Francisco Soriano

Antimicrobial susceptibilities of Corynebacterium species and other non-spore-forming gram-positive bacilli to 18 antimicrobial agents.

The susceptibilities of 265 strains of Corynebacterium species and other non-spore-forming gram-positive bacilli to 18 antimicrobial agents were tested. Most strains were susceptible to vancomycin, doxycycline, and fusidic acid. Corynebacterium jeikeium and Corynebacterium urealyticum were the most resistant organisms tested. Resistance to beta-lactams, clindamycin, erythromycin, azythromycin, ciprofloxacin and gentamicin was common among strains of Corynebacterium xerosis and Corynebacterium minutissimum. Ampicillin resistance among Listeria monocytogenes was more prevalent than previously reported. Optochin, fosfomycin, and nitrofurantoin showed very little activity against most organisms tested, but the use of nitrofurantoin as a selective agent in culture medium may prevent the recovery of some isolates. Except for the unvarying activity of vancomycin against Corynebacterium species, the antimicrobial susceptibilities of the latter to other antibiotics are usually unpredictable, such that susceptibility tests are necessary for selecting the best antimicrobial treatment.

Activity of nine antimicrobial agents against Corynebacterium group D2 strains isolated from clinical specimens and skin.

The in vitro activities of nine antimicrobial agents against Corynebacterium group D2 strains isolated from clinical specimens and from healthy skin of hospitalized patients were studied. Ciprofloxacin, ofloxacin, norfloxacin, vancomycin, and teicoplanin were very active against these microorganisms. There were no significant differences in susceptibility between clinical and colonizing isolates.

Antimicrobial susceptibility of Corynebacterium group D2

The in vitro susceptibility of 30 Corynebacterium group D2 strains to nine antimicrobial agents was determined. Vancomycin and norfloxacin were the most active agents tested. All strains were resistant to ampicillin and cephalothin, all except one were resistant to gentamicin, and the activity of erythromycin, novobiocin, tetracycline, and rifampin varied.

Isolation of Propionibacterium acnes from central nervous system infections.

Propionibacterium acnes is a common skin colonizer and its involvement in central nervous system (CNS) infections may be related with previous neurosurgical procedures. P. acnes was isolated in pure or mixed cultures from ten patients with CNS infections during a 5-year period. The clinical presentation, treatment and outcome were retrospectively reviewed. Nine out of 11 patients had CNS infections after a neurosurgical procedure. The clinical presentation was: brain abscess (five patients), subdural or epidural empyema (four patients) and shunt meningitis (one patient). Three patients had also secondary meningitis. All patients received antibiotic therapy and all abscesses and empyemas were drained. The patient with shunt meningitis cured without catheter removal. Only one patient with a brain abscess by P. acnes died, but several months thereafter and as a consequence of a Gram-negative superinfection. P. acnes is a pathogen for the CNS and infections must be surgically managed under adequate antibiotic treatment.

Q Fever Endocarditis on Porcine Bioprosthetic Valves: Clinicopathologic Features and Microbiologic Findings in Three Patients Treated with Doxycycline, Cotrimoxazole, and Valve Replacement

Three patients developed Q fever endocarditis on porcine bioprosthetic valves. They had a subacute or chronic course with nonspecific symptoms, enlargement of the liver and spleen, and cardiac failure due to destruction of the cusps, without disruption of the valve ring. High-phase I-specific IgG and IgA antibody titers against Coxiella burnetii were found. C. burnetii was isolated in each patient by inoculating suspensions of valve tissue into a human fetal diploid fibroblast cell line, which was grown as monolayers on slides contained inside rubber-stoppered tube cultures. Patients were treated successfully with doxycycline, cotrimoxazole, and valve replacement and were followed up for periods of 24 to 42 months; no evidence of deterioration was found. The human fetal diploid cell culture may be an expeditious, easy, and safe method to isolate C. burnetii from cardiac valves. Valve replacement seemed necessary to cure prosthetic-valve endocarditis due to C. burnetii infection. Combined therapy with doxycycline and cotrimoxazole may control the disease and prevent reinfection of the homografts replacing the valves.

