Marzia Rahman

Salmonella spp. is a major foodborne pathogen in poultry. The rise of multidrug-resistant (MDR) strains poses a serious threat to both animal and public health. The current study evaluated the prevalence, antimicrobial susceptibility, and molecular resistance traits of Salmonella spp. from four commercial poultry farms in Bangladesh. The study screened 325 samples on Salmonella-Shigella (SS) agar and found 63 (19.38%) with presumptive Salmonella colonies. PCR targeting the invA gene confirmed 30 isolates, giving an overall prevalence of 9.23%. The distribution of isolates did not differ significantly across the four farms (p = 0.70). Antimicrobial testing revealed the highest resistance to oxytetracycline (86.67%), streptomycin (70.00%), and amoxicillin (63.33%). Resistance to florfenicol and chloramphenicol was lower (33.33% and 30.00%, respectively). All 30 confirmed isolates (100%) were multidrug-resistant. Their multiple antibiotic resistance (MAR) indices ranged from 0.375 to 0.625. Molecular screening showed tetA was the most common resistance gene (96.67%), followed by aadA1 (80.00%), blaTEM and qnrA (66.67% each), floR (40.00%), and cat1 (36.67%). We observed that genotypic detection often exceeded phenotypic resistance, especially for ampicillin/blaTEM and ciprofloxacin/qnrA. We detected the class 1 integron gene (intI1) in 40.00% of isolates. Every intI1-positive isolate showed an MDR phenotype and the highest MAR index (0.625). These results suggest that poultry farms act as critical reservoirs for MDR Salmonella. They also point to the farm environment as an active site for horizontal gene transfer, underscoring the urgent need for responsible antimicrobial use and ongoing molecular surveillance.

Multidrug‐resistant (MDR) Salmonella spp. is regarded as a perilous menace of public health significance. This research finding was carried out to investigate the prevalence of MDR Salmonella spp. in cloacal swabs of healthy layer birds and egg surface washing along with their resistance patterns and some associated resistance gene detection. In total, 120 samples consisting of 60 cloacal swabs and 60 eggs were collected from three different layer farms located at Mymensingh, Bangladesh, and subjected to various classical and molecular approaches. Antibiotic resistance patterns were investigated phenotypically using the Kirby–Bauer disk diffusion method and genotypically by detection of respective resistance genes. The overall prevalence rate of Salmonella spp. was 29% (95% CI: 18.077%−33.255%) and sample‐wise prevalence was 23% (95% CI: 14.415%−26.918%) in cloacal swab and 35% (95% CI: 22.043%−39.956%) in egg surface washing, respectively. Antibiotic susceptibility test revealed that the highest resistance was found to ampicillin 94.29% (95% CI: 86.65%–99.96%) followed by oxytetracycline 80.00%, (95% CI: 65.23%–98.03%), and erythromycin 65.72% (95% CI: 56.73%–75.41%), 45.71%, (95% CI: 33.039%–58.08%) to streptomycin, whereas the highest sensitivity was observed against florfenicol 74.29% (95% CI: 62.91%–85.28%), followed by ciprofloxacin (68.57%, 95% CI: 62.80%−73.66%), and sulphamethoxazole (68.57%, 95% CI: 53.48%–78.97%). The isolates were also found to be MDR as 80% (28/35) isolates (95% CI: 75.80%–86.69%) possessed a MAR index ranging between 0.33 and 0.89. On average, 19 isolates (54.28%; 95% CI: 26.90%−85.17%) were resistant to 5 ̶ 8 antibiotics of seven classes, which is really alarming for public health significance. Based on PCR results, different resistant genes blaTEM, tetA, aadA1, cat1, and flo- R were amplified from 100%, 85.71%, 77.14%, 62.86%, and 37.14% of the isolates. Due to increased drug resistance, antibiotics and other antimicrobial drugs are becoming ineffective for the medication of both human and animal infections. Further investigations are also suggested to cope with antimicrobial resistance through this research study.

