The combination of pivampicillin and pivmecillinam versus pivampicillin alone in the treatment of acute pyelonephritis

Intravenous mecillinam compared with other β-lactams as targeted treatment for Escherichia coli or Klebsiella spp. bacteraemia with urinary tract focus

BACKGROUND

Mecillinam (amdinocillin) is active against Gram-negative bacteria. Clinical data on the efficacy of IV mecillinam for severe urinary tract infections is sparse.

OBJECTIVES

To assess the effectiveness of targeted IV mecillinam compared with other β-lactams for bacteraemia with Escherichia coli and Klebsiella spp. and a urinary tract focus.

PATIENTS AND METHODS

We performed a retrospective cohort study at five university hospitals in the Capital Region of Denmark from 1 January 2012 to 31 December 2017. We used Cox proportional hazard regression to compare the primary composite endpoint (all-cause mortality or bacteraemia recurrence within 30 days) between patients treated with mecillinam versus ampicillin, cefuroxime, piperacillin/tazobactam and meropenem.

RESULTS

We included 1129 patients in the primary analysis, of which 146 were given IV mecillinam as targeted treatment. We found no significant difference in the primary endpoint between patients treated with mecillinam versus ampicillin and cefuroxime, but found a higher risk for the primary endpoint in the piperacillin/tazobactam and meropenem groups, with adjusted HRs of 2.22 (95% CI 1.24-3.97, P < 0.01) and 2.48 (95% CI 1.04-5.93, P = 0.04), respectively, compared with mecillinam.

CONCLUSIONS

The results of this study suggest that IV mecillinam may be a suitable targeted treatment for bacteraemia with a urinary tract focus. However, these results need confirmation by randomized controlled studies.

Treatment of infections caused by multidrug-resistant Gram-negative bacteria: report of the British Society for Antimicrobial Chemotherapy/Healthcare Infection Society/British Infection Association Joint Working Party

The Working Party makes more than 100 tabulated recommendations in antimicrobial prescribing for the treatment of infections caused by multidrug-resistant (MDR) Gram-negative bacteria (GNB) and suggest further research, and algorithms for hospital and community antimicrobial usage in urinary infection. The international definition of MDR is complex, unsatisfactory and hinders the setting and monitoring of improvement programmes. We give a new definition of multiresistance. The background information on the mechanisms, global spread and UK prevalence of antibiotic prescribing and resistance has been systematically reviewed. The treatment options available in hospitals using intravenous antibiotics and in primary care using oral agents have been reviewed, ending with a consideration of antibiotic stewardship and recommendations. The guidance has been derived from current peer-reviewed publications and expert opinion with open consultation. Methods for systematic review were NICE compliant and in accordance with the SIGN 50 Handbook; critical appraisal was applied using AGREE II. Published guidelines were used as part of the evidence base and to support expert consensus. The guidance includes recommendations for stakeholders (including prescribers) and antibiotic-specific recommendations. The clinical efficacy of different agents is critically reviewed. We found there are very few good-quality comparative randomized clinical trials to support treatment regimens, particularly for licensed older agents. Susceptibility testing of MDR GNB causing infection to guide treatment needs critical enhancements. Meropenem- or imipenem-resistant Enterobacteriaceae should have their carbapenem MICs tested urgently, and any carbapenemase class should be identified: mandatory reporting of these isolates from all anatomical sites and specimens would improve risk assessments. Broth microdilution methods should be adopted for colistin susceptibility testing. Antimicrobial stewardship programmes should be instituted in all care settings, based on resistance rates and audit of compliance with guidelines, but should be augmented by improved surveillance of outcome in Gram-negative bacteraemia, and feedback to prescribers. Local and national surveillance of antibiotic use, resistance and outcomes should be supported and antibiotic prescribing guidelines should be informed by these data. The diagnosis and treatment of both presumptive and confirmed cases of infection by GNB should be improved. This guidance, with infection control to arrest increases in MDR, should be used to improve the outcome of infections with such strains. Anticipated users include medical, scientific, nursing, antimicrobial pharmacy and paramedical staff where they can be adapted for local use.

Mecillinam for the treatment of acute pyelonephritis and bacteremia caused by Enterobacteriaceae: a literature review

Purpose

The pharmacokinetic properties of mecillinam (MEC) for urinary tract infections are excellent, and the resistance rate in Enterobacteriaceae is low compared to other recommended antibiotics. The oral prodrug pivmecillinam (P-MEC) has been used successfully as first choice for cystitis in the Nordic countries for many years. Norwegian and Danish guidelines also recommend P-MEC for acute uncomplicated pyelonephritis (AUP) and intravenous (IV) MEC for suspected urosepsis (only in Denmark). Here, we wish to present an updated investigation on the clinical data behind these recommendations together with sparse but more current clinical data.

