Percentage Of Resistant Strains Research Articles

Trends of Antimicrobial Susceptibility of Neisseria gonorrhoeae Isolates Between 2012 and 2023: Results From an Open Italian Cohort.

Neisseria gonorrhoeae (Ng) is a public health priority because of the rapid evolution of antimicrobial resistance, the emergence of antibiotic resistance, and the absence of a vaccine against Ng. The aim of this study was to investigate trends in the minimum inhibitory concentration and resistance (R) or reduced susceptibility (DS) of Ng cases to ceftriaxone (CRO), azithromycin (AZM), tetracycline (TET), benzylpenicillin (PenG), and ciprofloxacin (CIP) during a 10-year period. We conducted a retrospective analysis on an open cohort of Ng cases diagnosed on rectal, urethral, and pharyngeal samples at San Raffaele Scientific Institute, between September 2012 and February 2023. Minimum inhibitory concentrations of antibiotics were determined by gradient-test strips. Bivariate linear regression models were applied on logarithmic minimum inhibitory concentrations values; Cochran-Armitage test was used to determine a linear trend in the proportions of resistant strains. A total of 436 Ng isolates from 352 individuals were analyzed. Minimum inhibitory concentrations of CRO and PenG reduced over time ( P < 0.001, P = 0.030), AZM increased ( P = 0.001), and CIP and TET did not change ( P = 0.473, P = 0.272). The percentages of resistant strains were as follows: PenG, 89.9%; TET, 90.8%; CIP, 48.2%; AZM, and 4.4%. CRO-DS strains were 8.7%, and only 1 case of CRO-R was identified. The proportion of resistant strains increased over time for AZM ( P = 0.007), TET ( P = 0.001), and CIP ( P < 0.001), whereas it decreased for PenG ( P < 0.001) and CRO-DS/R strains ( P < 0.001). Ng strains showed high susceptibility to CRO, although we identified cases of DS/R and observed high levels of susceptibility to AZM. Overall, the recommended primary regimen for Ng treatment was confirmed to be effective.

Comparative analysis of resistance of main etiological agents of chronic osteomyelitis isolated from association and in monoculture

Introduction. To date, a significant number of works have been published devoted to the analysis of the sensitivity of the leading causative agents of osteomyelitis to modern drugs, however, in the available literature there are no data on a comparative analysis of the antibiotic resistance of bacteria isolated from the osteomyelitis focus from the association and in monoculture. Purpose of the work: to compare the resistance profiles of the leading causative agents of osteomyelitis, depending on the bacterial composition of the focus of infection.Materials and methods. The study included 216 clinical isolates, of which 114 were isolated as part of two-component associations, 102 – in a monoculture from pathological material in patients with chronic osteomyelitis who were treated in the purulent department of National Medical Scientific Centre of Traumatology and Orthopedics n.a. academician G.E. Ilizarov (Kurgan, Russia) from 2018 to 2020. To analyze the resistance profiles, depending on the type of microorganism, modern drugs used in the clinic for the treatment of osteomyelitis were taken into account.Results and its discussion. Effective drugs against P. aeruginosa strains isolated from the association were polymyxin and meropenem, and in monoculture–polymyxin, piperacillin/tazobactam, tobramycin; in relation to strains of K. pneumoniae isolated from the association, it was imipenem, in monoculture – amikacin. S. aureus strains isolated both from the association and in monoculture were highly susceptible to antibacterial drugs.Conclusion. The analysis of the sensitivity of the leading causative agents of osteomyelitis, isolated in monoculture and from the association, to the antibacterial drugs used in the clinic, showed significant differences in the resistance profiles between the groups: for S. aureus strains, 4 antibiotics tested out of 13, for P. aeruginosa strains – 7 out of 13, for K. pneumoniae strains – 12 out of 16. The tested antibacterial drugs were less active against P. aeruginosa and S. aureus strains isolated from associations. In contrast, the percentage of resistant strains of K. pneumoniae was higher among monocultures.

Comparison of Phenotypic and Genotypic Patterns of Antimicrobial-Resistant Bacteroides fragilis Group Isolated from Healthy Individuals in Vietnam and Japan.

