Parameterization of inoculum effect via mathematical modeling: aminoglycosides against Staphylococcus aureus and Escherichia coli

Inoculum effect describes the inoculum size dependent changes in minimum inhibitory concentrations (MIC) exhibited by antibiotic-bacterium combinations demonstrating such effect. Traditionally, inoculum effect has been loosely defined based on the extent of increase in the MIC with respect to the increase in inoculum size. In most studies, assessment of MIC data has relied on the arbitrary selection of a point of reference for both baseline MIC and inoculum size. More importantly, this conventional method of assessment does not permit information conveyed in a complete MIC versus inoculum size profile to be fully explored. To undertake these issues, a mathematical model was developed for the description of the entire inoculum effect profile. With the employment of three key parameter estimates, i.e., the baseline MIC, the threshold inoculum size at which the increase in MIC commences, and the rate of increase in MIC with respect to inoculum size, both the shape and location of the profile could be adequately defined. To verify the application of this model, a series of four aminoglycosides were tested against standard strains of E. coli and S. aureus. Results showed a good degree of organism specificity and antibiotic-class dependency of the inoculum effect profiles. Analysis of the parameter estimates obtained provided further support for these observations. In conclusion, the mathematical model developed in the present study adequately described the inoculum effect exhibited by the various aminoglycoside-bacterium combinations tested. The parameter estimates generated by the modeling approach allowed comparison and quantitative analysis of the inoculum effect profiles with minimal difficulties.

Mitral insufficiency as a complication of acute myocardial infarction and left ventricular remodeling

The presence of mitral insufficiency after acute myocardial infarction (AMI) often leads to hemodynamic impairment and heart failure. This study was designed to examine the relationship between mitral regurgitation (MR), an indicator of mitral insufficiency, and the course of recovery from AMI. We evaluated the course of MR after AMI in 223 patients by color Doppler echocardiography. MR was detected in 21% (47/223) of patients at the onset of AMI, and developed in 18% (40/223) of patients during follow-up. Patients were grouped according to the course of MR as well as the success of acute recanalization therapy. No correlation was observed between the presence or course of MR and the site of infarction. The incidence of successful recanalization was higher in patients with MR that improved during follow-up than in patients with MR that was unchanged or that worsened during follow-up. Although no significant differences in hemodynamic variables were noted among the groups at admission, the group with unsuccessful recanalization and unimproved MR (BS-) showed a significantly greater left ventricular end-diastolic diameter (LVDd), left ventricular end-systolic diameter, and left ventricular end-diastolic volume (LVEDV) as well as a lower left ventricular ejection fraction than patients with successful recanalization and no MR (CS+) during the convalescent period. The extent of change in LVDd and LVEDV between admission and convalescence was significantly greater in the BS(-) group than in the CS(+) group. The results suggest that successful recanalization after AMI reduces the incidence of MR. Acute recanalization therapy after AMI may prevent left ventricular remodeling, resulting in a secondary improvement of MR.

Unilateral cleft lip repair without making incisions on the lip surface. A modified Millard operation

In clinical and anatomical studies carried out during 1986-1990, two new findings were identified: a small spade-shaped myocutaneous tag which can often be found at the medial side of the cleft near the columella base and the levator septi nasi muscle which draws the cleft side of the philtrum upwards. With the full use of the two findings, a method of unilateral cleft lip repair without making incisions on the lip surface was developed. Since 1986, 52 cases of unilateral cleft lip have been repaired with this method. The early and late results were gratifying.