Rapid determination of ß-lactam antimicrobial resistance in bacteria by a liquid chromatography-mass spectrometry-based method.

Conventional antimicrobial susceptibility tests (ASTs) are very time consuming and insufficiently precise to promptly select a proper antimicrobial treatment. This difficulty disrupts the management of infections and exacerbates the development of antimicrobial resistance. Generally, antimicrobial resistance involves the chemical modification of an antimicrobial compound to an inactive form by an enzyme released by bacteria. This modification causes a structural change and is followed by a characteristic mass shift of the antimicrobials. Using this mechanism, we developed a new liquid chromatography-mass spectrometry method to rapidly determine the degree of resistance of Salmonella enterica subspecies enterica serovar Typhimurium (Salmonella Typhimurium), Escherichia coli, and Staphylococcus aureus to amoxicillin, ampicillin, and penicillin G, respectively. This method was successfully applied to 20 bacterial isolates from Korean slaughterhouses and farms. There were 18-Da mass shifts in resistant strains compared with susceptible strains of Salmonella Typhimurium, E. coli, and S. aureus, and the intensities of the hydrolyzed penicillin mass spectra were much higher in resistant strains than those in susceptible strains, which together indicate the reliability of this method. A comparison of the mass spectrometry-derived results with that from conventional ASTs revealed an identical classification of the tested bacteria according to sensitivity and resistance. Notably, this assay method requires only 2 h for determining the susceptibility status of a strain. This newly developed method is able to determine the extent of antimicrobial resistance qualitatively and quantitatively within a very short time and could be used to replace conventional AST methods. Graphical abstract Rapid determination of ß-lactam antimicrobial resistance in bacteria by LC-MS/MS.

Evaluation of changes induced by temperature, contact time, and surface in the efficacies of disinfectants against avian influenza virus.

Avian influenza viruses (AIV) are highly susceptible to all disinfectants because they are enveloped viruses. Disinfectants effective against AIV have optimum efficacies at temperatures above 20°C. Very few studies on effective disinfectants at low temperatures have been done. Disinfectants were investigated at 4 different temperatures (25, 4, 0, and -10°C) and 2 contact times (1 and 5 min) with suspension tests. Virucidal activity of the disinfectants was evaluated by carrier tests (wood and stainless steel) at 25 and -10°C. The concentration of each disinfectant for efficient disinfection within a short time (<1 min) at 25 and -10°C was also reestablished. The results from the suspension test indicated that low temperatures inhibited the virucidal efficacy of citric acid (CA) and CA + quaternary ammonium compounds (CA+ QAC) for 1 and 5 min, whereas the remaining disinfectants were effective, regardless of the short contact times and low temperatures. The carrier test results suggested that dried virus on wood was more difficult to inactivate compared with that on stainless steel. However, sodium dichloroisocyanurate and glutaraldehyde could inactivate AIV on both wood and stainless steel at -10°C. Citric acid-based agents could not sufficiently inactivate AIV at -10°C; however, the limitation due to low temperatures was overcome by adjusting disinfectant concentration. For a successful disinfection during winter, the disinfectants that could have short contact times with optimum efficacy against the target organism should be selected.

Efficacy evaluation of commercial disinfectants by using Salmonella enterica serovar Typhimurium as a test organism.

The efficacies of six commercial disinfectants were evaluated by using Salmonella enterica serovar Typhimurium under simulated natural conditions such as sub-zero temperature, short disinfecting time, and surface type (uneven or smooth). We used a suspensionmodel test to determine the disinfecting efficacy under varying contact times (1, 5, 10, and 30 min) and temperatures (25°C, 4°C, 0°C, and -10°C). The bactericidal effect according to surface structure was measured by using a carriermodel test at 25°C and -10°C. The effective concentrations of each disinfectant were fixed to give a disinfecting effect within a short time (< 1 min) at 25°C and -10°C. The suspension model results revealed that bactericidal efficacy significantly dropped at low temperature for most of the disinfectants used; a sodium dichloroisocyanurate product showed the strongest efficacy. In the carrier test, bacterial load on a wooden surface was more difficult to remove than that on a stainless-steel surface. The results show that commercial disinfectant products vary in their disinfecting efficacy, which is affected by several field factors including temperature, contact time, and carrier material. Environmental conditions and surface type for disinfection should be considered prior to selecting an optimal disinfectant in the field.

Epidemiological aspects of human brucellosis and leptospirosis outbreaks in Korea.

UNLABELLED: In order to compare the epidemiological aspects of human brucellosis (HB) and human leptospirosis (HL) outbreaks in Korea, we have analyzed the current state both of the disease incidence and related risk factors. A total 651 cases of HB occurred between 2001 and 2010 in Korea, and the average incidence rate per 100,000 populations was 0.15. A total 1,153 of HL cases occurred during the same period, and its rate was 0.24. While most of the HB prevalence occurred in the whole year round, prevalence in summer was more prominent for HB (p < 0.01), while outbreaks in autumn was more frequent for HL (p < 0.01). Geographical distribution HB cases were eastern and western regions of the rural (88.6% of total) in the Korean peninsula, showing higher outbreaks than other areas, while HL occurred in easterly regions (64.5%). Significantly more males were infected in both HB (86.8%) and HL (59.5%) than those of females in both HB (13.1%) and HL (41.1%), respectively (p < 0.01). The distribution by age groups were different between HB and HL, while the outbreaks over 62.1% of the cases of HB occurred in 40- to 59-year-old age group, and that of HL was clearly showing a high incidence in the elderly age over 60-year-old (59.6%) (p < 0.01). In both diseases, elderly people especially in famers showed a very high incidence rate (57.9% of HB and 52.2% of HL), which is possible due to increased outdoor activities and a decreased number of young people in those areas. The occupational distribution of HB cases was famers, veterinarians, dairyman and others, and those of HL cases were broad. In conclusion, the difference between HB and HL risk factors reflects the different influence of host/vector, climate, and geographical and environmental characteristics in the epidemiological patterns. KEYWORDS: Human brucellosis and leptospirosis; Epidemic aspects; Risk factors.