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Biomedical subjects

D J Lyon

Publications and source records attributed to D J Lyon.

At least 37 records · Page 2Linked to original sources
PubMed1998

Antimicrobial resistance in Shigella flexneri and Shigella sonnei in Hong Kong, 1986 to 1995.

Three hundred and thirty-three Shigella isolates obtained in 1986 to 1995 were tested for their susceptibilities to 19 antimicrobial agents. Nalidixic acid resistance had emerged in 59.6% of Shigella flexneri isolates during 1994 to 1995, with all tested resistant isolates having the mutation in gyrA encoding the Ser-83 alteration. Multiresistance (resistance to four or more agents) was more common in S. flexneri than in Shigella sonnei.

Anti-Infective Agents↗
PubMed1997

Comparison of E-test with agar dilution for determining susceptibility of Streptococcus pneumoniae to penicillin.

Minimum inhibitory concentrations (MICs) of penicillin for Streptococcus pneumoniae were determined by the E-test and the agar dilution method. Ninety Streptococcus pneumoniae strains were tested, of which 16 were resistant, 33 intermediate, and 41 susceptible by agar dilution. By the E-test, 80 (88.9%) strains agreed with these determinations within one log2 dilution step, and no strains disagreed by more than two dilution steps. Sixty-eight of the 70 strains with discrepant MICs read lower in the E-test, resulting in 15 strains being placed in different susceptibility categories when classified by this test. Exact MICs rather than classification groups should be used to determine appropriate antibiotic therapy, since small differences in MICs determined by different methods can lead to a significant degree of misclassification.

Colony Count, Microbial↗
PubMed1997

Living with methicillin-resistant Staphylococcus aureus: a 7-year experience with endemic MRSA in a university hospital.

A review of our infection control records revealed 3,159 new isolations of methicillin-resistant Staphylococcus aureus (MRSA) from 1988 to 1994. Prior to this period, our approach to MRSA had changed from eradication to containment measures. We found a decline in MRSA rates from 11.4 to 5.2 first isolations per 1,000 deaths and discharges over the study period.

Cross Infection↗
PubMed1996

Varicella exposure in a neonatal intensive care unit: emergency management and control measures.

We describe an exposure of varicella zoster virus in our neonatal intensive-care unit and the emergency procedures instituted to prevent an outbreak. Fifty-seven infants and 129 staff members were exposed but none developed chickenpox. The measures included rapid identification of varicella antibody status in all neonates and those staff members with uncertain history of varicella infection; cohorting of exposed infants according to immune status; and prompt administration of varicella zoster immunoglobulin to susceptible patients. The recommendation of the American Academy of Pediatrics did not accurately predict the immune status of preterm infants, as only one of the eight susceptible infants would have qualified for immunoglobulin prophylaxis if their guidelines had been followed. Mass screening of all exposed infants using the varicella zoster enzyme linked immunosorbent assay (ELISA) test was the only reliable means of determining the immune status. Of the four risk factors evaluated for the prediction of antibody status: gestational age, postnatal age, birthweight and episodes of blood transfusion, only postnatal age was found to independently predict the immune status of our patients. Because varicella zoster susceptible staff members are difficult to identify on the basis of history, we suggest that prospective screening of staff in high-risk units be undertaken and vaccination with live varicella vaccine be offered to susceptibles.

Antibodies, Viral↗
PubMed1996

In-vitro susceptibility of isolates of methicillin-resistant Staphylococcus aureus 1988-1993.

MICs for 423 strains of methicillin-resistant Staphylococcus aureus (MRSA) isolated in Hong Kong during 1988-1993 were performed for 15 antimicrobial agents: erythromycin, chloramphenicol, tetracycline, minocycline, gentamicin, netilmicin, trimethoprim, rifampicin, fusidic acid, ciprofloxacin, vancomycin, teicoplanin, sparfloxacin, clinafloxacin and RP 59500 (quinupristin/dalfopristin). Susceptibility to antibiotics generally remained stable throughout the study period, with the exception of the quinolones. Resistance to ciprofloxacin (breakpoint 4 mg/L) increased from a low of 9% in 1988 to a high of 82% in 1993. For sparfloxacin the corresponding figures were 9% and 78%, respectively. Six (1%) clinafloxacin-resistant strains were found. MIC50s and MIC90s of clinafloxacin increased from < or = 0.06 mg/L and 0.25 mg/L in 1988 to 1.0 mg/L and 2.0 mg/L, respectively, in 1993. All 423 strains were phage typed (typability 70%) and a diversity of phage types which changed during the observation period, with 13 dominating types, was observed. Ciprofloxacin resistance occurred in 12 of the dominating types, in 46 non-typable strains, and also in 23 strains of different, sporadically occurring types, indicating that the emergence of quinolone resistance was not due to dissemination of a single or few MRSA clones. The usefulness of quinolones in the treatment of MRSA infections is likely to be seriously constrained by the emergence of resistance. MICs for RP-59500 were < or = 2 mg/L for all isolates, suggesting that this agent merits further evaluation as an anti-MRSA agent. All MRSA remained susceptible to vancomycin and teicoplanin throughout the study period.