PurposeNormal non-pathogenic flora can harm the host by acting as a reservoir of resistance determinants that are potentially transferable to human pathogens. This study aimed to assess the phenotypic and genotypic antimicrobial susceptibility patterns of the Bacteroides fragilis group (BFG) isolated from healthy individuals in Vietnam and Japan in order to elucidate the prevalence of antimicrobial resistance in human flora in the two economically and geographically different countries.Materials and MethodsBFG was isolated from fecal samples of 80 healthy individuals in Vietnam (n=51) and Japan (n=29). Isolated strains were identified using MALDI-TOF MS, and the minimum inhibitory concentration (MIC) of 18 antibiotics was determined using the agar dilution method. Additionally, 20 antimicrobial resistance genes were detected using standard PCR.ResultsA total of 139 BFG strains belonging to 11 BFG species were isolated from the two countries, with diversity in the prevalence of each species. B. fragilis was not the predominant species. Isolations from Vietnam and Japan showed some similarities in terms of MIC50 values, MIC90 values, and the percentage of resistant strains. However, isolations from Vietnam showed significantly higher resistance to piperacillin, cefmetazole, clindamycin, tetracycline, and minocycline. ErmB, tet36, tetM, nim, catA, and qnrA were not found in either country. CepA was more common in B. fragilis than in non-fragilis Bacteroides. In contrast, cfiA, ermG, mefA, msrSA, tetX, tetX1, bexA, qnrB, and qnrS were found only in non-fragilis Bacteroides. There were differences in the prevalence of ermG, linA, mefA, msrSA, and qnrS between isolates from Vietnam and Japan.ConclusionThis study is the first report on the antimicrobial susceptibility patterns in the BFG isolated from healthy individuals in Vietnam and Japan. Compared to isolations from Japan, isolations from Vietnam showed significantly higher resistance to antimicrobial agents. The distribution of various antibiotic resistance genes also differed between the two countries.

Antimicrobial Resistance of Listeria monocytogenes Strains Isolated from Humans, Animals, and Food Products in Russia in 1950-1980, 2000-2005, and 2018-2021.

Susceptibility of 117 L. monocytogenes strains isolated during three time periods (1950–1980; 2000–2005, and 2018–2021) to 23 antibiotics was tested by the disk diffusion method. All strains were sensitive to aminoglycosides (gentamicin, kanamycin, neomycin, streptomycin), glycopeptides (vancomycin and teicoplanin), clarithromycin, levofloxacin, amoxicillin/clavulanic acid, and trimethoprim/sulfamethoxazole. Resistance to clindamycin was observed in 35.5% of strains. Resistance to carbapenems, imipenem and meropenem was found in 4% and 5% of strains, respectively. Resistance to erythromycin, penicillin G, trimethoprim, and ciprofloxacin was found in 4%, 3%, 3%, and 2.5% of strains, respectively. Resistance to tylosin, ampicillin, enrofloxacin, linezolid, chloramphenicol, and tetracycline was found in less than 2%. Three strains with multiple antibiotic resistance and 12 strains with resistance to two antibiotics were revealed. Comparison of strains isolated in different time periods showed that the percentage of resistant strains was the lowest among strains isolated before 1980, and no strains with multiple antibiotic resistance were found among them. Statistical analysis demonstrated that the temporal evolution of resistance in L. monocytogenes has an antibiotic-specific character. While resistance to some antibiotics such as ampicillin and penicillin G has gradually decreased in the population, resistance to other antibiotics acquired by particular strains in recent years has not been accompanied by changes in resistance of other strains.

Antibiotic resistance of non-fermenting Gram-negative bacilli isolated at a large Infectious Diseases Hospital in North-Eastern Romania, during an 11-year period.

Increased antibiotic resistance of non-fermenting Gram-negative bacilli (NFGNB) associated with increased morbidity and mortality makes the infections they produce a major public health problem. This study aims to assess the evolution of antibiotic susceptibility and the level of NFGNB antibiotic resistance. We carried out a retrospective study on 994 NFGNB strains which had been isolated in the Clinical Laboratory of the "Sf. Parascheva" Clinical Hospital of Infectious Diseases, Iaşi, during a period of 11 years (2008-2018). Of the 994 NFGNB analyzed, 322 were Acinetobacter spp. and 672 Pseudomonas aeruginosa. Also, 882 NFGNB were isolated from non-sterile sites, in which there was a higher burden of P. aeruginosa strains (n=617). Acinetobacter spp. presented over 70% resistance to the majority of antibiotics. Three pandrug-resistant P. aeruginosa strains were identified. The rate of colistin resistance was 2.91% for P. aeruginosa and 3.33% for Acinetobacter spp. A comparative analysis of the antibiotic susceptibility of strains isolated from non-sterile sites versus sterile sites revealed statistically significant differences only for Acinetobacter spp. The percentage of resistant strains was significantly higher in tracheobronchial aspirate compared to sputum. The results show that Acinetobacter spp. is substantially more resistant to antibiotics compared to P. aeruginosa and that the use of medical devices can favor the occurrence of infections with multidrug-resistant strains.

