[Mycobacterium simiae infections: about two cases]

We report two cases of Mycobacterium simiae infections differing by the site of infection, the immunological status of the patients and the diagnostic methods used. The first case is a disseminated infection in an advanced immunosuppressed patient who died quickly confirming the severity of this infection in the context of HIV infection. The second case presented is a respiratory disease in a women with a past history of tuberculosis and an uneventful evolution of the M. simiae infection under treatment. These two cases demontrate the importance of molecular methods to correctly identify M. simiae.

Risk factors for multidrug-resistant Pseudomonas aeruginosa nosocomial infection

A case-control study was conducted in a university hospital to determine the risk factors for nosocomial infection with multidrug-resistant Pseudomonas aeruginosa (MDR-PA) among all hospitalized patients and among those with a nosocomial infection due to P. aeruginosa. Eighty patients infected with MDR-PA, 75 infected with a non-MDR phenotype and 240 random controls were included in the 12-month study. Among all hospitalized patients, age, severity index, having a bedridden condition, transfer from other units, nasogastric feeding, urinary catheterization and exposure to beta-lactams (OR=2.5) or fluoroquinolones (OR=4.1) in the seven days before infection were linked to nosocomial infection due to MDR-PA. Among patients infected by P. aeruginosa, exposure to fluoroquinolones (OR=4.7) or surgery (OR=0.5) were linked to the isolation of MDR-PA. This study showed that, in addition to urinary catheterization, nasogastric feeding is an important risk factor in MDR-PA infection. Indeed, an imbalance in gut flora, modifications to the mucous membranes due to the use of nasogastric feeding and the selection pressures exerted by antibiotics were implicated in the occurrence of this infection.

Risk factors for antibiotic-resistant Escherichia coli isolated from hospitalized patients with urinary tract infections: a prospective study

From November 1998 to February 1999 we prospectively evaluated the prevalence of resistance to penicillins, cephalosporins, carbapenem, quinolones, aminoglycosides, and trimethoprim-sulfamethoxazole (SXT) in 320 Escherichia coli isolates isolated from hospitalized patients with acute urinary tract infections (UTIs). We also studied for these strains risk factors for resistance to amoxicillin-clavulanic acid (AMC), fluoroquinolones (FQs), and SXT. Resistance rates were consistent with those from major recent studies reported in the literature. Multivariate analyses selected the following factors as being significantly associated with E. coli resistance: (i) for resistance to AMC, prior (1 year) UTI (odds ratio [OR] = 2.71, P = 0.006), prior (1 year) urinary catheter (OR = 2.98, P = 0.0025), and prior (6 months) antibiotic exposure (OR = 2.68, P = 0.005); (ii) for resistance to FQs male sex (OR = 3.87, P = 0.03), with a trend toward significance for age >65 years (OR = 7.67, P = 0.06) and prior (1 year) UTI (OR = 2.98, P = 0.07); and (iii) for resistance to SXT, male sex (OR = 1.91, P = 0.046), hospitalization in an intermediate-term-care unit (OR = 2.18, P = 0.008), and prior (1 year) UTI (OR = 2.03, P = 0.03). Ours results suggest that prior UTI is a common risk factor for resistance to the different antibiotics tested. Although few studies on risk factors for E. coli resistance to antibiotics have been published, careful interpretation of their findings, taking into consideration the population, infection site, and period studied, should contribute to the formulation of a better strategy that can be used to overcome antibiotic resistance.

A population approach to the forecasting of amikacin plasma and urinary levels using a prescribed dosage regimen

We retrospectively analyzed amikacin pharmacokinetics in 19 critically ill patients who received amikacin intravenously. Fourteen subjects (577 serum amikacin concentrations, 167 urine measurements) were studied to obtain data for population modeling, while 5 patients (267 serum amikacin concentrations, 68 urine measurements) were studied for the assessment of predictive performance. The population analysis was performed using serum and urine amikacin measurements; the renal clearance of amikacin was expressed as a function of creatinine clearance. A two-compartment model was fitted to the population data by using NONMEM. The population characteristics of the pharmacokinetic parameters (fixed and random effects) were estimated using the FOCE method. The population pharmacokinetic parameters with the interindividual variability (CV%) were as follows: slope (0.254, 126%) and intercept (3 l/h, 59.6%) of the linear model which relate the amikacin renal clearance to the creatinine clearance, initial volume of distribution (17.1 l, 22.2%), intercompartment clearance (5.22 l/h, 104%), steady state volume of distribution (55.2 l, 64.1%) and urinary elimination (67.5%, 36.3%). The Bayesian approach developed in this study accurately predicts amikacin concentrations in serum and urine and allows for the estimation of amikacin pharmacokinetic parameters, minimizing the risk of bias in the prediction.

