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PubMed1997

The effect of changes in the consumption of macrolide antibiotics on erythromycin resistance in group A streptococci in Finland. Finnish Study Group for Antimicrobial Resistance.

BACKGROUND: In the early 1990s there was an increase in erythromycin resistance among group A streptococci in Finland. In response, policies regarding outpatient antibiotic therapy were changed, and nationwide recommendations were issued that called for reductions in the use of macrolide antibiotics for respiratory and skin infections in outpatients. We studied the effect of this policy on the pattern of erythromycin resistance throughout Finland. METHODS: From 1991 through 1996, a total of 39,247 group A streptococcal isolates from throat swabs (82 percent of the isolates) and pus samples (18 percent) and 290 isolates from blood cultures were studied in regional microbiology laboratories. The susceptibility of the isolates to erythromycin was tested by the disk-diffusion or the screening-plate method. RESULTS: Consumption of macrolide antibiotics decreased from 2.40 defined daily doses per 1000 inhabitants per day in 1991 to 1.38 in 1992 (P=0.007) and remained near the lower level during the study period. The change in consumption was followed by a steady decrease in the frequency of erythromycin resistance among group A streptococcal isolates from throat swabs and pus samples, from 16.5 percent in 1992 to 8.6 percent in 1996 (odds ratio for 1996 as compared with 1992, 0.5; 95 percent confidence interval, 0.4 to 0.5). CONCLUSIONS: In Finland, after nationwide reductions in the use of macrolide antibiotics for outpatient therapy, there was a significant decline in the frequency of erythromycin resistance among group A streptococci isolated from throat swabs and pus samples.

Anti-Bacterial Agents↗
PubMed1994

Validation of NCCLS macrolide (azithromycin, clarithromycin, and erythromycin) interpretive criteria for Haemophilus influenzae tested with the Haemophilus test medium. National Committee for Clinical Laboratory Standards.

Some recently marketed macrolide antimicrobial agents possess physiochemical, antimicrobial, and pharmacokinetic advantages that enable their wider clinical use against Haemophilus influenzae infections. A five-laboratory study assessed the validity of existing or proposed azithromycin, clarithromycin, and erythromycin interpretive criteria for tests with H. influenzae isolates. National Committee for Clinical Laboratory Standards (NCCLS) methods, criteria, and quality-control guidelines were used. A total of 350 H. influenzae strains were processed, including fresh clinical isolates (250 strains) and replicate tests of 100 stock cultures sampling strains isolated from 1984 to 91. Azithromycin interpretive criteria (susceptible at < or = 4 micrograms/ml, > or = 12 mm) produced a 99.8% absolute agreement between the minimum inhibitory concentrations and disk diffusion results (0.2% false-susceptible error). Clarithromycin breakpoint criteria (susceptible at < or = 8 micrograms/ml, > or = 13 mm; and resistant at > or = 32 micrograms/ml, < or = 10 mm) produced high minor interpretive error, but < or = 1% combined false-susceptible and false-resistant discrepancies. Erythromycin interpretive guidelines were initially proposed for susceptible at < or = 0.5 microgram/ml, > or = 26 mm. This categorizes nearly all H. influenzae strains as resistant to this older macrolide. The NCCLS should consider the proposed erythromycin criteria for publication in appropriate tables, and a class drug should also be selected (azithromycin) that would best predict macrolide-class susceptibility for those agents indicated by the US Food and Drug Administration for H. influenzae infection chemotherapy (azithromycin and clarithromycin). No serious interpretive problems were observed with the current NCCLS criteria using Haemophilus test medium.

Anti-Bacterial Agents↗
PubMed2005

Synthesis of new bioactive venlafaxine analogs: novel thiazolidin-4-ones as antimicrobials.

