Microbiology of the oil fly, Helaeomyia petrolei

Helaeomyia petrolei larvae isolated from the asphalt seeps of Rancho La Brea in Los Angeles, Calif., were examined for microbial gut contents. Standard counts on Luria-Bertani, MacConkey, and blood agar plates indicated ca. 2 x 10(5) heterotrophic bacteria per larva. The culturable bacteria represented 15 to 20% of the total population as determined by acridine orange staining. The gut itself contained large amounts of the oil, had no observable ceca, and maintained a slightly acidic pH of 6.3 to 6.5. Despite the ingestion of large amounts of potentially toxic asphalt by the larvae, their guts sustained the growth of 100 to 1,000 times more bacteria than did free oil. All of the bacteria isolated were nonsporeformers and gram negative. Fourteen isolates were chosen based on representative colony morphologies and were identified by using the Enterotube II and API 20E systems and fatty acid analysis. Of the 14 isolates, 9 were identified as Providencia rettgeri and 3 were likely Acinetobacter isolates. No evidence was found that the isolates grew on or derived nutrients from the asphalt itself or that they played an essential role in insect development. Regardless, any bacteria found in the oil fly larval gut are likely to exhibit pronounced solvent tolerance and may be a future source of industrially useful, solvent-tolerant enzymes.     

Microbiology of the Oil Fly, Helaeomyia petrolei

Helaeomyia petrolei larvae isolated from the asphalt seeps of Rancho La Brea in Los Angeles, Calif., were examined for microbial gut contents. Standard counts on Luria-Bertani, MacConkey, and blood agar plates indicated ca. 2 × 10⁵ heterotrophic bacteria per larva. The culturable bacteria represented 15 to 20% of the total population as determined by acridine orange staining. The gut itself contained large amounts of the oil, had no observable ceca, and maintained a slightly acidic pH of 6.3 to 6.5. Despite the ingestion of large amounts of potentially toxic asphalt by the larvae, their guts sustained the growth of 100 to 1,000 times more bacteria than did free oil. All of the bacteria isolated were nonsporeformers and gram negative. Fourteen isolates were chosen based on representative colony morphologies and were identified by using the Enterotube II and API 20E systems and fatty acid analysis. Of the 14 isolates, 9 were identified as Providencia rettgeri and 3 were likely Acinetobacter isolates. No evidence was found that the isolates grew on or derived nutrients from the asphalt itself or that they played an essential role in insect development. Regardless, any bacteria found in the oil fly larval gut are likely to exhibit pronounced solvent tolerance and may be a future source of industrially useful, solvent-tolerant enzymes.     

Monitoring of antibiotic resistance in bacteria isolated from laboratory animals

The drug resistance of microorganisms isolated from laboratory animals never treated with antibiotics is being reported consistently, while the number of laboratory animals used in medicine, pharmacy, veterinary medicine, agriculture, nutrition, and environmental and health science has increased rapidly in Korea. Therefore, this study examined the development of antimicrobial resistance in bacteria isolated from laboratory animals bred in Korea. A total of 443 isolates (7 species) containing 5 Sphingomonas paucimobilis, 206 Escherichia coli, 60 Staphylococcus aureus, 15 Staphylococcus epidermidis, 77 Enterococcus faecalis, 27 Citrobacter freundii, 35 Acinetobacter baumannii were collected from the nose, intestine, bronchus and reproductive organs of ICR mice and SD rats. Of these species, Acinetobacter baumannii and Enterococcus faecalis showed significant antimicrobial resistance according to the minimum inhibition concentration (MIC) in E-test. In case of Acinetobacter baumannii, several isolates showed MIC values 16-128 μg/mL for cefazolin and cefoxitin, and higher resistance (128-512 μg/mL) to nitrofurantoin than that of standard type. Resistance to cefazolin, cefoxitin and nitrofurantoin was detected in 17.14, 20.00, and 8.57% of the Acinetobacter baumannii isolates, respectively. In addition, 44.1% of the Enterococcus faecalis isolates collected from the laboratory animals were resistant to oxacillin concentration of 16-32 μg/mL range, while MIC value of standard type was below oxacillin concentration of 6 μg/mL. These results suggest that in rodent species of laboratory animals, Acinetobacter baumannii are resistance to cefazolin, cefoxitin and nitrofurantoin, whereas those of Enterococcus faecalis were resistance to oxacillin.     

