Occurrence of chromium resistant thermotolerant coliforms in tannery effluent

Twenty six thermotolerant strains resistant to high levels of chromium (50-250 microg/ml) were isolated from treated tannery effluent. They were also found resistant to multiple heavy metals and antibiotics. Majority of them were resistant to copper and bacitracin. Nine strains representing different resistance patterns were selected for plasmid profile and conjugation studies. Agarose gel electrophoresis results revealed that 6 strains harboured a single plasmid, whereas 3 strains exhibited 2 plasmid bands. Among antimicrobials, co-trimazole and bacitracin and among metals, Cu2+, Cd2+, Zn2+ and Ni2+ resistance were transferred most frequently at variable rates. However, chromium resistance was transferred in 6 strains with a frequency ranging 19-49x10(-2). Resistance to Co2+ and Hg2+ did not transfer under environmental conditions. Among the nine strains, three were found predominantly uropathogenic Escherichia coli (UPEC) serotype 04, whereas two strains were untypable. In addition, 4 transconjugants also showed a positive result after serotyping.     

Cadmium resistant Enterobacter cloacae and Klebsiella sp. isolated from industrial effluents and their possible role in cadmium detoxification

Three bacterial strains, two of Klebsiella sp. and one Enterobacter cloacae were isolated from industrial effluents of chemical and textile industries. They showed high efficiency in removing cadmium (Cd²⁺) from the medium. When 100 g/ml of Cd was added to the medium, the three isolates namely CMBL-Cd1, CMBL-Cd2 and CMBL-Cd3 removed or accumulated 86%, 87% and 85% of Cd, respectively, from the medium within 24h. Plasmids were detected in all the three strains. Plasmids of E. cloacae (pCBL1) and Klebsiella sp. (pCBL2 and pCBL3), estimated to be 6.6kb, were used to transform Escherichia coli C600. The transformed E. coli cells showed elevated resistance to Cd. Ethidium bromide curing indicated the presence of the Cd resistance gene on the plasmid. Resistance of the isolated strains against other metals like chromium (cr⁶⁺) and lead (pb²⁺) and a number of antibiotics was also checked. Cured strains showed lowered resistance against Cr and some antibiotics. This again supported the indication of the presence of Cd, Cr and some antibiotics resistance genes on plasmids.     

Antibiotic resistance among coliforms and Pseudomonas spp. from bodies of water around Port Harcourt, Nigeria

Samples from municipal waste water, the Bonny River estuary and wells in and around Port Harcourt were examined for bacteriological quality over a 9 month period. A total of 157 Pseudomonas spp., 133 Escherichia coli and 282 other coliforms were isolated and tested for the incidence of resistance to 10 antibiotics. All of the Pseudomonas spp. were resistant to at least one of the antibiotics while 96.2% were resistant to two or more. Most (83.5%) of the E. coli and other coliforms (91.8%) were resistant to at least one antibiotic. All strains were susceptible to gentamicin. Minimal inhibitory concentrations of ampicillin and tetracycline for E. coli ranged from 6.25 to 50 and 6.25 to 12.5 micrograms/ml, respectively. Minimal inhibitory concentrations of ampicillin and tetracycline were 1000 and 25 micrograms/ml for the Pseudomonas strains. The high incidence of bacterial resistance to antibiotics is discussed in relation to the widespread use of antibiotics, and possible public health implications.     

Characterization of large plasmids encoding resistance to toxic heavy metals in Salmonella abortus equi

Salmonella abortus equi vaccine strains were found to be resistant to high levels of toxic heavy metals--arsenic, chromium, cadmium, and mercury. The two strains 157 and 158 were resistant to ampicillin also. Curing of these strains resulted in loss of one or more resistance marker indicating plasmid borne resistance. Plasmid profile of strain 157 showed presence of three plasmids of 85, 54, and 0.1 Kb, whereas 158 strain showed presence of 85 Kb and 2 Kb plasmids. Plasmids were isolated from strain 157 and introduced into E. coli DH5alpha with a transformation efficiency of 2 x 10(3) transformants/microg DNA. Interestingly the transformants were resistant to antibiotics, heavy metals (As, Cr, Cd, Hg) and was also able to utilize citrate, a trait specific to Salmonella species. We report and establish for the first time the transferable large plasmids encoding resistance to various heavy metals, antibiotics and biochemical nature of S. abortus equi.     

