The Frequency Unexpected Antibodies at Kyungpook National University Hospital / 대한수혈학회지

BACKGROUND: Unexpected antibody screening and identification tests are very important pre-transfusion tests for preventing transfusion reactions. Nowadays, the column agglutination test is widely used in Korea. The results of many studies that used this method showed the decreased frequency of nonsignificant cold antibodies and an increased frequency of warm antibodies when compared with other studies that used the tube test or the microplate test. This study was performed in order to determine the accurate frequency and distribution of unexpected alloantibody by using the column agglutination test. METHODS: We analyzed the results from 32,218 antibody screening tests with using LISS/Coombs cards and ID-DiaCell I and II for the transfusion candidates and patients with hemolytic anemia who were seen at Kyungpook National University Hospital during a recent eight-year period. RESULTS: According to the results of the antibody screening test, 188 samples (0.58%) out of all 32,218 samples, were shown to be positive. Unexpected alloantibodies were detected in 86 patients (0.27%) with using the antibody identification test. The antibodies that were detected most frequently were anti-E (29 samples), followed by anti-D (8 samples), anti-M (8 samples) and anti-c (7 samples). CONCLUSION: The frequency and distribution of unexpected antibodies at our hospital are similar with those obtained in other Korean studies. The detection rates of warm antibodies, including Rh antibodies, were high. The proportion of Rh antibodies in patients with a gestation history was significantly higher than that in the patients without a gestation history. This study shows once again that pregnancy affects the antibodies and this supports the relationship between pregnancy and antibody formation.

Comparative Analysis of Bronchoalveolar Lavages in Interstitial Lung Diseases / 대한진단검사의학회지

BACKGROUND: This study was purposed to find out the differences in the lymphocyte subsets and differential cell counts of the bronchoalveolar lavage (BAL) fluid in patients with interstitial lung disease (ILD) and to analyze the differences according to their ages, gender and smoking habits. METHODS: BAL fluid samples of 141 ILD patients were examined for lymphocyte subsets and differential cell counts, and the differences among the patients were analyzed according to their diseases. Then, within the three most common disease groups, the differences were further analyzed by the age, gender and smoking habit of the patients. RESULTS: There were no statistically significant differences in total cell counts (per millimeters of BAL fluid) among the patient groups with each ILD. However, significant differences were observed in the percentages of neutrophils, lymphocytes, eosinophils, and macrophages of BAL fluid. Also, in lymphocyte subset analyses, the percentages of total T cells, B cells, CD4+ T cells, CD8+ T cells, CD4/CD8 T cell ratios, and NK cells were significantly different among the patients with each ILD. However, within the same disease group, there were no differences in differential cell counts and lymphocyte subset analyses according to the age, smoking habit, and gender of the patients. CONCLUSIONS: Although the age, smoking habit and gender did not have an effect on the BAL fluid analyses among the patients with the same ILD, there were significant differences among the patients with each ILD; therefore, the differential cell counts and lymphocyte subset analyses of BAL fluid can be useful in differential diagnosis for determining the types of ILD.

Evaluation of BiosewoomTM Real-Q Cytomegalovirus Quantification kit for Cytomegalovirus Viral Load Measure / 대한진단검사의학회지

