The pathogenesis of herpes zoster is closely linked to reduced varicella-zoster virus-specific cell-mediated immunity. However, little is known about the interplay between natural killer cells and psychological stress in the pathogenesis of herpes zoster. This study aimed to investigate possible associations among natural killer cells, T cells and psychological stress in herpes zoster. Interferon-gamma secretion from natural killer cell, psychological stress events, stress cognition scale scores and cytomegalovirus-specific cell-mediated immunity were compared between 44 patients with herpes zoster and 44 age- and gender-matched control subjects. A significantly lower median level of interferon-gamma secreted by natural killer cells was observed in patients with a recent diagnosis of herpes zoster than in control subjects (582.7 pg/ml vs. 1783 pg/ml; P = 0.004), whereas cytomegalovirus-specific cell-mediated immunity was not associated with herpes zoster. Psychological stress events and high stress cognition scale scores were significantly associated in patients with herpes zoster (P<0.001 and P = 0.037, respectively). However, reduced interferon-gamma secretion from natural killer cell and psychological stress were not associated. In conclusion, patients with a recent diagnosis of herpes zoster display reduced interferon-gamma secretion from natural killer cells and frequent previous psychological stress events compared with controls. However, reduced natural killer cell activity is not an immunological mediator between psychological stress and herpes zoster.

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There is a high demand for novel approaches to counter the various challenges of conventional drug susceptibility testing (DST) for tuberculosis, the most prevalent infectious disease with significant global mortality. The QMAC-DST system was recently developed for rapid DST using image technology to track the growth of single cells of Mycobacterium tuberculosis (MTB). The purpose of this study was to clinically validate the QMAC-DST system compared to conventional DST. In total, 178 MTB isolates recovered from clinical specimens in Asan Medical Center in 2016 were tested by both QMAC-DST and absolute concentration methods using Lowenstein-Jensen media (LJ-DST). Among the isolates, 156 were subjected to DST using BACTEC MGIT 960 SIRE kits (BD, Sparks, MD, United States) (MGIT-DST). The susceptibility/resistance results obtained by QMAC-DST were read against 13 drugs after 7 days of incubation and compared with those of LJ-DST. Based on the gold standard LJ-DST, the agreement rates of QMAC-DST for all drugs were 97.8%, 97.9%, and 97.8% among susceptible, resistant, and total isolates, respectively, while the overall agreement of MGIT-DST tested for 156 isolates against first-line drugs was 95.5%. QMAC-DST showed the highest major error of 6.4% for rifampin, however, it could be corrected by a revised threshold of growth since false-resistant isolates showed grew only half than the true-resistant isolates. The rapid and accurate performance of QMAC-DST warrants ideal phenotypic DST for a wide range of first-line and second-line drugs.

Blood culture is important to detecting bacteremia and fungemia in patients with suspected sepsis. We observed a four-year trend of blood culture isolates in the frequency by age group and in vitro antimicrobial susceptibility patterns obtained at VHS Medical Center, the largest veterans hospital in Korea. Blood cultures collected between 2012 and 2015 were analysed retrospectively. Of 68,352 blood specimens, 7,901 isolates were identified during the study period. Seventy-two percent of the isolates were gram-positive cocci, 18% were gram-negative rods, and 6% were fungi. The frequency of bacteremia/fungemia in patients who were 80-89 years old was 43.8%, the highest rate among all age groups, and the mean age of patients diagnosed by blood culture was 77 years old. Coagulase-negative staphylococcus (52.3%), Staphylococcus aureus (8.3%), enterococci (7.5%), Escherichia coli (6.4%), and Klebsiella pneumoniae (3.9%) were the bacteria most commonly isolated. The percentage of methicillin-resistant S. aureus increased in 2015 (76%) relative to that in 2012-2014 (63%-65%), and that of vancomycin-resistant Enterococcus faecium was 17%-22% with no significant changes through time. Among the gram-negative isolates, the ciprofloxacin resistance rate increased to 51.4% (E. coli) and 31.1% (K. pneumoniae) in 2015, but imipenem or ertapenem resistance was still very rare, with resistance rates of less than 0.5%. Acinetobacter baumannii showed a high rate of resistance (over 70%) to imipenem and ciprofloxacin throughout the study. In Pseudomonas aeruginosa, the resistance rates of imipenem and ciprofloxacin increased dramatically over time. This analysis confirmed a decrease in antimicrobial susceptibility of gram-negative rods isolated by blood culture.

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