Cefotaxime and Amoxicillin-Clavulanate Synergism against Extended-Spectrum-β-Lactamase-Producing Escherichia coli in a Murine Model of Urinary Tract Infection

Variability in cell division among anatomical sites shapes Escherichia coli antibiotic survival in a urinary tract infection mouse model

Urinary tract infection (UTI), mainly caused by Escherichia coli, are frequent and have a recurrent nature even after antibiotic treatment. Potential bacterial escape mechanisms include growth defects, but probing bacterial division in vivo and establishing its relation to the antibiotic response remain challenging. Using a synthetic reporter of cell division, we follow the temporal dynamics of cell division for different E. coli clinical strains in a UTI mouse model with and without antibiotics. We show that more bacteria are actively dividing in the kidneys and urine compared with the bladder. Bacteria that survive antibiotic treatment are consistently non-dividing in three sites of infection. Additionally, we demonstrate how both the strain in vitro persistence profile and the microenvironment impact infection and treatment dynamics. Understanding the relative contribution of the host environment, growth heterogeneity, non-dividing bacteria, and antibiotic persistence is crucial to improve therapies for recurrent infections.

Peptidoglycan biosynthesis-associated enzymatic kinetic characteristics and β-lactam antibiotic inhibitory effects of different Streptococcus pneumoniae penicillin-binding proteins

Penicillin-binding proteins (PBPs) include transpeptidases, carboxypeptidases, and endopeptidases for biosynthesis of peptidoglycans in the cell wall to maintain bacterial morphology and survival in the environment. Streptococcus pneumoniae expresses six PBPs, but their enzymatic kinetic characteristics and inhibitory effects on different β-lactam antibiotics remain poorly understood. In this study, all the six recombinant PBPs of S. pneumoniae displayed transpeptidase activity with different substrate affinities (Km = 1.56-9.11 mM) in a concentration-dependent manner, and rPBP3 showed a greater catalytic efficiency (Kcat = 2.38 s-1) than the other rPBPs (Kcat = 3.20-7.49 × 10-2 s-1). However, only rPBP3 was identified as a carboxypeptidase (Km = 8.57 mM and Kcat = 2.57 s-1). None of the rPBPs exhibited endopeptidase activity. Penicillin and cefotaxime inhibited the transpeptidase and carboxypeptidase activity of all the rPBPs but imipenem did not inhibited the enzymatic activities of rPBP3. Except for the lack of binding of imipenem to rPBP3, penicillin, cefotaxime, and imipenem bound to all the other rPBPs (KD = 3.71-9.35 × 10-4 M). Sublethal concentrations of penicillin, cefotaxime, and imipenem induced a decrease of pneumococcal pbps-mRNA levels (p < 0.05). These results indicated that all six PBPs of S. pneumoniae are transpeptidases, while only PBP3 is a carboxypeptidase. Imipenem has no inhibitory effect on pneumococcal PBP3. The pneumococcal genes for encoding endopeptidases remain to be determined.

Predictive factors of urinary tract infections caused by extended-spectrum β-lactamase-producing Escherichia coli in children: a prospective Tunisian study

AIM

To identify the predictive factors for the occurrence of community-acquired urinary tract infections caused by Extended-Spectrum β-Lactamase-Producing Escherichia coli in children.

METHODS

This was a single-center prospective observational study of children and young adults with community-acquired urinary tract infections caused by Extended-Spectrum β-Lactamase-Producing Escherichia coli. The study was conducted in the pediatric nephrology department in Charles Nicolle Hospital, Tunis, Tunisia from January 1st, 2019, to December 31, 2020. Patients ≤20 years with community-acquired urinary tract infection caused by Escherichia coli were included prospectively in our study.

RESULTS

We collected 290 urinary tract infections in 218 patients, including 92 urinary tract infections due to Extended-Spectrum β-Lactamase-Producing Escherichia coli. The mean age of children was 50.10±54.28 months, with a female predominance in 65.2% of cases. Risk factors for the acquisition of multidrug-resistant bacteria were antibiotic therapy in the previous three months, antibiotic prophylaxis, hospitalization in the year preceding the urinary tract infections, and outpatient care in the previous six months (p < 0.05). Resistance to Ceftazidime, Cefotaxime, Cefixime, Gentamicin and Ofloxacin was significantly associated with the presence of an Extended-Spectrum β-Lactamase strain. Antibiotic resistance was significantly more observed in the age group above 6 years. Co-habitation with health care worker was a risk factor for resistance to Amoxicillin-Clavulanic Acid.

