Grit Ackermann

Comparative Activity of Moxifloxacin in Vitro Against Obligately Anaerobic Bacteria

Abstract The antimicrobial activity of moxifloxacin and seven other antibiotics (four of them quinolones) against 292 strains of obligately anaerobic bacteria was assessed employing a broth microdilution technique performed in Wilkens-Chalgren broth. MIC50/MIC90 values (mg/l) for moxifloxacin were as follows: Bacteroides fragilis (n=62) 0.25/2, Bacteroides ovatus (n=70) 1/4, Bacteroides vulgatus (n=29) 0.25/1, Bacteroides thetaiotaomicron (n=17) 2/2, Bacteroides caccae (n=11) 1/2, Prevotella spp. (n=11) 0.25/2, Fusobacterium spp. (n=17) 1/4, Bilophila wadsworthia (n=29) 0.5/1, and Clostridium spp. (n=29) 0.125/0.5, respectively. MIC50 values (mg/l) for Bacteroides distasonis (n=8) and Peptostreptococcus spp. (n=9) were 0.25. The results indicated that moxifloxacin was almost as active as trovafloxacin, as active as gatifloxacin, and more active than levofloxacin and ciprofloxacin against the anaerobes tested.

Effect of sub-MIC concentrations of metronidazole, vancomycin, clindamycin and linezolid on toxin gene transcription and production in Clostridium difficile

Clostridium difficile is the major cause of hospital-acquired infectious diarrhoea. Several antimicrobials are known to induce and promote C. difficile-associated diarrhoea (CDAD). The impact of metronidazole (MTR), vancomycin (VAN), clindamycin (CLI) and linezolid (LZD) on growth, toxin gene transcription and toxin production in C. difficile was investigated. Four C. difficile strains were grown with and without sub-MIC concentrations of MTR, VAN, CLI and LZD (0.5x MIC) and growth was measured by colony counts. Toxin production was detected using ELISA (for toxin A) and a cytotoxicity assay (for toxin B) in culture supernatants and also in sonicated cells. Real-time PCR was used to measure transcription of the toxin A and B genes. The aim of this work was to combine analysis of toxin A and B production by ELISA or cell culture assay with transcriptomic analysis. The four strains showed similar growth and different levels of toxin production in the absence of antibiotics. An antibiotic-free control showed toxin production at a late stage when the plateau phase of bacterial growth was reached, whereas antibiotic-exposed strains showed earlier toxin production. All of the antibiotics used except CLI increased the transcription rate of toxin genes. The findings of this study show that sub-MIC concentrations of antibiotics can cause changes in gene transcription of the major virulence factors of C. difficile. This study describes a new method for transcriptomic analysis of toxin genes in C. difficile.

OPT-80, a macrocyclic antimicrobial agent for the treatment of Clostridium difficile infections: a review.

Background: Clostridium difficile-associated diarrhoea has become a major problem over the last years. Increasing incidence and more severe clinical cases initiated the search for new treatment options. Objective: OPT-80, also known as tiacumicin B, lipiarmycin or PAR-101, is a macrocyclic antimicrobial with little or no systemic absorption after oral administration and narrow activity spectrum against Gram-positive aerobic and anaerobic bacteria. Methods: Data on OPT-80 available from published studies, presentations at conferences and the manufacturer were collected and reviewed. Results/conclusion: The in vitro studies of OPT-80 and clinical C. difficile strains showed high activity at low concentrations. Safety and efficacy of the drug were found to be favourable. More Phase II and III clinical trials are to be completed.

