Triple Antibiotic Combinations Research Articles

Comparative Evaluation of Antimicrobial Efficacy of Triple Antibiotic Paste Herbal Combination and Camphorated Monochlorophenol as Intracanal Medicaments against Enterococcus faecalis in Deciduous Molars: An In Vivo Study

Comparative Evaluation of Antimicrobial Efficacy of Triple Antibiotic Paste Herbal Combination and Camphorated Monochlorophenol as Intracanal Medicaments against Enterococcus faecalis in Deciduous Molars: An In Vivo Study

Causative microbes and antibiotic susceptibility of acute appendicitis in adults and children

In recent years, some studies have found that acute uncomplicated appendicitis can be treated with antibiotics alone. Because of the lack of relevant research on treating acute appendicitis in Taiwan, this study investigated the microbiological characteristics of acute appendicitis to permit accurate empirical antibiotic use for uncomplicated appendicitis. In this single-center retrospective cohort study, patients listed in the Taiwan National Health Insurance Research Database with a discharge diagnosis of acute appendicitis were identified. Data for bacterial specimens and antibiotic susceptibility tests among patients treated at Tri-Service General Hospital between January 2016 and December 2021 were analyzed. Among 2805 patients diagnosed with acute appendicitis, 167 (6%) were <18 years old. The culture positivity rates among children and adults were 33% and 18%, respectively. In total, 367 aerobes and 207 anaerobes were isolated. The predominant aerobic gram-positive coccus was viridans group streptococci (8.9%), the most common aerobic gram-negative bacillus was Escherichia coli (27.9%), and the most common anaerobic microorganism was Bacteroides spp. (27.7%). The results of antibiotic susceptibility testing of the predominant microorganisms revealed that 86.3% of gram-positive aerobes were susceptible to ampicillin, 76.3% of gram-negative aerobes were susceptible to gentamicin, and all anaerobic isolates were susceptible to metronidazole. Triple first-line antibiotic combination therapy, including ampicillin, gentamicin, and metronidazole, remains highly effective against the pathogens that cause acute appendicitis.

Metabolomics revealed mechanism for the synergistic effect of sulbactam, polymyxin-B and amikacin combination against Acinetobacter baumannii.

The emergence of multidrug-resistant (MDR) Acinetobacter baumannii prompts clinicians to consider treating these infections with polymyxin combination. Metabolomic analysis was applied to investigate the synergistic effects of polymyxin-B, amikacin and sulbactam combination therapy against MDR A. baumannii harboring OXA-23 and other drug resistant genes. The drug concentrations tested were based on their clinical breakpoints: polymyxin-B (2 mg/L), amikacin (16 mg/L), polymyxin-B/amikacin (2/16 mg/L), and polymyxin-B/amikacin/sulbactam (2/16/4 mg/L). The triple antibiotic combination significantly disrupted levels of metabolites involved in cell outer membrane structure including fatty acids, glycerophospholipids, nucleotides, amino acids and peptides as early as 15 min after administration. Amikacin and polymyxin-B alone perturbed a large number of metabolites at 15 min and 1 h, respectively, but the changes in metabolites were short-lived lasting for less than 4 h. In contrast, the combination treatment disrupted a large amount of metabolites beyond 4 h. Compared to the double-combination, the addition of sulbactam to polymyxin-B/amikacin combination produce a greater disorder in A. baumannii metabolome that further confer susceptibility of bacteria to the antibiotics. The metabolomic analysis identified mechanisms responsible for the synergistic activities of polymyxin-B/amikacin/sulbactam against MDR A. baumannii.

Effects of amikacin, polymyxin-B, and sulbactam combination on the pharmacodynamic indices of mutant selection against multi-drug resistant Acinetobacter baumannii.