BACKGROUND: Rapid and accurate laboratory tests are essential to detect cytomegalovirus (CMV) infections in solid organs and haematopoietic stem cell transplant recipients. We assessed the realtime quantitative PCR (RQ-PCR) technology for its usefulness in detecting CMV DNA. METHODS: We evaluated the analytical performance of CMV RQ-PCR using Real-Q Cytomegalovirus Quantification kit (BioSewoom Inc., Korea). To evaluate its clinical utility, we also compared it to pp65 antigenemia test, an immunostaining method, on 343 samples of total 84 patients, including 63 transplant recipients. RESULTS: The detection limit of RQ-PCR was 63 copies/mL and none of hepatitis B virus, hepatitis C virus, or human immunodeficiency virus showed a cross-reactivity with CMV. Total coefficient of variation (CV) was 10.4-19.5%. It detected CMV DNA in a linear range from 1 x 10(2) to 5 x 10(11) copies/mL (P<10(-13), R2=0.9994). The qualitative positive rates of pp65 antigenemia test and RQ-PCR were 4.7%, 16.3%, respectively and concordance rate between the two tests was 84.8% (K=0.221, P<10(-6)). In comparison of quantitative results, the correlation between two tests was significant (r=0.45, P<10(-17)). In comparison among three groups by pp65 antigen level, CMV DNA level obtained with RQ-PCR increased significantly (P<10(-3) and P<10(-7), respectively). CONCLUSIONS: The RQ-PCR is easier to perform than the immunostaining method, has good analytical performance and reflects the blood level of viral DNA well. It may be a new method substituting the pp65 antigenemia test. Further studies determining RQ-PCR value starting pre-emptive therapy will be required.

Evaluation of BiosewoomTM Real-Q Cytomegalovirus Quantification kit for Cytomegalovirus Viral Load Measure / 대한진단검사의학회지

BACKGROUND: Rapid and accurate laboratory tests are essential to detect cytomegalovirus (CMV) infections in solid organs and haematopoietic stem cell transplant recipients. We assessed the realtime quantitative PCR (RQ-PCR) technology for its usefulness in detecting CMV DNA. METHODS: We evaluated the analytical performance of CMV RQ-PCR using Real-Q Cytomegalovirus Quantification kit (BioSewoom Inc., Korea). To evaluate its clinical utility, we also compared it to pp65 antigenemia test, an immunostaining method, on 343 samples of total 84 patients, including 63 transplant recipients. RESULTS: The detection limit of RQ-PCR was 63 copies/mL and none of hepatitis B virus, hepatitis C virus, or human immunodeficiency virus showed a cross-reactivity with CMV. Total coefficient of variation (CV) was 10.4-19.5%. It detected CMV DNA in a linear range from 1 x 10(2) to 5 x 10(11) copies/mL (P<10(-13), R2=0.9994). The qualitative positive rates of pp65 antigenemia test and RQ-PCR were 4.7%, 16.3%, respectively and concordance rate between the two tests was 84.8% (K=0.221, P<10(-6)). In comparison of quantitative results, the correlation between two tests was significant (r=0.45, P<10(-17)). In comparison among three groups by pp65 antigen level, CMV DNA level obtained with RQ-PCR increased significantly (P<10(-3) and P<10(-7), respectively). CONCLUSIONS: The RQ-PCR is easier to perform than the immunostaining method, has good analytical performance and reflects the blood level of viral DNA well. It may be a new method substituting the pp65 antigenemia test. Further studies determining RQ-PCR value starting pre-emptive therapy will be required.

TT Virus (TTV) Infection in General Population, Chronic Liver Diseases, Hemodialysis, and Transfused Patients / 대한임상미생물학회지

BACKGROUND: TT virus (TTV), isolated initially from a Japanese patient with posttransfusion hepatitis of unknown etiology, was suggested to be a new causative agent of hepatitis. However, it has been found to infect both healthy and diseased individuals and numerous studies have raised questions about its pathogenic role in hepatitis. In order to study its prevalence and clinical impact on hepatitis, we assessed the frequency of TTV DNA. METHODS: Serum samples were obtained from 60 cases of the controls, 77 cases of chronic liver diseases, 44 cases of hemodialyzed patients, and 65 cases of transfused patients. TTV DNA was detected using nested polymerase chain reaction and alanine aminotransferase (ALT), aspartate aminotransferase (AST), and hepatitis B surface antigen (HBsAg) were measured. RESULTS: TTV DNA was detected in 41.7% of the controls, 51.9% of patients with chronic liver diseases, 68.2% of hemodialyzed patients and 61.5% of transfused patients. Comparison between patients with or without TTV revealed no significant differences in AST, ALT, and HBsAg test results. CONCLUSION: The prevalance of TTV infection in patients with chronic liver diseases was similar to that in the controls. TTV infection was not related to abnormal liver function findings and HBsAg positivity. We found no relationship between TTV infection and chronic liver diseases.

