Changes In Resistance Profiles Research Articles

Detection of Macrolide and/or Fluoroquinolone Resistance Genes in Mycoplasma genitalium Strains Isolated from Men in the Northwest Region of Croatia in 2018-2023.

Mycoplasma genitalium (M. genitalium) poses a significant public health challenge due to its association with non-gonococcal urethritis (particularly in men) and antimicrobial resistance. However, despite the prevalence of M. genitalium infections and the rise in resistance rates, routine testing and surveillance remain limited. This is the first study from Croatia that aimed to assess the prevalence and trends of resistance in M. genitalium strains isolated from male individuals by detecting macrolide and fluoroquinolone resistance genes. The study also aimed to explore the factors associated with resistance and changes in resistance patterns over time. Urine samples collected from male individuals in the Zagreb County and northwest region of Croatia between 2018 and 2023 were tested for M. genitalium with the use of molecular methods. Positive samples were subjected to DNA extraction and multiplex tandem polymerase chain reaction (MT-PCR) targeting genetic mutations associated with macrolide (23S rRNA gene) and fluoroquinolone (parC gene) resistance. Of the 8073 urine samples tested from 6480 male individuals (and following the exclusion of repeated specimens), we found that the prevalence of M. genitalium infection was 2.2%. Macrolide resistance was observed in 60.4% of strains, while fluoroquinolone resistance was found in 19.2%. Co-resistance to both antibiotics was present in 18.2% of cases. A statistically significant increase in fluoroquinolone resistance was noted over the study period (p = 0.010), but this was not evident for azithromycin resistance (p = 0.165). There were no statistically significant differences in resistance patterns between age groups, whereas re-testing of patients revealed dynamic changes in resistance profiles over time. The high burden of macrolide resistance and increasing fluoroquinolone resistance underscore the urgent need for comprehensive resistance testing and surveillance programs. The implementation of resistance-guided treatment strategies, along with enhanced access to molecular diagnostics, is pivotal for effectively managing M. genitalium infections.

Antimicrobial Resistance Profile of Staphylococcus hyicus Strains Isolated from Brazilian Swine Herds.

Staphylococcus hyicus is the causative agent of porcine exudative epidermitis. This disorder affects animals in all producing countries and presents a widespread occurrence in Brazil. This study evaluated strains from a historical collection in order to detect the presence of exfoliative-toxin-encoding genes (SHETB, ExhA, ExhB, ExhC, ExhD), characterize the strains using PFGE, and determine their respective antimicrobial resistance profiles. The results obtained from the evaluation of 77 strains from 1982 to 1987 and 103 strains from 2012 reveal a significant change in resistance profiles between the two periods, especially regarding the antimicrobial classes of fluoroquinolones, amphenicols, lincosamides, and pleuromutilins. The levels of multidrug resistance observed in 2012 were significantly higher than those detected in the 1980s. It was not possible to correlate the resistance profiles and presence of genes encoding toxins with the groups obtained via PFGE. Only 10.5% of the strains were negative for exfoliative toxins, and different combinations of toxins genes were identified. The changes observed in the resistance pattern of this bacterial species over the 30-year period analyzed indicate that S. hyicus could be a useful indicator in resistance monitoring programs in swine production. In a country with animal protein production such as Brazil, the results of this study reinforce the need to establish consistent monitoring programs of antimicrobial resistance in animals, as already implemented in various countries of the world.

