bluuebunny/crossref_metadata_2025 huggingface dataset:
Inter- and Intraquinolone Predictors of Antimicrobial Effect in an In Vitro Dynamic Model: New Insight into a Widely Used Concept
Authors: Firsov Alexander A. , Shevchenko Alexander A. , Vostrov Sergey N. , Zinner Stephen H.
Published: October 2018

Earlier efforts to search for pharmacokinetic and bacteriological predictors of fluoroquinolone antimicrobial effects (AMEs) have resulted in conflicting findings. To elucidate whether these conflicts are real or apparent, several predictors of the AMEs of two pharmacokinetically different antibiotics, trovafloxacin (TRO) and ciprofloxacin (CIP), as well as different dosing regimens of CIP were examined. The AMEs of TRO given once daily (q.d.) and CIP given q.d. and twice daily (b.i.d.) against
Escherichia coli
,
Pseudomonas aeruginosa
, and
Klebsiella pneumoniae
were studied in an in vitro dynamic model. Different monoexponential pharmacokinetic profiles were simulated with a TRO half-life of 9.2 h and a CIP half-life of 4.0 h to provide similar eightfold ranges of the area under the concentration-time curve (AUC)-to-MIC ratios, from 54 to 432 and from 59 to 473 (μg · h/ml)/(μg/ml), respectively. In each case the observation periods were designed to incorporate full-term regrowth phases in the time-kill curves, and the AME was expressed by its intensity (

I
E

; the area between the control growth and time-kill and regrowth curves up to the point at which the viable counts of regrowing bacteria are close to the maximum values observed without drug). Species-independent linear relationships were established between

I
E

and log AUC/MIC, log AUC above MIC (log AUC
eff
), and time above the MIC (
T
eff
). Specific and nonsuperimposed

I
E

versus log AUC/MIC or log AUC
eff
relationships were inherent in each of the treatments: TRO given q.d. (
r
2
= 0.97 and 0.96), CIP given q.d. (
r
2
= 0.98 and 0.96), and CIP given b.i.d. (
r
2
= 0.95 and 0.93). This suggests that in order to combine data sets obtained with individual quinolones to examine potential predictors, one must be sure that these sets may be combined. Unlike AUC/MIC and AUC
eff
, the

I
E

-
T
eff
relationships plotted for the different quinolones and dosing regimens were nonspecific and virtually superimposed (
r
2
= 0.95). Hence, AUC/MIC, AUC
eff
, and
T
eff
were equally good predictors of the AME of each of the quinolones and each dosing regimen taken separately, whereas
T
eff
was also a good predictor of the AMEs of the quinolones and their regimens taken together. However, neither the quinolones nor the dosing regimens could be distinguished solely on the basis of
T
eff
, whereas they could be distinguished on the basis of AUC/MIC or AUC
eff
. Thus, two types of predictors of the quinolone AME may be identified: intraquinolone and/or intraregimen predictors (AUC/MIC, AUC
eff
and T
eff
) and an interquinolone and interregimen predictor (
T
eff
).
T
eff
may be able to accurately predict the AME of one quinolone on the basis of the data obtained for another quinolone.
Anti-
Pneumocystis
Activities of Aromatic Diamidoxime Prodrugs
Authors: Hall James Edwin , Kerrigan John E. , Ramachandran Kishore , Bender Brendan C. , Stanko Jason P. , Jones Susan K. , Patrick Donald A. , Tidwell Richard R.
Published: October 2018

Aromatic dicationic compounds, such as pentamidine, have potent antimicrobial activities. Clinical use of these compounds has been restricted, however, by their toxicity and limited oral activity. A novel approach, using amidoxime derivatives as prodrugs, has recently been proposed to overcome these limitations. Although results were presented for amidoxime derivatives of only one diamidine, pentamidine, the authors in the original proposal claimed that amidoxime derivatives would work as effective prodrugs for all pharmacologically active diamidines. Nine novel amidoxime derivatives were synthesized and tested in the present study for activity against
Pneumocystis carinii
in corticosteroid-suppressed rats. Only three of the nine compounds had significant oral anti-
Pneumocystis
activity. The bisbenzamidoxime derivatives of three direct pentamidine analogs had excellent oral and intravenous activities and reduced acute host toxicity. These compounds are not likely candidates for future drug development, however, because they have chronic toxic effects and the active amidine compounds have multiple sites susceptible to oxidative metabolism, which complicates their pharmacology and toxicology. Novel diamidoximes from three other structural classes, containing different groups linking the cationic moieties, lacked significant oral or intravenous anti-
Pneumocystis
activity, even though the corresponding diamidines were very active intravenously. Both active and inactive amidoximes were readily metabolized to the corresponding amidines by cell-free liver homogenates. Thus, the amidoxime prodrug approach may provide a strategy to exploit the potent antimicrobial and other pharmacological activities of selected, but certainly not all, aromatic diamidines.
In Vitro Activities of Quinupristin-Dalfopristin and the Streptogramin RPR 106972 against
Mycoplasma pneumoniae
Authors: Izumikawa Koichi , Hirakata Yoichi , Yamaguchi Toshiyuki , Yoshida Ryoji , Tanaka Hironori , Takemura Hiromu , Maesaki Shigefumi , Tomono Kazunori , Kaku Mitsuo , Izumikawa Kin-Ichi , Kamihira Shimeru , Kohno Shigeru
Published: October 2018

The in vitro activities of quinupristin-dalfopristin and streptogramin RPR 106972 were determined with 44 strains of
Mycoplasma pneumoniae
and compared to those of macrolides, minocycline, and quinolones. All isolates tested were highly susceptible to macrolides and to quinupristin-dalfopristin (MIC at which 90% of the isolates are inhibited [MIC
90
], 0.0625 μg/ml), followed by RPR 106972 (MIC
90
, 0.5 μg/ml), quinolones, and minocycline.
Duration and Clinical Relevance of Postantibiotic Effect in Relation to the Dosing Interval
Authors: den Hollander Jan G. , Fuursted Kurt , Verbrugh Henri A. , Mouton Johan W.
Published: October 2018

