Ciprofloxacin resistance among nosocomial Pseudomonas aeruginosa and Staphylococcus aureus in the United States

The Expression of Efflux Pump Genes in Methicillin-Resistant Staphylococcus aureus (MRSA) Strains Isolated from Blood Cultures in Iran

Background: Efflux pump is a significant resistance mechanism in Staphylococcus aureus. A total of 100 patients with bacteremia from Shahid Beheshti University Hospitals of Tehran in Iran were tested for the expression of efflux pump genes, contributing to S. aureus antimicrobial resistance. Objectives: This study was conducted to identify antibiotic resistance pattern, and to evaluate the inhibitory effect of efflux pump, MIC of ciprofloxacin, and expression levels of norA, norB, and norC efflux pump genes in the presence of an efflux pump inhibitor against MDR S. aureus. Methods: A total of 100 MRSA isolates were investigated in different hospitals of Shahid Beheshti University of Medical Sciences from April 2017 - 2018. Owing to new consensus guidelines from the Clinical and Laboratory Standards Institute (CLSI), both the Kirby-Bauer disk diffusion test and micro-dilution method were used to evaluate antimicrobial susceptibility. Efflux pump activity using carbonyl cyanide 3-chlorophenylhydrazone (CCCP) was identified as a chemical efflux pump inhibitor. E-test was used to determine vancomycin-resistant antibiotic. Broth micro-dilution method for S. aureus isolates resistant to ciprofloxacin has been developed for minimum inhibitory concentration (MIC) of ciprofloxacin and CCCP and their composition. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to investigate the expression level of norA, norB, and norC efflux pump genes. Results: A total of 38 of 45 MRSA isolates (84.4%) showed resistance to ciprofloxacin. Moreover, 100% of isolates had the norA and norB genes. Further, 95% of S. aureus isolates had the norC gene. According to this study, ciprofloxacin MIC has decreased by CCCP compared to ciprofloxacin. There was an increase in the expression level of norA, norB, and norC efflux pump genes in methicillin-resistant and ciprofloxacin-resistant S. aureus strains based on RT- PCR. In this study, four different spA types were obtained as the most prevalent type of spA by t037and t790 (23.3%) and t030 (14.1%) and t044 (12.2%). Conclusions: This study indicates that the prevalence of ciprofloxacin-resistant S. aureus strains has a rising trend among MRSA clinical isolates. The ability of S. aureus isolates to be converted into drug-resistant strains using efflux pump mechanism has become a widespread concern.

Association of norB overexpression and fluoroquinolone resistance in clinical isolates of Staphylococcus aureus from Korea

OBJECTIVES

Although the prevalence of fluoroquinolone resistance among methicillin-resistant Staphylococcus aureus (MRSA) is known to be higher than in methicillin-susceptible S. aureus (MSSA), the reasons have never been identified.

METHODS

We randomly selected 115 isolates of S. aureus collected from 10 different hospitals in Korea between June 2009 and May 2011. To investigate the difference in fluoroquinolone resistance mechanisms between MRSA and MSSA, we evaluated gyrA and parC mutations and the relative expression of the multidrug efflux pump genes norA, norB and norC.

RESULTS

All 62 ciprofloxacin-resistant S. aureus had either gyrA or parC mutations. The S84L mutation of gyrA (59/62, 95.2%) and the S80F mutation of parC (61/62, 98.4%) were the most common. Fifty-eight (93.6%) strains had both the S84L mutation of gyrA and the S80F mutation of parC. Among the 115 isolates, norB overexpression was the most common, occurring in 49 (42.6%) strains. There were only two (1.7%) strains with norA overexpression and none with norC overexpression. Strains overexpressing norB were more common among ciprofloxacin-resistant S. aureus (33/62, 53.2%) than ciprofloxacin-susceptible S. aureus (16/53, 30.2%) (P = 0.013). When we analysed 62 ciprofloxacin-resistant S. aureus strains, those overexpressing norB were more common in ciprofloxacin-resistant MRSA (28/46, 60.9%) than in ciprofloxacin-resistant MSSA (5/16, 31.3%) (P = 0.041).

CONCLUSIONS

Increased expression of norB can be a factor that contributes to ciprofloxacin resistance in MRSA strains.

