Prevalence and characteristics of Escherichia coli sequence type 131 and its H30 and H30Rx subclones: a multicenter study from Korea.

We investigated the prevalence and characteristics of Escherichia coli sequence type 131 (ST131) and its subclones among 268 E. coli isolates. The isolates were collected from 21 Korean hospitals without use of selection criteria and were screened for ST131 status by PCR. ST131 isolates were characterized for extended-spectrum ß-lactamase variants, fluoroquinolone resistance genes, plasmid addiction systems, and replicon types. The collection's 57 identified ST131 isolates (21% of 268) were distributed disproportionately by clonal subset, as follows: 21 (37%) H30Rx, 27 (47%) H30 non-Rx, and 8 (14%) non-H30. Most (93%) ST131 isolates were ciprofloxacin resistant, and all H30 isolates had the same 5 nonsynonymous mutations in gyrA, parC, and parE. Twenty (95%) of H30Rx isolates harbored CTX-M-15, whereas only 14 (52%) of H30 non-Rx isolates harbored CTX-M-14 or CTX-M-27. Most (97%) ST131 isolates harbored IncF plasmids, but vagCD was confined exclusively to H30Rx. Our findings suggest that the distinctive characteristics of H30Rx isolates could have contributed to this subclone's recent epidemiologic success.

Aminoglycoside susceptibility profiles of Enterobacter cloacae isolates harboring the aac(6')-Ib gene.

The aminoglycoside 6'-N-acetyltransferases of type Ib (aac(6')-Ib) gene confers resistance to amikacin, tobramycin, kanamycin, and netilmicin but not gentamicin. However, some isolates harboring this gene show reduced susceptibility to amikacin. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) recommends a revision of the phenotypic description for isolates harboring the aac(6')-Ib gene. In this study, we determined the aminoglycoside susceptibility profiles of 58 AAC(6')-Ib-producing Enterobacter cloacae isolates. On the basis of the CLSI and EUCAST breakpoints, a large proportion (84.5% and 55.2%, respectively) of these 58 isolates were found to be susceptible to amikacin. However, among the isolates that were shown to be anikacin-susceptible according to the CLSI and EUCAST breakpoints, only 30.6% and 18.8% isolates, respectively, could be considered to have intermediate resistance on the basis of the EUCAST expert rules. Further studies should be conducted to determine the aminoglycoside susceptibility profiles of aac(6')-Ib-harboring isolates from various geographic regions and to monitor the therapeutic efficacy of amikacin in infections caused by these isolates.

[Performance characteristics of glycated albumin and its clinical usefulness in diabetic patients on hemodialysis].

BACKGROUND: The HbA1c has been considered to underestimate glucose level in diabetic patients on hemodialysis, therefore, glycated albumin (GA) was recently introduced to assess the glycemic control for those cases. We evaluated the performance of GA assay kit of Lucica GA-L (Asahi Kasei Pharma Co., Japan) and compare it with HbA1c for estimating glucose levels. METHODS: Tests for precision, linearity and interference were performed and reference interval was determined. Thirty eight of non-hemodialysis and seventy of hemodialysis patients were recruited, whose glucose levels of three-, two- and one-month prior to this study were available for calculating weighted means of glucose (WMGs). The correlation coefficients and the slopes of regression equation between WMG and HbA1c or GA were compared between two groups. Multiple linear regression analyses were used to determine significant predictor for HbA1c and GA. RESULTS: Total CV was 2.2% at concentration of 13.7% and 2.8% at 24.6%. The dilution curve between 15.7% and 62.1% was linear. Reference intervals were 10.0% to 16.5% for male and 11.4% to 17.6% for female. The correlation coefficients between WMG and GA were 0.682-0.713 in hemodialysis and 0.640-0.677 in non-hemodialysis. Those between WMG and HbA1c were 0.568-0.625 in hemodialysis and 0.735-0.783 in non-hemodialysis. The slopes of regression equation between GA and WMG in hemodialysis were 0.080-0.090 and 0.130-0.147 in non-hemodialysis. Those between HbA1c and WMG in hemodialysis were 0.012-0.014 and 0.029-0.032 in non-hemodialysis. GA was not influenced by hemodialysis status while HbA1c was. CONCLUSIONS: The claimed performance characteristic of Lucica GA-L were verified. WMG were better reflected by GA rather than HbA1c in patients on hemodialysis.

[Comparison of quantitative results among two automated Rapid Plasma Reagin (RPR) assays and a manual RPR test].

BACKGROUND: We compared two automated Rapid Plasma Reagin (RPR) assay kits with a manual RPR assay kit to evaluate the possibility of using the two automated RPR assays as an alternative to the manual RPR assay for a quantitative monitoring. METHODS: One hundred eighty-five samples were analyzed, including 16 sera from patients with primary, secondary, and latent syphilis. Measured RPR unit (R.U.) values of two automated RPR assay kits, Mediace RPR (Sekisui Chemical Co., Ltd, Japan) and HBi Auto RPR (HBI Co., Ltd, Korea), were compared with the RPR titers of Macro-Vue RPR card test (Becton Dickinson BD Microbiology systems, USA). As a confirmatory test, Anti-Treponema pallidum EUROLINE WB (IgG) and Anti-Treponema pallidum EUROLINE WB (IgM) (Euroimmun, Germany) were used. RESULTS: There was a prozone effect with Mediace RPR at RPR titer (card test) of 1:16, but not with HBi Auto RPR. The R.U. values of the two automated RPR assays did not show proportional increase to the RPR titer. Agreement between manual RPR and two automated RPR assay kits, Mediace RPR assay and HBi Auto RPR assay, were 83.8% and 83.2%, respectively. CONCLUSIONS: The two automated RPR assay kits could not be used as an alternative to manual RPR test for quantitative analysis of RPR titer. As Mediace RPR shows a prozone effect at relatively low RPR titer, caution is needed in the interpretation of the measured values.

