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Biomedical subjects

J M Ling

Publications and source records attributed to J M Ling.

At least 19 recordsLinked to original sources
PubMed2006

CTX-M-producing Salmonella spp. in Hong Kong: an emerging problem.

Two Salmonella enterica serovar Typhimurium isolates and one S. enterica serovar Enteritidis isolate that were resistant to 4 microg cefotaxime ml-1 and produced CTX-M-type extended-spectrum beta-lactamases (ESBLs) were characterized from patients in Hong Kong during 2003-2004. The S. Typhimurium strain isolated in 2003 produced a CTX-M-9 ESBL and harboured a blaCTX-M-9 gene that was associated with a class I integron-containing gene cassette and orf513 similar to those of In60. The second S. Typhimurium strain and the S. Enteritidis strain, both isolated in 2004, produced CTX-M-14; the former also produced TEM-1. The blaCTX-M-14 gene in these two isolates was associated with the insertion sequence ISEcp1. The CTX-M genes were present on a transferable plasmid of 62, 70 or 92 kb. PFGE of XbaI-restricted total DNA from the two S. Typhimurium isolates indicated that they were not clonally related. These three isolates were also resistant to one of the other non-beta-lactam antimicrobial agents tested. This is the first report of a CTX-M-9 ESBL in Salmonella in Hong Kong and the presence of blaCTX-M-9 and blaCTX-M-14 in S. Typhimurium.

Adult↗
PubMed2005

The safety and efficacy of oral dextrose for relieving pain following venepuncture in neonates.

The objective of this study was to assess the efficacy and safety of oral 30% dextrose during venepuncture in neonates. Neonates admitted in the Special Care Nursery for jaundice from September 200 to January 2001 were recruited for this double-blind randomised controlled trial. The intervention consisted of administration of either 2 ml of oral 30% dextrose or 2 ml of sterile water 2 minutes before venepuncture. The primary outcome measure was the cumulative Neonatal Infant Pain Scale (NIPS) score at 3 minutes after venepuncture and the duration of cry assessed from a videotaped recording. Twenty-six neonates received 30% dextrose and 26 neonates received sterile water. The cumulative NIPS score at 3 minutes (median, IQR) after venepuncture for neonates given 30% dextrose (13, 6.8-21) was significantly (p = 0.03) lower than that for neonates given sterile water (21, 13.8-21). The duration of cry in neonates given 30% dextrose (median 45 sec IQR 1.5-180.8 sec) was significantly (p = 0.03) shorter than that in neonates given sterile water (median 191 sec IQR 52.3-250 sec). No neonates developed diarrhoea, fever or rash during the 24 hour observation period. Both the intra-rater (ICC 0.993 95% CI 0.988-0.996) and inter rater (ICC 0.988 95% CI 0.980-0.993) agreement on the 3-minute NIPS score were good. In conclusion oral 30% dextrose given 2 minutes before venepuncture was effective in reducing neonatal pain following venepuncture. It is a simple, safe and fast acting analgesic and should be considered for minor invasive procedure in term neonates.

Administration, Oral↗
PubMed2003

What have we learnt from community-acquired infections in Hong Kong?

This study was initiated throughout Hong Kong, to reveal the characteristics of community-acquired infections. All specimens collected by general practitioners from infected patients were followed prospectively, and those that were culture-positive were analysed. Four thousand seven hundred and forty-one specimens were collected from 3977 patients by 89 doctors from July 2000 to October 2001. The most common specimens were throat swabs (33%), urine (26%) and sputa (16%). The average culture-positive rate was 28%. The most common organisms were Escherichia coli (18%), beta-haemolytic streptococci (15%) and Staphylococcus aureus (12%). Fluoroquinolone resistance was relatively high (up to 35%) in organisms commonly causing urinary tract infection (E. coli, Proteus and Morganella). Although none of the pneumococci was resistant to penicillin 1 mg/L, the proportion with intermediate resistance (0.1-1 mg/L) was alarming (81%). There were three strains of methicillin-resistant S. aureus. A decrease in ampicillin resistance but a high prevalence of macrolide resistance were noted in Haemophilus influenzae. All Neisseria gonorrhoeae isolates were resistant to penicillin, up to 79% to the fluoroquinolones, 15% to spectinomycin, but all were susceptible to ceftriaxone. Respiratory pathogens (Streptococcus pneumoniae, beta-haemolytic streptococci and H. influenzae) were relatively susceptible to the newer fluoroquinolones (0-2%, 0.5-6% and 2% resistant, respectively) or third-generation cephalosporins (0-2% resistant). The distribution of organisms and their antibiotic resistance varied over time. Thus frequent surveillance is needed to provide information on the drugs of choice for different infections.

