High prevalence of closely-related Acinetobacter baumannii in pets according to a multicentre study in veterinary clinics, Reunion Island

Our objective was to study the carriage of Acinetobacter baumannii (AB) in pets in Reunion Island (RI), a French territory in Indian Ocean. Overall, 138 pets were sampled (rectum, mouth, wounds if applicable) in 9 veterinary clinics (VC). The prevalence of AB carriage was 6.5% (95%CI; 2.4, 10.6) and 9 carriers were identified from 4 VC. Hospitalization in a VC and antimicrobial treatment administered within the 15 preceding days were significantly associated with AB carriage (P<0.01 and P<0.05, respectively). Despite the VC in which animals have been sampled were located all around RI, most isolates (8/9) were closely-related (>90% similarity by pulsed-field gel electrophoresis). Additional studies are needed to improve the understanding about interactions between the different reservoirs of AB in RI.

Influence of fluoride, hydrogen peroxide and lactic acid on the corrosion resistance of commercially pure titanium

Titanium is widely used in dental implantology and orthopaedics due to its excellent corrosion resistance and mechanical properties. However, it has been reported that Ti is sensitive to F(-), H(2)O(2) and lactic acid. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate the corrosion resistance of CP-Ti disks after 9 days immersion in different test solutions, based on artificial saliva containing F(-) (0.5% and 2.5%), H(2)O(2) (0.1% and 10%) and/or lactic acid. Because activated macrophages and bacteria can also release locally some of these oxidative compounds, we investigated the role of these cells when plated onto titanium disks. The surface roughness (R(a)) was highly increased when titanium disks were immersed in artificial saliva containing F(-), H(2)O(2) and lactic acid. After 21 days of cell culture, R(a) was significantly increased on disks incubated with activated-J774.2 cells or Streptococcus mitis. AFM appeared to be more sensitive than SEM in evaluating the corrosion of the titanium. Chemical species, either environmental or those released by macrophages and bacteria, can provoke a marked attack of the titanium surface.

[Acinetobacter, a nosocomial pathogen. Contribution of experimental models]

EPIDEMIOLOGY

The increasing importance of Acinetobacter as a nosocomial pathogen responsible for outbreaks in intensive care units has been pointed out for twenty years. Today Acinetobacter infections are essentially pneumonia in patients under mechanical ventilation.

EXPERIMENTAL MODELS

Most clinical isolates are resistant to b-lactam antibiotics as well as to other drugs. Animal models represent an essential step between in vivo testing an<d clinical studies, necessary to understand physiopathology, pharmacology and efficacy of therapy. The virulence of clinical isolates of Acinetobacter spp has been studied in a mouse model of systemic infection. Pharmacological studies and efficacy of antibiotics have been studied in a mouse model of Acinetobacter pneumonia.

HUMAN THERAPEUTICS

The majority of strains are multi-resistant to antibiotics and the infections they cause are difficult to treat. Isolated or combined Sulbactam has often been used with success.

[Treatment of genital infections in gynecology]

Choice of antimicrobial agents and length of therapy of infections of the female genital tract and chemotherapy are presented with particular mention to their side effects. Clinical approach and antibiotic regimens of pelvic inflammatory diseases are discussed.

Accuracy of delayed cultures of plugged telescoping catheter samples for diagnosing bacterial pneumonia

OBJECTIVE

It is not always feasible to culture immediately bacteriologic samples of protected pulmonary specimens on a 24-hr basis before starting antibiotic treatment. We have evaluated the effect of delaying the culture of immediate plugged telescoping catheter (PTC) samples performed before starting antibiotherapy.

DESIGN

Prospective paired comparisons study.

SETTING

Intensive care unit in a university hospital.

PATIENTS

Ninety-nine PTCs were performed on 68 intensive care unit patients suspected of nosocomial or community- acquired bacterial pneumonia.

INTERVENTION

PTC samples were divided into two aliquots: one for immediate (H0) analysis and one for storage at 4 degrees C (H24) for 24 hrs before being cultured.

MEASUREMENTS AND MAIN RESULTS

The results from these delayed cultures (H24) were compared with those from immediate ones (H0). All negative H0 samples (n = 59) were also negative at H24. Forty PTCs yielded one or more microorganisms, with a total of 69 microorganisms in one or both samples. H0 and H24 cultures were concordant in 119 of 128 (97.9%) cases (kappa coefficient value 0.79) with a threshold of 103 colony-forming units (cfu)/mL. Agreement between paired cultures was very good. The bias calculated as the mean difference between paired culture results was 0.128 +/- 1.024 (Deltalog). Concordance using the 103 cfu/mL threshold (102/107 cases, kappa coefficient value 0.82) and agreement were enhanced (0.067 +/- 0.645) when possible contaminants were excluded (n = 21).

CONCLUSIONS

Storing PTC specimens for 24 hrs at 4 degrees C is an acceptable alternative when culturing cannot be performed immediately. This allows starting antibiotic treatment without any delay.

An outbreak of imipenem-resistant Acinetobacter baumannii in critically ill surgical patients

OBJECTIVE

To describe an outbreak of imipenem-resistant Acinetobacter baumannii (IR-Ab) and the measures for its control, and to investigate risk factors for IR-Ab acquisition.

DESIGN

An observational and a case-control study.

SETTING

A surgical intensive care unit (ICU) in a university tertiary care hospital.

METHODS

After admission to the ICU of an IR-Ab-positive patient, patients were prospectively screened for IR-Ab carriage upon admission and then once a week. Environmental cleaning and barrier safety measures were used for IR-Ab carriers. A case-control study was performed to identify factors associated with IR-Ab acquisition. Cases were patients who acquired IR-Ab. Controls were patients who were hospitalized in the ICU at the same time as cases and were exposed to IR-Ab for a similar duration as cases. The following variables were investigated as potential risk factors: baseline characteristics, scores for severity of illness and therapeutic intervention, presence and duration of invasive procedures, and antimicrobial administration.

RESULTS

Beginning in May 1996, the outbreak involved 17 patients over 9 months, of whom 12 acquired IR-Ab (cases), 4 had IR-Ab isolates on admission to the ICU, and 1 could not be classified. Genotypic analysis identified two different IR-Ab isolates, responsible for three clusters. Ten of the 12 nosocomial cases developed infection. Control measures included reinforcement of barrier safety measures, limitation of the number of admissions, and thorough environmental cleaning. No new case was identified after January 1997. Eleven of the 12 cases could be compared to 19 controls. After adjustment for severity of illness, a high individual therapeutic intervention score appeared to be a risk factor for IR-Ab acquisition.

