Best in class: a good principle for antibiotic usage to limit resistance development?

Gallic Acid Potentiates the Antimicrobial Activity of Tulathromycin Against Two Key Bovine Respiratory Disease (BRD) Causing-Pathogens

Bovine respiratory disease (BRD) is the most common infectious disease in dairy and beef cattle. It is associated with significant morbidity and mortality and causes a huge economic loss each year. In western Canada, a one-time injection of tulathromycin is commonly used as a metaphylactic procedure to reduce BRD incidence and eliminate potential BRD outbreak. With increased global concern on antimicrobial usage in dairy and beef products and bacterial resistance to antimicrobials, it is important to develop a novel strategy to eliminate the usage or decrease the dosage of antimicrobials. In this study, we showed that gallic acid was active against both Mannheimia haemolytica and Pasteurella multocida, two key BRD associated-pathogens, with the minimum inhibitory concentration (MIC) measured at 250 and 500 μg/mL, respectively. Co-administration of tulathromycin and gallic acid exhibited a strong additive or weak synergistic effect toward both M. haemolytic and P. multocida. Tulathromycin, gallic acid and their combination were also effective against the mixed culture of M. haemolytic and P. multocida. Furthermore, we showed that pre-exposure to tulathromycin generated bacterial resistance to the antimicrobial in M. haemolytica but not in P. multocida.

OXA β-lactamases

The OXA β-lactamases were among the earliest β-lactamases detected; however, these molecular class D β-lactamases were originally relatively rare and always plasmid mediated. They had a substrate profile limited to the penicillins, but some became able to confer resistance to cephalosporins. From the 1980s onwards, isolates of Acinetobacter baumannii that were resistant to the carbapenems emerged, manifested by plasmid-encoded β-lactamases (OXA-23, OXA-40, and OXA-58) categorized as OXA enzymes because of their sequence similarity to earlier OXA β-lactamases. It was soon found that every A. baumannii strain possessed a chromosomally encoded OXA β-lactamase (OXA-51-like), some of which could confer resistance to carbapenems when the genetic environment around the gene promoted its expression. Similarly, Acinetobacter species closely related to A. baumannii also possessed their own chromosomally encoded OXA β-lactamases; some could be transferred to A. baumannii, and they formed the basis of transferable carbapenem resistance in this species. In some cases, the carbapenem-resistant OXA β-lactamases (OXA-48) have migrated into the Enterobacteriaceae and are becoming a significant cause of carbapenem resistance. The emergence of OXA enzymes that can confer resistance to carbapenems, particularly in A. baumannii, has transformed these β-lactamases from a minor hindrance into a major problem set to demote the clinical efficacy of the carbapenems.

The characterization and antibiotic resistance profiles of clinical Escherichia coli O25b-B2-ST131 isolates in Kuwait

Background

Escherichia coli O25b-B2-ST131 are considered virulent extra-intestinal pathogens causing serious clinical complications such as urinary tract infection and bacteraemia. Our main objectives in this study were to characterise the multi-drug resistant (MDR) isolates of this lineage in Kuwait, and to demonstrate whether reduced susceptibility is spread clonally.

Results

A subset of 83 (10%) non-duplicate and non-selective E. coli O25b-B2-ST131 out of 832 MDR E. coli was identified and collected. Minimum inhibitory concentrations of the isolates were determined and pulsed-field gel electrophoresis was used for typing.

The majority (95.2%) of the 83 E. coli O25b-B2-ST131 harboured at least one bla gene with bla_CTX-M-15 being the most prevalent. bla_CTX-M-2 was present in one isolate. Also one isolate harboured bla_CTX-M-56, qnrB1 and bla_CMY-2 genes and carried IncF1 plasmids of about 97 kb and160 kb. qnrB and qnrS were found in 8 other bla_CTX-M-15 containing isolates. The bla_NDM, bla_IMP, bla_VIM and qnrA were not detected, however, the bla_OXA-48 was present in two (2.4%).

