MICs Of Ampicillin Research Articles

Polymorphism in ftsI gene and -lactam susceptibility in Portuguese Haemophilus influenzae strains: clonal dissemination of -lactamase-positive isolates with decreased susceptibility to amoxicillin/clavulanic acid

The aim of this study was to characterize ampicillin resistance mechanisms in clinical isolates of Haemophilus influenzae from Portugal. Association between specific patterns of amino acid substitutions in penicillin-binding protein 3 (PBP3) (with or without β-lactamase production) and β-lactam susceptibility as well as genetic relatedness among isolates were investigated. Two-hundred and forty non-consecutive H. influenzae isolates chosen according to their different ampicillin MICs [101 β-lactamase-non-producing ampicillin-resistant (BLNAR) isolates, 80 β-lactamase-producing ampicillin-resistant (BLPAR) isolates and 59 β-lactamase-non-producing ampicillin-susceptible (BLNAS) isolates] were analysed. The β-lactamase-encoding bla(TEM-1) gene was detected by PCR. The ftsI gene encoding PBP3 was sequenced. Genetic relatedness among isolates was examined by PFGE. Of the 240 H. influenzae isolates, 141 had mutations in the transpeptidase domain of the ftsI gene, including most BLNAR strains (94/101, 93.1%) and a high percentage of BLPAR strains (47/80, 58.8%). As previously reported, the latter have been described as β-lactamase-positive amoxicillin/clavulanic acid resistant (BLPACR). The most common amino acid substitutions were identified near the KTG motif: N526K (136/141, 96.5%), V547I (124/141, 87.9%) and N569S (121/141, 85.8%). The 141 strains were divided into 31 ftsI mutation patterns and included six groups (I, IIa, IIb, IIc, IId and III-like). BLNAR strains were genetically diverse but close genetic relationships were demonstrated among BLPACR strains. This study shows that the non-enzymatic mechanism of resistance to β-lactams is widespread among H. influenzae isolates in Portugal. Clonal dissemination of BLPACR strains showing high resistance to ampicillin and reduced susceptibility to amoxicillin/clavulanic acid was documented.

Performance of the Oxoid M.I.C.EvaluatorTM Strips compared with the Etest(R) assay and BSAC agar dilution

ObjectivesThe Oxoid M.I.C.Evaluator™ (M.I.C.E™; Thermo Fisher Scientific) comprises an antibiotic gradient on a plastic support. We compared its performance with Etest®—a similar product—using BSAC agar dilution as a reference.MethodsParallel MIC tests were performed by M.I.C.Evaluator, Etest and agar dilution on Iso-Sensitest™ agar. In total, 9354 organism/strip combinations were tested by each method, using 1017 bacteria representing clinically important fastidious and non-fastidious species.ResultsEssential agreement of strip MIC values (±1 doubling dilution) with the agar dilution reference, with off-scale results excluded, was 89.9% for M.I.C.Evaluator versus 89.5% for Etest (P > 0.05). These proportions were similar, at 89.5% and 89.3% (P > 0.05), respectively, if off-scale values were counted as agreeing if they could agree (e.g. a strip MIC >32 mg/L and an agar dilution MIC of 128 mg/L). For both strips, agreement with agar dilution was best for non-fastidious genera, Moraxella, Listeria, Pasteurella and Campylobacter spp. and weaker for streptococci, anaerobes, Neisseria spp. and, especially, Haemophilus influenzae. Many ‘disagreements’, especially for H. influenzae, concerned organisms unequivocally resistant by all methods (e.g. ampicillin MIC 256 mg/L by agar dilution, 16 or 32 mg/L by both strips); nevertheless both strips underestimated imipenem MICs for Proteus. There was no difference between the two strip types in the proportion of agreements with agar dilution (P > 0.05); nevertheless their results agreed better with each other than with agar dilution (P < 0.01).ConclusionsThe M.I.C.Evaluator performed almost identically to the Etest, giving good agreement with BSAC agar dilution.

