Progress Report: Antimicrobial Drug Discovery in the Resistance Era.

Antibiotic resistance continues to be a most serious threat to public health. This situation demands that the scientific community increase their efforts for the discovery of alternative strategies to circumvent the problems associated with conventional small molecule therapeutics. The Global Antimicrobial Resistance and Use Surveillance System (GLASS) Report (published in June 2021) discloses the rapidly increasing number of bacterial infections that are mainly caused by antimicrobial-resistant bacteria. These concerns have initiated various government agencies and other organizations to educate the public regarding the appropriate use of antibiotics. This review discusses a brief highlight on the timeline of antimicrobial drug discovery with a special emphasis on the historical development of antimicrobial resistance. In addition, new antimicrobial targets and approaches, recent developments in drug screening, design, and delivery were covered. This review also discusses the emergence and roles of various antibiotic adjuvants and combination therapies while shedding light on current challenges and future perspectives. Overall, the emergence of resistant microbial strains has challenged drug discovery but their efforts to develop alternative technologies such as nanomaterials seem to be promising for the future.

Prevalence, multidrug-resistance and risk factors for AmpC ß-lactamases producing Escherichia coli from hospitalized patients.

INTRODUCTION: Multi-drug resistance among AmpC ß-lactamases producing Escherichia coli isolates is alarming. The study aimed to know the prevalence and presumptive antibiogram of AmpC producing Escherichia coli isolates and to determine the associated risk factors. METHODOLOGY: Escherichia coli isolated from various clinical specimens from hospitalized patients during the study period (January 2018- December 2018) were taken for the study. Standard biochemical reactions were used for organism identification. Antibiotic susceptibility testing was done using Kirby-Bauer method as per CLSI guidelines. Cefoxitin resistance was taken as screening tool to detect AmpC producing strains. The phenotypic confirmation was done using modified three-dimensional test. Multiplex PCR was used to detect pAmpC. RESULTS: A total non-duplicate consecutive 470 Escherichia coli were isolated from various clinical specimens of hospitalized patients during the study period. Cefoxitin resistance was observed in 51.9% (244/470). Modified three dimensional test was positive in 115/244 (47.1%) strains. Genotypic characterization of phenotypic positive AmpC strains showed presence of CIT and DHA genes among 33/115 and 19/115 isolates respectively. The overall prevalence of pAmpC producing E. coli was found to be 52/470 (11.1%). Multidrug resistance (MDR) was observed in 42/52 (80.7%) pAmpC strains. Antimicrobial use, prolonged hospitalization and interventions were associated risk factors for AmpC producing isolates. CONCLUSIONS: A high prevalence of multidrug resistance among AmpC producing strains suggests plasmid mediated spread of drug resistance in E. coli. Every hospital should formulate and implement infection control policies at-least for the risk group patients to control the dissemination of such microbes as infection prevention is better than infection control.

Papain-cetylpyridinium chloride and pepsin-cetylpyridinium chloride; two novel, highly sensitive, concentration, digestion and decontamination techniques for culturing mycobacteria from clinically suspected pulmonary tuberculosis cases.

Mycobacterial culture remains the gold standard for the diagnosis of tuberculosis. However, an appropriate digestion and decontamination method (DDM) is essential for the effective recovery of tubercle bacilli in culture. Therefore, the current study was designed to compare the performance of papain-cetylpyridinium chloride [papain-CPC] and pepsin-cetylpyridinium chloride [pepsin-CPC] DDMs against N-acetyl L-Cysteine-sodium hydroxide (NALC-NaOH) DDM for recovery of mycobacteria from clinically suspected pulmonary tuberculosis cases. To evaluate papain-CPC, pepsin-CPC and NALC-NaOH DDMs, sputum samples (N = 1381) were cultured on Löwenstein-Jensen medium and the results were compared. The papain-CPC DDM showed sensitivity, specificity, positive predictive value, and negative predictive value of 100%, 93.27%, 71.7%, and 100%, respectively as compared to NALC-NaOH DDM. Similarly, pepsin-CPC DDM demonstrated sensitivity, specificity, positive predictive value and negative predictive value of 98.94%, 94.7%, 76.11%, and 99.81%, respectively. In summary, both papain-CPC and pepsin-CPC DDMs are highly sensitive and specific techniques for recovery of mycobacteria as compared to NALC-NaOH DDM. However, when the overall performances of all DDMs compared, papain-CPC DDM isolated increased number of mycobacterial isolates with comparatively higher numbers of colonies on LJ media than both pepsin-CPC and NALC-NaOH DDMs, indicating its potential to replace the NALC-NaOH DDM for recovery of mycobacteria from sputum samples.

