Indian Journal of Medical Microbiology最新文献

Introduction: Shigella is a highly infectious diarrheal pathogen in developing countries. The increasing number of MDR isolates is an emerging problem in resource-limited settings such as India.

Hypothesis/gap statement: Detecting resistance genes and virulence genes of Shigella species can help plan empirical therapy and aid in future vaccine development.

Aim: This study was conducted to decipher the virulence and antimicrobial resistance among our Shigella isolates using targeted PCR.

Methods: The antimicrobial susceptibility testing of all Shigella isolates was done as per the CLSI 2021 using the Kirby-Bauer disc diffusion method. The genomic DNA was subjected to PCR for the detection of resistance genes and virulence genes. The contig sequence of positive amplicons was compared and analysed using BLAST (Basic Local Alignment Search Tool, NCBI) and the translated protein by ExPASy (Expert Protein Analysis System) server.

Results: Sequence determination of the QRDRs of gyrA,gyrB, parC and parE genes showed mutations in gyrA and parC. In GyrA at Gln69/Trp, Phe71/Ser, Ser72/Pro, Met75/Leu, Ser90/Cys, Met94/Leu, His106/Pro, Asn161/His, Thr163/Ala and in ParC at Ala64/Asp; aac-(6')Ib-cr were detected in 95.9% (215/224) and qnrS in 71.8% (161/224) of the isolates respectively. Bla_OXA was found in 92.8% (208/224), while bla_TEM in 37.9% (85/224) and bla_CTX in 8.0% (18/224); mphA was found in 19.4% (4/21) S.sonnei tested, of which 2 had azithromycin MIC of 64mcg/ml. IpaH was found in all the isolates, but the ompA gene, as well as the outer membrane protein A, was absent in 5 isolates of S.flexneri. The isolates of S.sonnei which showed resistance to azithromycin had IncFII, K and F plasmid types and the mphA gene.

Conclusion: The emergence of azithromycin resistance among Shigella is a major challenge in controlling multidrug-resistant Shigella. The absence of the ompA protein in some of our isolates limits its use as a potential vaccine candidate.

Background: The increasing isolation of penicillin-susceptible Staphylococcus aureus (PSSA) has renewed interest in benzylpenicillin (penicillin G, PCG) for targeted therapy. However, blaZ-encoded inducible penicillinase may not be detected by routine susceptibility testing. This study evaluated the diagnostic performance of phenotypic penicillinase detection methods applicable to routine clinical laboratories, using blaZ polymerase chain reaction (PCR) as the reference standard.

Materials and methods: A total of 379 non-duplicate S. aureus isolates with a PCG minimum inhibitory concentration (MIC) ≤0.12 μg/mL were collected at a single institution between January 2020 and July 2024. The blaZ gene was detected by PCR. Phenotypic methods included low-range MIC determination by Etest, disk diffusion using PCG 10 U and PCG 1 U disks, zone-edge testing, and nitrocefin-based assays. Sensitivity and specificity were calculated relative to blaZ PCR results.

Results: Among the 379 isolates, 20 (5.3%) were blaZ-positive despite being classified as PCG-susceptible by both CLSI and EUCAST criteria. Neither low-range MIC values nor inhibition zone diameters reliably differentiated blaZ-positive from blaZ-negative isolates. The zone-edge test demonstrated the highest diagnostic performance, with a sensitivity of 95.0% and specificity of 93.3% when performed using a PCG 1 U disk according to EUCAST methodology. Nitrocefin-based assays showed poor sensitivity (<50%).

Conclusion: MIC- and zone diameter-based methods alone are insufficient to detect penicillinase-producing S. aureus among PCG-susceptible isolates. The zone-edge test using a PCG 1 U disk is a practical and reliable phenotypic confirmatory method suitable for routine clinical microbiology laboratories to support safe PCG therapy.

Paragonimiasis, a parasitic infection caused by Paragonimus westermanii, presents with a range of symptoms, including chronic cough, chest pain, and hemoptysis, often mimicking tuberculosis. This case report describes the first documented case of Paragonimus westermanii infection in Bihar, India, presenting with hemoptysis. The patient, a 40-year-old female with a history of consuming smoked and improperly cooked crabs, exhibited eosinophilia and chest radiographic abnormalities. Microscopic examination of the sputum revealed characteristic Paragonimus eggs. Praziquantel treatment led to rapid symptom resolution. This case underscores the importance of considering paragonimiasis as an important differential diagnosis in regions where it is not widely recognized.