Mutational Analysis of VIM-2 Reveals an Essential Determinant for Metallo-β-Lactamase Stability and Folding

Metallo-beta-lactamase (MBL)-producing bacteria are emerging worldwide and represent a formidable threat to the efficacy of relevant beta-lactams, including carbapenems, expanded-spectrum cephalosporins, and beta-lactamase inactivator/beta-lactam combinations. VIM-2 is currently the most widespread MBL and represents a primary target for MBL inhibitor research, the clinical need for which is expected to further increase in the future. Using a saturation mutagenesis approach, we probed the importance of four residues (Phe-61, Ala-64, Tyr-67, and Trp-87) located close to the VIM-2 active site and putatively relevant to the enzyme activity based on structural knowledge of the enzyme and on structure-activity relationships of the subclass B1 MBLs. The ampicillin MIC values shown by the various mutants were affected very differently depending on the randomized amino acid position. Position 64 appeared to be rather tolerant to substitution, and kinetic studies showed that the A64W mutation did not significantly affect substrate hydrolysis or binding, representing an important difference from IMP-type enzymes. Phe-61 and Tyr-67 could be replaced with several amino acids without the ampicillin MIC being significantly affected, but in contrast, Trp-87 was found to be critical for ampicillin resistance. Further kinetic and biochemical analyses of W87A and W87F variants showed that this residue is apparently important for the structure and proper folding of the enzyme but, surprisingly, not for its catalytic activity. These data support the critical role of residue 87 in the stability and folding of VIM-2 and might have strong implications for MBL inhibitor design, as this residue would represent an ideal target for interaction with small molecules.

Intra- and Interlaboratory Performances of Two Commercial Antimicrobial Susceptibility Testing Methods for Bifidobacteria and Nonenterococcal Lactic Acid Bacteria

In a small-scale harmonization study involving nine laboratories in eight European countries, the intra- and interlaboratory performances of two commercially available systems, i.e., the VetMIC microplate system and Etest, for antimicrobial susceptibility testing of nonenterococcal lactic acid bacteria (NELAB) and bifidobacteria were analyzed. In addition, one laboratory also performed standard broth microdilution as a reference method. MICs of tetracycline, erythromycin, ampicillin, gentamicin, clindamycin, and streptomycin for the type strains of 25 species of NELAB and bifidobacteria and MICs of vancomycin for a selection of relevant taxa were determined. The previously described lactic acid bacterium susceptibility test medium (LSM) and related mixed-medium formulations, all including Iso-Sensitest broth as a basic component, were used as test media. The overall agreement of median MIC ranges +/- 1 log(2) dilution determined by the VetMIC and Etest methods with the median MICs determined by the reference method was very good for tetracycline, ampicillin, and streptomycin (92.3 to 100%) but low for erythromycin (19.5 to 30.7%) and clindamycin (50.0 to 80.8%). There was a consensus among the participating laboratories that VetMIC was preferred over Etest because of its lower cost, better growth support, and more uniform criteria for MIC end point reading. With the range for acceptable intralaboratory reproducibility being defined as the median MIC +/- 1 log(2) dilution, VetMIC results (with 69.2% of all data sets in the acceptable range) were shown to display greater reproducibility than Etest results (with 58.8% of all data sets in the acceptable range). Also at the interlaboratory level, the proportion of MIC values obtained with VetMIC that belonged to the complete agreement category (60.0%) was higher than the proportion of such values obtained with Etest (47.0%), which indicates a higher degree of interlaboratory reproducibility for the former method. Apart from some agent-specific effects, the majority of VetMIC and Etest replicate data sets were situated within a 1- to 2-log(2) dilution range, suggesting that the two methods can be considered to be equivalent for recognizing resistance phenotypes. This multicenter study has further validated the standard use of LSM and related mixed-medium formulations with commercially available systems and formed the basis for the ongoing development of the ISO 10932/IDF 223 standard for susceptibility testing of NELAB and bifidobacteria.

