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Biomedical subjects

G H Miller

Publications and source records attributed to G H Miller.

At least 37 records · Page 2Linked to original sources
PubMed1995

Mechanism of amikacin resistance in Pseudomonas aeruginosa isolates from patients with cystic fibrosis.

We studied 27 amikacin-resistant isolates of Pseudomonas aeruginosa from patients with cystic fibrosis to determine the mechanism of antibiotic resistance. The absence of aminoglycoside-modifying enzymes (AMEs) in these isolates was inferred from the failure of DNA probes for 16 candidate AMEs to hybridize with DNA harvested from these isolates and, in addition, the uniform reduction in susceptibility to a panel of aminoglycosides. In eight of the 27 isolates that were resistant to amikacin at high levels (minimum inhibitory concentration > or = 250 micrograms/ml), plasmids were not detected. The ribosomes of these isolates were sensitive to amikacin in studies of protein synthesis by cell "ghosts." These data suggest that impermeability is the mechanism of amikacin resistance in isolates of P. aeruginosa from patients with cystic fibrosis. Recognition of this mode of resistance may be difficult, as some isolates appeared to be borderline susceptible when tested against aminoglycosides other than amikacin, or had zone diameters that overlapped those obtained with amikacin-susceptible isolates.

Amikacin↗
PubMed1995

Dynamics of the U.S. interstate migration system, 1975-1992.

This note further develops an analysis of the U.S. interstate migration system by K.E. McHugh and P. Gober. Specifically, it uses annual state-to-state migration flow data from Internal Revenue Service for the period 1975-1992 to analyze migration trends. Some modifications to earlier conclusions are suggested. "First the note concludes that the emergence of a new pattern of population redistribution in the U.S. in the 1980s, as reported by McHugh and Gober, was indeed significant, but that it was transitory. Second, the note's analysis does not support McHugh and Gober's conclusion of a fairly strong inverse relationship between migration effectiveness and economic expansions and contractions."

Americas↗
PubMed1995

Cloning and characterization of a 3-N-aminoglycoside acetyltransferase gene, aac(3)-Ib, from Pseudomonas aeruginosa.

A novel gene encoding an aminoglycoside 3-N-acetyltransferase, which confers resistance to gentamicin, astromicin, and sisomicin, was cloned from Pseudomonas aeruginosa Stone 130. Its sequence was determined and found to show considerable similarity to an aac(3)-I gene previously cloned from R plasmids from Enterobacter, Pseudomonas, and Serratia spp. We have designated the genes from the R plasmids and this work aac(3)-Ia and aac(3)-Ib, respectively. The two aac(3)-I genes share 74% nucleotide identity, and their deduced protein products are 88% similar. These data suggest that the genes derive from a common ancestor. Homology between the flanking sequences of both aac(3)-I genes and other resistance determinants known to reside in integron environments was also observed. Intragenic probes specific for either aac(3)-Ia or aac(3)-Ib were used in hybridization studies with a series of gentamicin-, astromicin-, and sisomicin-resistant clinical isolates. Of 59 clinical isolates tested, no isolates hybridized with both probes, 30 (51%) hybridized with the aac(3)-Ia probe, 12 (20%) hybridized with the aac(3)-Ib probe, and 17 (29%) did not hybridize with either probe. These data suggest the existence of at least one other aac(3)-I gene.

Acetyltransferases↗
PubMed1995

Suspected pulmonary embolism. The difficulties of diagnostic evaluation.

It is impossible to prove or disprove a diagnosis of acute pulmonary embolism on clinical grounds. Diagnostic evaluation is best carried out by first attempting to identify a provable alternative diagnosis that can explain a patient's symptoms. Once the diagnosis of pulmonary embolism is seriously considered, a ventilation-perfusion (V/Q) scan is the next step. A positive ("high-probability") or negative ("normal-perfusion") scan is an appropriate diagnostic end point. Unfortunately, most V/Q scans are nondiagnostic, and the workup must be pursued further. Color-flow (duplex) ultrasound, if available, is the next logical step. If a site of deep venous thrombosis cannot be identified, pulmonary angiography is indicated. Newer methods, such as D-dimer measurement and spiral computed tomography, are being studied.

