were identified. Eighty-three bacteria isolated from a cranberry marsh and Erwinia herbicola C9-1,which is being developed elsewhere for the biological control of fire blight of pome fruits, were tested fortheir ability to inhibit radial growth and conidial germination of M. oxycocci in vitro. IsolateBA35 from cranberry (tentatively identified as Pseudomonas syringae pv. morsprunorum) and E. herbicola C9-1 completely inhibited radial growth of M. oxycocci. BA35 and C9-1 were among the most effective of 21 bacteria tested for inhibition of conidial germination. Growth of bacteria in sclerotial extracts of M. oxycocci and Sclerotinia sclerotiorum was determined in order to select isolates that might be successful in degradingsclerotia, thereby reducing the viability of M.oxycocci. Populations of isolates 62 and S-18(identities unknown), and S-19 (tentatively identified as Micrococcus luteus), increased approximately3.0--5.0 log₁₀ units in all extracts within 24 h. Populations of isolate S-10 increased by about 3.5log₁₀ units in all sclerotial extracts within 48 h. Populations of isolate S-49 (identity unknown)were lower in extracts of M. oxycocci than S. sclerotiorum after 48-h. In buffer controls, bacterial populations remained stable or decreased over the 48-h period. This revised version was published online in July 2006 with corrections to the Cover Date.     

Multiple Antimicrobial Resistance of Gram-Negative Bacteria from Natural Oligotrophic Lakes Under Distinct Anthropogenic Influence in a Tropical Region

The aim of this study was to evaluate the resistance to ten antimicrobial agents and the presence of bla _TEM1 gene of Gram-negative bacteria isolated from three natural oligotrophic lakes with varying degrees of anthropogenic influence. A total of 272 indigenous bacteria were recovered on eosin methylene blue medium; they were characterized for antimicrobial resistance and identified taxonomically by homology search and phylogenetic comparisons. Based on 16S ribosomal RNA sequences analysis, 97% of the isolates were found to be Gram-negative bacteria; they belonged to 11 different genera. Members of the genera Acinetobacter, Enterobacter, and Pseudomonas predominated. Most of the bacteria were resistant to at least one antimicrobial. The incidence of resistance to β-lactams, chloramphenicol, and mercury was high, whereas resistance to tetracycline, aminoglycosides, and nalidixic acid was low. There was a great frequency of multiple resistances among the isolates from the three lakes, although no significant differences were found among the disturbed and reference lakes. The ampicillin resistance mechanism of 71% of the isolates was due to the gene bla _TEM1 . Our study suggests that multiresistant Gram-negative bacteria and the bla _TEM1 gene are common in freshwater oligotrophic lakes, which are subject to different levels of anthropogenic inputs.     

Microbial Responses to Environmentally Toxic Cadmium

Abstract We analyzed the soil microbial communities from one uncontaminated and two metal-impacted soils and found that while cadmium adversely affected the numbers of culturable bacteria in all soils, cadmium-resistant isolates were found from each of the soils. With exposure to 24 and 48 μg ml^-1 soluble cadmium, the metal-contaminated soil communities were more resistant than the uncontaminated soil community. In addition, in one metal-stressed soil, the resistant population became more resistant with increased cadmium levels. Ribosomal 16S DNA sequencing identified the isolates as Arthrobacter, Bacillus, or Pseudomonas spp. Further characterization demonstrated that two of the isolates were highly resistant to soluble cadmium with maximum resistance at 275 μg ml^-1 cadmium. These isolates were also resistant to a variety of antibiotics, namely ampicillin, gentamicin, penicillin, and streptomycin, but no overall correlation was found between enhanced antibiotic resistance and cadmium resistance. One Pseudomonas isolate H1 did become more resistant with increasing cadmium levels, suggesting a different resistance mechanism at high cadmium concentrations. Received: 29 April 1999; Accepted: 7 July 1999; Online Publication: 30 November 1999     

Antimicrobial susceptibilities and resistance genes in Campylobacter strains isolated from poultry and pigs in Australia

Aims

To evaluate the phenotypic and genotypic profiles of Campylobacter spp. from poultry faecal samples from free range or intensively raised meat chickens and free range egg layers. In addition, a case‐comparison study of antibiotic resistance genes from different groups of poultry and some pig strains previously collected was carried out.

