Antimicrobial Susceptibility Testing Research Articles

Species distribution and antimicrobial susceptibility of Burkholderia cepacia complex isolates in clinical infections: Experience from a tertiary care hospital, Southern India

PurposeBurkholderia cepacia complex (Bcc) is a diverse group of environmental bacteria associated with opportunistic infections. The identification of Bcc using conventional methods poses challenges. Bcc infections are difficult to treat due to intrinsic antibiotic resistance. The study aimed to investigate the species distribution and antimicrobial susceptibility of clinical Bcc isolates. MethodsA total of 153 Bcc isolates obtained from clinical samples were analysed. Species identification was carried out using automated methods, including MALDI-TOF MS and VITEK2. Antimicrobial susceptibility testing was performed using the disc diffusion method. ResultsBurkholderia cenocepacia (70.5%) emerged as the most prevalent species, followed by Burkholderia contaminans (9.8%) and Burkholderia cepacia (7.2%). Ventilator-associated pneumonia (38.6%) was the most common infection, followed by sepsis (28.1%). Co-existence of Bcc with other pathogens in many cases suggested potential co-infection scenarios. Antimicrobial susceptibility revealed that ceftazidime, co-trimoxazole and meropenem were the most effective drugs, while levofloxacin proved to be the least effective. Moderate susceptibility was noted to minocycline, with 4.6% of isolates exhibiting multi-drug resistance. ConclusionThis study provides valuable insights into the prevalence, clinical associations, and antibiotic susceptibility of Bcc in India. It highlights the importance of Bcc as a nosocomial pathogen, especially in vulnerable patient populations. The findings contribute to understanding Bcc infections, their distribution, and emphasize the necessity for accurate identification methods in clinical settings.

Evaluation of fortimicin antibiotic combinations against MDR Pseudomonas aeruginosa and resistome analysis of a whole genome sequenced pan-drug resistant isolate

BackgroundMultidrug-resistant (MDR) P. aeruginosa is a rising public health concern, challenging the treatment of such a ubiquitous pathogen with monotherapeutic anti-pseudomonal agents. Worryingly, its genome plasticity contributes to the emergence of P. aeruginosa expressing different resistant phenotypes and is now responsible for notable epidemics within hospital settings. Considering this, we aimed to evaluate the synergistic combination of fortimicin with other traditional anti-pseudomonal agents and to analyze the resistome of pan-drug resistant (PDR) isolate.MethodsStandard methods were used for analyzing the antimicrobial susceptibility tests. The checkerboard technique was used for the in vitro assessment of fortimicin antibiotic combinations against 51 MDR P. aeruginosa and whole genome sequencing was used to determine the resistome of PDR isolate.ResultsOut of 51 MDR P. aeruginosa, the highest synergistic effect was recorded for a combination of fortimicin with β-lactam group as meropenem, ceftazidime, and aztreonam at 71%, 59% and 43%, respectively. Of note, 56.8%, 39.2%, and 37.2% of the tested MDR isolates that had synergistic effects were also resistant to meropenem, ceftazidime, and aztreonam, respectively. The highest additive effects were recorded for combining fortimicin with amikacin (69%) and cefepime (44%) against MDR P. aeruginosa. Resistome analysis of the PDR isolate reflected its association with the antibiotic resistance phenotype. It ensured the presence of a wide variety of antibiotic-resistant genes (β-lactamases, aminoglycosides modifying enzymes, and efflux pump), rendering the isolate resistant to all clinically relevant anti-pseudomonal agents.ConclusionFortimicin in combination with classical anti-pseudomonal agents had shown promising synergistic activity against MDR P. aeruginosa. Resistome profiling of PDR P. aeruginosa enhanced the rapid identification of antibiotic resistance genes that are likely linked to the appearance of this resistant phenotype and may pave the way to tackle antimicrobial resistance issues shortly.