Methods

Prospective clinical trials evaluating MEC as monotherapy or in polytherapy with one other beta-lactam (mostly ampicillin [AMP]) for pyelonephritis or bacteremia were reviewed. Outcomes of primary interest were clinical and bacteriological success and relapse, respectively. Search databases used were PubMed, Cochrane Library, and Embase.

Results

Twelve clinical studies (1979-2015) were included in this integrated literature review. Clinical success was seen in 38/51 (75%) patients treated with MEC as monotherapy and in 152/164 (93%) patients treated with MEC and one other beta-lactam. Bacteriological success was seen in 35/47 (74%) and 117/167 (70%) patients treated with MEC alone and with one other beta-lactam, respectively. In complicated infections, bacteriological success was much lower. Clinical relapse rate was not well described. Several uropathogenic bacteremia cases were treated successfully with MEC alone (ie, 10/15 [67%] and 13/15 [87%] for clinical and bacteriological success, respectively) or with one other beta-lactam (ie, 57/65 [88%] and 53/63 [84%] for clinical and bacteriological success, respectively). However, data on bacteremia are very sparse. Adverse reactions were few and mild (73/406 [18%]) and primarily seen when AMP was co-administered (69/73 [95%]). No serious adverse reactions were reported.

Conclusion

IV MEC or oral P-MEC for 14 days may be suitable for the treatment of AUP and pediatric pyelonephritis. Randomized controlled trials using a single standardized dose of P-MEC compared to other current recommendations are warranted. Similarly, more evidence is required before MEC should be recommended for bacteremia or sepsis due to Enterobacteriaceae.

Top Questions in Uncomplicated, Non-Staphylococcus aureus Bacteremia

The Infectious Diseases Society of America infection-specific guidelines provide limited guidance on the management of focal infections complicated by secondary bacteremias. We address the following 3 commonly encountered questions and management considerations regarding uncomplicated bacteremia not due to Staphylococcus aureus: the role and choice of oral antibiotics focusing on oral beta-lactams, the shortest effective duration of therapy, and the role of repeat blood cultures.

Ciprofloxacin for 7 days versus 14 days in women with acute pyelonephritis: a randomised, open-label and double-blind, placebo-controlled, non-inferiority trial

BACKGROUND

Acute pyelonephritis is a common infection in adult women, but there is a paucity of controlled trials of its treatment and the optimum duration of antibiotic treatment has not been properly defined. We compared the efficacy of ciprofloxacin for 7 days and 14 days in women with community-acquired acute pyelonephritis.

METHODS

In a prospective, non-inferiority trial undertaken at 21 centres of infectious diseases in Sweden, women (aged ≥18 years) who were not pregnant and had a presumptive diagnosis of acute pyelonephritis were randomly assigned to oral treatment with ciprofloxacin 500 mg twice daily for 7 days or 14 days. The first week was open label. A computer-generated randomisation list in block sizes of two was used for treatment allocation in a 1:1 ratio. The study was double-blind and placebo-controlled during the second week of treatment, which was either continuation of ciprofloxacin 500 mg or placebo tablets twice daily according to the randomisation code. Patients, carers, site investigators, and trial coordinating centre staff were masked to group assignment. The primary endpoint was the clinical and bacteriological outcome 10-14 days after completion of treatment with active drug. Analysis was by per protocol. This trial is registered with EudraCT, number 2005-004992-39, and ClinicalTrials.gov, number ISRCTN73338924.

FINDINGS

126 of 248 patients were randomly assigned to 7 days and 122 to 14 days of ciprofloxacin. 73 and 83 patients, respectively, were analysed. Short-term clinical cure occurred in 71 (97%) patients treated with ciprofloxacin for 7 days and 80 (96%) treated for 14 days (difference -0·9%; 90% CI -6·5 to 4·8; p=0·004; non-inferiority test). Cumulative efficacy at long-term follow-up was 93% in each group (68 of 73 vs 78 of 84; -0·3%; -7·4 to 7·2; p=0·015). Both regimens were well tolerated. Two patients discontinued ciprofloxacin because of myalgia with 7 days of treatment and itching exanthema with 14 days. Four (5%) of 86 patients assigned to 7 days of treatment who complied with study criteria and six (6%) of 93 assigned to 14 days reported an adverse event after the first week of treatment that was possibly or probably related to the study drug. In those assigned to 7 days, no patient had mucosal candida infection after the first week versus five treated for 14 days (p=0·036).