Surveillance of intrahospital infections at the clinic for gynaecology and obstetrics

Intrahospital infections (IHI) and antibiotics resistance are the problems which exist in virtually all hospitals in the world. The main aim of the present research is establishing of epidemiological surveillance over occurrence of IHI at the Clinic for Gynaecology and Obstetrics at the University Clinical Center Tuzla and thus identifies: types of bacteria which cause IHI, types of infection according to anatomical localization and research resistance organisms causing of IHI on antimicrobial drugs. A study was implemented on all patients admitted to Clinic for Gynaecology and Obstetrics during the period of one year and who subsequently developed infection. Determination of intrahospital infections was done according to criteria defined by the Centres for Disease Control and Prevention from the United States. The results of our work have shown that both urinary tract infections and surgical site infections are the most frequent. As IHI causers the most found are gram-negative organisms (73,7%), such as Escherichia coli (29,8%), right after that Klebsiella pneumoniae (24,6%), Pseudomonas aeruginosa (14%) and Proteus mirabilis (5,3%) (p<0,05). Gram-positive organisms as causers of IHI are registered in 26,3% cases. Out of that Streptococcus species are isolated in 10,5% cases, Staphylococcus aureus (8,8%) and coagulasa negative staphylococci (7%) (p>0,05). High percent resistance of bacteria was evident to beta-lactams, aminoglycosids and cephalosporin's of third generation. Gram-positive organisms were 100% sensitive to vancomycin, while gram-negative organisms manifested the high percent of sensibility to imipenem and cefepime.

A review of antimicrobial peptides and their therapeutic potential as anti-infective drugs

PURPOSE

Antimicrobial peptides (AMPs) are an essential part of innate immunity that evolved in most living organisms over 2.6 billion years to combat microbial challenge. These small cationic peptides are multifunctional as effectors of innate immunity on skin and mucosal surfaces and have demonstrated direct antimicrobial activity against various bacteria, viruses, fungi, and parasites. This review summarizes their progress to date as commercial antimicrobial drugs for topical and systemic indications.

METHODS

Literature review.

RESULTS

Despite numerous clinical trials, no modified AMP has obtained Food & Drug Administration approval yet for any topical or systemic medical indications.

CONCLUSIONS

While AMPs are recognized as essential components of natural host innate immunity against microbial challenge, their usefulness as a new class of antimicrobial drugs still remains to be proven.

Comparative activity and spectrum of broad-spectrum β-lactams (cefepime, ceftazidime, ceftriaxone, piperacillin/tazobactam) tested against 12,295 staphylococci and streptococci: report from the SENTRY antimicrobial surveillance program (North America: 2001-2002)

A contemporary collection of 12,295 North American isolates (2001-2002) consisting of Staphylococcus aureus (50%), coagulase-negative staphylococci (12%), Streptococcus pneumoniae (24%), beta-hemolytic streptococci (12%), and viridans-group streptococci (2%) were tested against broad-spectrum beta-lactams (cefepime, ceftazidime, ceftriaxone, imipenem, piperacillin/tazobactam) and comparator agents using a reference broth microdilution method to determine their continued effectiveness for empiric antimicrobial therapy. All isolates were very susceptible to vancomycin, linezolid and quinupristin/dalfopristin (>98%). Oxacillin-susceptible staphylococci were also highly susceptible to the tested beta-lactams (>98%) with the exception of ceftazidime (93%). beta-hemolytic streptococci were exquisitely susceptible (>99%) to penicillin and all other agents except for clindamycin (94%) and erythromycin (81%). Viridans group streptococci were routinely less susceptible than were other streptococci. S. pneumoniae remained susceptible to most agents (>91%) with the exceptions of erythromycin (74%) and penicillin (69%). Among beta-lactams tested against S. pneumoniae, ceftriaxone and cefepime continued to be very active against penicillin-susceptible (>99%) and intermediate (>98%) strains, but less active (80% and 82%, respectively) against penicillin-resistant isolates. These findings confirm that the newer cephalosporins (cefepime and ceftriaxone) among broad-spectrum beta-lactam agents have a spectrum of activity that remains comprehensive for the commonly isolated Gram-positive pathogens.

