Reemergence of Chloramphenicol Sensitivity in Enteric Fever

Comprehensive Analysis of Salmonella Species Antibiogram and Evolving Patterns in Empirical Therapy: Insights From Tertiary Care Hospitals in Peshawar, Pakistan

Background Typhoid fever presents a significant challenge in developing nations, exacerbated by the emergence of antibiotic-resistant strains due to widespread prevalence and overuse of antibiotics. This study seeks to assess the antibiogram profiles of Salmonella species isolated from blood cultures of patients hospitalized at two prominent tertiary care hospitals in Peshawar, Pakistan: Khyber Teaching Hospital (KTH) and Hayatabad Medical Complex (HMC). By examining these profiles, the research aims to provide valuable insights into the evolving landscape of antibiotic resistance in the context of typhoid fever management. Materials and Methods This retrospective cross-sectional study utilized data gathered from two hospitals in Peshawar, KTH and HMC. Cases of enteric fever were identified based on positive blood cultures for Salmonella species. The study encompasses demographic information, seasonal prevalence, and antibiogram profiles of 3,137 cases that were presented between 2017 and 2023. Results Among the total 3,137 cases, males accounted for the majority, comprising 63% (2,044 cases). Particularly notable was the clustering of cases among children and adolescents aged one to 24 years. The incidence peaked during the months of summer and spring, from April to September. In terms of Salmonella Typhi isolates, considerable resistance was noted against first-line antibiotics such as amoxicillin/clavulanate (80.1%), co-trimoxazole/trimethoprim-sulfamethoxazole (66.6%), and chloramphenicol (86.9%), as well as against ceftriaxone (79.7%) and ciprofloxacin (51.6%). Conversely, certain antibiotics displayed higher sensitivity patterns, including meropenem (97.8%), doripenem (99.5%), imipenem (97.7%), ertapenem (96.5%), polymyxin B (99.4%), colistin (98.1%), and tigecycline (97.3%). Despite a limited sample size of 214 specimens, fosfomycin demonstrated a remarkable sensitivity of 93.4%. Sensitivities of amikacin and gentamicin were 90.7% and 81.5%, respectively. However, the sensitivity of azithromycin was concerning, standing at 66.5%. The antibiogram pattern for Salmonella exhibited significant and drastic changes. Conclusion In conclusion, this study sheds light on a higher prevalence of typhoid fever among males, with a notable seasonal peak observed during the summer and spring months. The age group most affected spans from one to 24 years. Salmonella isolates displayed significant resistance to conventional first-line antibiotics, alongside ciprofloxacin and third-generation cephalosporins. Azithromycin exhibited lower sensitivity compared to amikacin, gentamicin, and fosfomycin. The research advocates for the empirical use of amikacin, gentamicin, fosfomycin, and meropenem in the treatment of typhoid fever in Pakistan. Urgent measures, including regular Salmonella antibiogram surveillance, antibiotic stewardship, public health education, and Salmonella vaccination programs, are deemed crucial for primary disease prevention.

A paradox of bacterial persistence and antibiotic resistance: chloramphenicol acetyl transferase as a double barrel shot gun

The problematic microbial resistance to antibiotics has led to an increasing interest in bacterial persistence and its impact on infection. Nonetheless, these two mechanisms are often assessed in independent studies, and there is a lack of knowledge about their relation or possible interactions, both at cellular and population levels. This work shows evidence that the insertion of the resistance gene Chloramphenicol Acetyl Transferase (cat) together with its cognate antibiotic chloramphenicol (CAM), is capable to modulate Salmonella Typhimurium persistence to several antibiotics and decrease its survival. This effect is independent of the antibiotics' mechanisms of action or the locus of cat. RelA [p(ppGpp) syntetase] has been shown to be involved in persistence. It was recently proposed that RelA [(p)ppGpp synthetase], binds to uncharged tRNAs, forming RelA.tRNA complexes. These complexes bind to vacant A-sites in the ribosome, and this mechanism is essential for the activation of RelA. In this study, we propose that the antibiotic chloramphenicol blocks the A-site of the ribosome, hindering the binding of RelA.tRNA complexes to the ribosome thus preventing the activation of RelA and (p)ppGpp synthesis, with a consequent decrease in the level of persistence of the population. Our discovery that the concomitant use of chloramphenicol and other antibiotics in chloramphenicol resistant bacteria can decrease the persister levels can be the basis of novel therapeutics aiming to decrease the persisters and recalcitrant infections.