The influence of half-life on the postantibiotic effect (PAE) of tobramycin against
Pseudomonas aeruginosa
and
Staphylococcus aureus
was investigated during one dosing interval. Tobramycin half-lives of 0.5 to 2.5 h were simulated in an in vitro model, and the PAE was determined by an enzymatic inactivation method at different time points, i.e., when the tobramycin concentrations were 20×, 5×, and 1× the MIC. At the time point during therapy when the tobramycin concentrations had declined to 1× the MIC, at a tobramycin half-life of 0.5 h, the times of the PAEs were approximately 0.7 and 1.7 h for
P. aeruginosa
and
S. aureus
, respectively, and the PAE disappeared completely at half-lives corresponding to those found in humans (i.e., 2 to 2.5 h). The PAE itself cannot be fully explained by the presence of free intrabacterial tobramycin or the emergence of resistant subpopulations. The explanation for the disappearance of the PAE during the dosing interval may therefore be explained by the repair of sublethal damage. Since the standard method of determining the PAE in animal models is somewhat different from the method used for measurement of the PAE in vitro, the conditions under which the PAE is measured in vivo were also simulated in the in vitro model. This resulted in PAEs longer than those found by the standard method of obtaining in vitro PAE measurements. We conclude that the PAE of tobramycin, as determined by conventional in vitro methods, has virtually no clinical importance. PAEs determined in vivo may have some clinical relevance, but they are probably primarily caused by sub-MIC effects.
Amphotericin B in Lipid Emulsion: Stability, Compatibility, and In Vitro Antifungal Activity
Authors: Walker Scott , Tailor Sandra A. N. , Lee Mark , Louie Lisa , Louie Marie , Simor Andrew E.
Published: October 2018

Newer formulations of amphotericin B (AmB) complexed with liposomes or lipid suspensions have been developed. Preliminary studies have suggested that AmB in Intralipid (IL) may be as effective as, but less toxic than, conventional formulations of AmB, but few data are available regarding its stability, compatibility, or in vitro antifungal activity. A compatibility study was done to evaluate the effects of AmB concentrations in IL containing either 10 or 20% soybean oil. The effects of temperature, shaking, and AmB and IL concentrations on the stability of AmB-IL suspensions were analyzed by visual inspection and liquid chromatography. The in vitro antifungal activity of AmB-IL, compared to that of AmB alone against reference strains of
Candida
species was determined by using a broth macrodilution method in accordance with National Committee for Clinical Laboratory Standards guidelines (M27-T). Samples of AmB-IL which were lightly shaken retained more than 90% of the AmB concentration over 21 days when stored at either 4 or 23°C. Varying the AmB concentration did not appear to affect the stability of AmB-IL. However, a precipitate was formed when mixtures with more than 30% lipid as a proportion of the total volume were centrifuged. AmB-IL and AmB alone had similar in vitro antifungal activities against reference strains of yeasts. Further pharmacologic and clinical studies with AmB-IL are warranted, although AmB should not be combined with IL in concentrations capable of producing a precipitate.
Activity of Amoxicillin-Clavulanate against Penicillin-Resistant
Streptococcus pneumoniae
in an Experimental Respiratory Infection Model in Rats
Authors: Smith Gillian M. , Slocombe Brian , Abbott Karen H. , Mizen Linda W.
Published: October 2018

High doses of amoxicillin, equivalent to those produced by 500- and 750-mg oral doses in humans (area under the plasma concentration-time curve), were effective against a penicillin-resistant strain of
Streptococcus pneumoniae
in an experimental respiratory tract infection in immunocompromised rats; this superior activity confirms the results of previous studies. An unexpected enhancement of amoxicillin’s antibacterial activity in vivo against penicillin-resistant and -susceptible
S. pneumoniae
strains was observed when subtherapeutic doses of amoxicillin were coadministered with the β-lactamase inhibitor potassium clavulanate. The reason for this enhancement was unclear since these organisms do not produce β-lactamase. The differential binding of clavulanic acid and amoxicillin to penicillin-binding proteins may have contributed to the observed effects.
Population Pharmacokinetic Study of Amikacin Administered Once or Twice Daily to Febrile, Severely Neutropenic Adults
Authors: Tod Michel , Lortholary Olivier , Seytre Delphine , Semaoun Rémi , Uzzan Bernard , Guillevin Loïc , Casassus Philippe , Petitjean Olivier
Published: October 2018

Once-daily (o.d.) administration of 20 mg of amikacin per kg of body weight to neutropenic patients has been validated by clinical studies, but amikacin pharmacokinetics have been documented only for the 7.5-mg/kg twice-daily (b.i.d.) regimen in this population. In order to determine in neutropenic patients (i) the influence of the dosing regimen on the kinetics of amikacin, (ii) the linearity of kinetics of amikacin in the range of 7.5 to 20 mg/kg, and (iii) the influence of patient characteristics on the disposition of amikacin and (iv) to provide a rationale for dosing recommendations, we evaluated the population pharmacokinetics of amikacin administered to 57 febrile neutropenic adults (neutrophil count, <500/mm
3
) being treated for a hematological disorder and receiving amikacin at 7.5 mg/kg b.i.d. (
n
= 29) or 20 mg/kg o.d. (
n
= 28) and administered intravenously over 0.5 h. A total of 278 blood samples were obtained (1 to 14 samples per patient) during one or several administration intervals (1 to 47). Serum amikacin levels were measured by the enzyme-multiplied immunoassay technique. A mixed-effect modeling approach was used to fit a bicompartmental model to the data (NONMEM software). The influences of the dosing regimen and the demographic and biological indices on the pharmacokinetic parameters of amikacin were evaluated by the maximum-likelihood ratio test on the population model. The dosing regimen had no influence on amikacin pharmacokinetic parameters, i.e., the kinetics of amikacin were linear over the range of 7.5 to 20 mg/kg. Amikacin elimination clearance (CL) was only correlated with creatinine clearance or its covariates, namely, sex, age, body weight, and serum creatinine level. The interindividual variability of CL was 21%, while those of the central volume of distribution, the distribution clearance, and the tissue volume of distribution were 15, 30, and 25%, respectively. On the basis of the expected distribution of amikacin concentrations in this population, dosing recommendations as a function of creatinine clearance (CL
CR
) are proposed: for patients with normal renal function (CL
CR
of 80 to 130 ml/min), 20 mg/kg o.d. is recommended, whereas for patients with severe renal impairment (CL
CR
, 10 to 20 ml/min), a dosage of 17 mg/kg every 48 h is recommended.
Efficacy of Trovafloxacin against Penicillin-Susceptible and Multiresistant Strains of
Streptococcus pneumoniae
in a Mouse Pneumonia Model
Authors: Bédos Jean-Pierre , Rieux Véronique , Bauchet Jacqueline , Muffat-Joly Martine , Carbon Claude , Azoulay-Dupuis Esther
Published: October 2018