Australian Gonococcal Surveillance Programme, 1 October to 31 December 2023

The Australian National Neisseria Network (NNN) comprises reference laboratories in each state and territory that report data on antimicrobial susceptibility testing to an agreed group of antimicrobial agents for the Australian Gonococcal Surveillance Programme (AGSP). The AGSP data are presented quarterly in tabulated form, as well as in the AGSP annual report. This report presents national gonococcal antimicrobial resistance surveillance data from 1 October to 31 December 2023

Implementation of the EUCAST rapid antimicrobial susceptibility test (RAST) for carbapenemase/ESBL-producing Escherichia coli and Klebsiella pneumoniae isolates, and its effect on mortality.

With the rise in antimicrobial resistance, there is a growing demand for rapid antimicrobial susceptibility testing (RAST). In this study, we applied the EUCAST RAST method to ESBL/carbapenemase-producing Escherichia coli and Klebsiella pneumoniae isolates without using advanced identification systems and analysed the effect of this method on mortality rates Also the clinical impact of this method on patients infected with these bacteria and its effect on mortality rates were investigated. RAST was used for clinical blood cultures containing carbapenemase/ESBL-producing E. coli and K. pneumoniae without advanced identification systems (e.g. MALDI TOF), with preliminary identification by simple diagnostic tests (predicted RAST, or p-RAST), and its categorical agreement was investigated. The impact of the method on mortality was analysed by comparing the clinical data of patients whose blood cultures were subject to p-RAST (p-RAST group, n = 49) and those who were not subject to p-RAST (non-RAST group, n = 145). p-RAST results were analysed based on 539 antibiotic-bacteria combinations. Total error rates at 4, 6 and 8 h of incubation were 2.9%, 3.9% and 3.8%, respectively. In the p-RAST group, patients who did not receive appropriate antibiotics (29/45, 59.1%) were switched to appropriate treatment within 8 h at the latest. In contrast, in the non-RAST group, treatment of patients who received inappropriate antibiotics (79/145, 54.5%) could be changed after at least 24 h. Mortality rates were lower in the p-RAST group than in the non-RAST group (28.6% versus 51.7%, P = 0.005). p-RAST can be used safely in hospital laboratories with high rates of antimicrobial resistance and can reduce mortality rates by shortening the transition time to appropriate treatment.

Molecular Characterization and Antimicrobial Susceptibility Pattern of Microorganisms from Port Harcourt Correctional Center, Rivers State Nigeria

Correctional centers have been reported to be associated with several conditions predisposing inmates to health challenges as a result of exposure to disease causing microbial population. This study therefore targeted the Molecular Characterization and Antimicrobial susceptibility pattern of Microorganisms from Port Harcourt Correctional Center, Rivers State Nigeria. A total of 150 samples (100 from skin (upper arm) and 50 from wall surfaces) were collected using sterile swab sticks and immediately transported to Department of Microbiology Laboratory, Rivers State University for analyses, using standard microbiological techniques. Molecular characterization was done using Polymerase Chain reaction (PCR) and subjected to gene sequencing. The Kirby-Bauer Disc Diffusion method was used for the antimicrobial susceptibility test. Well in agar method was used to assess the susceptibility of the isolates to honey and Aloe Vera extract. The study revealed that 100% of all the bacterial isolates were resistant to Meropenem, Vancomycin, cefuroxime, and Ceftazidine, while 90% of the bacterial isolates were susceptible to Gentamicin, Cepftriaxone, Erythromycin, and Ciproflozaxine. Data showed the MAR index ranged from 0.3 to 0.8. Statistical analysis revealed there were no significant differences in the mean values of data obtained from the animate and inanimate surfaces (p > 0.05). Molecular identification confirmed the isolates to be Kocuria palustris, Serretia liquefaciens, Klebsiella pneumonia, Enterococcus feacalis, Bacillus flexus, and Aspergillus niger. The results revealed that honey was more effective (100%) than Aloe Vera extract which inhibited only one of the Escherichia coli isolates. The study displayed the antimicrobial effect of honey against both Gram positive and Gram negative bacterial isolates. While adequate personal hygiene, proper sanitation, and spaced room should be encouraged, honey can be used in correctional centers to control bacterial skin infections.

