Antibiotic synergy against biofilm-forming <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis>

Eight antibiotics (aztreonam, ceftazidim, cefoperazon, cefepim, netilmicin, amikacin, ofloxacin and ciprofloxacin) exhibited antimicrobial activity individually and/or in combinations against 20 wild-type biofilm-forming strains of Pseudomonas aeruginosa. The strains were less susceptible in biofilm; in 10 strains antibiotic synergy was observed for the combination of aztreonam and ciprofloxacin. Synergy was also demonstrated in the case of β-lactams and aminoglycosides, β-lactams and fluoroquinolones, aminoglycosides and fluoroquinolones, and for monobactams and β-lactams although the strains were resistant to the individual antibiotics. Synergism or partial synergism was found with one or more antibiotic combinations against 32.4% of isolates.     

铜绿假单胞菌氨基糖苷16SrRNA甲基化酶基因分析

目的调查215株湖州地区临床分离铜绿假单胞菌对氨基糖苷类抗生素的耐药性和16S rRNA甲基化酶基因分布情况。方法收集2011年1月至2012年12月湖州地区临床分离铜绿假单胞菌215株,琼脂稀释法测定5种氨基糖苷类抗菌药物（庆大霉素、阿米卡星、妥布霉素、伊帕米星、奈替米星）的MIC值;PCR检测armA、rmtA、rmtB、rmtC、rmtD和npmA六种氨基糖苷类16S rRN甲基化酶基因,序列分析明确基因型。测定产16S rRNA甲基化酶菌株对常见抗菌的敏感性,并检测碳青霉烯耐药株产碳青霉烯酶情况。结果铜绿假单胞菌对异帕米星敏感率最高为81.4%,对5种氨基糖苷类抗生素全部耐药的22株菌株中,17株检出armA基因;未发现其他16S rRNA甲基化酶基因阳性菌株。17株armA阳性菌株对碳青霉烯类抗生素耐药5株（耐药率为29.4%）,对头孢他啶、头孢吡肟、哌拉西林/他唑巴坦、环丙沙星耐药率均超过40%。5株碳青霉烯耐药菌株中检测到2株产VIM-2型金属碳青霉烯酶。结论铜绿假单胞菌对氨基糖苷类抗生素耐药率高,检测到16S rRNA甲基化酶基因armA。产16S rRNA甲基化酶铜绿假单胞菌耐药性强,部分菌株同时产金属碳青霉烯酶,给临床抗感染治疗及院内感染控制带来挑战。     

In vitro antibiotic susceptibilities of Yersinia enterocolitica biotype 1A

Antibiotic susceptibilities of 80 strains of Yersinia enterocolitica biotype 1A isolated from human, swine and various aquatic sources to 20 β-lactam and 26 non-β-lactam antibiotics were studied. Most isolates were resistant to penicillins, first-generation cephalosporins, macrolides and lincosamides, while sensitive to aminoglycosides and quinolones. In comparison to earlier studies, the majority of the strains were either intermediately sensitive or resistant to piperacillin. Relatively decreased susceptibility or resistance to third-generation cephalosporins was also observed in several Y. enterocolitica isolates. This revised version was published online in August 2006 with corrections to the Cover Date.     

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.     

Comparison of disc diffusion and epsilometer (E-test) testing techniques to determine antimicrobial susceptibiliy of Campylobacter isolates of food and human clinical origin

The antibiotic resistance profiles of 75 Campylobacter isolates of food and human clinical origin was determined by two agar diffusion susceptibility methods; disc diffusion and epsilometer-test (E-test). The most common therapeutic antimicrobials, erythromycin, ciprofloxacin and tetracycline were studied, along with chloramphenicol, ampicillin and naladixic acid. The resistance observed for each antimicrobial, as determined by both of methods, were statistically compared using Fisher two-tailed analysis.Of the six antimicrobials studied only two were shown to have statistically different patterns when resistance was compared by disc diffusion and E-test. The percentage of isolates resistant to clinically relevant antimicrobials using both techniques ranged from 6.6 to 21.3% for erythromycin, 25.3–26.6% for tetracycline and 33.3–36.0% for ciprofloxacin. The prevalence of multi-drug resistant (MDR) campylobacters (isolates resistant to 2 or more antimicrobials) for both disc diffusion and E-test was 44%. It can be concluded that, for four of the six antimicrobials assessed, antimicrobial resistance prevalences could be equally determined by either of the methods studied.     