The increasing emergence of penicillin-resistant and multidrug-resistant strains of
Streptococcus pneumoniae
will create a serious therapeutic problem in coming years. Trovafloxacin is a novel naphthyridone quinolone with promising activity against
S. pneumoniae
, including penicillin-resistant strains (MIC for 90% of the isolates tested, 0.25 μg/ml). We compared its in vivo efficacy with that of other fluoroquinolones (ciprofloxacin, temafloxacin, and sparfloxacin) and a reference beta-lactam (amoxicillin) in a model of acute experimental pneumonia. Immunocompetent Swiss mice were infected by peroral tracheal delivery of a virulent, penicillin-susceptible strain (MIC, 0.03 μg/ml); leukopenic Swiss mice were infected with three poorly virulent, penicillin-resistant strains (MICs, 4 to 8 μg/ml) and a ciprofloxacin-resistant strain (MIC, 32 μg/ml). Treatments were started 6 h (immunocompetent mice) or 3 h (leukopenic mice) after infection. Doses ranging from 12.5 to 300 mg/kg were given at 12- or 8-h intervals for 3 days. Trovafloxacin (25 mg/kg) was the most effective agent in vivo against penicillin-susceptible and -resistant strains. Corresponding survival rates were 2- to 4-fold higher than with 50-mg/kg sparfloxacin or temafloxacin and 8- to 16-fold higher than with 100-mg/kg ciprofloxacin. The ratios of the area under the concentration-time curve to the MIC in serum and lung tissue were more favorable with trovafloxacin than with the other quinolones. Efficacy in vivo correlated with pharmacokinetic parameters. Trovafloxacin shows potential for the treatment of infections due to penicillin-susceptible and -resistant
S. pneumoniae
but appears to be ineffective against a ciprofloxacin-resistant strain.
Comparison of Fungizone, Amphotec, AmBisome, and Abelcet for Treatment of Systemic Murine Cryptococcosis
Authors: Clemons Karl V. , Stevens David A.
Published: October 2018

Three lipid-based formulations of amphotericin B have been approved for use in various countries. The aim of this study was to compare Amphotec (ABCD; Sequus), AmBisome (AmBi; Nexstar), Abelcet (ABLC; The Liposome Co.), and conventional deoxycholate amphotericin B (Fungizone; Bristol Meyers Squibb) for the treatment of experimental systemic cryptococcosis. A model was established in 10-week-old female CD-1 mice by intravenous (i.v.) injection of 6.25 × 10
5
viable
Cryptococcus neoformans
yeast cells. Therapy began 4 days later, with i.v. administration three times per week for 2 weeks. Mice received either no treatment, 1 mg of Fungizone per kg of body weight, or 1, 5, or 10 mg of ABCD, AmBi, or ABLC per kg. Ninety percent of control mice died between days 15 and 34. All treatment regimens except ABLC at 1 mg/kg prolonged survival compared with no treatment (
P
< 0.01 to 0.001). All mice receiving 5 or 10 mg of ABCD or AmBi per kg and 90% of mice given 10 mg of ABLC per kg survived, whereas ≤50% of those given other treatment regimens survived. Fungizone was the least effective of the four formulations, with 5 or 10 mg of ABCD, AmBi, or ABLC per kg resulting in a significantly better outcome than Fungizone (
P
< 0.001). Among the three formulations, ABCD and AmBi were equally effective, both being better than ABLC at equal 5- or 10-mg/kg doses (
P
< 0.001). Comparison of residual infectious burdens in various organs showed that each drug had some dose-responsive efficacy in three or more organs at escalating doses. In the brain, ABCD or AmBi at 5 or 10 mg/kg or ABLC at 10 mg/kg was more effective than Fungizone at 1 mg/kg or no treatment, while ABCD or AmBi at 1 mg/kg was as effective as ABLC at 10 mg/kg. Similar results were obtained for the kidneys and lungs. In the spleen, ABCD at 10 mg/kg cured all mice of infection and was superior to all other regimens. In the liver, AmBi at 5 mg/kg was superior to an equal dose of ABCD or ABLC. Overall, the efficacies of ABCD and AmBi were equal to that of Fungizone at 1 mg/kg and were about 10-fold better than that of ABLC, particularly in the brain; a comparative rank order of efficacies was ABCD ≅ AmBi > ABLC ≫ Fungizone. This is the first study that compared all four amphotericin B formulations.
Synthesis and Antibacterial Evaluation of Novel Water-Soluble Organic Peroxides
Authors: Liu Wenqiu , Liu Xuejun , Knaebel David , Luck Linda , Li Yuzhou
Published: October 2018