In Vitro Antimicrobial Activities of Silver Nanoparticles (NANOVER) against Clinical Isolates / 대한임상미생물학회지

BACKGROUND: Silver has extensive and powerful antimicrobial activities and silver-containing materials have been widely used in many medical fields. Recently nanoparticulate silver was developed and it is superior to other types of silver in the antimicrobial activity and cytotoxicity. There have been no data from Korea on its antimicrobial activity, and we evaluated the antimicrobial activity of NANOVER against common clinical isolates. METHODS: Minimum inhibitory concentrations (MICs) of NANOVER for clinical isolates were determined using the agar dilution method of Clinical and Laboratory Standard Institute. A total of 45 isolates were tested including 4 reference strains (Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Enterococcus faecalis ATCC 29212), 5 strains of methicillin-resistant S.aureus (MRSA), 7 strains of methicillin-sensitive S. aureus (MSSA), 14 strains of E.coli,and 15 strains of P. aeruginosa. RESULTS: The MICs of S.aureus to NANOVER were under 12.5 microgram/mL regardless of the methicillin sensitivity or resistance. The other isolates showed the MICs under 12.5 to 6.25 microgram/mL. CONCLUSION: NANOVER has strong and extensive antimicrobial activities to common clinical isolates including those resistant to other antimicrobials.

Age-Related Decrease and a Simple Flow Cytometric Assay of Neutrophil Function / 대한진단검사의학회지

BACKGROUND: We intended to confirm a decline in neutrophil function with aging and to devise a simple neutrophil function test protocol for use in a clinical setting. Reversely, the reliability of this protocol was to be verified by detectability of a decline in neutrophil function with aging. METHODS: Whole blood samples from young (thirties, N=32) and old (sixties, N=32) healthy subjects were incubated with the 7-aminoactinomycin D stained Escherichia coli. The mixture was stained by dihydrorhodamine 123 as an oxidative probe. Two kinds of fluorescence were measured by flow cytometry. RESULTS: Phagocytosis was declined with aging as indicated by a decrease in the percentage (form 28.2+/-9.5% to 21.9+/-10.9%, P<0.05) and the mean fluorescence intensity (MFI) ratio (from 1.67+/-0.27 to 1.51+/-0.27, P<0.05). Oxidative burst had a trend toward a decrease with aging, but the differences were not significant (percentage: from 35.3+/-13.2% to 32.1+/-14.1%, P=0.36; MFI ratio: from 5.26+/-3.23 to 5.08+/-3.55, P=0.84). CONCLUSIONS: The devised protocol in this study could detect a significant decline in neutrophil function with aging, and this protocol may be useful for the assessment of neutrophil function in a clinical setting.

Association of Myocardial Infarction and Chlamydophila pneumoniae Infection / 대한임상미생물학회지

BACKGROUND: Although there are growing evidences linking Chlamydophila pneumoniae infection to myocardial infarction, it remains controversial. The authors intended to assess whether C. pneumoniae infection is associated with myocardial infarction. METHODS: Sera and peripheral mononuclear cells (PMNCs) were collected from 54 cases of acute myocardial infarction (MI), 33 cases of old MI, and 60 normal controls. Anti-C.pneumoniae IgG and IgM antibodies were measured using a microimmunofluorescence (mIF) method, and C.pneumoniae DNA was detected using polymerase chain reaction (PCR). RESULTS: Seropositivity of anti-C.pneumoniae IgM antibody by mIF was shown 5.0% in control group, 29.6% (OR=8.00) in the acute MI and 6.1% (OR=1.23) in old MI group. Seropositivity of anti C.pneumoniae IgG antibody were 60.0 % in control group, 92.6% (OR=8.33) in the acute MI and 87.9% (OR= 4.83) in old MI group. The antibody titers in the acute MI and old MI group tended to be higher compared to those in control group. No C.pneumoniae DNA was detected in any case by PCR. CONCLUSION: The seropositivity and antibody titers were significantly higher in the acute MI and old MI group than in control group, suggesting that C.pneumoniae infection may be a risk factor for myocardial infarction.