CONCLUSION

Understanding the epidemiological profile and risk factors for ESBL-producing UTIs, including Extended-Spectrum β-Lactamase-producing Escherichia coli in the pediatric population, could improve the therapeutic approach and lead to more rational prescription of antibiotics.

Synergistic Activity of Pep16, a Promising New Antibacterial Pseudopeptide against Multidrug-Resistant Organisms, in Combination with Colistin against Multidrug-Resistant Escherichia coli, In Vitro and in a Murine Peritonitis Model

Colistin is a drug of last resort to treat extreme drug-resistant Enterobacterales, but is limited by dose-dependent toxicity and the emergence of resistance. A recently developed antimicrobial pseudopeptide, Pep16, which acts on the cell membrane, may be synergistic with colistin and limit the emergence of resistance. We investigated Pep16 activity against Escherichia coli with varying susceptibility to colistin, in vitro and in a murine peritonitis model. Two isogenic derivatives of E. coli CFT073 (susceptible and resistant to colistin) and 2 clinical isolates (susceptible (B119) and resistant to colistin (Af31)) were used. Pep16 activity, alone and in combination with colistin, was determined in vitro (checkerboard experiments, time-kill curves, and flow cytometry to investigate membrane permeability). Toxicity and pharmacokinetic analyses of subcutaneous Pep16 were performed in mice, followed by the investigation of 10 mg/kg Pep16 + 10 mg/kg colistin (mimicking human concentrations) in a murine peritonitis model. Pep16 alone was inactive (MICs = 32-64 mg/L; no bactericidal effect). A concentration-dependent bactericidal synergy of Pep16 with colistin was evidenced on all strains, confirmed by flow cytometry. In vivo, Pep16 alone was ineffective. When Pep16 and colistin were combined, a significant decrease in bacterial counts in the spleen was evidenced, and the combination prevented the emergence of colistin-resistant mutants, compared to colistin alone. Pep16 synergizes with colistin in vitro, and the combination is more effective than colistin alone in a murine peritonitis by reducing bacterial counts and the emergence of resistance. Pep16 may optimize colistin use, by decreasing the doses needed, while limiting the emergence of colistin-resistant mutants.

Studies on Virulence and Extended-Spectrum β-Lactamase-Producing Uropathogenic Escherichia coli Isolates and Therapeutic Effect of Fosfomycin in Acute Pyelonephritis Mice

The understanding about virulence factors (VFs) and the drug resistance of uropathogenic Escherichia coli (UPEC) helps us understand the pathogenesis of urinary tract infections (UTIs) and make better decisions for clinical treatment. This study examined the correlation between the extended-spectrum β-lactamases (ESBLs) phenotype and VFs in UPEC strains. In addition, we validated the therapeutic potential of fosfomycin in acute pyelonephritis mice. From May 2017 to November 2018, 22 nonduplicate E coli. strains were isolated from UTI patients. PCR was utilized to detect the distribution of virulence genes. We also analyzed the ESBL phenotype in E coli. We further evaluated the therapeutic effect of intravenous fosfomycin treatment in the acute pyelonephritis (APN) model. All 22 UPEC strains expressed the type 1 fimbriae (FimH) gene and more than 50% (12/22) of strains produced ESBLs. The detection rates of the iron acquisition-associated genes ChuT and IutA were 77.3% (n = 17) and 50% (n = 11) and those of P fimbria papA and papC genes were 45% (n = 10) and 50% (n = 11), respectively. Though the VFs were closely related with pathologenicity, the relationship between VFs and ESBLs still needs further investigation. Furthermore, intravenous fosfomycin 800 mg/kg significantly reduced the bacterial load and the inflammatory infiltration in the bladder and kidney, maintaining the structural integrity of the kidney. Intravenous fosfomycin administration can be used for the treatment of acute pyelonephritis caused by highly pathogenic and drug-resistant UPEC strains.