Agreement of antimicrobial susceptibility testing of Pasteurella multocida and Mannheimia haemolytica found in pre-weaned dairy calves with bovine respiratory disease

Bovine respiratory disease (BRD) is one of the primary dis­eases affecting pre-weaned dairy calves and involves respi­ratory pathogens, such as Mannheimia haemolytica (Mh) and Pasteurella multocida (Pm). While agreement between methods for detection of bacterial pathogens in dairy calves with BRD is very good, there are limited data regarding how antimicro­bial susceptibility (AS) of isolates collected via these methods agree. The objective was to evaluate agreement among the AS profiles of Mh or Pm obtained by transtracheal wash (TTW), nasal swab (NS), nasopharyngeal swab (DNP), and bronchoal­veolar lavage (BAL) in pre-weaned dairy calves with BRD that were positive in all 4 samples.

Surveillance of Enterobacteriaceae from Diabetic Foot Infections in a Tunisian Hospital: Detection of E. coli-ST131-blaCTX-M-15 and K. pneumoniae-ST1-blaNDM-1 Strains.

The study determined the prevalence, antimicrobial resistant (AMR) determinants, and genetic characteristics of Escherichia coli and Klebsiella pneumoniae isolates from patients with diabetic foot infection (DFI) in a Tunisian hospital. A total of 26 Escherichia spp. and Klebsiella spp. isolates were recovered and identified by MALDI-TOF-MS. Antimicrobial susceptibility testing, the detection of AMR determinants and Shiga-like toxin genes, phylogenetic grouping, and molecular typing were performed. Twelve E. coli, 10 K. pneumoniae, 3 K. oxytoca, and 1 E. hermanii were isolated. A multidrug-resistant phenotype was detected in 65.4% of the isolates. About 30.8% of isolates were extended-spectrum β-lactamase (ESBL) producers and mainly carried blaCTX-M-15 and blaCTX-M-14 genes. One blaNDM-1-producing K. pneumoniae-ST1 strain was identified. Class 1 integrons were detected in 11 isolates and 5 gene cassette arrangements were noted: dfrA1+aadA1 (n = 1), dfrA12+aadA2 (n = 3), and dfrA17+aadA5 (n = 1). Other non-β-lactam resistance genes detected were as follows (number of isolates): aac(3')-II (3), aac(6')-Ib-cr(8), qnrB (2), qnrS (4), cmlA (2), floR (4), sul1 (11), sul2 (11), and sul3 (2). The phylogroup B1 was the most frequent (41.7%) among E. coli, and two ESBL-producing isolates corresponded to the ST131-B2 lineage. The ESBL- and carbapenemase-producing Enterobacteriaceae in DFIs are described for the first time in Tunisia.

Co-occurrence of triple carbapenemase genes, bla VIM-2, bla NDM-1, and bla OXA-48 in Enterobacter hormaechei clinical isolates –first report from Croatia

Two Enterobacter hormaechei isolates harbouring three carbapenemase genes each, were isolated from two patients from different ICUs at University Hospital Centre Zagreb, Croatia, which is to our knowledge, the first report of triple carbapenemase (bla VIM-2, bla NDM-1, and bla OXA-48 ) co-existence in E. hormachei strains and also among Enterobacterales members in Croatia. Antimicrobial susceptibility testing showed susceptibility only to colistin and amikacin. The production of carbapenemases was phenotypically tested by immunochromatographic assay and confirmed by PCR. Detailed analysis by Whole Genome Sequencing (WGS) of short reads by Illumina and long reads by Oxford Nanopore Technologies (ONT) was additionally performed and showed that both isolates belonged to ST200. They were separated by 98 Single Nucleotide Polymorphisms (SNPs) having variations in the number of bla VIM-2 genes on the chromosome, the number of bla NDM-1 genes on the plasmid, non-identical bla NDM-1 plasmids, different plasmid content in general, and only one isolate carried a 94 kb prophage.