Humans↗
PubMed1995

Chronic pulmonary embolism. Often misdiagnosed, difficult to treat.

Chronic thromboembolic pulmonary hypertension with cor pulmonale is an extremely debilitating disease that (1) is more common than generally recognized, (2) is often misdiagnosed, and (3) is difficult to treat. When a patient has persistent exertional dyspnea with no obvious cause, a ventilation-perfusion scan, echocardiography, and (if indicated) pulmonary angiography should be done. Prevention is especially important because by the time a patient is symptomatic, the disease is already far advanced and hemodynamic reserves are greatly reduced. Prevention of recurrence mandates lifetime anticoagulation and placement of a vena cava filter. The only effective treatment is pulmonary endarterectomy, which is being performed at an increasing number of specialty centers across the United States.

Chronic Disease↗
PubMed1995

The changing nature of aminoglycoside resistance mechanisms and the role of isepamicin--a new broad-spectrum aminoglycoside. The Aminoglycoside Resistance Study Groups.

Aminoglycoside resistance mechanisms from recent studies were compared with those found in earlier studies in the USA and Europe for three pathogen groups. Among Citrobacter-Enterobacter-Klebsiella, four single mechanisms (AAc(3)-II, AAC(3)-I, ANT(2")-I and AAC(6')-I were found in all studies, but the most recent studies showed a significant increase in combinations of AAC(6')-I with the other common mechanisms. Since AAC(6')-I confers resistance to tobramycin, netilmicin and amikacin, combinations of it with the other gentamicin modifying enzymes conferred broad-spectrum resistance to all clinically available aminoglycosides except isepamicin. Similar changes occurred in Escherichia-Morganella-Proteus-Salmonella-Shigella except that the frequency of combinations was much lower and two additional single mechanisms - AAC(3)-IV and permeability - were also found frequently. Among aminoglycoside-resistant Pseudomonas, three mechanisms, AAC(6')-II, ANT(2")-I and permeability, were always common and remained common. However, combinations of the three mechanisms with each other and with other mechanisms were more common in the recent surveys. Different genes which produce different proteins with the same aminoglycoside-modifying activity are now known. The results of hybridisation studies with two aac(3)-I, 2 aac(6')-II and 4 aac(6')-I gene probes are presented. The most commonly occurring genes were: aac(3)-Ia, aac(3)-IIa, aac(6')-IIa, aac(6')-Ib and, in Serratia, aac(6')-Ic. The activity of isepamicin against amikacin resistant strain which produce AAC(6')-I can be related to differences in the structure of these two similar aminoglycosides at Position 3". Amikacin may form a stable complex with AAC(6')-I enzymes via binding interaction at Position 3 and 3". Isepamicin, which has a secondary amino group at Position 3", may only be able to interact at Position 3 and enzyme-isepamicin complexes are likely to be less stable.

Acetyltransferases↗
PubMed1994

Women and lung cancer: a comparison of active and passive smokers with nonexposed nonsmokers.

Prior to the 1920s, lung cancer was a rare disease. However, the current increase in lung cancer appears to parallel the increase in smoking for both men and women with a 30- to 50-year delay. National lung cancer deaths continue to rise, with over 168,000 total deaths estimated in 1992. Women are now showing higher percentage increases in lung cancer than men from active smoking. The data from the Erie County Study on Smoking and Health (ECSSH), a population study, were used to measure the effects of both active and passive smoking on women's lung cancer mortality. The three major categories of exposure (no known or minimal exposure, passive smoking exposed, and active smoking) were used in the analyses. The results from the population data in Erie County, PA, were based on 528 nonexposed nonsmoking women, 3138 exposed nonsmoking women, and 1747 smoking women. Deaths due to lung cancer as a percentage of total deaths excluding traumatic deaths were 0.2% for the nonexposed nonsmoking women, 0.9% for the exposed nonsmoking women, and 8.0% for women who smoked. The data showed that women smokers died of lung cancer at a rate 9 times greater than exposed nonsmokers and 42 times greater than nonexposed nonsmokers.