Association of Chlamydophila pneumoniae, Cytomegalovirus, Helicobacter pylori and HIV Infections with Myocardial Infarction / 대한임상미생물학회지

BACKGROUND: There is some evidence linking the infections with common organisms such as Chlamydophila pneumoniae, cytomegalovirus (CMV), Helicobacter pylori and HIV to myocardial infarction (MI). We had performed a serologic study to assess whether C.pneumoniae, CMV, H. pylori and HIV infections are associated with MI. METHODS: Serum samples were obtained from 54 cases of acute MI, 33 cases of old MI, and 60 normal controls. C-reactive protein (CRP) as an inflammation marker was measured and antibodies to C.pneumoniae, CMV, H.pylori and HIV were assayed by ELISA. Odds ratios (OR) were calculated against control group. RESULTS: CRP was significantly higher in the acute MI and old MI group. ORs of C.pneumoniae infection increased considerably in the acute MI (IgM 1.57, IgG 4.80) and old MI group (IgM 2.42, IgG 5.18). ORs of CMV infection were 3.30 in the acute MI and 5.12 in old MI group. ORs of H. pylori infection showed below 1 in the acute MI and old MI. Anti-HIV antibody showed all negative result in three groups, so OR could not be calculated. CONCLUSION: C.pneumoniae and CMV infections appear to be risk factors for MI.

A Case of Pichia anomala Detected Incidentally in Peripheral Blood Smear / 대한임상미생물학회지

Nosocomial opportunistic infections including fungal infections continue to increase with a longer survival of immunocompromised patients. Disseminated candidiasis is the most common nosocomial fungal infection and the frequency of isolation of non-Candida albicans organisms besides C.albicans is increasing as causative organisms. We detected numerous yeast cells incidentally in a peripheral blood smear of an infant with congenital heart disease who was treated with total parenteral nutrition and catheterization, and had a history of antibiotics use during a long hospitalization period. Pichia anomala was isolated from the blood and pleural effusion.

Estimate of Thrombopoiesis by Flow Cytometric Analysis of Reticulated Platelets in Patients with Severe Thrombocytopenia / 대한진단검사의학회지

BACKGROUND: Analysis of reticulated platelets (RPs) is useful for discriminating the causes of thrombocytopenia and monitoring the thrombopoiesis. In the patients with severe thrombocytopenia, we evaluated the thrombopoiesis-discriminating ability of several indices applying forward scatter (FSC) and thiazole orange (TO) fluorescence in addition to the percentage of reticulated platelets (RPs%). METHODS: Forty cases with decreased thrombopoiesis, twenty cases with increased thrombopoiesis and twenty cases with liver cirrhosis were selected. By flow cytometry with two analytic methods, dependent on or independent of the staining of CD41-PE as a platelet marker, the primary parameters including RPs% were measured and the applied parameters were calculated from them. And we compared the diagnostic efficiency of each parameter and analyzed the purity of platelet light scatter gate. RESULTS: The purity of platelet light scatter gate was significantly lower in patients with severe thrombocytopenia than in healthy persons with normal platelet counts (P<10(-6)), so the use of CD41-PE for platelet gating improved the diagnostic efficiency of RPs%. Compared to the primary parameters, the applied parameters originated from RPs%, FSC and TO fluorescence improved diagnostic efficiency significantly (RPs%: 55%, RPs%xs delta MFI: 80%) between decreased and increased thrombopoiesis groups. CONCLUSIONS: In the patients with severe thrombocytopenia, the estimate of the thrombopoiesis by a flow cytometric analysis can be more predictable by using platelet markers and by considering the fluorescence intensity of TO together with the RPs%.