Bacterial resistance to minocycline after adjunctive minocycline microspheres during periodontal maintenance: A randomized clinical trial.

Despite widespread use, the impact of minocycline hydrochloride microspheres on the shifts of oral bacterial species resistant to minocycline remains unknown. This study aimed at examining the percentage and taxonomy of minocycline-resistant isolates in saliva and subgingival plaque samples before and after minocycline microspheres application in periodontitis patients during maintenance. Patients received supra- and sub-gingival debridement with (test) or without (control) minocycline microspheres application to sites with probing depth>4mm and were clinically monitored at baseline, 1, 3, and 6 months. Samples were collected at baseline, 1 and 6 months and analyzed via cultivation with or without 4μg/mL minocycline. Percentage of resistant strains was determined by colony counting and taxonomy by checkerboard DNA-DNA hybridization. Significant clinical changes were sought with the Mann-Whitney test and differences in percentage of resistant isolates with the Friedman and Mann-Whitney tests. Groups showed similar clinical improvements. Mean percentage of resistant isolates rose at 1 month and decreased at 6 months in saliva and plaque samples in test group (P<0.05) but remained unchanged in control group. Percentage of resistant isolates of Gemella morbillorum and Eubacterium saburreum increased significantly at 6 months in both groups. Antibiotic resistance by Aggregatibacter actinomycetemcomitans, Tannerella forsythia, and Porphyromonas gingivalis was either absent or infrequent. Minocycline microspheres result in transient selection of minocycline resistant species in saliva and subgingival plaque samples.

The most common bacterial isolates from wound samples – a three-year study

Aim: The aim of our study was to determine the most common bacteria isolated from wound samples and tо compare the frequency of the resistant bacteria isolated over a 3-year period. Material and methods: During a three years period (2017-2019) a total of 11 863 wound samples (wound swabs, punctuates, exudates, tissue, etc.) were obtained from the hospitalized patients in the University Clinics of the ,,Mother Theresa” campus, the City hospital ,,8th September” and the University Clinic for surgical diseases ,,St. Naum Ohridski” in Skopje. All samples were processed at the Institute of Microbiology and Parasitology, Faculty of Medicine, Skopje. They were examined by standard microbiology techniques. Identification and susceptibility of microorganisms were done by both standard methods and automatized Vitek 2 system. Results: Out of a total number of samples, which was 3 463 in 2017, 4 127 in 2018 and 4 273 in 2019, positive were 2 068 (60%), 2 302 (55.8%) and 2 387 (55.9%), respectively. From the total of aerobes/facultative anaerobes (2 758, 2 949 and 3 279 in three consecutive years, 2017, 2018 and 2019, respectively), Staphylococcus aureus was the most predominant isolate (19.5%, 16.6%, 16.9%) followed by Enterococcus spp (16%, 16%, 16.7%), Pseudomonas aeruginosa (12%, 13%, 12.7%) and E. coli (10%, 10.4%, 10.7%). Considering anaerobic bacteria, the percentage of Gram positive anaerobes (Peptostreptococcus) has decreased from 33% to 18% out of a total number of anaerobes, unlike Gram negative anaerobes in which the increasing percentage was mostly observed in bacteria of the genus Bacteroides (from 39% to 45%). The percentage of the resistant strains of MRSA, CNS-MR and VRE was almost the same in that period. In Gram-negatives the percentage of ESBL-positive isolates of E. coli and Enterobacter spp. increased consecutively from 2017 to 2019. The increase in the percentage of resistant strains was more noticeable in ESBL-positive isolates of Klebsiella pneumonia between 2017 and 2018, but in 2019 a percentage decrease can be observed. Considering carbapenem-resistant (CR) Enterobacterales, an increase in the resistance was noticeable in K. pneumonia. The increase in the percentage of resistant strains in Enterobacter spp. between 2017 and 2018, as well as the decrease between 2018 and 2019 was statistically significant. The percentage of CR-isolates of Pseudomonas aeruginosa was from 30% to 38% and for Acinetobacter spp. this percentage was from 81% to 85%. Conclusion: The knowledge of the most commonly isolated bacterial pathogens, especially the presence of resistant bacteria, is crucial and should be continuously monitored in order to understand, construct and update effective treatment algorithms and guidelines.