Antibiotic resistance among coliforms and Pseudomonas spp. from bodies of water around Port Harcourt, Nigeria

Samples from municipal waste water, the Bonny River estuary and wells in and around Port Harcourt were examined for bacteriological quality over a 9 month period. A total of 157 Pseudomonas spp., 133 Escherichia coli and 282 other coliforms were isolated and tested for the incidence of resistance to 10 antibiotics. All of the Pseudomonas spp. were resistant to at least one of the antibiotics while 96.2% were resistant to two or more. Most (83.5%) of the E. coli and other coliforms (91.8%) were resistant to at least one antibiotic. All strains were susceptible to gentamicin. Minimal inhibitory concentrations of ampicillin and tetracycline for E. coli ranged from 6.25 to 50 and 6.25 to 12.5 μg/ml, respectively. Minimal inhibitory concentrations of ampicillin and tetracycline were 1000 and 25 μg/ml for the Pseudomonas strains. The high incidence of bacterial resistance to antibiotics is discussed in relation to the widespread use of antibiotics, and possible public health implications.     

Sensitivity of the causative agent of tularemia to antibiotics

Sensitivity of the tularemia causative agent of different geographical races to antibiotics such as streptomycin, tetracycline, gentamicin, rifampicin (20 strains), ampicillin, polymyxin M, erythromycin, oleandomycin (361 strains) and lincomycin (294 strains) was studied. High sensitivity of the tularemi a microbe to streptomycin, tetracycline, rifampicin (MIC of 10 gamma/ml), gentamicin (MIC of 1 gamma/ml) and resistance to 50 gamma of ampicillin and 1000 gamma/ml of polymyxin M were found. Combined use of 50 gamma of ampicillin and 100 gamma/ml of polymyxin M added to the nutrient medium for growth inhibition of the foreign flora on isolation of the tularemia causative agent from the infected material including stable laboratory animal carcases was recommended. Marked differences in sensitivity of the strains of different geographical races to the macrolides and lincomycin were observed. The strains of the non-Arctic and Central Asiatic races were of low resistance to the above drugs (the MIC of erythromycin, oleandomycin and lincomycin were 10--50, 50--400 and 25--100 gamma/ml respectively. Within the holarctic race 40 per cent were low resistant and 60 per cent were highly resistant to these drugs. The above drugs should not be used for treatment of tularemia cases.     

Isolation and characteristics of polymyxin-resistant mutants of Shigella flexneri

Some characteristics of S. flexneri 2a mutants resistant to various concentrations of polymyxin M were studied. The data indicate that mutations resulting in low (50 microgram/ml) and high (300 microgram/ml) levels of the antibiotic resistance were determined by different genes. Polymyxin resistance led to changed permeability of the outer membrane with respect to detergents and some antibiotics, such as aminoglycosides, penicillins, chloramphenicol and amphotericin B but did not change sensitivity of the strains to some bacteriophages, except phage PI. Mutants resistant to 50 microgram/ml of polymyxin M preserved their ability to induce keratoconjunctivitis in guinea pigs. Part of the strains resistant to 300 microgram/ml of the antibiotic lost this property. No correlation between the polymyxin M resistance level, loss of the pathogenic properties and toxicity of the bacterial cells was found. It was confirmed that though inactivation of endotoxin by polymyxins is associated with their capacity for interaction with lipid A, this component does not participate in development of resistance to these antibiotics.     

