Otago Diagnostic Laboratories' (ODL) Method for the detection of beta-lactamases in Enterobacteriaceae.

AIM: The rapid evolvement of beta-lactamases in Enterobacteriaceae is an important concern and the clinical microbiology laboratory is required to detect them, where possible, using a rapid, reliable, simple and low cost methodology. MATERIALS AND METHODS: A disc diffusion method using NCCLS breakpoints, Jarlier's principle and cefoxitin test for AmpC was carried out. It incorporated seven antimicrobial discs in one agar plate: cefotaxime, aztreonam, amoxicillin-clavulanate, ceftazidime, cefpodoxime, cefepime and cefoxitin. NCCLS disc confirmation test for extended-spectrum beta-lactamase (ESBL) was carried out simultaneously. RESULTS: AmpC, ESBL, CTX-M, and K1 were detected using these tests. The prevalence of ESBL was <1% in the hospital. CONCLUSION: The method is recommended for the phenotypic detection of beta-lactamases in Enterobacteriaceae or for confirmation after the results are obtained by conventional automated systems.

Prevalence of enterococcal high-level aminoglycoside resistance in Japan. Comparative detection by three methods.

A total of 250 strains of enterococci isolated in Kumamoto University Hospital, Japan, during the period from January to March 1992 were tested for high-level aminoglycoside resistance. Brain-heart infusion (BHI) agar plates supplemented with 1000 micrograms/ml of gentamicin or 2000 micrograms/ml of streptomycin detected 164 (66%) isolates resistant to either gentamicin or streptomycin alone, or both, and consisted of 107 (43%) resistant to gentamicin and 96 (38%) resistant to streptomycin. The Vitek Gram-Positive Susceptibility card (GPS-TA) revealed high correlations with those by agar screens, the results indicating a sensitivity of 100% and 99% to gentamicin and streptomycin, respectively, and 100% specificity to both. Also, the microdilution tests of the National Committee for Clinical Laboratory Standards (NCCLS) showed 100% and 92% sensitivity to gentamicin and streptomycin, respectively, and no false resistance (100% specificity) when compared with the results by agar screens.

Comparison of three methods for the molecular typing of Singapore isolates of enterococci with high-level aminoglycoside resistances.

Enterococci are frequently isolated as nosocomial pathogens and have often acquired intrinsic drug resistances. Molecular typing techniques have been developed to assist in epidemological and infection control measures. This study investigates enterococci with high-level aminoglycoside resistance (HLAR) from the National University Hospital (NUH) of Singapore, and evaluates and compares three methods for typing: restriction enzyme analysis by conventional gel electrophoresis [restriction fragment length polymorphism (RFLP)], pulsed-field gel electrophoresis (PFGE), and polymerase chain reaction (PCR) using random amplified polymorphic DNA (RAPD). Fifty-two isolates of Enterococcus faecalis and 13 isolates of Enterococcus faecium were used for the study. The numbers of patterns obtained for E. faecalis and E. faecium were 26 and 4, respectively by the RFLP method, and very similar discrimination was obtained by PFGE. RAPD PCR results were not reliably reproducible. A single pattern type by RFLP accounted for 16 of the E. faecalis isolates, suggesting hospital spread.

Gastrointestinal colonisation of vancomycin-resistant enterococcus in a Singapore teaching hospital.

Vancomycin-resistant enterococcus (VRE) has become an important nosocomial pathogen in many countries but is still rare in Singapore. A study was conducted from January to March 1997 at a 900-bed teaching hospital to determine the prevalence of intestinal colonisation of VRE in the patient population. A total of 299 consecutive stool specimens received by the microbiology laboratory for routine testing were plated onto two different selective media for comparison. VRE isolated were phenotypically characterised using minimum inhibitory concentrations (MICs) to vancomycin and teicoplanin and then typed using pulsed-field gel electrophoresis (PFGE) with Smal digestion of DNA. VRE were detected in the stool of 35 patients (12.3%). This group consisted of four isolates with VanB (one Enterococcus faecalis and three E. faecium) and 31 isolates with VanC (30 E. casseliflavus and one E. gallinarum). Two patients (0.7%) carried isolates (both VanB) with high level resistance to vancomycin (MIC > or = 256 microg/ml) while the rest had isolates of low level resistance (MIC = 8 microg/ml). Except for isolates from the same patients, PFGE patterns were diverse, suggesting that the VRE isolates were genotypically different and possibly introduced from many sources. This study demonstrates that VRE colonisation is not uncommon in the Singapore patient population.

Prevalence in Singapore of enterococci with high-level resistance to aminoglycosides and comparison of three methods for their detection.

The first study of the prevalence in Singapore of enterococci with high-level resistance to aminoglycosides has been made in the National University Hospital. From March to June 1992, 225 isolates were studied by means of three methods: (1) use of brain-heart infusion (BHI) agar incorporating the antibiotic; (2) microdilution of the antibiotic in broth; and (3) use of high content antibiotic discs. The BHI agar was the reference method. Of the total, 49 (22%) isolates were resistant to gentamicin, 86 (38%) to streptomycin, 82 (36%) to kanamycin and 93 (41%) to one or more of the agents. Results of the disc diffusion method correlated completely with the BHI agar method. The broth microdilution method showed a 100, 90 and 96% sensitivity in relation to gentamicin, streptomycin and kanamycin, respectively, and a specificity of 100% for all three aminoglycosides. Statistical significance (P < 0.01 to P < 0.001) was demonstrated in (1) a greater incidence of enterococci with high-level resistance to aminoglycosides among blood isolates; (2) gentamicin resistance predicting kanamycin high-level resistance; and (3) more resistance to gentamicin, streptomycin and kanamycin among Enterococcus faecium isolates compared to those of Enterococcus faecalis. Beta-lactamase activity was not detected.