Population pharmacokinetics of amikacin in critically ill patients

The pharmacokinetic parameters of amikacin were determined in a population of 20 adults and 36 pediatric patients admitted into an intensive care unit. Amikacin was administered by repeated intravenous infusion over 0.5 h (600 to 1,350 mg for adults; 70 to 1,500 mg for children). The number of administrations ranged from 2 to 17, and the number of samples collected from each patient ranged from 2 to 70. The population enrolled in the study had large variabilities in age (0.5 to 85 years), weight (6 to 95 kg), height (72 to 187 cm), creatinine clearance rate (18 to 110 ml/min), blood urea nitrogen concentration (1.5 to 15 mmol/liter), and total protein concentration (30 to 91 g/liter). The mean population parameters and their interindividual variabilities were obtained for an initial group of 44 patients (16 adults and 28 children). A two-compartment model was fitted to the population data by using the computer program P-PHARM. Model selection was guided by evaluation of the minimum objective function and the weighted residuals. The population analysis has been performed with the complete set of the collected data, including the individual serum amikacin concentration together with the individual estimate of the creatinine clearance values. The potential sources of variability in the population parameters were investigated by using patients' age, height, weight, creatinine clearance, blood urea nitrogen concentration, and total protein concentration as covariables. A test group of 12 additional patients (4 adults and 8 children) was used to evaluate the predictive performances of the population parameters. The individual pharmacokinetic parameters were computed by a Bayesian fitting procedure. From the resulting individualized values of the parameters, the concentrations of amikacin in the serum of the patients were calculated. To evaluate the performance of the Bayesian estimation, the experimental concentrations were compared with the predicted ones. The Bayesian approached developed in the study accurately predicts amikacin concentrations in serum and allows for the estimation of amikacin pharmacokinetics parameters, minimizing the risk of bias in the prediction. This was demonstrated in patients with both stable and unstable renal functions.

Pefloxacin clinical pharmacokinetics

Pefloxacin has a broad spectrum of activity against a great number of Gram-negative and Gram-positive bacteria. It is also capable of penetration into cells, yielding high tissue:serum ratios, with implications for the treatment of infections caused by intracellular pathogens. Pefloxacin is well absorbed from the gastrointestinal tract. Its elimination half-life ranges from 6.2 to 12.4 hours. After repeated administration, a major change in pharmacokinetic parameters is observed. Pharmacokinetic parameters are minimally altered or not altered in patients with impaired renal function. Altered plasma pharmacokinetics in patients with liver insufficiency and in elderly patients are observed, so dosage adjustments are necessary. In addition, pefloxacin interacts with a number of other compounds at hepatic (e.g. theophylline and cimetidine) and gastrointestinal (e.g. antacids) sites. With the exception of saliva, cerebrospinal fluid, aqueous humor, vitreous fluid and amniotic fluid, body fluid concentrations reach plasma concentrations. Studies on tissue penetration show that concentrations exceeding plasma concentrations are obtained in most tissues. The highest tissue:plasma concentration ratios are achieved in lung and kidney, whereas concentrations in fat are considerably lower than those in plasma.

Epidemiological study by pulsed-field gel electrophoresis of an outbreak of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae in a geriatric hospital

Twelve cases of infections caused by extended-spectrum beta-lactamase (ESBla)-producing Klebsiella pneumoniae were reported between August 1991 and March 1993 in the Geriatric Department of the Nimes University Hospital, where these bacterial had not been previously isolated. Restriction profiles of total genomic DNAs cleaved by XbaI and SpeI were compared by pulsed-field gel electrophoresis. The strains that were tested included the 12 isolates from K. pneumoniae-infected patients, strains recovered from rectal swabs of asymptomatic patients in the same ward, and strains isolated in other hospitals in Nîmes at the same time. The restriction profiles of the 12 isolates and those recovered from asymptomatic patients in the same ward were very similar. Over a period of more than 1 year, extended-spectrum beta-lactamases were not detected in K. pneumoniae isolates with restriction patterns different from that of the epidemic strain. It seems, therefore, that there was no transfer of a plasmid or a gene coding for ESBla to strains of K. pneumoniae that were different from the epidemic strain. At the same time, ESBla-producing K. pneumoniae isolates exhibiting restriction endonuclease profiles very different from that of the epidemic strain were isolated from other hospitals in Nîmes. None of these strains caused an outbreak. Pulsed-field gel electrophoresis, which allows precise characterization of strains beyond the species level, is a useful tool for studying the ESBla-producing K. pneumoniae strains involved in nosocomial outbreaks.