Plasmid Composition, Antimicrobial Resistance and Virulence Genes Profiles of Ciprofloxacin- and Third-Generation Cephalosporin-Resistant Foodborne Salmonella enterica Isolates from Russia

Salmonella enterica is an important foodborne pathogen worldwide. Ciprofloxacin and extended-spectrum cephalosporins are the common first-line antimicrobial drugs for the treatment of salmonellosis, antimicrobial resistance genes for which are mostly transferred via plasmids. The goal of this work was to perform genomic analysis of plasmids from foodborne S. enterica isolates obtained in Russia based on whole-genome sequencing. In the current study, 11 multidrug-resistant samples isolated in 2021 from 8 regions of Russia were selected based on their resistance to ciprofloxacin and third-generation cephalosporins (CIP-3rd). Whole-genome short-read sequencing (WGS) was performed for all isolates; the samples belonged to five different sequence types (ST32, ST469, ST11, ST142, and ST548) which had different profiles of antimicrobial resistance (AMR) and virulence genes. We have performed additional long-read sequencing of four representative S. enterica isolates, which showed that they carried pESI-like megaplasmids of 202-280 kb length harboring extended-spectrum β-lactamase genes, fluoroquinolone, tetracycline, and aminoglycosides resistance genes, as well as several virulence determinants. We believe that the WGS data obtained will greatly facilitate further studies of foodborne S. enterica isolates epidemiology in terms of their self-transmissible plasmid composition that mediated antimicrobial resistance and virulence determinants conferring selective advantages of this important bacterial pathogen.

Antimicrobial sensitivity patterns of enteric fever in Pakistan: a comparison of years 2009 and 2019

BACKGROUND

Pakistan is one of the endemic regions for typhoid fever and paratyphoid fever. This study aimed to identify the evolving antimicrobial sensitivity patterns of Salmonella species causing enteric fever and its implications on the clinical prescribing of antimicrobials.

METHODS

This was a retrospective descriptive study conducted at a university hospital. Antimicrobial resistance was defined in terms of non-resistant, multidrug resistant (MDR) and extended drug resistant (XDR) as per WHO guidance. Data were collected from the years 2009 and 2019. Chi squared was applied to test for statistical significance (p < 0.05).

RESULTS

A total of 200 patients (100 from 2009 and 100 from 2019) were included in the study. Non-resistant enteric fever cases reduced from 100% in 2009 to 44% in 2019, whereas the MDR and XDR enteric fever cases increased to 16% and 40%, respectively (p < 0.05). Cross tabulation carried out for individual drugs showed an independent rise in the sensitivities of individual first-line antimicrobials.

CONCLUSION

Antimicrobial resistant enteric fever has become a big challenge for Pakistan. The choice of antibiotic prescription has narrowed down to broader spectrum antimicrobials making it difficult to treat, leading to increased morbidity and mortality.

Antibiotic Susceptibility Patterns of Salmonella Typhi and Salmonella Paratyphi in a Tertiary Care Hospital in Islamabad

Background

Enteric fever is a serious public health problem in Pakistan. Growing problem of drug-resistant Salmonella strains and outbreak of ceftriaxone-resistant Salmonella typhi in Hyderabad during 2016-2017 is concerning. This study aimed to determine the antibiogram profile of Salmonella typhi and Salmonella paratyphi isolated from blood cultures of patients presenting in Pakistan Institute of Medical Sciences (PIMS), Islamabad.

Materials and methods

A retrospective cross-sectional study conducted in PIMS. A case of enteric fever was defined as a patient with blood culture positive for either S. typhi or S. paratyphi. Demographics and antibiogram profile of the 664 cases who presented during 2012-2018 were included in this study.

Results

Out of 664 cases, S. typhi was isolated from 528 and S. paratyphi was isolated from 136 cases. Males accounted for the majority of the cases (n = 440, 66.3%). Clustering of the cases was observed in young adults (18-25 years). Incidence was highest during months of summer and monsoon (May-September). Most of the S. typhi isolates were resistant to the first-line antibiotics (amoxicillin 57.6%, co-trimoxazole 61.4%, chloramphenicol 46.9%) and ciprofloxacin (62.7%). Antibiotic resistance rates were lowest for imipenem (3.8%) and ceftriaxone (4.4%). Among S. typhi isolates tested for all first-line antibiotics, 44.6% (149/334) were multidrug-resistant (MDR). In contrast, only 12.2% (11/90) of the S. paratyphi isolates were MDR. 0.7% (2/283) of the tested S. typhi isolates were extensively drug-resistant (XDR). XDR strains were sensitive to imipenem. There was an overall reduction in first-line antibiotic resistance rates from 2012 to 2018.