Effect of antifungals on itraconazole resistant <Emphasis Type="Italic">Candida glabrata</Emphasis>

In the last decade, infections caused by Candida glabrata have become more serious, particularly due to its decreased susceptibility to azole derivatives and its ability to form biofilm. Here we studied the resistance profile of 42 C. glabrata clinical isolates to different azoles, amphotericin B and echinocandins. This work was also focused on the ability to form biofilm which plays a role in the development of antifungal resistance. The minimal inhibitory concentration testing to antifungal agents was performed according to the CLSI (Clinical and Laboratory Standards Institute) M27-A3 protocol. Quantification of biofilm was done by XTT reduction assay. All C. glabrata clinical isolates were resistant to itraconazole and sixteen also showed resistance to fluconazole. All isolates remained susceptible to voriconazole. Amphotericin B was efficient in a concentration range of 0.125–1 mg/L. The most effective antifungal agents were micafungin and caspofungin with the MIC₁₀₀ values of ≤0.0313–0.125 mg/L. Low concentrations of these agents reduced biofilm formation as well. Our results show that resistance of different C. glabrata strains is azole specific and therefore a single azole resistance cannot be assumed to indicate general azole resistance. Echinocandins proved to have very high efficacy against clinical C. glabrata strains including those with ability to form biofilm.     

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.     

Prevalence and antimicrobial resistance of Campylobacter in US dairy cattle

AIMS: To obtain an overview of the prevalence and antimicrobial resistance of Campylobacter in faeces of US dairy cows in 2002. METHODS AND RESULTS: Faeces from 1435 cows, representing 96 dairy operations in 21 US states, were collected for the culture of Campylobacter. A total of 735 Campylobacter strains were isolated (51.2% positive samples) with 94 operations positive (97.9%) for Campylobacter. From this collection, 532 isolates (473 Campylobacter jejuni and 59 Campylobacter coli) were randomly selected for susceptibility testing to eight antimicrobials: azithromycin, chloramphenicol, ciprofloxacin, clindamycin, erythromycin, gentamicin, nalidixic acid and tetracycline. The C. jejuni isolates exhibited resistance to tetracycline (47.4%), nalidixic acid (4.0%) and ciprofloxacin (2.5%), while the C. coli strains exhibited some resistance to all antimicrobials except chloramphenicol and ciprofloxacin. Only 3.6% of the C. jejuni isolates were resistant to two or more antimicrobials but 20.3% of the C. coli strains were multiresistant. CONCLUSIONS: On most operations, at least one cow was positive for Campylobacter and more than half of the cows sampled were shedding Campylobacter. The C. coli isolates had significantly higher levels of resistance to macrolides and to tetracycline compared with the C. jejuni strains, but were susceptible to ciprofloxacin. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated a high prevalence of Campylobacter on US dairy operations; however, US dairy cattle have not been recognized as a major source of human infection compared with poultry. Campylobacter coli appears to develop antimicrobial resistance more readily than C. jejuni from the same environment.     

Phenotypic and genotypic analysis of bacteria isolated from three municipal wastewater treatment plants on tetracycline‐amended and ciprofloxacin‐amended growth media

Aims: The goal of this study was to determine the antimicrobial susceptibility of bacteria isolated from three municipal wastewater treatment plants. Methods and Results: Numerous bacterial strains were isolated from three municipal wastewater treatment facilities on tetracycline‐ (n = 164) and ciprofloxacin‐amended (n = 65) growth media. These bacteria were then characterized with respect to their resistance to as many as 10 different antimicrobials, the presence of 14 common genes that encode resistance to tetracycline, the presence of integrons and/or the ability to transfer resistance via conjugation. All of the characterized strains exhibited some degree of multiple antimicrobial resistance, with nearly 50% demonstrating resistance to every antimicrobial that was tested. Genes encoding resistance to tetracycline were commonly detected among these strains, although intriguingly the frequency of detection was slightly higher for the bacteria isolated on ciprofloxacin‐amended growth media (62%) compared to the bacteria isolated on tetracycline‐amended growth media (53%). Class 1 integrons were also detected in 100% of the queried tetracycline‐resistant bacteria and almost half of the ciprofloxacin‐resistant strains. Conjugation experiments demonstrated that at least one of the tetracycline‐resistant bacteria was capable of lateral gene transfer. Conclusions: Our results demonstrate that multiple antimicrobial resistance is a common trait among tetracycline‐resistant and ciprofloxacin‐resistant bacteria in municipal wastewater. Significance and Impact of the Study: These organisms are potentially important in the proliferation of antimicrobial resistance because they appear to have acquired multiple genetic determinants that confer resistance and because they have the potential to laterally transfer these genetic determinants to strains of clinical importance.     

