In vitro Antimicrobial Activity of Gatifloxacin Compared with Other Quinolones against Clinical Isolates from Cancer Patients

In Vitro Selective Combinatory Effect of Ciprofloxacin with Nitroxoline, Sanguinarine, and Zinc Pyrithione against Diarrhea-Causing and Gut Beneficial Bacteria

Antibiotic resistance in diarrhea-causing bacteria and its disruption of gut microbiota composition are health problems worldwide. The development of combinatory agents that increase the selective inhibitory effect (synergism) against diarrheagenic pathogens and, simultaneously, have a lowered impact (antagonism) or no negative action on the gut microbiota is therefore proposed as a new strategy efficient for chemotherapy against diarrheal conditions. In this study, the in vitro selective combinatory effect of ciprofloxacin with nitroxoline, sanguinarine, and zinc pyrithione, representing various classes of alkaloid-related compounds (nitroquinolines, benzylisoquinolines and metal-pyridine derivative complexes) against selected standard diarrhea-causing (Bacillus cereus, Enterococcus faecalis, Listeria monocytogenes, Shigella flexneri, and Vibrio parahaemolyticus) and gut-beneficial (Bifidobacterium adolescentis, Bifidobacterium animalis subsp. lactis, Bifidobacterium breve, Lactobacillus casei, and Lactobacillus rhamnosus) bacteria, was evaluated according to the sum of fractional inhibitory concentration indices (FICIs) obtained by the checkerboard method. The results showed that the individual combination of ciprofloxacin with nitroxoline, sanguinarine, and zinc pyrithione produced a synergistic effect against the pathogenic bacteria, with FICI values ranging from 0.071 to 0.5, whereas their antagonistic interaction toward the Bifidobacterium strains (with FICI values ranging from 4.012 to 8.023) was observed. Ciprofloxacin-zinc pyrithione produced significant synergistic action against S. flexneri, whereas a strong antagonistic interaction was observed toward B. breve for the ciprofloxacin-nitroxoline combination. These findings suggest that certain combinations of agents tested in this study can be used for the development of antidiarrheal therapeutic agents with reduced harmful action on the gastrointestinal microbiome. However, further studies focused on their pharmacological efficacy and safety are needed before they are considered for clinical trials. IMPORTANCE Diarrheal infections, which are commonly treated by antibiotics, are still responsible for over 4 to 5 million cases of human deaths annually. Moreover, the rising incidence of antibiotic resistance and its negative effect on beneficial bacteria (e.g., Bifidobacteria) of the gut microbial community are another problem. Thus, the development of selective agents able to inhibit diarrheal bacteria and, simultaneously, that have no negative impact on the gut microbiota, is important. Our results showed that individual combinations of ciprofloxacin with nitroxoline, sanguinarine, and zinc pyrithione produced synergism against the pathogenic bacteria, whereas their antagonistic interaction toward the beneficial strains was observed. The antagonism can be considered a positive effect contributing to the safety of the therapeutic agents, whereas their synergism against diarrheal bacteria significantly potentiates total antimicrobial efficacy. The certain combinations tested in this study can be used for the development of antidiarrheal agents with reduced harmful action on the gastrointestinal microbiome.

Pangenomic and functional investigations for dormancy and biodegradation features of an organic pollutant-degrading bacterium Rhodococcus biphenylivorans TG9

Environmental bacteria contain a wealth of untapped potential in the form of biodegradative genes. Leveraging this potential can often be confounded by a lack of understanding of fundamental survival strategies, like dormancy, for environmental stress. Investigating bacterial dormancy-to-degradation relationships enables improvement of bioremediation. Here, we couple genomic and functional assessment to provide context for key attributes of the organic pollutant-degrading strain Rhodococcus biphenylivorans TG9. Whole genome sequencing, pangenome analysis and functional characterization were performed to elucidate important genes and gene products, including antimicrobial resistance, dormancy, and degradation. Rhodococcus as a genus has strong potential for degradation and dormancy, which we demonstrate using R. biphenylivorans TG9 as a model. We identified four Resuscitation-promoting factor (Rpf) encoding genes in TG9 involved in dormancy and resuscitation. We demonstrate that R. biphenylivorans TG9 grows on fourteen typical organic pollutants, and exhibits a robust ability to degrade biphenyl and several congeners of polychlorinated biphenyls. We further induced TG9 into a dormant state and demonstrated pronounced differences in morphology and activity. Together, these results expand our understanding of the genus Rhodococcus and the relationship between dormancy and biodegradation in the presence of environmental stressors.