Prevalence of Enterotoxin Producing Staphylococcus aureus in Stools of Patients with Nosocomial Diarrhea

Background:Nosocomial diarrhea causes prolonged hospital stay leading to additional diagnostic and therapeutic procedures resulting in higher costs. A total of 20%–25% of antibiotic-associated diarrhea (AAD) cases are attributed to Clostridium difficile. Other microorganisms like Clostridium perfringens and Staphylococcus aureus are discussed to be associated with AAD.Patients and Methods:This study evaluated the prevalence of enterotoxigenic S. aureus in stool samples submitted to the laboratory with the diagnosis nosocomial diarrhea. A total of 2,727 stools from clinical patients were investigated for S. aureus and C. difficile. Samples were cultured for both bacteria and a C. difficile toxin A and B assay was performed from all stools. Isolated S. aureus were investigated for enterotoxin production and for resistance against methicillin. In addition, both assays were evaluated for determination of S. aureus enterotoxins directly in stool samples.Results:Out of 2,727 stools investigated, 198 grew S. aureus and 148 C. difficile. Toxins A/B from C. difficile were detected in 184 stools. A total of 114 S. aureus strains produced the following enterotoxins in vitro: A, 36; B, 20; C, 19; D, 68; E, 2. Both pathogens were found in 25 stools. Twenty-nine (14.6%) S. aureus strains were identified as methicillin-resistant. The two toxin assays evaluated in this study were not able to detect S. aureus enterotoxins directly in stools.Conclusion:The role of enterotoxigenic S. aureus in the pathogenesis of nosocomial and AAD needs further consideration. It might be necessary to investigate stool samples from patients with AAD/nosocomial diarrhea for S. aureus on a routine basis.

Infections Caused by Stenotrophomonas maltophilia– A Prospective Study

AbstractBackground:Stenotrophomonas maltophilia is an opportunistic microorganism, often highly resistant to routinely tested antibiotics. This microorganism is isolated in specimens from patients with nosocomial infections with increasing frequency. Patients and Methods: During a 1-year period (1998/1999) S. maltophilia was isolated from 137 specimens (0.26% of all investigated specimens) from 80 patients who were treated in a 1,500 bed major tertiary care teaching hospital in Leipzig. The data of 76 patients (133 specimens) could be collected and analyzed completely. Results: The pathogen was most frequently detected in specimens from the respiratory tract (54%). In five patients (six cases) S. maltophilia was isolated from blood cultures (0.3% of all positive blood cultures; 1.4% of all gram-negative isolates from blood cultures). 70 of the infected patients were inpatients and 32 (42%) of them were treated on the internal medicine wards. Of these 32 patients only six (19%) were pretreated with imipenem. The length of stay at the hospital resulted in an independent increased risk of infection with S. maltophilia. In addition, this organism was detected in six infected outpatients. Conclusion:S. maltophilia is not only a nosocomial pathogen. Pretreatment with a carbapemnem is no longer an unequivocal risk factor for an infection with S. maltophilia.

In vitro activities of fourteen antimicrobial agents against obligately anaerobic bacteria

The in vitro activities of fourteen antimicrobial agents were tested against 292 clinical isolates of obligately anaerobic bacteria using the broth microdilution technique. Taking all strains as a group the MIC(50/90) (mg/l) values were metronidazole and imipenem 0.25/1, meropenem 0.25/0.5, trovafloxacin 0.25/1, gatifloxacin and moxifloxacin 0.5/2, levofloxacin 2/16, ciprofloxacin 4/32, clindamycin 0.5/8, amoxycillin/clavulanate 1/4, doxycycline and chloramphenicol 2/4, erythromycin 4/>32 and penicillin G 16/>32.