Oxacillinases and antimicrobial susceptibility of Ralstonia pickettii from pharmaceutical water systems in Croatia

This study evaluated antibiotic susceptibility and presence of bla_OXA22 and bla_OXA60 genes in 81 isolates of Ralstonia pickettii obtained from different purified and ultra-pure water systems in two different geographical areas of Croatia. E-test and disc diffusion test were performed to determine antibiotic susceptibility. Polymerase chain reaction was applied to detect genes encoding OXA-22 and OXA-60 oxacillinases previously identified in R. pickettii. The isolates were genotyped by pulsed-field gel electrophoresis. The results revealed variable susceptibility/resistance profiles. Our isolates exhibited high susceptibility rates to ceftriaxone, cefotaxime, piperacillin-tazobactam, ciprofloxacin, imipenem, cefepime and in lesser extent to ceftazidime. High rates of susceptibility were also observed for sulphamethoxazole-trimethoprim and piperacillin. High resistance rates were noticed for ticarcillin-clavulanate, aztreonam and meropenem, as well as for all aminoglycosides tested. Modified Hodge test was positive in 51·9% strains, indicating production of carbapenemases. bla_OXA22 and bla_OXA60 genes were detected in 37·0 and 80·3% strains, respectively. Pulsed-field gel electrophoresis identified three major clusters containing subclusters. R. pickettii should be taken seriously as a possible cause of nosocomial infections to ensure adequate therapy, to prevent the development of resistant strains and to try to reduce the possibility of R. pickettii surviving in clean and ultra clean water systems.     

Antimicrobial susceptibility and molecular characterization of <Emphasis Type="Italic">Vibrio cholerae</Emphasis> from cholera outbreaks in Chennai

The genotype and antibiotic resistance pattern of the toxigenic Vibrio cholerae strains associated with cholera outbreaks vary frequently. Fifty-one V. cholerae strains isolated from cholera outbreaks in Chennai (2002–2005) were screened for the presence of virulence and regulatory genes by multiplex polymerase chain reaction (PCR) assay. Genotyping of the isolates was done by VC1 primers derived from enterobacterial repetitive intergenic consensus (ERIC)-related sequence in V. cholerae. All the isolates possessed toxigenic genes, such as ctxA, ctxB, tcpA, ace, ompU, toxR and zot. Two different El Tor genotypes and one O139 genotype could be delineated by VC1-PCR. One of the El Tor genotypes was similar to the El Tor strains isolated from Bhind district and Delhi during 2004. Antibiotic susceptibility testing revealed greater variability among the isolates tested. All the isolates were found to be susceptible to norfloxacin, ciprofloxacin and tetracycline. Thiry-three per cent of the isolates were found to be resistant to more than 4 antibiotics and could be termed as multiple antibiotic resistant. Coexistence of O139 serogroup along with the El Tor biotype could be identified among the strains recovered during the period 2002–2004. The O139 isolates were found to be more susceptible to the antibiotics tested when compared to the El Tor isolates.     

Antibiotic resistance and molecular characterization of poultry isolates of Salmonella by RAPD-PCR

The antibiotic resistance profile of 17 poultry isolates of Salmonella was studied against 24 different antibiotics. 69–88% of the Salmonella isolates displayed a high level of resistance, particularly against penicillin, rifampicin, erythromycin, clarithromycin, clindamycin, sulphamethoxazole and vancomycin. In contrast, a relatively low or moderate level of resistance was observed against furazolidone, spectinomycin, ciprofloxacin, chloramphenicol, cefepime, carbenicillin, nalidixic acid, streptomycin, oxacillin and cephalothin (11–59%). Moreover, resistance to multiple antibiotics (2–5) was also observed among the Salmonella strains, and none of the isolates was found susceptible to all the antibiotics used. Similarity coefficient among Salmonella strains by RAPD-PCR analysis varied from 0.60 to 0.86, and all the salmonellae could be classified into seven groups on the basis of dendrogram analysis. Generally, a very high level of concordance between RAPD-PCR profile and antibiotic profile was not observed, which indicates that genes for antibiotic resistance may not always be present on genomic DNA rather may be plasmid-borne.     