A one-pot, three-component, microwave irradiated and conventional solution-phase synthesis of bioactive venlafaxine analogs such as 2,3-disubstituted-1,3-thiazolidin-4-ones 3a-j under mild conditions and their characterization are reported. The novel thiazolidin-4-ones, 3-(2-(1-hydroxycyclohexyl)-2-(4-methoxyphenyl)ethyl)-2-phenyl-thiazolidin-4-one 3a, 2-(2,6-difluorophenyl)-3-(2-(1-hydroxycyclohexyl)-2-(4-methoxyphenyl)ethyl)thiazolidin-4-one 3c, and 2-(furan-2-yl)-3-(2-(1-hydroxycyclohexyl)-2-(4-methoxyphenyl)ethyl)thiazolidin-4-one 3i, were characterized by the single crystal X-ray diffraction method. The cyclohexane ring of all the three molecules is in chair conformation. All the synthesized compounds were screened for their efficacy as antimicrobials in vitro by the disk diffusion and microdilution method against pathogenic strains such as Bacillus subtilis, Escherichia coli, Pseudomonas fluorescens, Xanthomonas campestris pvs, Xanthomonas oryzae, Aspergillus niger, Aspergillus flavus, Fusarium oxysporum, Trichoderma species, and Fusarium monaliforme species. Among these compounds 3c, 3j, 3g, 3d, and 3e showed potent antimicrobial activity, when compared to standard drugs.

Anti-Bacterial Agents↗
PubMed2006

Molecular typing of Salmonella enterica serotype Worthington isolates from infantile diarrhoea.

BACKGROUND AND OBJECTIVES: Salmonella Worthington has been known to be a causative agent for childhood diarrhoea. There is a paucity of information on the molecular relatedness of the strains isolated in various hospitals in India. The present study was carried out to attempt molecular typing of a cluster of Salmonella Worthington isolates obtained from cases of infantile diarrhoea during a six month period, from a tertiary care paediatric hospital in Delhi, India. METHODS: Nine isolates of S. Worthington obtained from faecal samples of infants suffering from diarrhoea during October 2001 to March 2002, were identified by the conventional biochemical methods and by serotyping. The antimicrobial susceptibility was determined by the disk diffusion method. Molecular typing was done by ribotyping. RESULTS: Eight patients were admitted to 3 different wards of the hospital and one was an outpatient. Four patients including the first patient visited the hospital with diarrhoea as the presenting symptom while five developed diarrhoea after admission. Stool microscopy showed no specific findings. Salmonella Worthington was isolated from stool cultures of these patients. Repeated cultures of the common drinking water source of the hospital and the milk supplied to children from central kitchen were negative for known pathogens. All S. Worthington isolates were resistant to all the beta-lactams tested including third generation cephalosporins. Eight isolates were sensitive to furazolidone and 6 to ciprofloxacin. Molecular characterization by ribotyping revealed four different clones. INTERPRETATION AND CONCLUSION: As four different ribotypes of the isolated Salmonella Worthington isolates were identified, it was clear that there was no single source of infection.

Diarrhea↗
PubMed1987

[Antibiotic resistance and serotypes of Streptococcus pneumoniae in Zurich (1984-1985)].

We have investigated the serotypes and sensitivity of 133 pneumococci against 11 antimicrobial agents in the agar dilution test. The strains had been isolated from clinical specimens sent to the Department of Medical Microbiology of the University of Zurich during 1984 and 1985. - Three strains (2.3%) had reduced sensitivity to penicillin G. 23 strains (17.3%) showed resistance or reduced susceptibility to tetracycline, one strain each (0.8%) to amoxycillin and cefaclor, and two strains each (1.5%) to erythromycin and sulfamethoxazole/trimethoprim. All pneumococcal strains investigated were susceptible to ceftazidime, ceftriaxone, chloramphenicol, vancomycin and ciprofloxacin. In view of this situation, routine testing of all clinically significant pneumococci is to be recommended. However, in the agar diffusion test the use of a penicillin G disk is unreliable and may give results with false sensitivity. Therefore, the susceptibility test should be performed with a disk containing oxacillin. - The prevalent capsular serotypes were - in descending order - types 3, 6, 23, 19, 14, 7, 8, 9, 1, and 17. 90.2% of the isolated pneumococci belonged to serotypes which are contained in the new vaccine "Pneumovax-23".