Prevalence of multi-drug resistant bacteria in intensive care units at Tripoli University Hospital, Tripoli, Libya

ABSTRACT Among hospitalized patients worldwide, infections caused by multidrug-resistant (MDR) bacteria are a major cause of morbidity and mortality. This study aimed to isolate MDR bacteria from five intensive care units (ICUs) at Tripoli University Hospital (TUH). A prospective cross-sectional study was conducted over a seven-month period (September 2022 to March 2023) across five ICUs at TUH. A total of 197 swabs were collected from Patients’, healthcare workers’ and ICUs equipment. Samples collected from patients were nasal swabs, oral cavity swabs, hand swabs, sputum specimens, skin swabs, umbilical venous catheter swabs, and around cannula. Swabs collected from health care workers were nasal swabs, whereas ICUs equipment’s samples were from endotracheal tubes, oxygen masks, and neonatal incubators. Identification and antimicrobial susceptibility test was confirmed by using MicroScan auto SCAN 4 (Beckman Coulter). The most frequent strains were Gram negative bacilli 113 (57.4%) with the predominance of Acinetobacter baumannii 50/113 (44%) followed by Klebsiella pneumoniae 44/113 (40%) and Pseudomonas aeruginosa 6/113 (5.3%). The total Gram positive bacterial strains isolated were 84 (42.6%), coagulase negative Staphylococci 55 (66%) with MDRs (89%) were the most common isolates followed by Staphylococcus aureus 15 (17.8%). Different antibiotics were used against these isolates; Gram- negative isolates showed high resistance rates to ceftazidime, gentamicin, amikacin and ertapenem. A. baumannii were the most frequent MDROs (94%), and the highest resistance rates in Gram-positive strains were observed toward ampicillin, oxacillin, ampicillin/sulbactam and Cefoxitin, representing 90% of total MDR Gram-positive isolates. ESBL and MRS were identified in most of strains. The prevalence of antibiotic resistance was high for both Gram negative and Gram positive isolates. This prevalence requires strict infection prevention and control intervention, continuous monitoring, implementation of effective antibiotic stewardship, immediate, concerted and collaborative action to monitor its prevalence and spread in the hospital.

Bacterial enrichment prior to third-generation metagenomic sequencing improves detection of BRD pathogens and genetic determinants of antimicrobial resistance in feedlot cattle

IntroductionBovine respiratory disease (BRD) is one of the most important animal health problems in the beef industry. While bacterial culture and antimicrobial susceptibility testing have been used for diagnostic testing, the common practice of examining one isolate per species does not fully reflect the bacterial population in the sample. In contrast, a recent study with metagenomic sequencing of nasal swabs from feedlot cattle is promising in terms of bacterial pathogen identification and detection of antimicrobial resistance genes (ARGs). However, the sensitivity of metagenomic sequencing was impeded by the high proportion of host biomass in the nasal swab samples.MethodsThis pilot study employed a non-selective bacterial enrichment step before nucleic acid extraction to increase the relative proportion of bacterial DNA for sequencing.ResultsNon-selective bacterial enrichment increased the proportion of bacteria relative to host sequence data, allowing increased detection of BRD pathogens compared with unenriched samples. This process also allowed for enhanced detection of ARGs with species-level resolution, including detection of ARGs for bacterial species of interest that were not targeted for culture and susceptibility testing. The long-read sequencing approach enabled ARG detection on individual bacterial reads without the need for assembly. Metagenomics following non-selective bacterial enrichment resulted in substantial agreement for four of six comparisons with culture for respiratory bacteria and substantial or better correlation with qPCR. Comparison between isolate susceptibility results and detection of ARGs was best for macrolide ARGs in Mannheimia haemolytica reads but was also substantial for sulfonamide ARGs within M. haemolytica and Pasteurella multocida reads and tetracycline ARGs in Histophilus somni reads.DiscussionBy increasing the proportion of bacterial DNA relative to host DNA through non-selective enrichment, we demonstrated a corresponding increase in the proportion of sequencing data identifying BRD-associated pathogens and ARGs in deep nasopharyngeal swabs from feedlot cattle using long-read metagenomic sequencing. This method shows promise as a detection strategy for BRD pathogens and ARGs and strikes a balance between processing time, input costs, and generation of on-target data. This approach could serve as a valuable tool to inform antimicrobial management for BRD and support antimicrobial stewardship.