A set of new water-soluble organic peroxides has been synthesized and evaluated for in vitro antibacterial activity as part of an effort to develop new antibacterial agents for the treatment of acne vulgaris. The water solubility of these new dialkyl peroxides and peroxyesters was achieved by incorporating either a quaternary ammonium group or a polyethylene glycol moiety. These peroxides are effective against both gram-positive and gram-negative bacteria and have a prolonged activity compared to that of benzoyl peroxide and other peroxide-type antiseptic agents. Among them 4-[[(
tert
-butylperoxy)carbonyl]benzyl]triethylammonium chloride and [10-(
tert
-butylperoxy)decyl]trimethylammonium bromide have the broadest antimicrobial spectrums. We have shown that the oxidizing properties of the dioxy group of these compounds are responsible for their antibacterial activities.
Effects of Slime Produced by Clinical Isolates of Coagulase-Negative Staphylococci on Activities of Various Antimicrobial Agents
Authors: Souli Maria , Giamarellou Helen
Published: October 2018

A novel in vitro semiquantitative method was developed to investigate the influence of staphylococcal slime on the activities of 22 antimicrobial agents. Pefloxacin, teicoplanin, and vancomycin demonstrated remarkable decreases in efficacy: 30, 52, and 63%, respectively. The activity of rifampin was not significantly reduced (0.99%), whereas all other agents tested were modestly affected (<15% decrease). These data could be influential in the treatment of implant-associated infections caused by slime-producing staphylococci.
Determination of Activities of Levofloxacin, Alone and Combined with Gentamicin, Ceftazidime, Cefpirome, and Meropenem, against 124 Strains of
Pseudomonas aeruginosa
by Checkerboard and Time-Kill Methodology
Authors: Visalli Melissa A. , Jacobs Michael R. , Appelbaum Peter C.
Published: October 2018

A total of 124
Pseudomonas aeruginosa
strains were tested for synergy between levofloxacin and cefpirome, ceftazidime, gentamicin, and meropenem. Checkerboards yielded synergistic fractional inhibitory concentration (FIC) indices (≤0.5) with 25 of 496 possible combinations. All other FIC indices were >0.5 to 2 (additive or indifferent), with no antagonism. Time-kill studies with 12 strains showed that levofloxacin (0.06 to 0.5 μg/ml) was synergistic with cefpirome, ceftazidime, gentamicin, and meropenem in 10, 9, 4, and 11 strains, respectively.
Killing of
Staphylococcus aureus
by C-8-Methoxy Fluoroquinolones
Authors: Zhao Xilin , Wang Jian-Ying , Xu Chen , Dong Yuzhi , Zhou Jianfeng , Domagala John , Drlica Karl
Published: October 2018

C-8-methoxy fluoroquinolones were more lethal than C-8-bromine, C-8-ethoxy, and C-8-H derivatives for
Staphylococcus aureus
, especially when topoisomerase IV was resistant. The methoxy group also increased lethality against wild-type cells when protein synthesis was inhibited. These properties encourage refinement of C-8-methoxy fluoroquinolones to kill staphylococci.
In Vitro Susceptibilities of Aerobic and Facultative Non-Spore-Forming Gram-Positive Bacilli to HMR 3647 (RU 66647) and 14 Other Antimicrobials
Authors: Soriano Francisco , Fernández-Roblas Ricardo , Calvo Raquel , García-Calvo Gloria
Published: October 2018

The comparative in vitro activity of the ketolide HMR 3647 (RU 66647) and those of structurally related macrolide-lincosamide-streptogramin compounds (erythromycin, roxithromycin, azithromycin, clarithromycin, josamycin, lincomycin, pristinamycin, and quinupristin-dalfopristin) as well as those of benzylpenicillin, doxycycline, vancomycin, teicoplanin, levofloxacin, and rifapentine against 247 aerobic and facultative non-spore-forming gram-positive bacilli were determined by an agar dilution method. The ketolide was active against most organisms tested except
Corynebacterium striatum
, coryneform CDC group I2, and
Oerskovia
spp. The frequency of resistance to erythromycin and other macrolides as well as that to lincomycin was high. Pristinamycin and, to a lesser extent, quinupristin-dalfopristin were very active, but resistance to these agents was present in some strains of
Rhodococcus equi
,
Listeria
spp.,
C. striatum
,
Erysipelothrix rhusiopathiae
, and
Oerskovia
spp. HMR 3647 was very active against all erythromycin-sensitive and many erythromycin-nonsusceptible strains, especially
Corynebacterium minutissimum
,
Corynebacterium pseudodiphtheriticum
,
Corynebacterium amycolatum
, and
Corynebacterium jeikeium
. In vitro resistance to benzylpenicillin was common, but doxycycline, vancomycin, and teicoplanin were very active against most organisms tested except
E. rhusiopathiae
, against which glycopeptide antibiotics were not active. The in vitro activity of levofloxacin was remarkable, but resistance to this agent was common for
C. amycolatum
,
Corynebacterium urealyticum
,
C. jeikeium
, and
Oerskovia
spp. strains. Rifapentine was also very active in vitro against many organisms, but resistance to this agent was always present in
E. rhusiopathiae
and was very common in
C. striatum
and
C. urealyticum.
Metabolism in Human Cells of the
d
and
l
Enantiomers of the Carbocyclic Analog of 2′-Deoxyguanosine: Substrate Activity with Deoxycytidine Kinase, Mitochondrial Deoxyguanosine Kinase, and 5′-Nucleotidase
Authors: Bennett L. Lee , Allan Paula W. , Arnett Gussie , Shealy Y. Fulmer , Shewach Donna S. , Mason William S. , Fourel Isabelle , Parker William B.
Published: October 2018