Adolescent↗
PubMed2003

Mutations in topoisomerase genes of fluoroquinolone-resistant salmonellae in Hong Kong.

A total of 88 salmonella isolates (72 clinical isolates for which the ciprofloxacin MIC was >0.06 microg/ml, 15 isolates for which the ciprofloxacin MIC was < or =0.06 microg/ml, and Salmonella enterica serotype Typhimurium ATCC 13311) were studied for the presence of genetic alterations in four quinolone resistance genes, gyrA, gyrB, parC, and parE, by multiplex PCR amplimer conformation analysis. The genetic alterations were confirmed by direct nucleotide sequencing. A considerable number of strains had a mutation in parC, the first to be reported in salmonellae. Seven of the isolates sensitive to 0.06 micro g of ciprofloxacin per ml had a novel mutation at codon 57 of parC (Tyr57-->Ser) which was also found in 29 isolates for which ciprofloxacin MICs were >0.06 micro g/ml. Thirty-two isolates had a single gyrA mutation (Ser83-->Phe, Ser83-->Tyr, Asp87-->Asn, Asp87-->Tyr, or Asp87-->Gly), 34 had both a gyrA mutation and a parC mutation (29 isolates with a parC mutation of Tyr57-->Ser and 5 isolates with a parC mutation of Ser80-->Arg). Six isolates which were isolated recently (from 1998 to 2001) were resistant to 4 micro g of ciprofloxacin per ml. Two of these isolates had double gyrA mutations (Ser83-->Phe and Asp87-->Asn) and a parC mutation (Ser80-->Arg) (MICs, 8 to 32 microg/ml), and four of these isolates had double gyrA mutations (Ser83-->Phe and Asp87-->Gly), one parC mutation (Ser80-->Arg), and one parE mutation (Ser458-->Pro) (MICs, 16 to 64 micro g/ml). All six of these isolates and those with a Ser80-->Arg parC mutation were S. enterica serotype Typhimurium. One S. enterica serotype Typhi isolate harbored a single gyrA mutation (Ser83-->Phe), and an S. enterica serotype Paratyphi A isolate harbored a gyrA mutation (Ser83-->Tyr) and a parC mutation (Tyr57-->Ser); both of these isolates had decreased susceptibilities to the fluoroquinolones. The MICs of ciprofloxacin, levofloxacin, and sparfloxacin were in general the lowest of those of the six fluoroquinolones tested. Isolates with a single gyrA mutation were less resistant to fluoroquinolones than those with an additional parC mutation (Tyr57-->Ser or Ser80-->Arg), while those with double gyrA mutations were more resistant.

Anti-Infective Agents↗
PubMed2002

Distribution of enterococci in Hong Kong.

OBJECTIVES: To study the distribution of hospital isolates of enterococci from urines, bile, blood and body fluids and to evaluate different methods for the identification of enterococci. METHODS: Enterococci isolated from urine, bile, blood and body fluids collected during 1997 and 1998 were identified by polymerase chain reaction (PCR), API 20 Strep and conventional biochemical tests. RESULTS: A total of 498 non-duplicate enterococci were studied: 398 and 43 isolates from urine and bile, respectively, 49 from blood, two from cerebrospinal fluid and six from body fluids. Both API 20 Strep and PCR gave the same identification results for 240 Enterococcus faecalis isolates, 45 E. faecium isolates and one isolate each of E. gallinarum and E. Casseliflavus. These isolates were re-defined by conventional biochemical tests. PCR could correctly identify 303 (98%) isolates while API 20 Strep could only correctly identify 287 (93%) isolates (99% of E. faecalis and 57-87% of the other Enterococcus sp.). Thus, PCR was used in the identification of the remaining isolates and the identity of isolates other than E. faecalis was subsequently confirmed by biochemical tests. CONCLUSIONS: The majority of enterococci isolated was E. faecalis (81%) while only 15% were E. faecium and 4% the other enterococcal species. PCR could correctly identify E. faecalis while the identity of other enterococcal species had to be confirmed by biochemical tests.

