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Antibiotics, Volume 3, Issue 3 (September 2014), Pages 244-460

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Editorial

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Open AccessEditorial Urinary Tract Infections
Antibiotics 2014, 3(3), 375-377; doi:10.3390/antibiotics3030375
Received: 16 July 2014 / Accepted: 23 July 2014 / Published: 14 August 2014
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Abstract
Urinary tract infections (UTI) are among the most frequently acquired infections in the community, but also in hospitals and other health care institutions, causing a huge amount of antibiotic consumption. During the last decade we have seen significant changes in the field of
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Urinary tract infections (UTI) are among the most frequently acquired infections in the community, but also in hospitals and other health care institutions, causing a huge amount of antibiotic consumption. During the last decade we have seen significant changes in the field of urinary tract infections regarding causative pathogens and antibiotic treatment calling for an update of current trends. The worldwide increase of uropathogens resistant to former first line antibiotics, such as cotrimoxazole, fluoroquinolones and cephalosporins, has had detrimental consequences not only for treatment but also for prophylaxis of infectious complications after urological interventions. A paradigm shift concerning asymptomatic bacteriuria has had a great impact on the definition and management of UTIs today [1–4]. [...] Full article
(This article belongs to the Special Issue Antibiotics and Urinary Tract Infections) Print Edition available

Research

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Open AccessArticle Synthesis, Antibacterial Evaluation and QSAR of α-Substituted-N4-Acetamides of Ciprofloxacin and Norfloxacin
Antibiotics 2014, 3(3), 244-269; doi:10.3390/antibiotics3030244
Received: 4 April 2014 / Revised: 19 May 2014 / Accepted: 29 May 2014 / Published: 25 June 2014
Cited by 1 | PDF Full-text (962 KB) | HTML Full-text | XML Full-text
Abstract
Twenty six α-substituted N4-acetamide derivatives of ciprofloxacin (CIPRO) and norfloxacin (NOR) were synthesized and assayed for antibacterial activity against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Bacillus subtilis. The derivatives were primarily more active against Gram-positive bacteria. The
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Twenty six α-substituted N4-acetamide derivatives of ciprofloxacin (CIPRO) and norfloxacin (NOR) were synthesized and assayed for antibacterial activity against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Bacillus subtilis. The derivatives were primarily more active against Gram-positive bacteria. The CIPRO derivatives, CD-7 (Ar = 3-chlorophenyl), CD-9 (Ar = 2-pyrimidyl) and CD-10 (α-phenyl, Ar = 2-pyrimidyl), exhibited lower MIC values, 0.4–0.9 μM, against Staphylococcus aureus than CIPRO, while only compound CD-10 exhibited better activity, 0.1 μM, against Bacillus subtilis than CIPRO. In addition, compounds CD-5 (Ar = 2-methoxyphenyl), CD-6 (α-phenyl, Ar = 2-methoxyphenyl), CD-7 (Ar = 3-Chlorophenyl), CD-8 (α-phenyl, Ar = 3-chlorophenyl) and CD-9 (Ar = 2-pyrimidyl) showed MIC values below 1.0 μM against this strain. The NOR derivatives showed lower activity than NOR itself against Staphylococcus aureus, although ND-6 (α-phenyl, Ar = 2-methoxyphenyl) and ND-7 (Ar = 3-chlorophenyl) showed MIC values less than 2 μM. Two NOR derivatives, ND-7 and ND-6, exhibited MIC values of 0.7 and 0.6, respectively, which were comparable to that of NOR against Bacillus subtilis, while compounds ND-8 (α-phenyl, Ar = 3-chlorophenyl) and ND-10 (α-phenyl, Ar = 2-pyrimidyl) exhibited MIC values less than 1.0 μM against the same strain. QSAR revealed that while polarity is the major contributing factor in the potency against Staphylococcus aureus, it is balanced by lipophilicity and electron density around the acetamide group. On the other hand, electron density around the introduced acetamide group is the major determining factor in the activity against Bacillus subtilis, with a lesser and variable effect for lipophilicity. Full article
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Open AccessArticle Ciprofloxacin Affects Host Cells by Suppressing Expression of the Endogenous Antimicrobial Peptides Cathelicidins and Beta-Defensin-3 in Colon Epithelia
Antibiotics 2014, 3(3), 353-374; doi:10.3390/antibiotics3030353
Received: 27 May 2014 / Revised: 14 July 2014 / Accepted: 15 July 2014 / Published: 25 July 2014