Virulence and Antimicrobial Resistance of Listeria monocytogenes Isolated from Ready-to-Eat Food Products in Romania

Listeria monocytogenes (L. monocytogenes) poses a significant threat to food safety due to its ability to cause severe human illness and its resistance to various antibiotics and environmental conditions. This study investigated the prevalence, serotype distribution, virulence gene profiles, and antimicrobial resistance patterns of L. monocytogenes in ready-to-eat (RTE) food products from Romania. A total of 8151 samples were analyzed, including various processed dairy, bovine, poultry, pork, and fish products. Bacterial isolation was conducted using the classical standard method, followed by confirmation through biochemical and molecular testing. Among the isolated strains, serotypes 1/2a, 1/2b, and 1/2c were identified, with a prevalence of 75% for serotype 1/2a. Additionally, virulence genes specific to listeriolysin O (hlyA) and regulatory factor A (prfA) were detected in all isolates. Antimicrobial susceptibility testing revealed varying resistance patterns among the L. monocytogenes strains. Trimethoprim-sulfamethoxazole and oxacillin showed the highest prevalence of resistance at 26.92% and 23.07%, respectively. However, all strains remained susceptible to ciprofloxacin, levofloxacin, and moxifloxacin. Notably, 23.07% of the isolates exhibited multidrug resistance, with the most common pattern being resistance to oxacillin, penicillin, and tetracycline. Analysis of antimicrobial resistance genes identified tetracycline resistance genes, particularly tet(C), tet(M), and tet(K), in a significant proportion of isolates. The presence of ampC and dfrD genes was also notable, indicating potential mechanisms of resistance. These results emphasize the necessity for ongoing surveillance of L. monocytogenes in RTE foods and emphasize the importance of thorough monitoring of antimicrobial resistance to guide public health strategies within the European Union.

Bacteriological profile and their antimicrobial susceptibility pattern among clinical suspected adult septicemia admitted patients: A study from tertiary care and teaching hospital

Objectives: The objective of this study is to determine the bacteriological profile and their antimicrobial susceptibility pattern among clinically suspected adult septicemia admitted patients and to study the correlation between the clinical presentation and inflammatory biomarkers (C-reactive protein [CRP] and Procalcitonin [PCT]) in the final outcomes of nosocomial sepsis in adult septicemia patients. Material and Methods: This is a descriptive cross-sectional study of 1-year duration from November 2022 to November 2023. The study has been approved from the Institutional Ethical Committee. Adult patients with a clinical suspected diagnosis of sepsis were admitted to the medicine ward of the tertiary hospital. Blood samples of adult sepsis suspected patients samples were taken for as a part of septicemia screening. Blood culture and sensitivity were performed according to standard guidelines. The sepsis inflammatory prognostic markers CRP and PCT test were evaluated according to manufactures instruction. Results: Out of 300 clinically suspected adult septicemia patients, 93 (31%) patients were isolated culture-positive sepsis while 207 (69%) patients were culture-negative sepsis. Gram-positive organisms were more (69%) as compared to Gram-negative organisms (31%). Staphylococcus aureus was predominant among Gram-positive organisms while Acinetobacter baumanii complex (9%) followed by Enterobacter spp. (8%) isolated in Gram-negative bacilli. Culture-positive sepsis patients have CRP level ≥3.2 mg/dL (80%) and the majority (80%) of these patients have reactive PCT. Conclusions: Successful treatment of bloodstream infection depends on early diagnosis and appropriate use of antimicrobial agents. Rapid identification results and antimicrobial susceptibility tests are essential for guiding clinicians in the selection of the most appropriate treatment for patients with bloodstream infections.

Prevalence of multidrug resistance Salmonella species isolated from clinical specimens at University of Gondar comprehensive specialized hospital Northwest Ethiopia: A retrospective study.