Conclusions

The majority of isolates harbouring qnr genes demonstrated relatedness (≥85%) by PFGE. However, the diversity in PFGE profiles for the other MDR isolates reflected the changes in population genetics of E. coli O25b-B2-ST131. We identified for the first time the appearance of bla_CTX-M-2 in the Middle East and bla_CTX-M-56 outside the Latin American countries. The isolate harbouring bla_CTX-M-56 also contained qnrB1 and bla_CMY-2 genes and carried IncF1 plasmids. The appearance of a highly virulent E. coli O25b-ST131 that is resistant to penicillins, most cephalosproins, β-lactamase inhibitors as well as fluoroquinolones is a cause for concern.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-014-0214-6) contains supplementary material, which is available to authorized users.

The consequences of generic marketing on antibiotic consumption and the spread of microbial resistance: the need for new antibiotics

In both human and veterinary medicine, it has been shown that flooding the market with different generics and/or 'me-too' branded drugs has increased overall antibiotic consumption correlating with the emergence and spread of bacterial resistance to antibiotics. Another possible undesirable consequence of the promotion of generics is the promotion of an economic incentive that encourages the use of old drug products with very poor oral bioavailability, marketed with historical dosage regimens and extensively excreted in the environment. What veterinary medicine rather needs is new innovative and 'ecofriendly' antibiotics to actually enforce a more prudent use of antibiotics. For a pharmaceutical company, generics are inexpensive to manufacture and on a short-term basis, the generic market is very appealing. However, on a long-term basis, this marketing orientation provides a disincentive to the development of new and innovative products that will be required to meet the therapeutic needs of the veterinary community while being consistent with public health concerns. Indeed, for veterinary medicine, the key issue surrounding antibiotics is public health. It is the opinion of the authors that veterinary antibiotics and/or veterinary drug formulations should be innovative in terms of selectivity (no or minimal impact on the commensal gut flora), biodegradable (with minimal environmental disruption), and more expensive, with a strictly regulated market rather than unselective, cheap, and freely available drugs.

Evaluation of doripenem utilization and susceptibilities at a large urban hospital

BACKGROUND

Bacterial resistance presents a constant challenge in the treatment of hospitalized patients, particularly with Gram-negative infections. Carbapenems have an important role in the treatment of resistant nosocomial organisms. Doripenem, a recently approved carbapenem, has shown efficacy in clinical trials, but there is little published data on utilization in a general patient population.

OBJECTIVE

The clinical utilization of doripenem in a general adult inpatient population was evaluated during a carbapenem formulary conversion.

SETTING

A 706-bed acute care tertiary hospital serving an urban community.

METHODS

After formulary conversion to doripenem, the first 100 patients to receive doripenem were included in the analysis. Baseline characteristics were recorded for each patient, along with indication for treatment, prescribing physician, dose and frequency of doripenem and duration of treatment. Patients were monitored for adverse reactions to doripenem. Bacterial culture results were recorded. For positive cultures, doripenem susceptibility was determined by Etest. Patients were followed until discontinuation of antibiotic therapy, discharge or death to determine treatment outcomes. Successful treatment was defined as clinical or microbiological cure, while patients with infection-related mortality or requiring subsequent antibiotics for the index infection were considered treatment failure.

MAIN OUTCOME MEASURES

Clinical utilization of doripenem, including indications and doses used.

RESULTS

Doripenem treatment was recorded in 102 patients. The most common indications for treatment were pneumonia and sepsis. The majority of doripenem orders were written by Infectious Disease or Pulmonology Services. Forty-nine patients were treated successfully with doripenem and six patients experienced treatment failure. The remainder of patients were not evaluable by predefined outcomes criteria. Adverse events were reported in eight patients and included acute renal failure, Clostridium difficile-associated diarrhea and seizures. Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa were the most common organisms in culture results. Doripenem demonstrated in vitro activity against 81% of all organisms and susceptibility results had >90% correlation with meropenem and imipenem susceptibilities.

CONCLUSION

In our limited sample size, doripenem was safe and effective against various types of infections in a general inpatient population with similar bacterial susceptibilities to other cabapenems. Doripenem was utilized for appropriate indications, but doses were frequently outside the manufacturers labeling. Adverse events were uncommon, and no serious adverse events were directly associated with doripenem treatment.