INTERPRETATION

Our results show that acute pyelonephritis in women, including older women and those with a more severe infection, can be treated successfully and safely with oral ciprofloxacin for 7 days. Short courses of antibiotics should be favoured in an era of increasing resistance.

FUNDING

Swedish Strategic Programme against Antibiotic Resistance (Strama).

One or three weeks' treatment of acute pyelonephritis? A double-blind comparison, using a fixed combination of pivampicillin plus pivmecillinam

The clinical and bacteriological effects of 1 and 3 weeks' pivampicillin plus pivmecillinam treatment were compared in a double-blind, randomized study of patients with acute pyelonephritis. Three weeks after the end of active treatment, clinical success was seen in 29 (91%) of the 32 patients on 1-week treatment, compared with 28 (97%) of the 29 patients treated for 3 weeks. Bacteriological success was seen in only nine (28%) patients in the 1-week group vs. 20 (69%) in the 3-week group (p = 0.004). This difference was mainly due to a large number of relapses of lower urinary tract infection in the 1-week group. Even in uncomplicated cases, the bacteriological result of the 1-week treatment was unsatisfactory. Side-effects were more common in the 3-week treatment group. In conclusion, 1-week treatment of patients with acute pyelonephritis is too short. Three weeks' treatment is effective in uncomplicated cases, but even longer treatment or low-dose prophylaxis is indicated in certain patients with predisposing factors.

Complete genome sequence of uropathogenic Proteus mirabilis, a master of both adherence and motility

The gram-negative enteric bacterium Proteus mirabilis is a frequent cause of urinary tract infections in individuals with long-term indwelling catheters or with complicated urinary tracts (e.g., due to spinal cord injury or anatomic abnormality). P. mirabilis bacteriuria may lead to acute pyelonephritis, fever, and bacteremia. Most notoriously, this pathogen uses urease to catalyze the formation of kidney and bladder stones or to encrust or obstruct indwelling urinary catheters. Here we report the complete genome sequence of P. mirabilis HI4320, a representative strain cultured in our laboratory from the urine of a nursing home patient with a long-term (> or =30 days) indwelling urinary catheter. The genome is 4.063 Mb long and has a G+C content of 38.88%. There is a single plasmid consisting of 36,289 nucleotides. Annotation of the genome identified 3,685 coding sequences and seven rRNA loci. Analysis of the sequence confirmed the presence of previously identified virulence determinants, as well as a contiguous 54-kb flagellar regulon and 17 types of fimbriae. Genes encoding a potential type III secretion system were identified on a low-G+C-content genomic island containing 24 intact genes that appear to encode all components necessary to assemble a type III secretion system needle complex. In addition, the P. mirabilis HI4320 genome possesses four tandem copies of the zapE metalloprotease gene, genes encoding six putative autotransporters, an extension of the atf fimbrial operon to six genes, including an mrpJ homolog, and genes encoding at least five iron uptake mechanisms, two potential type IV secretion systems, and 16 two-component regulators.

Development of an intranasal vaccine to prevent urinary tract infection by Proteus mirabilis

Proteus mirabilis commonly infects the complicated urinary tract and is associated with urolithiasis. Stone formation is caused by bacterial urease, which hydrolyzes urea to ammonia, causing local pH to rise, and leads to the subsequent precipitation of magnesium ammonium phosphate (struvite) and calcium phosphate (apatite) crystals. To prevent these infections, we vaccinated CBA mice with formalin-killed bacteria or purified mannose-resistant, Proteus-like (MR/P) fimbriae, a surface antigen expressed by P. mirabilis during experimental urinary tract infection, via four routes of immunization: subcutaneous, intranasal, transurethral, and oral. We assessed the efficacy of vaccination using the CBA mouse model of ascending urinary tract infection. Subcutaneous or intranasal immunization with formalin-killed bacteria and intranasal or transurethral immunization with purified MR/P fimbriae significantly protected CBA mice from ascending urinary tract infection by P. mirabilis (P < 0.05). To investigate the potential of MrpH, the MR/P fimbrial tip adhesin, as a vaccine, the mature MrpH peptide (residues 23 to 275, excluding the signal peptide), and the N-terminal receptor-binding domain of MrpH (residues 23 to 157) were overexpressed as C-terminal fusions to maltose-binding protein (MBP) and purified on amylose resins. Intranasal immunization of CBA mice with MBP-MrpH (residues 23 to 157) conferred effective protection against urinary tract infection by P. mirabilis (P < 0.002).