Determination of the Efflux Pump-Mediated Resistance Prevalence in Pseudomonas aeruginosa, Using an Efflux Pump Inhibitor

In Gram negative bacteria, fluoroquinolone resistance is acquired by target mutations in topoisomerase genes or by reducing the permeation of drugs due to the increase in expression of endogenous multidrug efflux pumps that expel structurally unrelated antimicrobial agents. An ongoing challenge is searching for new inhibitory substances in order to block efflux pumps and restore the antibiotic drugs susceptibility. In this research, we sought to investigate the interplay between ciprofloxacin and an efflux pump inhibitor (EPI), phenyl alanine arginyl β-naphtylamide (PAβN), to determine the prevalence of efflux pump overexpression in clinical isolates of Pseudomonas aeruginosa. Ciprofloxacin was tested at different concentrations (256–0.25 μg/ml) with a fixed concentration of PAβN (50 μg/ml). The isolates susceptibility profiles were analyzed by disc diffusion and agar dilution methods using 10 antibiotic discs and 4 powders. It was found that in the presence of PAβN, resistance to ciprofloxacin was inhibited obviously and MIC values were decreased. The comparison between subgroups of P. aeruginosa isolates with different resistance profiles indicates that efflux pump overexpression (EPO) is present in 35% of ciprofloxacin resistant isolates with no cross resistance and in variable frequencies among isolates showing cross resistance to other tested antibiotics: gentamicin (31%), ceftazidime (29%), and imipenem (18%). Altogether, these results imply that PAβN maybe effective to restore the fluoroquinolone drugs susceptibility in clinical treatment procedures. Results also show that increased use of a fluoroquinolone drug such as ciprofloxacin can affect the susceptibility of P. aeruginosa to other different antipseudomonal agents.     

Functional properties of <Emphasis Type="Italic">Lactobacillus</Emphasis> strains isolated from dairy products

Twenty-four acid- and bile-tolerant lactobacilli isolates from dairy products were identified and further in vitro characterized for the presence of functional traits potentially useful for probiotic applications, which included desirable and undesirable traits, such as biofilm formation, ability to inhibit intestinal pathogens, antibiotic susceptibility, and enzyme activity. The majority of examined strains were susceptible to certain antimicrobial agents (streptomycin, gentamicin, clindamycin, erythromycin, tetracycline, quinupristin–dalfopristin), except for three strains of Lactobacillus rhamnosus with minimal inhibitory concentration levels for streptomycin higher than the microbiological breakpoints (≥32 μg/mL), which are considered as resistant. Undesirable traits such as α-chymotrypsin or N-acetyl-β-glucosaminidase activities were not detected, but low β-glucuronidase, and moderate and high β-glucosidase activities were recorded in nine strains, which were eliminated from further examination together with three isolates showing unsuitable antibiotic resistance. Of the remaining 12 isolates, 4 (Lactobacillus fermentum 202, Lactobacillus gallinarum 7001, L. rhamnosus 183, and Lactobacillus plantarum L2-1) manifested an outstanding potential to inhibit selected intestinal pathogens in an agar spot test, including Escherichia coli and Salmonella spp., and simultaneously demonstrated strong biofilm-forming capacity. In conclusion, the results of our in vitro experiments showed that the above four strains had a potential probiotic value and met the criteria to be identified as a possible probiotic microorganism, with the necessity of verification through well-designed in vivo experimental, clinical, and technological studies before the strains can be used as probiotics or as starter probiotic cultures.     