Insights into antifolate activity of phytochemicals against Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic drug resistant pathogen. Drug interaction studies for phytochemicals (protocatechuic acid (PA), gallic acid (GA), quercetin (QUER), and myricetin (MYR)) in combination with antifolates (sulfamethoxazole (SMX) and trimethoprim (TMP)) are presented. Our results show that the combinations of SMX and phytochemicals are synergistic, whereas TMP in combination with phytochemicals results in additive mode of interaction. Molecular docking of phytochemicals in the active site of modeled P. aeruginosa dihydrofolate reductase (DHFR), an important enzyme in the folic acid biosynthesis pathway, shows that the phytochemicals QUER and MYR dock in the active site of P. aeruginosa DHFR with promoted binding at the NADP site, PA, and GA dock in the active site of P. aeruginosa DHFR with promoted binding at the folate binding site. Possible mode of action of these phytochemicals as anti-DHFR compounds in this bacterium is suggested. Taken together, the above findings provide novel insights to mode of interactions of these phytochemicals with antibiotics and may have significance as prospective leads in the development of antipseudomonal drug developments.

Activity of Chitosans in combination with antibiotics in Pseudomonas aeruginosa

Chitosan and its derivative water soluble Chitosan oligosaccharide are used in a variety of applications in pharmaceutical preparations. In this study, 2 wild (ATCC 15729 and PAO1) and 2 mutant strains (PT121 and PT149) of P. aeruginosa are investigated for drug-drug interactions in vitro. 10 antimicrobial agents (antibiotics) are combined with different degree of deacetylated Chitosans and Chitosan oligosaccharide. All the chitosans show synergistic activity with sulfamethoxazole, a sulfonamide antimicrobial agent. It is interesting to observe that the MIC value for the MexEF-OprN overexpressing mutant strain of P. aeruginosa is 5 fold higher than the other strains under investigation suggesting a possible role of this efflux pump in Sulfamethoxazole efflux. The findings suggest on the use of chitosans as enhancing agent in combination with antibiotics in pharmaceutical preparations.

Meropenem: a review of its use in the treatment of serious bacterial infections

Meropenem (Merrem, Meronem) is a broad-spectrum antibacterial agent of the carbapenem family, indicated as empirical therapy prior to the identification of causative organisms, or for disease caused by single or multiple susceptible bacteria in both adults and children with a broad range of serious infections. Meropenem is approved for use in complicated intra-abdominal infection (cIAI), complicated skin and skin structure infection (cSSSI) and bacterial meningitis (in paediatric patients aged > or = 3 months) in the US, and in most other countries for nosocomial pneumonia, cIAI, septicaemia, febrile neutropenia, cSSSI, bacterial meningitis, complicated urinary tract infection (UTI), obstetric and gynaecological infections, in cystic fibrosis patients with pulmonary exacerbations, and for the treatment of severe community-acquired pneumonia (CAP). Meropenem has a broad spectrum of in vitro activity against Gram-positive and Gram-negative pathogens, including extended-spectrum beta-lactamase (ESBL)- and AmpC-producing Enterobacteriaceae. It has similar efficacy to comparator antibacterial agents, including: imipenem/cilastatin in cIAI, cSSSI, febrile neutropenia, complicated UTI, obstetric or gynaecological infections and severe CAP; clindamycin plus tobramycin or gentamicin in cIAI or obstetric/gynaecological infections; cefotaxime plus metronidazole in cIAI; cefepime and ceftazidime plus amikacin in septicaemia or febrile neutropenia; and ceftazidime, clarithromycin plus ceftriaxone or amikacin in severe CAP. Meropenem has also shown similar efficacy to cefotaxime in paediatric and adult patients with bacterial meningitis, and to ceftazidime when both agents were administered with or without tobramycin in patients with cystic fibrosis experiencing acute pulmonary exacerbations. Meropenem showed greater efficacy than ceftazidime or piperacillin/tazobactam in febrile neutropenia, and greater efficacy than ceftazidime plus amikacin or tobramycin in patients with nosocomial pneumonia. Meropenem is well tolerated and has the advantage of being suitable for administration as an intravenous bolus or infusion. Its low propensity for inducing seizures means that it is suitable for treating bacterial meningitis and is the only carbapenem approved in this indication. Thus, meropenem continues to be an important option for the empirical treatment of serious bacterial infections in hospitalized patients.