Adult↗
PubMed1993

Sch 39304, a new antifungal agent: oral and topical treatment of vaginal and superficial infections.

Sch 39304 is a new broad spectrum triazole antifungal agent that is active, orally and topically, against superficial Trichophyton mentagrophytes and vaginal Candida albicans infections. Sch 39304 was compared to fluconazole (FLZ) in a T. mentagrophytes infection model in guinea pigs. Following topical administration, Sch 39304 (0.125%, twice daily, 10 days), was 5-8-fold more effective than FLZ, based on culture and lesion score results. Following oral administration, Sch 39304 (2.5 mg kg-1, once daily, 10 days) produced a dramatic reduction in lesion scores and was 20-fold more active than FLZ; however, due to the length of time it takes for the drugs to reach the infected area of the skin and eradicate the infections, most animals remained culture positive with both drugs. Sch 39304 was also compared with FLZ in a vaginal C. albicans infection in hamsters. Following oral administration (4 days), Sch 39304 (1.6 mg kg-1), cured all hamsters and was 4-fold more active than FLZ. In addition, Sch 39304 as a single oral dose (10 mg kg-1) also cured all hamsters. When treatment was intravaginal (8 days), Sch 39304 was again more active than FLZ (2-fold), and also micronazole (8-fold), with 100% of the hamsters cured at concentrations as low at 0.025%.

Administration, Oral↗
PubMed1993

Analysis of the aac(3)-VIa gene encoding a novel 3-N-acetyltransferase.

Biochemical analysis (G. A. Papanicolaou, R. S. Hare, R. Mierzwa, and G. H. Miller, abstr. 152, Program Abstr. 29th Intersci. Conf. Antimicrob. Agents Chemother., 1989) demonstrated the presence of a novel 3-N-acetyltransferase in Enterobacter cloacae 88020217. This organism was resistant to gentamicin, and the MIC of 2'-N-ethylnetilmicin for it was fourfold lower than that of 6'-N-ethylnetilmicin, a resistance pattern which suggested 2'-acetylating activity. However, high-pressure liquid chromatography analysis demonstrated that the enzyme acetylated sisomicin in the 3 position. We have cloned the structural gene for this enzyme from a large (> 70-kb) conjugative plasmid present in E. cloacae. Subcloning experiments have localized the aac(3)-VIa gene to a 2.1-kb Sau3A fragment. The deduced AAC(3)-VIa protein showed 48% amino acid identity to the AAC(3)-IIa protein and 39% identity to the AAC(3)-VII protein. Examination of the 5'-flanking sequences demonstrated that the aac(3)-VIa gene was located 167 bp downstream of the aadA1 gene and was present in an integron. In addition, the aac(3)-VIa gene is also downstream of a 59-base element often seen in an integron environment. Primer extension analysis has identified a promoter for the aac(3)-VIa gene downstream of both the aadA1 gene and a 59-base element.

Amino Acid Sequence↗
PubMed1993

Nucleotide sequence analysis and DNA hybridization studies of the ant(4')-IIa gene from Pseudomonas aeruginosa.