Cited by 1 | PDF Full-text (1727 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Antibiotics exert several effects on host cells including regulation of immune components. Antimicrobial peptides (AMPs), e.g., cathelicidins and defensins display multiple functions in innate immunity. In colonic mucosa, cathelicidins are induced by butyrate, a bacterial fermentation product. Here, we investigated the effect of
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Antibiotics exert several effects on host cells including regulation of immune components. Antimicrobial peptides (AMPs), e.g., cathelicidins and defensins display multiple functions in innate immunity. In colonic mucosa, cathelicidins are induced by butyrate, a bacterial fermentation product. Here, we investigated the effect of antibiotics on butyrate-induced expression of cathelicidins and beta-defensins in colon epithelial cells. Real-time PCR analysis revealed that ciprofloxacin and clindamycin reduce butyrate-induced transcription of the human cathelicidin LL-37 in the colonic epithelial cell line HT-29. Suppression of LL-37 peptide/protein by ciprofloxacin was confirmed by Western blot analysis. Immunohistochemical analysis demonstrated that ciprofloxacin suppresses the rabbit cathelicidin CAP-18 in rectal epithelia of healthy and butyrate-treated Shigella-infected rabbits. Ciprofloxacin also down-regulated butyrate-induced transcription of the human beta-defensin-3 in HT-29 cells. Microarray analysis of HT-29 cells revealed upregulation by butyrate with subsequent down-regulation by ciprofloxacin of additional genes encoding immune factors. Dephosphorylation of histone H3, an epigenetic event provided a possible mechanism of the suppressive effect of ciprofloxacin. Furthermore, LL-37 peptide inhibited Clostridium difficile growth in vitro. In conclusion, ciprofloxacin and clindamycin exert immunomodulatory function by down-regulating AMPs and other immune components in colonic epithelial cells. Suppression of AMPs may contribute to the overgrowth of C. difficile, causing antibiotic-associated diarrhea. Full article
(This article belongs to the Special Issue Antimicrobial Peptides) Print Edition available
Open AccessArticle A Novel Organo-Selenium Bandage that Inhibits Biofilm Development in a Wound by Gram-Positive and Gram-Negative Wound Pathogens
Antibiotics 2014, 3(3), 435-449; doi:10.3390/antibiotics3030435
Received: 30 April 2014 / Revised: 7 August 2014 / Accepted: 19 August 2014 / Published: 25 August 2014
Cited by 1 | PDF Full-text (1807 KB) | HTML Full-text | XML Full-text
Abstract
Biofilm formation in wounds is a serious problem which inhibits proper wound healing. One possible contributor to biofilm formation in a wound is the bacteria growing within the overlying bandage. To test this mechanism, we used bandages that contained a coating of organo-selenium
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Biofilm formation in wounds is a serious problem which inhibits proper wound healing. One possible contributor to biofilm formation in a wound is the bacteria growing within the overlying bandage. To test this mechanism, we used bandages that contained a coating of organo-selenium that was covalently attached to the bandage. We tested the ability of this coating to kill bacteria on the bandage and in the underlying tissue. The bandage material was tested with both lab strains and clinical isolates of Staphylococcus aureus, Pseudomonas aeruginosa and Staphylococcus epidermidis. It was found that the organo-selenium coated bandage showed inhibition, of biofilm formation on the bandage in vitro (7–8 logs), with all the different bacteria tested, at selenium concentrations in the coating of less than 1.0%. These coatings were found to remain stable for over one month in aqueous solution, 15 min in boiling water, and over 6 years at room temperature. The bandages were also tested on a mouse wound model where the bacteria were injected between the bandage and the wound. Not only did the selenium bandage inhibit biofilm formation in the bandage, but it also inhibited biofilm formation in the wound tissue. Since selenium does not leave the bandage, this would appear to support the idea that a major player in wound biofilm formation is bacteria which grows in the overlying bandage. Full article
(This article belongs to the Special Issue Biofilm Infection)
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Open AccessArticle A Point Prevalence Survey of Antibiotic Use in 18 Hospitals in Egypt
Antibiotics 2014, 3(3), 450-460; doi:10.3390/antibiotics3030450
Received: 27 June 2014 / Revised: 22 July 2014 / Accepted: 1 September 2014 / Published: 10 September 2014
Cited by 2 | PDF Full-text (919 KB) | HTML Full-text | XML Full-text
Abstract