CONCLUSION

The outbreak ended after strict application of control measures. Our results suggest that high work load contributes to IR-Ab acquisition.

In vivo activity of levofloxacin alone or in combination with imipenem or amikacin in a mouse model of Acinetobacter baumannii pneumonia

We evaluated the in vivo activity of levofloxacin alone or in combination with imipenem or amikacin in a mouse model of Acinetobacter baumannii pneumonia using a susceptible strain and one with low-level resistance (MIC/MBC of levofloxacin: 0.06/0.06 and 4/4 mg/L, respectively). As demonstrated previously with other pathogens, the AUC/MIC ratio predicted the efficacy of fluoroquinolones against A. baumannii. This parameter correlated with bactericidal effect and survival. Combination therapy did not enhance the efficacy of levofloxacin.

Nosocomial bacteremia in HIV patients: the role of peripheral venous catheters

A retrospective case-control study compared 40 human immunodeficiency virus (HV)-infected patients with 43 nosocomial bacteremias (NB) to 77 HIV-infected patients without NB. Presence of a peripheral venous catheter (PVC) was associated with occurrence of NB and was significantly more frequent in NB without an identified source. PVCs probably are an underestimated source of NB in HIV-infected patients.

Control of staphylococcal adhesion to polymethylmethacrylate and enhancement of susceptibility to antibiotics by poloxamer 407

We studied the antiadhesive effect of Poloxamer 407 (P407), together with modifications in the antimicrobial susceptibility of residual adherent staphylococci. Bacterial adherence was markedly inhibited (77% to more than 99.9%) whether polymethylmethacrylate was exposed to P407 before or during the adherence assay. Furthermore, residual adherent staphylococci appeared to be more susceptible to antibiotic activity, suggesting that combination of P407 with antibiotics could be a promising approach to the prevention of infection of foreign material.

Nucleotide sequence of the bla(RTG-2) (CARB-5) gene and phylogeny of a new group of carbenicillinases

We determined the nucleotide sequence of the bla gene for the Acinetobacter calcoaceticus beta-lactamase previously described as CARB-5. Alignment of the deduced amino acid sequence with those of known beta-lactamases revealed that CARB-5 possesses an RTG triad in box VII, as described for the Proteus mirabilis GN79 enzyme, instead of the RSG consensus characteristic of the other carbenicillinases. Phylogenetic studies showed that these RTG enzymes constitute a new, separate group, possibly ancestors of the carbenicillinase family.

Microbiological evaluation of central venous catheter administration hubs

We compared, in three intensive care units, colonization of hubs with hub protection boxes or hubs with needleless closed connectors; 137 central venous catheters and 451 hubs were randomized in two groups with similar characteristics. Catheter and hub colonization were not different between the two groups. Among 30 colonized catheters, the same isolate was found in only two hubs; hub contamination rarely is responsible for catheter colonization in short-term catheters. Further studies are required to evaluate the benefit of protected hubs compared with unprotected hubs.

Control of a prolonged outbreak of extended-spectrum beta-lactamase-producing enterobacteriaceae in a university hospital

Extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBLPE) were isolated from clinical specimens from 130 to 140 patients/year in 1989-1991 in our hospital. In February 1992, a control program was initiated: screening tests in 3 intensive care units (ICUs) and contact-isolation precautions in all units. The septic surgical unit served as an isolation ward for surgical patients from whom ESBLPE was isolated. In 1992, the incidence of ESBLPE acquisition failed to decrease, and most acquisitions occurred in 3 ICUs. Critical evaluation of implementation of isolation procedures in these ICUs prompted corrective measures for barrier precautions. The incidence of acquired cases subsequently decreased, and a second evaluation determined that these measures had been correctly applied. The incidence of acquired cases in the septic surgical unit was lower than those in the other units. Decreases were also found in the incidence of acquisition of other hand-transmitted multidrug-resistant organisms. Barrier precautions, screening tests for ICU patients, and grouping of cohorts after ICU discharge are effective in controlling the spread of multidrug-resistant microorganisms by cross-contamination. The outbreak was effectively controlled without restricting antimicrobial use.

[Nosocomial infections]

GLYCOPEPTIDE RESISTANCE: Resistance to glycopeptides raises many therapeutic problems when it occurs in strains such as enterococci or staphylococci causing clinical infections. Two observations described here exemplify the emergence of such resistance in a metacillin-resistant Staphylococcus aureus (MRSA) strain during vancomycin treatment and in a Clostridium difficile strain. NASAL MRSA IN HOSPITAL PERSONNEL: Nasal cavities of hospital personnel is a not well recognized reservoir of MRSA. A survey conducted in a Parisian hospital evidenced problems of personnel-patient transmission. MRSA were found in 6% of the hospital personnel samples.

[Focus on Acinetobacter baumannii]

RESISTANCE

Acinetobacter baumannii carbapeneme-resistance is a serious problem due to the difficulty encountered in treating patients infected with this type of multiresistant bacteria. Several teams have detailed the resistance mechanisms and the way this type of strain spreads around the world. Different factors (plasmid transmission, strain variability) suggest that this type of resistance can diffuse and tends to increase with time. A NEW STRAIN: An outbreak of 15 colonizations with Acinetobacter baumannii, a BLSE producing a type PER-1 enzyme, was described in a neurosurgery intensive care unit in Great Britain. This type of strain has been exception to data and this outbreak emphasizes the problems encountered in controlling the epidemic.

[Some aspects of virulence]

GLYCOPEPTIDE INTERACTION AND THE STAPHYLOCOCCI WALL: Glycopeptides induce modifications in the cell wall of staphylococci. This modification has been observed in VISA strains and could involve bacterial adherence to materials. QUORUM SENSING: Bacterial virulence in Gram-negative germs is closely related to quorum sensing, a system regulated by bacterial inoculum. The use of strains deficient in different steps of quorum sensing in a experimental rat model has been useful in better understanding the pathophysiological effects linked to this system of virulence.