The ant(4')-IIa gene was previously cloned from Pseudomonas aeruginosa on a 1.6-kb DNA fragment (G. A. Jacoby, M. J. Blaser, P. Santanam, H. Hächler, F. H. Kayser, R. S. Hare, and G. H. Miller, Antimicrob. Agents Chemother. 34:2381-2386, 1990). In the current study, the ant(4')-IIa gene was localized by gamma-delta mutagenesis. A region of approximately 600 nucleotides which contained the ant(4')-IIa gene was identified, and DNA sequence analysis revealed two overlapping open reading frames (ORFs) within this region. Northern (RNA) blot analysis demonstrated expression of both ORFs in P. aeruginosa; therefore, site-directed mutagenesis was used to identify the ORF which encodes the ant(4')-IIa gene. No homology was found between ant(4')-IIa and ant(4')-Ia DNA sequences. Hybridization experiments confirmed that the ant(4')-Ia probe hybridized only to gram-positive presumptive ANT(4')-I strains and that the ant(4')-IIa probe hybridized only to gram-negative strains presumed to carry ANT(4')-II. Seven gram-negative strains which had been classified as having ANT(4')-II resistance profiles did not hybridize with probes for either ant(4')-Ia or ant(4')-IIa, suggesting that at least one additional ant(4') gene may exist. The predicted amino-terminal sequences of the ANT(4')-Ia and ANT(4')-IIa proteins showed significant sequence similarity between residues 38 and 63 of the ANT(4')-Ia protein and residues 26 and 51 of the ANT(4')-IIa protein.

Base Sequence↗
PubMed1993

Molecular genetics of aminoglycoside resistance genes and familial relationships of the aminoglycoside-modifying enzymes.

The three classes of enzymes which inactivate aminoglycosides and lead to bacterial resistance are reviewed. DNA hybridization studies have shown that different genes can encode aminoglycoside-modifying enzymes with identical resistance profiles. Comparisons of the amino acid sequences of 49 aminoglycoside-modifying enzymes have revealed new insights into the evolution and relatedness of these proteins. A preliminary assessment of the amino acids which may be important in binding aminoglycosides was obtained from these data and from the results of mutational analysis of several of the genes encoding aminoglycoside-modifying enzymes. Recent studies have demonstrated that aminoglycoside resistance can emerge as a result of alterations in the regulation of normally quiescent cellular genes or as a result of acquiring genes which may have originated from aminoglycoside-producing organisms or from other resistant organisms. Dissemination of these genes is aided by a variety of genetic elements including integrons, transposons, and broad-host-range plasmids. As knowledge of the molecular structure of these enzymes increases, progress can be made in our understanding of how resistance to new aminoglycosides emerges.

Acetyltransferases↗
PubMed1992

Pleistocene geochronology and palaeothermometry from protein diagenesis in ostrich eggshells: implications for the evolution of modern humans.

Proteinaceous residues incorporated within the crystal structure of ostrich eggshells (OES) are retained without loss over geological time exceeding 10 million years. Degradation of the polypeptides, including hydrolysis to smaller peptide fragments and eventual release of free amino acids, decomposition, and racemization and epimerization occur at regular, predictable rates dependent on ambient temperature. The extent of isoleucine epimerization (aIle/Ile ratio) in OES follows linear first-order reversible kinetics in controlled-temperature laboratory simulations of time up to an aIle/Ile ratio in excess of 1.0. The hydrolysis of leucine also follows a predictable pattern, but deviates from first-order kinetics. A nonlinear mathematical model has been developed that adequately describes the pattern of leucine hydrolysis through a wide temperature range. Arrhenius parameters were derived from laboratory experiments combined with rate constant values found for 14C-dated OES from stratified caves in southern Africa. These parameters for isoleucine epimerization and leucine hydrolysis differ by ca. 10%, allowing the simultaneous solution of the two equations for temperature, independent of sample age. Although the uncertainty of the simultaneous temperature is relatively high (+/- 10 degrees C), it provides an effective means of identifying burned samples. If sample age is known, palaeotemperatures (the integrated thermal history experienced by an eggshell as opposed to an 'instantaneous' temperature) can be calculated with a precision of better than +/- 1 degrees C. The ages of levels at Border Cave, South Africa, from which anatomically modern human skeletal remains have been recovered, are dated by the extent of isoleucine epimerization in associated OES.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Diversity of aminoglycoside resistance in Enterobacter cloacae in Greece.