Frequency and antibiotic resistance of bacteria isolated from urine cultures]

The AA report the data pertinent to the urine culture performed during a year in the Sanitary and Prophylactic Laboratory of the district of L'Aquila. In urine samples with number of bacteria > 10(5)/ml have been found E. coli (49%), Proteus mirabilis (32%), Pseudomonas aeruginosa (12%), Staphylococcus aureus (5%), Proteus rettgeri (1%), Enterococco (1%). The data are also reported concerning germ resistance to several antibiotics.     

Factors affecting the measurement of antibiotic resistance in bacteria isolated from lake water

It is more difficult to obtain a reliable assessment of antibiotic resistance in populations of aquatic bacteria than in those populations which are well characterized (e.g. bacteria of medical and veterinary significance). Factors which influence the results include the bacterial taxa involved, their site of origin and the methods and media used to isolate and subculture the bacteria, and to perform the sensitivity tests. Examples of these effects are provided. The resistance profiles obtained with populations of aquatic pseudomonads depend on the species composition of the population. Resistance patterns in aquatic bacteria varied with the site from which they were isolated; a higher incidence of resistance was recorded along shorelines and in sheltered bays than in the open water. The inclusion of antibiotics in the media employed for primary isolation increased the number of individual and multiple resistances recorded. A similar effect was observed with increased inoculum size in the sensitivity disc method but this could be reversed by raising the incubation temperature. The medium used to conduct the test also affected the results and many aquatic bacteria failed to grow on media such as Iso-Sensitest Agar. It is recommended that the sensitivity disc method is adopted for aquatic bacteria because it permits interpretation of a wider range of response. Comparison of the incidence of antibiotic resistance in different habitats will remain meaningless, however, until comprehensive methods for the identification of bacteria are developed and the techniques used for sensitivity testing are standardized.     

Factors affecting the measurement of antibiotic resistance in bacteria isolated from lake water

It is more difficult to obtain a reliable assessment of antibiotic resistance in populations of aquatic bacteria than in those populations which are well characterized (e.g. bacteria of medical and veterinary significance). Factors which influence the results include the bacterial taxa involved, their site of origin and the methods and media used to isolate and subculture the bacteria, and to perform the sensitivity tests. Examples of these effects are provided. The resistance profiles obtained with populations of aquatic pseudomonads depend on the species composition of the population. Resistance patterns in aquatic bacteria varied with the site from which they were isolated; a higher incidence of resistance was recorded along shorelines and in sheltered bays than in the open water. The inclusion of antibiotics in the media employed for primary isolation increased the number of individual and multiple resistances recorded. A similar effect was observed with increased inoculum size in the sensitivity disc method but this could be reversed by raising the incubation temperature. The medium used to conduct the test also affected the results and many aquatic bacteria failed to grow on media such as Iso-Sensitest Agar. It is recommended that the sensitivity disc method is adopted for aquatic bacteria because it permits interpretation of a wider range of response. Comparison of the incidence of antibiotic resistance in different habitats will remain meaningless, however, until comprehensive methods for the identification of bacteria are developed and the techniques used for sensitivity testing are standardized.     

Tolerance of pesticides and antibiotic resistance in bacteria isolated from wastewater-irrigated soil

A total of 64 bacterial isolates (40 Pseudomonas spp., 12 Azotobacter and 12 Rhizobium spp.) were characterized on the basis of morphological, cultural and biochemical characteristics. All the isolates were tested for their tolerance to the pesticides endosulfan, carbofuran, and malathion. 12.5% of the Pseudomonas isolates from soil tolerated concentrations of 1600 g malathion ml whereas 7.5% of isolates tolerated the same concentration of carbofuran. However, Pseudomonas isolates demonstrated a tolerance limit to endosulfan at a concentration of 800 g/ml. Asymbiotic N₂-fixers (Azotobacter) and symbiotic N₂-fixers (Rhizobium spp.) were also able to tolerate concentrations of pesticides up to 1600 g/ml. All the isolates were further tested for their antibiotic susceptibility against seven different antibiotics, nalidixic acid, cloxacillin, chloramphenicol, tetracycline, amoxycillin, methicillin, doxycycline. 100% of the Pseudomonas isolates were resistant to cloxacillin and 57.5% were resistant to methicillin. 7.5% of the isolates exhibited multiple resistance to five different antibiotics in three different combinations whereas 25% of the isolates showed multiple resistance to four different antibiotics in seven different combinations. Some of the resistant isolates were also screened for plasmid DNA and found to harbour a single plasmid.     