The role of thiamine inYersinia kristensenii resistance to antibiotics and heavy metals

The resistance to divalent metal ions, antibiotics and H₂O₂ was investigated inYersinia kristensenii strains 13, 15, 18 by performing subcultivations with CdSO₄ (20 and 100mg/L) in nutrient agar (NA) and M9 medium with thiamine. Metal resistance of all three strains in NA was the same and decreased in the following sequence: Ni>Zn=Co>Cd. The chloramphenicol (Cmp) resistance ranged between 32 and 256 mg/L and the H₂O₂ sensitivity was very low or even zero. In the presence of thiamine the metal resistance sequence changed to Zn=Cd>Ni, Co, Ni and Co tolerance being 10–20 mg/L. Cmp resistance of all strains increased to 256 mg/L and H₂O₂ sensitivity also rose. In Cd-treated cultures, the ratio of glucose to thiamine in culture medium affected Cd resistance. At normal content of glucose and thiamine (5 g/L and 5mg/L), Cd resistance markedly decreased coincident with thiamine exhaustion in these slowly-growing cultures. The Cmp resistance decreased to 16 mg/L, Ni and Co intolerance and H₂O₂ hypersensitivity appeared. At lowered glucose or thiamine levels (5 g/L and 2.5 mg/L or 2.5 g/L and 5 mg/L) a marginal decrease of Cd resistance took place in response to limited glucose uptake. Low thiamine or low-glucose cultures were resistant to H₂O₂, and exhibited a small decrease in Cmp resistance and a low Ni, Co tolerance. The adaptation of strain 15 to Cd induced only a small decrease of Cd resistance. Lowered glucose-to-thiamine ratio in culture medium probably induced in Cd-treated cultures a response triggering Cd resistance.     

Antibiotic Susceptibility of Helicobacter pylori Clinical Isolates: Comparative Evaluation of Disk-Diffusion and E-Test Methods

Antimicrobial susceptibility of 25 Helicobacter pylori strains isolated from patients with acid peptic diseases were tested for in vitro sensitivity to commonly used antibiotics using disk-diffusion and E-test, methods. All strains tested were susceptible to tetracycline by E-test, with the minimum inhibitory concentration (MIC) values being <0.125 μg/ml for all strains except for 6 (<0.023 μg/ml). However 1 strain was resistant by disk-diffusion method. One strain was resistant to clarithromycin both by disk diffusion and E-test (MIC <48 μg/ml), and 1 strain was resistant only by disk diffusion. Only one strain was resistant to amoxicillin by disk diffusion and E-test (MIC >256 μg/ml). For ciprofloxacin, three strains were resistant by disk diffusion and two by E-test (MIC <32 μg/ml). Sixteen strains were resistant to metronidazole by disk diffusion and E-test (MIC ≥ 8 μg/ml), and 1 was resistant only by E-test (MIC <48 μg/ml). Overall, 64% of the strains were resistant to metronidazole. The MIC for metronidazole was also tested by agar-dilution method, and metronidazole resistant strains had an, MIC >8 μg/ml. The disk-diffusion method showed excellent correlation with E-test results; there was 100% agreement for amoxicillin a other antibiotics showed 90% to 95% accuracy. Disk diffusion is cheaper than E-test (approximately 2.6 cents vs. US$2.60), is easy to perform, and is a reliable method for testing H. pylori susceptibility to antimicrobial agents in the clinical microbiology laboratory.     

2010年广州地区淋球菌耐药监测结果分析

目的了解广州地区淋球菌对抗生素耐药性的变化及PPNG和TRNG的流行趋势。方法用琼脂稀释法测定头孢曲松、大观霉素、环丙沙星、阿奇霉素和四环素的最低抑菌浓度（MIC）;用纸片碘量法检测β-内酰胺酶。结果83株淋球菌检出PPNG24株（28．9％）、TRNG50株（60．2％）、环丙沙星耐药率高达98．8％,高度耐药株（MIC≥16mg／L）43株（51．8％）,而76株淋球菌中阿奇霉素耐药株11株（14．5％）,均未出现对头孢曲松、大观霉素耐药的菌株,抗菌活性强。结论合理规范使用抗生素及动态监测淋球菌耐药性变迁是临床减少淋球菌耐药菌株出现的有效办法。     

Changes in antibiotic sensitivity in strains of Staphylococcus aureus, 1952-78.