Amikacin and polymyxins as monotherapies are ineffective against multidrug-resistant Acinetobacter baumannii at the clinical dose. When polymyxins, aminoglycosides, and sulbactam are co-administered, the combinations exhibit in vitro synergistic activities. The minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) were determined in 11 and 5 clinical resistant isolates of A. baumannii harboring OXA-23, respectively, in order to derive the fraction of time over the 24-h wherein the free drug concentration was within the mutant selection window (fTMSW) and the fraction of time that the free drug concentration was above the MPC (fT>MPC) from simulated pharmacokinetic profiles. The combination of these three antibiotics can confer susceptibility in multi-drug resistant A. baumannii and reduce the opportunity for bacteria to develop further resistance. Clinical intravenous dosing regimens of amikacin, polymyxin-B, and sulbactam were predicted to optimize fTMSW and fT>MPC from drug exposures in the blood. Mean fT>MPC were ≥ 60% and ≥ 80% for amikacin and polymyxin-B, whereas mean fTMSW was reduced to <30% and <15%, respectively, in the triple antibiotic combination. Due to the low free drug concentration of amikacin and polymyxin-B simulated in the epithelial lining fluid, the two predicted pharmacodynamic parameters in the lung after intravenous administration were not optimal even in the combination therapy setting.

Metabolomic profiling of polymyxin-B in combination with meropenem and sulbactam against multi-drug resistant Acinetobacter baumannii.

Empirical therapies using polymyxins combined with other antibiotics are recommended in the treatment of Acinetobacter baumannii infections. In the present study, the synergistic activities of polymyxin-B, meropenem, and sulbactam as combination therapy were investigated using metabolomic analysis. The metabolome of A. baumannii was investigated after treatment with polymyxin-B alone (2 mg/l), meropenem (2 mg/l) alone, combination of polymyxin-B/meropenem at their clinical breakpoints, and triple-antibiotic combination of polymyxin-B/meropenem and 4 mg/l sulbactam. The triple-antibiotic combination significantly changed the metabolite levels involved in cell outer membrane and cell wall biosynthesis, including fatty acid, glycerophospholipid, lipopolysaccharide, peptidoglycan, and nucleotide within 15 min of administration. In contrast, significant changes in metabolome were observed after 1 h in sample treated with either meropenem or polymyxin-B alone. After 1 h of administration, the double and triple combination therapies significantly disrupted nucleotide and amino acid biosynthesis pathways as well as the central carbon metabolism, including pentose phosphate and glycolysis/gluconeogenesis pathways, and tricarboxylic acid cycle. The addition of sulbactam to polymyxin-B and meropenem combination appeared to be an early disruptor of A. baumannii metabolome, which paves the way for further antibiotic penetration into bacteria cells. Combination antibiotics consisting of sulbactam/meropenem/polymyxin-B can effectively confer susceptibility to A. baumannii harboring OXA-23 and other drug resistant genes. Metabolomic profiling reveals underlying mechanisms of synergistic effects of polymyxin-B combined with meropenem and sulbactam against multi-drug resistant A. baumannii.

SPR741, Double- or Triple-Combined With Erythromycin and Clarithromycin, Combats Drug-Resistant Klebsiella pneumoniae, Its Biofilms, and Persister Cells.

Klebsiella pneumoniae has emerged as a major clinical and public health threat owing to the increasing prevalence of healthcare-associated infections caused by multidrug-resistant or extensively drug-resistant strains. However, increasing antibiotic resistance and the absence of clinically effective antimicrobial agents make combination therapy an urgent need. This study investigated the anti-microbial activity of SPR741, a polymyxin B derivative, in combination with macrolide antibiotics (erythromycin and clarithromycin), against extensively drug-resistant and pandrug-resistant K. pneumoniae. Monotherapy, double, and triple combination therapies were performed to identify the most effective treatment combination using in vitro checkerboard, time-killing kinetics. Furthermore, we evaluated the biofilm eradication and persister cell-killing activity of these combinations using laser confocal microscopy and colony forming unit counting. In addition, a neutropenic mouse thigh infection model was used to assess the therapeutic efficacy and toxicity of the triple antibiotic combination against pandrug-resistant K. pneumoniae in vivo. Our results suggested that SPR741 combined with macrolides exhibited strong synergistic antibacterial activity against extensively drug-resistant and pandrug-resistant K. pneumoniae. These antibiotic combinations could also effectively eradicate highly resistant bacterial biofilms and persister cells in vitro and demonstrate considerable efficacy and low toxicity in vivo. In summary, our findings indicated that SPR741, in combination with macrolide antibiotics (double or triple combination), has the potential to serve as a novel treatment option against drug-resistant K. pneumoniae -related infections.