Retrospective Analysis of Antibiotic Therapy and Sensitivity to Antifungals of Fungi of the Genus Candida, Secreted from Patients with Viral-Bacterial Pneumonia Associated with COVID-19

The appointment of antibacterial agents for the treatment of pneumonia that develops with COVID-19 is one of the treatment regimens. Antibacterial agents are prescribed only in the case of presence of confirmed bacterial co-infection, but can be appointed empirically. This approach promotes the development of antibiotic resistance of opportunistic and saprophytic microflora of almost all habitats, including the oropharynx that can lead to dysbiotic lesions with activation of fungal flora. The aim of the study was to analyze the composition of the oropharyngeal microbiome of patients with viral and bacterial pneumonia who took antibiotics, as well as the sensitivity of fungi of the genus Candida to antifungal drugs for effective treatment of the underlying disease. Methods. The results of bacteriological examination of 113 inpatients treated with a diagnosis of COVID-19 were analyzed. Microbiological examination of oropharyngeal swabs was performed by the classical bacteriological method with dosed seeding of suspended material on differential diagnostic media (in particular Saburo medium was used for selection of fungi of the genus Candida) and genus identification by morphological, cultural, biochemical properties. Results. PCR tests were performed for all patients in the clinical trial to confirm the diagnosis of viral and bacterial pneumonia. According to the results of bacteriological examination, fungi of the genus Candida were found in 52 (46.0%) patients with pneumonia associated with COVID-19. The analysis of prescriptions showed that only 14 (26.9%) patients were treated with one antibiotic, two antibiotics were prescribed to 31 (59.6%) patients, and three – 7 (13.5%). In the structure of antibiotic therapy, the lion’s share were cephalosporins of the third generation (ceftriaxone, hepacef) – 33 (63.5%), and macrolides (azithromycin) – 16 (30.8%) patients. In the structure of the oropharyngeal microbiome, according to the results of bacteriological research, fungi of the genus Candida significantly prevailed, which were found in 52 (46.0%), and in 29 patients (25.7%) S. pneumoniae was found. The sensitivity of fungi of the genus Candida to antifungal agents was analyzed, the maximum number of resistant strains was detected to nystatin and amphotericin – 38.5% and 26.9%, with only 8 (15.3%) fungi of the genus Candida sensitive to nystatin. Conclusions. All patients with viral-bacterial pneumonia associated with COVID-19 received antibiotic therapy, the lion’s share were third-generation cephalosporins (63.5%), and macrolides – (30.8%). According to the results of bacteriological examination of the oropharyngeal microbiome after antibiotic therapy, fungi of the genus Candida predominated (46.0%), followed by S. pneumoniae (25.7 %). Isolated strains of fungi of the genus Candida showed resistance to nystatin (38.5%) and amphotericin (26.9%). Antifungal agents of the imidazole subgroup have shown high efficiency and a low percentage of resistant strains, which allows us to recommend them for the treatment of complications of COVID-19 caused by fungi of the genus Candida.

Biological microchip for assessing tetracycline-resistance in &lt;i&gt;Neisseria gonorrhoeae&lt;/i&gt; clinical isolates in Russian Federation

A total of 399 Neisseria gonorrhoeae clinical isolates collected in different regions of the Russian Federation in 20152017 were analyzed for tetracycline susceptibility and genetic markers of resistance. Drug susceptibility testing was performed by serial dilution method in agar and minimum inhibitory concentration (MIC) was measured according to the Russian “Guidelines for microbial susceptibility testing for antibacterial agents No. 4.2.1890-04”. Tetracycline resistance determinants were studied by using hydrogel microarray with immobilized oligonucleotide probes able to identify a series of chromosomal mutations and detect plasmid tetM gene. Different resistance determinants were found in 193 isolates (48.4%). Mutation in codon 57 in the rpsJ gene (41.2%) was most common that decreases tetracycline affinity to ribosome 30S subunit, mainly due to Val57Met substitution both as a point mutation as well as in combination with others. Mutations in the rpsJ gene were found in strains with the intermediate tetracycline susceptibility. Mutations in the porB gene (lower tetracycline influx) held the se cond place in prevalence pattern (23.1%); the Gly120Lys substitution usually led to emergence of tetracycline resistance either as a point mutation or in combination with other substitutions. Substitutions of Gly120 for other residues (Asp, Asn, and Thr) and Ala121 for Asp, Asn, and Gly had much less effect on resistance level. The –35 delA deletion in the promoter region of mtrR gene (increased expression of MtrC-MtrD-MtrE efflux pump) was observed in 11.3% strains. The tetM gene was found in 27 strains including 17 American and 10 Dutch type tetM determinants. Evolutionary tree was constructed for the tetM genes with the estimation of their homology with similar genes in genera Streptococcus, Enterococcus and Mycoplasma. Mutations in chromosomal genes resulted in increase of tetracycline MIC up to 2–4 mg/L; 4 mg/L MIC was observed in case of simultaneous presence of several mutations. Strains bearing tetM gene-containing plasmid showed extremely high resistance level: MIC ≥ 8 mg/L (64 mg/L for the two samples). Thus, long-lasting withdrawal of tetracycline use for treatment of gonococcal infections in Russia (since 2003) resulted in decreased percentage of resistant strains (including strains with intermediate susceptibility) from 75% down to 45.4%. However, currently tetracycline resistance in Russia remains elevated that is explained by the presence of different resistance determinants in the half of isolates under study.