Disinfectant tolerance and antibiotic resistance in psychrotrophic Gram-negative bacteria isolated from vegetables

A total of 330 strains of psychrotrophic non-fermenting Gram-negative bacteria isolated from vegetables were studied. In spite of the wide range of antibiotic resistance occurring, less than 10% showed resistance patterns which included mezclocillin-ticarcillin-gentamicin or ceftizoxime-norfloxacin. Reductions of > 5 log₁₀ in the numbers of cfu were found when these strains were exposed for 30 min to a quaternary ammonium compound (1% w/v).     

社区获得性泌尿系感染病原菌分布及耐药性分析

目的分析社区获得性泌尿系感染病原菌的种类及对常用抗生素的耐药性。方法收集2008年5月至2013年3月分离自社区获得性泌尿系感染患者中段尿的菌株,分析病原菌种类并测试主要病原菌对常用抗生素的体外敏感性。结果在215株细菌中,以革兰阴性杆菌155株（72. 1% ）为主。分离前5位的细菌为大肠埃希菌（48.4% ）、肠球菌属（10. 7% ）、肺炎克雷伯菌（7.4% ）、链球菌属（6. 0% ）、假丝酵母属（6. 0% ）。大肠埃希菌和肺炎克雷伯菌中,共63株产ESBL,占52. 5%。产ESBL菌株对头孢替坦、哌拉西林/他唑巴坦、阿米卡星、呋喃妥因、亚胺培南等5种抗生素的耐药率低于10%,对其他抗生素耐药率则超过70%。不产ESBL的菌株除对氨苄西林、氨苄西林/舒巴坦、环丙沙星、左氧氟沙星和复方新诺明的耐药率超过30%外,对其他常用抗生素的耐药率均在10%以下。肠球菌属和链球菌属分别对呋喃妥因和青霉素的耐药率较低（3/23和0/23）,未发现对万古霉素耐药株。结论引起社区获得性泌尿系感染的病原菌以大肠埃希菌为代表的革兰阴性杆菌为主,但由于不同菌株对抗生素的敏感性差异较大,用药之前进行尿培养是避免因抗生素使用不合理造成感染慢性化的一项重要措施。     

Association of metal tolerance with multiple antibiotic resistance of bacteria isolated from drinking water

Bacterial isolates from the drinking water system of an Oregon coastal community were examined to assess the association of metal tolerance with multiple antibiotic resistance. Positive correlations between tolerance to high levels of Cu2+, Pb2+, and Zn2+ and multiple antibiotic resistance were noted among bacteria from distribution waters but not among bacteria from raw waters. Tolerances to higher levels of Al3+ and Sn2+ were demonstrated more often by raw water isolates which were not typically multiple antibiotic resistant. A similar incidence of tolerance to Cd2+ was demonstrated by isolates of both water types and was not associated with multiple antibiotic resistance. These results suggest that simultaneous selection phenomena occurred in distribution water for bacteria which exhibited unique patterns of tolerance to Cu2+, Pb2+, and Zn2+ and antibiotic resistance.     

外科血培养标本中病原菌分布及耐药性分析

目的了解中山大学附属第一医院外科血标本中病原菌的菌种分布及常见菌株的耐药性。方法血标本用Bact/A lert-120全自动血培养仪进行血培养,阳性血培养转种后用VITEK-60 AMS细菌鉴定仪鉴定,用K-B法进行药敏试验。结果2002年1月至2005年12月血培养标本中共分离出病原菌256株,阳性率为10.6%。122株(47.7%)为革兰阴性杆菌,其中肠杆菌科细菌占72.1%(88/122),非发酵菌占27.9%(34/122);113株(44.1%)为革兰阳性球菌,其中葡萄球菌属占51.3%(58/113),肠球菌占38.1%(43/113);真菌21株(8.2%)。血培养中的革兰阴性杆菌对亚胺培南、美洛培南治疗敏感;革兰阳性球菌对万古霉素和替考拉宁敏感。结论肠杆菌科细菌和葡萄球菌是外科血培养中的主要病原菌,其耐药现象严重,宜根据药敏结果选用敏感抗菌药物治疗。     

Association of metal tolerance with multiple antibiotic resistance of bacteria isolated from drinking water.

