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At least 19 recordsLinked to original sources
PubMed2004

Genetic and molecular characterization of beta-lactamase-negative ampicillin-resistant Haemophilus influenzae with unusually high resistance to ampicillin.

Previous studies with beta-lactamase-negative, ampicillin-resistant (BLNAR) Haemophilus influenzae from Japan, France, and North America indicate that mutations in ftsI encoding PBP3 confer ampicillin MICs of 1 to 4 micro g/ml. Several BLNAR strains with ampicillin MICs of 4 to 16 micro g/ml recently isolated from North America were studied. Pulsed-field gel electrophoresis identified 12 unique BLNAR strains; sequencing of their ftsI transpeptidase domains identified 1 group I and 11 group II mutants, as designated previously (K. Ubukata, Y. Shibasaki, K. Yamamoto, N. Chiba, K. Hasegawa, Y. Takeuchi, K. Sunakawa, M. Inoue, and M. Konno, Antimicrob. Agents Chemother. 45:1693-1699, 2001). Geometric mean ampicillin MICs for several clinical isolates were 8 to 10.56 micro g/ml. Replacement of the ftsI gene in H. influenzae Rd with the intact ftsI from several clinical isolates resulted in integrants with typical BLNAR geometric mean ampicillin MICs of 1.7 to 2.2 micro g/ml. Cloning and purification of His-tagged PBP3 from three clinical BLNAR strains showed significantly reduced Bocillin binding compared to that of PBP3 from strain Rd. Based on these data, changes in PBP3 alone could not account for the high ampicillin MICs observed for these BLNAR isolates. In an effort to determine the presence of additional mechanism(s) of ampicillin resistance, sequencing of the transpeptidase regions of pbp1a, -1b, and -2 was performed. While numerous changes were observed compared to the sequences from Rd, no consistent pattern correlating with high-level ampicillin resistance was apparent. Additional analysis of the resistant BLNAR strains revealed frame shift insertions in acrR for all four high-level, ampicillin-resistant isolates. acrR was intact for all eight low-level ampicillin-resistant and four ampicillin-susceptible strains tested. A knockout of acrB made in one clinical isolate (initial mean ampicillin MIC of 10.3 micro g/ml) lowered the ampicillin MIC to 3.67 micro g/ml, typical for BLNAR strains. These studies illustrate that BLNAR strains with high ampicillin MICs exist that have combined resistance mechanisms in PBP3 and in the AcrAB efflux pump.

Ampicillin↗
PubMed1999

Near absence of vancomycin-resistant enterococci but high carriage rates of quinolone-resistant ampicillin-resistant enterococci among hospitalized patients and nonhospitalized individuals in Sweden.

Rates of colonization with enterococci with acquired resistance to vancomycin (vancomycin-resistant enterococci [VRE]) and ampicillin (ampicillin-resistant enterococci [ARE]) were determined by using fecal samples from 670 nonhospitalized individuals and 841 patients in 27 major hospitals. Of the hospitalized patients, 181 (21.5%) were carriers of ARE and 9 (1.1%) were carriers of VRE. In univariate analyses, length of hospital stay (odds ratio [OR], 4.6; 95% confidence interval [CI], 2.5 to 8.9) and antimicrobial therapy (OR, 4.7; 95% CI, 3.3 to 6.7) were associated with ARE colonization, as were prior treatment with penicillins (OR, 3.1; 95% CI, 1.8 to 5. 5), cephalosporins (OR, 2.9; 95% CI, 1.7 to 5.0), or quinolones (OR, 2.7; 95% CI, 1.5 to 4.7). In logistic regression analysis, antimicrobial therapy for at least 5 days was independently associated with ARE carriage (adjusted OR, 3.8; 95% CI, 2.6 to 5.4). Over 90% of the ARE isolates were fluoroquinolone resistant, whereas 14% of the ampicillin-susceptible Enterococcus faecium isolates were fluoroquinolone resistant. ARE carriage rates correlated with the use of fluoroquinolones (P = 0.04) but not with the use of ampicillin (P = 0.68) or cephalosporins (P = 0.40). All nine VRE isolates were E. faecium vanB and were found in one hospital. Seven of these isolates were related according to their types as determined by pulsed-field gel electrophoresis. Among the nonhospitalized individuals, the ARE carriage rate was lower (6%; P < 0.05), and only one person, who had recently returned from Africa, harbored VRE (E. faecium vanA). The absence of VRE colonization in nonhospitalized individuals reflects an epidemiological situation in Sweden radically different from that in countries in continental Europe where glycopeptides have been widely used for nonmedical purposes.