Imported Ciprofloxacin-ResistantNeisseria meningitidis

Imported Ciprofloxacin-Resistant<i>Neisseria meningitidis</i>

Mutant ftsI genes in the emergence of penicillin-binding proteinmediated β-lactam resistance in Haemophilus influenzae in Norway

The most important mechanism for beta-lactam resistance in beta-lactamase-negative ampicillin-resistant (BLNAR) isolates of Haemophilus influenzae is the alteration of penicillin-binding protein 3 (PBP3) as a result of ftsI gene mutations. The present study aimed to map PBP3 alterations and to determine the correlation to beta-lactam resistance in respiratory tract isolates of H. influenzae in Norway, as well as assess the contribution of clonal spread to the emergence of PBP3-mediated resistance. Twenty-three beta-lactamase negative respiratory tract isolates with resistance to penicillins and 23 susceptible control isolates were examined by determination of beta-lactam MICs, ftsI sequencing and molecular typing by pulsed-field gel electrophoresis (PFGE). Ampicillin MIC ranges in the resistant group and the control group were 1-2 mg/L and 0.125-0.5 mg/L, respectively. All isolates in the resistant group had the PBP3 substitution Asn526-->Lys and were thus categorized as group II low-BLNAR. No control isolate met the genetic BLNAR (gBLNAR) criteria. The PBP3 substitution patterns corresponded well to those observed in previous European studies. Eighty-three percent (19/23) of the resistant isolates belonged to two clones, demonstrating the capability of low-BLNAR strains of clonal dissemination. Combined analysis of ftsI DNA sequences and PFGE patterns revealed distinctly different ftsI alleles in genetically indistinguishable isolates and identical copies of the same ftsI allele in unrelated isolates. A possible explanation of this observation is the recombinational exchange of ftsI alleles. This phenomenon, as well as the possibility of endemic European gBLNAR strains, should be further investigated.

Evolution of antimicrobial resistance in enteroaggregative Escherichia coli and enterotoxigenic Escherichia coli causing traveller's diarrhoea

Enteroaggregative Escherichia coli (EAEC) and enterotoxigenic E. coli (ETEC) are among the most frequent microorganisms causing traveller's diarrhoea. The aim of this study was to investigate the evolution of antimicrobial resistance in EAEC and ETEC causing diarrhoea in patients who had travelled to different developing countries, comparing two periods of time, 1994-97 and 2001-04. Overall, 134 EAEC and 190 ETEC clinical isolates were studied. The MICs of ampicillin, chloramphenicol, nalidixic acid, tetracycline, trimethoprim/sulfamethoxazole, ciprofloxacin and amoxicillin/clavulanic acid were determined by the Etest method. Detection of mutations in the quinolone-resistance determining region of the gyrA and parC genes was performed by PCR and DNA sequencing. When antimicrobial resistance in EAEC and ETEC isolates was compared between the two periods of time, a statistically significant increase in resistance (P < 0.01) was observed in EAEC for chloramphenicol and amoxicillin/clavulanic acid, whereas in ETEC it was for trimethoprim/sulfamethoxazole, nalidixic acid, ciprofloxacin and amoxicillin/clavulanic acid. Mutations in the gyrA gene were found in all nalidixic acid-resistant isolates, whereas mutation(s) in both gyrA and parC genes were found in the ciprofloxacin-resistant isolates. The high percentage of resistance to quinolones in ETEC and EAEC isolated from travellers to North Africa and India is a matter for concern. These agents should therefore be used with caution in patients with traveller's diarrhoea returning from these geographical areas.

Canadian β-lactamase–negative Haemophilus influenzae isolates showing decreased susceptibility toward ampicillin have significant penicillin binding protein 3 mutations

Nineteen β-lactamase–negative ampicillin-resistant (BLNAR) and 2 β-lactamase–positive amoxicillin-clavulanic acid–resistant Canadian Haemophilus influenzae strains were characterized. All 21 isolates were found to have the N526K mutations in their ftsI genes, and their ampicillin MIC 50 values were 4–8 times that of β-lactamase–negative ampicillin-susceptible strains. The difficulty in detection of BLNAR strains was discussed.

