ABSTRACT
ObjectiveTo evaluate bacteria contamination during collection,processing and storage of cord blood to gain insight into contamination mechanism and direct prevention.MethodsFresh cord blood was separated by hydroxyethyl starch (HES) to harvest nucleated cells.The bacteria contamination was tested by culturing 10 ml plasma-red cells with BacT/ALERT 3D-480 automatic blood culture system.Total 87 positive samples were further identified for bacteria species.Ninety six cord blood nucleated cells concentrate with bacteria positive stored in liquid nitrogen(LN2) for 6-7 years were thawed at 37 C and re-cultured for bacteria analysis.ResultsWe collected 19 062 umbilical cord blood.Among them,336 was bacteria positive ( contamination rate 1.8 ％ ).Eighty-seven positive samples were further investigated with facultative bacteria 58 (66.7 ％ ),aerobic 38(43.7％ ) and anaerobic 17( 19.5％ ),Gram- negative accounted for 68％ while positive 32％.The most frequent bacteria were Escherichia coli ( 25.3％ ),Streptacoccus intermediate ( 14.9％ ) and Chromobacteria violaceum(9.2％ ).Ninety-six nucleated cells concentrate with bacteria positive were cryopreserved at liquid nitrogen for researching.Of them,83 samples( 86％ ) showed positive of bacteria culture after deep-low temperature storage for 6-7 years.ConclusionsBacteria contamination rate of the cord blood collection,processing and storage in 2000 ～ 2007 was 1.8％.Stored in liquid nitrogen for 6-7 years,the viability of bacteria was 86％.The aseptic procedures of cord blood collection in delivery room should be intensified.The bacteria re-culture following thawing of cord blood cells is necessary before clinical transfusion.
ABSTRACT
Objective To investigate the reliability of using inhibitors including Phenylboronic acid (PBA)and Fqucloxacillin(FCC)in detecting derepressed hyperproduction and plasmid-mediated AmpC B-lactamases.Methods PBA and FCC were chosen as inhibitors and double-disk potentiation method and double-disk synergy method were used to detect positive and negative control strains of AmpC β-lactamases and 107 clinical isolates for AmpC β-lactamases production.The positive control strains included E.cloacae (029M),plasmid-mediated ACT-1 type of E.coli DH5a2919,MOX-1 type of k pheumoniae,LAT-2 type of E.coil.The negative control strains included E.cloacae 029(wild-type),E.coli SHV-1,E.coli SHV-2, E.coil SHV-5,E.coli TEM-1,E.coli TEM-3,k peumoniae SHV-18 and E.coli ATCC25922.We compared the results above with the three dimensional test(3-DT)to observe the accuracy in detecting AmpC-BLA.Results 3-DT together with PBA and FCC based inhibition tests showed the 4 positive control strains and the 9 negative control strains were determined as expected.AmpC-BILA was detected in 107 clinical isolates ofEnterobacteriaceaes.The positive rate of3-DTmethod is24.3%.The positive rates ofPBA.FCC double-disk potentiation method and double-disk synergy method are 30.8%(33/107),26.2%(28/107) and 23.4%(25/107),respectively.The conjugate results in two strains of P mirabilis and one strain of K.peumoniae were positive.They were all plasmid-mediated AmpC-Bi.A.There Was a higher false positive when using PBA and FCC-based double-disk potentiation method to detect the induction type of AmpC-BLA, but the accuracy of double-disk synergy method was high.Compared with the 3-DT,the coincidence rate using PBA and FCC-based double-disk synergy method is 99.1%.Conclusions Using PBA and FCC as inhibitors in the double-disk synergy test is a accurate and reliable method to detect AmpC-BLA regardless of derepressed hyperproduction type or plasmid-mediated type.