Amoxicillin↗
PubMed2003

Effects of permeabilizers on antimicrobial susceptibility of Stenotrophomonas maltophilia and Acinetobacter spp.

Isolates of the gram-negative bacteria Stenotrophomonas maltophilia and Acinetobacter spp. are naturally resistant to many classes of antibiotics. Using the disk diffusion technique it was shown that the membrane permeabilizers ethylenediaminetetraacetic acid, sodium citrate, and sodium polyphosphate increased susceptibility to a range of antibiotics including imipenem, ciprofloxacin, tetracycline, and rifampicin. These effects are probably due to the metal chelating properties of the permeabilizers.

Acinetobacter↗
PubMed2002

Rapid antimicrobial susceptibility testing of urinary tract isolates and samples by flow cytometry.

A multiparametric flow cytometry antimicrobial susceptibility test was developed and its performance was evaluated on clinical urine isolates and samples in comparison with standard methods. Alterations in cytoplasmic membrane integrity were monitored by propidium iodide, and the anionic probe bis-(1,3-dibutylbarbituric acid) trimethine oxonol (DiBAC4(3)) was used to measure changes in membrane potential. Microbial size and cellular content were analysed by light scattering. Twelve antibiotics were tested on 6 ATCC control strains, 22 urine isolates and 19 clinical urine samples, variously containing Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis, Enterococcus faecalis, Staphylococcus aureus, S. saprophyticus and S. epidermidis. Agreement between the flow cytometry results, broth microdilution and disk diffusion tests was 93.9% (n = 328 tests). Of the 20 discrepancies observed, 18 were for species other than E. coli. Perfect correlation was obtained with five antibiotics, whereas norfloxacin, nitrofurantoin and tetracycline were responsible for 13(65%) of the 20 discrepancies.

Anti-Bacterial Agents↗
PubMed1996

Comparison of antimicrobial susceptibilities of Corynebacterium species by broth microdilution and disk diffusion methods.

Corynebacterium species are increasingly being implicated in foreign-body infections and in immunocompromised-host infections. However, there are no specific recommendations on the method or the criteria to use in order to determine the in vitro activities of the antibiotics commonly used to treat Corynebacterium infections. The first aim of our study was to compare the susceptibilities of various species of Corynebacterium to vancomycin, erythromycin, and penicillin by using a broth microdilution method and a disk diffusion method. Second, the activity of penicillin against our isolates was assessed by using the interpretative criteria recommended by the National Committee for Clinical Laboratory Standards for the determination of the susceptibility of streptococci and Listeria monocytogenes to penicillin. Overall, 100% of the isolates were susceptible to vancomycin, while considerable variations in the activities of erythromycin and penicillin were noted for the different species tested, including the non-Corynebacterium jeikeium species. A good correlation in the susceptibilities of vancomycin and erythromycin between the disk diffusion and the microdilution methods was observed. However, a 5% rate of major or very major errors was detected with the Listeria criteria, while a high rate of minor errors (18%) was noted when the streptococcus criteria were used. Our findings indicate considerable variations in the activities of erythromycin and penicillin against the various species of Corynebacterium. Because of the absence of definite recommendations, important discrepancies were observed between the methods and the interpretations of the penicillin activity.

Anti-Bacterial Agents↗
PubMed2006

Frequency of serovars and antimicrobial resistance in Shigella spp. from Brazil.

A total of 296 Shigella spp. were received from State Public Health Laboratories, during the period from 1999 to 2004, by National Reference Laboratory for Cholera and Enteric Diseases (NRLCED)--IOC/Fiocruz, Rio de Janeiro, Brazil. The frequency of Shigella spp. was: S. flexneri (52.7%), S. sonnei (44.2%), S. boydii (2.3%), and S. dysenteriae (0.6%). The most frequent S. flexneri serovars were 2a and 1b. The highest incidence rates of Shigella isolation were observed in the Southeast (39%) and Northeast (34%) regions and the lowest rate in the South (3%) of Brazil. Strains were further analyzed for antimicrobial susceptibility by disk diffusion method as part of a surveillance program on antimicrobial resistance. The highest rates of antimicrobial resistance were to trimethoprim-sulfamethozaxole (90%), tetracycline (88%), ampicillin (56%), and chloramphenicol (35%). The patterns of antimicrobial resistance among Shigella isolates pose a major difficulty in the determination of an appropriate drug for shigellosis treatment. Continuous monitoring of antimicrobial susceptibilities of Shigella spp. through a surveillance system is thus essential for effective therapy and control measures against shigellosis.

