Detection of decreased susceptibility to fluoroquinolones in Salmonella spp. by five different methods including real-time polymerase chain reaction (PCR)

Detection of Salmonella spp. isolates showing decreased susceptibility to fluoroquinolones has become important owing to the increasing prevalence of these strains and their association with treatment failure. Nalidixic acid agar dilution, nalidixic acid disk diffusion, MicroScan automated system and real-time polymerase chain reaction (PCR) (LightCycler) followed by melting temperature (Tm) analysis are compared with ciprofloxacin agar dilution as suitable methods to detect decreased susceptibility to fluoroquinolones in 100 Salmonella spp. isolates. Three minor discrepancies were found for nalidixic acid disk diffusion, one minor discrepancy was found for nalidixic acid agar dilution and Tm analysis, and one major discrepancy was found for MicroScan. Nalidixic acid disk diffusion was confirmed as a good screening method. Tm analysis is a rapid and accurate method for detecting decreased susceptibility to fluoroquinolones due to gyrA mutations in Salmonella spp.

[Nontuberculous mycobacteria in patients with cystic fibrosis]

OBJECTIVE

Patients with cystic fibrosis are at great risk of infection by nontuberculous mycobacteria from the environment because of certain predisposing factors such as bronchiectasis, malnutrition, and diabetes. The aim of this study was to analyze the mycobacterial content of sputum smears and cultures from adult patients with cystic fibrosis attended at a specialized unit for adults from March 1997 through December 2001.

PATIENTS AND METHODS

Sputum samples were collected prospectively according to a protocol applied at each visit, and during most exacerbations staining and culture for mycobacteria were ordered in addition to the usual cultures for bacteria and fungi. A tuberculin test was performed at the end of the study.

RESULTS

Twenty-eight patients (16 men) with cystic fibrosis were enrolled. The mean (SD) age was 25.3 (6.7) years. A total of 251 samples were cultured (range in number of samples per patient, 1-31). The mean period of follow up was 40.3 (22.1) months. The sputum smear was positive in 29 cases (4 patients); the culture was positive in 7 patients. More than 3 samples were positive in only 4 patients. Mycobacterium abscessus was isolated in 3 cases, Mycobacterium avium complex in 2 and Mycobacterium simiae in 1 and other an unidentified rapid growth Mycobacterium species. The Mantoux test was positive in 5 patients. Two of the 4 patients in whose samples mycobacteria were isolated repeatedly required treatment.

CONCLUSIONS

The prevalence of nontuberculous mycobacterial infection is high in patients with cystic fibrosis. Staining and culture for mycobacteria should be carried out regularly and whenever exacerbation of pulmonary symptoms cannot be attributed to bacteria usually found in such patients. Patients with recurrent isolations of mycobacteria should be monitored closely.

Community-acquired urinary tract infection caused by vancomycin-resistant Enterococcus faecalis clinical isolate

We present a case of urinary tract infection caused by vancomycin-resistant Enterococcus faecalis. The patient is a 62-year-old woman showing no recent admittances. The isolated microorganism was identified by MicroScan (DADE) and API (BioMerieux) and susceptibility was assessed by disk diffusion, E-test and broth microdilution. The isolate was identified as Enterococcus faecalis and showed high MIC for vancomycin (>128 mg/l) and teicoplanin (8 mg/l) but was susceptible to ampicillin. The transmission routes of vancomycin-resistant enterococci in the community and their clinical implications remain uncertain. Healthy carriers have already been described in several countries but this case report represents an unusual finding.

Enzymatic cycling assay for D-carnitine determination

An enzymatic method for d-carnitine determination using the enzyme d-carnitine dehydrogenase is described. The assay is based on the amplified signal produced during NAD(+) cycling in the presence of a tetrazolium salt and using phenazine methosulfate as electron carrier. Optimum assay conditions were studied with two tetrazolium salt pairs: 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT)/MTT-formazan and 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl tetrazolium chloride (INT)/INT-formazan. The first pair (MTT) showed higher sensitivity. The calibration curve was linear from 0.1 to 5 mM d-carnitine, with a quantification limit of 0.1 mM and a relative standard deviation of 1.51%. The procedure is simple, rapid, accurate, and easily automated. It was satisfactorily applied to following d-carnitine levels during the microbial transformation of d-carnitine into l-carnitine and to determining the d-carnitine content of pharmaceutical preparations.

Penicillium brevicompactum as the cause of a necrotic lung ball in an allogeneic bone marrow transplant recipient

The non-Candida, non-Aspergillus fungal infections are being reported with increasing frequency in BMT patients. One of these agents is Penicillium which has rarely been implicated as a pathogen in these patients. Only a few cases of isolated fungemias have been reported to date. We present the first documented case of invasive lung infection due to Penicillium brevicompactum in an allogeneic BMT recipient. As this case shows, the diagnosis of non-Candida, non-Aspergillus fungal infections may be incorrect if only histologic findings are available, mainly because misdiagnosis with other more common fungus can occur. A positive culture is required in order to make an accurate diagnosis.

[Transient bacteremia caused by Corynebacterium urealyticum: apropos of 2 cases]

BACKGROUND

Corynebacterium urealyticum is a pathogen mainly isolated from the urinary tract and seldom from the blood. We present two cases of bacteremia caused by multiresistant C. urealyticum isolated in two and three blood cultures respectively.

PATIENTS AND METHODS

The two cases were studied. C. urealyticum was isolated from blood cultures and clinical charts were reviewed retrospectively. No history of prior antibiotic therapy was observed in either patient. Blood cultures were processed using BACTEC NC 730 system (Becton Dickinson). The API Coryne system (BioMérieux) was used to identify both strains.

RESULTS

Despite both patients having not received any antibiotic treatment, they improved clinically and microbiologically. Therefore, the episodes were considered as transitory bacteremias.

CONCLUSION

Although C. urealyticum is not common, we believe that it is necessary to identify any diphtheromorphic microorganism in blood, when they are clinically significant.

[Corynebacterium jeikeium septicemia]

An adult male with non-Hodgkin lymphoma, who had been admitted to the hospital for more than one month and had received previous antibiotic therapy, developed Corynebacterium jeikeium septicemia. The organism was isolated in four blood cultures and it was multirresistant, being only sensitive to vancomycin, ciprofloxacin, norfloxacin and rifampin. The patient improved clinically and was bacteriologically cured with intravenous vancomycin therapy.