Quantifying the effectiveness of ultraviolet-C light at inactivating airborne Mycobacterium abscessus

BACKGROUND

Mycobacterium abscessus (MABS) group are environmental organisms that can cause infection in people with cystic fibrosis (CF) and other suppurative lung diseases. There is potential for person-to-person airborne transmission of MABS among people with CF attending the same care centre. Ultraviolet light (band C, UV-C) is used for Mycobacterium tuberculosis control indoors; however, no studies have assessed UV-C for airborne MABS.

AIM

To determine whether a range of UV-C doses increased the inactivation of airborne MABS, compared with no-UVC conditions.

METHODS

MABS was generated by a vibrating mesh nebulizer located within a 400 L rotating drum sampler, and then exposed to an array of 265 nm UV-C light-emitting diodes (LED). A six-stage Andersen Cascade Impactor was used to collect aerosols. Standard microbiological protocols were used for enumerating MABS, and these quantified the effectiveness of UV-C doses (in triplicate). UV-C effectiveness was estimated using the difference between inactivation with and without UV-C.

FINDINGS

Sixteen tests were performed, with UV-C doses ranging from 276 to 1104 μW s/cm². Mean (±SD) UV-C effectiveness ranged from 47.1% (±13.4) to 83.6% (±3.3). UV-C led to significantly greater inactivation of MABS (all P-values ≤0.045) than natural decay at all doses assessed. Using an indoor model of the hospital environment, it was estimated that UV-C doses in the range studied here could be safely delivered in clinical settings where patients and staff are present.

CONCLUSION

This study provides empirical in-vitro evidence that nebulized MABS are susceptible to UV-C inactivation.

Genomics of the major histocompatibility complex: haplotypes, duplication, retroviruses and disease

The genomic region encompassing the Major Histocompatibility Complex (MHC) contains polymorphic frozen blocks which have developed by local imperfect sequential duplication associated with insertion and deletion (indels). In the alpha block surrounding HLA-A, there are ten duplication units or beads on the 62.1 ancestral haplotype. Each bead contains or contained sequences representing Class I, PERB11 (MHC Class I chain related (MIC) and human endogenous retrovirus (HERV) 16. Here we consider explanations for co-occurrence of genomic polymorphism, duplication and HERVs and we ask how these features encode susceptibility to numerous and very diverse diseases. Ancestral haplotypes differ in their copy number and indels in addition to their coding regions. Disease susceptibility could be a function of all of these differences. We propose a model of the evolution of the human MHC. Population-specific integration of retroviral sequences could explain rapid diversification through duplication and differential disease susceptibility. If HERV sequences can be protective, there are exciting prospects for manipulation. In the meanwhile, it will be necessary to understand the function of MHC genes such as PERB11 (MIC) and many others discovered by genomic sequencing.

The Malai Ika Daigaku (Syonan Medical College) in Malacca (1944 to 1945) during the Japanese occupation of Singapore and Malaya

During the Japanese Occupation of Singapore and Malaya (1941-1945), Singapore was renamed Syonan (or Syonanto) and Malaya was called Malai (or Marai; Marei). On 27 April 2603 (1943) the Japanese Military Administration established. The Marai Ika Daigaku (Syonan Medical College) at the Tan Tock Seng Hospital (Hakuai Byoin), Syonan. The Medical College shifted to the General Hospital, Malacca in February 2604 (1944) where it functioned till the end of the Japanese Occupation in September 2605 (1945).

The Marei Ika Daigaku (Syonan Medical College) during the Japanese occupation of Singapore (1942-1945)

During the Japanese Occupation of Singapore (1942-1945), Singapore was renamed Syonan (or Syonanto). The Japanese Military Administration established The Medical College on 27 April 2603 (1943) and it was known as The Marei Ika Daigaku or Syonan Medical College. It was sited at the Tan Tock Seng Hospital (Hakua Byoin). The Ika Daigaku relocated to the General Hospital, Malacca in February 2604 (1944) where it functioned till the end of the Japanese Occupation in September 1945. About 200 students from Singapore, Malaya, Sumatra and Java attended the Syonan Medical College; the students were taught mainly Japanese language and culture.

Immunogenetic analysis of successful and rejected bone marrow grafts within one family

We report the case of an Indonesian patient who required urgent bone marrow transplantation for acute leukaemia and who received successive transplants from two siblings. The first transplant failed while the second was successful. There were some uncertainties in serological typing due to the presence of cross-reacting HLA-B alleles, lack of paternal typing and the use of Caucasoid sera for Indonesian patients. Distinction between the two donors was also difficult. Interestingly, the use of a new DNA technique identified the presence of differences between the patient and the first unsuccessful donor but not the second successful donor.

Histocompatibility matching for bone marrow transplantation. Donor-recipient pairs in the 4AOHW cell panel

While the results of unrelated bone marrow transplantation are continually improving, a number of important issues remain: what are the histocompatibility requirements, what genes are involved, what mismatches are acceptable, and what are the best methods for determining donor-recipient match? In this study of material provided through the 4AOHW and the US NMDP, the match between 53 donor-recipient pairs was determined using several different markers within the MHC. The data showed that many apparently well-matched pairs have many mismatches, including mismatches for non-HLA genes (i.e., non-class-I or non-class-II) within the MHC. New methods matching for blocks of DNA around HLA-B and around HLA-DR/DQ are available that are sensitive and identify additional mismatches that are not apparent using conventional typing methods. The 4AOHW cells provide a valuable resource for the comparison and assessment of new matching techniques.

Analysis of MHC genomic structure and gene content between HLA-B and TNF using yeast artificial chromosomes

To characterize the genomic structure and gene content between HLA-B and TNF we studied three overlapping yeast artificial chromosome (YAC) clones derived from the Boleth cell line carrying the 62.1 MHC ancestral haplotype (AH). In particular, we have evaluated the stability of haplospecific sequence motifs (haplospecific geometric elements) in YACs. By PCR and gene scanning we show that the two larger YAC clones (318G11 and 8F2) exhibit features characteristic of the 62.1 AH carried by the parental cell line as well as those of a separate cell line (BSM) which also carries 62.1. It is concluded that a highly polymorphic duplicated region is represented faithfully in spite of the fact that it contains sequences that could be interpreted as simple repeats liable to mutations. In contrast, microsatellites AFM031 and AFM158, which are also located in the MHC, showed greater instability and the structure in the YACs was not consistent with genomic structure. Likewise, different examples of the same ancestral haplotype show differences at these microsatellite loci. We conclude that polymorphic repeat sequences may exhibit a range of stabilities in vivo and that this may be reflected in their stability in YACs. Northern blotting using the largest YAC clone revealed several novel transcripts which await localization.