Multidrug resistance Salmonellosis remains an important public health problem globally. The disease is among the leading causes of morbidity and mortality in developing countries, but there have been limited recent studies about the prevalence, antimicrobial resistance, and multidrug resistance patterns of Salmonella isolates from various clinical specimens. Aimed to assess the prevalence, antimicrobial resistance, and multidrug resistance patterns of Salmonella isolates from clinical specimens at the University of Gondar Comprehensive Specialised Hospital, northwestern Ethiopia. A retrospective hospital-based cross-sectional study was conducted to determine the prevalence, antimicrobial resistance, and multidrug resistance patterns of isolated from all clinical specimens at the University of Gondar Salmonella Comprehensive Specialised Hospital from June 1st, 2017 to June 3rd, 2022. A total of 26,154 data points were collected using a checklist of records of laboratory registration. Clinical specimens were collected, inoculated, and incubated for about a week with visual inspection for growth and gram staining. The isolates were grown on MacConkey agar and Xylose Lysine Deoxycholate agar. Pure colonies were identified with a conventional biochemical test, and those unidentified at the species level were further identified by the analytical profile index-20E. Then, antimicrobial susceptibility was determined by the Kirby-Bauer disc diffusion technique. The multidrug resistance Salmonella isolates was identified using the criteria set by Magiorakos. Finally, the data was cleaned and checked for completeness and then entered into SPSS version 26 for analysis. Then the results were displayed using tables and figures. Of the total 26,154 Salmonella suspected clinical samples, 41 (0.16%) Salmonella species were isolated. Most of the Salmonella isolates, 19 (46.3%), were in the age group of less than 18 years, followed by the age group of 19-44 years, 11 (26.8%). In this study, S. enterica subsp. arizonae accounts for the highest 21 (51%), followed by S. paratyphi A 9 (22%). Of the Salmonella isolates, S. typhi were highly resistant to ampicillin (100%), followed by tetracycline and trimethoprim-sulfamethoxazole, each accounting for 83.3%. Furthermore, S. paratyphi A was resistant to ampicillin (100%), tetracycline (88.9%), and chloramphenicol (88.9%). The overall multi-drug resistance prevalence was 22 (53.7%; 95% CI: 39.7-61). Accordingly, S. paratyphi A was 100% multidrug-resistant, followed by S. typhi (66.6%). A low prevalence of Salmonella species was observed in the past six years. Moreover, most S. typhi and S. paratyphi strains in the study area were found to be resistant to routinely recommended antibiotics like ciprofloxacin and ceftriaxone, compared to what was reported earlier. In addition, all isolates of S. paratyphi A and the majority of S. typhi were multidrug resistant. Therefore, health professionals should consider antimicrobial susceptibility tests and use antibiotics with caution for Salmonellosis management.

Bloodstream Infection Caused by Erysipelothrix rhusiopathiae in an Immunocompetent Patient

Erysipelothrix rhusiopathiae is a facultative anaerobe Gram-positive bacillus, which is considered a zoonotic pathogen. E. rhusiopathiae causes erysipeloid, mainly in occupational groups such as veterinarians, slaughterhouse workers, farmers, and fishermen. Two cutaneous forms (localised and generalised) and a septicaemic form have been described. Here, we report the isolation of a strain of E. rhusiopathiae from a 56-year-old immunocompetent obese male admitted to Fondazione IRCCS Policlinico San Matteo Pavia (Italy). Blood cultures were collected and Gram-positive bacilli were observed. E. rhusiopathiae grew and was identified. Antimicrobial susceptibility tests were performed and interpreted with EUCAST breakpoints (PK-PD). The strain was susceptible to all the antibiotics tested, while it was intrinsically resistant to vancomycin. The clinical diagnosis of E. rhusiopathiae can be challenging, due to the broad spectrum of symptoms and potential side effects, including serious systemic infections such as heart diseases. In the case described, bacteraemia caused by E. rhusiopathiae was detected in a immunocompetent patient. Bacteraemia caused by E. rhusiopathiae is rare in immunocompetent people and blood cultures were proven to be essential for the diagnosis and underdiagnosis of this pathogen, which is possible due to its resemblance to other clinical manifestations.