Chryseobacterium/Elizabethkingia species infections in Saudi Arabia

Objectives:

To describe the epidemiological, clinical, and outcome data of patients infected or colonized with Chryseobacterium/Elizabethkingia spp including antibiotic susceptibility patterns.

Methods:

This retrospective study was conducted at Prince Sultan Military Medical City, Riyadh, Saudi Arabia. All patients infected or colonized by Chryseobacterium /Elizabethkingia spp who were admitted between June 2013 and May 2019 were included. Data were extracted from patient electronic medical records.

Results:

We enrolled 27 patients (13 males and 14 females) with a mean age of 35.6 years. Chryseobacterium/Elizabethkingia spp were isolated from blood cultures (n=13, 48%) and tracheal aspirations (n=11, 41%). The most frequent species isolated was Elizabethkingia meningoseptica (n=22). Although 6 patients were considered colonized, the remaining 21 patients presented with ventilator associated pneumonia (n=9), central line associated bloodstream infection (n=4), septic shock (n=4), or isolated bacteremia (n=4). In 25 cases the infections were health-care related. Three patients (11%) died within 28 days. Twenty-six isolates (96.5%) were resistant to carbapenems. Moxifloxacin and cotrimoxazole were the most active antibiotics.

Conclusion:

Chryseobacterium/Elizabethkingia spp infection is rare, but can be responsible for severe hospital acquired infections. Cotrimoxazole and fluoroquinolone are the most effective antibiotic treatments.

Relationships among ciprofloxacin, gatifloxacin, levofloxacin, and norfloxacin MICs for fluoroquinolone-resistant Escherichia coli clinical isolates

Fluoroquinolones are some of the most prescribed antibiotics in the United States. Previously, we and others showed that the fluoroquinolones exhibit a class effect with regard to the CLSI-established breakpoints for resistance, such that decreased susceptibility (i.e., an increased MIC) to one fluoroquinolone means a simultaneously decreased susceptibility to all. For defined strains, however, clear differences exist in the pharmacodynamic properties of each fluoroquinolone and the extent to which resistance-associated genotypes affect the MICs of each fluoroquinolone. In a pilot study of 920 clinical Escherichia coli isolates, we uncovered tremendous variation in norfloxacin MICs. The MICs for all of the fluoroquinolone-resistant isolates exceeded the resistance breakpoint, reaching 1,000 microg/ml. Approximately 25% of the isolates (n = 214), representing the full range of resistant norfloxacin MICs, were selected for the simultaneous determinations of ciprofloxacin, gatifloxacin, levofloxacin, and norfloxacin MICs. We found that (i) great MIC variation existed for all four fluoroquinolones, (ii) the ciprofloxacin and levofloxacin MICs of >90% of the fluoroquinolone-resistant isolates were higher than the resistance breakpoints, (iii) ciprofloxacin and levofloxacin MICs were distributed into two distinct groups, (iv) the MICs of two drug pairs (ciprofloxacin and norfloxacin by Kendall's Tau-b test and gatifloxacin and levofloxacin by paired t test) were similar with statistical significance but were different from each other, and (v) approximately 2% of isolates had unprecedented fluoroquinolone MIC relationships. Thus, although the fluoroquinolones can be considered equivalent with regard to clinical susceptibility or resistance, fluoroquinolone MICs differ dramatically for fluoroquinolone-resistant clinical isolates, likely because of differences in drug structure.

Therapeutic options for Stenotrophomonas maltophilia infections beyond co-trimoxazole: a systematic review

BACKGROUND

Stenotrophomonas maltophilia has emerged as an important opportunistic pathogen, causing infections whose management is often problematic due to its inherent resistance to many antibiotics, making co-trimoxazole the main therapeutic option. However, there are cases in which either due to antimicrobial resistance or allergic reactions and intolerance to co-trimoxazole this antibiotic cannot be administered. We sought to evaluate the available clinical evidence regarding potentially effective alternative antibiotics for the treatment of S. maltophilia infections.