Anti-Infective Agents↗
PubMed1996

Aetiology of acute diarrhoea in hospitalized children in Hong Kong.

To determine the role of enteric pathogens in acute childhood diarrhoea in Hong Kong, 388 children with diarrhoea and 306 children of similar age without diarrhoea were evaluated in a hospital-based study during a one-year period from August 1994 to July 1995. Of the diarrhoeal cases, 55% were under 1 year and 95% were below 5 years of age. On admission, 22% had some dehydration but none was severely dehydrated. All children were well nourished. Oyer 60% of children with diarrhoea had one or more pathogens in their stool. Rotavirus was the most commonly isolated pathogen (34.6%), followed by Salmonella (23.3%), Campylobacter (4.7%) and Shigella (2.1%). Rotavirus was not assessed in the controls and was detected mainly during the winter months December to February. Bacterial pathogens were identified more commonly in diarrhoea patients (30%) than in controls (5.6%) (P < 0.001). Despite rapid recent socioeconomic development in Hong Kong, non-typhoidal Salmonella diarrhoea remains a significant local problem in infants under 1 year. Further detailed assessment of the transmission and prevention of this infection is required.

Acute Disease↗
PubMed1996

Molecular epidemiology of Escherichia coli diarrhea in children in Hong Kong.

This pediatric hospital-based study of 388 diarrhea cases and 306 controls analyzed predominant E. coli colonies from primary culture (253 cases and 177 controls) with eight DNA probes for enteropathogenic, enterotoxigenic, enteroaggregative, and diffusely adherent E. coli. Only enteropathogenic E. coli adherence factor was identified significantly more frequently in cases (10) than in controls (0).

Adolescent↗
PubMed1996

Self-inflicted bacteraemia and fungaemia in Vietnamese migrants.

From early 1993, we received a number of blood cultures, all from Vietnamese inmates of the Whitehead Detention Centre, the biggest detention camp in Hong Kong, which grew unusual organisms. Upon follow-up, the majority of the patients were found to abscond from the hospital a few days after having been admitted with a clinical picture of septic shock. During the period from March 1993 to late 1994, we noted a total of 25 positive blood cultures from 21 previously healthy Vietnamese migrants with this syndrome. The mean age was 27.8 years and 20 were males. The organisms isolated from the blood cultures were of low pathogenicity such as Saccharomyces cerevisiae, Trichosporon spp., Baciflus spp. and Micrococcus spp. Fourteen of the patients complained of abdominal pain and 3 others had apical pneumothoraces. Eighteen had shock requiring resuscitation. Multiple puncture or needle marks were found in 11 patients, mainly involving the lower limbs. One patient admitted inducing illness by self-injection, and it was suspected that all these infections were self-inflicted. The range of hospitalization was 1-13 days (mean 3.05 days). Eighteen of the 21 patients absconded.

Adolescent↗
PubMed1996

Rapid emergence of penicillin-resistant pneumococci in Hong Kong.

The prevalence of penicillin resistance in Streptococcus pneumoniae isolated at the Prince of Wales Hospital, Hong Kong, rose from 6.6% of sputum isolates in the first quarter of 1993 to 55.8% of isolates in the second quarter of 1995. Most of the isolates were also resistant to co-trimoxazole, tetracycline, choramphenicol and erythromycin. Type 19F was the most common capsular type in 1993-1994, comprising 40.0% of typed isolates in this period. Type 23F emerged in 1995 as the predominant type, making up 62.2% of typed isolates in the first 2 quarters of 1995. A high population density and excessive community use of antibiotics are likely to be factors promoting the rapid emergence of multiply-resistant pneumococci in Hong Kong.

Drug Resistance, Microbial↗
PubMed1996

Antimicrobial susceptibility and extended-spectrum beta-lactamases of Hong Kong isolates of enterobacteriaceae.