Use of pulsed-field gel electrophoresis for investigation of hospital outbreaks of Acinetobacter baumannii

Genomic DNAs from taxonomically and epidemiologically well-defined strains of Acinetobacter baumannii were digested with restriction endonucleases that cleave with low frequency, and the fragments were separated by pulse-field gel electrophoresis. Restriction fragment length polymorphisms were observed. Restriction fragment length polymorphism analysis can be used as an epidemiological tool to delineate outbreaks of nosocomial infections caused by A. baumannii.

DNA polymorphisms in methicillin-susceptible and methicillin-resistant strains of Staphylococcus aureus

Restriction fragment length polymorphisms in methicillin-susceptible and methicillin-resistant (MRSA) strains of Staphylococcus aureus isolated in the same hospital over a 4-month period were studied by using SmaI and ApaI digestion of genomic DNA and pulsed-field gel electrophoresis. Each of the 20 methicillin-susceptible strains had a unique SmaI pattern, but the 27 MRSA strains showed only seven SmaI patterns. More than half of the SmaI fragments in all of these seven patterns were identical, as were those in the patterns from two unrelated MRSA strains. Digestion with ApaI, which cuts staphylococcus DNA into at least twice as many fragments, confirmed the results obtained with SmaI. Lastly, the plasmid contents of MRSA strains showing identical SmaI and ApaI electrophoretic patterns were not identical. These results are interpreted as supporting the hypothesis that all MRSA strains arose from a single clone and emphasize the need to use several methods in epidemiological investigations of MRSA outbreaks.

Disposition of roxithromycin in the epididymis after repeated oral administration

The epididymal penetration of roxithromycin was studied in order to evaluate the drug for use in the treatment of epididymo-orchitis. Seventeen patients hospitalized for surgery as part of treatment for prostatic adenoma or prostatic cancer were premedicated orally with roxithromycin 150 mg bd for three days followed by 150 mg pre-operatively (3 h before surgical incision). Roxithromycin concentrations in serum and epididymis were determined by microbiological assay. The mean epididymal concentrations were 6.48 +/- 4.88 and 5.98 +/- 3.92 mg/kg for left and right epididymis respectively and the corresponding mean tissue/serum ratios 0.88 +/- 0.57 and 0.84 +/- 0.53. The wide intersubject variation in the concentration of roxithromycin found in serum and tissue is commonly seen with other macrolide antibiotics. The concentrations observed in this study in serum and tissue were greater than the MIC90s for Chlamydia trachomatis (0.25 to 1 mg/L), and Ureaplasma urealyticum (0.5 mg/L).

Altered tobramycin pharmacokinetics during chemoprophylaxis in bladder surgery

The effect of bladder surgery on the pharmacokinetics of tobramycin in hospitalized patients was studied. Fourteen patients with vesical neoplasia undergoing urinary tract surgery were given tobramycin in a dose of 2 mg/kg of body weight. Each patient received the dose at the induction of anesthesia, about 1 h before surgical incision. For seven patients, the drug was also administered 3 weeks later when nutritional conditions were normal. The pharmacokinetic parameters were determined by a two-compartment open model. Except for renal clearance, no significant difference appeared between pharmacokinetic parameters determined from serum data during peri- and postoperative periods. During this work, tobramycin excretion in urine was studied. Twenty-four hours after drug administration, the mean urine tobramycin levels were 25.5 +/- 9.06 and 41.6 +/- 21.5 micrograms/ml after peri- and postoperative administration, respectively; these values were higher than the MICs for most urinary tract pathogens. Seventy-two hours after perioperative administration, the mean value was still elevated (3.54 micrograms/ml), but 72 h after postoperative administration, the urinary tobramycin concentration was not detectable. The percentages of tobramycin recovered unchanged in urine were 54 and 79% after peri- and postoperative administration, respectively. When tobramycin was administered during surgery, a long terminal log-linear phase, with a mean half-life of 25.6 h, was detected. The ratio of renal clearance to total body clearance was 0.52 and 0.79 after peri- and postoperative administration, respectively.