Bacterial etiologies, antimicrobial susceptibility pattern and associated factors among patients suspected sterile body site infections at Debre Markos Comprehensive Specialized Hospital, Northwest Ethiopia

BackgroundSterile body locations are usually associated with clinical urgency and life-threatening illnesses, and they are typically contaminated with diverse bacterial etiologies. If the bacteria acquire resistance to antimicrobial drugs, the public health crisis will only worsen. In developing countries, drug-resistant bacteria are common because of poor surveillance, diagnostic capacity, and control measures. Early diagnosis, and assessing the drug resistance and factors associated with infection are important to combat the drug resistance and treatment. This study aimed to assess the bacterial etiologies, antimicrobial susceptibility pattern, and possible associated factors among patients suspected of sterile body sites.MethodsA hospital-based cross-sectional study was conducted from June 2022 to August 2022 at Debre Markos Comprehensive Specialized Hospital in Amhara regional state, Ethiopia. One hundred seven study participants were selected using consecutive convenient sampling techniques. A structured questionnaire was used to collect socio-demographic and clinical data. Gram stain was done for a preliminary report and inoculated into blood agar, MacConkey agar, and chocolate agar and incubated aerobically and micro aerobically at 37°C for 24 h. Antimicrobial susceptibility testing was done by the modified Kirby Bauer’s disk diffusion method. Data were analyzed using bivariate and multivariate logistic regression was used. A p-value less than 0.05 is considered as statistically significant.ResultsThe overall magnitude of sterile body site infection among study participants was 7.5% (14/187). The majority of the isolates were Gram-negative bacteria with the predominant species Enterobacter cloacae accounting for 28.57% (4/14). Among isolates 78.57%(11/14) of them were multidrug-resistant isolates. Being inpatient, co-morbidity, and alcohol consumption were significantly associated with sterile body site infection.ConclusionIn our study, Gram-negative bacteria were the predominant bacteria that infects sterile body fluid. The prevalence of multi-drug resistance bacteria isolates was significantly high. Therefore, before prescribing an empirical treatment, a medical professional should identify the bacterial etiology of sterile body fluids and the susceptibility of microbes to the drug.

Streptococcus suis serotype 4: a population with the potential pathogenicity in humans and pigs

: Streptococcus suis is a major bacterial pathogen in pigs and an emerging zoonotic pathogen. Different S. suis serotypes exhibit diverse characteristics in population structure and pathogenicity. Surveillance data highlight the significance of S. suis serotype 4 (SS4) in swine streptococcusis, a pathotype causing human infections. However, except for a few epidemiologic studies, the information on SS4 remains limited. In this study, we investigated the population structure, pathogenicity, and antimicrobial characteristics of SS4 based on 126 isolates, including one from a patient with septicemia. We discovered significant diversities within this population, clustering into six minimum core genome (MCG) groups (1, 2, 3, 4, 7-2, and 7-3) and five lineages. Two main clonal complexes (CCs), CC17 and CC94, belong to MCG groups 1 and 3, respectively. Numerous important putative virulence-associated genes are present in these two MCG groups, and 35.00% (7/20) of pig isolates from CC17, CC94, and CC839 (also belonging to MCG group 3) were highly virulent (mortality rate ≥ 80%) in zebrafish and mice, similar to the human isolate ID36054. Cytotoxicity assays showed that the human isolate and pig isolates of SS4 strains exhibit significant cytotoxicity to human cells. Antimicrobial susceptibility testing showed that 95.83% of strains isolated from our labs were classified as multidrug-resistant. Prophages were identified as the primary vehicle for antibiotic resistance genes. Our study demonstrates the public health threat posed by SS4, expanding the understanding of SS4 population structure and pathogenicity characteristics and providing valuable information for its surveillance and prevention.

Sedimentation field-flow fractionation for rapid phenotypic antimicrobial susceptibility testing: a pilot study.