Anti-Bacterial Agents↗
PubMed2003

Sensitization of Staphylococcus aureus and Escherichia coli to antibiotics by the sesquiterpenoids nerolidol, farnesol, bisabolol, and apritone.

The sesquiterpenoids nerolidol, farnesol, bisabolol, and apritone were investigated for their abilities to enhance bacterial permeability and susceptibility to exogenous antimicrobial compounds. Initially, it was observed by flow cytometry that these sesquiterpenoids promoted the intracellular accumulation of the membrane-impermeant nucleic acid stain ethidium bromide by live cells of Lactobacillus fermentum, suggesting that enhanced permeability resulted from disruption of the cytoplasmic membrane. The ability of these sesquiterpenoids to increase bacterial susceptibility to a number of clinically important antibiotics was then investigated. In disk diffusion assays, treatment with low concentrations (0.5 to 2 mM) of nerolidol, bisabolol, or apritone enhanced the susceptibility of Staphylococcus aureus to ciprofloxacin, clindamycin, erythromycin, gentamicin, tetracycline, and vancomycin. Nerolidol and farnesol also sensitized Escherichia coli to polymyxin B. Our results indicate the practical utility of sensitizing bacteria to antimicrobials with sesquiterpenoids that have traditionally been used as flavorants and aroma compounds in the food and perfume industries.

Anti-Bacterial Agents↗
PubMed1990

Antimicrobial susceptibility pattern of Aeromonas and Plesiomonas strains isolated from patients with diarrhoea in Nigeria.

The susceptibilities of 53 isolates of Aeromonas species and 16 Plesiomonas shigelloides, from patients with diarrhoea, to 15 commonly used antimicrobial agents were determined by the disk-agar diffusion technique. All the strains were susceptible to ofloxacin, a recent quinolone. Also, over 70 pc of our strains were susceptible to gentamicin, carbenicillin, ceftriaxone, erythromycin, Chloramphenicol, tetracycline and co-trimoxazole. However, less than 30 pc of our strains were susceptible to ampicillin. Results of this in vitro study indicate that for cases of serious Aeromonas or Plesiomonas infections requiring antimicrobial therapy, ofloxacin, gentamicin, carbenicillin or chloramphenicol could be useful.

Aeromonas↗
PubMed2003

Susceptibility testing for bovine respiratory and enteric disease.

The interpretation of susceptibility results for antimicrobials with NCCLS-approved veterinary-specific breakpoints and where the methods also were NCCLS-approved are well established. When these same breakpoints are applied to other applications, however, the interpretation is not so clear. In these cases, a finding of S based on serial-dilution breakpoints puts the isolate in a defined population of bacteria with an MIC equal to or below the S breakpoint. An R result, in these cases, indicates that the organism may have an MIC equal to or greater (with no limits) than the R breakpoint. Extended-dilution testing yields more specific information about the isolate MIC. The relationship of disk-diffusion zone diameters to serial-dilution MICs is correlated on the basis of specific bacterial populations. When disk-diffusion results are interpreted for isolates other than those used for interpretive criteria development, the clinician is left wondering if the zone-diameter results now have a different relationship to serial-dilution results. Furthermore, the question of predictive value of the serial-dilution break-points still remains. The veterinary clinician should be aware of the differences in susceptibility testing predictive value for different applications. When approved veterinary-specific interpretive criteria are not available, then it is appropriate to keep records of clinical response related to susceptibility testing results for common therapies. Advice should be sought on the relationship of pathogen MICs to pharmacokinetic-pharmacodynamic parameters in these situations.