Electro-mechanical Behavior of Graphene–Polystyrene Composites Under Dynamic Loading

An experimental investigation was conducted to understand the electro-mechanical response of graphene reinforced polystyrene (PS) composites under static and dynamic loading. Graphene/PS composites were fabricated using a solution mixing approach followed by hot-pressing. Absolute resistance values were measured with a high-resolution four-point probe method for both quasi-static and dynamic loading. A modified split Hopkinson (Kolsky) pressure bar apparatus, capable of simultaneous mechanical and electrical characterization, was developed and implemented to investigate the dynamic electro-mechanical response of the composites. In addition to measuring the change in electrical resistance as well as the dynamic constitutive behavior, real-time surface damage and global deformation was captured using high-speed photography. The real-time damage was correlated to both stress–strain and percent change in resistance profiles. The experimental findings indicate that the bulk resistance of the composite increased significantly due to the brittle nature of the PS matrix and the presence of relative agglomerations of graphene platelets which resulted in micro-crack formations. Scanning electron microscopy imaging gives further insight into the various damage mechanisms that occur within the composites subjected to a static or dynamic load. The results show that the change in transport properties can provide further insight into the micro-structural evolution of composite materials during loading.

Treatment for bovineEscherichia colimastitis – an evidence‐based approach

Bovine mastitis caused by Escherichia coli can range from being a subclinical infection of the mammary gland to a severe systemic disease. Cow-dependent factors such as lactation stage and age affect the severity of coliform mastitis. Evidence for the efficacy of antimicrobial treatment for E.coli mastitis is very limited. Antimicrobial resistance is generally not a limiting factor for treatment, but it should be monitored to detect changes in resistance profiles. The only antimicrobials for which there is some scientific evidence of beneficial effects in the treatment for E.coli mastitis are fluoroquinolones and cephalosporins. Both are critically important drugs, the use of which in animals destined for food should be limited to specific indications and should be based on bacteriological diagnosis. The suggested routine protocol in dairy herds could target the primary antimicrobial treatment for mastitis, specifically infections caused by gram-positive bacteria. In E.coli mastitis with mild to moderate clinical signs, a non-antimicrobial approach (anti-inflammatory treatment, frequent milking and fluid therapy) should be the first option. In cases of severe E.coli mastitis, parenteral administration of fluoroquinolones, or third- or fourth-generation cephalosporins, is recommended due to the risk of unlimited growth of bacteria in the mammary gland and ensuing bacteremia. Evidence for the efficacy of intramammary-administered antimicrobial treatment for E.coli mastitis is so limited that it cannot be recommended. Nonsteroidal anti-inflammatory drugs have documented the efficacy in the treatment for E.coli mastitis and are recommended for supportive treatment for clinical mastitis.

Decline in rates of acquired multidrug-resistant tuberculosis after implementation of the directly observed therapy, short course (DOTS) and DOTS-Plus programmes in Taiwan

To investigate the impact of the directly observed therapy, short course (DOTS) and DOTS-Plus strategies on changes in resistance profiles among Mycobacterium tuberculosis (MTB). We performed a retrospective analysis of resistance profiles among isolates of MTB obtained from 2160 consecutive patients with culture-confirmed pulmonary tuberculosis (TB) between 2005 and 2011 at a referral centre in southern Taiwan. Of the 2160 patients, 70 (3.2%) had primary multidrug-resistant (MDR)-TB, 178 (8.2%) had acquired MDR-TB, 10 (0.5%) had primary extensively drug-resistant (XDR)-TB, 23 (1.1%) had acquired XDR-TB and 5 (0.2%) had totally drug-resistant (TDR)-TB. Trend analysis revealed that the rates of acquired MDR-TB were significantly lower after implementation of the DOTS and DOTS-Plus programmes (P < 0.01). There was a significant negative correlation between the coverage rates of the DOTS and DOTS-Plus programmes and the rates of acquired MDR-TB (r = -0.84, P = 0.02 and r = -0.92, P = 0.03, respectively). The rates of resistance to rifampicin, isoniazid, ofloxacin, moxifloxacin, levofloxacin and para-aminosalicylic acid also decreased significantly during the study period. However, the rates of primary MDR-TB remained stable (P = 0.11). Multivariate logistic regression analysis showed that age ranging from 45 to 64 years, positive acid-fast stain results at the initiation of treatment and treatment without DOTS were independent risk factors associated with acquired MDR-TB. In addition, previous treatment for TB (100% versus 19% for TDR-TB and non-TDR-TB, P < 0.01) and treatment without DOTS (80% versus 44% for TDR-TB and non-TDR-TB, P = 0.18) were risk factors for TDR-TB. DOTS and DOTS-Plus are both effective at preventing the acquisition of MDR-TB in Taiwan.

