Streptococcus pneumoniae favors tolerance via metabolic adaptation over resistance to circumvent fluoroquinolones

Streptococcus pneumoniae is a major human pathogen of global health concern and the rapid emergence of antibiotic resistance poses a serious public health problem worldwide. Fluoroquinolone resistance in S. pneumoniae is an intriguing case because the prevalence of fluoroquinolone resistance does not correlate with increasing usage and has remained rare. Our data indicate that deleterious fitness costs in the mammalian host constrain the emergence of fluoroquinolone resistance both by de novo mutation and recombination. S. pneumoniae was able to circumvent such deleterious fitness costs via the development of antibiotic tolerance through metabolic adaptation that reduced the production of reactive oxygen species, resulting in a fitness benefit during infection of mice treated with fluoroquinolones. These data suggest that the emergence of fluoroquinolone resistance is tightly constrained in S. pneumoniae by fitness tradeoffs and that mutational pathways involving metabolic networks to enable tolerance phenotypes are an important contributor to the evasion of antibiotic-mediated killing.IMPORTANCEThe increasing prevalence of antibiotic resistant bacteria is a major global health concern. While many species have the potential to develop antibiotic resistance, understanding the barriers to resistance emergence in the clinic remains poorly understood. A prime example of this is fluroquinolone resistance in Streptococcus pneumoniae, whereby, despite continued utilization, resistance to this class of antibiotic remains rare. In this study, we found that the predominant pathways for developing resistance to this antibiotic class severely compromised the infectious capacity of the pneumococcus, providing a key impediment for the emergence of resistance. Using in vivo models of experimental evolution, we found that S. pneumoniae responds to repeated fluoroquinolone exposure by modulating key metabolic pathways involved in the generation of redox molecules, which leads to antibiotic treatment failure in the absence of appreciable shifts in resistance levels. These data underscore the complex pathways available to pathogens to evade antibiotic mediating killing via antibiotic tolerance.

Should Transperineal Prostate Biopsy Be the Standard of Care?

PURPOSE OF REVIEW

We reviewed the advantages and disadvantages of transperineal prostate biopsy (TP-bx) to evaluate its potential role as the standard of care for prostate biopsy.

RECENT FINDINGS

Studies have suggested no difference in prostate cancer (PCa) detection rate between TP-bx and transrectal biopsy (TR-bx) but have suggested potentially increased detection of anterior prostate tumors. Advances in anesthetic technique have obviated the need for sedation thus allowing TP-bx to become an office-based procedure, which in turn can decrease the overall cost of TP-bx. Furthermore, given the low rate of infectious complications after TP-bx, some have foregone peri-procedural antibiotics without a change in the rate of infectious complications. Recent procedural advances have made TP-bx a tolerable, office-based procedure. Given the similar diagnostic performance and the benefits for the patient and community, TP-bx should become the standard of care for prostate biopsy for most patients. Future efforts should address the barriers for more universal adoption.

Surveillance of Wisconsin Organisms for Trends in Antimicrobial Resistance and Epidemiology (SWOTARE): 2018-2019 Report on Enterobacter cloacae and Klebsiella pneumoniae Clinical Isolates