In vivo efficacies of combinations of beta-lactams, beta-lactamase inhibitors, and rifampin against Acinetobacter baumannii in a mouse pneumonia model

The effects of various regimens containing combinations of beta-lactams, beta-lactam inhibitor(s), and rifampin were assessed in a recently described mouse model of Acinetobacter baumannii pneumonia (M. L. Joly-Guillou, M. Wolff, J. J. Pocidalo, F. Walker, and C. Carbon, Antimicrob. Agents Chemother. 41:345-351, 1997). Two aspects of the therapeutic response were studied: the kinetics of the bactericidal effect (treatment was initiated 3 h after intratracheal inoculation, and bacterial counts were determined over a 24-h period) and survival (treatment was initiated 8 h after inoculation, and the cumulative mortality rate was assessed on day 5). Two clinical strains were used: a cephalosporinase-producing strain (SAN-94040) and a multiresistant strain (RCH-69). For SAN-94040 and RCH-69, MICs and MBCs (milligrams per liter) were as follows: ticarcillin, 32, 64, 256, and >256, respectively; ticarcillin-clavulanate, 32, 64, and 512, and >512, respectively; imipenem, 0.5, 0.5, 8, and 32, respectively; sulbactam, 0.5, 0.5, 8, and 8, respectively; and rifampin, 8, 8, 4, and 4, respectively. Against SAN-94040, four regimens, i.e., imipenem, sulbactam, imipenem-rifampin, and ticarcillin-clavulanate (at a 25/1 ratio)-sulbactam produced a true bactericidal effect (>/=3-log10 reduction of CFU/g of lung). The best survival rate (i.e., 93%) was obtained with the combination of ticarcillin-clavulanate-sulbactam, and regimens containing rifampin provided a survival rate of >/=65%. Against RCH-69, only regimens containing rifampin and the combination of imipenem-sulbactam had a true bactericidal effect. The best survival rates (>/=80%) were obtained with regimens containing rifampin and sulbactam. These results suggest that nonclassical combinations of beta-lactams, beta-lactamase inhibitors, and rifampin should be considered for the treatment of nosocomial pneumonia due to A. baumannii.

Practical recommendations for the drug treatment of bacterial infections of the male genital tract including urethritis, epididymitis and prostatitis

Bacterial infections of the male genital tract in young men (<35 years old) are primarily caused by sexually transmissible bacteria like Chlamydia trachomatis, Neisseria gonorrhoeae but also Mycoplasma or Haemophilus spp. In men aged over 35 years, Enterobacteriaceae are more frequently involved in urethritis, epididymitis and prostatitis. The traditional treatments suggested like tetracyclines or erythromycin are less effective since bacterial resistance is increasingly frequent, particularly in N. gonorrhoeae. Moreover, patient compliance with these drug treatments are frequently not well observed. New therapies including short term therapy with fluoroquinolones or azalides (e.g. azithromycin) are very effective and easy to use and thus eliminate any problem of compliance. However, we have to be vigilant for the emergence of resistant strains to these agents.

[Nosocomial infections]

WIDE-SPECTRUM beta-LACTAM PRODUCERS: A French survey demonstrated that Enterobacter aerogenes is currently the preferential host for this plasmid, apparently more so in general hospitals than in University hospitals. CANDIDEMIA: The highest rate of positive blood tests for candida was found in anti-cancer centers. VANCOMYCIN-RESISTANT STRAINS: Reduced susceptibility of methicillin-resistant staphylococci to vancomycin appears to be rather frequent (approximately 10% of strains isolated in one Japanese hospital). It is important to recognize germ populations with a homogeneous or heterogeneous pattern of resistance. In addition, a Spanish survey demonstrated that a large number of inpatients or outpatients harbor vancomycin-resistant enterococci. THE ACINETOBACTER ISSUE: In order to limit the emergence of multiresistant strains and control epidemics, a strong prevention program must be associated with an adapted policy for antibiotic use.

[Virulence and its relationship to antibiotic resistance]

PATHOGENIC ISLANDS: Certain DNA blocks inserted into the chromosome of most Gram negative bacteria originated in pathogens found in plants. VIRULENCE-ANTIBIOTIC INTERACTIONS: During the invasive phase, the bacterial cell covers itself with adhesins which facilitate its adherence to tissues. The bacterial cell produces a fibronectin which protects its defense systems. Antibiotics favor bacterial resistance by increasing the expression of surface adhesins and fibronectin production. PENICILLIN RESISTANT PNEUMOCOCCI: Experimental models have demonstrated that mortality in mice and host resistance to pneumococcal infection are related to the type of capsule and not to antibiotic resistance. QUORUM SENSING: The bacterial inoculum regulates the production of virulence factors in vivo via quorum sensing. This regulation can play an important role in Pseudomonas aeruginosa infections. ACINETOBACTER BAUMANNI VIRULENCE: Long poorly understood, factors favoring A. baumanni virulence appear to result from bacterial production of IROMPs in the extracellular growth medium in response to iron depletion during the exponential growth phase.

[Bacteria of the Acinetobacter genus]

Bacteria of the Acinetobacter genus received little attention for many years because of their weak pathogenic potential and changing taxonomy. Since the introduction starting in the 1980s of an ever increasing number of antimicrobials, these organisms have demonstrated their ability to adapt. They are causing an increasing number of nosocomial infections, most notably in intensive care units. The selection pressure exerted by antimicrobials and the use of increasingly invasive diagnostic and therapeutic procedures are the main factors that promote emergence of Acinetobacter in high-risk patients. Acinetobacter exhibit a high level of resistance to antimicrobials and are capable of persisting in hostile environments (humidity or dryness, presence of some antiseptics). As a result, they can cause nosocomial outbreaks. Identification of carriers and colonized patients, rigorous isolation, and scrupulous cleaning procedures are effective control measures. Despite these efforts, however, Acinetobacter baumannii now contributes a significant proportion of nosocomial infections.

Nosocomial pneumonia in patients with acute respiratory distress syndrome

To describe the epidemiologic and microbial aspects of ventilator-associated pneumonia (VAP) in patients with acute respiratory distress syndrome (ARDS), we prospectively evaluated 243 consecutive patients who required mechanical ventilation (MV) for > or = 48 h, 56 of whom developed ARDS as defined by a Murray lung injury score > 2.5. We did this with bronchoscopic techniques when VAP was clinically suspected, before any modification of existing antimicrobial therapy. For all patients, the diagnosis of pneumonia was established on the basis of culture results of protected-specimen brush (PSB) (> or = 10(3) cfu/ml) and bronchoalvelolar lavage fluid (BALF) (> or = 10(4) cfu/ml) specimens, and direct examination of cells recovered by bronchoalveolar lavage (BAL) (< or = 5% of infected cells). Thirty-one (55%) of the 56 patients with ARDS developed VAP for a total of 41 episodes, as compared with only 53 (28%) of the 187 patients without ARDS for a total of 65 episodes (p = 0.0005). Only 10% of first episodes of VAP in patients with ARDS occurred before Day 7 of MV, as compared with 40% of the episodes in patients without ARDS (p = 0.005). All but two patients with ARDS who developed VAP had received antimicrobial treatment (mostly with broad-spectrum antibiotics) before the onset of infection, as compared with only 35 patients without ARDS (p = 0.004). The organisms most frequently isolated from patients with ARDS and VAP were methicillin-resistant Staphylococcus aureus (23%), nonfermenting gram-negative bacilli (21%), and Enterobacteriaceae (21%). These findings confirm that microbiologically provable VAP occurs far more often in patients with ARDS than in other ventilated patients. Because these patients are often treated with antibiotics early in the course of the syndrome, the onset of VAP is frequently delayed after the first week of MV, and is then caused mainly by methicillin-resistant S. aureus and other multiresistant microorganisms.