High level of quinolone resistance in <Emphasis Type="Italic">Escherichia coli</Emphasis> from healthy chicken broilers

The development of resistance to quinolones (nalidixic acid, ciprofloxacin and enrofloxacin) in 2006–2008 was evaluated in 317 strains of Escherichia coli isolated from healthy chicken broilers from various farms. The isolates (2006/2007/2008) showed a high resistance to nalidixic acid (87/85/67 %), ciprofloxacin (CIP) (49/54/29 %) and enrofloxacin (ENR) (52/42/22 %). Nalidixic acid-resistant isolates with low level of MIC for CIP and ENR represented a single mutation; intermediary MIC for CIP and ENR were related to two mutations and high level resistance MIC for CIP (≥4 mg/L) and ENR (≥16 mg/L) represented three mutations (two in gyrA and one in parC). There was a correlation between the phenotype reading of high-level resistance and mutations in gyrA (Ser83Leu, Asp87Tyr or Asp87Asn) and parC (Ser80Ile) gene. Plasmid-mediated quinolone-resistance qnrS gene was detected in one Escherichia coli strain with a high level of ciprofloxacin resistance. Our results demonstrate the increase in occurrence of multiresistant E. coli strains with a high level of chromosomal and plasmid resistance to fluoroquinolones.     

仙居县儿童下呼吸道感染肺炎克雷伯菌耐药性分析

目的分析仙居人民医院住院下呼吸道感染患儿临床分离肺炎克雷伯菌的耐药特征,为临床合理用药提供依据。方法选择2012年7月至2013年7月该院下呼吸道感染肺炎克雷伯菌阳性患儿81例。对患儿的临床一般资料进行分析,对临床分离菌株进行细菌鉴定,用18种抗生素进行药敏试验,采用WHONET5．4分析软件进行统计。结果2012年7月至2013年7月共分离出81株肺炎克雷伯菌,ESBLs阳性42株,检出率为51．85％。所有菌株对亚胺培南、厄他培南、左旋氧氟沙星、丁胺卡那100％敏感。对氨苄西林耐药率为100％。ESBLs阴性菌株对氨曲南、头孢曲松、头孢他啶、头孢唑啉、头孢吡肟100％敏感,而ESBLs阳性菌株则100％耐药。ESBLs阴性菌株对其他抗生素的耐药率为氨苄西彬舒巴坦（12．82％）、环丙沙星（2．56％）、头孢替坦（O％）、呋喃妥因（20．51％）、庆大霉素（5．13％）、复方新诺明（17．85％）、妥布霉素（2．56％）、哌拉西林／他唑巴坦（2．56％）;ESBLs阳性菌株对其他抗生素的耐药率为氨苄西林／舒巴坦（73．80％）、环丙沙星（2．38％）、头孢替坦（16．67％）、呋喃妥因（61．90％）、庆大霉素（28．57％）、复方新诺明（54．76％）、妥布霉素（7．14％）、哌拉西林／他唑巴坦（7．14％）。结论本地区患儿中肺炎克雷伯菌耐药性较高,临床应重视病原菌的检测。     

Association of MexAB-OprM with intrinsic resistance ofPseudomonas aeruginosa to aminoglycosides

MexAB-OprM is known to pump out mostly lipophilic and amphiphilic drugs. But in low-ionic-strength medium, nutrient broth (NB), this pump has been shown to contribute to hydrophilic antibiotic (aminoglycosides) resistance, via active efflux. The association of the MexAB-OprM efflux system to aminoglycosides resistance inPseudomonas aeruginosa were assessed using a drug susceptibility test carried out in NB, in presence and absence of protonophore, carbonyl cyanide m-chlorophenyl hydrazone (CCCP) by 23 multidrug resistant strains were selected from 104 clinical isolates ofP. aeruginosa. Active efflux was assessed using EtBr accumulation assays. PCR was used to identify themexAB-oprM and MexAB-OprM-dependent efflux of aminoglycosides and the results were confirmed by continuous fluorescence assay. A multidrug resistant mutant ofmexAB-oprM, derivative of PAO1, was selected by ciprofloxacin and subjected to the same analysis as described above for the clinical isolates. In this study, CCCP reduced the level of MICs in at least 1 dilution. Ethidium bromide accumulation assays confirmed the presence of efflux mechanism in all clinical isolates and PCR demonstrated that 17% of our isolates had themexAB-oprM operon. Results of aminoglycosides accumulation showed, in addition to amphiphilic antibiotics in NB medium, MexAB-OprM extrudes aminoglycosides (hydrophilic) drugs.     