The carbocyclic analog of 2′-deoxyguanosine (CdG) has broad-spectrum antiviral activity. Because of recent observations with other nucleoside analogs that biological activity may be associated the
l
enantiomer rather than, as expected, with the
d
enantiomer, we have studied the metabolism of both enantiomers of CdG to identify the enzymes responsible for the phosphorylation of CdG in noninfected and virally infected human and duck cells. We have examined the enantiomers as substrates for each of the cellular enzymes known to catalyze phosphorylation of deoxyguanosine. Both enantiomers of CdG were substrates for deoxycytidine kinase (EC
2.7.1.74
) from MOLT-4 cells, 5′-nucleotidase (EC
3.1.3.5
) from HEp-2 cells, and mitochondrial deoxyguanosine kinase (EC
2.7.1.113
) from human platelets and CEM cells. For both deoxycytidine kinase and mitochondrial deoxyguanosine kinase, the
l
enantiomer was the better substrate. Even though the
d
enantiomer was the preferred substrate with 5′-nucleotidase, the rate of phosphorylation of the
l
enantiomer was substantial. The phosphorylation of
d
-CdG in MRC-5 cells was greatly stimulated by infection with human cytomegalovirus. The fact that the phosphorylation of
d
-CdG was stimulated by mycophenolic acid and was not affected by deoxycytidine suggested that 5′-nucleotidase was the enzyme primarily responsible for its metabolism in virally infected cells.
d
-CdG was extensively phosphorylated in duck hepatocytes, and its phosphorylation was not affected by infection with duck hepatitis B virus. These results are of importance in understanding the mode of action of
d
-CdG and related analogs and in the design of new biologically active analogs.
Drug Evaluation of Concurrent
Pneumocystis carinii
,
Toxoplasma gondii
, and
Mycobacterium avium
Complex Infections in a Rat Model
Authors: Brun-Pascaud Monique , Rajagopalan-Levasseur Premavathy , Chau Françoise , Bertrand Guylène , Garry Louis , Derouin Francis , Girard Pierre-Marie
Published: October 2018

We present a new experimental model for the simultaneous evaluation of the activities of drugs against
Pneumocystis carinii
,
Toxoplasma gondii
, and
Mycobacterium avium
complex infections. Rats latently infected with
P. carinii
were challenged with the MO-1 strain of
M. avium
and then immunosuppressed with corticosteroids for 7 weeks. At week 5 the RH strain of
T. gondii
was intraperitoneally injected. Organs were examined for the three pathogens after death or killing of the animals at week 7. Without treatment, rats challenged with
T. gondii
died with pulmonary
P. carinii
infection and disseminated
T. gondii
and
M. avium
infections. In order to assess the value of the model for evaluation of the activities of drugs, we administered by oral gavage for 7 weeks drugs or combinations of drugs selected for their individual efficacies against at least one pathogen. We found that clarithromycin with sulfamethoxazole, clarithromycin with atovaquone, roxithromycin with sulfamethoxazole or dapsone, and rifabutin with atovaquone were effective against the three infections, whereas PS-15 with dapsone and trimethoprim with sulfamethoxazole were active against
Toxoplasma
and
Pneumocystis
infections only. This triple-infection rat model offers a new tool for the simultaneous evaluation of the activities of drugs against three of the major opportunistic infections occurring in immunosuppressed individuals.
Disposition of the Acyclic Nucleoside Phosphonate (
S
)-9(3-Hydroxy-2-Phosphonylmethoxypropyl)Adenine
Authors: Bijsterbosch Martin K. , Smeijsters Louis J. J. W. , van Berkel Theo J. C.
Published: October 2018

The acyclic nucleoside phosphonate (
S
)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine [(
S
)-HPMPA] has been shown to be active against pathogens, like hepatitis B viruses and
Plasmodium
parasites, that infect parenchymal liver cells. (
S
)-HPMPA is therefore an interesting candidate drug for the treatment of these infections. To establish effective therapeutic protocols for (
S
)-HPMPA, it is essential that the kinetics of its hepatic uptake be evaluated and that the role of the various liver cell types be examined. In the present study, we investigated the disposition of (
S
)-HPMPA and assessed its hepatic uptake. Rats were intravenously injected with [
3
H](
S
)-HPMPA, and after an initial rapid distribution phase (360 ± 53 ml/kg of body weight), the radioactivity was cleared from the circulation with a half-life of 11.7 ± 1.4 min. The tissue distribution of [
3
H](
S
)-HPMPA was determined at 90 min after injection (when >99% of the dose cleared). Most (57.0% ± 1.1%) of the injected [
3
H](
S
)-HPMPA was excreted unchanged in the urine. The radioactivity that was retained in the body was almost completely recovered in the kidneys and the liver (68.4% ± 2.5% and 16.1% ± 0.4% of the radioactivity in the body, respectively). The uptake of [
3
H](
S
)-HPMPA by the liver occurred mainly by parenchymal cells (92.1% ± 3.4% of total uptake by the liver). Kupffer cells and endothelial cells accounted for only 6.1% ± 3.5% and 1.8% ± 0.8% of the total uptake by the liver, respectively. Preinjection with probenecid reduced the hepatic and renal uptake of [
3
H](
S
)-HPMPA by approximately 75%, which points to a major role of a probenecid-sensitive transporter in the uptake of (
S
)-HPMPA by both tissues. In conclusion, we show that inside the liver, (
S
)-HPMPA is mainly taken up by parenchymal liver cells. However, the level of uptake by the kidneys is much higher, which leads to nephrotoxicity. An approach in which (
S
)-HPMPA is coupled to carriers that are specifically taken up by parenchymal cells may increase the effectiveness of the drug in the liver and reduce its renal toxicity.
Defluorinated Sparfloxacin as a New Photoproduct Identified by Liquid Chromatography Coupled with UV Detection and Tandem Mass Spectrometry
Authors: Engler Michael , Rüsing Guido , Sörgel Fritz , Holzgrabe Ulrike
Published: October 2018

Photodegradation of sparfloxacin was observed by means of high-pressure liquid chromatography with UV detection and liquid chromatography coupled with UV detection and tandem mass spectrometry (LC-MS/MS). Three products were detected. Comparison with an independently synthesized derivative of sparfloxacin revealed the structure of one product which is believed to be 8-desfluorosparfloxacin. The second product is likely to be formed by the splitting off of a fluorine and a cyclopropyl ring. Thus, photodefluorination of quinolone antibacterial agents is found and proved for the first time by LC-MS/MS.
Cloning and Sequencing of the Gene Encoding Toho-2, a Class A β-Lactamase Preferentially Inhibited by Tazobactam
Authors: Ma Ling , Ishii Yoshikazu , Ishiguro Masaji , Matsuzawa Hiroshi , Yamaguchi Keizo
Published: October 2018