Overview of resistant gram-positive pathogens in the surgical patient

Staphylococci and enterococci are the most common pathogens in surgical-site and bloodstream infections. The emergence of drug resistance among these gram-positive bacteria thus poses a substantial threat to patients with surgical infections. Resistance to methicillin/oxacillin is frequently observed in Staphylococcus aureus isolates and is often accompanied by multidrug resistance. Vancomycin is usually the treatment of choice for infections caused by methicillin-resistant S. aureus (MRSA), so the recent appearance of S. aureus isolated with intermediate sensitivity to vancomycin is cause for concern. Vancomycin resistance has already appeared in most species of enterococci. Infections caused by vancomycin-resistant enterococci (VRE) are associated with increased mortality compared to infections caused by vancomycin-sensitive isolates. Measures for preventing vancomycin resistance include reducing the use of vancomycin and other agents that appear to be associated with VRE, including third-generation cephalosporins and anti-anaerobic drugs. Third-generation cephalosporins have also been implicated in the increased prevalence of MRSA infections. Prudent use of existing antibiotics is an essential strategy for combating the rising tide of drug-resistant gram-positive pathogens.

Emerging mechanisms of fluoroquinolone resistance

Broad use of fluoroquinolones has been followed by emergence of resistance, which has been due mainly to chromosomal mutations in genes encoding the subunits of the drugs' target enzymes, DNA gyrase and topoisomerase IV, and in genes that affect the expression of diffusion channels in the outer membrane and multidrug-resistance efflux systems. Resistance emerged first in species in which single mutations were sufficient to cause clinically important levels of resistance (e.g., Staphylococcus aureus and Pseudomonas aeruginosa). Subsequently, however, resistance has emerged in bacteria such as Campylobacter jejuni, Escherichia coli, and Neisseria gonorrhoeae, in which multiple mutations are required to generate clinically important resistance. In these circumstances, the additional epidemiologic factors of drug use in animals and human-to-human spread appear to have contributed. Resistance in Streptococcus pneumoniae, which is currently low, will require close monitoring as fluoroquinolones are used more extensively for treating respiratory tract infections.

Origins and consequences of antimicrobial-resistant nontyphoidal Salmonella: implications for the use of fluoroquinolones in food animals

Human Salmonella infections are common; most infections are self-limiting, however severe disease may occur. Antimicrobial agents, while not essential for the treatment of Salmonella gastroenteritis, are essential for the treatment of thousands of patients each year with invasive infections. Fluoroquinolones and third-generation cephalosporins are the drugs-of-choice for invasive Salmonella infections in humans; alternative antimicrobial choices are limited by increasing antimicrobial resistance, limited efficacy, and less desirable pharmacodynamic properties. Antimicrobial-resistant Salmonella results from the use of antimicrobial agents in food animals, and these antimicrobial resistant Salmonella are subsequently transmitted to humans, usually through the food supply. The antimicrobial resistance patterns of isolates collected from persons with Salmonella infections show more resistance to antimicrobial agents used in agriculture than to antimicrobial agents used for the treatment of Salmonella infections in humans. Because of the adverse health consequences in humans and animals associated with the increasing prevalence of antimicrobial-resistant Salmonella, there is an urgent need to emphasize non-antimicrobial infection control strategies, such as improved sanitation and hygiene, to develop guidelines for the prudent usage of antimicrobial agents, and establishment of adequate public health safeguards to minimize the development and dissemination of antimicrobial resistance and dissemination of Salmonella resistant to these agents.

Toward multinational antimicrobial resistance surveillance systems in Europe

While there is a growing concern about increasing antimicrobial resistance and international spread of resistant microorganisms, we are still lacking timely multinational, good-quality susceptibility data to guide our decisions on controlling such resistance. This review describes and compares current sources of multicentric antimicrobial susceptibility data, identifies problems responsible for the postponing of the implementation of epidemiological antimicrobial resistance surveillance systems and finally presents requirements for such systems.

