Successful infection control for a vancomycin-intermediate Staphylococcus aureus outbreak in an advanced emergency medical service centre

BACKGROUND

A vancomycin-intermediate Staphylococcus aureus (VISA) (vancomycin minimum inhibitory concentration: 4mg/L) outbreak occurred in an advanced emergency medical service centre [hereafter referred to as the intensive care unit (ICU)] between 2013 and 2014.

AIM

Our objective was to evaluate the infection control measures that were successful.

METHODS

Seventeen VISA strains were isolated from the sputum of 15 inpatients and the skin of two inpatients. Fourteen VISA strains were recognized as colonization. However, three VISA strains were isolated from the sputum of three inpatients with pneumonia. Environmental cultures were performed and VISA strains were detected in five of 65 sites. Pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) was performed on 21 VISA strains.

FINDINGS

Molecular typing including PFGE and MLST showed that the patterns of 19 VISA strains were identical and those of the other two VISA strains were possibly related. This meant that a horizontal transmission of VISA strains had occurred in the ICU. In August 2013, the infection control team began interventions. However, new inpatients with VISA strains continued to appear. Therefore, in October 2013, the ICU was partially closed in order to try to prevent further horizontal transmission, and existing inpatients with the VISA strain were isolated. Although new cases quickly dissipated after the partial closure, it took approximately five months to eradicate the VISA outbreak.

CONCLUSION

Our data suggest that despite the employment of various other infection control measures, partial closure of the ICU was essential in terminating this VISA outbreak.

Research note: fructose feeding increases lower gut weights in germ-free and conventional chicks

The present study was conducted to investigate whether there was any effect of carbohydrate sources on the magnitude of differences in growth and tissue weights found between germ-free and conventional environments in the chicken. Germ-free and conventional birds were allowed free access to a purified diet in which glucose or fructose was used as a sole carbohydrate source from 7 to 17 days of age. Growth performance and visceral weights were measured at the end of the experiment. The results indicated that there was no difference in growth, feed intake, or feed efficiency between the two environments, but that feeding fructose increased feed intake and decreased feed efficiency compared with feeding glucose. The conventional birds had heavier visceral organ weights including liver, jejuno-ileum, and cecum than did the germ-free counterparts. Feeding fructose resulted in lighter liver weight and heavier weights of jejuno-ileum and cecum than feeding glucose. It was concluded that consuming fructose might increase the lower gut weight of the chicken, as was found by the association with normal microflora, but might not affect overall growth compared with consuming glucose.

Effect of diet type on enhanced intestinal protein synthesis by the gut microflora in the chick

An experiment was conducted to investigate the effect of diet type on enhanced protein synthesis by the gut microflora in the chick intestine. Both germ-free (GF) and conventional (CV) White Leghorn chicks were fed ad libitum from 4 to 14 d of age either a nonpurified diet or a purified diet having 19% crude protein and 12.1 kJ/g metabolizable energy value. At 14 d of age, protein synthesis was measured in duodenum, jejunoileum and ceca after a large dose of L-[4-3H]phenylalanine injected intravenously via a wing vein. The results showed that wet tissue weights for all intestinal sections were significantly greater in CV birds than in GF counterparts with consistently larger differences between the two environments in chicks fed the nonpurified diet than in those fed the purified diet. Protein synthesis in all intestinal sections was significantly enhanced by the presence of gut microflora in terms of both fractional rate (%/d) and absolute rate [mg/(100 g BW.d)]. The effect of diet type on fractional and absolute rates of protein synthesis was most remarkable in ceca where the significant difference between GF and CV states was found only in chicks fed the nonpurified diet but not in those fed the purified diet.

Influence of the gut microflora on protein synthesis in tissues and in the whole body of chicks

1. The influence of the gut microflora on protein synthesis in individual tissues and in the whole body of young chicks was investigated by the large-dose injection of [3H]phenylalanine. 2. Growth of germ-free chicks was significantly better than that of conventional controls. Wet weights of liver, spleen, duodenum, jejunum + ileum and caeca were heavier in conventional birds than in germ-free counterparts. 3. Fractional rates of protein synthesis were higher in jejunum + ileum and whole body of conventional birds than in those of germ-free birds. Amounts of protein synthesized were larger in liver, jejunum + ileum and caeca in the presence of the gut microflora. 4. When tissues were classified into gut + liver and the remainder of the carcass, in the presence of the gut microflora an enhanced protein synthesis in fractional and absolute rate was found in the gut + liver, which is in direct contact or in close association with micro-organisms, whereas virtually no effect of the gut micro-organisms was detected in the remainder of the carcass. 5. The contribution of protein synthesis of gut + liver to that of the whole body was larger in conventional chicks than in germ-free birds, whereas the reverse was true for the remainder of the carcass.