Evaluation of antimicrobial action and push-out bond strength and compressive strength using mineral trioxide aggregate and triple antibiotic medicament combination as root-end filling material: A novel in vitro study

Evaluation of antimicrobial action and push-out bond strength and compressive strength using mineral trioxide aggregate and triple antibiotic medicament combination as root-end filling material: A novel in vitro study

1458. Uncharted territories: applying “precision medicine” to understand the treacherous landscape of extensively and multidrug resistant (XDR and MDR) Pseudomonas aeruginosa in a patient with cystic fibrosis and lung transplantation

Background Pseudomonas aeruginosa is a persistent and difficult-to-treat pathogen in many patients, especially those with cystic fibrosis (CF). Herein, we describe our experience managing a young woman suffering from CF with XDR P. aeruginosa who underwent lung transplantation. We highlight the contemporary difficulties reconciling the clinical, microbiological, and genetic information.MethodsMechanism-based-susceptibility disk diffusion synergy testing with double and triple antibiotic combinations aided in choosing tailored antimicrobial combinations to control the infection in the pre-transplant period, create an effective perioperative prophylaxis regimen, and manage recurrent infections in the post-transplant period. Thirty-six sequential XDR and PDR P. aeruginosa isolates obtained from the patient within a 17-month period, before and after a double-lung transplant were analyzed by whole genome sequencing (WGS) and RNAseq in order to understand the genetic basis of the observed resistance phenotypes, establish the genomic population diversity, and define the nature of sequence changes over timeResultsOur phylogenetic reconstruction demonstrates that these isolates represent a genotypically and phenotypically heterogeneous population. The pattern of mutation accumulation and variation of gene expression suggests that a group of closely related strains was present in the patient prior to transplantation and continued to evolve throughout the course of treatment regardless of antibiotic usage.Our findings challenge antimicrobial stewardship programs that assist with the selection and duration of antibiotic regimens in critically ill and immunocompromised patients based on single-isolate laboratory-derived resistant profiles. We propose that an approach sampling the population of pathogens present in a clinical sample instead of single colonies be applied instead when dealing with XDR P. aeruginosa, especially in patients with CF.ConclusionIn complex cases such as this, real-time combination testing and genomic/transcriptomic data could lead to the application of true “precision medicine” by helping clinicians choose the combination antimicrobial therapy most likely to be successful against a population of MDR pathogens present.Disclosures Federico Perez, MD, MS, Accelerate (Research Grant or Support)Merck (Research Grant or Support)Pfizer (Research Grant or Support) Robert A. Bonomo, MD, Entasis, Merck, Venatorx (Research Grant or Support)

Antimicrobial Efficacy of Calcium Hydroxide and Triple Antibiotic Paste Combination on E. faecalis Biofilm- an In vitro Study

Calcium hydroxide (CH) is an intracanal medicament that has been widely used in endodontics, which can eliminate bacteria because of its high alkalinity. However, E. faecalis is resistant to CH. Triple antibiotic paste (TAP) is a mixture of ciprofloxacin, minocycline, and metronidazole, and is highly effective against E. faecalis. Hence the main aim of this study was to find the antimicrobial efficacy of CH and TAP combination against E. faecalis. The study was done by agar diffusion method, three wells were punched in Tryptone soya agar and filled with CH, TAP, and the combination of both. The zone of inhibition values was recorded and subjected to statistical analysis using SPSS. One way ANOVA and Post Hoc tests were used to compare the means. The combination of CH with TAP was found to be significantly better than CH and TAP used alone (p-value &lt;0.05).Within the limits of this study, it can be concluded that TAP is more efficient when compared with CH,The combination of CH and TAP proved to be more effective when compared to the two when used alone.

An alternative combination therapy with metronidazole, clindamycin and doxycycline for Babesia gibsoni (Asian genotype) in dogs in Hong Kong.