4-Quinolones↗
PubMed1982

Resistance types in Enterobacter cloacae. Occurrence and resistance to Ampicillin, Carbenicillin, Cephalothin and Mecillinam. Transfer of ampicillin Resistance.

An investigation of the resistance types in Enterobacter cloacae is presented. The frequency of the different resistance types was determined. The strains were divided into three groups according to sensitivity to penicillin derivatives. The ampicillin-carbenicillin-sensitive (A-s/Ca-s) group 1 comprised 20% of the E. cloacae strains received in this laboratory. The ampicillin resistant-carbenicillin-sensitive (A-r/Ca-s) group 2 comprised 38.5% of the strains and the A-r/Ca-r group 3 comprised 41.5% of the strains. Group 3 contained a high proportion of multi-resistant strains. The log 2 IC50 against ampicillin, carbenicillin, cephalothin and mecillinam was determined for 28 strains. The group 3 strains were more ampicillin-resistant than the group 2 ones. Group 1 and 2 did not differ as regards carbenicillin sensitivity. The cephalothin resistance increased from group 1 to group 2 and further on to group 3. Mecillinam sensitivity did not differ between the three groups. The ability to transfer ampicillin resistance was investigated in the 24 A-r strains. The 8 group 2 strains were not able to transfer resistance, while 9 of 16 strains in groups 3 could transfer A-resistance with frequencies ranging from 10-0.2 to 10-5.7. Resistance to sulphonamide, tetracycline and streptomycin was also transferred, often with the same frequency as the ampicillin resistance.

Amdinocillin↗
PubMed1984

Resistance types in Citrobacter freundii. Occurrence and resistance to ampicillin, carbenicillin, cephalothin and mecillinam. Transfer of ampicillin resistance.

The resistance types of Citrobacter freundii were investigated. The strains were divided into three groups according to susceptibility to penicillin derivatives. Group 1, comprising the ampicillin-carbenicillin sensitive strains (A-s/Ca-s), constituted 22%. Group 2 (ampicillin-resistant (A-r)/Ca-s) constituted 45% and group 3 (A-r/Ca-r) 32%. Two strains (1%) were recorded as A-s/Ca-r. Group 3 contained a higher proportion of multi-resistant strains than groups 1 and 2. The log2IC50 with ampicillin, carbenicillin, cephalothin and mecillinam in the tube-dilution method were determined for 32 strains. Groups 1 and 2 differed only as regards cephalothin resistance. The strains of group 3 were more A-r than the group 2 ones. The mecillinam susceptibility did not differ between the three groups. No strains in group 2 could transfer A-resistance. In group 3 ten out of 16 strains were able to transfer A-resistance. Resistance to sulphonamide, tetracycline, and streptomycin was also transferred, but with low frequency. The A-r/Ca-r strains could be divided into two subgroups, probably reflecting different modes of developing beta-lactam resistance. One group was very A- and Ca-r, less cephalothin-r, more mecillinam-r and could transfer A-resistance. The other group had very high cephalothin-resistance and could not transfer A-resistance. Citrobacter freundii and Enterobacter cloacae are very similar as regards resistance conditions.

Ampicillin↗
PubMed1977

Occurrence and transfer of ampicillin resistance associated with ampicillin-resistant Haemophilus influenzae isolated from a case at a day-care centre.

A 1-year-old boy with recurrent otitis media had been repeatedly treated with antibiotics. A few days after withdrawal of administered ampicillin he again contracted otitis media and ampicillin-resistant Haemophilus influenzae was isolated. The strain was serologically untypable. No ampicillin-resistant H. influenzae was found in his family or at the day-care centre that he attended. The ability to produce the beta-lactamase elaborated from this strain could be transferred to ampicillin-sensitive strains of H. influenzae and Escherichia coli in frequencies of 0.7 X 10(-7) and 4.1 X 10(-4) respectively. The transcipients obtained were ampicillin-resistant and beta-lactamase producing. In the transcipients of E. coli, however, the marker for ampicillin resistance was quite unstable.

Amidohydrolases↗
PubMed1995

Successful treatment of persistent bacteremia due to vancomycin-resistant, ampicillin-resistant Enterococcus faecium.

