Biomedical subjects
Publications and source records attributed to L Tay.
A case of Pasteurella multocida infection in Singapore is presented. The patient was a 21-year-old Chinese male who developed fever and cellulitis with abscess formation of his right index finger after it was bitten by a stray cat. The organism was isolated in pure culture and identified as Pasteurella multocida subspecies septica. The patient responded to antibiotic therapy and had an uneventful recovery.
Enteropathogenic Escherichia coli (EPEC) was isolated from 2.7% of 2983 children under 3 years of age with diarrhoea in Singapore. Of the nine serotypes identified, the most common were 0126:K71(B16), 086:K61(B7) and 0127:K63(B8). Infants were at the greatest risk of contracting gastroenteritis due to EPEC, and female children were slightly more susceptible than males. Antimicrobial susceptibility tests showed that the EPEC strains were generally resistant to ampicillin, streptomycin, tetracycline and triple sulpha, but highly sensitive to ceftriaxone and gentamicin.
To determine the presence of Yersinia enterocolitica in Singapore, an attempt was made to isolate this organism from the stool samples of 6,619 patients with diarrhoea. No Y. enterocolitica was detected. The results suggest that Y. enterocolitica is not an important bacterial pathogen causing diarrhoeal disease in this region.
A total of 7344 inpatients with diarrhoea were investigated for Campylobacter infections in Singapore over one year. Campylobacter species were recovered from 1.2% of diarrhoeal stools; 70.3% of the 91 campylobacters were from children under 5 years of age. Further identification of these isolates showed that 89% were Campylobacter jejuni and 10.9% were C. coli, and a high level of resistance to erythromycin was observed among them. Concomitant isolation of Salmonella species or Shigella species was achieved in eight of the Campylobacter-infected patients. Campylobacter enteritis occurred throughout the year, with the highest isolation rate being recorded in September.
The comparative carcinogenicities of N-hydroxy-N-acetyl-1-aminopyrene, N-acetyl-1-aminopyrene, and 1-, 2-, and 4-nitropyrene were determined following i.p. injection into weaning female CD rats (67 mumol/kg body weight in dimethyl sulfoxide; 3 times/week for 4 weeks). At sacrifice 61 weeks after the first injection the incidences of malignant mammary tumors were increased significantly to 45 and 24% in the 4-nitropyrene- and N-hydroxy-N-acetyl-2-aminofluorene-treated groups, respectively. Cellular altered foci in the liver were increased significantly in the N-acetyl-1-aminopyrene-, N-hydroxy-N-acetyl-1-aminopyrene-, and N-hydroxy-N-acetyl-2-aminofluorene- treated groups; the latter two compounds also led to significantly increased formation of hyperplastic nodules in this organ. Significant increases in leukemia induction were observed in animals treated with 2-nitropyrene or N-hydroxy-N-acetyl-2-aminofluorene. In an experiment designed to compare the influence of the route of administration on the carcinogenic potential of this agent, 1-nitropyrene was injected i.p. or s.c. into weanling female CD rats (100 mumol/kg body weight; once a week for 4 weeks). The animals were sacrificed at 87 to 90 weeks after the first treatment. The incidences of mammary gland tumors in animals receiving injections of 1-nitropyrene by either route (59%) were significantly higher than in solvent-injected controls (37%). The incidences of adenocarcinoma in the i.p. 1-nitropyrene group (28%) and fibroadenoma in the s.c. 1-nitropyrene group (52%) were significantly higher than in the control animals (7 and 27%, respectively). These data suggest that the demonstration of the weak carcinogenicity of 1-nitropyrene is probably more a function of the length of the observation period than of the routes of administration used here. A further exploration of the effect of the route of administration involved treatment of weanling female CD rats by direct injection of 1-, 2-, or 4-nitropyrene into the mammary fat pads. A total of 2.04 mumol of the nitrocompound in dimethyl sulfoxide was injected into the mammary glands under each of the 6 left nipples. The right mammary glands were treated with the solvent only. Injections of the thoracic nipple areas were carried out on day 1; inguinal areas were treated on day 2. The animals were sacrificed after 77 weeks. The number of mammary tumor-bearing animals (23 of 28), the number with fibroadenoma (15 of 28), and the number with adenocarcinoma (19 of 28) were significantly increased in the 4-nitropyrene-treated group as compared with animals treated with only dimethyl sulfoxide.(ABSTRACT TRUNCATED AT 400 WORDS)
Serogrouping of 506 Shigella strains isolated in Singapore from 1986 to 1990 showed that Shigella flexneri (60.3%) was the most common, followed by S. sonnei (33.6%), S. boydii (3.2%) and S. dysenteriae (3%). Of the 23 Shigella serotypes identified, the predominant ones were S. flexneri types 2a and 1b, S. boydii types 1 and 5, and S. dysenteriae types 1 and 3. More than 80% of the Shigella species were resistant to at least one antimicrobial drug, and the incidence of multiresistance was particularly high in S. flexneri strains. Due to the high incidence of antimicrobial resistance, the susceptibility pattern of Shigella strains should be determined for treatment purposes.