Ninety Enterobacter cloacae strains isolated from 12 Greek hospitals were examined in terms of epidemiological types and resistance mechanisms. Using O serotyping 69% of the strains were assigned to a specific serotype and overall 16 different serotypes were identified. The combination of serotyping, phagetyping and biotyping efficiently discriminated most of the strains, indicating that single epidemic strains were not prevalent, although serotypes 3, 7, and group II predominated. Eight representative strains, all resistant to gentamicin, tobramycin, amikacin and netilmicin, were further examined for transferability and mechanisms of resistance. Aminoglycoside resistance was found to be transferable in most strains, and 13 R plasmids of 40-120 MDa molecular weight were detected. The enzymes detected consisted of three enzymes active against gentamicin [ANT(2h'), AAC(3)-I and AAC(3)-V]; three active against tobramycin [ANT(2"), AAC(3)-V and AAC(6')-I]; two active against netilmicin [AAC(3)-V and AAC(6')-I]; and one active against amikacin [AAC(6')-I]. APH(3') and ANT (3"), which modify neomycin and streptomycin plus spectinomycin respectively, were also found. Overall up to five aminoglycoside modifying enzymes were detected on the same R plasmid, AAC(6')-I plus ANT(2") being the most prevalent. The high incidence of multiresistance in Enterobacter cloacae and the fact that resistance is due to enzymatic inactivation of the antibiotics, indicate that in Greece this species might act as a gene pool for the spread of resistance to other bacteria of clinical relevance.

Aminoglycosides↗
PubMed1992

Comparison of SCH 39304, fluconazole, and ketoconazole for treatment of systemic infections in mice.

SCH 39304 was compared with fluconazole and ketoconazole in a systemic Candida albicans infection in mice (10(6) CFU per mouse). Results were based on survival rates and CFU in kidneys following once-daily oral treatment of 2, 5, or 10 days duration. In normal mice, SCH 39304 (dose to reduce kidney counts by 4 log units, 0.5 mg/kg of body weight) was 3 and 200 times more active than fluconazole and ketoconazole, respectively. In immunocompromised mice (gamma irradiation, 600 rads), SCH 39304 (dose to reduce kidney counts by 4 log units, 1.3 mg/kg) was 35 and greater than 100 times more active than fluconazole and ketoconazole, respectively. In normal mice, when the infecting inoculum varied from 10(5) to 10(7) CFU, only a fivefold increase in the dose to reduce kidney counts by 4 log units was observed with SCH 39304. Excellent protection was also seen when mice were treated with a single oral dose of SCH 39304 up to 24 h prior to infection with C. albicans. Studies in a systemic C. albicans infection model indicated that SCH 39304 is equally efficacious following either oral or intravenous administration. In a systemic Aspergillus flavus infection, mice treated with SCH 39304 (5 mg/kg) survived twice as long (16 days) as those treated with fluconazole (50 mg/kg) or controls did.

Administration, Oral↗
PubMed1992

Cloning and DNA sequence analysis of an aac(3)-Vb gene from Serratia marcescens.

The AAC(3)-V resistance mechanism is characterized by high-level resistance to the aminoglycosides gentamicin, netilmicin, 2'-N-ethylnetilmicin, and 6'-N-ethylnetilmicin and moderate resistance levels to tobramycin. Serratia marcescens 82041944 contains an AA(3)-V resistance mechanism as determined from aminoglycoside resistance profiles. This strain, however, does not exhibit hybridization with a probe derived from the previously cloned aac(3)-Va gene, (R. Allmansberger, B. Bräu, and W. Piepersberg, Mol. Gen. Genet. 198:514-520, 1985). High-pressure liquid chromatography analysis of the acetylation products of sisomicin carried out by extracts of S. marcescens 82041944 have demonstrated the presence of an AAC(3) enzyme. We have cloned the gene encoding this acetyltransferase and have designated it aac(3)-Vb. Nucleotide sequence comparisons show that the aac(3)-Va and aac(3)-Vb genes are 72% identical. The predicted AAC(3)-Vb protein is 28,782 Da. Comparisons of the deduced amino acid sequences show 75% identity and 84% similarity between the AAC(3)-Va and AAC(3)-Vb proteins. The use of a DNA fragment internal to the aac(3)-Vb as a hybridization probe demonstrated that the aac(3)-Vb gene is very rare in clinical isolates possessing an AAC(3)-V mechanism.