Animals↗
PubMed1998

Susceptibility pattern of Streptococcus pneumoniae among pre-school children in Kota Bharu, Malaysia.

Streptococcus pneumoniae (S. pneumoniae) is the most common bacterial cause of pneumonia, meningitis, and otitis media, with the highest incidence among young children and the elderly. S. pneumoniae was once routinely susceptible to penicillin, but since the mid-1980s the incidence of resistance to penicillin and other antimicrobial agents has been increasing all over the world. To optimize empirical regimens and initial therapy for S. pneumoniae infections, clinical healthcare providers must be informed about the prevalence and pattern of drug resistance among the isolates in their communities. No such data are available for the Malaysian population. Therefore, this study was designed to determine the antibiotic susceptibility pattern of S. pneumoniae among colonized pre-school children in Kota Bharu, Malaysia. Pharyngeal swabs were collected from children 1 month to 6 years of age. S. pneumoniae isolates were identified according to the standard and tested for penicillin resistance with a 1-microgram oxacillin disk by the Kirby-Bauer disk diffusion methods. Of 355 nasopharyngeal specimens obtained from kindergarten students, in-patients and pediatric clinics over a period of 1 year, S. pneumoniae was isolated from 36 (10 per cent). All isolates, except one, were susceptible to penicillin. The resistant isolates was susceptible to erythromycin, chloramphenicol and cephalosporins.

Child, Preschool↗
PubMed1996

An increase in Helicobacter pylori strains resistant to metronidazole: a five-year study.

BACKGROUND: Metronidazole is one of the most commonly used antimicrobial agents for the treatment of Helicobacter pylori infection. Resistance to metronidazole has been reported worldwide but with a wide range of prevalence. We started using the classical triple therapy (bismuth, tetracycline, and metronidazole) for H. pylori infection in 1991 but recently have experienced a decline in its efficacy in curing the infection. Thus our aim was to investigate in a single center the prevalence of metronidazole-resistant H. pylori over a period of 5 years. MATERIALS AND METHODS: A total of 1,015 different H. pylori strains collected over a period of 5 years were tested for sensitivity against metronidazole, ampicillin, tetracycline, and imipenem. Antibiotic sensitivity was tested by the disk diffusion and agar dilution methods. To elucidate further the possible relationship between these metronidazole-resistant strains, genomic DNA digestion by the Hae III endonuclease and ribotyping were undertaken in a selected group of isolates. RESULTS: In 1991, 29 of 132 (22.0%) tested strains of H. pylori were found to be resistant to metronidazole. Since our initiation at that time of a triple therapy of bismuth, metronidazole, and tetracycline, the prevalence of metronidazole-resistant strains rose rapidly to 73.2% in 1995. All H. pylori isolates were sensitive to ampicillin, tetracycline, and imipenem. A high degree of genomic heterogeneity was found among these isolates. Thus it is unlikely that the resistant strains of H. pylori were originated from a single clone. CONCLUSIONS: This study shows a rapid increase in metronidazole-resistant H. pylori with the use of an anti-Helicobacter regimen that contains metronidazole. We anticipate that the efficacy of metronidazole-containing anti-Helicobacter regimens will decline with the rapid rise in resistant strains of H. pylori.

Adolescent↗
PubMed1997

Reappraisal of the antimicrobial susceptibilities of Chryseobacterium and Flavobacterium species and methods for reliable susceptibility testing.

