Two-step acquisition of resistance to the teicoplanin-gentamicin combination by VanB-type Enterococcus faecalis in vitro and in experimental endocarditis

The activity of vancomycin and teicoplanin combined with gentamicin was investigated in vitro against strains of Enterococcus faecalis resistant to vancomycin and susceptible to teicoplanin (VanB type) and against mutants that had acquired resistance to teicoplanin by three different mechanisms. In vitro, gentamicin selected mutants with two- to sixfold increases in the level of resistance to this antibiotic at frequencies of 10(-6) to 10(-7). Teicoplanin selected teicoplanin-resistant mutants at similar frequencies. Both mutations were required to abolish the activity of the gentamicin-teicoplanin combination. As expected, simultaneous acquisition of the two types of mutations was not observed. In therapy with gentamicin or teicoplanin alone, each selected mutants in three of seven rabbits with aortic endocarditis due to VanB-type E. faecalis BM4275. The vancomycin-gentamicin combination selected mutants that were resistant to gentamicin and to the combination. In contrast, the teicoplanin-gentamicin regimen prevented the emergence of mutants resistant to one or both components of the combination. These results suggest that two mutations are also required to suppress the in vivo activity of the teicoplanin-gentamicin combination.

Activity and diffusion of LY333328 in experimental endocarditis due to vancomycin-resistant Enterococcus faecalis

The activity of LY333328 against Enterococcus faecalis JH2-2, which is susceptible to glycopeptides, and against its transconjugants E. faecalis BM4281 and BM4316, with VanB and VanA phenotypes, respectively, was investigated. LY333328 was active in vitro against the three strains, for which MICs were 2 microg/ml on agar and 0.25 microg/ml in broth. LY333328 was bactericidal in broth against E. faecalis JH2-2 and BM4281 at a concentration of 8 microg/ml and against BM4316 at a concentration of 30 microg/ml. The protein binding of LY333328 to rabbit serum was >99%, and the bactericidal activity of LY333328 in broth was reduced when it was tested in the presence of 90% rabbit serum. Autoradiographic studies performed in rabbits with enterococcal endocarditis showed that 14[C]LY333328 was distributed heterogeneously throughout cardiac vegetations. In rabbits with aortic endocarditis, a regimen of 20 mg of LY333328 per kg of body weight administered intramuscularly twice a day for 5 days after a loading dose of 40 mg/kg was active against the three strains in vivo (P < 0.01), whereas vancomycin was not active against the VanB-type strain and teicoplanin was not active against the VanA-type strain. We conclude that the activity of LY333328 is not significantly modified by acquired resistance to glycopeptides in E. faecalis either in vitro or in experimental endocarditis.

Regression of rectal stenosis secondary to neoplasm in an HIV1-positive patient with gancyclovir antiviral therapy: report of a case

PURPOSE

The case of a human immunodeficiency virus-positive patient with rectal stenosis caused by a tumor that completely regressed in response to gancyclovir is presented.

METHODS

Several biopsies from the tumoral mass failed to show any stigmata of non-Hodgkin's lymphoma, adenocarcinoma, or Kaposi sarcoma. No parasites could be detected in rectal biopsies. Viral inclusions showing both Epstein-Barr virus and cytomegalovirus on immunostained sections suggested an unusual form of viral infection.

RESULTS

Antiviral therapy (gancyclovir 10 mg/kg/day) had a dramatic effect on pain and discharge of blood, and suppressed rectal difficulties within three days of therapy. The antiviral treatment was stopped at Day 10 because of leukopenia. Endoscopic and histologic examinations revealed normal rectal mucosa after 3, 6, 9, 12, and 18 months of follow-up.

CONCLUSION

This is the first case of complete and long-term regression of a rectal stenosis secondary to a tumoral mass in response to antiviral therapy in patients with human immunodeficiency virus.

[The contribution of experimental models to the physiopathology and treatment of infectious endocarditis]

The model of experimental endocarditis can be used for the investigation of the different steps in the physiopathologic process leading to the formation of the infected cardiac vegetation. It has also greatly contributed to the knowledge of the characteristics of the infected vegetation. These data allow a better understanding of the therapeutic consequences (both preventive and curative) of the physiopathologic process.

Critical importance of in vivo amoxicillin and cefotaxime concentrations for synergy in treatment of experimental Enterococcus faecalis endocarditis

The synergy between amoxicillin and cefotaxime against two strains of Enterococcus faecalis (JH2-2 and 6370) in vitro and in rabbit endocarditis was investigated. In vitro synergy was obtained only when amoxicillin concentrations were below the MBC and when cefotaxime concentrations were above 1 microg/ml. No synergy was observed in vivo, because of the short period of time during which these pharmacologic requirements were achieved.

