Involvement of a 43-kilodalton outer membrane protein in beta-lactam resistance of Shigella dysenteriae

Study of Antimicrobial Resistance (AMR) in Shigella spp. in India

Antimicrobial agents are essential in reducing illness and mortality brought on by infectious diseases in both humans and animals. However, the therapeutic effect of antibiotics has diminished due to an increase in antimicrobial drug resistance (AMR). This article provides a retrospective analysis of AMR in Shigella infections in India, showing a rise in resistance that has contributed to a global burden. Shigella spp. are widespread and the second-leading cause of diarrheal death in people of all ages. The frequency and mortality rates of Shigella infections are decreased by antibiotic treatment. However, the growth of broad-spectrum antibiotic resistance is making it more difficult to treat many illnesses. Reduced cell permeability, efflux pumps, and the presence of enzymes that break down antibiotics are the causes of resistance. AMR is a multifaceted and cross-sectoral problem that affects humans, animals, food, and the environment. As a result, there is a growing need for new therapeutic approaches, and ongoing surveillance of Shigella spp. infections which should definitely be improved for disease prevention and management. This review emphasizes on the epidemiological data of India, and antimicrobial resistance in Shigella spp.

Prevalence of Antibiotic-Resistant Shigella spp. in Bangladesh: A Systematic Review and Meta-Analysis of 44,519 Samples

Shigella is the leading global etiological agent of shigellosis, especially in poor and underdeveloped or developing nations with insufficient sanitation such as Bangladesh. Antibiotics are the only treatment option for the shigellosis caused by Shigella spp. as no effective vaccine exists. However, the emergence of antimicrobial resistance (AMR) poses a serious global public health concern. Therefore, a systematic review and meta-analysis were conducted to establish the overall drug resistance pattern against Shigella spp. in Bangladesh. The databases of PubMed, Web of Science, Scopus, and Google Scholar were searched for relevant studies. This investigation comprised 28 studies with 44,519 samples. Forest and funnel plots showed any-drug, mono-drug, and multi-drug resistance. Any fluoroquinolone had a resistance rate of 61.9% (95% CI: 45.7-83.8%), any trimethoprim-sulfamethoxazole-60.8% (95% CI: 52.4-70.5%), any azithromycin-38.8% (95% CI: 19.6-76.9%), any nalidixic acid-36.2% (95% CI: 14.2-92.4%), any ampicillin-34.5% (95% CI: 25.0-47.8%), and any ciprofloxacin-31.1% (95% CI: 11.9-81.3%). Multi-drug-resistant Shigella spp. exhibited a prevalence of 33.4% (95% CI: 17.3-64.5%), compared to 2.6% to 3.8% for mono-drug-resistant strains. Since resistance to commonly used antibiotics and multidrug resistance were higher, a judicious use of antibiotics, the promotion of infection control measures, and the implementation of antimicrobial surveillance and monitoring programs are required to tackle the therapeutic challenges of shigellosis.

Toward a Shigella Vaccine: Opportunities and Challenges to Fight an Antimicrobial-Resistant Pathogen

Shigellosis causes more than 200,000 deaths worldwide and most of this burden falls on Low- and Middle-Income Countries (LMICs), with a particular incidence in children under 5 years of age. In the last decades, Shigella has become even more worrisome because of the onset of antimicrobial-resistant strains (AMR). Indeed, the WHO has listed Shigella as one of the priority pathogens for the development of new interventions. To date, there are no broadly available vaccines against shigellosis, but several candidates are being evaluated in preclinical and clinical studies, bringing to light very important data and information. With the aim to facilitate the understanding of the state-of-the-art of Shigella vaccine development, here we report what is known about Shigella epidemiology and pathogenesis with a focus on virulence factors and potential antigens for vaccine development. We discuss immunity after natural infection and immunization. In addition, we highlight the main characteristics of the different technologies that have been applied for the development of a vaccine with broad protection against Shigella.