Ventilator-associated pneumonia caused by potentially drug-resistant bacteria

To determine risk factors for ventilator-associated pneumonia (VAP) caused by potentially drug-resistant bacteria such as methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, and/or Stenotrophomonas maltophilia, 135 consecutive episodes of VAP observed in a single ICU over a 25-mo period were prospectively studied. For all patients, VAP was diagnosed based on results of bronchoscopic protected specimen brush (> or = 10(3) cfu/ml) and bronchoalveolar lavage (> or = 10(4) cfu/ml) specimens. Seventy-seven episodes were caused by "potentially resistant" bacteria and 58 episodes were caused by "other" organisms. According to logistic regression analysis, three variables among potential factors remained significant: duration of mechanical ventilation (MV) > or = 7 d (odds ratio [OR] = 6.0), prior antibiotic use (OR = 13.5), and prior use of broad-spectrum drugs (third-generation cephalosporin, fluoroquinolone, and/or imipenem) (OR = 4.1). Distribution of the 245 causative bacteria was analyzed according to four groups defined by prior duration of MV (< 7 or > or = 7 d) and prior use or lack of use (within 15 d) of antibiotics. Although 22 episodes of early-onset VAP in patients receiving no prior antibiotics were caused by antibiotic-susceptible bacteria, 84 episodes of late-onset VAP in patients receiving prior antibiotics were mainly caused by potentially resistant bacteria. Differences in the potential efficacies (ranging from 100% to 11%) against microorganisms of 15 antimicrobial regimens were studied according to classification into these four groups. These findings may provide a more rational basis for selecting the initial therapy of patients suspected of having VAP.

[Beta-lactamase inhibitors]

BETA-LACTAMASE: The capacity to produce beta-lactamase, an enzyme which hydrolyses penicillin and cephalosporines, is the main source of bacterial resistance to beta-lactamines, thus the important contribution of beta-lactamase inhibitors (clavanulanic acid, sulbactam and tazobactam).

MECHANISM OF ACTION

Beta-lactamase inhibitors inactivate these enzymes and, in association with beta-lactamines, offer wide spectrum bactericidal action (Gram negative bacilli, anaerobic germs, methicillin-sensitive staphylococci and streptococci) and can be used as first-line treatment in certain community-acquired and nosocomial infections.

SIDE EFFECTS

Widespread use of these inhibitors selects intermediate or resistant strains. Toxicity is low. Undesirable effects (poor digestive tolerance for oral formulations) are dose-dependent. RIGOROUS PRESCRIPTION: Recent development of bacterial resistance emphasizes the importance of rational use of these associations and the need for a better definition of the optimal doses. Prescriptions must avoid underdosing and excessively long treatments. Treatment should be simplified if sensitivity to an antibiotic with a narrower spectrum is recognized.

Usefulness of quantitative cultures of BAL fluid for diagnosing nosocomial pneumonia in ventilated patients

STUDY OBJECTIVE

To evaluate the role of quantitative cultures of BAL for diagnosing nosocomial pneumonia in mechanically ventilated patients.

DESIGN

Cohort study.

SETTING

Medical ICU, Hôpital Bichat, Paris, France, an academic tertiary care center.

PATIENTS

A total of 141 episodes of suspected lung infection in 84 consecutive patients mechanically ventilated for 48 h or more.

MEASUREMENTS AND RESULTS

Microbiologic findings obtained using BAL were compared with those obtained with protected specimen brush (PSB) samples and their operating characteristics were determined. The level of qualitative agreement between BAL and PSB specimen cultures was high, with 83% of the organisms isolated in PSB specimens being recovered simultaneously from BAL fluid. In addition, the results of quantitative BAL and PSB cultures were significantly correlated (rho = 0.46, p < 0.0001). Fifty-seven cases of pneumonia were diagnosed based on the following criteria: PSB sample yielding > or = 10(3) cfu/mL of at least one microorganism and/or > or = 5% of cells containing intracellular bacteria on direct examination of BAL. The operating characteristics of BAL fluid cultures were determined using different ways to report the results and over a range of values. The discriminative value of 10(4) cfu/mL was found to be an optimal threshold, with a sensitivity of 82% (95% confidence interval [CI], 76 to 88) and a specificity of 84.5% (95% CI, 79 to 90).

CONCLUSIONS

These results indicate that BAL fluid cultures can offer a sensitive and specific means to diagnose pneumonia in ventilated patients and may provide relevant information about the causative pathogens.

Use of a new mouse model of Acinetobacter baumannii pneumonia to evaluate the postantibiotic effect of imipenem

Acinetobacter baumannii is responsible for severe nosocomial pneumonia. To evaluate new therapeutic regimens for infections due to multiresistant strains and to study the pharmacodynamic properties of various antibiotics, we developed an experimental mouse model of acute A. baumannii pneumonia. C3H/HeN mice rendered transiently neutropenic were infected intratracheally with 5 x 10(6) CFU of A. baumannii. The mean log10 CFU/g of lung homogenate (+/- the standard deviation) were 9 +/- 0.9, 9.4 +/- 0.8, 8.6 +/- 1.2, and 7.7 +/- 1.4 on days 1, 2, 3, and 4 postinoculation. The lung pathology was characterized by pneumonitis with edema and a patchy distribution of hemorrhages in the peribronchovascular spaces of both lungs. Abscesses formed on days 3 and 4. Four days after inoculation, subacute pneumonitis characterized by alveolar macrophage proliferation and areas of fibrosis was observed. The cumulative mortality on day 4 was 85%. This new model was used to study the effects of 1, 2, or 3 50-mg/kg doses of imipenem. Imipenem concentrations in lungs were above the MIC for 2 h after the last dose. The in vivo postantibiotic effect (PAE) was determined during the 9-h period following the last dose; it decreased in duration with the number of doses: 9.6, 6.4, and 4 h after 1, 2, and 3 50-mg/kg doses, respectively. In contrast, no in vitro PAE was observed. This model offers a reproducible acute course of A. baumannii pneumonia. The presence of a prolonged in vivo PAE supports the currently recommended dosing intervals of imipenem for the treatment of human infections due to A. baumannii, i.e., 15 mg/kg three times a day.