Methods

Resistance to different antibiotics was assessed using the agar dilution method. In addition, all the strains were tested for ampicillin (bla_OXA‐61), erythromycin (aph‐3‐1), tetracycline tet(O), streptomycin (aadE), and the energy‐dependent multi‐drug efflux pump (cmeB) resistance genes using multiplex polymerase chain reaction.

Results

The evaluation of phenotypic resistance revealed all of the strains from poultry were sensitive to ciprofloxacin, gentamicin, erythromycin or tylosin. But, widespread resistance to lincomycin (51–100%), extensive resistance to ampicillin (33·3–60·2%) and less resistance to tetracycline (5·6–40·7%) were observed in the different groups of chickens. Antibiotic resistance genes bla_OXA‐61, cmeB and tet(O) were found in 82·6–92·7%, 80·3–89% and 22·3–30·9% Camp. coli isolates from pigs, whilst 59–65·4% and 19·2–40·7% Camp. jejuni from chickens were found to encode bla_OXA‐61 and tet(O), respectively.

Conclusion

No significant difference between isolates from free range egg layers and meat chickens (P < 0·05) was found. However, there were significant differences between the pig strains and all the groups of poultry strains (P < 0·05) with regard to carriage of resistance genes. In addition, pulsed field gel electrophoresis of selected resistant isolates from the poultry and pig revealed closely related clonal groups.

Significance and Impact of the study

Our results suggest the resistant strains are persisting environmental isolates that have been acquired by the different livestock species. Furthermore, the different treatment practices in poultry and pigs have resulted in differences in resistance profiles in Campylobacter isolates.     

野生鸟类分离的多重耐药肺炎克雷伯氏菌(Klebsiella pneumoniae)耐药基因分子进化特征研究

【目的】调查野生鸟类携带菌的耐药状况,探索其在细菌耐药性传播过程中的作用。【方法】从野生鸟类石鸡、绯胸鹦鹉、太阳锥尾鹦鹉和黑领椋鸟的新鲜粪便分离4株Klebsiella pneumoniae,采用微量肉汤稀释法评估其多重耐药表型,并利用全基因组测序技术和细菌全因组关联分析、比较基因组学方法对分离株进行分子溯源,系统解析其携带的多重耐药质粒或基因与其宿主、同源质粒间的关联。【结果】4株肺炎克雷伯菌的耐药谱各不相同,来自石鸡样本的分离株S90-2对9种药物耐受,绯胸鹦鹉样本分离株S141对3种药物耐受,太阳锥尾鹦鹉分离株M911-1仅耐受氨苄西林,黑领椋鸟的样本分离株S130-1对所使用的14种药物完全敏感。S90-2属于ST629型,携带bla_CTX-M-14、fosA6、aac(3)-Iid和bla_SHV-11为主的30个耐药基因和携带1个耐药性质粒pS90-2.3 (IncR型)。S141属于ST1662型,携带fosA5、bla_SHV-217等27个耐药基因,1个质粒pS141.1 [IncFIB(K)(pCAV1099-114)/repB型]仅携带耐药基因adeF。M911-1为新ST类型,携带bla_SHV-1、fosA6等共计27个耐药基因,其质粒pM911-1.1携带了3个耐药基因。S130-1属于ST3753型,携带bla_SHV-11、fosA6等27个耐药基因,pS130-1 [IncFIB(K)型]则仅携带一个耐药基因tet(A)。质粒比对表明,质粒pS90-2.3携带的耐药基因片段源自不同的肠杆菌科菌株染色体或质粒。pS90-2.3的同源质粒主要来自人类宿主菌,且主要在中国分布,这些质粒主要细菌宿主为K. pneumoniae和Escherichia coli,且ST11型K. pneumoniae分离株为重要宿主菌。【结论】本研究中来自野生鸟类的多重耐药K. pneumoniae,其耐药基因主要来自质粒,质粒耐药基因主要由转座子、插入序列、整合子和前噬菌体等可移动元件介导,这些多重耐药质粒与人类的宿主菌密切相关。