Relation among the Tests and Comparison of Positivity of Tests for Multi-Drug Resistance in Newly Diagnosed Acute Leukemia / 대한진단검사의학회지

BACKGROUND: The expression of multi-drug resistance (MDR) in acute leukemia was known to decrease the outcome of chemotherapy and to increase the rate of relapse. Of the mechanism of MDR, the most well known is P-glycoprotein (P-gp) encoded by the mdr1 gene. There are MDR genes, P-gp tests and drug efflux function tests for the clinical measurement of MDR. To assess the clinical usefulness and MDR expression status in acute leukemia, MDR tests were performed. METHODS: MDR expression was assessed by MDR1 mRNA RT-PCR and flow cytometry measuring P-gp and daunorubicin (DNR) efflux in 77 patients with newly diagnosed acute leukemia (AL) including 48 acute myeloid leukemia (AML), 16 acute lymphoblastic leukemia (ALL) and 13 acute mixed-lineage leukemia (AMLL). The CD34 surface-marker study was also done by flow cytometry. The result of chemotherapy was evaluated by the percentage of remnant bone marrow (BM) blasts. RESULTS: The positivity of MDR1 mRNA was 57.1% (44/77) in AL, 61.5% (8/13) in AMLL, 60.4% (29/48) in AML, and 43.8% (7/16) in ALL. The positivity of P-gp expression was 36.5% (27/74) in AL and 100% in AML. The positivity of the DNR efflux test was 30.1% (22/73) in AL, 40.0% (18/45) in AML, 23.1% (3/13) in AMLL, and 6.7% (1/15) in ALL. There was a significant correlation between MDR1 mRNA and P-gp expression and between MDR1 mRNA and CD34 expression in AML. There was a significant correlation between the percentages of residual blast cells in BM and P-gp expression (P=0.039, r=0.312). CONCLUSIONS: It can be clinically useful to perform the mdr1 gene and P-gp test simultaneously both in newly diagnosed acute leukemia patients. The effectiveness of tests for MDR can be helpful to predict the outcome of chemotherapy.

Detection of Ureaplasma urealyticum and Mycoplasma hominis in Pregnant Women Using MYCOFAST(R) Evolution 2 and PCR / 대한임상미생물학회지

BACKGROUND: The associations between preterm labor or premature rupture of membrane (PROM) and urogenital infections of pregnant women are reported. Ureaplasma urealyticum and Mycoplasma hominis are well known as important pathogens of urogenital infections in pregnant women. In routine clinical laboratory, conventional culture for these microorganisms has not been made generally because of the requirements for strict growth condition. MYCOFAST(R) Evolution 2 is an easy and rapid liquid microculture method using metabolism of these microorganisms. Author investigated the relationship between U. urealyticum or M. hominis infections and preterm labor or PROM by MYCOFAST Evolution 2 and PCR. Also it was reviewed that the possibility of substitution of MYCOFAST Evolution 2 for conventional culture method by comparing with PCR methods. METHODS: This study was done on 91 pregnant women. They were composed of two groups; group I(n=48) had full-term delivery and group II(n=43) had preterm labor or PROM before the 37th week.Two cervical swabs were made each time. One was used for MYCOFAST(R) Evolution 2 and the other for PCR. RESULTS: The positivity of U. urealyticum was 39.6% in group Iand 58.1% in group IIby MYCOFAST Evolution 2 and 39.6% and 58.1% by PCR method, respectively. The positivity of M. hominis was 4.2% in group Iand 11.6% in group IIby MYCOFAST Evolution 2 and 4.2% and 7.0% by PCR method, respectively. The positivity of U. urealyticum and M. hominis in group IIwas higher than that in group Ibut was not significant statistically. The concordance rates between two methods were 86.8% for U. urealyticum and 97.8% for M. hominis. It showed good correlation between two methods (U. urealyticum, r=0.736; M. hominis, r=0.835). CONCLUSIONS: The infections of U. urealyticum and M. hominis were related to preterm labor or PROM. Considering vertical transmission to fetus or neonates resulting in perinatal morbidity or mortality, the detection of these microorganisms is important. MYCOFAST(R) Evolution 2 was an easy, rapid and reliable method substituting conventional culture method.