Objectives: Both Enterobacter cloacae and Klebsiella pneumoniae have been regarded as important opportunistic pathogens for humans. Recent data have described the spread of multi-resistant strains of these organisms. Development of novel resistance phenotypes may result in a reduction in anti-infective efficacy, therefore making patient treatment decisions challenging. The Surveillance of Wisconsin Organisms for Trends in Antimicrobial Resistance and Epidemiology (SWOTARE) program aims to combat this issue and improve antibiotic stewardship by monitoring antimicrobial resistance at a local level.Design: Multi-center laboratory surveillance, with testing at a single location utilizing standardized media and susceptibility testing protocolsMethods: In the years 2018 and 2019, a total of 591 clinically-significant E. cloacae and 668 clinically-significant K. pneumoniae isolates were collected through this initiative; limited demographic data were also supplied. Isolates were tested by broth microdilution procedures advocated by Clinical and Laboratory Standards Institute.Results: On a statewide level, both E. cloacae and K. pneumoniae demonstrated in vitro potency to carbapenem and aminoglycoside agents at rates exceeding 96%. K. pneumoniae isolates were generally more susceptible to cephem and monobactam agents than E. cloacae isolates; the converse was true for fluoroquinolone agents. Patterns of local antimicrobial resistance were revealed that were not apparent at the state level. E. cloacae isolates submitted from the Northcentral and Southeast regions demonstrated decreased susceptibility to five antimicrobial agents (notably third- and fourth-generation cephems) when compared to the state average. Isolates derived from males, older individuals, and urogenital sources exhibited decreased susceptibility to third- and fourth-generation cephem agents (P ≤ 0.047). With respect to K. pneumoniae, antimicrobial resistance phenotype was not a function of geography or gender. However, isolates emanating from older patients and the respiratory tract showed decreased susceptibility to ampicillin/sulbactam and cefazolin, respectively (P ≤ 0.019).Conclusions: Antimicrobial resistance surveillance at a local level provides utility to community/rural hospital clinicians, pharmacists, and infection control practitioners. With respect to E. cloacae, further surveillance efforts may be necessary in the Northcentral and Southeast regions of Wisconsin. Subanalysis of demographic data indicated cephem-resistance correlates that are not apparent at the statewide level.

Fluoroquinolone Can Be an Effective Treatment Option for Acute Pyelonephritis When the Minimum Inhibitory Concentration of Levofloxacin for the Causative Escherichia coli Is ≤16 mg/L

The purpose of this study was to determine whether the fluoroquinolone (FQ) minimum inhibitory concentration (MIC) for the causative agent Escherichia coli influences the clinical response of FQ treatment at 72 h in patients with community-acquired acute pyelonephritis (CA-APN). We prospectively collected the clinical data of women with CA-APN from 11 university hospitals from March 2010 to February 2012 as well as E. coli isolates from the urine or blood. In total, 78 patients included in this study received FQ during the initial 72 h, and the causative E. coli was detected. The clinical response at 72 h was significantly higher in patients with a levofloxacin MIC ≤ 16 mg/L than in those with an MIC > 16 mg/L (70.4% vs. 28.6%, p = 0.038). No difference was observed in clinical response at 72 h based on ciprofloxacin MIC. To summarize, FQ can be an effective treatment option for CA-APN when levofloxacin MIC against E. coli is ≤16 mg/L.

Antimicrobial use among adult inpatients at hospital sites within the Canadian Nosocomial Infection Surveillance Program: 2009 to 2016

BACKGROUND

Antimicrobial resistance is a growing threat to the world's ability to prevent and treat infections. Links between quantitative antibiotic use and the emergence of bacterial resistance are well documented. This study presents benchmark antimicrobial use (AMU) rates for inpatient adult populations in acute-care hospitals across Canada.

METHODS

In this retrospective surveillance study, acute-care adult hospitals participating in the Canadian Nosocomial Infection Surveillance Program (CNISP) submitted annual AMU data on all systemic antimicrobials from 2009 to 2016. Information specific to intensive care units (ICUs) and non-ICU wards were available for 2014-2016. Data were analyzed using defined daily doses (DDD) per 1000 patient days (DDD/1000pd).

RESULTS

Between 2009 and 2016, 16-18 CNISP adult hospitals participated each year and provided their AMU data (22 hospitals participated in ≥1 year of surveillance; 11 in all years). From 2009 to 2016, there was a significant reduction in use (12%) (from 654 to 573 DDD/1000pd, p = 0.03). Fluoroquinolones accounted for the majority of this decrease (47% reduction in combined oral and intravenous use, from 129 to 68 DDD/1000pd, p < 0.002). The top five antimicrobials used in 2016 were cefazolin (78 DDD/1000pd), piperacillin-tazobactam (53 DDD/1000pd), ceftriaxone (49 DDD/1000pd), vancomycin (combined oral and intravenous use was 44 DDD/1000pd; 7% of vancomycin use was oral), and ciprofloxacin (combined oral and intravenous use: 42 DDD/1000pd). Among the top 10 antimicrobials used in 2016, ciprofloxacin and metronidazole use decreased significantly between 2009 and 2016 by 46% (p = 0.002) and 26% (p = 0.002) respectively. Ceftriaxone (85% increase, p = 0.0008) and oral amoxicillin-clavulanate (140% increase, p < 0.0001) use increased significantly but contributed only a small component (8.6 and 5.0%, respectively) of overall use.