Several Flavobacterium species, comprising a heterogeneous group of gram-negative bacilli that are capable of causing opportunistic infections in humans, have recently been reclassified as Chryseobacterium or Myroides species. Intrinsically resistant to a number of antibiotics, these organisms have been reported to be susceptible to vancomycin and certain other drugs that are normally active against gram-positive bacteria. By using the National Committee for Clinical Laboratory Standards (NCCLS) broth microdilution procedure, 58 clinical isolates of former flavobacteria (36 Chryseobacterium meningosepticum isolates, 11 C. indologenes isolates, 3 C. gleum isolates, 4 unspeciated former members of Flavobacterium group IIb, and 4 Myroides odoratum isolates) were tested with 23 antibiotics, including conventional and investigational agents. In addition, the broth microdilution results were compared to those generated by agar dilution, E-test, and disk diffusion for vancomycin and piperacillin-tazobactam. Compared to the NCCLS microdilution results, there were 7.1 and 17.9% very major errors with piperacillin-tazobactam by agar dilution and E-test, respectively. In addition, there were from 12.1 to 48.3% minor errors with both procedures with vancomycin and piperacillin-tazobactam. The very major and minor error rates were unacceptably high with disk testing of piperacillin-tazobactam; the use of enterococcal vancomycin disk breakpoints (zone diameter of > or =17 mm = susceptible) resulted in >20% minor errors but only one very major error. All of the isolates were susceptible to minocycline; over 90% were susceptible to sparfloxacin, levofloxacin, and clinafloxacin; and 88% were susceptible to rifampin. None was susceptible to vancomycin. When Chryseobacterium or Myroides species are isolated from serious infections, susceptibility testing by broth microdilution should be performed and therapy should be guided by those results.

Anti-Bacterial Agents↗
PubMed1994

Antimicrobial susceptibility of Pasteurella haemolytica and Pasteurella multocida isolated from pneumonic ovine lungs.

The in vitro susceptibilities of Pasteurella haemolytica biotypes A and T and P multocida from pneumonic ovine lungs to penicillin, ampicillin, oxytetracycline, chloramphenicol, erythromycin, kanamycin, neomycin, gentamicin, streptomycin and lincomycin were determined by the disk diffusion method. All the isolates were sensitive to chloramphenicol and resistant to lincomycin. The isolates of P haemolytica biotype A were consistently more sensitive to penicillin, ampicillin, oxytetracycline, erythromycin and streptomycin than those of biotype T.

Animals↗
PubMed2006

Prevalence and antimicrobial resistance of Campylobacter isolated from retail raw chicken and beef meat, Tehran, Iran.

Campylobacter spp. is a leading cause of human diarrhea. The common source of infection is contaminated food, particularly poultry. The veterinary use of antimicrobial drugs has been suggested to be largely responsible for resistance in human isolates of this zoonotic pathogen. From April to October 2004, 241 samples of chicken and beef meat for sale in retail outlets in Tehran (Iran) were analyzed for the presence of Campylobacter. Totally, 88 (36.5%) Campylobacter strains were isolated. Campylobacter was isolated from a significantly larger number of chicken (63%) than beef (10%) meat (P < 0.0001). Susceptibilities of 72 strains were determined for eight antimicrobial drugs using the disk diffusion assay. Resistance to nalidixic acid was the most common finding (75%), followed by resistance to ciprofloxacin (69.4%), tetracycline (45.8%), amoxicillin (11.1%), streptomycin (4.2%), chloramphenicol (2.8%) and gentamicin (1.4%). None of the isolates was resistant to erythromycin. Multidrug resistance was seen in 75% of the Campylobacter strains.

Animals↗
PubMed1986

In vitro activity of piperacillin, ticarcillin, mezlocillin, ticarcillin-clavulanic acid, aztreonam, ceftazidime, azlocillin, cefoperazone, and thienamycin against Pseudomonas aeruginosa.

The in vitro susceptibility of 103 well-characterized strains of Pseudomonas aeruginosa to nine antimicrobial agents was assessed by means of the Kirby-Bauer disk diffusion assay and the microtiter minimal inhibitory concentration assay. The antimicrobials, from the most to the least active against P aeruginosa, were thienamycin greater than ceftazidime greater than piperacillin greater than azlocillin greater than cefoperazone greater than aztreonam greater than ticarcillin greater than ticarcillin-clavulanic acid greater than mezlocillin. The resistance patterns of the antimicrobial agents suggest that P aeruginosa resistant to a penicillin, cephalosporin, or aztreonam may be susceptible to thienamycin.

Anti-Bacterial Agents↗