High levels of resistance to extended-spectrum cephalosporins have been reported in the Western Pacific area but data on the prevalence of extended-spectrum beta-lactamases (ESBLs) is more scanty. 370 Hong Kong blood culture isolates of Enterobacteriaceae isolated in the years 1990 and 1995 were evaluated for resistance to 15 antibiotics and the presence of ESBLs. 1995 isolates showed increased levels of resistance for beta-lactams, trimethoprim, ciprofloxacin and aminoglycosides. The proportion of E. coli harbouring ESBLs was 1/61 (1.6%) in 1990 and 2/77 (2.6%) in 1995. The prevalence in Klebsiella spp. rose from 1/36 (2.8%) in 1990 to 5/49 (10.2%) in 1995. ESBLs were found most frequently in Enterobacter spp. and were present in 7/29 (24.1%) of 1990 isolates and 5/22 (22.7%) of 1995 isolates. ESBLs may not be detectable in routine susceptibility testing and appropriate screening methods such as double disc screening tests are necessary to accurately determine ESBL prevalence.

Drug Resistance, Microbial↗
PubMed1995

Intravenous ciprofloxacin as treatment for patients with acute suppurative cholangitis: a randomized, controlled clinical trial.

One hundred consecutive patients with acute suppurative cholangitis were randomized in a prospective, controlled clinical trial to receive either ciprofloxacin (200 mg bd iv) or triple therapy comprising ceftazidime (1 g bd iv), ampicillin (500 mg qds iv) and metronidazole (500 mg tds iv); 46 and 44 patients in the ciprofloxacin and triple therapy groups respectively were suitable for inclusion in the analysis of efficacy. In two-thirds of the patients biliary obstruction was caused by ductal calculi and in one-third by malignant or benign strictures of the biliary tract. Bacteraemia was documented in 38% of patients in the ciprofloxacin group and in 34% of patients in the triple therapy group, while bile cultures were positive in 87% and 92% of patients in the ciprofloxacin and triple therapy groups respectively. Escherichia coli, Klebsiella spp. and Enterococcus spp. were the most common biliary isolates. Eighty-five per cent of evaluable patients in the ciprofloxacin group and 77% of those in the triple therapy group responded to therapy. The mean durations of fever, septicaemic shock and hospitalization were also similar in the two treatment groups. Six (13%) patients in the ciprofloxacin group and seven (16%) in the triple therapy group required urgent endoscopy or surgery for uncontrolled infection. Recurrence of fever after an initial response was documented in one (2%) patient receiving ciprofloxacin and in three (7%) patients receiving triple therapy. The incidences of mortality were 4% in the ciprofloxacin group and 2% in the triple therapy group. The results of this study suggest that ciprofloxacin alone is adequate empirical therapy for patients with cholangitis.

Acute Disease↗
PubMed1995

A prospective study of the microbiological environment of the genitourinary tract in Hong Kong Chinese women during pregnancy.

Microbiological colonization of the genitourinary tract in pregnancy is associated with an increased risk of preterm labour and delivery. In our population, the risk of preterm labour is relatively low, and the purpose of this study was to examine the microbiological environment of the genitourinary tract to determine whether it differed from that reported in populations where the rate of preterm delivery is higher. A prospective study was made in 367 unselected women between 16 and 24 weeks' gestation. Although the rate of colonization with Candida species was higher than in most other studies (30.2%), colonization with Gardnerella, Group B Streptococcus, Trichomonas and Chlamydia was uncommon (1.9%, 0.8%, 0.6% and 3.5% respectively). Significant bacteriuria was also uncommon, occurring in only 4.9% of cases. The results of this study confirmed a relatively low incidence of colonization of the genitourinary tract in this population of women with a low incidence of preterm delivery. These findings suggest that low levels of colonization may be related to a low incidence of preterm delivery in our patients.

Adult↗
PubMed1994

In-vitro antimicrobial susceptibility and beta-lactamases of ampicillin-resistant Escherichia coli in Hong Kong.

Three hundred and forty isolates of ampicillin-resistant Escherichia coli isolated from blood, bile and urine were collected during 1984 and 1988 in the Prince of Wales Hospital, Hong Kong and MICs of 21 beta-lactam antibiotics were determined. beta-Lactamases were identified by isoelectric focusing, and TEM-1 was found in 89.1% of isolates, PSE-1 in 3.2%, and OXA-1 in 2.9% of strains. Ten isolates (2.9%) possessed both TEM-1 and PSE-1. Five isolates (1.5%) produced only chromosomal enzymes and one produced an unidentified enzyme which focussed at pI 6.0. All but seven of 274 TEM-1 producers and all nine OXA-1 producers reacted with oligonucleotide probes in a colony blot technique. All isolates contained plasmids and 229 of 318 (72.0%) isolates transferred the ampicillin resistance factor. Of 42 transconjugants of TEM-1 producers selected for study, 39(92.9%) had only a single transferable plasmid bearing the TEM-1 gene.

Ampicillin Resistance↗