The comparison of parathyroid hormone degradation effect by various protease inhibitors in blood specimen.

BACKGROUND: The objective of this study was to evaluate the role of proteases on the degradation of parathyroid hormone (PTH) in blood samples. METHODS: Protease inhibitors with specificity against serine proteases (aprotinin), cysteine proteases (E-64), serine and cysteine proteases (leupeptin), metalloproteases (EDTA), or a protease inhibitor cocktail with a broad spectrum of inhibitory activity were added to blood samples. After storage at room temperature (0-48 hr), PTH levels were measured. RESULTS: PTH levels in samples with the protease inhibitor cocktail did not change significantly after 48 hr of storage at room temperature, but the average PTH levels decreased by 40.7% and 20.1%, in samples stored at room temperature and stored at 4 degrees C without protease inhibitors, respectively. PTH levels in samples with leupeptin were stable for up to 24 hr. After 48 hr, the mean PTH levels decreased by 17.1%, 16.0%, 26.2%, and 32.1%, with 500 KIU/mL aprotinin, 100 micromol/L leupeptin, 10 micromol/L E-64, and 10 micromol/L EDTA, respectively, in the samples stored at room temperature. CONCLUSIONS: The decrease in PTH levels in blood samples seemed to be due to the degradation of PTH by proteases. Various proteases, including especially serine proteases, would act together to degrade PTH in blood specimen. The PTH degradation may be inhibited in blood specimen with protease inhibitor cocktail.

Neutrophils with toxic granulation show high fluorescence with bis(Zn2+-dipicolylamine) complex.

Although blood neutrophils with toxic granulation provide an excellent means of evaluating acute bacterial infections, the methods are labor-intensive and their reproducibilities depend on the staining technique and the observer's judgment. We measured the flavin adenine dinucleotide (FAD) content of normal neutrophils and neutrophils with toxic granulation by flow cytometry after incubating them with bis(Zn(2+)-dipicolylamine) complex. A total of 122 blood samples (78 with neutrophils with toxic granulation, 44 with normal neutrophils without toxic granulation) were analyzed. The mean autofluorescence levels of neutrophils in the toxic granulation (+) group and toxic granulation (-) group were both 1.9 x 10(3) MESF (mean equivalent soluble fluorochrome) values. However, after incubating neutrophils with bis(Zn(2+)-dipicolylamine) complex for 15 min, the mean fluorescence intensities of neutrophils in the toxic granulation (+) and toxic granulation (-) groups were significantly enhanced by 71- and 19-fold to 138+/-78 x 10(3) MESF and 37+/-37 x 10(3) MESF, respectively (p <0.001). An MESF cutoff value of 79 x 10(3) showed a sensitivity of 93.2% and a specificity of 81.8% for neutrophils with toxic granulation. Similarly, the MESF level ratio, defined as the ratio of the MESF value after incubation with bis(Zn(2+)-dipicolylamine) complex to the autofluorescence MESF value, at a cutoff value of 41, showed a sensitivity of 92.3% and a specificity of 81.8% for the detection of neutrophils with toxic granulation. The MESF values of neutrophils after incubation with bis(Zn(2+)-dipicolylamine) complex did not correlate with the leukocyte (p >0.05) or neutrophil counts (p >0.05). In conclusion, measurement of FAD fluorescence intensity in neutrophils by flow cytometry after incubation with bis(Zn(2+)-dipicolylamine) complex is an easy, objective, and reliable method of detecting neutrophils with toxic granulation.

Prevalence and characteristics of aac(6')-Ib-cr in AmpC-producing Enterobacter cloacae, Citrobacter freundii, and Serratia marcescens: a multicenter study from Korea.

We investigated the prevalence of aac(6')-Ib-cr and its association with other resistance genes in AmpC-producing Enterobacteriaceae without any selection criteria. A total of 479 clinical isolates of Enterobacter cloacae (179), Citrobacter freundii (134), and Serratia marcescens (166) from 12 laboratories between March and July 2005 were examined. We performed polymerase chain reaction for aac(6')-Ib, bla(OXA-1), ISEcp1, and class 1 integron. The aac(6')-Ib-cr was further identified by digestion with BstF5I and sequencing. The aac(6')-Ib was detected in 110 (23%) of 479 isolates, and 15 isolates (3.1%) were cr variants (8 E. cloacae, 5 C. freundii, and 2 S. marcescens). The aac(6')-Ib-cr was significantly associated with various resistance genes (bla(OXA-1), qnrS, qnrA, bla(CTX-M-3), and bla(CTX-M-14)), mobile elements (ISEcp1, ISCR1, and class 1 integron), and quinolone resistance. Eleven of 15 aac(6')-Ib-cr producers coharbored qnr genes. Although aac(6')-Ib-cr was uncommon in Korean AmpC producers, its association with various resistance genes and mobile elements would facilitate the dissemination of this variant.