Emergence of vancomycin-resistant enterococci has become an increasing problem in many medical centers. We report a liver transplant recipient with vancomycin-resistant Enterococcus faecium bacteremia who was successfully treated using very high dose continuous infusion ampicillin/sulbactam, plus gentamicin after he remained bacteremic on high dose ampicillin and gentamicin. At our institution, 83% of E. faecium isolates from 1994 were inhibited by ampicillin/sulbactam compared to 66% for ampicillin at an MIC < or = 64 micrograms/ml. None of these strains produced beta-lactamase, suggesting sulbactam may have an unexplained beneficial effect against some enterococci. Although an MIC of < or = 8 micrograms/ml is required for ampicillin to be considered active against enterococci, much higher levels of ampicillin or ampicillin/sulbactam are safely achievable. The response of our patient and the reported in vivo data have implications for future treatment of this pathogen, and may necessitate a reevaluation of susceptibility interpretation guidelines by clinical laboratories, and therapeutic drug dosing by clinicians.

Aged↗
PubMed1999

The bactericidal activity of levofloxacin against ampicillin-resistant and ampicillin-susceptible Haemophilus influenzae in comparison with ofloxacin, ciprofloxacin and sparfloxacin.

The bactericidal activity of levofloxacin against four Haemophilus influenzae clinical isolates (two ampicillin-resistant and two susceptible) was compared with that of ofloxacin, ciprofloxacin and sparfloxacin at concentrations simulating the peak serum concentrations obtained with the recommended oral doses. Bactericidal activity was assessed using time-kill curves and minimum kill-time values. Both concentrations of levofloxacin rapidly killed all the study strains, with mean kill times of 4 h and no viable bacteria remaining after 18-h exposure. The bactericidal activities of levofloxacin, ofloxacin and sparfloxacin were similar. The minimum kill-times for both concentrations of ciprofloxacin were 28-35% longer than those of levofloxacin. These results support the use of levofloxacin for H. influenzae infections, including ampicillin-resistant strains.

Ampicillin↗
PubMed1981

Systemic Haemophilus influenzae infections in a community hospital: prevalence of ampicillin resistance.

Ampicillin-resistant strains are presently known to account for 10% to 20% of type b Haemophilus influenzae infections in the United States. To determine whether the incidence in a community hospital parallels that of several university hospitals, we reviewed medical records of the 99 children with type b Haemophilus systemic infections for the period 1976 to 1979. These cass represented 1.8% of all pediatric medical admissions. In 1976-1977, 5% of those infections were caused by resistant strains; the incidence increased to 19% for the period 1978-1979. This increase on a community hospital level parallels the increase in ampicillin resistance in Haemophilus noted in university hospitals and underscores the need for chloramphenicol (alone or in combination with ampicillin) as initial treatment for systemic Haemophilus infections.

Ampicillin↗
PubMedDate not supplied

The bactericidal activity of ampicillin, daptomycin, and vancomycin against ampicillin-resistant Enterococcus faecium.

Ampicillin, daptomycin, and vancomycin, alone and in combination with gentamicin, were examined for bactericidal effects on ampicillin-resistant Enterococcus faecium using broth dilution minimum inhibitory concentrations (MICs) and time-kill studies. We tested 12 ampicillin-resistant isolates and demonstrated the following MICs and MBCs, respectively: ampicillin, greater than or equal to 32 micrograms/ml and greater than 256 micrograms/ml; daptomycin, less than or equal to 4 micrograms/ml and less than or equal to 16 micrograms/ml; and vancomycin, less than or equal to 4 micrograms/ml and greater than 64 micrograms/ml. Time-kill studies demonstrated that daptomycin alone had marked activity against the ampicillin-resistant E. faecium and that the addition of gentamicin resulted in synergistic killing. In addition, ampicillin and vancomycin were not bactericidal for the ampicillin-resistant isolates without the addition of gentamicin. The present study supports the consideration of daptomycin alone or in combination with an aminoglycoside as an alternative therapy for ampicillin-resistant enterococci, although additional clinical experience is now necessary.

Ampicillin↗
PubMed1979

Transposition of ampicillin resistance to an enterotoxin plasmid in an Escherichia coli strain of human origin.