1‐methyl malate from Berberis integerrima fruits enhances the antibacterial activity of ampicillin against Staphylococcus aureus

The enhancement of the antibacterial activity of ampicillin by different extracts of Berberis integerrima fruits was evaluated against Staphylococcus aureus. Disk diffusion and agar dilution methods were used to determine the antibacterial activity of ampicillin in the absence and presence of different plant extracts or various fractions eluted by column chromatography. A clinical isolate of S. aureus was used as a test strain. The active component of B. integerrima fruits involved in the enhancement of ampicillin activity was purified and identified as 1-methyl malate using different spectroscopic methods. Both the ethanol extract of B. integerrima fruits and 1-methyl malate enhanced the antibacterial activity of ampicillin. The total extract as well as 1-methyl malate increased the antibacterial activity of ampicillin against the test strain. The potency of ampicillin against the test strain was increased 64-fold when tested with a sub-toxic concentration of total extract of B. integerrima fruits. Also, 1-methyl malate increased the bactericidal activity of ampicillin. In the presence of 2 mg/mL of 1-methyl malate the MIC of ampicillin for S. aureus decreased from 128 to 1 microg/mL (128-fold).

Highly Susceptible Strains of Typhoid Bacilli Encountered in Jamaica

Background: Unlike reports of multidrug-resistant Salmonella enterica serovar typhi (S. typhi) in countries around the world, strains encountered in Jamaica have been uniformly susceptible to all the anti-typhoid drugs and also to other antibiotics by disc method. We have been maintaining these isolates on Dorset-egg medium over the years. In this report, we examine the MICs of 4 front-line antibiotics against 41 unduplicated isolates(one from a patient) encountered in consecutive 17 years between 1984 and 2000 at the University Hospital in Kingston, Jamaica. Methods: The MICs were determined by E test(AB Biodisk, Solna, Sweden) using E. coli ATCC 25922 as control. Manufacturers’ instructions in regard to media, inoculum density and incubation parameters were followed strictly. Our observation of extremely low MICs (see results below) made us to do the tests repeatedly and read the results independently by each of us (NCB and OH) and repeat again if we differed in reading by more than one E test dilution. Results: The MICs( g/ml) of the four antibiotics were Chloramphenicol MIC range 2—4, MIC50 3 and MIC90 3; Ampicillin MIC range 0.125—1, MIC50 0.25 and MIC90 0.5; Trimethprim/Sulpha MIC range 0.023—0.064, MIC50 0.032 and MIC90 0.047; Ceftriaxone MIC range 0.023—0.047, MIC50 0.032 and MIC90 0.047. All isolates were susceptible. MICs were extremely low, fell in a narrow range and far below the standard susceptible(CLSI) Breakpoint MICs of the antibiotics. We have not seen any report of such a highly susceptible strains of typhoid bacilli from anywhere in the world. Conclusion: Considering the growing increase of multidrug-resistant typhoid in countries around the world and reports of isolation of strains with MICs of front-line antibiotics of more than 256 g/ml(Hirose K et al Antimicrob Ag Chemother 45:956—958,2001), the highly susceptible nature of strains encountered in Jamaica is noteworthy. These unique strains which we call ‘Jamaica strains’ have been persisting in this island country throughout the years.

A comparison of Etest(R), M.I.C.EvaluatorTM strips and CLSI broth microdilution for determining -lactam antimicrobial susceptibility in Haemophilus influenzae

β-Lactamase-positive ampicillin-resistant (BLPAR) strains of Haemophilus influenzae generally have relatively high ampicillin MICs, but remain susceptible to cephalosporins and co-amoxiclav. β-Lactamase-negative ampicillin-resistant (BLNAR) strains, on the other hand, have relatively low ampicillin MICs and low levels of resistance or decreased susceptibility to cephalosporins and co-amoxiclav due to altered PBP3. Some strains have both β-lactamase and altered PBP3: these β-lactamase-positive co-amoxiclav-resistant (BLPACR) strains have relatively high ampicillin MICs due to the β-lactamase and low MICs of other β-lactam antibiotics associated with altered PBP3.

In vitro activity of cefditoren and other antimicrobial agents against 288 Streptococcus pneumoniae and 220 Haemophilus influenzae clinical strains isolated in Zaragoza, Spain