Candidal renal papillary necrosis: report of a case and review.

Renal papillary necrosis (RPN) due to Candida is a rare disease with only 19 cases reported over the past 37 years. But the diagnosis in 17 of the 19 cases was not made until a necropsy was carried out. The 2 cases that were diagnosed antemortem had radiographic sonography. A singapore case with candidal RPN was described in detail. Candidal RPN was associated with underlying diseases in all these cases. The disease may be more frequently encountered in the future with the advent of radiographic tools like sonography which was not described prior to 1980. Indeed, patients with underlying diseases who develop persistent candiduria should have radiographic investigation of the urinary tract to detect candidal RPN to that early remedial measures can be carried out.

Five cases of high-level aminoglycoside resistant enterococcal septicaemia in Singapore.

Five clinical cases of enterococcal septicaemia were studied retrospectively including determination of high-level aminoglycoside resistance (HLAR) to gentamicin, streptomycin and kanamycin. This is the first study of its kind in Singapore. The clinical features and risk factors for this illness were analysed and found to be very similar to enterococcal bacteremia in general. It is important to carry out tests to detect HLAR so that unnecessary aminoglycoside toxicity can be prevented or to decide on the appropriate aminoglycoside to combine with a cell wall-active agent in severe enterococcal sepsis.

Vancomycin-resistant enterococci.

Vancomycin-resistant enterococci (VRE) are gaining much attention in the West, chiefly because of the lack of available antimicrobial therapy for VRE infections as most VRE are also resistant to drugs previously used to treat such diseases (e.g. aminoglycosides and ampicillin), the possibility that the vancomycin-resistant genes present in VRE can be transferred to methicillin-resistant Staphylococcus aureus (MRSA), and increasing reports of VRE and the trend towards endemicity in North America. There are three case reports and a study showing stool carriage of more than 10% from Singapore. One of the case reports is notable as the VRE isolated from the urinary tract is community-acquired. In Europe, there is a strong association between the use of avoparcin (a glycopeptide) in animal feeds and the emergence of VRE. Clonal dissemination resulting in nosocomial transmission is also demonstrated. Prior vancomycin use is a risk factor for the subsequent development of VRE bacteraemia. The laboratory plays an important role, namely, a) detection of VRE, and b) determination of susceptibilities of antimicrobials whereby possible therapeutic options may be instituted when antimicrobial intervention is indicated. There is a need to evaluate existing infection control measures against VRE to prevent it from becoming endemic in Singapore as had happened in North America.

Clinical observations on nail changes in psoriasis.

410 cases of psoriasis [282 males (68%) and 127 females (31%)] were interviewed and examined to study the nail changes. The prevalence of nail changes was 78.0% (males = females). Common changes were pitting (67.5%) and onycholysis (67.2%). Dystrophy of varying degrees occurred in 35.0%, subungual hyperkeratosis in 24.7%, discoloration in 18.4%, loss of nails in 2.8% and pustulation in 1.3%. Pitting and onycholysis was the most common combination (45.6%). Nail changes were significantly more common in patients who have moderate to severe psoriasis as compared with patients with mild psoriasis; in patients who have psoriasis for greater than 5 years as compared with patients who have psoriasis for less than 5 years; and in patients older than age 50 as compared with those aged less than 50. A definite correlation was found between the prevalence of nail changes and the presence of scalp and periungual psoriasis, and the presence of joint involvement.

Susceptibility of Haemophilus influenzae isolates with known resistance mechanisms to five cephalosporins.

The in vitro activities of cefaclor, cefetamet, cefixime, cefotaxime and cefuroxime were determined against 150 isolates of Haemophilus influenzae. These included 50 ampicillin-susceptible, 50 beta-lactamase-producing and 50 intrinsically ampicillin-resistant isolates. A closer relationship was apparent between the intrinsic resistance to ampicillin and reduced susceptibility to cephalosporins. Both MIC and disc diffusion methods showed that the activities of cephalosporins were reduced against most, though not all, isolates with intrinsic resistance to ampicillin. All intrinsically ampicillin-resistant isolates should be considered resistant to all cephalosporins at the present time since the clinical significance of the reduction in susceptibility is uncertain. Amongst the five cephalosporins tested, cefaclor susceptibility may facilitate the detection of intrinsic ampicillin resistance since it predicts isolates with this type of resistance mechanism.

Can susceptibility to an antimicrobial be restored by halting its use? The case of streptomycin versus Enterobacteriaceae.

To test the widespread view that resistance disappears in the absence of antimicrobial use, we tested streptomycin against 477 Enterobacteriaceae from the Royal London Hospital. Twenty per cent proved resistant although streptomycin is little used at the hospital and streptomycin resistance in gram-negative bacteria is caused by mechanisms that do not compromise the drugs that are used. Up to 70% of the observed resistance was associated with cross-resistance to spectinomycin and the presence of ant(3")-Ia, an integron-associated gene carried in Tn21-type transposons. This genetic organization may have conserved streptomycin resistance in the absence of direct selection pressure.