Babesia spp. are globally distributed hemoparasites that cause disease in many mammalian species. The species Babesia gibsoni (Asian genotype) is prevalent and endemic in many Asian countries but has also been reported in growing numbers in countries outside of Asia. Standard therapies for the treatment of B. gibsoni often fail to result in consistent and successful clearance of the organism. This study evaluated the use of a combination of three antibiotics: metronidazole, clindamycin and doxycycline after atovaquone and azithromycin failed to eliminate the infection on a polymerase chain reaction (PCR) test. The aim of this study was to determine whether the triple antibiotic combination was an appropriate alternative or additional treatment for the elimination of B. gibsoni. The medical records of 24 patients treated from December 2012 to July 2015 were retrospectively analyzed. The diagnosis of B. gibsoni was confirmed with a PCR test that was also used to assess treatment response. All patients were initially treated with the standard therapy, atovaquone and azithromycin with a 25% success rate clearing B. gibsoni. Dogs that remained positive on PCR using the standard therapy were then treated with the triple antibiotic protocol achieving an 87% success rate. The inclusion of an alternative and potentially effective protocol for the treatment of B. gibsoni would increase the options for the current therapeutic options, could aid in clearance of the organism and offer a more affordable option for clients.

A PROSPECTIVE STUDY ON DRUG UTILIZATION IN OBSTETRIC PROCEDURES WITH EMPHASIS ON ANTIBIOTIC USAGE AT A TERTIARY CARE HOSPITAL

Background: Antibiotics are largely prescribed drugs in all major surgical procedures due to high prevalence of infections that has been increase in expenditure and increases antibacterial resistance. Drug utilization studies help to identify and overcome the misuse of antibacterial in prescribing pattern. Hence, the aim of this study was to evaluate the antibiotics utilization patterns in obstetric procedures.&#x0D; Methods: It is a prospective observational study carried out in department of obstetrics and gynecology, of a multi-specialty teaching hospital (Haryana) after obtaining permission from the IEC. The prescriptions were assessed for patient’s demographic data, antimicrobial preference, dose, duration, and route of administration. Categorization of drugs according to Food and Drug Administration (FDA), and rationality score as per the World Health Organization (WHO).&#x0D; Results: During six month study period 120 patients were included into study. The mean age of women undergoing C-section procedure was 27.79±2.78 years. The maximum (90.83%) length of hospital stay was 2 week by women under C-section procedure. The single antibiotic therapy (ceftriaxone - 53.33%) was the most commonly prescribed antibiotic as prophylaxis but in post- operative prescription orders, triple antibiotic combination therapy (ceftriaxone, metronidazole with gentamycin) was maximum (62.50%) prescribed antibiotic. Parenteral route (96.09% in pre-operative and 59.40% in post-operative) was most common route for antibiotic administration. Out of 2216 drugs, branded drugs were 1893 (85.42%) and generic drugs were 323 (14.58%).&#x0D; Conclusion: The present study facilitates the rational use of ceftriaxone as prophylaxis in C-section and triple antibiotic combination therapy as post-operative by the gynaecologists. These antibiotics are most effective without any adverse effect on mother and fetus when use in recommended dose and frequency during obstetric procedures.&#x0D; Keywords: Antibiotics, Caesarean section delivery, Drug utilization study

An exploratory pilot study evaluating the supplementation of standard antibiotic therapy with probiotic lactobacilli in south African women with bacterial vaginosis