Electrical Response of Carbon Nanotube Reinforced Nanocomposites Under Static and Dynamic Loading

An experimental investigation was conducted to study the effect of quasi-static and dynamic compressive loading on the electrical response of multi-wall carbon nanotube (MWCNT) reinforced epoxy nanocomposites. An in-situ polymerization process using both a shear mixer and an ultrasonic processor were employed to fabricate the nanocomposite material. The fabrication process parameters and the optimum weight fraction of MWCNTs for generating a well-dispersed percolation network were first determined. Absolute resistance values were measured with a high-resolution four-point probe method for both quasi-static and dynamic loading. In addition to measuring the percentage change in electrical resistance, real-time damage was captured using high-speed photography. The real-time damage was correlated to both load and percentage change in resistance profiles. The experimental findings indicate that the bulk electrical resistance of the nanocomposites under both quasi-static and dynamic loading conditions initially decreased between 40%–60% during compression and then increased as damage initiated and propagated.

Recovery of Multidrug-Resistant Bacteria From Combat Personnel Evacuated From Iraq and Afghanistan at a Single Military Treatment Facility

U.S. combat casualties from Iraq and Afghanistan continue to develop infections with multidrug-resistant (MDR) bacteria. This study assesses the infection control database and clinical microbiology antibiograms at a single site from 2005 to 2007, a period when all Operation Iraqi Freedom (OIF)/Operation Enduring Freedom (OEF) casualties admitted to the facility underwent initial isolation and screening for MDR pathogens. During this 3-year period, there were 2,242 OIF/OEF admissions: 560 in 2005, 724 in 2006, and 958 in 2007. The most commonly recovered pathogens from OIF/OEF admission screening cultures were methicillin-resistant Staphylococcus aureus (MRSA), Klebsiella pneumoniae and Acinetobacter. The yearly nosocomial infection rate of these three pathogens among OIF/OEF admissions ranged between 2 and 4%. There were remarkable changes in resistance profiles for Acinetobacter, K. pneumoniae, and S. aureus over time. Despite aggressive infection control procedures, there is continued nosocomial transmission within the facility and increasing antimicrobial resistance in some pathogens. Novel techniques are needed to control the impact of MDR bacteria in medical facilities.

Variable Resistance Patterns of Integron-Associated Multidrug-ResistantAcinetobacter baumanniiIsolates in a Surgical Intensive Care Unit

Between 1998 and 2000, we characterized 91 nosocomial isolates of Acinetobacter baumannii by antibiotyping and genotyping. A total of 25 ribotypes were obtained among these 91 isolates. When the isolates from surgical intensive care units (ICUs) and other wards were compared, multiresistant A. baumannii isolates with the same ribotype 25 (R-25) were significantly more prevalent in nosocomial infections among the surgical patients. Further subtyping of the strains by pulsed-field gel electrophoresis confirmed that strains of the same ribotype in surgical ICUs and a few isolates from other wards were identical or clonally related. Different antibiotic resistance profiles were observed among these R-25 isolates. All R-25 isolates contained intI1 integrase, and two clusters of integron cassettes were found. These clusters of cassettes were encoded by an open reading frame (ORF) of -5'CS-aac(3)Ia-aadA1a-unknown or f-3'CS or 5'CS-aacA4-aadA1-catB8-3'CS, indicating the involvement of different resistant genes. Two isolates contained bla (IMP-1), which was acquired from a conjugatively transferable plasmid and did not involve integron-associated resistance. In conclusion, an epidemic of nosocomial infections associated with A. baumannii strains that have different resistance profiles was identified. Resistance profiles can change by a combination of plasmid- and integron-associated acquisition, especially in a unit with high antibiotic selective pressures. Infectious control personnel should be alert to the change in resistance profiles during routine monitoring.