BruSIC: a novel selective medium for the primary isolation of Brucella in veterinary samples

Brucellosis, a re-emerging zoonotic infection, threatens animal welfare and public health with serious economic consequences. A definitive diagnosis requires Brucella isolation by culturing field specimens in specific media. This study aimed to (i) assess the effectivity of recommended Farrell's médium (FM) and CITA medium (CM) for the isolation of four Brucella melitensis strains (16M, Rev1, and the 16MΔwzm and Rev1Δwzm in-frame deletion mutants) with variable susceptibility to polymyxins; (ii) develop a Brucella selective medium (BSM) suitable for these strains; (iii) test BSM, FM, and CM with other Brucella species; and (iv) develop an improved selective culture medium (BruSIC) for all brucellae, including B. abortus bv1. The four B. melitensis strains were strongly inhibited in FM and (except Rev1) CM. Since Rev1Δwzm's CM inhibition was due to a synergistic effect of colistin and vancomycin, we formulated BSM with half the concentrations of both antibiotics, achieving a similar growth of B. melitensis to blood agar base (BAB) and an inhibition of contaminant microorganisms comparable to CM; CM performance was surpassed by BSM for the primary isolation of B. melitensis when tested in 1,789 real sheep samples. For other brucellae, BSM and CM were more inhibitory than FM for B. abortus bv1 when using plates immediately after preparation but not after ≥4 weeks of storage. To address this, we developed the improved solid medium BruSIC by replacing the calf serum in BSM with activated charcoal. BruSIC yielded faster colony growth than BSM and CM and similar CFU numbers than BAB (including for B. ovis in BAB-Serum) and inhibited accompanying microorganisms in sheep and cow samples as effectively as BSM. IMPORTANCE Farrell's medium (FM) and CITA medium (CM), recommended for Brucella isolation in animal samples, are inhibitory for certain strains. A reformulated Brucella selective medium (BSM), containing half the CM vancomycin and colistin concentrations, improved the isolation of B. melitensis, but not Brucella abortus bv1. A novel Brucella selective culture medium (BruSIC), in which calf serum is replaced by activated charcoal, retains the selectivity and improves the productivity of BSM and CM. BruSIC allows the growth of all brucellae faster than in CM or BSM, and at CFU number equivalent to BAB supplemented by calf serum, including B. abortus bv1 and the serum-dependent Brucella ovis. Due to its performance and reduced cost, BruSIC represents an added-value alternative to the existing selective culture media for these bacteria.

Use of Monocyte-Derived Macrophage Culture Increases Zika Virus Isolation Rate from Human Plasma

Viral isolation is desirable for many reasons, including development of diagnostic assays and reference materials, and for virology basic research. Zika virus (ZIKV) isolation from clinical samples is challenging, but isolates are known to infect various cell lines. Here, we evaluated suitability of Vero, C6/36 and JEG-3 as host cells, for direct isolation of ZIKV from human plasma. We also assessed the use of primary monocyte-derived macrophages (MDMs) culture to enhance ZIKV isolation from human plasma samples followed by virus expansion in Vero, C6/36 and JEG-3 cultures. Direct inoculation of cell lines with 42 ZIKV-RNA positive samples resulted in isolation rates of 9.52% (4/42) in Vero and C6/36, and of 7.14% (3/42) in JEG-3 cells. Inoculation of plasma in MDMs followed by supernatant testing by TaqMan RT-PCR, resulted in 33/42 (78.57%) ZIKV-RNA-positive supernatants, which expansion in cell lines increased isolation rates to 24.24% (8/33) in Vero and to 27.27% (9/33) in C6/36 and JEG-3 regardless of the presence of ZIKV-antibody. Isolates generated in JEG-3 cells were also produced in Vero and C6/36 with similar viral titers. These results suggest that efficiency of ZIKV isolation from human plasma can be enhanced when MDM culture is used before viral expansion in cell lines.