CONCLUSIONS

This study represents the largest collection of dispensed antimicrobial use data among inpatients in Canada to date. Between 2009 and 2016, there was a significant 12% decrease in AMU, driven primarily by a 47% decrease in fluoroquinolone use. Modest absolute increases in parenteral ceftriaxone and oral amoxicillin-clavulanate use were noted but contributed a small amount of total AMU. Ongoing national surveillance is crucial for establishing benchmarks and antimicrobial stewardship guidelines.

Molecular characterization of plasmid-mediated AmpC beta-lactamase- and extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae among corvids (Corvus brachyrhynchos and Corvus corax) roosting in Canada

This study evaluated the carriage of AmpC and extended-spectrum beta-lactamase (ESBL) genes and associated plasmids in faecal bacteria of Canadian corvids. Faecal samples from 449 birds in five roosting sites across Canada were analyzed using selective media, screening for AmpC and ESBL genes by PCR, and sequencing. Genomic relatedness was determined by PFGE and MLST. Plasmid mobility was studied by conjugation and transformation experiments, followed by plasmid typing. In total, 96 (21%, n = 449) cefotaxime-resistant Escherichia coli and three (0.7%) Klebsiella pneumoniae isolates were identified. ESBL genes blaCTX-M-1 (n = 3), blaCTX-M-14 (n = 2), blaCTX-M-32 (n = 2) and blaCTX-M-124 (n = 1) were detected in eight E. coli isolates, whereas blaSHV-2 (2) was found in two K. pneumoniae. E. coli isolates contained blaCMY-2 (n = 83) and blaCMY-42 (n = 1). The high genetic diversity of the isolates and presence of clinically important E. coli ST69 (n = 1), ST117 (n = 7) and ST131 (n = 1) was revealed. AmpC genes were predominantly carried by plasmids of incompatibility groups I1 (45 plasmids), A/C (10) and K (7). The plasmid IncI1/ST12 was most common and found in diverse E. coli STs in all sites. Highly diverse E. coli isolates containing AmpC and ESBL genes, including clinically important clones and emerging plasmids, are in circulation throughout Canadian wildlife.

Trend of antibiotics usage for acute pyelonephritis in Korea based on national health insurance data 2010-2014

BACKGROUND

The objective of this study is to describe the changes in prescribing practices of antibiotics to treat acute pyelonephritis (APN) in Korea.

METHODS

The claim data base of the Health Insurance Review and Assessment Service in Korea was used to select patients with ICD-10 codes N10 (acute tubulo-interstitial nephritis) or N12 (tubulo-interstitial nephritis, not specified as acute nor chronic) as the primary discharge diagnosis during 2010-2014. Consumption of each class of antibiotics was converted to Defined Daily Dose (DDD)/event.

RESULTS

Throughout the five-year period, the average antibiotic consumption were 11.3 DDD per inpatient event and 6.0 DDD per outpatient event. The annual average antibiotic consumption increased for inpatients (P = 0.002), but remained stable for outpatients (P = 0.066). The use of parenteral antibiotics increased for inpatients (P < 0.001), but decreased for outpatients (P = 0.017). As for the the antibiotic classes, 3rd generation cephalosporins (3rd CEPs) was the most commonly prescribed (41.4%) for inpatients, followed by fluoroquinolones (FQs) (28.5%); for outpatient, FQs (54.8%) was the most commonly prescribed, followed by 3rd CEPs (13.1%). The use of 3rd CEPs (P < 0.001), beta-lactam/beta-lactamase inhibitors (P = 0.007), and carbapenems (P < 0.001) increased substantially for the treatment of hospitalized APN patients. In particular, carbapenems use increased 3.1-fold over the 5 years.

CONCLUSIONS

Prescription of broad-spectrum antibiotics increased much for the treatment of APN in Korea during 2010-2014.

Effectiveness of fosfomycin tromethamine prophylaxis in preventing infection following transrectal ultrasound-guided prostate needle biopsy: Results from a large Canadian cohort

OBJECTIVES

Rates of infection following transrectal ultrasound-guided prostate biopsy (TRUSPB) are increasing. The aim of this study was to evaluate the effectiveness of fosfomycin tromethamine (FMT) prophylaxis in preventing post-TRUSPB infectious complications.