[Manifestations and diagnosis of extrapulmonary tuberculosis]

Extra pulmonary tuberculosis currently represents 25 per cent of notified tuberculosis in France. All organs can be involved but the most frequent localisation are the lymph nodes. Immunodepressed patients notably those infected with HIV are particularly prone to a polyvisceral tuberculous infection. The diagnosis is often difficult on account of the polymorphism of the disease and the weak specificity of the clinical manifestation. A firm diagnosis always rests on histological or microbiological evidence. Certain recent developments should enable a more rapid microbiological diagnosis notably as a result of development in molecular biology and rapid culture techniques. The mortality and morbidity remain elevated in developing counties as in industrialised counties and clinical situations in which extra pulmonary tuberculosis occur often worsen the prognosis.

Influence of inducible cross-resistance to macrolides, lincosamides, and streptogramin B-type antibiotics in Enterococcus faecium on activity of quinupristin-dalfopristin in vitro and in rabbits with experimental endocarditis

The influence of inducible cross-resistance to macrolides, lincosamides, and streptogramin B (MLS(B)) type antibiotics (inducible MLS(B) phenotype) on the activity of quinupristin-dalfopristin was investigated against Enterococcus faecium in vitro and in rabbits with experimental endocarditis. In vitro, quinupristin-dalfopristin displayed bacteriostatic and bactericidal activities against a MLS(B)-susceptible strain similar to those against two strains with the inducible MLS(B) phenotype. In addition, induction of the two MLS(B)-resistant strains with quinupristin (0.016 to 1 microg/ml) or quinupristin-dalfopristin (0.08 to 0.25 microg/ml) increased the MICs of quinupristin from 8 microg/ml to 32 to > 128 microg/ml, but did not modify the MIC of dalfopristin (2 microg/ml) or quinupristin-dalfopristin (0.5 microg/ml). In a rabbit endocarditis model, quinupristin-dalfopristin was as active as amoxicillin against the MLS(B)-susceptible E. faecium strain. In contrast, the activity of quinupristin-dalfopristin was significantly decreased in animals infected with either of the two inducible MLS(B)-resistant strains (P < 0.05), although no mutants resistant to quinupristin-dalfopristin were detected. Against the clinical strain with the inducible MLS(B) phenotype, quinupristin-dalfopristin was not effective and was less active than amoxicillin (P < 0.001); however, the activity of the combination of amoxicillin and dalfopristin-quinupristin was superior to that of amoxicillin (P < 0.01). The different impact of the inducible MLS(B) phenotype in E. faecium on the activity of quinupristin-dalfopristin in vitro and in experimental endocarditis may be related to the reduced diffusion of dalfopristin compared with that of quinupristin into cardiac vegetations that we previously reported. This result emphasizes the importance of the constant presence of dalfopristin at the site of infection to ensure synergism with quinupristin.

Selection of glycopeptide-resistant mutants of VanB-type Enterococcus faecalis BM4281 in vitro and in experimental endocarditis

Enterococcus faecalis BM4281 is resistant to vancomycin, susceptible to teicoplanin (VanB phenotype), and intrinsically resistant to low levels of gentamicin. The efficacy of glycopeptides against BM4281 was investigated in a rabbit model of experimental endocarditis for reduction of bacterial counts in cardiac vegetations and selection of mutants with increased resistance to glycopeptides. Teicoplanin led to a 100-fold reduction of bacteria in the vegetations, whereas vancomycin had no effect. Monotherapy with either antibiotic selected mutants with homogeneous or heterogeneous resistance to high levels of both glycopeptides. Vancomycin also selected mutants that required the antibiotic for growth. The combination of gentamicin plus teicoplanin was bactericidal, prevented the emergence of mutants, and allowed sterilization of the vegetations in 25% of the rabbits, indicating that the combination may be an alternative if penicillin cannot be used against VanB-type enterococci.

Lymphocyte subset counts during the course of community-acquired pneumonia: evolution according to age, human immunodeficiency virus status, and etiologic microorganisms

We investigated the evolution of lymphocyte subsets in blood samples from 94 consecutive patients with community-acquired pneumonia; these samples were obtained 72 hours after hospitalization and at follow-up, when the patients were considered to be cured. Acute-phase lymphocyte counts, as compared with follow-up counts, were decreased in the overall population (P < .0001); however, the percentage of CD4+ T cells remained unchanged during the course of pneumonia in each patient. These changes that were noted for the overall population were not significantly influenced by age, the presence (or not) of infection with human immunodeficiency virus (HIV), or etiologic microorganisms. Of the 68 HIV-seronegative patients, 12 had initial CD4+ T cell counts of < 200/mm3; multivariate analysis revealed that this finding was significantly associated with the presence of an underlying disease or tuberculosis and an age of > or = 60 years.