Bacterial Typing Techniques↗
PubMed2001

Molecular epidemiological analysis of Salmonella enterica serotype Derby infections in Hong Kong.

OBJECTIVES: We aimed to study the antimicrobial susceptibilities and molecular epidemiology of Salmonella enterica serotype Derby, a unique and common salmonella serotype in Hong Kong. METHODS: Salmonella Derby strains isolated from stools of patients in a large general hospital in Hong Kong from 1989 to 1994 and from food samples isolated in the Public Health Laboratory were randomly selected and investigated for the antimicrobial susceptibilities by determining the minimal inhibitory concentrations of 19 antimicrobial agents and their relatedness using plasmid analysis, ribotyping, pulsed-field gel electrophoresis (PFGE) and total DNA fingerprinting. RESULTS: About 50% of the 127 isolates studied were susceptible to all the 19 antibiotics tested, although resistance to tetracycline (49%) and sulfamethoxazole (38%) was high. Only 12% did not harbour any detectable plasmids, while the rest contained plasmids in 51 profiles. There were two predominant clones, one comprising of 35% of isolates that could not be pulsotyped because discrete bands were not discernible after PFGE and another comprising 34% of isolates that could be pulsotyped. The remaining 31% belonged to a variety of types. CONCLUSIONS: Approximately 70% of S. Derby belonging to two clones were endemic in the community, while the remaining isolates belonged to a variety of types which were probably a result of sporadic infection. The sources of human infections were foods, since most isolates from foods also belonged to the two endemic clones. Typing of S. Derby isolates from other sources such as animals or the environment would help elucidate how foods were contaminated. PFGE might not be universally applicable to all salmonella strains.

Adolescent↗
PubMed2001

Epidemiological analysis of Salmonella enterica serotype typhimurium from Hong Kong by ribotyping and pulsed-field gel electrophoresis.

We investigated the antimicrobial susceptibilities and molecular epidemiology of 200 strains of Salmonella enterica serotype typhimurium isolated from 1989 to 1996 in Hong Kong. Only 22% of strains were susceptible to all 19 antibiotics tested but all were susceptible to second- and third-generation cephalosporins. Up to 9% of strains were resistant to 0.12 mg/l concentrations of ciprofloxacin or ofloxacin but none were resistant to 1 or 2 mg/l concentrations of these 2 drugs, respectively. The isolates were grouped into 15 types by ribotyping with restriction endonuclease EcoRI and into 53 types by pulsed-field gel electrophoresis of XbaI-restricted DNA fragments. When DNA fragments of the ribotypes and pulsotypes were pooled and analyzed 87 types resulted, 76 (87%) of which were of > 90% similarity and were grouped into 15 clusters. About 60% of the isolates belonged to 3 clusters, which probably represented 3 clones endemic in the community. The rest of the isolates were of a large variety of types or clusters. For epidemiological purposes analysis of pooled results from different molecular techniques would be more discriminative than results from individual techniques alone.

Anti-Bacterial Agents↗
PubMed2000

Molecular methods for the epidemiological typing of Salmonella enterica serotype Typhi from Hong Kong and Vietnam.

A total of 217 and 73 strains of Salmonella enterica serotype Typhi isolated from 1985 to 1997 in Hong Kong and in 2 months of 1989 and 1990 in Vietnam, respectively, were studied. These isolates were typed by plasmid profile analysis, plasmid fingerprinting, ribotyping with PstI, and total DNA fingerprinting with NarI. There appeared to be no major outbreak of typhoid fever in Hong Kong during the study period since there was considerable heterogeneity among the isolates. Isolates from Hong Kong were different from those from Vietnam. Thirty-seven percent of Vietnamese isolates belonged to two predominant clones, with the rest being heterogeneous in nature. Total DNA fingerprinting supplemented with ribotyping could be a reliable and rapid method for epidemiological typing of S. enterica serotype Typhi.