Escherichia coli
TUM1083, which is resistant to ampicillin, carbenicillin, cephaloridine, cephalothin, piperacillin, cefuzonam, and aztreonam while being sensitive to cefoxitin, moxalactam, cefmetazole, ceftazidime, and imipenem, was isolated from the urine of a patient treated with β-lactam antibiotics. The β-lactamase (Toho-2) purified from the bacteria hydrolyzed β-lactam antibiotics such as penicillin G, carbenicillin, cephaloridine, cefoxitin, cefotaxime, ceftazidime, and aztreonam and especially had increased relative hydrolysis rates for cephalothin, cephaloridine, cefotaxime, and ceftizoxime. Different from other extended-spectrum β-lactamases, Toho-2 was inhibited 16-fold better by the β-lactamase inhibitor tazobactam than by clavulanic acid. Resistance to β-lactams was transferred by conjugation from
E. coli
TUM1083 to
E. coli
ML4909, and the transferred plasmid was about 54.4 kbp, belonging to the incompatibility group IncFII. The cefotaxime resistance gene for Toho-2 was subcloned from the 54.4-kbp plasmid. The sequence of the gene was determined, and the open reading frame of the gene was found to consist of 981 bases. The nucleotide sequence of the gene (DDBJ accession no.
D89862
) designated as
bla
toho
was found to have 76.3% identity to class A β-lactamase CTX-M-2 and 76.2% identity to Toho-1. It has 55.9% identity to SHV-1 β-lactamase and 47.5% identity to TEM-1 β-lactamase. Therefore, the newly isolated β-lactamase designated as Toho-2 produced by
E. coli
TUM1083 is categorized as an enzyme similar to Toho-1 group β-lactamases rather than to mutants of TEM or SHV enzymes. According to the amino acid sequence deduced from the DNA sequence, the precursor consisted of 327 amino acid residues. Comparison of Toho-2 with other β-lactamase (non-Toho-1 group) suggests that the substitutions of threonine for Arg-244 and arginine for Asn-276 are important for the extension of the substrate specificity.
Postantibiotic Effect and Postantibiotic Sub-MIC Effect of Levofloxacin Compared to Those of Ofloxacin, Ciprofloxacin, Erythromycin, Azithromycin, and Clarithromycin against 20 Pneumococci
Authors: Spangler Sheila K. , Lin Gengrong , Jacobs Michael R. , Appelbaum Peter C.
Published: October 2018

The postantibiotic effect (PAE) (10 times the MIC of quinolones, 5 times the MIC of macrolides) and postantibiotic sub-MIC effect (PAE-SME) at 0.125, 0.25, and 0.5 times the MIC were determined for levofloxacin, ciprofloxacin, ofloxacin, erythromycin, azithromycin, and clarithromycin against 20 pneumococci. Quinolone PAEs ranged between 0.5 and 6.5 h, and macrolide PAEs ranged between 1 and 6 h. Measurable PAE-SMEs (in hours) at the three concentrations were 1 to 5, 1 to 8, and 1 to 8, respectively, for quinolones and 1 to 8, 1 to 8, and 1 to 6, respectively, for macrolides.
Antipneumococcal Activity of Grepafloxacin Compared to That of Other Agents by Time-Kill Methodology
Authors: Pankuch Glenn A. , Jacobs Michael R. , Appelbaum Peter C.
Published: October 2018

Time-kill studies compared the activities of grepafloxacin with those of ciprofloxacin, levofloxacin, sparfloxacin, amoxicillin-clavulanate, and clarithromycin against 12 pneumococcal strains. Grepafloxacin was bactericidal after 24 h against all strains at a concentration of ≤0.5 μg/ml, while sparfloxacin, levofloxacin, and ciprofloxacin were bactericidal at concentrations of ≤1.0, ≤2.0, and ≤8.0 μg/ml, respectively. Amoxicillin-clavulanate and clarithromycin were bactericidal at 2× the MIC after 24 h against 12 of 12 strains and against all 8 macrolide-susceptible strains, respectively.
In Vitro Activities of Clinafloxacin against Contemporary Clinical Bacterial Isolates from 10 North American Centers
Authors: Fuchs Peter C. , Barry Arthur L. , Brown Steven D.
Published: October 2018

Clinafloxacin was more active than ciprofloxacin against 4,213 aerobic and facultative anaerobic bacterial isolates from 10 medical centers, as tested by broth microdilution and disk diffusion methods. The percentage of 201 anaerobes susceptible to clinafloxacin by broth microdilution was comparable to cefoxitin. Our data support the proposed disk diffusion interpretive criteria for aerobic bacteria with 5-μg clinafloxacin disks.
Prophylaxis of
Plasmodium falciparum
Infection in a Human Challenge Model with WR 238605, a New 8-Aminoquinoline Antimalarial
Authors: Brueckner Ralf P. , Coster Trinka , Wesche David L. , Shmuklarsky Moshe , Schuster Brian G.
Published: October 2018

The prophylactic efficacy of WR 238605, a primaquine analog, was studied with a human
Plasmodium falciparum
challenge model. A single oral dose of 600 mg, administered 1 day prior to challenge, successfully protected three of four subjects. The fourth subject developed mild, oligosymptomatic malaria on day 31, with drug concentrations one-half of those in the protected individuals. WR 238605 appears to be a promising prophylactic drug for
P. falciparum
malaria.
Phase I Safety and Pharmacokinetics Study of Micronized Atovaquone in Human Immunodeficiency Virus-Infected Infants and Children
Authors: Hughes Walter , Dorenbaum Alejandro , Yogev Ram , Beauchamp Belinda , Xu Jing , McNamara James , Moye John , Purdue Lynette , van Dyke Russell , Rogers Michael , Sadler Brian , Group The Pediatric Aids Clinical Trials
Published: October 2018