METHODS

This nested case-control study included patients undergoing TRUSPB in a Canadian tertiary-care hospital who developed post-TRUSPB bacteraemia or urinary tract infection. Four prophylaxis periods were defined: (i) ciprofloxacin, low-resistance period (CIPRO-LOW), 2002-2009; (ii) ciprofloxacin, high-resistance period (CIPRO-HIGH), 2010-October 2013; (iii) oral FMT, one dose (FOSFO1), December 2013-September 2015; and (iv) oral FMT, two doses (FOSFO2), November 2015-June 2016. Incidence rates of the infection were calculated.

RESULTS

TRUSPB (n=9391) resulted in 138 cases of urinary sepsis (58% with bacteraemia). The incidence rates were 1.8% (CIPRO-HIGH), 3.5% (FOSFO1; P=0.004 vs. CIPRO-HIGH) and 2.7% (FOSFO2; P=0.19 vs. CIPRO-HIGH). Although Escherichia coli remained the predominant pathogen with fosfomycin-based regimens, the proportion of infections caused by Klebsiella spp. was higher (20/66; 30.3%) than with ciprofloxacin-based regimens (2/77; 2.6%; P<0.0001).

CONCLUSION

Independent risk factors for infection were the prophylactic regimen administered, presence of urological co-morbidities and diabetes. FMT was therefore not an effective alternative to ciprofloxacin for preventing post-TRUSPB urinary sepsis. These results highlight the need for novel antibacterial prophylaxis approaches.

Epidemiology of bacterial corneal ulcers at tertiary centres in Vancouver, B.C

OBJECTIVE

To report the epidemiology of culture-positive bacterial corneal ulcers in Vancouver, B.C., Canada.

DESIGN

Retrospective, observational case series.

METHODS

Predetermined search terms were entered into the hospitals' electronic microbiology databases to create a cohort of patients who had undergone corneal scrapings for ulcers from April 2006 to March 2011. All specimens were plated on culture media. Cultured species were identified, and antimicrobial sensitivities were obtained. Clinical charts were then reviewed to identify associated risk factors.

RESULTS

In total 281 corneal scrapings were included, with a positive culture recovery rate of 75%. Bacterial keratitis accounted for 84.8% of culture-positive ulcers, followed by fungi (10%) and finally Acanthamoeba (5.2%); 73% of ulcers were monomicrobial in origin and 28% polymicrobial. We found an increase in Gram-negative micro-organisms over time. General sensitivity to antibiotics did not change over time. A major risk factor for Gram-positive involvement was ocular surface disease, whereas contact lens wear was a major risk factor for Gram-negative involvement.

CONCLUSIONS

Bacterial keratitis was found to be the major cause of infectious keratitis in Vancouver, B.C. The majority of bacterial ulcers were caused by Gram-positive bacteria. However, we found an increase in Gram-negative involvement over time. Contact lens wear was identified as the major risk factor for development of Gram-negative ulcers. Pre-existing ocular disease was associated with Gram-positive infection. Susceptibility of Gram-negative bacteria to common broad-spectrum antibiotics was high, but susceptibility of Gram-positive bacteria to these antibiotics was lower and more variable.

Cost analysis of nonoperative management of acute appendicitis in children

PURPOSE

The purpose of this study was to determine if nonoperative management of acute appendicitis in children is more cost effective than appendectomy.

METHODS

A retrospective review of children (6-17years) with acute appendicitis treated nonoperatively (NOM) from May 2012 to May 2015 was compared to similar patients treated with laparoscopic appendectomy (OM) (IRB#107535). Inclusion criteria included symptoms ≤48h, localized peritonitis, and ultrasound confirmation of acute appendicitis. Variables analyzed included failure rates, complications, length of stay (LOS), and cost analysis.