Bacterial Typing Techniques↗
PubMed1999

Vancomycin in Oregon: who's using it and why.

OBJECTIVE: To determine the proportion of vancomycin orders that are appropriate according to national guidelines and to identify targets for educational messages. DESIGN: Population-based study of vancomycin use in Oregon during a 3-week period. Survey of pharmacists, prospective flagging of vancomycin orders, and data abstraction from patient charts using standardized forms. SETTING: Nonpsychiatric hospitals in Oregon. RESULTS: Four (6%) of the 66 Oregon hospitals had pharmacy restrictions on initial vancomycin orders. Sixty-four (97%) of the hospitals participated in the study of indications for use; 293 vancomycin orders were reported; 3.8 courses were initiated per 1,000 patient-days. Indications for use were determined for 266 (91%); of these, 159 (60%) were deemed appropriate. Of uses for prophylaxis, empirical treatment of suspected gram-positive infection, and treatment of documented gram-positive infection, 57%, 56%, and 65%, respectively, were appropriate. Of hospitals with <250, 251-475, and >475 licensed beds, 65%, 58%, and 57% of vancomycin orders were appropriate. No single medical specialty accounted for >16% of inappropriate vancomycin use. CONCLUSIONS: Vancomycin was used inappropriately by physicians of many different specialties, in hospitals of all sizes, and in sundry clinical situations. The problem of inappropriate vancomycin use does not lend itself to solution by educational strategies targeted at specific subgroups; restrictions by hospital pharmacies may be required.

Anti-Bacterial Agents↗
PubMed1999

Markedly different rates and resistance profiles exhibited by seven commonly used and newer beta-lactams on the selection of resistant variants of Enterobacter cloacae.

Seven beta-lactam antibiotics (cefepime, cefoperazone, ceftazidime, ceftriaxone, cefamandole, imipenem and meropenem) were tested for their potential to select resistance in standard and clinical strains of Enterobacter cloacae (n = 9). The strains were subcultured daily with the test antibiotics at doubling concentrations starting at 0.125 x MIC. Development of resistance throughout the passages was detected by a disc diffusion test. Ceftazidime, ceftriaxone and cefamandole selected resistance at a faster rate than cefoperazone, cefepime and meropenem. Imipenem did not select resistance in the nine strains tested and was the only antibiotic that eradicated all the strains during selection. The resistance patterns of strains selected by meropenem, cefepime and the other cephalosporins were markedly different, although cross-resistance to the early generation cephalosporins was common. The resistance phenotypes of most strains remained stable upon serial passages in antibiotic-free medium. The findings of this study highlight the importance of the choice of antibiotic for therapy not only on the basis of its antibacterial activity, but also on its potential to select resistance to itself and other antibiotics.

Anti-Bacterial Agents↗
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↗
PubMed1998

Evaluation of a selective transport medium for gastric biopsy specimens to be cultured for Helicobacter pylori.

Since the means of culturing Helicobacter pylori may not be available in some laboratories, prolonging the survival of this organism during transportation is a major concern in terms of improving detection rates. A selective transport medium was evaluated for the preservation of H. pylori from 254 gastric biopsy specimens collected from a rural area in China where culturing is not feasible. Gastric biopsy specimens were inoculated in sterile broth consisting of brain heart infusion (BHI) broth, horse serum, and yeast extract supplemented with vancomycin, amphotericin B, and nalidixic acid (VAN). Of the 254 biopsy specimens, 238 were identified by histology to have H. pylori infection. Total rates of recovery of H. pylori from the H. pylori-positive gastric biopsy specimens stored in the BHI-VAN broth ranged from 76 to 46% after storage of specimens for 5 to 9 days. In conclusion, the selective medium is useful for prolonging the survival of H. pylori in gastric biopsy specimens for which immediate culture is not feasible.