Serum immunoglobulin response and protection from homologous challenge by Proteus mirabilis in a mouse model of ascending urinary tract infection

We tested the hypothesis that experimental Proteus mirabilis urinary tract infection in mice would protect against homologous bladder rechallenge. Despite production of serum immunoglobulin G (IgG) and IgM (median titers of 1:320 and 1:80, respectively), vaccinated (infected and antibiotic-cured) mice did not show a decrease in mortality upon rechallenge; the survivors experienced only modest protection from infection (mean log(10) number of CFU of P. mirabilis Nal(r) HI4320 per milliliter or gram in vaccinated mice versus sham-vaccinated mice: urine, 100-fold less [3.5 versus 5.5; P = 0.13]; bladder, 100-fold less [3.1 versus 5.1; P = 0.066]; kidneys, 40-fold less [2.7 versus 4.3; P = 0.016]). Western blots using protein from the wild-type strain and isogenic mutants demonstrated antibody responses to MR/P and PMF fimbriae and flagella. There was no correlation between serum IgG or IgM levels and protection from mortality or infection. There was a trend toward elevated serum IgA titers and protection from subsequent challenge (P >/= 0.09), although only a few mice developed significant serum IgA levels. We conclude that prior infection with P. mirabilis does not protect significantly against homologous challenge.

The expression of nonagglutinating fimbriae and its role in Proteus mirabilis adherence to epithelial cells

Proteus mirabilis is a common causative agent of human urinary tract infections, especially in catheterized patients and in those patients with structural abnormalities of the urinary tract. In addition to the production of hemolysin and urease, fimbriae-mediated adherence to uroepithelial cells and kidney epithelium may be essential for virulence of P. mirabilis. A single P. mirabilis strain is capable of expressing several morphologically distinct fimbrial species, which can each be favoured by specific in vitro growth conditions. The fimbrial species reported to date include mannose-resistant/Proteus-like fimbriae, ambient temperature fimbriae, P. mirabilis fimbriae, and nonagglutinating fimbriae (NAF). Here, using intact bacteria or purified NAF as immunogens, we have generated the first reported NAF-specific monoclonal antibodies (mAbs). Bacteria expressing NAF as their only fimbrial species adhered strongly to a number of cell lines in vitro, including uroepithelial cell lines. Binding of P. mirabilis was markedly reduced following preincubation with NAF-specific mAbs and Fab fragments. The presence of NAF with highly conserved N-terminal sequences on all P. mirabilis strains so far examined, combined with the ability of both anti-NAF mAbs and purified NAF molecules to inhibit P. mirabilis adherence in vitro, suggests that NAF may contribute to the pathogenesis of P. mirabilis.

Aminoglycosides do not improve the efficacy of cephalosporins for treatment of acute pyelonephritis in women

A prospective, coordinated, randomized multicentre trial was conducted to determine whether tobramycin 160 mg intravenously (i.v.) once daily for 2 days would improve the efficacy of cefotaxime 1 g i.v. twice daily for 2 days followed by a 10-day course of oral cefadroxil 1 g twice daily, in the treatment of community-acquired acute pyelonephritis in women. Of 73 patients enrolled in the study, 51 could be evaluated according to the protocol. There were no significant differences in bacteriological cure rates between the combined treatment with tobramycin/cefotaxime and cefotaxime alone, either at short-term follow-up (63.0% vs 59.1%; 95% confidence interval (CI) for difference in proportions -23.4% to 31.2%), or up to 7 weeks after cessation of treatment (42.9% vs 52.2%; 95% CI, -18.0% to 36.6%). A modified intention-to-treat analysis showed no difference in clinical efficacy between the two regimens (68.6% vs 69.2%; 95% CI, -22.9% to 24.1%). Tobramycin seemed to enhance the resolution of inflammation by a more rapid decline in C-reactive protein levels. The high recurrence rates after treatment with beta-lactam antibiotics in this and previous studies of acute pyelonephritis may be explained by adverse ecological effects rather than failure to eradicate the infection.

Expression of a nonagglutinating fimbria by Proteus mirabilis

We have clarified growth conditions and isolation strategies for the nonagglutinating fimbriae from Proteus mirabilis. Nonagglutinating fimbriae were expressed by all P. mirabilis strains we examined, and the major subunit proteins, which ranged from 23 to 29 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, had highly conserved N-terminal sequences.