METHODS

The literature search was performed in the PubMed and Scopus databases. The search string used was 'Stenotrophomonas maltophilia OR Xanthomonas maltophilia'.

RESULTS

Thirty-one case reports and 5 case series were retrieved including a total of 49 patients with a variety of infections. Twenty of 49 cases (40.8%) were treated with ciprofloxacin as monotherapy or in combination with other antibiotics; 12 of 49 cases (24.5%) were treated with ceftriaxone- or ceftazidime-based regimens; and 6 of 49 cases (12.2%) were treated with ticarcillin- or ticarcillin/clavulanate-based regimens. The cure or improvement rates were 18 cases (90%), 8 (75%) and 4 (66.7%), respectively. The remaining 11 patients received various antimicrobials including aminoglycoside-based regimens, carbapenems, levofloxacin, chloramphenicol, aztreonam, minocycline and other beta-lactams.

CONCLUSIONS

The limited available data suggest that ciprofloxacin, ceftazidime or ceftriaxone, and ticarcillin/clavulanate, alone or in combination with other antibiotics, may be considered as alternative options beyond co-trimoxazole.

Microbial spectrum and antibiotic susceptibility profile of gram-positive aerobic bacteria isolated from cancer patients

PURPOSE

Cancer patients are particularly susceptible to nosocomial infections because of their compromised immune system, and because of the nature of treatment practices they experience. Recently, a shift of the microbial spectrum of cancer patients from gram-negative to gram-positive has been demonstrated. This study analyzed the distribution and the antimicrobial resistance of gram-positive bacteria isolated from cancer patients in Egypt.

PATIENTS AND METHODS

We examined the microbial spectrum of gram-positive bacteria in patients with hematologic malignancies and solid tumors. In addition, we also studied the antimicrobial resistance of pathogens accounting for the majority of gram-positive infections in these cancer patients.

RESULTS

Most of gram-positive isolates from urinary tract (100%), respiratory tract (89.7%), and bloodstream infections (BSIs; 65.5%) were obtained from leukemic patients. All gram-positive isolates from skin infections were isolated from solid-tumor patients. In both leukemic and solid-tumor patients, gram-positive bacteria causing nosocomial BSI were mainly Coagulase-negative staphylococcus (CNS) and S. aureus, whereas gram-positive bacteria causing nosocomial RTI were mainly alpha-hemolytic streptococci and CNS. Gram-positive bacteria were not isolated from GI tract infections. S. aureus, CNS, and alpha-hemolytic streptococci demonstrated methicillin resistance (81.5%, 92.3%, and 90% resistance, respectively). S. aureus and CNS were susceptible to linezolid (15.4% and 0% resistance, respectively), and vancomycin (15.5% and 11% resistance, respectively).

CONCLUSION

This is the first study to report the emergence of vancomycin- and linezolid-resistant S. aureus in Egypt. Newer generation quinolones (moxifloxacin and gatifloxacin) were more active than older quinolones (ciprofloxacin and ofloxacin) against S. aureus and CNS, suggesting the use of newer generation quinolones in the prophylaxis of cancer patients.

Stenotrophomonas maltophilia pneumonia in cancer patients without traditional risk factors for infection, 1997–2004