Down-regulation of microRNA let-7d inhibits the proliferation and invasion of trophoblast cells in preeclampsia

Preeclampsia (PE) is a serious pregnancy complication that continues to adverse effects on mother and the fetus. The study investigated the effect of microRNA let-7d (miR-let-7d) on the proliferation and invasion of trophoblast cells (TC) in PE. In situ hybridization techniques were employed to evaluate the miR-let-7d expressions in the placental tissues from 63 PE patients as well as 65 normal placental tissues. Transfection of pre-let-7d, anti-let-7d, and their corresponding control sequences was performed in TCs obtained from PE. The blank group was composed of TCs no transfection and normal group consisted of normal TCs. Expressions of proliferation and invasion markers in TCs were detected by qRT-PCR. Proliferation, apoptosis, and the invasion ability of the TCs were determined using a CCK-8 assay, flow cytometry, and Transwell assay. In comparison to the normal placental tissues, PE placental tissues exhibited increased levels of let-7d expression. Following transfection of anti-let-7d, when compared with the blank group, the anti-let-7d group displayed increased levels of proliferation ability, expression of proliferation labeling proteins PCNA and Ki67, number of TCs as well as expressions of the invasion related proteins MMP-2, MMP-9, and TIMP-1. In contrast declines in cell apoptosis rate were observed. Compared with the blank group, the changes of the indexes were reversed in the pre-let-7d group. The study provided evidence suggesting that low expression levels of miR-let-7d plays a central role in suppressing apoptosis in addition to promoting the proliferation and invasion of PE TCs.

Susceptibility of rodent cell lines to rat coronaviruses and differential enhancement by trypsin or DEAE-dextran

Cell lines of rodent origin were tested for susceptibility to infection with rat coronavirus (RCV), including sialodacryoadenitis virus (SDAV) and Parker's rat coronavirus (PRCV). LBC rat mammary adenocarcinoma cells were susceptible only if the cells were treated with diethylaminoethyl-dextran (DEAE-D). A recent report that RCVs grow well in L2 mouse fibroblast cells was confirmed and expanded. RCV infection of L2 cells was substantially enhanced by treatment of cells with trypsin but not by treatment with DEAE-D. Primary isolation of SDAV from experimentally infected rats was accomplished using trypsin-treated L2 cells. One of 13 additional cell lines tested (rat urinary bladder epithelium, RBL-02) supported growth of RCVs, and growth was slightly enhanced by DEAE-D, but not by trypsin. These refinements of in vitro growth conditions for RCVs should facilitate further studies of their basic biology and improve options for primary isolation.

NCI-H292 as an alternative cell line for the isolation and propagation of the human paramyxoviruses

Primary rhesus monkey kidney (MK) cells have long been the cells of choice for isolation and propagation of the human paramyxoviruses (parainfluenza 1, 2, 3, 4A, 4B, and mumps). However, problems with the supply and cost of MK cells and the presence of endogenous viruses, including herpes B virus and SV-5, necessitated a search for an alternative cell line. Continuous cell cultures of human origin (L132, A-549, HuT-292, HEK, G-293, G-401, A-498, A-704, CAKI-1, RD) and simian origin (LLC-MK2, BSC-1, MA-104, Vero) were evaluated for their capacity to support the growth of the human paramyxoviruses, as followed by cytopathic effect, hemadsorption, hemagglutination, and EIA. NCI-H292 (HuT-292) human lung mucoepidermoid carcinoma cells (ATCC # CRL-1848) proved to be the most sensitive line for cultivating all serotypes and strains of the paramyxoviruses. These cells were also shown to be a suitable substitute for MK in primary isolation of paramyxoviruses from clinical specimens. RPMI-1640 with 1.5 micrograms/ml trypsin was the preferred maintenance medium; alternatively, Eagle's MEM supplemented with 1.5 micrograms/ml trypsin and 0.1% ITS was satisfactory. NCI-H292 cells are a continuous line with excellent growth characteristics, although the genetic polyploidy of the cells may limit the number of passages of usable cells.