Clinical Utility of Reticulocyte Parameters in the Early Detection of Hematopoietic Engraftment After Stem Cell Transplantation / 대한진단검사의학회지

BACKGROUND: Allogeneic or autologous bone marrow transplantation (BMT) or peripheral blood stem cell transplantation (PBSCT) has been settled a modality of treatment in hematologic malignantdisorders or solid tumors. Because engraftment or not was important for the direction of treatment and prognosis of the patients, various methods, judging it early were groped. Instead of an absoluteneutrophil count (ANC) or platelet count in PB, we used reticulocyte parameters as early predictors of hematopoietic engraftment. METHODS: We measured the ANC with reticulocyte parameters daily in 25 patients receiving allogeneic BMT or PBSCT (n=17, 30.82+/-9.97 years old) and autologous PBSCT (n=8, 30.63+/-8.55 years old) from January 2002 to February 2003 in Kyungpook National University Hospital. Wedefined erythroid engraftment as the first day of a mean corpuscular volume of reticulocyte (MCVr)>or=105 fL and immature reticulocyte fraction (IRF) >or=10% in the second rising peak and myeloid engraftment as the first day of ANC >or=500/microL. RESULTS: The erythroid engraftment occurred after a mean time of 16.24+/-4.16 days in allogeneic graft and 14.00+/-3.55 days in autologous graft and the myeloid engraftment occurred 17.94+/-3.23 days and 15.00+/-2.78 days, respectively. In the allogeneic graft, the erythroid engraftment occurred earlier than the myeloid engraftment (P=0.03). In the autologous graft, the erythroid engraftment preceded the myeloid engraftment; however, it was not statistically significant (P=0.47). Among 3 cases, wherein the erythroid engraftment occurred later than the myeloid engraftment in allogeneic graft, 2cases were ABO-incompatible PBSCT. CONCLUSIONS: Considering that the successive increase of immature reticulocytes preceded that of ANC in most cases, we concluded that as an early indicator of hematopoietic engraftment, reticulocyte parameters such as IRF and MCVr were useful especially observing them simultaneously.

Detection by Flow Cytometry of Antibodies against Neutrophil Antigens Expressed by Long Incubation / 대한진단검사의학회지

BACKGROUND: We investigated the interactions between spontaneous apoptosis-induced neutrophils and autoantibodies with attention to the reactivities of each autoantibody against intracellular antigenssuch as the antinuclear antibody (ANA) and the anti-neutrophil cytoplasmic antibody (ANCA) and the applicability as a conventional test for autoantibody detection. METHODS: The 127 serum samples from patients with autoimmune disease were mixed with whole blood from healthy donors and incubated for 20 hours. The bound antibody against substrate neutrophils was detected with anti-IgG-FITC by flow cytometry. The results of this anti-long incubated neutrophil antibody (ALINA) testing were compared with ANA, ANCA and clinical manifestations. RESULTS: The positivity rate was significantly higher in the 20 hour incubation than that of a 30 minute incubation (100% and 18%, respectively; P<0.000005). Agreement analyses between ANCA and ALINA (k=0.34) and between ANA and ALINA (k=0.39) were poor. In comparison, among the autoimmune diseases, systemic lupus erythematosus had a significantly higher ALINA positivity rate than did other diseases (P<0.000005). In patients with SLE, higher mean fluorescence intensity was significantly associated with the presence of lupus nephritis (11/12 cases vs. 2/10 cases, P<0.005). CONCLUSIONS: We detected antibodies against neutrophil antigens expressed by long incubation with patient sera. Those detected autoantibodies were significantly associated with SLE, especially lupus nephritis. Therefore, further studies are necessary to devise optimal protocols and to clarify specificities for detected autoantibodies or their target antigens.