Use of low-frequency-cleavage restriction endonucleases for DNA analysis in epidemiological investigations of nosocomial bacterial infections

Epidemiological investigations of bacterial infections are generally based on multiple phenotypic markers that are often difficult to verify. A more general and reliable method is genomic DNA analysis by restriction endonucleases. However, the commonly used endonucleases produce too many fragments for correct separation by agarose electrophoresis. In contrast, simple electrophoretic patterns are obtained after genomic DNA digestion by low-frequency-cleavage restriction endonucleases and pulsed-field gel electrophoresis, making it easier to compare numerous strains from the same species. This technique was used to investigate an Acinetobacter calcoaceticus outbreak in a urologic department and bronchial colonization of artificially ventilated patients by Pseudomonas aeruginosa in an intensive care unit. The method allowed a clear distinction between epidemic and self-contaminating strains in these different epidemiological situations.

Two cases of Mycobacterium haemophilum infection in a renal-dialysis unit

Two cases of Mycobacterium haemophilum infection in renal-transplant patients occurred in the same hospital department. This raised the possibility that infection may have been acquired in hospital.

[Comparison of the efficacy of cefotaxime alone and the combination cefazolin-tobramycin in the treatment of enterobacterial septicemia]

In a prospective, randomized study we compared cefotaxime (C) with tobramycin plus cefazolin (C + T) in the treatment of Enterobacterial septicemia. Twenty-five patients received C and twenty two C + T. There are 8 treatment failures, in C + T group, 3 in C group. We observed 5 adverse effects, 2 in the C group (1 reversible collapse and 1 Pseudomonas aeruginosa superinfection) and 3 in the C + T group (acute renal failures). We conclude that C may be more effective and less toxic than cefazolin plus tobramycin for patients with Enterobacterial septicemia.

Previously undescribed 6.6-kilobase R plasmid in penicillinase-producing Neisseria gonorrhoeae

A penicillin-resistant Neisseria gonorrhoeae strain was isolated. The resistance was due to the production of TEM-1 beta-lactamase encoded by a plasmid. This 6.6-kilobase plasmid was compared with the previously known 7.4- and 5.3-kilobase penicillin R plasmids of N. gonorrhoeae.

Mycobacterium haemophilum and mycobacterium xenopi associated infection in a renal transplant patient

The case is presented of a renal-transplant patient in Europe with a Mycobacterium haemophilum infection in association with M. xenopi infection. Clinical signs suggested the diagnosis of mycobacteriosis, which was confirmed by a skin biopsy. Despite antitubercular treatment which rapidly eliminated M. xenopi, the patient's condition did not improve until M. haemophilum was identified. Minimal inhibitory concentrations of various antimicrobial compounds showed a lack of efficacy of isoniazid, and rifampin had no clinical effect. The patient recovered only after careful surgical drainage of the lesions and the administration of minocycline. The pathogenesis of such mycobacterioses is discussed, with focus on the immunodepressive status which in our patient may have been partially induced by a cytomegalovirus reinfection.

In vitro immunosuppressive activity of gram-positive (Streptococcus pyogenes) peptidoglycan on mouse lymphocytes

A peptidoglycan fraction prepared from group-A streptococcus was assayed for in vitro mitogenicity on mouse lymphocytes. This fraction reduced considerably the uptake of radioactive thymidine both on unstimulated cell suspensions and on suspensions stimulated by T(PHA)- or B(LPS)-mitogens. The immunosuppression was induced by relatively moderate doses of the fraction, and was dose-dependent. Several experiments ruled out the possibility that these results could be due to a cytotoxicity of the fraction, or to a non-specific interference with the uptake or metabolism of the radioactive precursor. These results are coherent with the observations made in vivo on the mouse and previously published. It is suggested that the mechanism of the immunosuppression could be in relation with the capacity of this fraction to stimulate the reticulo-macrophagic system.

[Liver diseases associated with Yersinia infections (author's transl)]

Yersinia infections are exceptionally responsible for liver damage, the hepatic diseases most commonly encountered being liver abscess consecutive to Y. enterocolitica or Y. pseudo-tuberculosis septicaemia or, more rarely, hepatic granulomata or hepatitis with necrosis and cholestasis. Two new cases are reported. One patient had hepatic granulomata caused by Y. pseudo-tuberculosis and the other, necrotizing hepatitis caused by y. enterocolitica. The course of the disease was favourable in both cases.