Two hundred strains of Staphylococcus aureus isolated from outpatients with infections of the skin and subcutaneous tissues were tested for sensitivity to penicillin, erythromycin, tetracycline, sodium fusidate, methicillin, clindamycin, chloramphenicol, and gentamicin. One hundred and sixty-three (81.5%) of the strains were resistant to penicillin and 16 (8%) resistant to tetracycline. Incidence of resistance to other antibiotics was low. No strain was resistant to chloramphenicol, gentamicin, or methicillin. When compared with results of earlier studies, there was an increase in the incidence of resistance to penicillin and tetracycline, but no appreciable increase in resistance to other antibiotics.     

Presence of genetic exchange in Crithidia oncopelti (Trypanosomatidae) studied with drug resistance markers

Strains resistant to 100 mkg/ml of cycloheximide (ChxR100) and to 2.5 mg/ml of chloramphenicol (CapR2.5) were used in studies for the presence of genetic interchange in C. oncopelti. Phenotypes of these strains were stable on the nonselective medium and specific. Strains ChxR100 and CapR2.5 were mixed in equal proportions, cultivated during 7 days and tested. Under consecutive effect of inhibitors the culture of strains mixture and clones isolated from it exhibited double resistance. Phenotypes of recombinant clones were stable on the nonselective medium during, at the minimum, 70 to 90 cell generations. At the same conditions control cultures of parental strains and clones did not exhibit resistance that excludes the possibility of origin of cells resistant to both antibiotics from Crithidia of one of the parental strains as a result of secondary mutation. Thus, the results obtained show convincingly the presence of genetic interchange between flagellates of ChxR100 and CapR2.5 strains.     

2016‒2017年辽宁省沙门菌耐药菌谱与分子分型

摘要：目的 分析2016?2017年辽宁省沙门菌分离株的耐药特性与脉冲场凝胶电泳（PFGE）分子分型特征,为沙门菌引起的食源性疾病暴发、防控及抗生素使用提供参考数据。方法 对分离的54株沙门菌进行血清分型和药物敏感试验。根据PulseNet沙门菌标准PFGE分型技术,选取全部菌株进行PFGE分子分型分析,应用BioNumerics软件对菌株条带进行分析,确定菌株间的特征及相关性。结果 54株沙门菌血清型居首位的是肠炎沙门菌,占46.30％;其次是鼠伤寒沙门菌,占24.07％;共分为10个血清型。对13种抗生素的耐药分析显示多重耐药菌株为36株,占66.7％,其中耐3～5种的13株（24.1%）,耐6～8种的13株（24.1%）,耐9～11种的10株（18.5%）。54株沙门菌经聚类分析获得36种带型,相似度区间为49.7%～100.0％。结论 辽宁省沙门菌分离株多重耐药状况比较严重,相同血清型其PFGE带型相似度相对较高,同时具有较显著的优势带型特点;而且发现同一PFGE型菌株的耐药谱相对比较接近。     

Effectiveness of the antibiotics chloramphenicol and rifampin in the treatment of Streptococcus pneumoniae-induced meningitis and systemic infections