RESULTS

26 NOM patients (30% female, mean age 12) and 26 OM patients (73% female, mean age 11) had similar median initial LOS (24.5h (NOM) vs 16.5h (OM), p=0.076). Median total LOS was significantly longer in the NOM group (34.5h (NOM) vs 17.5 (OM), p=0.01). Median cost of appendectomy was $1416.14 (range $781.24-$2729.97). 9/26 (35%) NOM patients underwent appendectomy for recurrent appendicitis. 4/26 (15%) OM patients were readmitted (postoperative abscess (n=2), Clostridium difficile colitis (n=1), postoperative nausea/vomiting (n=1)). Median initial hospital admission costs were significantly higher in the OM group ($3502.70 (OM) vs $1870.37 (NOM), p=0.004)). However, median total hospital costs were similar for both groups ($3708.68 (OM) vs $2698.99 (NOM), p=0.065)).

CONCLUSION

Although initial costs were significantly less in children with acute appendicitis managed nonoperatively, total costs were similar for both groups. The high failure rate of nonoperative management in this series contributed to the total increased cost in the NOM group.

LEVEL OF EVIDENCE

3b.

Susceptibility patterns and ESBL rates of Escherichia coli from urinary tract infections in Canada and the United States, SMART 2010-2014

Increasing antimicrobial resistance in urinary tract infections (UTI) is a concern. To evaluate resistance trends, 3498 Escherichia coli UTI isolates were collected from 2010 to 2014 in the Study for Monitoring Antimicrobial Resistance Trends (SMART) in Canada and United States (US). ESBL phenotype and susceptibility were determined using CLSI microdilution and breakpoints. US ESBL rates increased in 2010-2014 (7.8-18.3%, P < 0.0001), especially among hospital-associated (HA) infections, males, and older patients (≥65 years). Overall, ESBL rates in Canada showed no significant trend (10.4-13.0%. P = 0.079), and were lower than US rates in recent years, but increased significantly among community-associated (CA) infections, females, and older patients. In the US, but not Canada, susceptibility to cephalosporins and fluoroquinolones among 2013-2014 isolates was significantly lower in isolates from HA than CA UTI, males than females, and ≥65- than <65-year-olds. These observations confirm increasing resistance in E. coli. Subgroup analyses like these may help direct empirical therapy.

Bloodstream Infections in Hospitalized Children: Epidemiology and Antimicrobial Susceptibilities

BACKGROUND

Bloodstream infection is a major cause of morbidity and mortality. Much of our understanding of the epidemiology and resistance patterns of bloodstream infections comes from studies of hospitalized adults.

METHODS

We evaluated the epidemiology and antimicrobial resistance of bloodstream infections occurring during an 11-year period in a large, tertiary care children's hospital in the US. All positive blood cultures were identified retrospectively from clinical microbiology laboratory records. We excluded repeat positive cultures with the same organism from the same patient within 30 days and polymicrobial infections.

RESULTS

We identified 8196 unique episodes of monomicrobial bacteremia in 5508 patients. Overall, 46% were community onset, 72% were Gram-positive bacteria, 22% Gram-negative bacteria and 5% Candida spp. Coagulase negative Staphylococcus was the most common isolated organism. ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.) accounted for 20% of episodes. No S. aureus isolate was resistant to vancomycin or linezolid, and no increase in vancomycin minimum inhibitory concentration among methicillin-resistant S. aureus was observed during the study period. Clinically significant increases in vancomycin-resistant Enterococcus, ceftazidime-resistant P. aeruginosa or carbapenem-resistant Enterobacteriaceae were not observed during the study period; however, rates of methicillin-resistant S. aureus increased over time (P < 0.01).

CONCLUSIONS

Gram-positive and ESKAPE organisms are leading causes of bacteremia in hospitalized children. Although antimicrobial resistance patterns were favorable compared with prior reports of hospitalized adults, multicenter studies with continuous surveillance are needed to identify trends in the emergence of antimicrobial resistance in this setting.

Threading the Needle: Small-Molecule Targeting of a Xenobiotic Receptor to Ablate Escherichia coli Polysaccharide Capsule Expression Without Altering Antibiotic Resistance

BACKGROUND

Uropathogenic Escherichia coli (UPEC), a leading cause of urinary tract and invasive infections worldwide, is rapidly acquiring multidrug resistance, hastening the need for selective new anti-infective agents. Here we demonstrate the molecular target of DU011, our previously discovered potent, nontoxic, small-molecule inhibitor of UPEC polysaccharide capsule biogenesis and virulence.