BackgroundTo reduce acquisition and relapse of bacterial vaginosis (BV), lactobacilli must be maintained in the vaginal microbiome. Probiotic lactobacilli may aid this purpose. We investigated whether vaginal probiotics (containing Lactobacillus rhamnosus DSM 14870 and Lactobacillus gasseri DSM 14869) would result in vaginal colonisation with lactobacilli in women with and without BV.MethodsThis prospective, partially randomised, exploratory pilot study was conducted in Soweto, South Africa. Thirty-nine sexually-active, HIV negative women were enrolled from October 2014 to May 2016 into three arms. Women who did not have BV (Group 1, n = 13) self-administered probiotic capsules vaginally once daily for 30 days, then once a week until Day 190. Women diagnosed with BV were randomized into Group 2 (n = 12) or Group 3 (n = 14) and treated with the triple oral antibiotic combination for vaginal discharge syndrome per South African guidelines (cefixime 400 mg stat, doxycycline 100 mg BD for 7 days and metronidazole 2 g stat). Immediately after antibiotic treatment, women in Group 2 self-administered probiotic capsules vaginally once daily for 30 days then vaginally once a week until Day 190. Women in Group 3 were not given lactobacilli.ResultsDuring the study, L. rhamnosus DSM 14870 or L. gasseri DSM 14869, were isolated in 5/13 (38.5%) women in Group 1 compared to 10/12 (83.3%) women in Group 2 (p = 0.041). The 1-month and 6-month BV cure rates were similar (P > 0.05) between Group 2 (42 and 25%) compared to Group 3 (36 and 25%). In Group 2, no correlation was observed between the frequency of isolation of the two Lactobacillus strains and the 1-month or 6-month cure rate.ConclusionsSupplementation with vaginal probiotic capsules resulted in colonisation of the vagina by the Lactobacillus strains (L. rhamnosus DSM 14870 and L. gasseri DSM 14869) contained in the capsules. We observed low initial cure rates of BV after a stat dose of metronidazole and that the probiotic did not improve BV cure rates or alleviate recurrence which could be due to treatment failure or very limited power of the study.Trial registrationRegistered at the Pan African Clinical Trial Registry (www.pactr.org) on April 13, 2018 (retrospectively registered). Trial identification number: PACTR201804003327269.

Discussion: The Questionable Role of Antibiotic Irrigation in Breast Augmentation

Discussion: The Questionable Role of Antibiotic Irrigation in Breast Augmentation

Comparative Evaluation of Mixture of Calcium Hydroxide and Chlorhexidine, with Triple Antibiotic Paste and Combination of Calcium Hydroxide, Chlorhexidine, and Lycopene on Incidence of Interappointment Flare-up: An in vivo Study

ABSTRACT Background The present study was undertaken to evaluate the most suitable intracanal medicament with the least incidence on Interappointment flare-up. Aim To clinically evaluate and compare the effect of combination of calcium hydroxide (CH) and chlorhexidine (CHX) with triple antibiotic paste and combination of CH, CHX, and lycopene on interappointment flare-up. Materials and methods A total of 36 patients requiring root canal treatment were selected according to the selection criteria and divided into three groups: Group I – CH and CHX, group II – triple antibiotic paste, and group III – CH, CHX, and lycopene. Access opening and biomechanical preparation of all samples, and intracanal medicaments were placed respectively. Subsequently, interappointment flare-up was assessed at 1, 2, 3, 7, and 14 days using verbal rating scale. Statistical analysis used One way analysis of variance test and Tukey's post hoc test. Results There was no statistically significant difference seen in the clinical performance of CH + CHX, triple antibiotic paste, and mixture of CH + CHX + lycopene at the end of 14 days in terms of interappointment flare-up. Conclusion All the intracanal medicaments were effective in reducing interappointment flare-up at the end of 14 days. How to cite this article Bilgi PS, Shah NC, Mehta J. Comparative Evaluation of Mixture of Calcium Hydroxide and Chlorhexidine, with Triple Antibiotic Paste and Combination of Calcium Hydroxide, Chlorhexidine, and Lycopene on Incidence of Interappointment Flare-up: An in vivo Study. Int J Clin Dent Res 2017;1(1):10-14.

Colistin Increases the Cidal Activity of Antibiotic Combinations Against Multidrug-Resistant Klebsiella pneumoniae: An In Vitro Model Comparing Multiple Combination Bactericidal Testing at One Peak Serum Concentration and Time-Kill Method.

The lack of treatment for multidrug-resistant (MDR) Enterobacteriaceae often leads to the use of double or triple antibiotic combinations to increase the option of clinical success. This study analyzes multiple combination bactericidal testing (MCBT) to screen double and triple antibiotic combinations, at standard peak serum concentration, for bactericidal activity against 21 MDR Klebsiella pneumoniae isolates. This method was compared with time-killing curves. The full bactericidal activity against all strains was obtained only by adding colistin. MCBT has a potential to become a rapid method for testing multiple antibiotic combinations for MDR microorganisms when colistin is used, providing clinicians with in vitro cidal data within 48 hr of strain isolation.

Triple antibiotic combination therapy may improve but not resolve granuloma annulare.