Single-dose amikacin plus 7 days of amoxicillin/clavulanate to treat acute cystitis caused by extended-spectrum beta-lactamase-producing Escherichia coli: A retrospective cohort study

PURPOSE

Treatment options for urinary tract infection (UTI) caused by extended-spectrum beta-lactamase (ESBL)-producing organisms are limited other than carbapenem. Accordingly, clinicians should investigate alternative antimicrobial options for limited infection. This study was performed to assess the efficacy of single-dose amikacin and a 7-day oral regimen of amoxicillin/clavulanate for the treatment of acute cystitis caused by ESBL-producing Escherichia coli and Klebsiella pneumoniae.

MATERIALS AND METHODS

A single-dose amikacin and 7-day oral amoxicillin/clavulanate regimen was given to all patients with acute cystitis or recurrent cystitis between May 2016 and October 2018. We conducted a retrospective cohort study assessing the efficacy of this regimen for the treatment of UTI due to ESBL-producing organisms. Both clinical and laboratory efficacy were assessed a minimum of 7 days and a maximum of 14 days after the completion of treatment.

RESULTS

A total of 47 patients were enrolled in this study. E. coli and K. pneumoniae were isolated in 44 patients (93.6%) and 3 patients (6.4%), respectively. Of the 47 enrolled, 39 patients (83.0%) showed sterile culture results on follow-up. Thirty-seven patients (78.7%) showed improvement of symptoms. Of 8 patients who showed bacterial persistence, 4 patients showed ESBL-producing E. coli, whereas 4 patients showed non-ESBL E. coli on follow-up cultures. During follow-up, 12 patients experienced the recurrence of acute cystitis with a median recurrence period of 2.5 months.

CONCLUSIONS

The combination of amoxicillin/clavulanate and amikacin may be an alternative to carbapenem treatment in patients with acute cystitis caused by ESBL-producing Enterobacteriaceae.

Evaluation of Immunocompetent Urinary Tract Infected Balb/C Mouse Model For the Study of Antibiotic Resistance Development Using Escherichia Coli CFT073 Infection

Urinary tract infections (UTI) are common worldwide and are becoming increasingly difficult to treat because of the development of antibiotic resistance. Immunocompetent murine models of human UTI have been used to study pathogenesis and treatment but not for investigating resistance development after treatment with antibiotics. In this study, intravesical inoculation of uropathogenic Escherichia coli CFT073 in immunocompetent Balb/c mice was used as a model of human UTI. The value of the model in investigating antibiotic exposure on in vivo emergence of antibiotic resistance was examined. Experimentally infected mice were treated with 20 or 200 mg/kg ampicillin, 5 or 50 mg/kg ciprofloxacin, or 100 or 1000 mg/kg of fosfomycin. Ampicillin and ciprofloxacin were given twice daily at 8 h intervals, and fosfomycin was given once daily. Antibiotic treatment began 24 h after bacterial inoculation and ended after 72 h following the initial treatment. Although minimum inhibitory concentrations (MIC) for the experimental strain of E. coli were exceeded at peak concentrations in tissues and consistently in urine, low levels of bacteria persisted in tissues in all experiments. E. coli from bladder tissue, kidney, and urine grew on plates containing 1× MIC of antibiotic, but none grew at 3× MIC. This model is not suitable for studying emergent resistance but might serve to examine bacterial persistence.

Effective Oral Combination Treatment for Extended-Spectrum Beta-Lactamase-Producing Escherichia coli