In order to elucidate the spectrum of Stenotrophomonas maltophilia pneumonia in cancer patients without traditional risk factors, 44 cancer patients (cases) with S. maltophilia pneumonia in whom S. maltophilia pneumonia risk factors were not present were compared with two S. maltophilia pneumonia risk groups (controls) including 43 neutropenic non-intensive care unit (ICU) and 21 non-neutropenic ICU patients. The case and control patients had similar demographic and underlying clinical characteristics. Compared with case patients with S. maltophilia pneumonia, neutropenic patients had higher exposure to carbapenem antibiotics (58 vs. 41%; p < 0.03), more frequent hematologic malignancy (95 vs. 64%; p < 0.0003), and they presented with concurrent bacteremia more often (23 vs. 0%; p < 0.0005). Patients with S. maltophilia pneumonia in the ICU needed vasopressor therapy more frequently than cases (62 vs. 5%; p < 0.0001). Hospital-acquired S. maltophilia pneumonia was more common among controls than cases (98 vs. 61%; p < 0.000002). Among the cases, 15 (34%) received outpatient oral antimicrobial therapy, while 29 were hospitalized and eight (28%) were subsequently admitted to the ICU. The mean duration of ICU stay, even among these eight patients (19 +/- 40 days), was comparable to that of patients with neutropenia (23 +/- 26 days) and those who developed S. maltophilia pneumonia during their ICU stay (34 +/- 22 days; p = 0.46). The overall infection-associated mortality in the 108 patients with S. maltophilia pneumonia was 25%. Twenty percent of patients without traditional risk factors for S. maltophilia pneumonia died due to progressive infection. In a multivariate logistic regression analysis, only admission to the ICU predicted death (odds ratio 33; 95% confidence interval, 4.51-241.2; p < 0.0006). The results of this study indicate S. maltophilia pneumonia is a serious infection even in non-neutropenic, non-ICU patients with cancer.

The spectrum of Gram-positive bloodstream infections in patients with hematologic malignancies, and the in vitro activity of various quinolones against Gram-positive bacteria isolated from cancer patients

OBJECTIVES

To determine the current spectrum of Gram-positive bloodstream infections (BSI) in patients with hematologic malignancies at our institution, and to determine the in vitro activity of various fluoroquinolones against clinical Gram-positive isolates collected from such patients.

METHODS

Institutional microbiology records from 493 consecutive episodes of Gram-positive BSI were reviewed. The in vitro activity of six fluoroquinolones against 477 clinical isolates was determined using an NCCLS approved, broth-dilution method.

RESULTS

The most common Gram-positive organisms isolated from the bloodstream of patients with hematological malignancies were coagulase-negative staphylococci (33%), Staphylococcus aureus (15%), viridans group streptococci (10%), and the enterococci (8%). Acute leukemias were the most common underlying malignancies, and 73% of patients were neutropenic when they developed their BSI. The newer generation quinolones--moxifloxacin and gatifloxacin--had the best overall in vitro activity against the Gram-positive isolates tested, and were at least 2 to 8-fold more potent than the early generation quinolones (ofloxacin and ciprofloxacin). Of the 477 isolates tested, 405 (85%) were from patients receiving quinolone (ciprofloxacin or levofloxacin) prophylaxis.

CONCLUSIONS

In patients with hematologic malignancies, Gram-positive BSI are caused by a large number of bacterial species and many occur despite antimicrobial prophylaxis. The newer generation quinolones--moxifloxacin and gatifloxacin--have better in vitro activity against these organisms than early generation agents (ciprofloxacin and ofloxacin).

Once daily, oral, outpatient quinolone monotherapy for low-risk cancer patients with fever and neutropenia

BACKGROUND

The objective of this study was to assess the feasibility of empiric, oral, outpatient quinolone monotherapy in 40 adult patients with fever and neutropenia who were at low risk for serious medical complications.

METHODS

Patients with breast cancer or sarcoma who presented with fever and neutropenia and were identified as low risk received empiric, oral, quinolone monotherapy (gatifloxacin at a dose of 400 mg once daily). Patients who had a significant source/focus of infection on presentation were excluded. After an initial observation period of 4 to 8 hours in the emergency center, the remainder of their management was ambulatory. Patients were evaluated for response to therapy, development of complications and/or the need for hospital admission, and drug-related adverse events.

RESULTS

Three of 43 patients studied were ineligible medically because of the presence of Common Toxicity Criteria (version 3.0) Grade>2 mucositis. Of the 40 eligible patients, 38 patients (95%) responded to gatifloxacin monotherapy, although 1 patient requested hospital admission (92% response for ambulatory management). The mean duration of therapy was 7 days, and the median number of days from enrollment to defervescence was 4 days. There were no serious medical complications, no drug-related adverse events, and no deaths on study or during 30 days of follow-up.

CONCLUSIONS

The results from this study indicated that outpatient quinolone monotherapy in low-risk febrile neutropenic patients is safe, effective, and well received. These conclusions need to be validated in a randomized trial.