Bacterial isolates from the drinking water system of an Oregon coastal community were examined to assess the association of metal tolerance with multiple antibiotic resistance. Positive correlations between tolerance to high levels of Cu2+, Pb2+, and Zn2+ and multiple antibiotic resistance were noted among bacteria from distribution waters but not among bacteria from raw waters. Tolerances to higher levels of Al3+ and Sn2+ were demonstrated more often by raw water isolates which were not typically multiple antibiotic resistant. A similar incidence of tolerance to Cd2+ was demonstrated by isolates of both water types and was not associated with multiple antibiotic resistance. These results suggest that simultaneous selection phenomena occurred in distribution water for bacteria which exhibited unique patterns of tolerance to Cu2+, Pb2+, and Zn2+ and antibiotic resistance.     

Natural antimicrobial peptides from bacteria: characteristics and potential applications to fight against antibiotic resistance

Because of the emergence of antibiotic‐resistant pathogens worldwide, a number of infectious diseases have become difficult to treat. This threatening situation is worsened by the fact that very limited progress has been made in developing new and potent antibiotics in recent years. However, a group of antimicrobials, the so‐called bacteriocins, have been much studied lately because they hold a great potential in controlling antibiotic‐resistant pathogens. Bacteriocins are small antimicrobial peptides (AMPs) produced by numerous bacteria. They often act toward species related to the producer with a very high potency (at pico‐ to nanomolar concentration) and specificity. The common mechanisms of killing by bacteriocins are destruction of target cells by pore formation and/or inhibition of cell wall synthesis. Several studies have revealed that bacteriocins display great potential in the medical sector as bacteriocinogenic probiotics and in the clinic as therapeutic agents. In this review, we discuss the emerging antibiotic resistance and strategies to control its dissemination, before we highlight the potential of AMPs from bacteria as a new genre of antimicrobial agents.     

Combating antibiotic resistance in bacteria

Combinations of certain antibiotics select against resistant strains of bacteria. This finding may provide a strategy of combating antibiotic resistant bacteria.     

Acquired antibiotic resistance in lactic acid bacteria from food

Acquired antibiotic resistance, i.e. resistance genes located on conjugative or mobilizable plasmids and transposons can be found in species living in habitats (e.g. human and animal intestines) which are regularly challenged with antibiotics. Most data are available for enterococci and enteric lactobacilli. Raw material from animals (milk and meat) which are inadvertantly contaminated with fecal matters during production will carry antibiotic resistant lactic acid bacteria into the final fermented products such as raw milk cheeses and raw sausages. The discovered conjugative genetic elements of LAB isolated from animals and food are very similar to elements studied previously in pathogenic streptococci and enterococci, e.g. -type replicating plasmids of the pAM1, pIP501-family, and transposons of the Tn916-type. Observed resistance genes include known genes like tetM, ermAM, cat, sat and vanA. A composite 29'871 bp resistance plasmid detected in Lactococcus lacti s subsp. lactis isolated from a raw milk soft cheese contains tetS previously described in Listeria monocytogenes, cat and str from Staphylococcus aureus. Three out of five IS elements on the plasmid are almost or completely identical to IS1216 present in the vanA resistance transposon Tn1546. These data support the view that in antibiotic challenged habitats lactic acid bacteria like other bacteria participate in the communication systems which transfer resistance traits over species and genus borders. The prevalence of such bacteria with acquired resistances like enterococci is high in animals (and humans) which are regularly treated with antibiotics. The transfer of antibiotic resistant bacteria from animals into fermented and other food can be avoided if the raw substrate milk or meat is pasteurized or heat treated. Antibiotic resistance traits as selectable markers in genetic modification of lactic acid bacteria for different purposes are presently being replaced, e.g. by metabo lic traits to generate food-grade vectors.     