Antimicrobial resistance in shigellosis: A surveillance study among urban and rural children over 20 years in Bangladesh

Antimicrobial resistance against shigellosis is increasingly alarming. However, evidence-based knowledge gaps regarding the changing trends of shigellosis in Bangladesh exist due to the scarcity of longitudinal data on antimicrobial resistance. Our study evaluated the last 20 years antimicrobial resistance patterns against shigellosis among under-5 children in the urban and rural sites of Bangladesh. Data were extracted from the Diarrheal Disease Surveillance System (DDSS) of Dhaka Hospital (urban site) and Matlab Hospital (rural site) of the International Centre for Diarrheal Disease Research, Bangladesh (icddr,b) between January 2001 and December 2020. We studied culture-confirmed shigellosis cases from urban Dhaka Hospital (n = 883) and rural Matlab Hospital (n = 1263). Since 2001, a declining percentage of shigellosis in children observed in urban and rural sites. Moreover, higher isolation rates of Shigella were found in the rural site [1263/15684 (8.1%)] compared to the urban site [883/26804 (3.3%)] in the last 20 years. In both areas, S. flexneri was the predominant species. The upward trend of S. sonnei in both the study sites was statistically significant after adjusting for age and sex. WHO-recommended 1st line antibiotic ciprofloxacin resistance gradually reached more than 70% in both the urban and rural site by 2020. In multiple logistic regression after adjusting for age and sex, ciprofloxacin, azithromycin, mecillinam, ceftriaxone, and multidrug resistance (resistance to any two of these four drugs) among under-5 children were found to be increasing significantly (p<0.01) in the last 20 years in both sites. The study results underscore the importance of therapeutic interventions for shigellosis by appropriate drugs based on their current antibiogram for under-5 children. These observations may help policymakers in formulating better case management strategies for shigellosis.

Shigella: Antibiotic-Resistance Mechanisms And New Horizons For Treatment

Shigella spp. are a common cause of diarrheal disease and have remained an important pathogen responsible for increased rates of morbidity and mortality caused by dysentery each year around the globe. Antibiotic treatment of Shigella infections plays an essential role in reducing prevalence and death rates of the disease. However, treatment of these infections remains a challenge, due to the global rise in broad-spectrum resistance to many antibiotics. Drug resistance in Shigella spp. can result from many mechanisms, such as decrease in cellular permeability, extrusion of drugs by active efflux pumps, and overexpression of drug-modifying and -inactivating enzymes or target modification by mutation. Therefore, there is an increasing need for identification and evolution of alternative therapeutic strategies presenting innovative avenues against Shigella infections, as well as paying further attention to this infection. The current review focuses on various antibiotic-resistance mechanisms of Shigella spp. with a particular emphasis on epidemiology and new mechanisms of resistance and their acquisition, and also discusses the status of novel strategies for treatment of Shigella infection and vaccine candidates currently under evaluation in preclinical or clinical phases.

Differential expression of ompC and ompF in multidrug-resistant Shigella dysenteriae and Shigella flexneri by aqueous extract of Aegle marmelos, altering its susceptibility toward beta-lactam antibiotics

Steadily increasing resistance among Shigella to beta-lactams, aminoglycosides, and tetracycline has compromised the utility of these commonly used antimicrobial agents. Also, undesirable side effects of certain antibiotics have triggered immense interest in search of alternative therapies using medicinal plants. One such medicinal plant used since ancient times to cure diarrhea is Aegle marmelos. The present study exemplifies the susceptibility of beta-lactam-resistant Shigella dysenteriae and Shigella flexneri toward beta-lactam antibiotics, when grown in the presence of aqueous extract of A. marmelos (AEAM), by altering porin channels. This was demonstrated by antibiotic sensitivity test using disc diffusion method and MIC test. Susceptibility toward beta-lactam antibiotic is associated with changes in outer membrane porins OmpC (approximately 42 kDa) and OmpF (approximately 38 kDa) and cytosolic proteins of approximately 26 kDa, OmpR, a transcriptional regulator. Expression of ompF is increased in S. dysenteriae and S. flexneri grown in the presence of AEAM due to down-regulation of ompR, which is conformed by reverse transcriptase polymerase chain reaction. In conclusion, AEAM influences susceptibility of beta-lactam-resistant Shigella toward beta-lactam antibiotics by altering porin channels. Hence, AEAM along with beta-lactam can be used for treatment of multidrug-resistant Shigella.