METHODS

Real-time polymerase chain reaction analysis and a target-overexpression drug-suppressor screen were used to localize the putative inhibitor target. A thermal shift assay quantified interactions between the target protein and the inhibitor, and a novel DNase protection assay measured chemical inhibition of protein-DNA interactions. Virulence of a regulatory target mutant was assessed in a murine sepsis model.

RESULTS

MprA, a MarR family transcriptional repressor, was identified as the putative target of the DU011 inhibitor. Thermal shift measurements indicated the formation of a stable DU011-MprA complex, and DU011 abrogated MprA binding to its DNA promoter site. Knockout of mprA had effects similar to that of DU011 treatment of wild-type bacteria: a loss of encapsulation and complete attenuation in a murine sepsis model, without any negative change in antibiotic resistance.

CONCLUSIONS

MprA regulates UPEC polysaccharide encapsulation, is essential for UPEC virulence, and can be targeted without inducing antibiotic resistance.

Molecular epidemiology and genetic diversity of fluoroquinolone-resistant Escherichia coli isolates from patients with community-onset infections in 30 Chinese county hospitals

The high frequency of fluoroquinolone resistance in Escherichia coli is a feature of clinical bacteriology in China, where the molecular epidemiology and genetic characteristics of this resistance in county hospitals remain unclear. A total of 590 nonduplicate E. coli isolates from 30 county hospitals located across seven Chinese regions were examined for plasmid-mediated quinolone resistance (PMQR) genes and mutations in quinolone resistance-determining regions (QRDRs). Multilocus sequence typing (MLST) and phylogenetic analysis of fluoroquinolone-resistant isolates were used to determine their genetic relatedness. The ciprofloxacin resistance rate of community-onset E. coli was 51.2%, and at least one PMQR gene was carried by 220 (37.3%) isolates. These included qnr (3.7%), aac(6')-Ib-cr (19.7%), qepA (14.4%), and oqxAB (3.8%). Two novel oqxB mutants were identified and named oqxB20 and oqxB29. From 60 sequence types (STs) isolated, 5 novel STs (ST4499 to ST4503) were identified. ST1193 (7.9%) was the second most abundant ST among fluoroquinolone-resistant isolates (ST131 was the most common, with 14.6%), and this is the first report of it in China. This is also the first report of ST2115 and ST3014 isolates from human samples. Ciprofloxacin-resistant E. coli isolates fell mainly into phylogroups B2 and D. The rates of fluoroquinolone resistance and the prevalence of PMQR genes in community-onset E. coli isolates from Chinese county hospitals were high. The wide-ranging molecular epidemiology of E. coli isolates from scattered locations across China indicates that fluoroquinolone resistance evolved from different sources.

Predictive utility of prior positive urine cultures

BACKGROUND

A patient's prior urine cultures are often considered when choosing empiric antibiotic therapy for a suspected urinary tract infection. We sought to evaluate how well previous urine cultures predict the identity and susceptibility of organisms in a patient's subsequent urine cultures.

METHODS

We conducted a multinational, multicenter, retrospective cohort study, including 22 019 pairs of positive urine cultures from 4351 patients across 2 healthcare systems in Toronto, Ontario, and Chicago, Illinois. We examined the probability of the same organism being identified from the same patient's positive urine culture as a function of time elapsed from the previous positive urine specimen; in cases where the same organism was identified we also examined the likelihood of the organism exhibiting the same or better antimicrobial susceptibility profile.

RESULTS

At 4-8 weeks between cultures, the correspondence in isolate identity was 57% (95% confidence interval [CI], 55%-59%), and at >32 weeks it was 49% (95% CI, 48%-50%), still greater than expected by chance (P < .001). The susceptibility profile was the same or better in 83% (95% CI, 81%-85%) of isolate pairs at 4-8 weeks, and 75% (95% CI, 73%-77%) at >32 weeks, still greater than expected by chance (P < .001). Despite high local rates of ciprofloxacin resistance in urine isolates across all patients (40%; 95% CI, 39.5%-40.5%), ciprofloxacin resistance was <20% among patients with a prior ciprofloxacin sensitive organism and no subsequent fluoroquinolone exposure.

CONCLUSIONS

A patient's prior urine culture results are useful in predicting the identity and susceptibility of a current positive urine culture. In areas of high fluoroquinolone resistance, ciprofloxacin can be used empirically when prior urine culture results indicate a ciprofloxacin-susceptible organism and there has been no history of intervening fluoroquinolone use.