Comparison of in vitro synergistic effect between clarithromycin or azithromycin in combination with amikacin against Mycobacterium intracellulare.

This study compared the in vitro synergistic effect between clarithromycin or azithromycin in combination with amikacin against Mycobacterium intracellulare. In vitro antimicrobial susceptibility of M. intracellulare isolates was determined by the broth microdilution method in cation-adjusted Mueller-Hinton broth. The fractional inhibitory concentration index (FICI) was also calculated to assess synergy between the antimicrobial agents. A total of 32 respiratory M. intracellulare isolates were included in the study. Clarithromycin was the most potent agent against M. intracellulare, with MIC50 and MIC90 values (minimum inhibitory concentration required to inhibit 50% and 90% of the isolates, respectively) of 0.5μg/mL and 8μg/mL, respectively. Azithromycin and amikacin also showed moderate activity against M. intracellulare, with MIC90 values of 16μg/mL and 4μg/mL, respectively. The percentage of resistant strains among the 32 M. intracellulare isolates was 3.1% for clarithromycin, 9.3% for amikacin and 12.5% for azithromycin. The presence of amikacin had no effect on the MIC50 of clarithromycin, whereas the presence of amikacin resulted in a two-fold increase in the MIC50 of azithromycin. In addition, antagonism for the clarithromycin-amikacin combination was noted in 5 (15.6%) of the 32 M. intracellulare isolates, which was significantly lower than for the azithromycin-amikacin combination (14/32; 43.8%) (P = 0.042). These data demonstrated that clarithromycin displayed more potent in vitro activity against M. intracellulare isolates than azithromycin. In addition, the antagonistic effect between azithromycin and amikacin was more frequent in M. intracellular isolates than that between clarithromycin and amikacin.

Antimicrobial resistance of Lactobacillus spp. from fermented foods and human gut

A total of 122 Lactobacillus strains were isolated from household-prepared or commercial yogurts and pickles in Sichuan, among which 15 representative strains, along with another 37 strains isolated from human guts, were analyzed for their antimicrobial resistance (AMR) to 17 clinically significant antimicrobials applied in China by agar dilution method. The correlation of AMRs in Lactobacillus plantarum from fermented foods and human gut was examined. The AMRs varied with Lactobacillus species. For L. plantarum, the distributions of minimum inhibitory concentration to 12 antimicrobials were correlated between food and gut source (P < 0.05), and the percentages of resistant strains from foods and gut were also similar (P > 0.05) except to norfloxacin, where the AMR was more severe in gut than in foods (P < 0.05), while all 14 high-level vancomycin-resistant strains were from gut. Illustrated by L. plantarum, the severity of resistance to most antimicrobials in lactobacilli from fermented foods and human gut gradually converged, with gut ones taking the leading role. Accordingly, AMR in human gut lactobacilli was more likely the consequence of clinical medication instead of acquired from fermented foods. Lactobacillus strains widely utilized in fermented foods would unlikely aggravate their AMR in human guts.

The clinical significance of bacteria Acinetobacter spp., separated from patients with chronic osteomyelitis.