Clonal spread of antimicrobial-resistant <Emphasis Type="Italic">Escherichia coli</Emphasis> isolates among pups in two kennels

Although the dog breeding industry is common in many countries, the presence of antimicrobial resistant bacteria among pups in kennels has been infrequently investigated. This study was conducted to better understand the epidemiology of antimicrobial-resistant Escherichia coli isolates from kennel pups not treated with antimicrobials. We investigated susceptibilities to 11 antimicrobials, and prevalence of extended-spectrum β-lactamase (ESBL) in 86 faecal E. coli isolates from 43 pups in two kennels. Genetic relatedness among all isolates was assessed using pulsed-field gel electrophoresis (PFGE). Susceptibility tests revealed that 76% of the isolates were resistant to one or more of tested antimicrobials, with resistance to dihydrostreptomycin most frequently encountered (66.3%) followed by ampicillin (60.5%), trimethoprim-sulfamethoxazole (41.9%), oxytetracycline (26.7%), and chloramphenicol (26.7%). Multidrug resistance, defined as resistance against two or more classes of antimicrobials, was observed in 52 (60.5%) isolates. Three pups in one kennel harboured SHV-12 ESBL-producing isolates. A comparison between the two kennels showed that frequencies of resistance against seven antimicrobials and the variation in resistant phenotypes differed significantly. Analysis by PFGE revealed that clone sharing rates among pups of the same litters were not significantly different in both kennels (64.0% vs. 88.9%), whereas the rates among pups from different litters were significantly different between the two kennels (72.0% vs. 33.3%, P < 0.05). The pups in the two kennels had antimicrobial-resistant E. coli clones, including multidrug-resistant and ESBL-producing clones. It is likely that resistant and susceptible bacteria can clonally spread among the same and/or different litters thus affecting the resistance prevalence.     

Relation between resistance to β-lactam antibiotics and cadmium in salmonellae isolated from pigs

Of 50Salmonella species isolated from pigs, 30 were resistant to cadmium and 18 of these also to azlocillin. The azlocillin-resistant isolates were resistant to cadmium at 80–500, mg/L CdSO₄. A broader spectrum of resistance to azlocillin, ampicillin and cephazollin was found in strains resistant to <200 mg/L CdSO₄. Resistance to silver, mercury, chloramphenicol and streptomycin was independent of the resistance to β-lactam antibiotics and Cd²⁺. Production and levels of β-lactamase do not correlate with the spectrum of resistance.     

嗜麦芽寡养单胞菌临床分布特征与耐药分析

目的了解湖州市中心医院嗜麦芽寡养单胞菌临床分布特征与耐药性。方法采用常规方法分离,用VITE-COMPACT2全自动微生物分析仪进行菌种鉴定,用K—B法进行药敏试验。结果分离到嗜麦芽寡养单胞菌810株,复方新诺明耐药菌株48株（分离率5．9％）。标本来源主要来自ICU室,其次呼吸科,大部分来自痰液标本（约占89．2％）,年龄段以中老年人比率最高。嗜麦芽寡养单胞菌对亚胺培南、美罗培南、头孢吡肟、哌拉西彬他坐巴坦、庆大霉素、妥布霉素、阿米卡星高度耐药;头孢他啶、替卡西林／克拉维酸、环丙沙星耐药率为33．7％～58．2％;头孢哌酮／舒巴坦、左氧氟沙星、米诺环素、复方新诺明耐药率低于30．0％。复方新诺明耐药菌株对头孢哌酮／舒巴坦、左氧氟沙星和米诺环素耐药率分别为60．4％、91．7％和2．0％,对其余抗菌药物耐药率达100．0％。复方新诺明耐药菌株与复方新诺明敏感菌株相比,耐药情况更严重,其中对三、四代头孢菌素、喹诺酮类耐药率显著高于复方新诺明敏感菌株（P〈0．01）;对碳青霉烯类、青霉素类、氨基糖苷类抗菌药物耐药率与复方新诺明敏感菌株相比,差异无统计学意义（P〉0．05）。结论嗜麦芽寡养单胞菌呈高度耐药,对头孢哌酮／舒巴坦、左氧氟沙星、米诺环素、复方新诺明尚敏感,但对复方新诺明耐药的嗜麦芽寡养单胞菌耐药现象更严重。应重视嗜麦芽寡养单胞菌引起的院内感染,尽量减少不必要的侵人性操作,加强抗菌药物的合理规范使用。