Comparative efficacy of chloramphenicol, ampicillin, and co-trimoxazole in the treatment of typhoid fever

The Gathering Storm: Is Untreatable Typhoid Fever on the Way?

Klemm et al. (mBio 9:e00105-18, 2018, https://doi.org/10.1128/mBio.00105-18) present comprehensive antibiotic sensitivity patterns and genomic sequence data on Salmonella enterica serovar Typhi blood culture isolates from typhoid fever cases during an epidemic in Pakistan. Microbiologic and genomic data pinpoint the identities and locations of the antimicrobial resistance genes and the outbreak strain’s lineage. They propose that Salmonella enterica serovar Typhi be added to the list of bacterial pathogens of public health importance that have become extensively drug resistant (XDR). This paper portends possible dire scenarios for typhoid fever control if XDR strains disseminate globally. Since the outbreak strain is of the H58 haplotype, known for its ability to spread worldwide and displace endemic S. Typhi, this concern is well-founded. The report of Klemm et al. forewarns the global community to address control of typhoid fever more aggressively through prevention, should therapeutic options disappear. This Commentary frames the Klemm et al. findings within a historic perspective.

Epidemiology, Clinical Presentation, Laboratory Diagnosis, Antimicrobial Resistance, and Antimicrobial Management of Invasive Salmonella Infections

Salmonella enterica infections are common causes of bloodstream infection in low-resource areas, where they may be difficult to distinguish from other febrile illnesses and may be associated with a high case fatality ratio. Microbiologic culture of blood or bone marrow remains the mainstay of laboratory diagnosis. Antimicrobial resistance has emerged in Salmonella enterica, initially to the traditional first-line drugs chloramphenicol, ampicillin, and trimethoprim-sulfamethoxazole. Decreased fluoroquinolone susceptibility and then fluoroquinolone resistance have developed in association with chromosomal mutations in the quinolone resistance-determining region of genes encoding DNA gyrase and topoisomerase IV and also by plasmid-mediated resistance mechanisms. Resistance to extended-spectrum cephalosporins has occurred more often in nontyphoidal than in typhoidal Salmonella strains. Azithromycin is effective for the management of uncomplicated typhoid fever and may serve as an alternative oral drug in areas where fluoroquinolone resistance is common. In 2013, CLSI lowered the ciprofloxacin susceptibility breakpoints to account for accumulating clinical, microbiologic, and pharmacokinetic-pharmacodynamic data suggesting that revision was needed for contemporary invasive Salmonella infections. Newly established CLSI guidelines for azithromycin and Salmonella enterica serovar Typhi were published in CLSI document M100 in 2015.

Efficacy and safety of chloramphenicol: joining the revival of old antibiotics? Systematic review and meta-analysis of randomized controlled trials

OBJECTIVES

Chloramphenicol is an old broad-spectrum antibiotic. We assessed its efficacy and safety.

METHODS

This was a systematic review and meta-analysis. Electronic databases were searched to identify randomized controlled trials (RCTs) that assessed patients, of any age, with systemic bacterial infections that can cause sepsis and compared chloramphenicol alone versus other antibiotics. No restrictions on the date of publication, language or publication status were applied. The primary outcome assessed was overall mortality.

RESULTS

Sixty-six RCTs fulfilled the inclusion criteria, and these included 9711 patients. We found a higher mortality with chloramphenicol for respiratory tract infections [risk ratio (RR) 1.40, 95% CI 1.00-1.97] and meningitis (RR 1.27, 95% CI 1.00-1.60), both without heterogeneity. The point estimate was similar for enteric fever, without statistical significance. No statistically significant difference was found between chloramphenicol and other antibiotics regarding treatment failure, except for enteric fever (RR 1.46, 95% CI 1.07-2.00, without heterogeneity). This difference derived mainly from studies comparing chloramphenicol with fluoroquinolones (RR 1.85, 95% CI 1.07-3.2). There were no statistically significant differences between chloramphenicol and other antibiotics in terms of adverse events, including haematological events, except for anaemia, which occurred more frequently with chloramphenicol (RR 2.80, 95% CI 1.65-4.75, I(2) =0%), and gastrointestinal side effects, which were less frequent with chloramphenicol (RR 0.67, 95% CI 0.46-0.99, I(2) =0%). Many of the studies included were sponsored by pharmaceutical companies marketing the comparator drug to chloramphenicol, and this might have influenced the results.

CONCLUSIONS

Chloramphenicol cannot be recommended as a first-line treatment for respiratory tract infections, meningitis or enteric fever as alternatives are probably more effective. Chloramphenicol is as safe as treatment alternatives for short antibiotic courses. RCTs are needed to test this treatment against MDR organisms when better alternatives do not exist.

Pharmacokinetics and pharmacodynamics of antimicrobials

Antibiotics are some of our most commonly used drugs. Until recently, little has been known about how to optimize administration of these agents. Unfortunately, the rate of discovery of new antibiotics has been declining, coincident with the explosion in the number of multidrug-resistant organisms in both the community and hospital environments. This development makes the identification of optimal regimens that will result in good clinical and microbiological outcomes important, but it also makes clear the necessity of identifying regimens that will suppress the emergence of resistant organisms. Given that new agents for multidrug-resistant pathogens will take nearly a decade to become available to physicians, keeping organisms susceptible to drugs that are already available is even more critical. Pharmacodynamics allows identification of the drug exposure measure that is closely associated with the ability to kill organisms and, also, to suppress the emergence of resistant subpopulations of organisms. Use of Monte Carlo simulation allows identification of drug doses in the clinical arena to accomplish these ends. Such approaches should be applied to all old and new antibacterial agents.