Characterisation of DNA gyrase and measurement of drug accumulation in clinical isolates of Acinetobacter baumannii resistant to fluoroquinolones

Twelve clinical isolates of Acinetobacter baumannii highly resistant to pefloxacin (MIC > or = 32 mg/L) and to ciprofloxacin (MIC > or = 16 mg/L), were studied. A susceptible isolate used as a reference (MIC of 0.032 and 0.25 mg/L for ciprofloxacin and pefloxacin, respectively) accumulated 85 mg of pefloxacin per litre of cell volume within 10 min, from a solution containing 10 mg/L of antibiotic. One resistant isolate accumulated the same amount of pefloxacin, while the 11 others accumulated between 40 and 70 mg/L of cell volume. The differences between reference and resistant isolates with respect to ciprofloxacin and sparfloxacin accumulation were less pronounced. There were no apparent differences in the outer membrane protein profiles of susceptible and resistant isolates. DNA gyrase was isolated from four A. baumannii and the minimum concentration of fluoroquinolones, required to inhibit gyrase-catalysed supercoiling of plasmid DNA was 5- to 80-fold higher for the resistant isolates than for the reference strain. Although most isolates showed some degree of reduced fluoroquinolone accumulation, a DNA gyrase mutation was more likely to be the main mechanism of the high level resistance encountered.

[Comparative study of minimal inhibiting concentrations of doxycycline, ofloxacin and erythromycin against 18 recent isolates from Chlamydia trachomatis (1994-1995)]

In vitro activity of the 3 antimicrobial agents, against 18 recent isolates of Chlamydia trachomatis: 11 from urethral samples and 7 from endocervical samples, was tested by cell culture technique. HeLa 229 cells maintained in antibiotic-free MEM medium supplemented with 10% fetal calf serum and 2 mM glutamine were seeded into 96-well culture plates. After inoculation with 10(2) to 10(3) inclusion-forming units/ml of each strain of C. trachomatis, the culture medium was replaced by a maintenance medium containing 1 micrograms/ml of cycloheximide and serial two fold dilutions of the antibiotics. After 48 h incubation at 36 degrees C in 5% CO2 atmosphere, cells were fixed and inclusion bodies were stained using fluorescein-conjugated anti-Chlamydia monoclonal antibodies. MICs were defined as the lowest antibiotic concentrations required to inhibit the development of a single inclusion. MICs 90% (mg/l) were 0.054 for doxycyclin, 0.700 for ofloxacin and 0.150 for erythromycin. These results confirm the effective in vitro activity of the three antibiotics tested against C. trachomatis.

[Bacteria isolated in 1994-1995 in female upper genitalia infections and in male urethritis. Distribution and sensitivity to antibiotics]

OBJECTIVE

Classify antibiotics according to their individual activity so as to identify those suitable for empiric therapy.

METHODS

We studied bacterial strains isolated from patients with urethritis (n = 189) and upper genital tract infections (n = 163) between June 1994 and February 1995 in 3 hospital and 4 community laboratories. Upper genital tract infections were divided into two groups: proven infection on laparoscopy specimen (n = 79) and suspected infection with isolation of pathogen in cervical samples (n = 84). Pathogens isolated were: Chlamydia trachomatis in 36/12/15 cases respectively, Mycoplasma hominis in 12/20/13, Ureaplasma urealyticum in 55/30/15, Neisseria gonorrhoeae in 40/2/0, Haemophilus spp in 20/2/1, group B streptococci in 7/1/8, E. coli in 8/1/17 and miscellaneous in 11/8/15. The minimal inhibitory concentrations for all strains were determined in 4 laboratories for ofloxacin, erythromycin and doxycyclin against C. trachomatis, M. hominis and U. urealyticum, and for ofloxacin, erythromycin, doxycyclin, amoxicillin+clavulanate, cefotaxime and gentamicin against the other strains. The activity score (% susceptibility to each antibiotic weighted by the frequencies of each isolate in urethritis and upper genital tract infection based on recent French epidemiologic data) was calculated for each antibiotic.

CONCLUSION

The antibiotics with the best empiric activity scores in urethritis were, in decreasing order: doxycyclin (90.4%), ofloxacin (88.1%), and erythromycin (50.2%). The most active combinations in upper genital tract infections were ofloxacin+amoxicillin (100%), doxycyclin+cefotaxime+metronidazole (95.9%) and doxycyclin+amoxicillin (95.3%).

Bactericidal in-vitro activity of beta-lactams and beta-lactamase inhibitors, alone or associated, against clinical strains of Acinetobacter baumannii: effect of combination with aminoglycosides

Five Acinetobacter baumannii strains of various phenotypes were selected on the basis of the results of a national survey in France in 1991. beta-Lactamases in Acinetobacter isolates were characterized by isoelectrofocusing. We carried out a 24 h time-kill study to assess the bactericidal effect of antibiotic alone or in combination against A. baumannii strains. The initial inoculum was 10(6) cfu/mL. Antibiotics were tested at MIC x 2 when an antibiotic was tested alone and at the MIC for each combination including ticarcillin, piperacillin, ceftazidime or imipenem with or without amikacin or netilmicin and/or beta-lactamase inhibitors. Concentration of inhibitors were: 2 mg/L for clavulanic acid, 4 mg/L for tazobactam and 8 mg/L for sulbactam. Sulbactam and tazobactam showed an intrinsic in-vitro activity against strains susceptible to ticarcillin. A complete killing at 24 h was observed when beta-lactams were combined with amikacin in comparison with antibiotics alone. Synergy was lost when the strain presented a low resistance level to beta-lactams or aminoglycosides except for ticarcillin. Combinations of sulbactam with ticarcillin showed the best bactericidal activity against strains multiresistant to beta-lactams.

Role of quantitative cultures of endotracheal aspirates in the diagnosis of nosocomial pneumonia

To assess the reliability of quantitative cultures of endotracheal aspirates (EA) to diagnose ventilator-associated pneumonia, fiberoptic bronchoscopy was used to study 57 episodes of suspected lung infection in 39 patients with no recent changes in antimicrobial chemotherapy. A total of 19 cases (33%) of pneumonia were diagnosed based on the following criteria: protected specimen brush (PBS) sampling yielding > or = 10(3) cfu/ml of at least one microorganism and/or > or = 5% of cells containing intracellular bacteria on direct examination of bronchoalveolar lavage (BAL). The operating characteristics of EA cultures were calculated over a range of cutoff values (from 10(3) to 10(7) cfu/ml), and the threshold of 10(6) cfu/ml appeared to be the most accurate, with a sensitivity of 68% and a specificity of 84%. Microorganisms cultured from EA samples correlated weakly with those obtained using PSB specimens (rho = 0.32), with only 49 microorganisms among 123 (40%) found in both samples. These latter results and the relatively low sensitivity of the technique indicate that EA quantitative cultures are of limited value for the diagnosis of pneumonia in ventilated patients when fiberoptic techniques are available.