Detection by Flow Cytometry of Antibodies against Neutrophil Antigens Expressed by Long Incubation / 대한진단검사의학회지

BACKGROUND: We investigated the interactions between spontaneous apoptosis-induced neutrophils and autoantibodies with attention to the reactivities of each autoantibody against intracellular antigenssuch as the antinuclear antibody (ANA) and the anti-neutrophil cytoplasmic antibody (ANCA) and the applicability as a conventional test for autoantibody detection. METHODS: The 127 serum samples from patients with autoimmune disease were mixed with whole blood from healthy donors and incubated for 20 hours. The bound antibody against substrate neutrophils was detected with anti-IgG-FITC by flow cytometry. The results of this anti-long incubated neutrophil antibody (ALINA) testing were compared with ANA, ANCA and clinical manifestations. RESULTS: The positivity rate was significantly higher in the 20 hour incubation than that of a 30 minute incubation (100% and 18%, respectively; P<0.000005). Agreement analyses between ANCA and ALINA (k=0.34) and between ANA and ALINA (k=0.39) were poor. In comparison, among the autoimmune diseases, systemic lupus erythematosus had a significantly higher ALINA positivity rate than did other diseases (P<0.000005). In patients with SLE, higher mean fluorescence intensity was significantly associated with the presence of lupus nephritis (11/12 cases vs. 2/10 cases, P<0.005). CONCLUSIONS: We detected antibodies against neutrophil antigens expressed by long incubation with patient sera. Those detected autoantibodies were significantly associated with SLE, especially lupus nephritis. Therefore, further studies are necessary to devise optimal protocols and to clarify specificities for detected autoantibodies or their target antigens.

Phenotypes and Interpretive Reading of Antimicrobial Susceptibility Tests for Clinical Isolates of Several Species / 대한임상미생물학회지

BACKGROUND: In recent years, knowledge of bacterial resistance to antimicobials has expanded in important ways. Availability of an increasing number of antibiotics allows more precise individualization of resistance phenotypes and recording susceptibility results as patterns or phenotypes is valuable for both surveillance and patient care. If the patterns of resistance to panels of related antimicrobials are considered the underlying mechanisms can often be inferred. And the inferred mechanisms make the clinician to be advised to use alternative treatment. Interpretation of resistance phenotypes is based on the comparison of clinical isolates with prototype susceptible bacteria belonging to the same species. But interpretative reading of antimicrobial susceptibility tests requires an immense knowledge of antibiotics. Such interpretative reading is best achieved by computerized expert systems. METHODS: The authors attempt to determine phenotypes for the clinically isolated strains for each class of drugs tested by the Vitek 2 systemTM(bioMerieux, Marcy I'Etoile, France) using the Advanced Expert SystemTM(AES, bioMerieux, Marcy I'Etoile, France). A total of 91, 107, 89, 65, 251, 113, 47, 33, 23, 122 and 110 isolates of Staphylococcus aureus, coagulase negative staphylococci, Enterococcus faecalis, Enterococcus facium, Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, Enterobacter cloacae, Enterobacter aerogenes, Pseudomonas aeruginosae and Acinetobacter baumannii, were examined respectively. RESULTS: Biological correction based on the phenotype was recommended from 2.2% of E. faecalis to 46.8% of S. marcescens and therapeutic correction, from 7.3% of A. baumannii to 60.9% of E. aerogenes. A total of 25, 26, 18, 19, 22, 22, 15, 15, 17, 19, 19 phenotypes of S. aureus, coagulase negative staphylococci, E. faecalis, E. facium, E. coli, K. pneumoniae, S. marcescens, E. cloacae, E. aerogenes, P. aeruginosa and A. baumannii, were detected respectively. Association of resistance mechanism from S. aureus, coagulase negative staphylococci, E. coli, K. pneumoniae, S. marcescens, show 10, 11, 6, 4 and 3 pairs from resistant phenotypes, respectively. CONCLUSION: Vitek AES potentially provides a tool to assist the development of antimicrobial susceptibility interpretation in the clinical microbiology laboratory. The inferred mechanisms make the clinician to be advised to use alternative treatment.