Amino Acid Sequence↗
PubMed1992

In vitro and in vivo activities of SCH 42427, the active enantiomer of the antifungal agent SCH 39304.

SCH 39304, a new triazole antifungal agent, is a 50:50 racemic mixture of two enantiomers, SCH 42427 and SCH 42426. The activities of these three compounds were compared in a series of in vitro and in vivo experiments. SCH 42427 was twofold more active in vitro against a variety of yeasts and dermatophytes than SCH 39304, while SCH 42426 was inactive (MICs greater than 64 micrograms/ml). In a systemic Candida albicans infection in mice, SCH 42427 administered orally (p.o.) (50% protective dose [PD50], 0.17 mg/kg of body weight; 50% effective dose, [ED50], 0.47 mg/kg) had greater efficacy than SCH 39304 (PD50, 0.21 mg/kg; ED50, 0.62 mg/kg) and SCH 42426 (greater than 100 mg/kg for PD50 and ED50). In a pulmonary Aspergillus flavus infection in mice, SCH 42427 p.o. (PD50, 13 mg/kg) was also more effective than SCH 39304 (18 mg/kg) and SCH 42426 (greater than 250 mg/kg). In a C. albicans vaginal infection in hamsters, SCH 42427 p.o. (ED50, 3.5 mg/kg) was more active than SCH 39304 (8.5 mg/kg) and SCH 42426 (320 mg/kg). Following topical administration, against a Trichophyton mentagrophytes infection in guinea pigs, SCH 42427 was about 2-fold more active than SCH 39304 and about 100-fold more active than SCH 42426. These and other results indicated that SCH 42427 is the active enantiomer, responsible for all the antifungal activity observed with SCH 39304.

Animals↗
PubMed1992

Characterization of the chromosomal aac(6')-Ic gene from Serratia marcescens.

The DNA sequence of the chromosomal aac(6')-Ic gene from Serratia marcescens, which had been previously cloned (H. M. Champion, P. M. Bennett, D. A. Lewis, and D. S. Reeves, J. Antimicrob. Chemother. 22:587-596, 1988) was determined. High-pressure liquid chromatographic analysis of extracts prepared from Escherichia coli carrying the chromosomal aac(6')-Ic gene on a plasmid confirmed the presence of 6'-N-acetyltransferase activity in this strain, which was suggested by the aminoglycoside resistance profile. DNA sequence analysis of the cloned 2,057-bp PstI fragment revealed several regions of homology to previously characterized sequences from GenBank, including the rpoD and tRNA-2 genes of E. coli. Subcloning experiments confirmed the coding sequence of the aac(6')-Ic gene to be at positions 1554 to 1992. The predicted amino acid sequence of the AAC(6')-Ic protein suggested that it was the third member of a family of AAC(6') proteins which included a coding region identified between the aadB and aadA genes of Tn4000 and an AAC(6') protein encoded by pUO490, which was isolated from Enterobacter cloacae. Primer extension analysis suggested that the -35 region of the aac(6')-Ic promoter overlapped a large palindromic sequence which may be involved in the regulation of the aac(6')-Ic gene. Hybridization experiments utilizing a restriction fragment from the aac(6')-Ic gene showed that all S. marcescens organisms carried this gene whether or not the AAC(6')-I resistance profile was expressed. Organisms other than Serratia spp. did not hybridize to this probe.

Base Sequence↗