Adult↗
PubMed1998

Antimicrobial susceptibilities and molecular epidemiology of Salmonella enterica serotype enteritidis strains isolated in Hong Kong from 1986 to 1996.

The incidence of salmonellosis has been increasing in Hong Kong since 1989. The most common Salmonella enterica serotype isolated in 1994 was S. enteritidis. The antimicrobial susceptibilities and molecular epidemiology of 275 S. enteritidis strains isolated in this locality between 1986 and 1996 were studied. Over 99% of the isolates were susceptible to 17 of the 19 antimicrobial agents tested. One isolate harbored an autotransferring plasmid that confers resistance to tetracycline and trimethoprim-sulfamethoxazole. Another isolate harbored a mobilizable plasmid that confers resistance to ampicillin and cephalothin. This isolate was found to produce a beta-lactamase with a pI of 5.2. A total of 264 isolates (96%) were found to harbor one to five plasmids, and the majority (254) harbored a 60-kb plasmid. Of these isolates, 94% contained identical 60-kb plasmids. Based on plasmid profiles, plasmid and chromosomal fingerprints, ribotypes, and randomly amplified polymorphic DNA (RAPD) patterns, 170 (62%) isolates were allocated to group 1b. About 90% of isolates had identical or similar DNA fingerprints, ribotypes, and RAPD patterns, suggesting that a predominant clone of S. enteritidis was circulating in Hong Kong during the period being studied.

Anti-Bacterial Agents↗
PubMed1997

Restriction endonucleases in clinical isolates of Shigella spp.

Thirteen restriction endonuclease-containing strains were isolated from a collection of 186 clinical isolates of Shigella spp. Among these, eight and five isolates carried isoschizomers of EcoRII and NciI, respectively. The former restriction-modification (R-M) system was homologous to that of EcoRII and was located on plasmids with sizes of 46.6 or 55.6 kb. Isolates producing NciI isoschizomers contained a 5.7-kb non-transferable plasmid. Together with antimicrobial susceptibility tests and plasmid profile studies, it is concluded that these two R-M systems are not widely spread but confined to strains with similar antibiotic resistance and plasmid profile.

Anti-Bacterial Agents↗
PubMed1997

Antibiotic exposure and its relationship to postantibiotic effect and bactericidal activity: constant versus exponentially decreasing tobramycin concentrations against Pseudomonas aeruginosa.

In vitro postantibiotic effects (PAEs) exhibited by a standard strain of Pseudomonas aeruginosa following exposure to tobramycin at constant concentrations were compared to those at exponentially decreasing concentrations. Exposure to a constant concentration showed more extensive bacterial killing and resulted in longer PAEs at comparable areas under the concentration-time curves above the MIC. This phenomenon suggests a significant contribution of pharmacokinetics to antimicrobial pharmacodynamics.

Anti-Bacterial Agents↗
PubMed1996

Examination of coumarins, flavonoids and polysaccharopeptide for antibacterial activity.

1. Coumarins, flavonoids and polysaccharopeptide were tested for antibacterial activity. 2. The bacteria used for this study included clinical isolates of Staphylococcus aureus, Shigella flexneri, Salmonella typhi, Escherichia coli and Pseudomonas aeruginosa. 3. Most of the coumarins tested failed to inhibit the bacteria at 25 mg/l. Edultin at 128 mg/l inhibited 4 of the 8 P. aeruginosa strains and 1 of the S. aureus strains tested. O-acetylcolumbianetin and imperatorin did not inhibit any isolate, even at 128 mg/l. 4. When tested at the dose of 128 mg/l, the flavonoids (rutin, naringin and baicalin) inhibited 25% or less of P. aeruginosa and only baicalin was active against S. aureus. 5. Arbutin and 4-(beta-D-glucopyranosyloxyl)-benzaldehyde inhibited 3 of the 8 P. aeruginosa strains when tested at 128 mg/l. 6. Polysaccharopeptide from the fungus Coriolus versicolor failed to inhibit any P. aeruginosa or S. aureus strain at 128 mg/l.

Bacteria↗