This study reports the complete genome sequencing of the duck enteritis virus strain YLBRDP_11 isolated from liver tissue of ducks during a local outbreak in Netrokona district, Northern part of Bangladesh. The viral genome consists of 161,633 bp encoding 74 proteins with a GC content of 44.9%.

Salmonella enterica is a major foodborne pathogen that poses significant risks to public health and poultry production. This study aimed to investigate the distribution, serovar types, virulence genes, and antimicrobial resistance (AMR) profiles of S. enterica isolated from chickens in Bangladesh. A total of 250 samples from broiler ( n = 100), layer ( n = 100), and Sonali ( n = 50) chickens were collected across four districts in Bangladesh and analyzed using polymerase chain reaction (PCR) and MALDI‐TOF for identification and serotyping. The presence of virulence and AMR genes was assessed via PCR, while phenotypic resistance was determined using the disk diffusion method. In PCR, S. enterica was detected in 14.4% (36/250) of the samples, with significantly higher prevalence in layers compared with broilers and Sonali. Among the isolates, 61.1% (22/36) were identified as serovar Typhimurium, 27.8% (10/36) as Enteritidis, and 11.1% (4/36) remained untyped. All isolates harbored the invA , stn , sivH , and lpfA virulence genes, while hilA and spvC were detected in 97.2% and 63.9% of the isolates, respectively. High phenotypic resistance was observed to sulfamethoxazole (94.4%), sulfonamide (91.7%), nitrofurantoin (55.5%), and ampicillin (52.8%), with 86.1% of isolates classified as multidrug‐resistant. Genotypically, resistance genes aadA2 and SUL1 were most common (94.4%), followed by bla _CMY‐9 (75%) and bla _SHV (52.8%), with variations across serovars and poultry types. These findings highlight the high burden of antimicrobial‐resistant S. enterica serovars in Bangladeshi poultry and underscore the need for continuous surveillance and prudent antimicrobial use.

A lytic bacteriophage, BAU.Micro_SLP-22, was isolated from drain water in search of bio-controlling agents against avian salmonellosis. The phage genome is comprised of 59,738 bp with 56.96% guanine–cytosine content, encoding 81 protein-coding genes containing no transfer RNAs, antibiotic resistance, virulence, temperate marker, and clustered regularly interspaced short palindromic repeat coding sequences.

Escherichia coli lytic bacteriophage BAU.Micro_ELP-22 was isolated from sewage wastewater as a therapeutic agent alternative to antibiotics. The phage genome is 373,488 bp in length, encoding 744 protein-coding sequences and 7 tRNAs, and contains no antibiotic resistance, virulence, or temperate marker genes, which specifies its potentiality as a compatible phage therapy candidate.

Objective: The methodology employed in this research was designed to identify and characterize the infectious bursal disease virus (IBDV) at the molecular level, originating from recent outbreaks in Bangladesh. Materials and Methods: The IBDV outbreak farm was investigated, and bursa of Fabricius (BF) specimens were acquired from infected chickens. Initially, viruses in the processed samples were detected in chicken embryo fibroblast (CEF) cells, and the RT-PCR method was used to confirm IBDV. The positive samples were injected through chorioallantoic membrane route into the embryo of a 10-day-old specific pathogen-free (SPF) egg for virus isolation and pathogenicity testing. Finally, we sequenced the VP2 gene to identify phylogenetic relationships and detect mutations. Results: From the 77 collected samples, 42.85% (33/77) were found positive for cytopathic effects in CEF cells, and IBDV was detected in 31.16% (24/77) of the samples by RT-PCR. IBDV was isolated in SPF chicken embryos. In the pathogenicity test, infectious bursal disease was evident in seronegative chickens with visible signs of disease. Sequence analysis shows that the broiler-isolated viruses clustered with genotype A3B2 and backyard chickens with genotype A1B1. The presence of amino acid motifs for virulence markers was revealed in the partially sequenced VP2 gene with a mutation at S254G in four IBDV isolates from broilers. However, amino acids for virulence markers were absent in two isolates from backyard chickens, which shows sequence homology with IBDV classic strains. Conclusion: In this study, we identified and characterized circulating reassorted IBDV from vaccinated broilers, which may be one of the major causes of vaccination failure in broilers.