The increase in antibiotic resistance is a major public health issue. The development of rapid antimicrobial susceptibility testing (AST) methods is becoming a priority to ensure early and appropriate antibiotic therapy. To evaluate sedimentation field-flow fractionation (SdFFF) as a method for performing AST in less than 3 h. SdFFF is based on the detection of early biophysical changes in bacteria, using a chromatographic-type technology. One hundred clinical Escherichia coli strains were studied. A calibrated bacterial suspension was incubated for 2 h at 37°C in the absence (untreated) or presence (treated) of five antibiotics used at EUCAST breakpoint concentrations. Bacterial suspensions were then injected into the SdFFF machine. For each E. coli isolate, retention times and elution profiles of antibiotic-treated bacteria were compared with retention times and elution profiles of untreated bacteria. Algorithms comparing retention times and elution profiles were used to determine if the strain was susceptible or resistant. Performance evaluation was done according to CLSI and the ISO standard 20776-2:2021 with broth microdilution used as the reference method. AST results from SdFFF were obtained in less than 3 h. SdFFF showed high categorical agreement (99.8%), sensitivity (99.5%) and specificity (100.0%) with broth microdilution. Results for each antimicrobial were also in agreement with the ISO 20776-2 recommendations, with sensitivity and specificity of ≥95.0%. This study showed that SdFFF can be used as a rapid, accurate and reliable phenotypic AST method with a turnaround time of less than 3 h.

Exploiting Image Processing and Artificial Intelligence Techniques for the Determination of Antimicrobial Susceptibility

Exploiting Image Processing and Artificial Intelligence Techniques for the Determination of Antimicrobial Susceptibility

Genotypic insights to Panton-Valentine leukocidin positive methicillin-resistant Staphylococcus aureus isolated from cattle mastitis.

In this research communication we investigate the prevalence and antimicrobial susceptibility of S. aureus harboring virulent genes responsible for mastitis in cattle of Punjab, Pakistan. A total of 690 milk samples were collected from commercial dairy farms for analysis of the prevalence of subclinical and clinical mastitis and isolation of S. aureus. Virulence ability and methicillin resistance in S. aureus (MRSA) was determined by targeting the pvl (the gene for Panton-Valentine leukocidin) and mecA genes, respectively. A total of 175 S. aureus isolates exhibiting prevalence of pvl gene (6.28%) and mecA gene (22.28%) were determined. Antimicrobial susceptibility testing of pvl positive and negative MRSA against different classes of antibiotics revealed 100% resistance against β-lactams while 100% sensitivity towards tylosin and linezolid.

Molecular characterization and bivalent vaccine development of Aeromonas hydrophila and Aeromonas veronii in Nile tilapia (Oreochromis niloticus)

In the present study, nine strains of Aeromonas spp. were isolated from diseased Nile tilapia in Thailand and identified based on 16S rRNA and gyrB gene sequences and multilocus sequence typing (MLST) analysis. Phenotypic characterization was performed for all the isolates. For the antimicrobial susceptibility test, all isolates were resistant to amoxicillin, whereas most of the isolates were susceptible to enrofloxacin. Pathogenicity analysis revealed that most A. hydrophila strains were highly virulent to fish, corresponding with the hemolytic activity test demonstrating that clear hemolysis occurred on sheep blood agar. To develop a vaccine for fish against A. veronii and A. hydrophila infection, a bivalent vaccine based on the formalin-killed cells (FKC) of A. veronii A5 and A. hydrophila A9, which showed higher virulence to fish, was prepared. This FKC vaccine was administered to Nile tilapia by intraperitoneal injection. The booster vaccination was conducted at 4 weeks after the first vaccination. The specific antibody titer was evaluated during rearing since the first vaccination, and then at 8 weeks after the first vaccination, the fish were challenged with A. veronii A5 and A. hydrophila A9 via intraperitoneal injection. There is not significance different in relative percentage survival of the vaccinated fish against A. veronii (63.49 ± 19.51%) and A. hydrophila (93.33 ± 6.67%). These results suggest that this candidate bivalent vaccine is effective against both A. veronii and A. hydrophila infection in Nile tilapia and could be an “motile Aeromonas septicemia (MAS)” control measure. However, to obtain the promising vaccine efficacy, the optimization of vaccine formulation might be achieved and be validated vaccine efficacy in field trial.