We examined a strain of Escherichia coli, serotype O159.H34, of human origin which produced heat-stable and heat-labile enterotoxins, was resistant to ampicillin, and produced colicin. By conjugation and transformation experiments plasmids coding for enterotoxin production (Ent), enterotoxin production and ampicillin resistance (Ap-Ent), ampicillin resistance (Ap), and colicin production were isolated. Both the Ent and Ap-Ent plasmids were autotransferring and belonged to the F-incompatibility complex. However, the Apr Ent+ transconjugants showed differences in their levels of resistance and in their abilities to propagate F-specific phages and to transfer resistance. The results suggested there was transposition from the small Ap plasmid to the Ent plasmid. The Ap-Ent plasmids were larger than the enterotoxin factor and when treated with restriction endonuclease BamHI showed an additional fragment not present in the enterotoxin plasmid. The insertion of ampicillin resistance probably occurred at different sites on the enterotoxin plasmid, resulting in the observed variation in phenotype.

Ampicillin↗
PubMed1975

Transfer of ampicillin resistance between strains of Haemophilus influenzae type B.

Haemophilus influenzae type B, strain W-2, is highly resistant to ampicillin (MIC, 12.5 mug/ml). The ampicillin resistance of strain W-2 was transferred to an antibiotic-sensitive strain TF-2 (RifR, SmR) during mixed incubation on membrane filters at 36 C(transfeer frequency, 4.6 times 10(-5) per donor). Resistance was also transferred from the primary recipient to a secondary one (TF-3, EryR, NovR). The transfer frequency between these derivative strains was 10(-4) after incubation for 30 min. Resistance in strain W-2 remained even after growth in the presence of ethidium bromide or at an elevated temperature, although ampicillin resistance was lost from 13%-25% of transcipient cells after growth in broth. Strain W-2 and transcipients of ampicillin resistance had equivalent levels of beta-lactamase activity, while sensitive segregants and recipient strains demonstrated little or no enzyme activity. Transfer of ampicillin resistance between strains of H. influenzae is probably mediated by conjugation since transfer (1) requires cell-to-cell contact, (2) remains unchanged in the presence of DNase I, and (3) occurs in the absence of demonstrable bacteriophage.

Ampicillin↗
PubMed2006

Sources of variation in the ampicillin-resistant Escherichia coli concentration in the feces of organic broiler chickens.

Currently, there are limited published data for the population dynamics of antimicrobial-resistant commensal bacteria. This study was designed to evaluate both the proportions of the Escherichia coli populations that are resistant to ampicillin at the level of the individual chicken on commercial broiler farms and the feasibility of obtaining repeated measures of fecal E. coli concentrations. Short-term temporal variation in the concentration of fecal E. coli was investigated, and a preliminary assessment was made of potential factors involved in the shedding of high numbers of ampicillin-resistant E. coli by growing birds in the absence of the use of antimicrobial drugs. Multilevel linear regression modeling revealed that the largest component of random variation in log-transformed fecal E. coli concentrations was seen between sampling occasions for individual birds. The incorporation of fixed effects into the model demonstrated that the older, heavier birds in the study were significantly more likely (P = 0.0003) to shed higher numbers of ampicillin-resistant E. coli. This association between increasing weight and high shedding was not seen for the total fecal E. coli population (P = 0.71). This implies that, in the absence of the administration of antimicrobial drugs, the proportion of fecal E. coli that was resistant to ampicillin increased as the birds grew. This study has shown that it is possible to collect quantitative microbiological data on broiler farms and that such data could make valuable contributions to risk assessments concerning the transfer of resistant bacteria between animal and human populations.

Ampicillin↗
PubMed1990

[High incidence of ampicillin resistance in Salmonella spp non typhi].

Salmonella spp non typhi is a common cause of gastroenteritis and, more rarely, extraintestinal infections in humans. The type of syndrome determines the choice and duration of antibiotic therapy. Extraintestinal infections by this organism require correct antibiotic therapy. In the present study, the susceptibility to antibiotics of 59 strains of Salmonella spp non typhi from clinical sources, isolated during a period of three and a half months, were evaluated. Fifty one of them were S. enteritidis, 7 S. typhimurium and 1 S. schwarzengrund. A high frequency (45.8%) of resistance to ampicillin (MIC greater than 256 micrograms/ml) was found. Other antibiotics had good or excellent in vitro activity: 90% of strains were sensitive to tetracyclines, 93% to chloramphenicol, 97% to co-trimoxazole, and 100% to cefotaxime and ciprofloxacine. It was concluded that the high frequency of ampicillin resistance to ampicillin precludes its use as first choice antibiotic in our area for suspected extraintestinal infections caused by Salmonella spp non typhi.

Ampicillin Resistance↗
PubMed1984

Characterization of non-beta-lactamase-mediated ampicillin resistance in Haemophilus influenzae.