Importance of penicillinase production for activity of penicillin alone or in combination with sulbactam in experimental endocarditis due to methicillin-resistant Staphylococcus aureus

The activity of penicillin, alone and in combination with sulbactam, against a heterogeneously methicillin-resistant, penicillinase-producing clinical isolate of Staphylococcus aureus and its penicillinase-negative derivative was investigated in vitro and in a rabbit experimental endocarditis model. Penicillin was significantly more effective than vancomycin against the penicillinase-negative derivative in vivo (P < 0.001), and it sterilized 25% of the vegetations. The combination of penicillin and sulbactam exhibited an in vivo synergistic effect on the penicillinase-producing strain (P < 0.01) but did not produce any advantage over treatment with vancomycin, even when a high dose of sulbactam was used (100 mg/kg of body weight every 6 h). This combination was significantly less effective against the penicillinase-producing strain than was penicillin alone against the penicillinase-negative derivative (P < 0.03). In addition, the most resistant subpopulation of the surviving bacteria, which grew on agar containing 16 micrograms of methicillin per ml, was detected in 5 of 6 animals treated with penicillin and a high dose of sulbactam against the penicillinase-producing strain compared with only 1 of 12 animals treated with penicillin alone against the penicillinase-negative derivative (P < 0.01). We conclude that penicillin is highly effective against penicillinase-negative methicillin-resistant S. aureus and that penicillinase production, rather than methicillin resistance, appears to be the limiting factor for the activity of the penicillin-sulbactam combination against penicillinase-producing, methicillin-resistant S. aureus.

Critical influence of timing of administration of granulocyte colony-stimulating factor on antibacterial effect in experimental endocarditis due to Pseudomonas aeruginosa

The effect of human recombinant granulocyte colony-stimulating factor (hrG-CSF) in rabbits with aortic endocarditis due to Pseudomonas aeruginosa was investigated. hrG-CSF significantly increased the number of polymorphonuclear neutrophils in blood and in cardiac vegetations and the expression of the adhesin molecule CD11b on the surface of polymorphonuclear neutrophils compared with those of animals that had not received hrG-CSF. When treatment was started 72 h after bacterial challenge, hrG-CSF alone had no antibacterial effect and did not enhance the efficacy of ciprofloxacin when used in combination, even with the higher dosing regimen used (50 micrograms/kg of body weight subcutaneously every 12 h for 4 days), in terms of number of positive blood cultures, bacterial counts in vegetations, and survival. In contrast, when treatment was started 30 min prior to bacterial challenge, hrG-CSF (50 micrograms/kg injected every 12 h) decreased bacterial titers in vegetations 72 h later (6.5 +/- 0.9 versus 7.9 +/- 0.9 log10 CFU/g of vegetation for hrG-CSF and controls, respectively; P = prophylactic administration of hrG-CSF did not increase the antibacterial effect of ciprofloxacin. We concluded that the antibacterial effect of hrG-CSF in experimental endocarditis was related to the timing of its administration since hrG-CSF demonstrated a significant but transient antimicrobial effect only when treatment was initiated before bacterial challenge.

Critical influence of resistance to streptogramin B-type antibiotics on activity of RP 59500 (quinupristin-dalfopristin) in experimental endocarditis due to Staphylococcus aureus

In order to determine the microbiological and pharmacokinetic parameters that best predicted the in vivo antistaphylococcal activity of the streptogramin RP 59500 (quinupristin-dalfopristin), we evaluated the activity in rabbit aortic endocarditis of three regimens of quinupristin-dalfopristin against five strains of Staphylococcus aureus with various streptogramin B-type antibiotic resistance phenotypes and susceptible to streptogramin A-type antibiotics. Quinupristin-dalfopristin was as active as vancomycin against three strains that were susceptible to its streptogramin B component quinupristin, including one strain that was inducibly resistant to erythromycin, but had a significantly decreased activity against two strains that were resistant to quinupristin, for all quinupristin-dalfopristin regimens tested (P < 0.05). The area under the concentration-time curve for quinupristin-dalfopristin in plasma divided by the MIC of quinupristin was the only parameter retained by multilinear regression that predicted the in vivo activity of quinupristin-dalfopristin (P = 0.0001), emphasizing the importance of determining the susceptibility to quinupristin in order to predict the in vivo activity of quinupristin-dalfopristin against S. aureus.