The article deals with the results of analysis of 17 clinical strains of Acinetobacter spp., isolated from wounds of patients with chronic osteomyelitis of long bones. In 8 patients strains of Acinetobacter spp. were isolated in mono-culture, in 8 - in composition of association with staphylococci (Staphylococcus aureus - 4, S.epidermidis - 2, S.hatmolyticus - 1, S.capitis -1) and in one patient - with strains of Enteroccocus faecalis. highly adhesive characteristics were established in 29% of isolates of Acinetobacter spp, average adhesive - in 43% and low adhesive - in 28%. The average index of adhesiveness of analyzed strains made up to 2.86±0.02 units. The strains with high adhesive potential were isolated from associations with Staphylococcus spp. The strains of Acinebacter spp. are characterized as far as of incubating by increasing activity of formation of biofilm on the surface of 96 alveolar tray. The calculated integral coefficient (K>0.5 units) testifies high percentage of strains resistant to selected antibiotics. It is established that the most effective in relation to Acinebacter spp. were aminoglycosides (gentamycin and tobramycin) and carbapenems (meropenem, imipenem).The percentage of resistant strains did not exceed 38%. The implemented study demonstrated that inter-microbial relationships ameliorate capacity of association-forming strains Acinebacter spp. to form bio-films. The derived values of bio-film-forming capacity and coefficient of resistance of clinical isolates Acinebacter spp.isolated from patients with chronic osteomyelitis testify their high pathogenicity. The treatment of infection associated with Acinebacter spp. is to consider both results of antibioticgram and data concerning virulent characteristics of isolated agent.

Study of oral and gingival microbial flora in institutionalized mentally retarded patients of Sari-2011

Introduction and Objectives: Mental retardation (MR) is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive function and deficits in two or more adaptive behaviors. The prevalence and severity of dental caries‚gingivitis and periodontitis is high in patients with mental retardation. This shift to a diseased state may lead to the experience of a high mortality from septicemia‚ sepsis‚ pneumonia and endocarditis.Our purpose was to study oral and gingival microbial flora in institutionalized mentally retarded patients of Sari and to estimate D% (percentage with untreated decayed teeth) and DMFT% (percentage of population affected with dental caries)Materials and Methods: This study was a descriptive cross-sectional type in which Plaque samples were collected from the mouth and gingiva of 138 institutionalized mentally retarded patients of Sari to culture in specific media to identify the microorganisms. In this study anaerobic bacteria were not isolated because the instrument was not available in the laboratory. The information has been analyzed by X2 T-test methods by SPSS 17 software.Results: The isolated microorganisms were: pnuemococci S(37.7%); Streptococci sp(18.8%); E.coli (16.7%); Staphylococcus(1.4%); Neisseria sp(45/6%); Salmonella(8.7%); Proteus(3.6%); Diphteroid (4.2%); Pseudomonas(0.7%). The percentage of resistant strains was found to be highest with penicillin(67.9%) and lowest with vancomycin(11%).Conclusion: D% between all the patients were (66.66%) . Bacterial flora in mentally retarded patients were significanty higher in frequency than in normal persons. With improvement in oral health care, we can decreasethese undesirable changes.Key words: Oral and gingival microbial flora, Mental retardation, D%, Sari

Increase over time in the prevalence of multiple antibiotic resistance among isolates of Listeria monocytogenes from poultry in Spain

The aim of this study was to determine and compare the antibiotic resistance profiles of Listeria monocytogenes isolates obtained from poultry in North-Western Spain in 1993 and 2006. The prevalence of Listeria spp. and L. monocytogenes was also investigated. A total of 202 samples were analysed (100 in 1993 and 102 in 2006). Samples taken in 1993 and 2006 showed a similar (P > 0.05) prevalence for both Listeria spp. (95.0% and 92.1%, respectively) and L. monocytogenes (32.0% and 24.5%). In both 1993 and 2006 the species most frequently detected was Listeria innocua, followed by L. monocytogenes. Other species isolated were Listeria welshimeri, Listeria grayi and Listeria ivanovii. L. monocytogenes isolates (68) were tested by disc diffusion assay for their resistance to 15 drugs currently used in veterinary and human therapy. All isolates displayed resistance to at least one antibiotic. Excluding nalidixic acid, to which most strains are intrinsically resistant, 37.2% of strains in 1993 and 96.0% in 2006 showed resistance to at least one antibiotic. Multi-resistance (resistance to two or more antibiotics) was less common in 1993 than in 2006 (18.6% and 84.0%, respectively; P < 0.001). The average number of antibiotics to which the strains were resistant was lower (P < 0.001) in 1993 (1.6) than in 2006 (4.2). An increase (P < 0.05) in the percentage of resistant strains was observed between 1993 and 2006 for six different drugs: gentamicin, streptomycin, neomycin, enrofloxacin, ciprofloxacin and furazolidone. In this research, the prevalence and the antibiotic susceptibility of L. monocytogenes in poultry samples from the same origin in North-Western Spain in the 1990s and the 2000s were compared for the first time. The increase in antibiotic resistance from 1993 to 2006 constitutes a matter for concern and confirms a general worldwide pattern among many groups of bacteria. The high prevalence of L. monocytogenes in poultry suggests the crucial role of food handlers in preventing listeriosis in consumers. Reducing the prevalence of L. monocytogenes in poultry and preventing the emergence or selection of antibiotic-resistant strains are also highlighted.