Objective: This study focused on the antibiogram profiling of Staphylococcus aureus and coagu¬lase-negative Staphylococcus spp. (CoNS) and the detection of icaA and blaZ genes from bovine raw milk samples. Materials and Methods: Bovine milk samples were collected from dairy farms, and Staphylococcus spp. were isolated and identified via conventional and molecular screening. Disk diffusion test (DDT) was implemented to determine the resistance pattern. Biofilm and β-lactamase-produc¬ing Staphylococcus spp. were identified via amplification of the icaA and blaZ genes. Methicillin-resistant Staphylococcus aureus and CoNS were identified by DDT and PCR of the mecA gene. Results: From 63 samples, 35 were confirmed as Staphylococcus spp., of which 16 (25.39%) S. aureus isolates were coagulase-positive, while 19 (30.16%) were negative. PCR confirmed that 50% (8/16) of S. aureus and 36.84% (7/19) of CoNS possessed the icaA gene. All S. aureus iso¬lates were found resistant to penicillin-G (P) both phenotypically and genotypically. The isolates were also resistant to erythromycin (ERY) and oxytetracycline (TET). While CoNS showed high to reduced resistance against P, TET, ERY, and azithromycin, no S. aureus isolates were resistant to sulfamethoxazole, while 10.53% of CoNS isolates were. All S. aureus and CoNS isolates were sus¬ceptible to vancomycin and gentamicin. MR was exhibited by 37.5% of S. aureus and 42.10% of CoNS isolates. Moreover, S. aureus and CoNS had 56.25% and 52.63% multidrug-resistant (MDR) isolates, respectively. Conclusion: The present study revealed the presence of a biofilm-producing, MDR staphylococcal strain in milk that might endanger consumers. Routine surveillance and monitoring, along with antimicrobial resistance learning, can reduce risks.

The eradication of staphylococcal infections has become more difficult due to the development of antibiotic resistance and virulence in biofilm-forming Staphylococcus aureus. The presence of the life-threatening zoonotic pathogen, methicillin-resistant S. aureus (MRSA), in foods indicates a public health issue. This study, therefore, aimed to determine virulence factors and methicillin resistance in biofilm-forming S. aureus isolates from different foods and food handlers. A total of 100 PCR-positive S. aureus isolates (97 biofilm formers and three non-biofilm formers) were screened using the disk diffusion method and PCR assay. By PCR, genes encoding virulence factors, e.g., enterotoxin (sea, 30%, 95% CI: 21.90–39.59%), toxic shock syndrome toxin (tst, 20%, 95% CI: 13.34–28.88%), and Panton–Valentine leukocidin toxin (PVL, 15%, 95% CI: 9.31–23.28%), were detected in the S. aureus isolates. By the disk diffusion method, 100% (95% CI: 96.30–100.00%) of S. aureus isolates were phenotypically MRSA in nature, showing 100% resistance to oxacillin and cefoxitin. Moreover, the methicillin-resistant gene mecA was found in 61 (61%, 95% CI: 51.20–69.98%) MRSA isolates. Furthermore, all the S. aureus isolates were phenotypically resistant to ampicillin and penicillin, 30% to erythromycin, and 11% to gentamycin. Among them, 51% (95% CI: 41.35–60.58%) of S. aureus isolates were phenotypically multidrug-resistant in nature, and the multiple antibiotic resistance index varied from 0.33 to 0.55. Genes encoding resistance to beta-lactams (blaZ, 100%, 95% CI: 96.30–100.00%) and tetracyclines (tetA and tetC, 3%, 95% CI: 0.82–8.45%) were found positive in the S. aureus isolates. Genes encoding virulence determinants and MRSA were significantly (p < 0.05) higher in strong biofilm-forming S. aureus than in moderate and non-biofilm-forming isolates. To our knowledge, this is the first study in Bangladesh to incorporate preliminary data on the occurrence of virulence determinants and methicillin resistance, including resistance to clinically important antibiotics, in biofilm-forming S. aureus isolates from different foods and food handlers in Bangladesh, emphasizing a potential threat to human health.