Modified combined disc test (mCDT): a novel, labor-saving and 4 times cheaper method to differentiate Class A, B and D carbapenemase-producing Klebsiella species.

Carbapenemase-producing organisms have been an immense public health problem in recent years. Combined disc test (CDT) is a simple and widely used phenotypic method for carbapenemase detection, especially in developing countries. This study evaluates the performance of modified combined disc test (mCDT), a novel and 4 times cheaper method than CDT. In total, 572 (15.5%) Klebsiella spp. including 81 (14.2%) carbapenemase producers were isolated from 3993 clinical samples. Both mCDT and CDT showed similar sensitivity, specificity, positive predictive value, and negative predictive value for the differentiation of Class A, B, and D carbapenemase-producing Klebsiella spp.

Modified Carba NP Test: Simple and rapid method to differentiate KPC- and MBL-producing Klebsiella species.

BACKGROUND: The aim of this study was to evaluate the modified Carba NP test to differentiate KPC (Klebsiella pneumoniae carbapenemase)- and MBL (metallo-ß-lactamase)-producing Klebsiella species. METHODS: A total of 508 non-duplicate clinical isolates of Klebsiella spp. were processed by modified Carba NP and combined disc tests which were further confirmed by conventional polymerase chain reaction (PCR), a gold standard method for statistical analysis. RESULTS: Modified Carba NP test demonstrated 91.7% sensitivity, 100% specificity, 100% positive predictive value (PPV) and 99.8% negative predictive value (NPV) for KPC and 96.7%, 100%, 100%, and 99.5% for MBL detection, respectively. CONCLUSION: The performance of modified Carba NP test was significantly better than combined disc test, fulfilling the requirement of simple and rapid test for clinical applications.

Saliva as a tool in the detection of hepatitis B surface antigen in patients.

Viral hepatitis is one of the world's most common viral illnesses. Hepatitis B virus infection is a global health problem, and its importance in dentistry is well recognized. The role of saliva in the transmission of hepatitis B makes dentists and dental personnel particularly vulnerable to hepatitis B infection. The objective of this study was to predict the efficacy of saliva as a tool for the detection of hepatitis B surface antigen (HBsAg), which is the hallmark of the infection. The study group comprised 70 patients, 35 of whom were known to be hepatitis B infection seropositive (test group) and the remaining 35 who did not have hepatitis B (control group). All of the subjects were tested with enzyme-linked immunosorbant assay. Of the 35 seropositive subjects, HBsAg was detected in the saliva samples of 26 subjects. The sensitivity and specificity of saliva as a diagnostic tool for detecting HBsAg antigen in this study was 74.29% and 100%, respectively. Because of its noninvasive nature, saliva can be effectively used for large-scale Hepatitis B virus detection.

Effect of denture wearing on occurrence of fungal Isolates in the oral cavity: A pilot study.

OBJECTIVES: An attempt was made to evaluate effect of denture wearing on occurrence of fungal isolates in the oral cavity before and after complete denture insertion. METHOD: Twenty five completely edentulous patients were selected; swab samples were collected intraorally before fabrication of complete dentures from labial vestibular area and after complete denture fabrication (one and four days after denture insertion). Further these samples were inoculated and incubated. RESULTS: In nineteen patients no isolate of fungus before denture insertion as well as 4 days after denture insertion was found. In two subject results were false positive (contamination from environment), and in four patients there was increase in growth but not much significant increase of growth of fungal isolates was seen (mild growth of fungus only after denture insertion). One of the major finding of this study was overall occurrence of fungal isolates (before and after denture insertion) in the oral cavity were not significant. Key words:Fungal isolates, denture stomatitis, denture, Candida, insertion.