In vitro brodimoprim activity on bacterial strains

The antibacterial activity of brodimoprim (BDP) was compared to that of trimethoprim (TMP) and to 4 other antibiotics (3 beta-lactams and one macrolide). The 237 tested strains were selected predominantly among bacteria isolated from respiratory tract infections: 133 Gram-negative bacilli and 98 Gram-positive cocci. The study included: determination of minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of all antibiotics of the study for all isolates; kinetics of bactericidal activities for selected susceptible strains; correlation between MICs and inhibition zones (standard agar diffusion technique) of BDP (regression line). The results of the study showed: [1] no significant difference between in vitro activities of BDP and TMP against all tested strains; [2] low MICs of both drugs for Haemophilus influenzae, Legionella pneumophila, Staphylococcus aureus (methi-S and methi-R), Streptococcus pneumoniae (peni-S), streptococci and enterococci; [3] kinetics of bactericidal activities indicating 4 log decrease of inoculum size with BDP for Staph. aureus, S. pneumoniae, H. influenzae, within 7 hours; [4] correlation was established between inhibition zones and MICs of BDP, with a coefficient of correlation r = 0.88 for 182 strains. In conclusion, BDP exhibited in vitro antibacterial and bactericidal activities at least equal to that of reference drugs against most respiratory pathogens; BDP was superior to comparators against methi-R staphylococci and enterococci.

Opportunistic nosocomial multiply resistant bacterial infections--their treatment and prevention

One of the most difficult problems confronting the clinician who deals with nosocomial infections is that of microbial resistance. The predominant nosocomial infections (urinary tract infections, pneumonia, septicaemia, surgical wound infections) involve increasing numbers of Gram-positive bacteria, Staphylococcus epidermidis, Corynebacterium jeikeium or resistant enterococci as well as new multiresistant Gram-negative bacilli such as Xanthomonas maltophilia, Acinetobacter baumannii and Alcaligenes xylosoxydans. The emergence and spread of Klebsiella pneumoniae and other Enterobacteriaceae producing novel plasmid-mediated beta-lactamases active against third-generation cephalosporins contribute to the difficulty in treating nosocomial infections.

Hospital infection with Acinetobacter spp.: an increasing problem

During the last few years, among nosocomial pathogens, Acinetobacter spp. have given rise to an increasing number of nosocomial infections. Acinetobacter strains are widely distributed in nature; in hospitals, the human skin is the likely source for most outbreaks of hospital infections. The organism has been frequently found in the inanimate environment, especially in moist situations and it has been isolated from various types of opportunistic infections (septicaemia, endocarditis, meningitis, pneumonia, skin and wound sepsis and urinary tract infection). For epidemiological studies, various typing methods such as biotyping, bacteriocin typing and serology have been developed. More recently electrophoretic patterns of cell-envelope proteins and plasmid analysis have proved useful in differentiating outbreak strains. Antibiogram typing may be useful but the antibiotic resistance of Acinetobacter spp. has changed rapidly within the last few years and thus antibiotyping must be complemented by other typing systems. New methods such as electrophoretic analysis of isoenzymes, definition of plasmidotype profiles or restriction endonuclease digestion of chromosomal DNA are under investigation.

[In vitro antibacterial activity of a new fluoroquinolone, temafloxacin, against hospital isolates. Results of a multicenter study]

Minimal inhibitory concentrations (MICs) of temafloxacin (TMF) was determined by agar dilution for 2,510 bacterial strains isolated in 1989 in 9 university hospitals. Activity of TMF against nalidixic acid (NAL) susceptible (S) Enterobacteriaceae was close to that of other fluoroquinolones (FQ) (mode MIC: 0.06 micrograms/l); like for other FQ, this activity was reduced against NAL intermediate (mode 1) and resistant (R) (mode 4) Enterobacteriaceae. MICs of TMF against P. aeruginosa were between 0.12 and 128 (mode 0.5-1). TMF had also a good activity against NAL S A. baumannii (mode MIC: 0.06-0.12) but this activity is reduced against NAL R Acinetobacter (mode MIC: 16). TMF was highly active against Haemophilus mode MIC: less than or equal to 0.008), Gonococci (mode MIC: 0.008-0.032), Meningococci (mode MIC: 0.08) and B. catarrhalis (mode MIC: 0.016). TMF showed better activity to other fluoroquinolones against methicillin susceptible Staphylococci (mode MIC: 0.06); the resistant strains (mode MIC: 8) are usually methicillin resistant. Comparatively to the currently available FQ, TMF is so more effective against Enterococci (mode MIC: 1), Streptococci (mode MIC: 0.5-1) and Pneumococci (mode MIC: 0.5). Finally, for the anaerobic bacteria, TMF is more active against C. perfringens (mode MIC: 0.5) than against B. fragilis (mode MIC: 2).

A study of the relationships between antibiotic resistance phenotypes, phage-typing and biotyping of 117 clinical isolates of Acinetobacter spp

Two typing systems were used to conduct an epidemiological study of Acinetobacter and to establish their relationship to antibiotic resistance phenotypes. Biotyping was performed with biochemical tests according to the new definition of Acinetobacter baumannii (18 biotypes). Phage typing included two complementary systems: 125 phage-types and 25 subtypes. Resistance phenotype analysis included 11 antibiotics. The results of the study showed that: (1) nine phage-types or subtypes (67%) and two groups of atypical phage-types (5%) or of untypable strains (28%), could be defined; (2) all strains that were resistant to carboxy/ureido-penicillins and cephalosporins (62%) belonged to biotypes 6 or 9; among them 70% belonged to phage-types 17 or 124; (3) imipenem resistance was observed in five isolates of biotype 9 and one of biotype 6; (4) a phenotype including resistance to third generation cephalosporins (but not carboxypenicillins) and to amikacin (but not tobramycin) represented 8.5% of the isolates; 90% of them belonged to biotype 1 and were not phage-typable; (5) 15% of the isolates were not identified as A. baumannii; among them five Acinetobacter haemolyticus strains all had the same resistance phenotype: amikacin-tobramycin-kanamycin-netilmicin resistant; they were however, susceptible to beta-lactams and to gentamicin. There was a clear relationship between biotypes 6 and 9 and phage-types 17 and 124 which were the strains most resistant to beta-lactams and aminoglycosides and were predominant in the survey. The three typing systems were complementary but it seems that antibiotic resistance phenotypes and one of the two other typing systems would be required in parallel to provide suitable information for epidemiological purposes.

