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Biomedical subjects

K G Kerr

Publications and source records attributed to K G Kerr.

At least 37 records · Page 2Linked to original sources
PubMed2000

Detection of extended-spectrum beta-lactamases in members of the family enterobacteriaceae: comparison of the MAST DD test, the double disc and the Etest ESBL.

A technically simple method-the MAST double disc (MDD) test-for the detection of extended-spectrum beta-lactamase (ESBL) production by bacteria is described. A wide range of ESBL, non-ESBL and Class 1 beta-lactamase-producing isolates was examined. The MDD test, which uses discs containing ceftazidime and a complementary disc containing ceftazidime and clavulanate and a second pair containing cefotaxime and cefotaxime and clavulanate was compared with the standard double disc diffusion test and an Etest method. Both the Etest and the MDD correctly identified 93% of ESBL producers. The MDD is an inexpensive alternative to current methods for the detection of ESBL production.

Anti-Bacterial Agents↗
PubMed1999

Activity of quinolones against viridans group streptococci isolated from blood cultures of patients with haematological malignancy.

Use of fluoroquinolones for antimicrobial prophylaxis during neutropenia is often cited as a significant predisposing factor for viridans group streptococcus (VGS) bacteraemia. Newer compounds in this class are reputed to have enhanced activity against Gram-positive bacteria, and we determined the minimal inhibitory concentrations (MICs) for ciprofloxacin and three of the newer compounds: trovafloxacin, fleroxacin and clinafloxacin, against 44 isolates of VGS. On a gravimetric basis, clinafloxacin was most active (MIC90 0.19 mg/l), whereas ciprofloxacin and fleroxacin were the least active (both MIC90 16 mg/l). Clinafloxacin warrants further study as an agent of prophylaxis against bacterial infection in neutropenic patients.

Adult↗
PubMed1999

Microbiological safety of essential oils used in complementary therapies and the activity of these compounds against bacterial and fungal pathogens.

To determine the safety of plant essential oils we determined the sterility of eight of these products obtained from retail outlets. In addition, the ability of oils to support the growth of fungal and bacterial pathogens was examined. The antimicrobial activity of these products against seven bacterial species and Candida albicans was also investigated. All oils and their respective carriers were sterile. Methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa were unable to survive in oils for longer than 6 h, whereas C. albicans was able to survive, but not multiply, in ylang ylang oil for at least 48 h.

Bacteria↗
PubMed1999

Staphylococcus capitis endocarditis: two cases and review of the literature.

Coagulase negative staphylococci are the principal cause of prosthetic valve endocarditis but are a rare cause of native valve infections. However, the incidence of native valve endocarditis is increasing. Staphylococcus capitis is a coagulase negative staphylococcus with the capacity to cause endocarditis on native heart valves. Two cases of native valve endocarditis caused by S capitis are presented; both in patients with aortic valve disease. The patients were cured with prolonged intravenous vancomycin and rifampicin and did not need surgery during the acute phase of the illness. Five of the six previously described cases of endocarditis caused by this organism occurred on native valves and responded to medical treatment alone.

Adult↗
PubMed1998

Bottled water as a source of multi-resistant Stenotrophomonas and Pseudomonas species for neutropenic patients.

Stenotrophomonas maltophilia is an emerging nosocomial pathogen in patients rendered neutropenic following cytoreductive therapy for malignancy. The identification of sources and routes of transmission of this bacterium is of importance in the development of strategies to prevent nosocomial acquisition of S. maltophilia. A previous study had shown high rates of faecal carriage of S. maltophilia amongst patients with haematological malignancy and, as bottled water was consumed by many patients, we determined the prevalence of S. maltophilia in both carbonated and non-carbonated commercially available bottled water. Whereas carbonated water did not yield bacterial growth, 22 samples of non-carbonated products had total viable bacterial counts (at 22 degrees C) ranging between 0 and 4.9 x 10(4)/mL. Three samples yielded S. maltophilia and a further eight grew Pseudomonas species. Isolates of S. maltophilia of both clinical and environmental origin were able to survive, or grow, in non-carbonated mineral water over a range of pH and temperature values, including refrigeration temperatures. We therefore recommend that neutropenic patients should not consume non-carbonated bottled mineral water.

Antineoplastic Agents↗
PubMed1998

Microbiological and clinical aspects of infection associated with Stenotrophomonas maltophilia.

The gram-negative bacterium Stenotrophomonas maltophilia is increasingly recognized as an important cause of nosocomial infection. Infection occurs principally, but not exclusively, in debilitated and immunosuppressed individuals. Management of S. maltophilia-associated infection is problematic because many strains of the bacterium manifest resistance to multiple antibiotics. These difficulties are compounded by methodological problems in in vitro susceptibility testing for which there are, as yet, no formal guidelines. Despite its acknowledged importance as a nosocomial pathogen, little is known of the epidemiology of S. maltophilia, and although it is considered an environmental bacterium, its sources and reservoirs are often not readily apparent. Molecular typing systems may contribute to our knowledge of the epidemiology of S. maltophilia infection, thus allowing the development of strategies to interrupt the transmission of the bacterium in the hospital setting. Even less is known of pathogenic mechanisms and putative virulence factors involved in the natural history of S. maltophilia infection and this, coupled with difficulties in distinguishing colonization from true infection, has fostered the view that the bacterium is essentially nonpathogenic. This article aims to review the current taxonomic status of S. maltophilia, and it discusses the laboratory identification of the bacterium. The epidemiology of the organism is considered with particular reference to nosocomial outbreaks, several of which have been investigated by molecular typing techniques. Risk factors for acquisition of the bacterium are also reviewed, and the ever-expanding spectrum of clinical syndromes associated with S. maltophilia is surveyed. Antimicrobial resistance mechanisms, pitfalls in in vitro susceptibility testing, and therapy of S. maltophilia infections are also discussed.