Risk factor assessment for the acquisition of fluoroquinolone-resistant isolates of Pseudomonas aeruginosa in a community-based hospital

A case-control study was performed in a community-based nonteaching hospital to assess patient risk factors for the acquisition of fluoroquinolone-resistant isolates of Pseudomonas aeruginosa. Fifty-five patients who were hospitalized between July 1, 1993 and December 31, 1993 and who had P. aeruginosa recovered from a clinical specimen were included in the analysis. Two patient populations were designated based on the fluoroquinolone susceptibility of their P. aeruginosa isolates. Statistical evaluation using univariate analysis of demographic and clinical data from the 42 patients with quinolone-susceptible P. aeruginosa and the 13 patients with quinolone-resistant P. aeruginosa demonstrated that prior receipt of a fluoroquinolone was the only significant risk factor for the subsequent emergence of fluoroquinolone resistance among P. aeruginosa isolated from patients hospitalized in this small community-based institution (p = 0.0196). Multivariate analysis supported the finding that prior receipt of a fluoroquinolone was the major risk factor for the isolation of fluoroquinolone-resistant P. aeruginosa (p = 0.0004); isolation of this Gram-negative bacillus from sputum (p = 0.0306) and a history of recent surgery (p = 0.0058) were also significantly associated as risk factors for resistance.

Comparative activity of clinafloxacin and nine other compounds tested against 2000 contemporary clinical isolates from patients in United States hospitals

The in vitro activity of clinafloxacin (formerly CI-960, AM-1091, PD-127391) was compared with other fluoroquinolones, cephalosporins, gentamicin, vancomycin, imipenem, piperacillin/tazobactam, clindamycin, and metronidazole against 2000 recent clinical strains from a large number of hospitals in the United States. Overall, clinafloxacin was the most active compound tested. Against Pseudomonas aeruginosa, clinafloxacin and ciprofloxacin demonstrated comparable activity (88% and 80% susceptible, respectively), and were four- to 16-fold more potent than levofloxacin (MIC90, 16 micrograms/ml) or trovafloxacin (MIC90, 32 micrograms/ml). Among anaerobic bacteria, clinafloxacin (MIC50s, 0.25-0.5 microgram/ml) and trovafloxacin (MIC50s, 0.5-2.0 micrograms/ml) were the most active quinolones, whereas metronidazole, imipenem and piperacillin/tazobactam were the most potent comparators. Clinafloxacin demonstrated sustained activity when compared to several available peer drugs against contemporary clinical isolates. The clinafloxacin spectrum against the 15 important pathogens monitored ranged from nil or 4.0% (vancomycin-resistant enterococci) to 100.0% (four different species) susceptible with an average percent susceptibility of 94.0%. This degree of potency and spectrum for clinafloxacin provides a wide potential for use against many species with established resistance to other anti-microbial classes.

Antimicrobial resistance in Staphylococcus aureus

Recognized since 1883 as a common cause of infection, Staphylococcus aureus' preantimicrobial-era bacteremia mortality rate was 82%. The mortality of that era threatens to return as evidence of growing vancomycin resistance undermines the utility of vancomycin therapy. Successful treatment of S. aureus infections requires knowledge of its antimicrobial resistance capacity.

Antibiotic resistance problems in the critical care unit

The increased resistance of bacteria to antimicrobial agents poses major therapeutic problems for the treatment of patients hospitalized in critical care units. This article discusses the mechanisms of resistance and the basic rationale for the treatment of infected patients. The authors also discuss methods used to control the dissemination of resistant bacteria from patient to patient, the complex problems of colonization, and the strategies used to delay the emergence of resistance to new antibiotics.

Application of the ATC/DDD methodology to monitor antibiotic drug use

In order to monitor the use of antibiotics, it is essential to have comprehensive data on drug consumption. The findings of drug utilisation studies can serve to describe the pattern of drug use in a particular population, to detect areas of concern, and to evaluate the impact of interventions taken to influence the use of drugs. In the present study, the Anatomical Therapeutical Chemical Classification/Defined Daily Doses (ATC/DDD) system developed by the World Health Organisation was evaluated. The system measures the amount of drug used independent of package size and sales price, which allows comparisons not only within an institution but also within a region, a country, or even internationally. Obviously, there can be no modifications of this system. To illustrate the method, the pattern of quinolone use in the general population, in long-term care facilities, and within a single institution was analysed. These drugs were widely used in long-term care facilities in the Nijmegen region of the Netherlands, accounting for about 30% of the antibiotics used in these settings, whereas in the general population as well as in the University Hospital Nijmegen, these drugs constitute only about 6% of the total antibiotics used. These differences are large enough to warrant closer analysis of patterns of antibiotic usage in different settings to identify the reasons for the use of quinolones and to identify measures that might be taken to rationalise the prescription of these drugs.