Antibiotic resistance of subgingival species in chronic periodontitis patients

The increasing rate of resistance of microorganisms to penicillin and other antibiotics has generated concern among health authorities in Latin America. The present investigation determined the in vitro susceptibility of Porphyromonas gingivalis, Fusobacterium nucleatum, black-pigmented Prevotella spp. and Aggregatibacter actinomycetemcomitans to metronidazole, amoxicillin, amoxicillin/clavulanic acid, clindamycin and moxifloxacin in patients with chronic periodontitis. Subgingival plaque samples from patients with periodontitis were collected and cultured on selective and nonselective culture media. The antimicrobial susceptibility of periodontopathogenic isolates was studied in chronic periodontitis patients in Colombia. Metronidazole, amoxicillin, amoxicillin/clavulanic acid, clindamycin and moxifloxacin were tested on all bacterial isolates and the percentage of resistant strains was calculated. Of the 150 bacteria identified, 51 were P. gingivalis, 45 were black-pigmented Prevotella spp., 36 were F. nucleatum and 18 were A. actinomycetemcomitans. All the isolates were sensitive to amoxicillin/clavulanic acid and to moxifloxacin, but exhibited variable susceptibility patterns to the other antimicrobial agents tested. The results of the present study suggest that periodontal microorganisms in patients with chronic periodontitis can be resistant to the antimicrobial agents commonly used in anti-infective periodontal therapy. We suggest that the indiscriminate use of antimicrobials could result in the appearance of more highly antibiotic-resistant strains of bacteria associated with periodontal diseases in our population compared with the populations of other countries.

Bacterial communities of two contrasting soils reacted differently to lincomycin treatment

The antibiotic lincomycin an anthropogenic pollutant – may change the bacterial diversity and resistance of soil communities by increasing selection pressure in favour of resistant phenotypes. In a laboratory experiment, two forest soils of contrasting characteristics in both pH and clay content were examined for changes in their bacterial communities after lincomycin treatment. The two soils were incubated in beakers and treated with three dosages of lincomycin. Changes in bacterial community were assessed by (i) cultivation of bacteria on two different media, and percentage of resistant colonies at two lincomycin concentrations; (ii) analysis of putative actinomycete isolates for antibiotic activities and resistance; (iii) T-RFLP diversity profiles of the 16S rDNA and homologues of the resistance gene lmrB; and (iv) cloning-sequencing of PCR amplicons of both 16S rDNA and lmrB homologues. In cultivation, no increase in percentage of resistant strains in lincomycin-treated versus untreated soils was detected. Similar numbers of bacterial cells were determined by DAPI staining in the two, treated or untreated, soils; but significantly higher numbers of both total bacteria and actinomycetes were cultivated from all treatments of the high pH soil. Significantly higher numbers of antibiotic-producing bacteria as well as resistant bacteria were found in the low pH soil. Significant shifts in bacterial diversity (16S rRNA gene) were demonstrated after lincomycin treatment for the high pH soil, while the low pH soil with a higher percentage of actinomycetes and higher diversity of the lmrB homologue genes did not change after treatment. Finally, sequencing of 157 new clones of lmrB homologues revealed that the antibiotic treatment significantly influenced selection for lmrB homologues in both soils.

A laboratory method to evaluate the sensitivity of Colletotrichum musae to postharvest fungicides

Introduction. Ce protocole vise a detecter et evaluer des variations de sensibilite dans des populations de Colletotrichum musae vis-a-vis des fongicides actuellement utilises pour le controle des maladies de conservation des bananes. Le principe, les principaux avantages, le materiel vegetal de depart, le temps necessaire et les resultats attendus de la methode sont presentes. Materiel et methodes. Le materiel de laboratoire necessaire, et le detail des douze etapes du protocole realise pour l'echantillonnage des bananes et le developpement des lesions dues a l'anthracnose, la preparation des boites de milieu gelose (agar), les isolements monospores, les tests de germination et l'analyse des donnees sont decrits. De possibles problemes sont evoques. Nous obtenons (a) pour les produits antimitotiques, le pourcentage de souches resistantes dans la population analysee ; (b) pour des fongicides inhibiteurs de la biosynthese des sterols (SBI), la variation et la distribution de la sensibilite des isolats dans la population analysee en fonction de la reduction de leur croissance radiale, imputable au fongicide. (Resume d'auteur)