[Streptococcus pneumoniae bacteremia and HIV infection. Retrospective study of 41 episodes in 30 patients]

OBJECTIVES

Pulmonary infections and bacteraemia, essentially due to Streptococcus pneumoniae and Haemophilus influenzae, are frequently reported in patients infected with the human immunodeficiency virus (HIV). We retrospectively analyzed episodes of bacteraemia in HIV-infected patients to determine whether supplementary risk factors could be ascertained and whether it would be advisable to propose vaccination.

METHODS

From June 1986 to February 1992, 41 episodes of bacteraemia in 30 HIV-infected patients were observed in 7 different wards. Data on age, sex, risk group, Centers for Disease Control classification, CD4 counts and clinical outcome were recorded.

RESULTS

There were 18 males and 12 females, mean age 34 years (range 26-67 years) in CDC class II (n = 11), III (n = 5) and IV (n = 16). There were 17 intravenous drug users (56.6%). There were 8 heterosexuals (26%), 3 homosexuals or bisexuals (n = 3) and 2 patients infected after blood transfusions (6%). All the heterosexual patients were of black-African or Carabean ethnic origin. Mean CD4 count was 239 mm3 (range 2-1148) during the episode of bacteraemia which occurred during an upper respiratory tract infection in 96% of the patients. Recurrent episodes were observed in 7 patients. Outcome of the infectious episode was favourable in 35/41 cases after antibiotic therapy. Six patients (all CDC class IV) died during the episode of bacteraemia.

CONCLUSIONS

These observations showed that intravenous drug use and black-African ethnic origin are supplementary risk factors for S. pneumoniae infection in HIV-infected patients. The frequency of upper respiratory tract infections in these patients suggests that anti-S. pneumoniae vaccination should be evaluated further.

Influence of antimicrobial therapy on kinetics of tumor necrosis factor levels in experimental endocarditis caused by Klebsiella pneumoniae

The kinetics of tumor necrosis factor (TNF) levels in serum during therapy with cell wall-active agents (ceftriaxone, imipenem) and gentamicin were investigated in rabbits with experimental endocarditis caused by an isogenic pair of Klebsiella pneumoniae strains: a TEM-3 beta-lactamase-producing strain (KpR) or its susceptible variant (KpS). In vitro, KpR was resistant to ceftriaxone and was susceptible to gentamicin and imipenem, while KpS was susceptible to all three antibiotics. Serum TNF levels were determined in control rabbits hourly after bacterial inoculation and then daily; they were determined in treated animals hourly after the first antibiotic injection and then daily during a 4-day therapy with either imipenem (60 mg/kg of body weight four times daily), ceftriaxone (75 mg/kg once daily), or gentamicin (4 mg/kg once daily) alone or in combination with ceftriaxone. After a transient peak (10.2 +/- 3.1 ng/ml) at 90 min following bacterial challenge, serum TNF levels remained low and stable in control animals. The peak in the serum TNF levels occurred 4 h after the first antibiotic injection and with ceftriaxone was significantly higher (P < 0.05) against KpS (1.99 +/- 0.52 ng/ml) than against KpR (1.40 +/- 0.17 ng/ml). Against the KpR strain, the levels observed with ceftriaxone were significantly higher (P < 0.05) than those obtained with the other therapeutic regimens (0.70 to 0.80 ng/ml). On the day of sacrifice, effective regimens were associated with low TNF levels. We concluded that TNF production depends on (i) the antiobiotic's mechanism of action and the susceptibility of the strain at the early phase of therapy, without any effect of the rapidity of bacterial killing, and (ii) the final reduction of the bacterial count at a later stage of therapy.

Conditions for the emergence of resistance to cefpirome and ceftazidime in experimental endocarditis due to Pseudomonas aeruginosa

The conditions for the emergence of resistance to cefpirome and ceftazidime were studied in rabbits with experimental aortic endocarditis due to Pseudomonas aeruginosa. The MIC of cefpirome was 16 mg/L and that of ceftazidime was 4 mg/L. Resistant mutants with MICs of > or = 64 mg/L were obtained in vitro to cefpirome after a single passage and to ceftazidime after five passages. A single dose of 50 mg/kg intramuscularly gave mean peak serum concentrations of 110.0 +/- 31.7 mg/L for cefpirome compared with 67.7 +/- 21.4 mg/L for ceftazidime and the half-lives were 1.2 +/- 0.1 h and 2.1 +/- 0.4 h, respectively. After treating infected rabbits for 4 days with various dosing regimens, resistant strains were only detected in those animals in which the time that the serum concentration exceeded the MIC was less than half of the dosing interval. There was no evidence of emergent resistance when the serum concentrations exceeded the MIC for a longer period nor when amikican was combined with the cephalosporins on the first day of therapy. Moreover, once differences in MICs and pharmacokinetics were taken into account, both antibiotics had a similar propensity to induce resistance.