Proteus mirabilis flagella and MR/P fimbriae: isolation, purification, N-terminal analysis, and serum antibody response following experimental urinary tract infection

Urinary tract infection with Proteus mirabilis may lead to serious complications, including cystitis, acute pyelonephritis, fever, bacteremia, and death. In addition to the production of hemolysin and the enzyme urease, fimbriae and flagellum-mediated motility have been postulated as virulence factors for this species. We purified mannose-resistant/proteuslike (MR/P) fimbriae and flagella from strains CFT322 and HU2450, respectively. Electron microscopy revealed highly concentrated preparations of fimbriae and flagella. Fimbrial and flagellar structural subunits were estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be 18.5 and 41 kDa, respectively. N-terminal sequencing revealed that 10 of the first 20 amino acids of the major MR/P subunit matched the sequence of the P. mirabilis uroepithelial cell adhesin N terminus and 11 of 20 amino acids matched the predicted amino acid sequence of the Escherichia coli P fimbriae structural subunit, PapA. In addition, 90 and 80% homologies were found between the first 20 amino acids of P. mirabilis flagellin and those of Salmonella typhimurium phase-1 flagellin and the E. coli hag gene product, respectively. An enzyme-linked immunosorbent assay using purified antigens showed a strong reaction between the MR/P fimbriae or flagella and sera of CBA mice challenged transurethrally with P. mirabilis. A possible role for MR/P fimbriae in the pathogenesis of urinary tract infection is supported by (i) a strong immune response to the antigen in experimentally infected animals, (ii) amino acid sequence similarity to other enteric surface structure, and (iii) our previously reported observation that MR/P fimbriae are expressed preferentially as the sole fimbrial type in human pyelonephritis isolates.

Cytotoxicity of the HpmA hemolysin and urease of Proteus mirabilis and Proteus vulgaris against cultured human renal proximal tubular epithelial cells

Proteus mirabilis, a common agent of nosocomially acquired and catheter-associated bacteriuria, can cause acute pyelonephritis. In ascending infections, bacteria colonize the bladder and ascend the ureters to the proximal tubules of the kidney. We postulate that Proteus species uses the HpmA hemolysin and urease to elicit tissue damage that allows entry of these bacteria into the kidney. To study this interaction, strains of Proteus mirabilis and P. vulgaris and their isogenic hemolysin-negative (hpmA) or isogenic urease-negative (ureC) constructs were overlaid onto cultures of human renal proximal tubular epithelial cells (HRPTEC) isolated from kidneys obtained by immediate autopsy. Cytotoxicity was measured by release of soluble lactate dehydrogenase (LDH). Two strains of P. mirabilis inoculated at 10(6) CFU caused a release of 80% of total LDH after 6 h, whereas pyelonephritogenic hemolytic Escherichia coli CFT073 released only 25% at 6 h (P less than 0.012). Ten P. mirabilis isolates and five P. vulgaris isolates were all hemolytic and cytotoxic and produced urease which was induced by urea. The HpmA hemolysin is apparently responsible for the majority of cytotoxicity in vitro since the hemolysin-negative (hpmA) mutants of P. mirabilis and P. vulgaris were significantly less cytotoxic than wild-type strains. P. mirabilis WPM111 (hemolysin negative) was used to test the effect of urease-catalyzed urea hydrolysis on HRPTEC viability. In the presence of 50 mM urea, WPM111 caused the release of 42% of LDH versus 1% at 6 h in the absence of substrate (P = 0.003). We conclude that the HpmA hemolysin of Proteus species acts as a potent cytotoxin against HRPTEC. In addition, urease apparently contributes to this process when substrate urea is available.

Randomised double-blind study of norfloxacin and cefadroxil in the treatment of acute pyelonephritis

In a coordinated, double-blind multi-centre trial, adults with symptoms of acute pyelonephritis were randomly assigned to receive a two-week course of oral treatment with either 400 mg norfloxacin twice daily or 1 g cefadroxil twice daily. Of 197 patients enrolled in the study, 140 could be evaluated for drug efficacy and 193 for drug safety. Norfloxacin gave a significantly higher bacteriological cure rate than cefadroxil, both at 3 to 10 days (98% versus 65%; p less than 0.0001; 95% confidence interval (CI) for difference in proportions 21-46%) and up to eight weeks (87% versus 48%; p less than 0.0001; 95% CI 25-54%) after cessation of treatment. The differences between the two regimens were most pronounced in men and in patients with complicating factors such as diabetes mellitus and urinary tract abnormalities. The clinical response during treatment did not differ between the two groups, but symptomatic recurrences at follow-up were more common in the cefadroxil group (28% versus 3%; p less than 0.0001; 95% CI 14-36%). Adverse events were more often reported by patients receiving cefadroxil (39% versus 22%; p = 0.011; 95% CI 4-30%) and consisted mainly of gastrointestinal disturbances and vulvo-vaginitis. In terms of bacteriological and clinical efficacy and safety, a two-week course of norfloxacin was superior to a two-week course of cefadroxil for oral treatment of community-acquired acute pyelonephritis.