Antimicrobial profiles of periodontal pathogens isolated from periodontitis patients in the Netherlands and Spain

Antimicrobial resistance of periodontal pathogens towards currently used antibiotics in periodontics has been investigated in a previous study. Microbial resistance in the periodontal microflora was more frequently observed in Spanish patients in comparison with Dutch patients. The aim of the present study was to compare antimicrobial susceptibility profiles of five periodontal bacteria isolated from periodontitis patients in Spain and in The Netherlands. Subgingival plaque samples from adult patients with periodontitis were collected and cultured on selective and non-selective plates. Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum and Micromonas micros were isolated and used for minimal inhibitory concentration tests using the Epsilometer (E-test) technique. Eight different antibiotics were tested on all bacterial isolates. MIC50 and MIC90 values for each antibiotic and each species were determined and the percentage of resistant strains was calculated. Significantly higher MIC values were noted in Spanish strains of F. nucleatum for penicillin, ciprofloxacin, of P. intermedia for penicillin, amoxicillin and tetracycline, of M. micros for tetracycline, amoxicillin and azithromycin, and of P. gingivalis for tetracycline and ciprofloxacin. Based on breakpoint concentrations, a higher number of resistant strains in Spain were found in F. nucleatum for penicillin, amoxicillin and metronidazole, in Prevotella intermedia for tetracycline and amoxicillin, and in A. actinomycetemcomitans for amoxicillin and azithromycin. Resistance of P. gingivalis strains was not observed for any of the antibiotics tested both in Spain and The Netherlands. Differences exist in the susceptibility profiles of periodontal pathogens isolated from periodontitis patients in Spain and in The Netherlands. This implicates that antibiotic susceptibility testing is necessary to determine efficacy of antimicrobial agents. Also, clinical studies with antibiotics should take these differences into account. The information from the present study indicates that it may not be possible to develop uniform protocols for usage of antibiotics in the treatment of severe periodontitis in the European Union.

Antimicrobial resistance in Campylobacter from broilers: association with production type and antimicrobial use

The isolation and antimicrobial resistance of Campylobacter jejuni and Campylobacter coli strains from broilers arriving in French slaughterhouses, were analysed according to production types (i.e. standard, export or free-range) and antimicrobial (i.e. coccidiostats, growth promoters or therapeutic agents) administration in flocks. Prevalence was 56.6% in standard, 51.3% in export and 80.0% in free-range broilers. Three hundred and ninety-three strains were identified. Two-thirds of the strains belonged to the species C. jejuni. The others were C. coli. Antimicrobial susceptibility testing was carried out for ampicillin, nalidixic acid, enrofloxacin, tetracycline, erythromycin and gentamicin according to a dilution method. The percentages of resistant strains were, 23, 25, 17, 57, 0.3 and 0% for C. jejuni and 29, 43, 40, 70, 31 and 0% for C. coli. Statistical analysis revealed significant difference in distribution of C. jejuni and C. coli and antimicrobial resistance according to production type or antimicrobial administration.

Antimicrobial resistance in Campylobacter from broilers: association with production type and antimicrobial use

The isolation and antimicrobial resistance of Campylobacter jejuni and Campylobacter coli strains from broilers arriving in French slaughterhouses, were analysed according to production types (i.e. standard, export or free-range) and antimicrobial (i.e. coccidiostats, growth promoters or therapeutic agents) administration in flocks. Prevalence was 56.6% in standard, 51.3% in export and 80.0% in free-range broilers. Three hundred and ninety-three strains were identified. Two-thirds of the strains belonged to the species C. jejuni . The others were C. coli . Antimicrobial susceptibility testing was carried out for ampicillin, nalidixic acid, enrofloxacin, tetracycline, erythromycin and gentamicin according to a dilution method. The percentages of resistant strains were, 23, 25, 17, 57, 0.3 and 0% for C. jejuni and 29, 43, 40, 70, 31 and 0% for C. coli. Statistical analysis revealed significant difference in distribution of C. jejuni and C. coli and antimicrobial resistance according to production type or antimicrobial administration.