Transferable antibiotic resistance in Escherichia coli isolated from healthy Nigerian school children

High prevalence of antibiotic resistance in commensal Escherichia coli from healthy human sources in community settings

Antibiotic resistance is a global health crisis that requires urgent action to stop its spread. To counteract the spread of antibiotic resistance, we must improve our understanding of the origin and spread of resistant bacteria in both community and healthcare settings. Unfortunately, little attention is being given to contain the spread of antibiotic resistance in community settings (i.e., locations outside of a hospital inpatient, acute care setting, or a hospital clinic setting), despite some studies have consistently reported a high prevalence of antibiotic resistance in the community settings. This study aimed to investigate the prevalence of antibiotic resistance in commensal Escherichia coli isolates from healthy humans in community settings in LMICs. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we synthesized studies conducted from 1989 to May 2020. A total of 9363 articles were obtained from the search and prevalence data were extracted from 33 articles and pooled together. This gave a pooled prevalence of antibiotic resistance (top ten antibiotics commonly prescribed in LMICs) in commensal E. coli isolates from human sources in community settings in LMICs of: ampicillin (72% of 13,531 isolates, 95% CI: 65-79), cefotaxime (27% of 6700 isolates, 95% CI: 12-44), chloramphenicol (45% of 7012 isolates, 95% CI: 35-53), ciprofloxacin (17% of 10,618 isolates, 95% CI: 11-25), co-trimoxazole (63% of 10,561 isolates, 95% CI: 52-73), nalidixic acid (30% of 9819 isolates, 95% CI: 21-40), oxytetracycline (78% of 1451 isolates, 95% CI: 65-88), streptomycin (58% of 3831 isolates, 95% CI: 44-72), tetracycline (67% of 11,847 isolates, 95% CI: 59-74), and trimethoprim (67% of 3265 isolates, 95% CI: 59-75). Here, we provided an appraisal of the evidence of the high prevalence of antibiotic resistance by commensal E. coli in community settings in LMICs. Our findings will have important ramifications for public health policy design to contain the spread of antibiotic resistance in community settings. Indeed, commensal E. coli is the main reservoir for spreading antibiotic resistance to other pathogenic enteric bacteria via mobile genetic elements.

Prevalence of multidrug-, extensive drug-, and pandrug-resistant commensal Escherichia coli isolated from healthy humans in community settings in low- and middle-income countries: a systematic review and meta-analysis

BACKGROUND

The majority of existing studies aimed at investigating the incidence and prevalence of multidrug-resistance by bacteria have been performed in healthcare settings. Relatively few studies have been conducted in community settings, but these have consistently shown a high prevalence of multidrug-resistant bacteria in low- and middle-income countries (LMICs).

OBJECTIVES

To provide an appraisal of the evidence on the high prevalence of multidrug-, extensive drug-, and pandrug-resistance in commensal Escherichia coli isolates from human sources in community settings in LMICs.

METHODS

Using the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines, PubMed, EMBASE, MEDLINE, Web of Science, CINAHL, and Cochrane Library databases were systematically searched with the search string: 'Enterobacteriaceae', OR 'E. coli', OR 'Escherichia coli', AND 'antibiotic resistance', OR 'antimicrobial resistance', OR 'drug-resistance', AND 'prevalence', OR 'incidence', OR 'morbidity', OR 'odds ratio', OR 'risk ratio', OR 'confidence interval', OR 'p-value', OR 'rate'. Data were extracted and proportional meta-analysis was performed using the Freeman-Tukey transformation random effect model.

RESULTS

The prevalence of multidrug-, extensive drug- and pandrug-resistance were extracted from articles that met our inclusion criteria and pooled together after a systematic screening of 9,369 items. The prevalence of multidrug-resistance was 28% of 14,336 total cases of isolates tested, 95% CI: 23-32. Extensive drug-resistance was 24% of 8,686 total cases of isolates tested, 95% CI: 14-36. Lastly, pandrug-resistance was 5% of 5,670 total cases of isolates tested, 95% CI: 3-8.

CONCLUSION

This paper provides an appraisal of the evidence on the high prevalence of multidrug-, extensive drug- and pandrug-resistance by commensal E. coli in community settings in LMICs. Our results call for greater effort to be placed at the community level in the design of new and improved public health policies to counter the global threat of antibiotic-resistant infections and bacteria.