In vitro cefditoren antimicrobial activity was tested against 288 Streptococcus pneumoniae and 220 Haemophilus influenzae clinical strains isolated in our hospital from January 2005 to May 2006 by agar dilution and broth microdilution method, respectively. MICs were also determined for 13 and 10 comparison drugs, respectively. The pneumococci tested comprised 113 (39.2%) penicillin susceptible, 91 (31.6%) penicillin intermediate, and 84 (29.2%) penicillin resistant. Cefditoren was the most active drug on the basis of the MICs (MIC 90 = 0.5 μg/mL), followed by ceftriaxone and levofloxacin (MIC 90 = 1 μg/mL). Cefditoren MICs ranged from 0.25 to 1 μg/mL for ceftriaxone-resistant isolates, with a modal MIC of 0.5 μg/mL and an MIC 90 of 1.0 μg/mL. No S. pneumoniae isolates evaluated in this study showed MICs to cefditoren higher than 1 μg/mL (MIC range, ≤0.015 to 1 μg/mL). Against penicillin-resistant pneumococci, the rank order of intrinsic activity (MIC 90, μg/mL) was cefditoren (0.5) < ceftriaxone (2.0) = cefotaxime (2.0) < amoxicillin/clavulanate (8.0) = amoxicillin (8.0) = cefuroxime (8.0). Among the 220 strains of H. influenzae, 42 (19.09%) produced a β-lactamase (Hi β+) and 3 (1.1%) were β-lactamase (Hi β-) negative but have reduced susceptibility to ampicillin (BLNAR). The most active drugs on the basis of MICs were cefditoren and levofloxacin, showing MIC 50 and MIC 90 values of 0.015/0.06 μg/mL. Cefditoren at concentration of 0.06 μg/mL inhibited all 3 BLNAR (ampicillin MICs >4 μg/mL). Against H. influenzae (Hi β+), the rank order of intrinsic activity (MIC 90, μg/mL) was cefditoren (0.03) < cefixime (0.06) < ceftriaxone (0.12) = cefotaxime (0.12) < cefuroxime (1.0) < amoxicillin/clavulanate (2.0) < ampicillin (>8.0).

Polymorphism in pbp5 Gene Detected in Clinical Enterococcus faecium Strains with Different Ampicillin MICs from a Tunisian Hospital

The polymorphism in pbp5 gene was investigated in nine unrelated clinical gentamicin-resistant Enterococcus faecium strains with different minimal-inhibitory-concentration values for ampicillin (six ampicillin-resistant and three ampicillin-susceptible). Five alleles were detected when the pbp5 C-terminal region was analysed, two of them in the ampicillin-susceptible strains. Two of our high-ampicillin-resistant strains showed a new allele characterised by the Thr416Ala and Val462Ala substitutions. Two different alleles were identified when the pbp5 N-terminal region was studied; one of them in the unique strain (E. faecium 83) that presented very low ampicillin MIC (<0.125 μg/ml) and a nucleotidic mutation implicating a stop codon at 451 position. RT-PCR experiments carried out on five E. faecium strains belonging to each of the different pbp5 alleles (including E. faecium 83) gave positive results indicating the expression of this gene. Specific mutations in pbp5 gene could be responsible of the high MIC values of some of the E. faecium strains.

Antimicrobial Susceptibility Profile of Streptococcus pseudopneumoniae Isolated from Sputum