Streptococcus pneumoniae, a common pathogen in pediatric infections, has become resistant to penicillin and make these infections difficult to treat. Rifampin and chloramphenicol have been recommended as alternative therapies, since they are less costly and more accessible to communities with limited resources. However, their use may be restricted by the differing levels of resistance found in target populations. The objective was to determine minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) for chloramphenicol and rifampin in strains of S. pneumoniae. These strains were newly isolated from children under age 5 that had demonstrated systemic infections and meningitis. A subgroup of 107 isolates of S. pneumoniae was selected from 324 strains isolated during a period of 2 years (1994-1996). Among these isolates, 60 were penicillin-resistant and 47 were susceptible; 53 isolates were from children with meningitis. MIC and MBC for chloramphenicol and rifampicin were obtained by standard methods recommended by the National Committee for Clinical Laboratory Standards (NCCLS). S. pneumoniae ATCC strain 49619 served as the control. An isolate was considered susceptible to chloramphenicol when MIC = 4 microg/ml and resistant when MIC = 8 microg/ml. A strain was considered susceptible to rifampin when MIC = 1 microg/ml and resistant when MIC = 4 microg/ml. MBC was determined by recording the lower concentration of the antibiotic that inhibited 99.9% of the initial inoculum. Chloramphenicol resistance was found in 21% of the 107 isolates. In the group susceptible to penicillin, 11% were resistant to chloramphenicol and in the group resistant to penicillin 28% was resistant to chloramphenicol as well. MBC was found > 4 microg/ml in 28% of the isolates susceptible to penicillin and in 60% of the resistant isolates. No isolates were found resistant to rifampin. However, 2 penicillin resistant isolates showed CBM > 1 microg/ml to rifampin, and one with CIM = 1 microg/ml had a MBC to rifampicin of 16 microg/ml. Meningitis isolates showed higher CIM and CBM than the group of total isolates. These data suggest that chloramphenicol is not recommended for invasive infections caused by S. pneumoniae in Colombia. Rifampin is a more effective therapy in combination with other antibiotics for treatment of this kind of infections. Further studies are necessary to clarify the significance of low levels of MBC to rifampin found in some strains, since this may affect the efficacy of therapies that include this antibiotic.     

Level and nature of the drug resistance of Shigella flexneri]

Characteristics of antibiotic resistance of 300 strains of Shigella flexner 2a isolated from patients within 1976--1977 in the regions where these bacteria were very rare for a long period of time were studied. It was shown that most of the isolates were resistant to chloramphenicol (88.1 per cent), tetracycline (94.8 per cent), streptomycin (89.1 per cent), polymyxin M (82.4 per cent) and others. 46.5--61.6 per cent of the isolates were resistant to neomycin antibiotics. A high level of the resistance was also noted: the bactericidal effect was registered in 52.0-74.0 per cent of the cultures at a dose of 500--1000 microgram/ml. 91.4 per cent of the strains possessed multiple dug resistance, 78.8 per cent of them being simultaneously resistant to 4--7 drugs. Transmissive R-plasmids were found in 68.8 per cent of the isolates. After exposure to acridine dyes the plasmid nature of the resistance was confirmed in 72.3 per cent of the cultures. Variability of the r-determinant sets in r-plasmids was noted. Strains (64.9 per cent) carrying r-determinants Tc, Cm, Sm and Tc, Cm were more frequent. Strains with one transmissive r-determinant were usually solitary.     

鲍曼不动杆菌耐药程度与其主动外排泵蛋白的相关性研究

目的:探讨鲍曼不动杆菌耐药程度与其主动外排泵蛋白的相关性。方法:首先用纸片扩散法检测64株临床鲍曼不动杆菌对8种抗菌药物的敏感性;将其分为A组(0～2种抗生素耐药)、B组(对3～5种抗生素耐药)和C组(对6～8种抗生素耐药);检测64株临床鲍曼不动杆菌对罗丹明6G的外排情况,筛选出罗丹明6G外排明显增加的菌株;并用逆转录-聚合酶链反应(RT-PCR)方法检测主动外排泵基因AdeABC的表达水平。结果:64株鲍曼不动杆菌中有4株对0～2种抗生素耐药(A组),对3～5种抗生素耐药的有33株(B组),对6～8种抗生素耐药的有27株(C组);多重耐药组鲍曼不动杆菌罗丹6G外排明显增高,外排程度A组相似文献   

Streptococcus group A resistance to tetracycline: its spread and transduction]