Conclusion

S. typhi accounted for the majority of the cases of enteric fever. Most S. typhi isolates were resistant to first-line antibiotics. S. paratyphi exhibited lower antibiotic resistance rates. This study recommends third-generation cephalosporins for empirical therapy and for treatment of MDR cases of enteric fever. Imipenem should be reserved for the treatment of XDR Salmonella cases. A decreasing trend in first-line antibiotic resistance rates over time is promising. Antibiotic stewardship is the need of the hour. 

Sensitivity Pattern Of Salmonella typhi And Paratyphi A Isolates To Chloramphenicol And Other Anti-Typhoid Drugs: An In Vitro Study

Purpose

To investigate the antimicrobial sensitivity pattern of commonly prescribed antimicrobials (chloramphenicol, cefixime, ofloxacin, azithromycin, and ceftriaxone) against Salmonella enterica isolates.

Methods

Blood culture positive isolates of S. typhi and S. paratyphi A (N = 251) received at Metropolis Healthcare Limited (Mumbai, India) from four zones of India (North, South, West, and East) between April and August 2018 were tested for antimicrobial susceptibility by E-test method. Based on the minimum inhibitory concentration (MIC), the organism was categorized as sensitive, intermediate, and resistant against the respective antibiotics as per Clinical and Laboratory Standards Institute criteria 2018.

Results

Out of 251 Salmonella isolates, 192 (76.5%) were S. typhi and 59 (23.5%) were S. paratyphi A. All 251 (100%) Salmonella isolates were sensitive to cefixime, ceftriaxone, and azithromycin; 237/251 (94.4%) isolates to chloramphenicol and only 9/251 (3.6%) isolates were sensitive to ofloxacin. Based on average MIC and MIC breakpoints, Salmonella isolates were found to be sensitive to chloramphenicol (MIC: 3.89±6.94 µg/mL), cefixime (MIC: 0.13±0.11 µg/mL), azithromycin (MIC: 3.32±2.19 µg/mL), and ceftriaxone (MIC: 0.11±0.18 µg/mL) and resistant to ofloxacin (MIC: 2.95±6.06 µg/mL). More than 20% of Salmonella isolates had MICs of chloramphenicol as 1.5 µg/mL (27.85% isolates) and 2 µg/mL (29.53% isolates).

Conclusion

Our study confirms the re‑emergence of susceptibility of Salmonella isolates to chloramphenicol. Further, the concern about fluoroquinolone-decreased susceptibility as indicated by the intermediate susceptibility or resistance was reiterated in this study. Though cefixime, azithromycin, and ceftriaxone showed susceptibility, the possibility of antibiotic resistance with the irrational use of these antibiotics cannot be deterred. This study thus emphasizes the need for continuous evaluation and judicious use of antimicrobials, considering the ever-changing landscape.

The Use of Ceftriaxone Compared to Chloramphenicol in Typhoid Fever Treatment: an Evidence Based Case Report

Typhoid fever is a disease caused by the gram-negative bacterium Salmonella typhi. Since its introduction in 1949, chloramphenicol for decades become a first-line treatment of typhoid fever. Until now, chloramphenicol is still the first line treatment of typhoid fever in rural areas in Indonesia, especially due to its low cost. However, in addition to the problem of bacterial resistance, chloramphenicol is known to cause side effect such as bone marrow suppression. Right now many other antibiotics are used as regimens for treatment of typhoid fever, one of which is ceftriaxone. This report is created to answer the clinical question whether ceftriaxone is more effective compared to chloramphenicol as first-line treatment of typhoid fever. Structured search was performed on PubMed, EBSCO, and ScienceDirect and after a screening process and appraisal using criteria from Center of Evidence Based Medicine at Oxford University, three articles were selected. Two of the three articles demonstrate higher effectiveness of chloramphenicol in term of defervescence rate (P = 0.35 and P > 0.05). On the other hand, the third article shows higher effectiveness of ceftriaxone in term of defervescence rate (P = 0.0001). The conclusion drawn is that ceftriaxone showed better effectiveness in the treatment of typhoid fever compared to chloramphenicol.