Streptococcus pseudopneumoniae is a recently described member of the Streptococcus mitis/oralis group of viridans streptococci that shares some characteristics with Streptococcus pneumoniae (1). Key characteristics of S. pseudopneumoniae are the absence of pneumococcal capsule, insolubility in bile, resistance or indeterminate susceptibility to optochin when incubated in 5% CO2 but susceptibility to optochin when incubated in ambient air, and positive reactions in DNA probe hybridization and antigen detection tests (1, 3). The clinical relevance of S. pseudopneumoniae has not yet been established, although it may be associated with chronic obstructive pulmonary disease (3). As yet, the antibiotic susceptibility profile of S. pseudopneumoniae has not been reported in detail. The aim of this study was to determine the antibiotic susceptibility profile of a large number of S. pseudopneumoniae isolates recovered from clinical specimens. Ninety-five isolates of S. pseudopneumoniae collected between 2000 and 2007 were studied. All isolates had been recovered as the predominant organism from good-quality sputum specimens containing >25 leukocytes and ≤10 squamous epithelial cells per 100× field. The isolates were identified on the basis of phenotypic characteristics as previously described (1, 3). MICs were determined by broth microdilution with the MicroScan Micro STREP plus 1 system (Dade Behring, West Sacramento, CA). The MICs of penicillin, ampicillin, ceftriaxone, cefotaxime, cefepime, meropenem, chloramphenicol, clindamycin, erythromycin, azithromycin, tetracycline, vancomycin, gatifloxacin, levofloxacin, and trimethoprim-sulfamethoxazole were determined. Strains for which the MICs were greater than the highest dilution included on the MicroScan panel were retested with the Etest (AB Biodisk, Solna, Sweden) to determine the precise MIC. Susceptibility breakpoints were based on CLSI guidelines (2). Strains showing resistance to erythromycin but susceptibility to clindamycin were further tested to determine the presence of macrolide-lincosamide-streptogramin B resistance (MLS phenotype). Discs containing erythromycin (15 μg) and clindamycin (2 μg) were placed 20 mm apart on the plate. After incubation, the plates were examined for flattening of the clindamycin zone, which is indicative of the phenotype. The MICs of the 15 antibiotics are shown in Table ​Table1.1. No isolate was resistant to any β-lactam agent, although about one-third showed reduced susceptibility to penicillin and ampicillin. About one-third of the isolates were resistant to macrolides, almost half were resistant to tetracycline, and 71% were resistant to tetracycline and/or macrolide antibiotics. Reduced susceptibility to the macrolide antibiotics only (M phenotype) occurred in seven isolates, with an additional isolate being resistant to clindamycin (intrinsic MLS resistance). Inducible MLS resistance was noted in 3 of 28 erythromycin-resistant, clindamycin-susceptible isolates. In each case, the MIC was within a 1-dilution difference from susceptible. All azithromycin-resistant isolates were resistant to erythromycin. TABLE 1. In vitro activities of antimicrobial agents against 95 isolates of S. pseudopneumoniae One limitation of our study is that all of the isolates were collected from respiratory samples from patients attending a tertiary care center in one geographical area of New Zealand. As such, they may not be representative of the isolates found in the wider community or other regions of the world. Further studies are needed in other geographic regions, and possibly with other sample types, in order to better clarify the antibiotic susceptibility profile of S. pseudopneumoniae.

Low β-Lactamase-Negative Ampicillin-Resistant Haemophilus influenzae Strains Are Best Detected by Testing Amoxicillin Susceptibility by the Broth Microdilution Method

Ampicillin resistance in Haemophilus influenzae due to alterations in penicillin-binding proteins (beta-lactamase negative ampicillin resistant [BLNAR]) is acquiring increasing clinical and epidemiological importance. BLNAR strains with low ampicillin MICs (0.5 to 4 microg/ml) represent the majority of this population in Europe and the United States, but separating them from susceptible isolates is challenging. To investigate the best method to identify low-BLNAR strains, we studied the antibiotic susceptibilities of 94 clinical isolates of H. influenzae by microdilution, Etest, and disk diffusion: 25 had no resistance mechanisms (gBLNAS), 34 had mutations in the ftsI gene only (gBLNAR), 20 were beta-lactamase producers only (gBLPAR), and 15 showed beta-lactamase production and mutations in the ftsI gene (gBLPACR). By current CLSI breakpoints, most gBLNAR isolates were ampicillin susceptible by microdilution (76.5%) or by Etest (88.2%). Most gBLNAR strains (79.4%) were nonsusceptible to amoxicillin (the most widely used community antibiotic in the United States and Europe) when tested by microdilution. By Etest, 15% of beta-lactamase-positive isolates were nonresistant to ampicillin or amoxicillin. The poorest agreement between Etest and microdilution results was for the gBLPAR isolates (25% for ampicillin, 15% for amoxicillin, and 10% for cefaclor). Low-strength disks of ampicillin and amoxicillin-clavulanic acid poorly identified low-BLNAR isolates and are not recommended as a screening method. We suggest new amoxicillin breakpoints for BLNAR isolates as follows: susceptible, MIC < or = 0.5 microg/ml (no resistance mechanisms; pharmacokinetic/pharmacodynamic [PK/PD] data favorable); intermediate, MICs = 1 to 2 microg/ml (resistance mechanisms present but PK/PD data favorable), and resistant, MICs > or = 4 microg/ml (resistance mechanisms present and PK/PD data unfavorable).