Diversity of tet resistance genes in tetracycline-resistant bacteria isolated from a swine lagoon with low antibiotic impact

Tetracycline resistance has been extensively studied and shown to be widespread. A number of previous studies have clearly demonstrated that a variety of tetracycline resistance genes are present in swine fecal material, treatment lagoons, and the environments surrounding concentrated animal feeding operations (CAFOs). The diversity of tetracycline resistance within a swine lagoon located at a CAFO that used only bacitricin methylene disalicylate as an antibiotic was evaluated by screening 85 tetracycline-resistant isolates for the presence of 18 different genes by performing PCR with primers that target tetracycline efflux genes of Gram-negative bacteria and ribosomal protection proteins. In addition, partial 16S rRNA sequences from each of these isolates were sequenced to determine the identity of these isolates. Of the 85 isolates examined, 17 may represent potential novel species based on BLAST results. Greater than 50% of the isolates (48 out of 85) were found to not contain targeted tet efflux genes. Though minimum inhibitory concentrations ranged widely (16 - >256 mg/L), these values did not give an indication of the tet genes present. Ten new genera were identified that contain at least one tet efflux gene. Five other genera possessed tet efflux genes that were not found in these organisms previously. Interestingly, none of the isolates possessed any of the selected ribosomal protection protein genes. Though tetracycline resistance was found in bacteria isolated from a swine CAFO lagoon, it appears that the limited antibiotic use at this CAFO might have impacted the presence and diversity of tetracycline resistance genes.     

广州地区儿童血培养病原菌的分布及耐药性研究

目的探讨儿童血培养病原菌的分布特点及其耐药情况,为临床诊疗提供参考。方法对广州市儿童医院2005年至2006年临床各科室送检血液标本所分离病原菌的分布及药敏结果进行回顾性分析。结果共检出385株病原菌,其中革兰阳性菌208株,占54．0％,革兰阴性菌164株,占42．6％,真菌13株,占3．4％。分离率前6位的病原菌依次为凝固酶阴性葡萄球菌（CNS,35．8％）、肺炎克雷伯菌（8．8％）、不动杆菌（5．5％）、大肠埃希菌（4．9％）、铜绿假单胞菌（4、7％）、金黄色葡萄球菌（4．4％）。病原菌的病区分布特点：儿科重症监护病房以不动杆菌等非发酵菌为主要分离菌（占41．7％）,新生儿重症监护病房以CNS为主（40．5％）,血液病区以肠杆菌科细菌为主（35．7％）,新生儿病房及传染病房均以CNS为主要分离菌。CNS对青霉素、氨苄西林、红霉素耐药率均超过80％,但对万古霉素、替考拉宁和阿米卡星敏感,MRCNS检出率达72.5％。肠杆菌科细菌对哌拉西林、氨苄西林、头孢噻肟及头孢哌酮的耐药率为50％～100％,但对亚胺培南、阿米卡星和诺氟沙星耐药率较低。不动杆菌对广谱青霉素、第3代头孢菌素、氨曲南及庆大霉素的耐药率较高而对亚胺培南、头孢哌酮／舒巴坦较为敏感。结论凝固酶阴性葡萄球菌是广州地区儿童败血症最主要的病原菌。不同病区检出病原菌种类有较大差异。根据病原菌种类及药敏结果合理应用抗菌药是有效控制感染和减少耐药菌株产生的重要手段。     

Physiological aspects of hydrocarbon emulsification, metal resistance and DNA profile of biodegrading bacteria isolated from oil polluted sites

The production of biosurfactants was evaluated for seven bacterial strains isolated from different oil contaminated sites by the Emulsification Index using diesel oil as the hydrocarbon source. Minimum Inhibitory Concentrations of Mg²⁺, Cr³⁺ and Cu²⁺ were determined to identify the less sensitive bacteria in order to select the best strains for bioremediation. Plasmid extraction was also performed in order to search for gene sequences involved with biosurfactant synthesis. All strains were able to emulsify diesel oil. Rhodococcus ruber AC239 presented the best index (58%), followed by other Rhodococcus strains. Pseudomonas aeruginosa, R. ruber AC239, AC87 and R. erytropolis AC272 presented smallest sensitivities to heavy metals used, being suitable for use in sites contaminated with high concentrations of them. No plasmid DNA was detected showing that biosurfactant coding genes should be in the chromosomal DNA.