In Vitro Antibiofilm Efficacies of Different Antibiotic Combinations with Zinc Sulfate against Pseudomonas aeruginosa Recovered from Hospitalized Patients with Urinary Tract Infection

Urinary tract infections (UTIs) are a serious healthcare dilemma influencing millions of patients every year and represent the second most frequent type of body infection. Pseudomonas aeruginosa is a multidrug-resistant pathogen causing numerous chronic biofilm-associated infections including urinary tract, nosocomial, and medical devices-related infections. In the present study, the biofilm of P. aeruginosa CCIN34519, recovered from inpatients with UTIs, was established on polystyrene substratum and scanning electron microscopy (SEM) and was utilized for visualization of the biofilm. A previously described in vitro system for real-time monitoring of biofilm growth/inhibition was utilized to assess the antimicrobial effects of ciprofloxacin, levofloxacin, moxifloxacin, norfloxacin, ertapenem, ceftriaxone, gentamicin, and tobramycin as single antibiotics as well as in combinations with zinc sulfate (2.5 mM) against P.aeruginosa CCIN34519 biofilm. Meanwhile, minimum inhibitory concentrations (MICs) at 24 h and mutant prevention concentrations (MPCs) at 96 h were determined for the aforementioned antibiotics. The real-time monitoring data revealed diverse responses of P.aeruginosa CCIN34519 biofilm to the tested antibiotic-zinc sulfate combinations with potential synergisms in cases of fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin, and norfloxacin) and carbapenem (ertapenem) as demonstrated by reduced MIC and MPC values. Conversely, considerable antagonisms were observed with cephalosporin (ceftriaxone) and aminoglycosides (gentamicin, and tobramycin) as shown by substantially increased MICs and MPCs values. Further deliberate in vivo investigations for the promising synergisms are required to evaluate their therapeutic potentials for treatment of UTIs caused by P. aeruginosa biofilms as well as for developing preventive strategies.

Moxifloxacin in lower respiratory tract infections: in silico simulation of different bacterial resistance and drug exposure scenarios

Moxifloxacin has potent bactericidal activity against Streptococcus pneumoniae; a major causative organism of lower respiratory tract infections. This study aims to use the pharmacokinetic/pharmacodynamic indices to predict the therapeutic outcome under different scenarios of moxifloxacin exposure and pneumococcal resistance. STELLA(®) software was used to simulate the pharmacokinetics and pharmacodynamics of moxifloxacin in patients with severe pneumonia and acute exacerbations of chronic bronchitis (AECB). The current dose of moxifloxacin was found to be insufficient for eradication of ciprofloxacin resistant bacteria in ventilated patients with severe bronchopneumonia. This can be attributed to the lower tissue penetration observed in this population. Increasing the dose to 600 mg was able to achieve higher levels of free drug AUC/MIC in both bronchial and plasma compartments. In AECB, moxifloxacin achieved the same AUC/MIC values observed in pneumonia at the different MIC values. This may allow the extrapolation of findings of moxifloxacin studies in pneumonia to the management of patients with AECB.

New 7-[4-(4-(un)substituted)piperazine-1-carbonyl]- piperazin-1-yl] derivatives of fluoroquinolone: synthesis and antimicrobial evaluation

Fluoroquinolones have been a class of important synthetic antimicrobial agents broadly and effectively used in clinic for infectious diseases. In this study, the synthesis of a range of fluoroquinolone derivatives with 4-(carbopiperazin-1-yl)piperazinyl moieties at the C7 position and their inhibition of bacterial pathogens commonly disseminated in hospital environment were described. The results indicated that a 7-[4-(4-(benzoyl)carbopiperazin-1-yl)]piperazinyl derivative 5h and two 7-[4-(4-(benzenesulfonyl)carbopiperazin-1-yl)]piperazinyl derivatives 5k and 5l showed more promising growth inhibition of ciprofloxacin-resistant P. aeruginosa (CRPA) with MIC values as low as 16 μg/mL which is 16-fold more potent than ciprofloxacin, while most of other derivatives maintained potency against methicillin-resistant Staphylococcus aureus (MRSA).