Inappropriate antibiotic use leads to increased risk of antibiotic resistance and other adverse outcomes. The objectives of the study were to determine the prevalence and characteristics of antibiotic use in Egyptian hospitals to identify opportunities for quality improvement. A point prevalence survey was
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Inappropriate antibiotic use leads to increased risk of antibiotic resistance and other adverse outcomes. The objectives of the study were to determine the prevalence and characteristics of antibiotic use in Egyptian hospitals to identify opportunities for quality improvement. A point prevalence survey was conducted in 18 hospitals in March 2011. A total of 3408 patients were included and 59% received at least one antibiotic, with the most significant use among persons <12 years and intensive care unit patients (p < 0.05). Third generation cephalosporin were the most commonly prescribed antibiotics (28.7% of prescriptions). Reasons for antibiotic use included treatment of community—(27%) and healthcare-associated infections (11%) and surgical (39%) and medical (23%) prophylaxis. Among surgical prophylaxis recipients, only 28% of evaluable cases received the first dose within two hours before incision and only 25% of cases received surgical prophylaxis for <24 h. The prevalence of antibiotic use in Egyptian hospitals was high with obvious targets for antimicrobial stewardship activities including provision of antibiotic prescription guidelines and optimization of surgical and medical prophylaxis practices. Full article

Review

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Open AccessReview Evolution of Metallo-β-lactamases: Trends Revealed by Natural Diversity and in vitro Evolution
Antibiotics 2014, 3(3), 285-316; doi:10.3390/antibiotics3030285
Received: 11 April 2014 / Revised: 15 June 2014 / Accepted: 18 June 2014 / Published: 1 July 2014
Cited by 9 | PDF Full-text (2966 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The production of β-lactamase enzymes is one of the most distributed resistance mechanisms towards β-lactam antibiotics. Metallo-β-lactamases constitute a worrisome group of these kinds of enzymes, since they present a broad spectrum profile, being able to hydrolyze not only penicillins, but also the
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The production of β-lactamase enzymes is one of the most distributed resistance mechanisms towards β-lactam antibiotics. Metallo-β-lactamases constitute a worrisome group of these kinds of enzymes, since they present a broad spectrum profile, being able to hydrolyze not only penicillins, but also the latest generation of cephalosporins and carbapenems, which constitute at present the last resource antibiotics. The VIM, IMP, and NDM enzymes comprise the main groups of clinically relevant metallo-β-lactamases. Here we present an update of the features of the natural variants that have emerged and of the ones that have been engineered in the laboratory, in an effort to find sequence and structural determinants of substrate preferences. This knowledge is of upmost importance in novel drug design efforts. We also discuss the advances in knowledge achieved by means of in vitro directed evolution experiments, and the potential of this approach to predict natural evolution of metallo-β-lactamases.The production of β-lactamase enzymes is one of the most distributed resistance mechanisms towards β-lactam antibiotics. Metallo-β-lactamases constitute a worrisome group of these kinds of enzymes, since they present a broad spectrum profile, being able to hydrolyze not only penicillins, but also the latest generation of cephalosporins and carbapenems, which constitute at present the last resource antibiotics. The VIM, IMP, and NDM enzymes comprise the main groups of clinically relevant metallo-β-lactamases. Here we present an update of the features of the natural variants that have emerged and of the ones that have been engineered in the laboratory, in an effort to find sequence and structural determinants of substrate preferences. This knowledge is of upmost importance in novel drug design efforts. We also discuss the advances in knowledge achieved by means of in vitro directed evolution experiments, and the potential of this approach to predict natural evolution of metallo-β-lactamases. Full article
(This article belongs to the Special Issue Mechanisms of Antibiotic Resistance)
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Open AccessReview Drug Resistance Mechanisms in Mycobacterium tuberculosis
Antibiotics 2014, 3(3), 317-340; doi:10.3390/antibiotics3030317
Received: 8 April 2014 / Revised: 20 June 2014 / Accepted: 23 June 2014 / Published: 2 July 2014