A phase I dose-escalating safety and pharmacokinetic study evaluated an oral suspension of micronized atovaquone (m-atovaquone) in infants and children stratified into age groups from 1 month to 12 years of age. Dosages of 10, 30, and 45 mg/kg of body weight/day were evaluated as single daily doses over a period of 12 days. Steady-state concentrations in plasma were determined on day 12, and single postdose concentrations were measured on days 1, 3, 5, 7, 9, 13, 15, 18, 21, and 24. Prior studies with adults suggest that the average plasma atovaquone concentration of 15 μg/ml is associated with therapeutic success in more than 95% of patients with
Pneumocystis carinii
pneumonitis. The results showed m-atovaquone to be safe and well tolerated. Dosages of 30 mg/kg/day were adequate to achieve an average steady-state concentration of greater than 15 μg/ml in children ages 1 to 3 months and 2 to 12 years, but a dosage of 45 mg/kg/day was needed to reach this concentration in infants 3 to 24 months of age. The oral suspension of atovaquone is safe and well tolerated in children. A single daily dose of 30 mg/kg provides bioavailability considered adequate for therapy of
P. carinii
pneumonia, but infants between 3 and 24 months of age may require a dosage of 45 mg/kg/day.
Minocycline and Cefotaxime in the Treatment of Experimental Murine
Vibrio vulnificus
Infection
Authors: Chuang Yin-Ching , Ko Wen-Chien , Wang Shan-Tair , Liu Jien-Wei , Kuo Chih-Feng , Wu Jiunn-Jong , Huang Kun-Yen
Published: October 2018

We conducted an in vivo study with the mouse model of
Vibrio vulnificus
infection to evaluate the efficacies of therapy with minocycline or cefotaxime alone and in combination.
V. vulnificus
was introduced subcutaneously into the area over the right thigh. The inoculum size ranged from 1.0 × 10
3
to 1.2 × 10
8
CFU from experiment to experiment but was constant for all animals in the same experiment. Antibiotics were given intraperitoneally 2 h after the bacteria were inoculated. In experiments 1 to 4, the standard dose for humans was used to treat the infection, while in experiment 5, five times the standard dose for humans was used to treat the infection. In experiment 1, with a small inoculum of 5 × 10
3
CFU, all mice in the saline-treated control group and the cefotaxime-, minocycline-, and combined antibiotic-treated groups survived. In experiment 2, with a moderate inoculum of 1.2 × 10
5
CFU, all the mice in the three antibiotic-treated groups survived, while only two of nine mice in the control group survived. In experiment 3, with a large inoculum of 8.0 × 10
7
CFU, six of nine mice in the combined antibiotic-treated group survived, while only one of nine mice in the cefotaxime-treated group and none of the mice in the control and minocycline-treated groups survived. In experiment 4, with a large inoculum of 1.2 × 10
8
CFU, 8 of 20 mice in the combined antibiotic-treated group survived, while none of the 20 mice in the control group, the group treated with cefotaxime alone, and the group treated with minocycline alone survived. In experiment 5, in which mice were infected with a large inoculum of 6.6 × 10
7
CFU and treated with five times the standard human dose of antibiotics, 10 of 12 mice in the combined antibiotic-treated group survived, while only 4 of 12 mice in the minocycline-treated group, 1 of 12 mice in the cefotaxime-treated group, and none of the mice in the control group survived. In experiments 3 to 5, the difference in the survival rates between the combined antibiotic-treated and minocycline-treated groups was statistically significant (
P
< 0.05). These results indicate that combination therapy with cefotaxime and minocycline is distinctly more advantageous than therapy with the single antibiotic regimen for the treatment of severe experimental
V. vulnificus
infections.
Phenotypic Study of Resistance of β-Lactamase-Inhibitor-Resistant TEM Enzymes Which Differ by Naturally Occurring Variations and by Site-Directed Substitution at Asp
276
Authors: Caniça M. Manuela , Caroff Nathalie , Barthélémy Michel , Labia Roger , Krishnamoorthy Rajagopal , Paul Gérard , Dupret Jean-Marie
Published: October 2018

At this time an amino acid substitution at position 276 in the TEM-1 enzyme is associated with an additional substitution at position 69 in natural β-lactamase-inhibitor-resistant (IRT) β-lactamases. The effect of the Asn
276
→Asp substitution on resistance was assessed with the Asn276Asp variant, generated by site-directed mutagenesis. The mutant was resistant to β-lactamase inhibitors, but the MICs of amoxicillin combined with clavulanic acid or tazobactam were strikingly different for
E. coli
strains producing the Asn276Asp variant and those producing naturally occurring IRTs with single or double substitutions. The inhibitory effects of clavulanic acid and tazobactam were the same in IRTs with substitutions at position 69 (IRT-5 and IRT-6). The effect of clavulanic acid on the MICs of amoxicillin for the Asn276Asp variant was greater than that of tazobactam. In IRTs with double substitutions, at positions 69 plus 276 (IRT-4, IRT-7, and IRT-8) or 69 plus 275 (IRT-14), tazobactam was a more potent inhibitor than clavulanic acid. The effect of the Asn
276
→Asp substitution on the values of the kinetic constants and the concentration required to inhibit by 50% the hydrolysis of benzylpenicillin confirms that this single mutation is responsible for resistance to β-lactamase inhibitors. Molecular modeling of the Asn276Asp mutant shows that Asp
276
can form two salt bonds with Arg
244
close to the penicillin-binding cavity. The addition of the Asp
276
mutation to that preexisting at position 69 confers a higher selective advantage to bacteria, as shown by the reduction in β-lactamase inhibitor efficiencies of the double variants. Therefore, the emergence of multiple mutations in TEM β-lactamases by virtue of the use of β-lactamase inhibitors increases selection pressure resulting in the convergent evolution of resistant strains.
Effect of Metronidazole Resistance on Bacterial Eradication of
Helicobacter pylori
in Infected Children
Authors: Raymond J. , Kalach N. , Bergeret M. , Benhamou P. H. , Barbet J. P. , Gendrel D. , Dupont C.
Published: October 2018