Anti-Bacterial Agents↗
PubMed1998

Molecular epidemiology of Stenotrophomonas maltophilia isolated from clinical specimens from patients with cystic fibrosis and associated environmental samples.

Stenotrophomonas maltophilia was isolated from the respiratory tracts of 41 (25%) of 163 children attending our pediatric cystic fibrosis unit between September 1993 and December 1995. The extents of S. maltophilia contamination of environmental sites frequented by these patients were investigated with a selective medium incorporating vancomycin, imipenem, and amphotericin B. Eighty-two isolates of S. maltophilia were cultured from 67 different environmental sites sampled between January and July 1996. The organism was widespread in the home environment, with 20 (36%) and 25 (42%) of sampled sites positive in the homes of colonized and noncolonized patients, respectively. In the nosocomial setting, it was isolated from 18 (32%) sites in the hospital ward and from 4 (17%) sites in the outpatient clinic area. The most common sites of contamination were sink drains, faucets, and other items frequently in contact with water. All environmental and clinical isolates were genotyped with enterobacterial repetitive intergenic consensus sequences as primers. A total of 33 of the 41 patients were colonized with unique strains, and four pairs of patients shared strains. Further characterization by pulsed-field gel electrophoresis after digestion with XbaI found that there was no evidence of patient-to-patient transmission; however, there was some evidence that a small number of patients may have acquired the organism from the hospital environment. Resampling of environmental sites in the hospital ward in January 1997 revealed evidence of genetic drift, complicating the accurate determination of environmental sources for clinical strains. The source of the majority of S. maltophilia strains colonizing the respiratory tracts of these patients with cystic fibrosis remained uncertain but may have represented multiple, independent acquisitions from a variety of environmental sites both within and outside the hospital.

Adolescent↗
PubMed1996

A new selective differential medium for isolation of Stenotrophomonas maltophilia.

A new selective differential medium for the isolation of Stenotrophomonas (formerly Xanthomonas) maltophilia was developed. The medium, VIA agar, contained vancomycin, imipenem, and amphotericin B as selective agents and incorporated a mannitol/bromothymol blue indicator system. Compared with Xanthomonas maltophilia Selective Medium (XMSM), VIA agar was less inhibitory to Stenotrophomonas maltophilia and was more selective than XMSM in preventing the growth of unwanted bacteria from contaminated specimens. Although vancomycin-resistant strains of Enterococcus faecium may grow on VIA agar, these can be easily distinguished from Stenotrophomonas maltophilia because of mannitol fermentation.

Amphotericin B↗
PubMed1993

Effect of divalent cations in bacteriological media on the susceptibility of Xanthomonas maltophilia to imipenem, with special reference to zinc ions.

The susceptibility of Xanthomonas maltophilia strains to beta-lactams is known to vary according to the type of growth media used. We have assayed the divalent cation content of various susceptibility testing media and correlated this with the susceptibility to imipenem of 30 strains of X. maltophilia, by calculating the IC50. No correlation was found with Ca++ and Mg++ content (r = 0.005, P = 0.99), but a highly significant correlation with the Zn++ content (7.7-42.7 mumol/L) of the medium was found (r = 0.93, P = 0.003). The effect of Zn++ on the susceptibility of X. maltophilia to imipenem was further investigated by adding varying amounts of zinc sulphate to Oxoid Mueller-Hinton agar which has a low Zn++ content (14.2 mumol/L). A highly significant correlation between the Zn++ content and the IC50 was observed (r = 0.95, P = 0.001). Some variability was seen from one series of IC50 determinations to another and samples of ultra-pure water were processed in exactly the same fashion as the agar media and then assayed for cation content. No significant increase in Ca++ or Mg++ content of the water were observed but water autoclaved in universal containers with metal caps and rubber washers acquired up to 40 mumol/L of Zn++. Studies of the correlation between in-vitro sensitivity tests and the clinical performance of beta-lactams used against X. maltophilia will need to take account of the Zn++ content of the susceptibility testing media used.

Anti-Bacterial Agents↗
PubMed1993

Evaluation of the API Coryne system for identification of Listeria species.

The API Coryne system, a commercially available system for the identification of coryneform bacteria, was used to identify 103 strains of Listeria spp. from clinical and environmental sources. All isolates were identified correctly to the genus or species level, although complete characterization also required tests for beta-hemolysis and CAMP reaction.

Listeria↗
PubMed1991

Evaluation of the Rosco system for the identification of Listeria species.

The Rosco system was used to identify previously confirmed isolates of the seven currently recognised species of Listeria. These included reference cultures and recent isolates from clinical material, food products and environmental sources. The system identified all correctly. Results were obtained after 4 h if heavy inocula, as suggested by the manufacturers, were used. The method may be used to aid identification of isolates of Listeria from clinical and non-clinical specimens and would be of particular value in laboratories examining small numbers of isolates relatively infrequently. Essential tests not included in the system are beta-haemolysis on sheep-blood agar and the CAMP test.

Listeria↗