Background: Extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-EC) is increasing worldwide. The drugs of choice for treatment of ESBLs are parenteral carbapenems. The aim of this study was to evaluate the in vitro and in vivo efficacy of a new combination of oral cephalosporins and amoxicillin/clavulanate in treatment of ESBL-EC. Methods: A total of 150 ESBL-EC samples were collected over 1 year from two referral centers. Synergistic studies of cephalosporins and amoxicillin/clavulanate were performed in vitro using disk approximation and disk replacement methods. Combination treatment was assessed in vivo on 20 ESBL-EC urinary tract infection (UTI) patients. Results: ESBL-EC isolates were confirmed in 150 patients with a mean age of 46.67 years, 75.2% of them being women. Antibiotic susceptibility testing of isolates indicated high resistance rate to oral antibiotics. The frequency of positive synergy and mean distance of synergy between cephalosporins and amoxicillin/clavulanate was significantly higher with cefotaxime and cefixime compared with cefpodoxime, cefdinir, and ceftazidime using disk approximation and disk replacement methods (p < 0.05). Addition of amoxicillin/clavulanate enhanced the susceptibility rate with cefixime from 8.6% to 86.3%, significantly higher than with other cephalosporins (p < 0.0005). Cefixime and amoxicillin/clavulanate synergy was not affected by age, gender, hospital, department, sample type, or bacterial load. Eighteen of 20 ESBL-EC-positive UTI patients had a positive in vitro synergy test and complete clinical and microbiological resolution after completion of cefixime and amoxicillin/clavulanate oral treatment course. Conclusions: Cefixime and amoxicillin/clavulanate combination therapy could be an effective oral outpatient treatment option for ESBL-EC. In vitro synergistic testing is simple and predictive of successful treatment.

Study of class 1 integrons in multidrug-resistant uropathogenic Escherichia coli isolated from different hospitals in Karachi

OBJECTIVES

Escherichia coli is the key pathogen in the family producing ESBL (extended spectrum β-lactamase) and associated with community-acquired infections. Therefore, this study was planned to determine the antibiotic susceptibility pattern of uropathogenic E. coli, prevalence of the ESBL gene group and class 1 integrons.

MATERIALS AND METHODS

Clinical isolates of uropathogenic E. coli were isolated from different hospitals of Karachi. Antibiotic susceptibility test was performed by Kirby-Bauer Methods. Presence of β- lactamases genes (CTX, TEM, and SHV) and integron 1 were identified by polymerase chain reaction (PCR).

RESULTS

Out of 500, 105 isolates were identified as multi-drug resistant (MDR) uropathogenic E. coli. The subject MDR isolates showed the highest resistance to aztreonam, amoxil/ clavulanic acid, ampicillin, cotrimoxazole, ceftriaxone, cefipime, and cefuroxime. Genetic analysis showed that the majority of the MDR E. coli carry CTX M1 (57.1%) followed by TEM (33.3%) and SHV (9.5%). Moreover, 79% of MDR E. coli harbored class 1 integrons, whereas all three conserved genes for class 1 integrons were present in 58% of MDR E. coli.

CONCLUSION

This study is helpful to provide information regarding the antibiotic susceptibility pattern, distribution ESBLs and class 1 integrons among uropathogenic E. coli.

Extended-spectrum β-lactamase-producing bacteria caused less than 5% of urinary tract infections in a paediatric emergency centre

AIM

The last decade has seen a significant increase in extended-spectrum β-lactamase (ESBL) secreting organisms responsible for paediatric urinary tract infections (UTIs), particularly in community-acquired infections. These expose patients to the risks of antibiotic treatment failure and renal scarring. This prospective study examined the prevalence and risk factors of febrile ESBL UTIs and their treatment in the paediatric emergency department of a university hospital.

METHODS

In this prospective observational study, all children from 0 to 16 years of age with febrile UTIs were included from May 2012 to April 2013. Cases with and without ESBL involvement were compared.

RESULTS

Of the 474 diagnosed febrile UTIs, 22 (4.6%) with a 95% confidence interval (95% CI) of 2.9-6.9 were due to an ESBL-producing organism. Escherichia coli was found in 85% of cases. Significant odds ratios (OR) for ESBL urinary tract infections were prior hospitalisation (OR 4.1, 95% CI 1.6-10.8), urinary tract abnormalities (OR 3.9, 95% CI 1.5-10.2) and previous antibiotic treatment (OR 3.1, 95% CI 1.2-8.8). All ESBL urinary tract infections had positive outcomes.

CONCLUSION

The prevalence of febrile ESBL urinary tract infections was less than 5% in a paediatric emergency department. This low rate was not high enough to justify changing our guidelines.