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.
In an analysis of 127 patients with pyodermas, 38 (30%) had primary pyodermas and 89 (70%) had secondary pyodermas. Seventy-one percent (71%) of the primary pyodermas were due to Staphylococcus aureus (S. aureus). Five (5%) of the primary pyodermas were due to multiple organisms. Among the patients with secondary pyodermas, 45% were due to S. aureus, 21% Streptococci, 9% Pseudomonas and 9% Proteus species. Forty-four percent (44%) of the secondary pyodermas were due to multiple organisms. S. aureus is highly sensitive to cephalothin, cloxacillin, erythromycin, methicillin and co-trimoxazole. Streptococci are highly sensitive to cephalothin, erythromycin, ampicillin and penicillin. The gram-negative organisms are sensitive to amikacin, gentamicin, kanamycin and co-trimoxazole. Cloxacillin, or erythromycin (for patients with penicillin allergy) is the antibiotic of choice in patients with primary pyodermas. In patients with infected eczemas, first-generation cephalosporin or cloxacillin is the preferred antibiotic. In patients with infected ulcers, a combination of cloxacillin and gentamicin or a cephalosporin effective against the causative agent is most suitable.
The progress and development of microbiology services in Singapore during the last two decades are described. Rapid diagnosis, quality control, automation, nosocomial infections and national and international studies are some of the topics highlighted in this paper.
The plasmid profiles of 112 clinical isolates of Pseudomonas aeruginosa were determined by two reproducible, rapid, plasmid screening methods. Plasmid DNA was present in 15% of isolates examined. Plasmids varied in size from 1.2 X 10(6) to 60.2 X 10(6) mol. wt. The dominant serotypes encountered were O:11 and O:4, which comprised 38% and 12% of strains, respectively. Four pyocin types (1, 10, 3 and 5) dominated (respective frequencies: 56, 15, 12 and 6%). Reproducibility of pyocin typing was distinctly inferior to both plasmid profiling and serotyping. Strains of identical serotypes could be further differentiated by dissimilar plasmid profiles. Serologically untypable or polyagglutinable strains were successfully characterised by plasmid profile patterns. Thus, plasmid profiling was shown to be a useful adjunct to serotyping for the epidemiological typing of P. aeruginosa.
A coagglutination test for detection of group A streptococci in throat samples was evaluated in a multicentre study and found to be about 95% sensitive when applied to swabs taken from symptomatic patients which yielded more than 100 colonies per plate on culture. The sensitivity of the test dropped significantly when it was applied to swabs giving fewer than 100 colonies on culture. The specificity of the test was high regardless of colony count on conventional media.
A three month prospective survey of nosocomial infections in a Neurosurgery Department was carried out. Results showed that the overall nosocomial infection rate was 6.7 per 100 patient discharges with the rate of infected patients being 4.6 per 100 discharges. Patients in intensive care had two times the risk of acquiring a nosocomial infection then patients in non-intensive care. Both respiratory tract and urinary tract infections accounted for the majority (89.1%) of the nosocomial infections. 69.7% of lower respiratory tract infections were associated with the use of endotracheal tube and/or ventilatory assistance. Similarly, 87.5% of urinary tract infections were associated with the use of indwelling catheters. It is hoped that preventive measures introduced or reemphasized just before and after the study will serve to further lower the nosocomial infection rate in the Neurosurgery Department.
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A prospective three years' survey, conducted on a total of 491 children attending four schools in Singapore showed that the throat carrier rates for beta-haemolytic and group A streptococci varied from 15-31 percent and 6.6-15.7 per cent respectively. Malays had the highest streptococcal throat carrier rates followed by Indians/Pakistanis and the Chinese. There was no significant difference in streptococcal throat carrier rates between the sexes. Children from lowest family income of less than $500/- and those living in attap/zinc houses had the highest streptococcal carriage rates. On the other hand, children from households where two or less than two persons shared a room had the lowest beta-haemolytic and group A streptococcal throat carrier rates. No marked variation in the incidences of streptococcal carriage rates was detected during the rainy and dry seasons. Twelve (2.4 percent) of the children haboured beta-haemolytic streptococci on their healthy skin. Ten (2 percent) of these children were colonized by group A streptococci. T5/11/12/27/44 was found to be the most predominant pattern during the period of study. Other common T patterns were T3/13/B3264, T8/25/Imp19 and T4/24/26/28/29/46. 19(17.3 percent) of the throat group A strains were M-typable and 11 M types were differentiated.