Enterococcus faecium isolated from bone marrow transplant patients in Tunisia: High prevalence of antimicrobial resistance and low pathogenic power

Objectives Investigation of the occurrence and antibiotic susceptibility of Enterococcus faecium isolates, collected during four years from neutropenic patients at the Tunisian bone marrow transplantation centre. Materials and methods E. faecium strains were identified by conventional methods and by the Api20 Strep (Bio-Mérieux, France). Antibiotic susceptibility was determined by the disk diffusion method on Mueller-Hinton agar and interpreted as recommended by CA-SFM. MICs of ampicillin, vancomycin, and teicoplanin were determined by E-test method. Results Two hundred and thirty five E. faecium isolates were recovered from stool cultures or rectal swabs (229), throat (three), urine (two), and pus of wound (one). None was responsible for bacteraemia. Ampicillin resistance, without production of β-lactamase, was observed in 43.8% of isolates. All the isolates were susceptible to glycopeptides. High rates of resistance were observed: high-level resistance (HLR) to gentamicin (33.6%), HLR to kanamycin (55.7%), HLR to streptomycin (47.6%), erythromycin (86.4%), ciprofloxacin (78.7%), rifampicin (85%), and tetracycline (43%). Strains with HLR to gentamicin were significantly more resistant to ampicillin and streptomycin. Multiple drug resistance was observed in most isolates. Conclusion These findings demonstrated the low pathogenic power of E. faecium in our patients, and the high frequencies of resistance to ampicillin and aminoglycosides. In the absence of glycopeptide-resistance, vancomycin remains an alternative treatment against multidrug resistant strains.

本邦で認知度が低い&lt;I&gt;Clostndium&lt;/I&gt;の感染症材料からの分離状況と薬剤感受性

Cigar-shaped clostridia such as Clostridium clostridioforme and Clostridium symbiosum have been found in serious infections such as bacteremia. In Japan, however, these strains are unrecognized as clinically significant because they are overlooked as unidentified gram-negative rods. We isolated 60 strains of cigar-shaped Clostridium spp. from 48 clinical specimens treated at our laboratory from November 2004 to September 2006. Of these, 19 (39.6%) were primary infections and 29 (60.4%) postsurgical. Primary infections included infected decubitus ulcer (7), peritonitis, intra abdominal abscess, sepsis (2 cases in each group), pyometra, Bartholin's gland abscess, and Fournier's gangrene (1 case in each group). Secondary infections included 28 cases of surgical site infection and 1 case of pyothorax. CRP in 30 cases (62.5%) exeeded 10 mg/dL. In 26 (54.2%), WBC exceeded 12,000/microL. The 60 isolated strains were as follows by 16S rRNA sequencing: Clostridium hathewayi (26.7%), C. clostridioforme (16.7%), Clostridium bolteae (18.3%), Clostridium citroniae (10%), Clostridium aldenense (8.3%), and Clostridium symbiosum (20%). In antimicrobial susceptibility, strains of C. hathe-wayi showed relatively higher MIC for cefotaxime (MIC50; 64 microg/mL, MIC90; 128 microg/mL). Three strains of C. bolteae were beta-lactamase-producing and their MICs for ampicillin exceeded 128 microg/mL.

Ampicillin-Resistant Non-β-Lactamase-Producing Haemophilus influenzae in Spain: Recent Emergence of Clonal Isolates with Increased Resistance to Cefotaxime and Cefixime