Granuloma annulare is a fairly common entity yet lacks reliable treatment options especially when multiple lesions or dissemination exists. A recent case series suggests that a regimen of three oral antibiotics may prove to be an effective treatment. Our objective is to evaluate the efficacy of once monthly triple antibiotic therapy for granuloma annulare. We conducted an open-label prospective study of subjects with at least five lesions of granuloma annulare who received once monthly rifampin, ofloxacin, and minocycline for 6 months. Improvement was measured with a novel objective Granuloma Annulare Severity Index (GASI) scoring system. Twenty-one subjects enrolled. Ten subjects (48%) achieved at least a 50% reduction in their GASI, including three subjects (14%) who reached 75% improvement and one subject (5%) whose skin cleared. Six subjects (29%) had no change or worsening of their granuloma annulare. Median GASI scores decreased significantly by 15 points (p < 0.01), although the clinical significance of this result is unclear. As this was a small open-label study without a control group, we cannot determine if the results simply reflect the natural course of the disease. The GASI is not a validated assessment tool. Once monthly triple antibiotic use may improve but not clear granuloma annulare over 6 months. Randomized trials may be warranted to further assess this therapy.

A Galleria mellonella infection model reveals double and triple antibiotic combination therapies with enhanced efficacy versus a multidrug-resistant strain of Pseudomonas aeruginosa

The aim of this study was to compare the inhibitory effect of antibiotic combinations in vitro with efficacy in Galleria mellonella larvae in vivo to identify efficacious combinations that target Pseudomonas aeruginosa. P. aeruginosa NCTC 13437, a multidrug-resistant strain resistant to β-lactams and aminoglycosides, was used. Susceptibility to cefotaxime, piperacillin, meropenem, amikacin, levofloxacin and colistin alone, or in dual or triple combinations, was measured in vitro via a 24 h time-kill assay. In vitro results were then compared with the efficacy of the same dual or triple antibiotic combinations versus G. mellonella larvae infected with P. aeruginosa. G. mellonella haemolymph burden of P. aeruginosa was determined over 96 h post-infection and treatment with the most potent combination therapies. Many dual and triple combinations of antibiotics displayed synergistic inhibition of multidrug-resistant P. aeruginosa in vitro. There was little correlation between combinations that were synergistic in vitro and those that showed enhanced efficacy in vivo versus infected G. mellonella larvae. The most potent dual and triple combinations in vivo were cefotaxime plus piperacillin, and meropenem plus piperacillin and amikacin, respectively. Fewer combinations were found to offer enhanced therapeutic benefit in vivo compared with in vitro. The therapeutic benefit arising from treatment with antibiotic combinations in vivo correlated with reduced larval burden of P. aeruginosa. This study has identified antibiotic combinations that merit further investigation for their clinical potential and has demonstrated the utility of using G. mellonella to screen for novel antibiotic treatments that demonstrate efficacy in vivo.

English

The emergence of extreme drug resistant (XDR) Pseudomonas aeruginosa and Acinetobacter baumannii represent a major problem in health care settings. Colistin is the only therapeutic option available for treatment of infections caused by such pathogens. Worryingly, colistin resistance recently emerged which may lead to the return to the pre antibiotic era. The aim of the present study was to assess for the first time the bactericidal activity of four novel triple antibiotic combinations, including imipenem (IMP), amikacin (AK), cefepime (CEF) and tigecycline (TIG) against four XDR P. aeruginosa and A. baumannii clinical pathogens. Antibiotic combinations were evaluated by time-kill assay at the breakpoints. Three combinations (IMP/TIG/AK, TIG/AK/CEF and IMP/TIG/CEF) showed significant bactericidal activity against XDR A. baumannii isolates. Only two combinations (IMP/AK/CEF and IMP/TIG/AK) displayed remarkable killing against XDR P. aeruginosa isolates. These finding revealed that these triple antibiotic combinations are attractive therapeutic options for treatment of infections caused by XDR pathogens and could be utilized as an alternative to colistin. Further studies are warranted to assess the clinical outcomes of such combinations. Key words: Extreme drug resistant (XDR), Pseudomonas aeruginosa, Acinetobacter baumannii, antibiotic combinations, bactericidal activity.