Cited by 5 | PDF Full-text (558 KB) | HTML Full-text | XML Full-text
Abstract
Tuberculosis (TB) is a serious public health problem worldwide. Its situation is worsened by the presence of multidrug resistant (MDR) strains of Mycobacterium tuberculosis, the causative agent of the disease. In recent years, even more serious forms of drug resistance have been
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Tuberculosis (TB) is a serious public health problem worldwide. Its situation is worsened by the presence of multidrug resistant (MDR) strains of Mycobacterium tuberculosis, the causative agent of the disease. In recent years, even more serious forms of drug resistance have been reported. A better knowledge of the mechanisms of drug resistance of M. tuberculosis and the relevant molecular mechanisms involved will improve the available techniques for rapid drug resistance detection and will help to explore new targets for drug activity and development. This review article discusses the mechanisms of action of anti-tuberculosis drugs and the molecular basis of drug resistance in M. tuberculosis. Full article
(This article belongs to the Special Issue Mechanisms of Antibiotic Resistance)
Open AccessReview Uncomplicated Urinary Tract Infections and Antibiotic Resistance—Epidemiological and Mechanistic Aspects
Antibiotics 2014, 3(3), 341-352; doi:10.3390/antibiotics3030341
Received: 23 April 2014 / Revised: 11 July 2014 / Accepted: 14 July 2014 / Published: 22 July 2014
Cited by 2 | PDF Full-text (594 KB) | HTML Full-text | XML Full-text
Abstract
Uncomplicated urinary tract infections are typically monobacterial and are predominantly caused by Escherichia coli. Although several effective treatment options are available, the rates of antibiotic resistance in urinary isolates of E. coli have increased during the last decade. Knowledge of the actual
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Uncomplicated urinary tract infections are typically monobacterial and are predominantly caused by Escherichia coli. Although several effective treatment options are available, the rates of antibiotic resistance in urinary isolates of E. coli have increased during the last decade. Knowledge of the actual local rates of antibiotic resistant pathogens as well as the underlying mechanisms are important factors in addition to the geographical location and the health state of the patient for choosing the most effective antibiotic treatment. Recommended treatment options include trimethoprim alone or in combination with sulfamethoxazol, fluoroquinolones, β-lactams, fosfomycin-trometamol, and nitrofurantoin. Three basic mechanisms of resistance to all antibiotics are known, i.e., target alteration, reduced drug concentration and inactivation of the drug. These mechanisms—alone or in combination—contribute to resistance against the different antibiotic classes. With increasing prevalence, combinations of resistance mechanisms leading to multiple drug resistant (mdr) pathogens are being detected and have been associated with reduced fitness under in vitro situations. However, mdr clones among clinical isolates such as E. coli sequence type 131 (ST131) have successfully adapted in fitness and growth rate and are rapidly spreading as a worldwide predominating clone of extraintestinal pathogenic E. coli. Full article
(This article belongs to the Special Issue Antibiotics and Urinary Tract Infections) Print Edition available
Open AccessReview Foreign Body Infection Models to Study Host-Pathogen Response and Antimicrobial Tolerance of Bacterial Biofilm
Antibiotics 2014, 3(3), 378-397; doi:10.3390/antibiotics3030378
Received: 2 April 2014 / Revised: 1 July 2014 / Accepted: 6 August 2014 / Published: 21 August 2014
Cited by 2 | PDF Full-text (1139 KB) | HTML Full-text | XML Full-text
Abstract
The number of implanted medical devices is steadily increasing and has become an effective intervention improving life quality, but still carries the risk of infection. These infections are mainly caused by biofilm-forming staphylococci that are difficult to treat due to the decreased susceptibility