A prospective study was performed with 23
Helicobacter pylori
-infected children (mean age, 9.5 ± 4.4 years) with clinical symptoms of gastritis and positive results of culture and histologic examination of gastric biopsy specimens to evaluate the influence of antibiotic resistance on eradication. Positive children were treated for 4 weeks with lansoprazole and for 2 weeks with either amoxicillin-metronidazole or spiramycin (a macrolide)-metronidazole. At endoscopy 1 month after the discontinuation of therapy, the eradication rate and improvement of histologically related gastritis were significantly dependent on the susceptibility or the resistance of the infecting organism to metronidazole (83 versus 17% and 88 versus 16.6%, respectively). Pretreatment determination of the susceptibility is appropriate in any anti-
H. pylori
regimen, including one with metronidazole.
β-Lactamases Responsible for Resistance to Expanded-Spectrum Cephalosporins in
Klebsiella pneumoniae
,
Escherichia coli
, and
Proteus mirabilis
Isolates Recovered in South Africa
Authors: Pitout J. D. D. , Thomson K. S. , Hanson N. D. , Ehrhardt A. F. , Moland E. S. , Sanders C. C.
Published: October 2018

Although resistance to the expanded-spectrum cephalosporins among members of the family
Enterobacteriaceae
lacking inducible β-lactamases occurs virtually worldwide, little is known about this problem among isolates recovered in South Africa. Isolates of
Klebsiella pneumoniae
,
Escherichia coli
, and
Proteus mirabilis
resistant to expanded-spectrum cephalosporins recovered from patients in various parts of South Africa over a 3-month period were investigated for extended-spectrum β-lactamase production. Antibiotic susceptibility was determined by standard disk diffusion and agar dilution procedures. Production of extended-spectrum β-lactamases was evaluated by using the double-disk test, and the β-lactamases were characterized by spectrophotometric hydrolysis assays and an isoelectric focusing overlay technique which simultaneously determined isoelectric points and general substrate or inhibitor characteristics. DNA amplification and sequencing were performed to confirm the identities of these enzymes. The
P. mirabilis
and
E. coli
isolates were found to produce TEM-26-type, SHV-2, and SHV-5 extended-spectrum β-lactamases. An AmpC-related enzyme which had a pI of 8.0 and which conferred resistance to cefoxitin as well as the expanded-spectrum cephalosporins was found in a strain of
K. pneumoniae
. This is the first study which has identified organisms producing different extended-spectrum β-lactamases from South Africa and the first report describing strains of
P. mirabilis
producing a TEM-26-type enzyme. The variety of extended-spectrum β-lactamases found among members of the family
Enterobacteriaceae
isolated from major medical centers in South Africa is troubling and adds to the growing list of countries where these enzymes pose a serious problem for antimicrobial therapy.
Use of a Continuous-Culture Biofilm System To Study the Antimicrobial Susceptibilities of
Gardnerella vaginalis
and
Lactobacillus acidophilus
Authors: Muli F. , Struthers J. K.
Published: October 2018

Gardnerella vaginalis
and
Lactobacillus acidophilus
have been shown to grow to high titers in a simple biofilm system. This system was used in the present investigation to compare the biofilm-eradicating concentrations (BECs) of amoxicillin, clindamycin, erythromycin, and metronidazole to standard tube MIC and minimum bactericidal concentration (MBC) results. With the lactobacillus, the BEC/tube MBC ratio was at least 16:1, while for
G. vaginalis
the ratio varied from 2:1 to 512:1. The simple continuous-culture system used in the present investigation is ideal for investigating the BEC for bacteria involved in complex ecological situations such as bacterial vaginosis and may be useful for the identification of the most effective and selective antibiotic therapy.
Pharmacokinetics and Safety of a New Parenteral Carbapenem Antibiotic, Biapenem (L-627), in Elderly Subjects
Authors: Kozawa Osamu , Uematsu Toshihiko , Matsuno Hiroyuki , Niwa Masayuki , Takiguchi Yoshiharu , Matsumoto Syouzou , Minamoto Masahiko , Niida Yoshito , Yokokawa Masahiro , Nagashima Satoru , Kanamaru Mitsutaka
Published: October 2018

The pharmacokinetics and tolerability of a new parenteral carbapenem antibiotic, biapenem (L-627), were studied in healthy elderly volunteers aged 65 to 74 years (71.6 ± 2.7 years [mean ± standard deviation],
n
= 5; group B) and ≥75 years (77.8 ± 1.9 years,
n
= 5; group C), following single intravenous doses (300 and 600 mg), and compared with those of healthy young male volunteers aged 20 to 29 years (23.0 ± 3.5 years,
n
= 5; group A). The agent was well tolerated in all three age groups. Serial blood and urine samples were analyzed for biapenem to obtain key pharmacokinetic parameters by both two-compartment model-dependent and -independent methods. The maximum plasma concentration and area under plasma concentration-versus-time curve (AUC) increased in proportion to the dose in all three groups. Statistically significant age-related effects for AUC, total body clearance, and renal clearance (CL
R
) were found, while elimination half-life (
t
1/2β
) and percent cumulative recovery from urine of unchanged drug (% UR) remained unaltered (
t
1/2β
, 1.51 ± 0.42 [300 mg] and 2.19 ± 0.64 [600 mg] h [group A], 1.82 ± 1.14 and 1.45 ± 0.36 h [group B], and 1.75 ± 0.23 and 1.59 ± 0.18 h [group C]; %UR, 52.6% ± 3.0% [300 mg] and 53.1% ± 5.1% [600 mg] [group A], 46.7% ± 7.4% and 53.0% ± 4.8% [group B], and 50.1% ± 5.2% and 47.1% ± 7.6% [group C]). A significant linear correlation was observed between the CL
R
of biapenem and creatinine clearance at the dose of 300 mg but not at 600 mg. The steady-state volume of distribution tended to be decreased with age, although not significantly. Therefore, the age-related changes in parameters of biapenem described above were attributable to the combination of decreased lean body mass and lowered renal function of the elderly subjects. However, the magnitude of those changes does not necessitate dosage adjustment in elderly patients with normal renal function for their age.