Evaluation of Double- and Triple-Antibiotic Combinations for VIM- and NDM-Producing Klebsiella pneumoniae by In Vitro Time-Kill Experiments

Combination therapy is recommended for infections with carbapenemase-producing Klebsiella pneumoniae. However, limited data exist on which antibiotic combinations are the most effective. The aim of this study was to find effective antibiotic combinations against metallo-beta-lactamase-producing K. pneumoniae (MBL-KP). Two VIM- and two NDM-producing K. pneumoniae strains, all susceptible to colistin, were exposed to antibiotics at clinically relevant static concentrations during 24-h time-kill experiments. Double- and triple-antibiotic combinations of aztreonam, ciprofloxacin, colistin, daptomycin, fosfomycin, meropenem, rifampin, telavancin, tigecycline, and vancomycin were used. Synergy was defined as a ≥2 log10 decrease in CFU/ml between the combination and its most active drug after 24 h, and bactericidal effect was defined as a ≥3 log10 decrease in CFU/ml after 24 h compared with the starting inoculum. Synergistic or bactericidal activity was demonstrated for aztreonam, fosfomycin, meropenem, and rifampin in double-antibiotic combinations with colistin and also for aztreonam, fosfomycin, and rifampin in triple-antibiotic combinations with meropenem and colistin. Overall, the combination of rifampin-meropenem-colistin was the most effective regimen, demonstrating synergistic and bactericidal effects against all four strains. Meropenem-colistin, meropenem-fosfomycin, and tigecycline-colistin combinations were not bactericidal against the strains used. The findings of this and other studies indicate that there is great potential of antibiotic combinations against carbapenemase-producing K. pneumoniae. However, our results deviate to some extent from those of previous studies, which might be because most studies to date have included KPC-producing rather than MBL-producing strains. More studies addressing MBL-KP are needed.

Investigation of Biofilm-Associated Antibiotic Susceptibilities of Methicillin-Resistant Staphylococci Isolated from Catheter-Related Nosocomial Infections

Risks for development of local and/or systemic infections are the most important complications of catheters that are widely used during hospitalization process. The aims of this study were to investigate and compare the antibiotic susceptibilities of methicillin-resistant staphylococci isolated from catheters, in planktonic and biofilm forms, and to evaluate the antimicrobial effects of antibiotics on those forms alone and in combinations. A total of 30 strains [15 methicillin-resistant Staphylococcus aureus (MRSA) and 15 methicillin-resistant coagulase-negative staphylococci (MR-CNS)] isolated from catheter cultures of patients hospitalized in different clinics and intensive care units in Baskent University Medical School Hospital between 2006-2009, were included in the study. The antibiotic sensitivities of MRSA and MR-CNS isolates were investigated in vitro in planktonic phase and on sessile cells after biofilm was formed. Vancomycin, ciprofloxacin, rifampicin, gentamicin, meropenem, tigecycline, linezolid, ceftazidime and cephazolin were used for antibiotic susceptibility testing. The sensitivity of planktonic cells to antibiotics was primarily investigated, so that minimal inhibitor concentration (MIC) and minimal bactericidal concentration (MBC) values were determined by broth microdilution method. Afterwards, each strain was transformed to sessile cell in a biofilm environment, and MIC and MBC values were also determined for sessile cells. Double and triple antibiotic combinations were prepared, the effectiveness of combinations were studied on both planktonic and biofilm cells with multiple-combination bactericidal testing (MCBT) method. The data set obtained from planktonic and biofilm cells for each antibiotic analyzed via two proportion z test. Statistically significant decreases were found in the sensitivities of sessile cells when compared to planktonic cells (p< 0.01). The tests performed with the use of double and triple antibiotic combinations also showed the susceptibility decrease between planktonic and biofilm forms to be significant in most of the combinations (p< 0.01). The comparison of double and triple antibiotic combinations against planktonic and sessile cells as determined by the inhibition of more than 90% of the strains, revealed no significant difference . Vancomycin and tigecycline were the most effective antibiotics for all isolates in planktonic and sessile cells. Combinations containing vancomycin and rifampicin showed the best activity both double and triple antibiotic combinations against biofilm. In conclusion, our data indicated that combination therapy, especially double combinations of antibiotics seem to be a rational approach for biofilm-related infections.