The study on antibiotics resistance of group A streptococci isolated in 1977 showed that the number of the antibiotic resistant strains had significantly increased as compared to the data of 1960. High percentage (53%) of the cultures with multiple resistance was noted. It was observed that the number of the streptococcal cultures resistant to erythromycin and chloramphenicol decreased while the number of the strains resistant to tetracyclines increased. The level of resistance to tetracycline increased more than 2 times from 1960 and in some cases reached 125 and 250 gamma/ml. The wide spread of tetracycline resistance was evident of the presence of the mechanism of the marker transduction. Possible transduction of this feature was studied. Microbe-free phagolysates obtained by induction with UV-light from the strains with multiple antibiotic resistance were used as the donor material in the experiment on transduction. Principal possibility of transducing resistance to tetracycline from 2 donors to 4 recipients at a frequency of 10(-6) was shown.     

双歧杆菌的耐药性与质粒

目的：研究双歧杆菌的耐药性与质粒的关系。方法 对１７株５种来自微生态制剂的双歧杆菌进行抗生素药敏试验和质粒检测,利用溴化乙锭消除其质粒;比较质粒消除前后耐药性的改变。结果１７株双歧杆菌对氨基糖式类和多肽类抗生素呈强抗性;除１株短型双歧杆菌Ｂ１５７存有２．７Ｋｂ和５．６Ｋｂ两种质粒外,其余菌株均未质粒,消除后持粒的Ｂ１５７株菌对抗生素的敏感性并未改变。结论 此１７株双歧杆菌的耐药性与质粒无直接相关性     

Fecal pollution in water from storm sewers and adjacent seashores in Natal, Rio Grande do Norte, Brazil.

A study on the distribution patterns of enteropathogenic bacteria polluting the shoreline in Natal, Rio Grande do Norte, Brazil, was carried out based on 72 samples obtained from three storm sewers and adjoining beach locations, Praia do Meio (PM), Areia Preta (AP) and Ponta Negra (PN). From each location, 12 water samples were taken and analyzed for fecal coliforms (FC) and Escherichia coli. In AP, two (16.7%) of the seawater samples and five (41.7%) of the storm sewer samples yielded values above 1.1 x 107 FC/100 ml, whereas only one (8.3%) of the samples from PM reached this level. There was no correlation (p > 0.05) between rainfall indices and FC values. A total of 64 E. coli isolates were obtained: 37 from the storm sewer samples and 27 from the seawater samples. Of these isolates, four (O143, two O112ac, and O124) were enteroinvasive and two (O111 and O125) were enteropathogenic. Resistance to antibiotics and to heavy metals was also analyzed. Almost 36% of the E. coli strains isolated were resistant to more than one antibiotic. All strains were resistant to zinc and copper at the highest concentration tested (250 microg/ml), and several (23.4%) were resistant to mercury at 50 microg/ml. Our results agreed with previous reports that antibiotic resistance is commonly associated with heavy-metal resistance in pathogens.     

Study of the activity of a new glycopeptide antibiotic eremomycin combined with tobramycin against Staphylococci in vitro

Eremomycin is an original natural antibiotic with glycopeptide structure isolated at the Institute of New Antibiotics, the USSR Academy of Medical Sciences. Activity of eremomycin alone or in combination with tobramycin was studied with using 25 clinical strains of staphylococci. 56 and 88 per cent of the strains were respectively resistant to gentamicin and kanamycin, two aminoglycoside antibiotics. All the staphylococcal strains were sensitive to eremomycin in concentrations of 0.12 to 1 microgram/ml. The MIC of tobramycin for 10 (40 per cent) sensitive strains ranged within 0.25-2 micrograms/ml. For 60 per cent of the strains the MIC was equal to or higher than 16 micrograms/ml. When eremomycin was used in combination with tobramycin the antibacterial effect with respect to 17 strains (68 per cent) increased. In 32 per cent of the strains the effect was synergistic and in 36 per cent of the strains it was additive. Indifference and antagonism were detected with respect to 7 (28 per cent) and 1 (4% per cent) strains respectively. No significant difference was shown in manifestation of the synergistic-additive nature of eremomycin and tobramycin interaction with respect to the tobramycin sensitive and resistant strains.