Prevalence and detection of antibiotic-resistant determinant in Salmonella isolated from food-producing animals

Salmonella spp. infections are considered as the most common food-borne disease globally. The contamination of food products with Salmonella has given rise to severe health and economic challenges. This study assessed the prevalence of Salmonella in the faeces of cows and goats in the Eastern Cape province of South Africa, their antibiotic resistance patterns as well as antibiotic-resistant gene determinant. Antibiotic disc was used for antibiogram profiles while polymerase chain reaction was employed for the detection of antibiotic-resistant genes. A total of 150 Salmonella were isolated from the faecal samples. Eighty two (55%) isolates were recovered from cow faeces while 68 (45%) were isolated from goat faeces. All Salmonella isolates were sensitive to ciprofloxacin (100%) while 95% were sensitive to ofloxacin. Also, a high sensitivity of 93 and 89% was observed against nalidixic acid and ofloxacin, respectively. Salmonella isolates demonstrated moderate sensitivity against cephalothin (70%), chloramphenicol (75%) and minocycline (68%) while 49% were resistant to tetracycline and erythromycin. The prevalence of the antibiotic-resistant genes in Salmonella isolates were detected as follows: integron conserved segment 28% (42/150), bla TEM gene 19.3% (29/150), blapse₁ 7.3% (11/150) and blaampC 4.7% (7/150). The results obtained in the study imply that cow and goat faeces could be potential reservoirs of Salmonella and could possibly cause infections as a result of contamination of food products. There is a need for a surveillance system to track resistance patterns of Salmonella circulating in South Africa.

Prevalence and antimicrobial resistance of Listeria, Salmonella, and Yersinia species isolates in ducks and geese

The aims of this study were to determine the prevalence and antimicrobial resistance of Listeria, Salmonella, and Yersinia spp. isolated from duck and goose intestinal contents. A total of 471 samples, including 291 duck and 180 goose intestinal contents, were purchased from wet markets between November 2008 and July 2010. Listeria, Salmonella, and Yersinia spp. were isolated from 58 (12.3%), 107 (22.7%), and 80 (17%) of the samples, respectively. It was concluded that Listeria ivanovii, Salmonella Thompson, and Yersinia enterocolitica were the predominant serovars among Listeria, Salmonella, and Yersinia spp., respectively. Moreover, resistance to tetracycline was common in Listeria (48.3%) and Salmonella spp. (63.6%), whereas 51.3% of the Yersinia spp. isolates were resistant to cephalothin. Therefore, continued surveillance of the prevalence of the pathogens and also of emerging antibiotic resistance is needed to render possible the recognition of foods that may represent risks and also ensure the effective treatment of listeriosis, salmonellosis, and yersiniosis.

Resistance pattern of ciprofloxacin against different pathogens

OBJECTIVES

Ciprofloxacin is a broad-spectrum antibiotic widely prescribed in clinical and hospital settings. The emergence of antimicrobial resistance against effective antibiotics is a global issue. The objective of study is the surveillance of ciprofloxacin against common pathogens.

METHODS

To investigate the present status of antimicrobial resistance against ciprofloxacin, five hundred and twenty four clinical isolates of Escherichia coli (30%), Staphylococcus aureus (33%), Salmonella typhi (9%), Klebsiella pneumonia (14%) and Pseudomonas aeruginosa (14%) were collected during study from January, 2008 to February, 2009 from different pathological laboratories running in and out side hospitals located in Karachi, Pakistan. These pathogens were isolated from specimens of both in and out patients. The in-vitro antimicrobial activity of ciprofloxacin was carried out by Disc Diffusion Method (Kirby-Bauer test).

RESULTS

Showed that ciprofloxacin is 27.02%, 21.95%, 16.66%, 72.22% and 44.44% resistant to Escherichia coli, Staphylococcus aureus, Salmonella typhi, Klebsiella pneumonia and Pseudomonas aeruginosa respectively.

CONCLUSION

It is concluded that these clinical isolates have started developing resistance against ciprofloxacin due to its irrational and inappropriate use. Continuous surveillance is crucial to monitor the antimicrobial resistance among pathogens.