[Comparative activity of imipenem, ceftazidime and cefotaxime against Acinetobacter calcoaceticus]

The authors compared the in vitro activity of imipenem, ceftazidime and cefotaxime against 100 strains of Acinetobacter calcoaceticus isolated in 1986 and 1987. The minimal inhibitory and bactericidal concentrations (MICs and MBCs) were determined by the agar dilution and broth microdilution methods respectively, with and without 50 per cent of human serum in the medium to evaluate the possible influence of protein binding. Imipenem was the most active of the three drugs against Acinetobacter, including beta-lactamase producing strains. The MICs 50 and 90 of imipenem were 0.18 micrograms/ml and 0.48 micrograms/ml respectively, as opposed to 5.16 and 14.61 micrograms/ml for ceftazidime, 16 and 75.6 micrograms/ml for cefotaxime. No change was noted in the susceptibility of Acinetobacter to imipenem from 1981 to 1987. The geometric mean MIC of imipenem was 0.25 micrograms/ml. Susceptibility remained unchanged for ceftazidime and cefotaxime but the geometric mean MICs were higher, being 7.29 and 22.8 micrograms/ml respectively. Imipenem had the highest bactericidal activity, with a mean MBC/MIC ratio of 1.16. The presence of human serum did not influence the results, due to the low protein binding of all three antibiotics. It is concluded that imipenem is one of the major antibiotics available for the treatment of nosocomial Acinetobacter infections. However, a few resistant strains have recently been isolated, confirming the need for epidemiological surveillance of bacterial resistance to this antibiotic.

[Epidemiology of Acinetobacter and resistance to antibiotics at hospitals. A 5-year evaluation]

The growing number of Acinetobacter strains in hospitals and the rapid increase of their resistance to antibiotics have prompted us to undertake a long-term epidemiological study of this resistance at the Bichat hospital, Paris. Between 1971 and 1984, the resistance of Acinetobacter to antibiotics had already progressed, with only some antibiotics (imipenem, ceftazidime, tobramycin and amikacin) remaining active. During the following 5 years (1984-1988) a study of 1056 strains demonstrated a further increase of resistance and showed how serious the problem was in intensive care units. During the last few years, there has been a considerable increase in the proportion of multiresistant strains, reaching 84 per cent with beta-lactam antibiotics and 64 per cent with aminoglycosides. At present, in most cases the only effective treatment is imipenem, and no antibiotic is active in 5.5 per cent of the cases. Studies of lysotypes, enzymes and phenotypic resistance of bacterial strains completed the epidemiological approach, showing the presence of dominant lysotypes. Two predominant lysotypes are associated with multiresistance of Acinetobacter strains responsible for nosocomial infections.

Novel carbenicillin-hydrolyzing beta-lactamase (CARB-5) from Acinetobacter calcoaceticus var. anitratus

A strain of Acinetobacter calcoaceticus var. anitratus highly resistant to ticarcillin but susceptible to ticarcillin in combination with clavulanic acid (2 mg/l) was found to produce a constitutive beta-lactamase. This enzyme was periplasmic with a characteristic substrate profile of a carbenicillin-hydrolyzing enzyme. Enzyme inhibition was detected with antiserum (anti-CARB-3), pCMB, cloxacillin, clavulanic acid and sulbactam. This novel enzyme with a molecular mass of 28,000 resembles other plasmid-mediated carbenicillinases (CARB) but differs in its apparent isoelectric point estimated as 6.3 and has been designated CARB-5 on this basis.

[Nosocomial infections caused by Acinetobacter. Epidemiology and therapeutic difficulties]

Nosocomial infections due to Acinetobacter calcoaceticus are not easy to treat particularly in intensive-care and surgical units. Our study included 33 cases of nosocomial infections which developed during 1987 in the surgical intensive care unit and in the urology department. Acinetobacter was isolated from various types of nosocomial infections: urinary tract infections (43 per cent); septicaemia (15 per cent); surgical infections (27 per cent) and respiratory tract infections (15 per cent). Forty eight per cent of the patients received an antibiotic therapy and 52 per cent had no specific treatment. The following beta-lactam antibiotics were studied: ticarcilline, mezlocilline, cefotaxime and ceftazidime, and 83 per cent of the strains were TICRMEZRCTXR (phenotype IV). All the strains except one were imipenem susceptible. The study of aminoglycoside resistance in Acinetobacter showed that 91 per cent of the strains were gentamicin resistant (GENR); 25.5 per cent were gentamicin, and amikacin resistant and tobramycin susceptible (GENR AMKR TOBS, phenotype IV), and 45 per cent were GENR TOBR AMKR (phenotype V). Acinetobacter strains were resistant and 63 per cent pefloxacin resistant. Co-trimoxazole resistant strains represented 65 per cent of the strains. Should major antibiotics be used to treat nosocomial infections due to multiresistant Acinetobacter strains? Are prophylaxis, aseptic and surgical procedures sufficient to control these infections?

[In vitro antibacterial activity of apalcillin on aerobic bacteria and the regression curve]

Minimal inhibitory concentrations (MICs) of apalcillin (APL) were evaluated by agar dilution on 1,201 bacterial strains isolated simultaneously in four university hospitals; agar diffusion tests (disks APL: 75 micrograms) were performed on these strains to establish relationship between MIC and zone diameters. For Enterobacteriaceae naturally non beta-lactamase-producing (E. coli and P. mirabilis), mode MIC was 0.5 microgram/ml; some acquired penicillinase-producing strains were only inhibited by concentrations greater than or equal to 16. Chromosomal penicillinase producing Klebsiella were inhibited by 2 to 8 micrograms/ml but APL was inactive on acquired penicillinase-producing strains. For chromosomal cephalosporinase-producing species (Enterobacter, Citrobacter, Serratia, indole + Proteus and Providencia) two populations of strains were observed: one sensitive and the second resistant to carboxypenicillins: on the first population, mode MIC of APL was 1 to 4 micrograms/ml; on the second MIC were generally greater than or equal to 64 micrograms/ml. P. aeruginosa strains sensitive to carboxypenicillins were inhibited by 1 and 2 micrograms/ml; this activity was diminished on strains resistant to these antibiotics (MIC APL 8-32). MIC of Acinetobacter varied to 0.25 to greater than 128 with a majority of strains inhibited by 4 to 64 micrograms/ml. APL was active against non penicillinase producing Staphylococci; mode MIC was 2 micrograms/ml for Enterococci. Correlation coefficient of regression curve was 0.87. For critical concentrations less than or equal to 8 and greater than 64 micrograms/ml, critical diameters could be greater than or equal to 19 and less than 12 mm.