Mapping of linear antigenic determinants on glycoprotein C of herpes simplex virus type 1 and type 2 recognized by human serum immunoglobulin G antibodies

Using membrane‐based dekapeptides, the reactivity of human serum antibodies with linear antigenic determinants of herpes simplex virus (HSV) type 1 and type 2 glycoprotein C (gC‐1, gC‐2) was studied by pep scan and immunodot assay. The entire coding sequences of gC‐1 and gC‐2 were screened for the presence of linear epitopes by pep scan. Peptides recognized in an HSV‐1 type‐specific manner were mainly identified within the N‐terminal third and at the C‐terminus of gC‐1, whereas most type‐common antibodies were directed against colinear peptides within the central parts of gC‐1 and gC‐2. The type‐specific reaction of human sera with gC‐2 peptides in pep scan was poor. Eight peptides identified as immunoreactive by pep scan were further tested in immunodot assay for their reactivity with a human serum panel. None of the eight HSV‐negative sera gave positive results by immunodot assay. Positive reactions with gC peptides were found to be strongly age‐dependent, i.e., the rate of positive reactions was significantly higher in HSV‐positive adults than in HSV‐positive children. Antibody reactivity with two type‐common gC peptides was demonstrated in 17 out of 28 HSV‐positive sera. A putative type‐specific gC‐2 peptide employed in immunodot assay was inconsistently recognized by human sera. Twenty HSV‐positive sera reacted with at least 1 of 5 type‐specific gC‐1 peptides. Nine sera showing no reactivity with glycoprotein G of HSV‐1 (gG‐1) by immunoblotting recognized type‐specific gC‐1 peptides in immunodot assay. Thus, gC‐1 peptides might allow the detection of HSV‐1‐specific antibodies in individuals showing no reactivity with commonly employed HSV‐1‐specific diagnostic antigens, i.e., purified or recombinant gG‐1. J. Med. Virol. 55:281–287, 1998.

Prevalence of the ermB Gene in Clostridium difficile Strains Isolated at a University Teaching Hospital from 1987 through 1998

We analyzed 226 strains of Clostridium difficile for the presence of erythromycin ribosomal methylase B (ermB) genes. Forty-four strains (19.4%) carried ermB genes and were resistant to erythromycin. Toxin A and toxin B gene sequences were identified in 81.9% of these 44 strains. Strains of C. difficile that carry ermB genes are common etiologic agents of C. difficile-associated diarrhea.

Therapeutic efficacy of moxifloxacin in a murine model of severe systemic mixed infection with Escherichia coli and Bacteroides fragilis.

The therapeutic efficacy of moxifloxacin was studied in an experimental murine model of a systemic aerobic/anaerobic mixed infection and compared to therapies with either imipenem or ciprofloxacin plus metronidazole. Groups of 20 mice each were intravenously (iv) infected with approximately 2.5 x 10(6) colony forming units (CFU) of Escherichia coli and 2 x 10(7)CFU of Bacteroides fragilis. Iv therapy was started 24 h post-infection (pi) with either moxifloxacin, imipenem, or ciprofloxacin plus metronidazole, for 3 days. A control group of 20 mice was left untreated. Survival rate at day seven pi was recorded, mice were then sacrificed and bacterial organ contents of livers and kidneys were determined. All mice treated survived at day seven, while six animals of the untreated group died. B. fragilis was not detected in any of the treated mice. E. coli was found in two of the moxifloxacin-treated mice and in two and five of the ciprofloxacin plus metronidazole and imipenem-treated animals, respectively. The results indicate that a therapy of severe mixed aerobic/anaerobic infections with moxifloxacin might be feasible and possibly be as efficacious as current therapy regimens with ciprofloxacin plus metronidazole or imipenem.

Rapidly Growing Tumor-Like Brain Lesion

Listeria monocytogenes accounts for 8–11% of the casers of bacterial meningitis which is associated with high mortality in patients with serious underlying diseases or those receiving immunosuppressive treatment. Brain abscess due to L. monocytogenes is a very rare occurrence. The case reported here concerns a 54-year-old female patient with a rapidly growing tumor-like brain lesion. L. monocytogenes type 4b could be cultured from blood and brain biopsy. Despite antimicrobial therapy with ampicillin and gentamicin, the patient died 11 days after admission to the hospital. The growing numbers of elderly and immunocompromised patients will increasingly confront physicians with patients with listeriosis. Delayed therapy in patients treated with corticosteroids may result in a fatal outcome.