Surveillance for the emergence and dissemination of antimicrobial resistance in bacteria

Effective surveillance of antimicrobial-resistant bacteria is important for developing rational empiric therapy guidelines and for guiding public health efforts to control and prevent the spread of infective agents. Surveillance must include a timely and thorough review of the test results generated in clinical microbiology laboratories because this data serves as the core of surveillance activities. Besides ensuring data accuracy and optimizing detection of emerging resistance, the role of clinical microbiology also includes supporting the production of informative surveillance reports, providing laboratory resources for outbreak investigations, and monitoring the performance of commonly used susceptibility testing methods. Once the accuracy of susceptibility results has been validated, the data are used by public health agencies and professional societies to monitor resistance trends on a local, state, national, and international level. This information is also used to develop policies for prudent antimicrobial use locally and nationally.

The impact of antimicrobial use on the emergence of antimicrobial-resistant bacteria in hospitals

Abundant evidence suggests a relationship between antimicrobial resistance and use, including models, consistent associations between resistance and antimicrobial use in hospitals, concomitant variation in resistance as antimicrobial use varies, and a dose-response relationship for many pathogen/antimicrobial combinations. Much of the evidence is from studies performed in single hospitals. Most multicenter studies on resistance have not included data on antimicrobial usage. Despite this substantial body of evidence, some studies have not demonstrated an association between antimicrobial resistance and use, suggesting other contributing factors such as cross transmission, interhospital transfer of resistance, a community contribution to resistance, or a complex relationship between resistance and the use of a variety of antimicrobials. Understanding the problem of antimicrobial resistance in a hospital cannot be achieved without knowledge of the hospital's pattern of antimicrobial use.

Control of antimicrobial resistance in the health care system

Resistance continues to spread in nosocomial pathogens in acute care hospitals and other key settings of managed health care systems. Appropriate control measures for such resistant organisms depend, in part, on the pathways by which resistance has arisen. Unfortunately, these pathways differ greatly from organism to organism and setting to setting. Although the epidemiology of resistant organisms sometimes is similar to that of susceptible organisms of the same kind, in some situations it may be quite different. This article highlights some of the pathways leading to the development of resistance in bacteria and the relevance of these mechanisms to measures for the control of resistant bacteria in hospital and community settings.

Ciprofloxacin. An updated review of its pharmacology, therapeutic efficacy and tolerability

Ciprofloxacin is a broad spectrum fluoroquinolone antibacterial agent. Since its introduction in the 1980s, most Gram-negative bacteria have remained highly susceptible to this agent in vitro; Gram-positive bacteria are generally susceptible or moderately susceptible. Ciprofloxacin attains therapeutic concentrations in most tissues and body fluids. The results of clinical trials with ciprofloxacin have confirmed its clinical efficacy and low potential for adverse effects. Ciprofloxacin is effective in the treatment of a wide variety of infections, particularly those caused by Gram-negative pathogens. These include complicated urinary tract infections, sexually transmitted diseases (gonorrhoea and chancroid), skin and bone infections, gastrointestinal infections caused by multiresistant organisms, lower respiratory tract infections (including those in patients with cystic fibrosis), febrile neutropenia (combined with an agent which possesses good activity against Gram-positive bacteria), intra-abdominal infections (combined with an antianaerobic agent) and malignant external otitis. Ciprofloxacin should not be considered a first-line empirical therapy for respiratory tract infections if penicillin-susceptible Streptococcus pneumoniae is the primary pathogen; however, it is an appropriate treatment option in patients with mixed infections (where S. pneumoniae may or may not be present) or in patients with predisposing factors for Gram-negative infections. Clinically important drug interactions involving ciprofloxacin are well documented and avoidable with conscientious prescribing. Recommended dosage adjustments in patients with impaired renal function vary between countries; major adjustments are not required until the estimated creatinine clearance is < 30 ml/min/1.73m2 (or when the serum creatinine level is > or = 2 mg/dl). Ciprofloxacin is one of the few broad spectrum antibacterials available in both intravenous and oral formulations. In this respect, it offers the potential for cost savings with sequential intravenous and oral therapy in appropriately selected patients and may allow early discharge from hospital in some instances. In conclusion, ciprofloxacin has retained its excellent activity against most Gram-negative bacteria, and fulfilled its potential as an important antibacterial drug in the treatment of a wide range of infections. Rational prescribing will help to ensure the continued clinical usefulness of this valuable antimicrobial drug.