Regional dissemination of a trimethoprim-resistance gene cassette via a successful transposable element

Background

Antimicrobial resistance is a growing international problem. We observed a 50% increase in the prevalence of trimethoprim resistance among fecal Escherichia coli from healthy Nigerian students between 1998 and 2005, a trend to increase that continued in 2009.

Methods and Findings

A PCR-based screen revealed that 131 (43.1%) of isolates obtained in Nigeria in 2005 and 2009 carried integron-borne dfrA cassettes. In the case of 67 (51.1%) of these isolates, the cassette was a class 1-integron-borne dfrA7 gene, which has been reported at high prevalence from E. coli isolates from other parts of Africa. Complete sequencing of a 27 Kb dfrA7-bearing plasmid from one isolate located the dfrA7 gene within a Tn21-type transposon. The transposon also contained an IS26-derived bla/sul/str element, encoding resistance to β-lactams, sulphonamides and streptomycin, and mercury resistance genes. Although the plasmid backbone was only found in 12 (5.8%) of trimethoprim-resistant isolates, dfrA7 and other transposon-borne genes were detected in 14 (16.3%) and 32 (26.3%) of trimethoprim resistant isolates collected in Nigeria in 2005 and 2009, respectively. Additionally, 37 (19.3%) of trimethoprim-resistant E. coli isolates collected between 2006 and 2008 from Ghana were positive for the dfrA7 and a transposon marker, but only 4 (2.1%) harbored the plasmid backbone.

Conclusions

Our data point to transposition as a principal mechanism for disseminating dfrA7 among E. coli from Nigeria and Ghana. On-going intensive use of the affordable broad-spectrum antibacterials is likely to promote selective success of a highly prevalent transposable element in West Africa.

Rapid evolution of fluoroquinolone-resistant Escherichia coli in Nigeria is temporally associated with fluoroquinolone use

Background

Antibiotic resistance has necessitated fluoroquinolone use but little is known about the selective forces and resistance trajectory in malaria-endemic settings, where selection from the antimalarial chloroquine for fluoroquinolone-resistant bacteria has been proposed.

Methods

Antimicrobial resistance was studied in fecal Escherichia coli isolates in a Nigerian community. Quinolone-resistance determining regions of gyrA and parC were sequenced in nalidixic acid resistant strains and horizontally-transmitted quinolone-resistance genes were sought by PCR. Antimicrobial prescription practices were compared with antimicrobial resistance rates over a period spanning three decades.

Results

Before 2005, quinolone resistance was limited to low-level nalixidic acid resistance in fewer than 4% of E. coli isolates. In 2005, the proportion of isolates demonstrating low-level quinolone resistance due to elevated efflux increased and high-level quinolone resistance and resistance to the fluoroquinolones appeared. Fluoroquinolone resistance was attributable to single nucleotide polymorphisms in quinolone target genes gyrA and/or parC. By 2009, 35 (34.5%) of isolates were quinolone non-susceptible with nine carrying gyrA and parC SNPs and six bearing identical qnrS1 alleles. The antimalarial chloroquine was heavily used throughout the entire period but E. coli with quinolone-specific resistance mechanisms were only detected in the final half decade, immediately following the introduction of the fluoroquinolone antibacterial ciprofloxacin.

Conclusions

Fluoroquinolones, and not chloroquine, appear to be the selective force for fluoroquinolone-resistant fecal E. coli in this setting. Rapid evolution to resistance following fluoroquinolone introduction points the need to implement resistant containment strategies when new antibacterials are introduced into resource-poor settings with high infectious disease burdens.

Dissemination of antibiotic-resistant bacteria across geographic borders

The development of antibiotic-resistant (AR) bacteria in any country is of global importance. After their initial selection and local dissemination, AR bacteria can be transferred across international borders by human travelers, animal and insect vectors, agricultural products, and surface water. The sources and routes of importation of strains of AR bacteria are most often unknown or undetected, because many bacteria carrying resistance genes do not cause disease, and routine surveillance often does not detect them. Control of international dissemination of AR bacteria depends on methods to reduce selection pressure for the development of such bacteria and improved surveillance to detect their subsequent spread.