[Fosfomycin-trometamol (monuril): pharmacokinetics and food-drug interactions]

A new water soluble monobasic salt of fosfomycin with trometamol has been recently developed for oral administration. The objective of this study was to evaluate the pharmacokinetics of trometamol-fosfomycin (monuril) in serum and urine in 10 healthy volunteers after oral administration of one single dose (50 mg/kg). In the volunteers, the concentrations of fosfomycin were measured before and after food absorption in serum and urine samples taken at t = 0, 2, 4, 6, 8, 24 h after the dose (plus 0.5 hand 1 h for serum samples). The measurement of fosfomycin levels was carried out by means of a microbiological procedure using Proteus mirabilis ATCC 21100 as test organism. The results indicated at 2 h after oral administration of the antibiotic, a mean serum peak level of 21.04 +/- 6.88 micrograms/ml. The urine concentrations reached 2,000 to 2,750 micrograms/ml at the 2nd hour, with high levels (mean: 1,876 +/- 709 micrograms/ml) till the 8th hour and persistence of noticeable concentrations at 24 h (334 +/- 210 micrograms/ml). The influence of food absorption, even variable, decreased significantly the rate of absorption with lower serum and urine levels. Taking into account this factor influencing the bioavailability and the distribution of the drug, the results of the study confirm that a high proportion of the oral dose of trometamine salt of fosfomycin is well absorbed; the extremely high urinary recovery of the drug could certainly allow short course therapy in the treatment of uncomplicated urinary tract infection.

[Evaluation of the ATB system and the 32 GN tests for the identification and determination of the antibiotic sensitivity of Acinetobacter calcoaceticus var. anitratum. Comparison with the reference dilution method in a gel medium]

The authors determined the susceptibility to 24 antibiotics of 95 strains of Acinetobacter calcoaceticus variety anitratum with the automated API ATB System in comparison with the agar dilution method for MIC measurement. The strains have been identified with API 32 GN (automated system) and API NE. There was a good agreement between the two sets of identification results. In susceptibility tests the discrepancies ranged from 0.86% to 3% with a mean value of 1.8%. The overall agreement was 95% between the two methods. This study allowed the authors to define susceptibility phenotypes to the three major antibiotic classes: beta-lactams, aminoglycosides and quinolones. The use of 32 GN tests and ATB in the automated system seems very useful, especially in epidemiologic studies in order to analyse numerous data in a short time.

Trometamol-fosfomycin (Monuril) bioavailability and food-drug interaction

A new water-soluble monobasic salt of fosfomycin with trometamol has recently been developed for oral administration. The objective of this study was to evaluate the pharmacokinetics of trometamol-fosfomycin (Monuril) in serum and in urine in 10 healthy volunteers after oral administration of one single dose (50 mg/kg). In the same volunteers the concentrations of fosfomycin were measured before and after food absorption, in serum and urine samples taken at t = 0, 2, 4, 6, 8 and 24 h after the dose (plus 0.5 and 1 h for serum samples). The measurement of fosfomycin levels was carried out by means of a microbiological procedure using Proteus mirabilis ATCC 21100 as test organism. The results indicated at 2 or 4 h serum peak levels ranging from 9 to 28 micrograms/ml, with mean values of about 17-21 micrograms/ml. The urine concentrations reached 2,000-2,500 micrograms/ml at 2 h, with high levels maintained till the 8th hour (1,200-2,750 micrograms/ml) and persistence of noticeable concentrations at 24 h (100-700 micrograms/ml). The influence of food absorption, even variable, decreased significantly the rate of absorption, with lower serum and urine levels, as measured in the same volunteers. Taking into account this factor influencing the bioavailability and the distribution of the drug, the results of the study confirm that a high proportion of the oral dose of trometamine salt of fosfomycin is absorbed; the extremely high urinary recovery of the drug even after food administration could certainly allow short-course therapy or even single-dose therapy in the treatment of uncomplicated urinary tract infection.

Comparative activity of imipenem, ceftazidime and cefotaxime against Acinetobacter calcoaceticus

Imipenem was the most active drug against Acinetobacter, even against strains possessing beta-lactamases. MICs of imipenem for 50% and 90% of the A. calcoaceticus (var. anitratum) were 0.28 and 0.61 mg/l respectively whereas for ceftazidime they were 4.4 and 10.0, and for cefotaxime, 7.9 and 22.2 mg/l. No change occurred in the in-vitro activity of imipenem against Acinetobacter, during the period 1980-1985. Geometric mean MICs in 1985 were 0.33 mg/l for A. calcoaceticus var. anitratum; the values were lower for A. calcoaceticus var. lwoffi. Ceftazidime and cefotaxime MICs were also stable from 1981 to 1985, but the values were higher, geometric mean MICs being 5.3 and 10.1 mg/l respectively. MBCs of imipenem for A. calcoaceticus var. anitratum ranged from 0.194 to 0.35 mg/l; the ratio MBC/MIC was 1.17.

[Comparative activity in vitro of ceftizoxime, ceftazidime and imipenem against Acinetobacter calcoaceticus]

Acinetobacter calcoaceticus, a nosocomial pathogenic agent, is isolated with increasing frequency from hospitalized patients. Acinetobacter is one of the most resistant pathogens to currently available antibiotics, particularly beta-lactam antibiotics. Beta-lactamases (TEM penicillinase and cephalosporinase) and problems of permeability are the most frequent mechanisms of resistance. The authors compared the in vitro activity of ceftizoxim, ceftazidim and imipenem against 82 clinical isolates of Acinetobacter calcoaceticus. Ceftizoxim, structurally similar to cefotaxim, was highly active in vitro; MIC 50%, 90% and geometric mean were respectively 6.28, 15 and 6.9 micrograms/ml. A significant difference was observed between the anitratum and lwoffi varieties. The lwoffi variety was more susceptible to tested drugs than the anitratum variety. Ceftazidim activity was comparable with MIC 50 of 6.5 micrograms/ml and MIC 90 of 26.2 micrograms/ml. A good bactericidal activity was observed against susceptible strains (MIC less than or equal to 4 micrograms/ml). Imipenem showed the greatest activity since 0.47 microgram/ml of the drug inhibited 90% of Acinetobacter calcoaceticus.