Isolation of Nocardia sp. from Blood Cultures in a Teaching Hospital

To determine the clinical significance of the isolation of Nocardia sp. from blood cultures, clinical records of patients with bacteremia due to Nocardia sp. in our hospital from January 1986 to December 1990 were retrospectively reviewed. Eight patients had 9 blood cultures positive for Nocardia sp. Four of the isolates were identified as Nocardia asteroides. Only 2 of the patients had disseminated nocardiosis due to N. asteroides, and both were appropriately treated for Nocardia sp. In the other cases, isolation of Nocardia sp. was considered nonsignificant or undetermined, and all were clinically cured. Nocardia sp. may be an occasional contaminant of blood cultures. The significance of nocardemia is a matter of clinical judgment.

Pulmonary infection by Mycobacterium gordonae in an immunocompromised patient

Mycobacterium gordonae, a scotochromogenic organism, is considered a saprophyte and isolation of this organism in sputum cultures is not generally considered clinically significant. We report the case of 70-yr-old man with Hodgkins disease and pulmonary infection caused by Mycobacterium gordonae. The clinical and radiographic findings in this case and the course are outlined. Mycobacterium gordonae isolated from patients with debilitating diseases should not automatically be rejected as a contaminant.

Treatment of encrusted cystitis caused by Corynebacterium group D2 with norfloxacin, ciprofloxacin, and teicoplanin in an experimental model in rats.

Oral doses of norfloxacin (80 mg/kg of body weight per day) and ciprofloxacin (25 and 80 mg/kg/day) and intramuscular doses of teicoplanin (5 mg/kg/day), all administered once a day for 10 days, were evaluated as a means of preventing encrusted cystitis caused by Corynebacterium group D2. Zinc disks dipped into a 24-h broth culture of these microorganisms were inserted into the bladders of female Wistar rats, and treatment was started 14 days after bacterial challenge. The appearance of encrusted cystitis was directly related to a documented urinary tract infection by these coryneforms (71.7 and 0% for rats with positive and negative urine cultures, respectively). All rats that died between days 18 to 43 after bacterial challenge presented very severe encrusted cystitis, which was prevented by teicoplanin and high doses of ciprofloxacin. Rats surviving up to day 44 after bacterial challenge were sacrificed; they presented a lower incidence of encrusted cystitis which was also less severe, with teicoplanin and a high dose of ciprofloxacin being more active in reducing the rate of positive cultures (78.8 and 65.7% reduction, respectively). All antibiotics and doses used were active in vivo at preventing encrusted cystitis by Corynebacterium group D2, but the best therapeutic effect was obtained with teicoplanin.

Biochemical, antimicrobial susceptibility and genotyping studies on Corynebacterium urealyticum isolates from diverse sources.

Thirty-two isolates of Corynebacterium urealyticum, isolated between 1991 and 1995, were studied by biochemical tests, phospholipid content, analysis of fatty and mycolic acids, ribotyping, whole-cell protein patterns and antimicrobial susceptibility to six antibiotics. Nineteen isolates were from human and human-related sources (HHRS); the remainder were from animal and animal-related sources (AARS). Most C. urealyticum isolates were similar in their biochemical and whole-cell protein profiles, although most HHRS isolates were alkaline phosphatase-positive (84%) and produced almost identical protein patterns, whereas AARS isolates were quite diverse. The qualitative composition of cellular fatty acids was identical for all isolates examined. Twelve different ribotypes were obtained with HindIII producing four-to-seven bands. Ribotypes 8, 9 and 10 were predominant in isolates from HHRS, whereas in isolates from AARS, ribotypes 5 and 6 predominated. AARS isolates were significantly less antibiotic-resistant, in comparison with HHRS isolates. Ribotyping appeared to be the most useful tool for strain characterisation.

Effect of inoculum size on bacteriolytic activity of cefminox and four other beta-lactam antibiotics against Escherichia coli.

MICs and turbidimetric experiments revealed a negligible inoculum effect with two Escherichia coli strains exposed to cefminox and cefoxitin, whereas a marked inoculum effect was revealed after exposure to cefotaxime, ceftizoxime, and imipenem. The activities of the cephamycins were associated with spheroplast formation and bacteriolysis at concentrations close to the MIC, whereas the other agents induced the formation of filaments or, in the case of imipenem, rounded cells.