Beta-lactam resistance and Enterobacteriaceae, United States

Extended-spectrum cephalosporins (ESC) are an important drug class for treating severe Salmonella infections. We screened the human collection from the National Antimicrobial Resistance Monitoring System 2000 for ESC resistance mechanisms. Of non-Typhi Salmonella tested, 3.2% (44/1,378) contained bla_CMY genes. Novel findings included bla_CMY-positive Escherichia coli O157:H7 and a bla_SHV-positive Salmonella isolate. CMY-positive isolates showed a ceftriaxone MIC >2 µg/mL.

Selection of cefoxitin-resistant bacteroides thetaiotaomicron mutants and mechanisms involved in beta-lactam resistance

The beta-lactam antibiotics are the most widely used of all the groups of antimicrobials, but beta-lactam resistance is increasingly common among members of the Bacteroides fragilis group. Three major mechanisms are involved in beta-lactam resistance, and they act together in certain instances. In the present study, 2 resistant mutants (238m and 1186m) of Bacteroides thetaiotaomicron, obtained from clinical isolates (238 and 1186) by selection with increasing concentrations of cefoxitin, showed decreased susceptibilities to cefoxitin and other beta-lactam antibiotics. Alterations in both penicillin-binding proteins (PBPs) and outer-membrane proteins (OMPs) were observed in the mutants in comparison with their parent strains. The similar alteration in OMPs was also observed in clinical isolates. In conclusion, the beta-lactam-resistant mutants of B. thetaiotaomicron with deficiency in both PBPs and OMPs can be selected for by exposure to cefoxitin, and several mechanisms are involved in the beta-lactam resistance in the strains investigated.

New findings in beta-lactam and metronidazole resistant Bacteroides fragilis group

Beta-lactam antibiotics and 5-nitroimidazoles have been extensively used against anaerobic bacteria. However, antibiotic resistance is increasingly common among anaerobic Gram-negative bacilli. The classical mechanisms of resistance to beta-lactams are, (1) production of beta-lactamases; (2) alteration of penicillin-binding proteins (PBPs); and (3) changes in outer membrane permeability to beta-lactams. The 5-nitroimidazole molecule is a prodrug whose activation depends upon reduction of the nitro group in the absence of oxygen. Decreased uptake and altered reduction are believed to be responsible for metronidazole resistance. Five nim genes (A, B, C, D and E) have been identified in Bacteroides fragilis group spp. that confer resistance to 5-nitroimidazole antibiotics. Knowledge of the status and the mechanisms of resistance is critical for both the selection of antimicrobial therapy and the design of new antimicrobial agents. The purpose of this article is to review the mechanisms for and the prevalence of beta-lactam and metronidazole resistance in strains belonging to the B. fragilis group.

Alterations in high molecular mass penicillin-binding protein 1 associated with beta-lactam resistance in Shigella dysenteriae

Beta-lactam resistance poses a major problem in the chemotherapy of shigellosis caused by Shigella dysenteriae. Such resistance may arise from alterations in the affinities or amounts of the penicillin-binding proteins (PBPs) for beta-lactams, elaboration of beta-lactamases and reduced permeability across the outer membrane. The mechanisms of resistance in S. dysenteriae have not been studied in depth. This report describes a laboratory mutant, M19 which was characterized by the appearance of two high molecular mass PBPs of 84 (PBP1') and 82 kDa (PBP1"). M19 was more resistant to cefsulodin and cefoxitin. Resistance could be correlated with lower second order rate constants (k+2/K) of acylation. Moreover there was an overall two-fold increase in the relative amount of PBP1 (i.e. 1' + 1") in the mutant M19 compared to C152. This is the first report which presents evidence of the involvement of altered high molecular mass PBPs in beta-lactam resistance in S. dysenteriae.

Involvement of an efflux system in high-level fluoroquinolone resistance of Shigella dysenteriae

Shigella dysenteriae represent one of the growing list of antibiotic-resistant bacteria. Quinolones are widely employed to treat shigellosis. However, quinolone resistance has already been reported, necessitating an understanding of the mechanisms of development of resistance. We demonstrate that high-level fluoroquinolone resistance of S. dysenteriae exposed to these antibiotics may occur in the absence of gyrA mutations and involve a proton motive force(pmf)-dependent efflux system.