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The number of implanted medical devices is steadily increasing and has become an effective intervention improving life quality, but still carries the risk of infection. These infections are mainly caused by biofilm-forming staphylococci that are difficult to treat due to the decreased susceptibility to both antibiotics and host defense mechanisms. To understand the particular pathogenesis and treatment tolerance of implant-associated infection (IAI) animal models that closely resemble human disease are needed. Applications of the tissue cage and catheter abscess foreign body infection models in the mouse will be discussed herein. Both models allow the investigation of biofilm and virulence of various bacterial species and a comprehensive insight into the host response at the same time. They have also been proven to serve as very suitable tools to study the anti-adhesive and anti-infective efficacy of different biomaterial coatings. The tissue cage model can additionally be used to determine pharmacokinetics, efficacy and cytotoxicity of antimicrobial compounds as the tissue cage fluid can be aspirated repeatedly without the need to sacrifice the animal. Moreover, with the advance in innovative imaging systems in rodents, these models may offer new diagnostic measures of infection. In summary, animal foreign body infection models are important tools in the development of new antimicrobials against IAI and can help to elucidate the complex interactions between bacteria, the host immune system, and prosthetic materials. Full article
(This article belongs to the Special Issue Biofilm Infection)
Open AccessReview Acquired Class D β-Lactamases
Antibiotics 2014, 3(3), 398-434; doi:10.3390/antibiotics3030398
Received: 3 June 2014 / Revised: 31 July 2014 / Accepted: 8 August 2014 / Published: 21 August 2014
Cited by 2 | PDF Full-text (1233 KB) | HTML Full-text | XML Full-text
Abstract
The Class D β-lactamases have emerged as a prominent resistance mechanism against β-lactam antibiotics that previously had efficacy against infections caused by pathogenic bacteria, especially by Acinetobacter baumannii and the Enterobacteriaceae. The phenotypic and structural characteristics of these enzymes correlate to activities
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The Class D β-lactamases have emerged as a prominent resistance mechanism against β-lactam antibiotics that previously had efficacy against infections caused by pathogenic bacteria, especially by Acinetobacter baumannii and the Enterobacteriaceae. The phenotypic and structural characteristics of these enzymes correlate to activities that are classified either as a narrow spectrum, an extended spectrum, or a carbapenemase spectrum. We focus on Class D β-lactamases that are carried on plasmids and, thus, present particular clinical concern. Following a historical perspective, the susceptibility and kinetics patterns of the important plasmid-encoded Class D β-lactamases and the mechanisms for mobilization of the chromosomal Class D β-lactamases are discussed. Full article
(This article belongs to the Special Issue Mechanisms of Antibiotic Resistance)

Other

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Open AccessConcept Paper Bacteriophages and Biofilms
Antibiotics 2014, 3(3), 270-284; doi:10.3390/antibiotics3030270
Received: 25 April 2014 / Revised: 6 June 2014 / Accepted: 10 June 2014 / Published: 25 June 2014
Cited by 12 | PDF Full-text (851 KB) | HTML Full-text | XML Full-text
Abstract
Biofilms are an extremely common adaptation, allowing bacteria to colonize hostile environments. They present unique problems for antibiotics and biocides, both due to the nature of the extracellular matrix and to the presence within the biofilm of metabolically inactive persister cells. Such chemicals
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Biofilms are an extremely common adaptation, allowing bacteria to colonize hostile environments. They present unique problems for antibiotics and biocides, both due to the nature of the extracellular matrix and to the presence within the biofilm of metabolically inactive persister cells. Such chemicals can be highly effective against planktonic bacterial cells, while being essentially ineffective against biofilms. By contrast, bacteriophages seem to have a greater ability to target this common form of bacterial growth. The high numbers of bacteria present within biofilms actually facilitate the action of bacteriophages by allowing rapid and efficient infection of the host and consequent amplification of the bacteriophage. Bacteriophages also have a number of properties that make biofilms susceptible to their action. They are known to produce (or to be able to induce) enzymes that degrade the extracellular matrix. They are also able to infect persister cells, remaining dormant within them, but re-activating when they become metabolically active. Some cultured biofilms also seem better able to support the replication of bacteriophages than comparable planktonic systems. It is perhaps unsurprising that bacteriophages, as the natural predators of bacteria, have the ability to target this common form of bacterial life. Full article
(This article belongs to the Special Issue Biofilm Infection)
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