The sequence of the ftsI gene encoding the transpeptidase domain of penicillin-binding protein 3 (PBP 3) was determined for 354 nonconsecutive Haemophilus influenzae isolates from Spain; 17.8% of them were ampicillin susceptible, 56% were beta-lactamase nonproducing ampicillin resistant (BLNAR), 15.8% were beta-lactamase producers and ampicillin resistant, and 10.4% displayed both resistance mechanisms. The ftsI gene sequences had 28 different mutation patterns and amino acid substitutions at 23 positions. Some 93.2% of the BLNAR strains had amino acid substitutions at the Lys-Thr-Gly (KTG) motif, the two most common being Asn526 to Lys (83.9%) and Arg517 to His (9.3%). Amino acid substitutions at positions 377, 385, and 389, which conferred cefotaxime and cefixime MICs 10 to 60 times higher than those of susceptible strains, were found for the first time in Europe. In 72 isolates for which the repressor acrR gene of the AcrAB efflux pump was sequenced, numerous amino acid substitutions were found. Eight isolates with ampicillin MICs of 0.25 to 2 microg/ml showed changes that predicted the early termination of the acrR reading frame. Pulsed-field gel electrophoresis analysis demonstrated that most BLNAR strains were genetically diverse, although clonal dissemination was detected in a group of isolates presenting with increased resistance to cefotaxime and cefixime. Background antibiotic use at the community level revealed a marked trend toward increased amoxicillin-clavulanic acid consumption. BLNAR H. influenzae strains have arisen by vertical and horizontal spread and have evolved to adapt rapidly to the increased selective pressures posed by the use of oral penicillins and cephalosporins.

Prevalence of Campylobacter spp. in cattle in Finland and antimicrobial susceptibilities of bovine Campylobacter jejuni strains.

The study investigated the prevalence of Campylobacter spp. in Finnish cattle at slaughter and carcass contamination after slaughter. During the period January to December 2003, bovine rectal fecal samples (n=952) and carcass surface samples (n=948) from 12 out of 15 Finnish slaughterhouses were examined. In total, campylobacters were detected in 31.1% of fecal samples and in 3.5% of carcass surface samples. Campylobacter jejuni was isolated from 19.5%, Campylobacter coli from 2.2%, and presumptive Campylobacter hyointestinalis from 10.8% of fecal samples. Campylobacters were detected in 4.4% and 37.4% of the fecal samples examined both by direct culture and by enrichment (n=730), respectively, suggesting a low level of campylobacters in the intestinal content. A slightly increasing trend was observed in the overall prevalence of campylobacters towards the end of summer and autumn. Seventeen different serotypes were detected among the fecal C. jejuni isolates using a set of 25 commercial antisera for serotyping heat-stable antigens (Penner) of C. jejuni by passive hemagglutination. The predominant serotypes, Pen2 and Pen4-complex, were isolated from 52% of the fecal samples. Subtyping by pulsed-field gel electrophoresis (SmaI) yielded 56 and 20 subtypes out of 330 fecal and 70 carcass C. jejuni isolates, respectively. MICs of ampicillin, enrofloxacin, erythromycin, gentamicin, nalidixic acid, and oxytetracycline for 187 C. jejuni isolates were determined using a commercial broth microdilution method. Sixteen (9%) of the isolates were resistant to at least one of the antimicrobials tested. Resistance to nalidixic acid was most commonly detected (6%). No multiresistance was observed.

Antimicrobial Resistance in Campylobacter jejuni from Broilers and Broiler House Environments in Norway

Antimicrobial susceptibility in Campylobacter jejuni collected from the environment outside four broiler houses (n = 63) and from the environment inside these broiler houses (including broiler droppings) (n = 36) from May to September 2004 was studied and compared with isolates from Norwegian broilers analyzed within the frame of the Norwegian monitoring program of antimicrobial resistance in feed, food, and animals (NORM-VET) in 2004 (n = 75). The MICs of oxytetracycline, ampicillin, erythromycin, gentamicin, enrofloxacin, and nalidixic acid were obtained by the broth microdilution method VetMIC. The present study, which to our knowledge is the first Norwegian study on the occurrence of antimicrobial resistance in Campylobacter spp. from the environment of broiler houses, revealed a very low occurrence of antimicrobial resistance in C. jejuni from the broilers and broiler house environments studied. All isolates originating from the four broiler houses studied were susceptible to all the antimicrobial agents tested, except for one isolate from the outdoor environment (courtyard soil), which was resistant to oxytetracycline (MIC, 8 mg/liter). For the isolates from broilers (NORM-VET), low prevalences of resistance to oxytetracycline (1.3%) and ampicillin (4%) were observed. No quinolone resistance was observed. The results for the broiler isolates are in agreement with the earlier findings of a very low prevalence of resistance in Campylobacter from broilers in Norway, which reflects the low usage of antimicrobials in Norwegian broiler production. Furthermore, the present data are in accordance with antimicrobial susceptibility data for C. jejuni from domestically acquired human cases.