Ampicillin resistance in Haemophilus influenzae is most often due to the plasmid-mediated production of TEM beta-lactamase. We studied four strains with high-level ampicillin resistance (MIC of 32 micrograms/ml with an inoculum of 10(5) CFU on solid media) which did not produce detectable beta-lactamase activity with two different detection methods. Two of the four strains contained extrachromosomal DNA by agarose gel electrophoresis. Conjugation failed to transfer ampicillin resistance; in contrast, transformation yielded ampicillin-resistant transformants in three of the four strains. These transformants did not contain detectable extrachromosomal DNA. In addition, mobilization of the resistance determinant by transformation to, or conjugation with, recombination-deficient strains was unsuccessful. DNA-DNA hybridization experiments revealed no homology of the DNA of these strains with two R plasmids (one coding for ampicillin resistance, the other for chloramphenicol and tetracycline resistance). We conclude that the genetic basis of the non-beta-lactamase ampicillin resistance in these strains appears to be chromosomally mediated. We investigated the mechanism of resistance in these strains. Enzymatic modification of penicillin was not detected by autoradiography of a thin-layer chromatogram of cell sonic extracts of three ampicillin-resistant transformant strains incubated with [14C]penicillin. To assess changes in permeability of the cell envelope, a plasmid coding for beta-lactamase was conjugated into these strains, and the hydrolysis of penicillin by intact cells and cell sonic extracts was compared. Only one of three transformant strains had significantly diminished permeability. Outer membrane proteins of these strains analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed apparent differences in comparison with the isogenic ampicillin-susceptible recipient strain. Autofluorography of a sodium dodecyl sulfate-polyacrylamide gel electrophoresis of Sarkosyl-solubilized crude membrane (the putative inner membranes) from these ampicillin-resistant transformant strains incubated with [3H]penicillin compared with the isogenic ampicillin-susceptible recipient strain revealed reduced binding to PBP 3 and 6, 3 and 4, or 4. In addition, affinity binding studies revealed decreased affinity of PBP 4 for ampicillin of all four transformants tested. We conclude that the major mechanism of resistance in these strains is altered penicillin-binding proteins; however, other mechanisms, including permeability, may also play a role.

Ampicillin↗
PubMed1990

Comparative in vitro activity of cefixime against Haemophilus influenzae isolates, including ampicillin-resistant, non-beta-lactamase-producing isolates, from pediatric patients.

The in vitro activity of cefixime was comparatively tested against 232 non-type b and 102 type b isolates of Haemophilus influenzae derived from clinical specimens of pediatric patients, including 10 non-type b strains that did not produce beta-lactamase and demonstrated resistance to ampicillin. Cefixime was active against the ampicillin-susceptible and ampicillin-resistant, beta-lactamase-producing isolates; however, its activity against some non-beta-lactamase-producing, ampicillin-resistant isolates appeared to be limited.

Ampicillin Resistance↗
PubMed1984

Increasing ampicillin-resistance rates in Hemophilus influenzae meningitis.

We studied the epidemiology of reported Hemophilus influenzae meningitis in Colorado for the years 1977 through 1981. Of 340 culture-confirmed cases, 94% occurred in children less than 5 years old. A marked seasonal variation was present, with peaks in late fall-early winter and late spring. The percentage of H influenzae isolates resistant to ampicillin increased from 4.2% in 1977 to 31.3% in 1981. The incidence of reported disease in children younger than 5 years of age increased from 26 per 100,000 population in 1977 to 39 per 100,000 population in 1981, The overall case fatality rate was 5.2%; mortality was somewhat higher for persons with ampicillin-resistant infections (9.4%) than for those with ampicillin-sensitive infections (4.3%). Our results agree with previous reports of an increasing rate of ampicillin resistance in H influenzae meningitis and indicate a possible increasing incidence of this disease in Colorado.

Adolescent↗
PubMed1982

Acute epiglottitis and bacteremia with ampicillin-resistant Haemophilus influenzae.

Acute epiglottitis in adults occurs more frequently than generally realized. Haemophilus influenzae type b is the major causative agent. While H influenzae resistant to ampicillin sodium has been associated with epiglottitis in children, no adult cases have been reported. We describe a 48-year-old woman with epiglottitis and associated typical rapid onset of sore throat, fever, respiratory distress, and swollen, red supraglottic structures. Blood cultures were positive for beta-lactamase-producing, ampicillin-resistant H influenzae. We conclude that H influenzae resistant to ampicillin should be considered when diagnosing and treating adult epiglottitis.

Acute Disease↗