Fluoroquinolones in the treatment of typhoid fever and the carrier state

Typhoid fever remains an important public health problem throughout the world with a higher morbidity and mortality rate in the developing countries. Early establishment of the diagnosis and prompt initiation of treatment with chloramphenicol, ampicillin or trimethoprim-sulfamethoxazole is not necessarily followed by complete resolution of the infection. Between 1% and 6% of patients with typhoid fever become chronic biliary carriers of Salmonella typhi. These carriers are potential factors in the continued transmission of the disease. The increasing emergence worldwide of strains showing multiple resistance to the agents traditionally used in therapy has encouraged investigators to seek alternatives such as third generation cephalosporins and recently the new 4-quinolones, which have greater activity against Salmonella typhi including multi-resistant strains. The fluoroquinolones seem to be the treatment of choice in those regions where resistant strains of Salmonella typhi are prevalent.

Typhoid fever in Hong Kong children

Experience with typhoid fever in 111 children over a 5-year period was reviewed. There were 66 boys and 45 girls, ranging in age from 1 to 11.5 years. The symptoms of typhoid fever were quite non-specific. Fever was the most common presenting symptom (in 98.3%). Other common presenting features were diarrhoea (25.7%), constipation (22%), vomiting (21.1%), cough (25%), abdominal pain (27.5%), headache (9.2%), epistaxis, meningism and convulsions. Rose spots were detected in 20% of cases, occurring mainly during the first 2 weeks of illness. Significant Widal reactions were present in 84.7% of cases. Blood and stool cultures were positive in 57% and 44% of cases, respectively. Peripheral blood white cell counts were not found to be of great diagnostic value. Chloramphenicol remained the drug of choice in the treatment of typhoid fever. It was more effective than ampicillin or co-trimoxazole. Complications were uncommon, occurring in only two patients. There were two deaths; both were admitted late and in moribund state. Early diagnosis and treatment is vital in typhoid fever and, as the presenting features are non-specific, a high index of suspicion is required.

Tetracyclines, chloramphenicol, erythromycin, and clindamycin

The tetracyclines are effective in the treatment of Chlamydia, Mycoplasma pneumoniae, and rickettsial infections and may also be used for gonococcal infections in patients unable to tolerate penicillins. These drugs may cause gastrointestinal irritation, photo-toxic dermatitis, diarrhea, vestibular damage, and hepatotoxicity in pregnant women. Chloramphenicol is used primarily for anaerobic infections, Haemophilus influenzae meningitis, and typhoid fever. The most important toxic effect of chloramphenicol is bone marrow suppression, which can be dose related or idiosyncratic. Erythromycin is the drug of choice for the treatment of infections caused by M. pneumoniae, Legionella species, group A beta-hemolytic streptococci, and Streptococcus pneumoniae. The frequency of serious untoward effects associated with the use of erythromycin is low; epigastric distress may occur. Clindamycin is active against Bacteroides fragilis and other anaerobic microorganisms. Pseudomembranous enterocolitis has developed in as many as 10% of patients taking this drug. The use of clindamycin should be discontinued promptly if diarrhea occurs.

Association between specific plasmids and relapse in typhoid fever

We studied isolates from 73 patients hospitalized with typhoid fever in Lima, Peru. Of these 73 patients, 11 (15%) suffered a clinical relapse, with fever and positive blood cultures, within 3 months of their original illness. Using plasmids as epidemiologic markers, we found that three patients who subsequently relapsed were initially infected with more than one strain of Salmonella typhi. There was a highly significant association between relapse and isolation of a strain containing either a 24- or a 38-kilobase plasmid at the time of the original infection; however, we were unable to show any evidence of homology between these two plasmids. Our data indicate that infection with multiple strains is not uncommon in this endemic area and suggest that relapse may be partly strain dependent.

Enteric fever in patients admitted to a diarrhoeal disease hospital in Bangladesh

The hospital records of 62 patients with blood culture-proven enteric fever admitted to the Dacca Hospital of the International Centre for Diarrhoeal Disease Research, Bangladesh, over a one-year period were reviewed. Older children and young adults had the highest age-specific rates of disease. The clinical, epidemiological and laboratory features of patients with enteric fever were compared with similar information from patients in hospital for cholera and shigellosis. Patients with enteric fever had a significantly longer prodrome of illness and were more likely to have fever than patients in the other groups. Our hospital cares primarily for patients with diarrhoeal diseases and while 94% of enteric fever patients had diarrhoea, only 5% had the recognized diarrhoeal pathogens Shigella or Vibrio cholerae identified, compared to 25% of the total hospital in-patient group, suggesting that Salmonella typhi itself may be a cause of diarrhoea. Antibiotic resistance patterns of S. typhi isolates were reviewed, and one isolate was found to be multiply antibiotic resistant. The advent of an effective oral typhoid vaccine makes further work on the epidemiology of enteric fever in endemic areas such as Bangladesh a high priority.