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Biomedical subjects

M L Ling

Publications and source records attributed to M L Ling.

6 recordsLinked to original sources
PubMed1992

Isolation and sequence analysis of dacB, which encodes a sporulation-specific penicillin-binding protein in Bacillus subtilis.

A novel penicillin-binding protein (PBP 5*) with D,D-carboxypeptidase activity is synthesized by Bacillus subtilis, beginning at about stage III of sporulation. The complete gene (dacB) for this protein was cloned by immunoscreening of an expression vector library and then sequenced. The identity of dacB was verified not only by the size and cross-reactivity of its product but also by the presence of the nucleotide sequence that coded for the independently determined NH2 terminus of PBP 5*. Analysis of its complete amino acid sequence confirmed the hypothesis that this PBP is related to other active-site serine D,D-peptidases involved in bacterial cell wall metabolism. PBP 5* had the active-site domains common to all PBPs, as well as a cleavable amino-terminal signal peptide and a carboxy-terminal membrane anchor that are typical features of low-molecular-weight PBPs. Mature PBP 5* was 355 amino acids long, and its mass was calculated to be 40,057 daltons. What is unique about this PBP is that it is developmentally regulated. Analysis of the sequence provided support for the hypothesis that the sporulation specificity and mother cell-specific expression of dacB can be attributed to recognition of the gene by a sporulation-specific sigma factor. There was a good match of the putative promoter of dacB with the sequence recognized by sigma factor E (sigma E), the subunit of RNA polymerase that is responsible for early mother cell-specific gene expression during sporulation. Analysis of PBP 5* production by various spo mutants also suggested that dacB expression is on a sigma E-dependent pathway.

Amino Acid Sequence↗
PubMed1992

Leuconostoc bacteraemia.

Leuconostoc species, a gram-positive coccal bacterium that is classically moderately susceptible to ampicillin and penicillin and resistant to vancomycin is a potential pathogen in the immunocompromised host. Twenty-eight isolates were collected from patients' blood culture specimens in the year 1989-1990. The clinical history and course of nineteen of these patients were studied. Five of them recovered without any antimicrobial therapy and in eight patients Leuconostoc species was isolated with other organisms in the blood culture specimens. The question arises as to when Leuconostoc species is of clinical significance when isolated in the blood culture specimens of patients.

Adult↗
PubMed1990

Epidemiology of pneumococcal infection in Singapore (1977-1986).

Streptococcus pneumoniae was isolated from 43 children and 143 adults in a ten year period from 1977 through 1986. There was a high incidence in the males, in the extremes of ages and in the Indian and Others racial groups. The overall mortality rate was 29.5% with a higher rate associated in those with chronic obstructive lung disease, smoking, malignancy and alcoholism, 0.5% of the isolates were resistant to penicillin (of intermediate resistance only) and 16% resistant to tetracycline. Common serotypes isolated were types 1, 4, 14, 3 and 6B, all of which are covered by the pneumococcal vaccine. In children, the common serotypes associated with primary bacteraemia were types 14 and 20; with pneumonia, types 6B, 14, 19A and with meningitis, types 6B, 19F and 19A. In adults, the common serotypes associated with primary bacteraemia were types 20, 11A and 1; with pneumonia, types 3, 4, 7F, 14; with meningitis, types 1, 13, 34 and with endocarditis, type 13. Characteristics of pneumococcal infection, the organism's antibiogram and the serotype distribution are discussed in relation to the work of other investigators.

Age Factors↗
PubMed1989

Abortive initiation by bacteriophage T3 and T7 RNA polymerases under conditions of limiting substrate.

Initiation of RNA synthesis by the phage polymerases is abortive if the concentration of pyrimidine triphosphates is limiting. Under abortive initiation conditions the polymerases repeatedly initiate transcription but produce ribooligonucleotides that terminate just prior to the first occurrence of the limiting substrate. Abortive initiation is most severe if the limiting substrate occurs within the first 8-12 nucleotides of the nascent RNA chain and is particularly evident when UMP is limiting. The formation of stable elongation complexes (as determined by gel retardation experiments) occurs after the synthesis of an RNA product 8-12 nucleotides in length.

Base Sequence↗
PubMed1989

Comparative double-blinded study between mupirocin and tetracycline ointments for treating skin infections.

A double-blinded study was conducted to compare the effects of mupirocin and tetracycline ointments in the treatment of skin infections. 111 patients were available for clinical assessment, of which 53 were treated with mupirocin and 58 treated with tetracycline. Clinically, both groups were improved, and there was no significant difference. Bacteriological assessment however revealed a better response to mupirocin. Staphylococcus aureus and Streptococcus pyogenes were the most common organisms isolated. 99% of Staphylococci were sensitive to mupirocin compared with 61% to tetracycline and 29% to penicillin G. 57% of Group A beta haemolytic Streptococci were resistant to tetracycline compared to 14% to mupirocin. Gram-negative organisms were mostly resistant to both preparations. No side effects were observed in both treatment groups. This study suggests that mupirocin is a safe and effective topical preparation for treating most of our common skin infections.

Adolescent↗