Access Microbiology - Current Issue

Antimicrobial resistance (AMR) increasingly compromises food safety and public health worldwide. Poultry products are major vectors for AMR bacteria in the food supply. We conducted the first preliminary survey of non-typhoidal Salmonella (NTS) and Escherichia coli on imported poultry in the Maldives. A total of 30 frozen whole chicken samples (15 processed as whole and 15 separated into meat and skin) and 3 pooled egg samples (10 eggs per pool) were obtained from supermarkets and grocery stores in Greater Malé between June 2022 and July 2022. Standard culture methods (Food and Drug Administration Bacteriological Analytical Manual) were used to isolate NTS and E. coli, and isolates were tested for susceptibility to five antibiotics (ampicillin, ceftriaxone, ciprofloxacin, tetracycline and trimethoprim-sulphamethoxazole) by disc diffusion [European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines]. NTS was recovered from 10 of 30 (33.3%) chicken samples, predominantly from skin (9/15) versus meat (3/15); E. coli was found in 15 of 30 (50%) samples, more often in meat. One pooled egg sample (33%) was positive for E. coli. Among 13 NTS isolates, 69% (9/13) were resistant to tetracycline, and 38% (5/13) to ciprofloxacin, ampicillin and ceftriaxone. Thirty-eight per cent (5/13) of NTS were classified by EUCAST as susceptible, increased exposure to ciprofloxacin. Overall, 9 of 13 (69.2%) NTS isolates were multidrug-resistant (MDR; non-susceptible to ≥3 classes). In E. coli, resistance was most common to ampicillin (8/19; 42.1%), followed by tetracycline (5/19; 26.3%), trimethoprim-sulphamethoxazole (4/19; 21.1%), ciprofloxacin (1/19; 5.3%) and ceftriaxone (1/19; 5.3%), with 26.3% (5/19) of E. coli being MDR. These results indicate a substantial prevalence of MDR foodborne bacteria in imported poultry and underscore critical food safety and One Health concerns. Strengthened microbiological surveillance, risk-based import inspection and enhanced regulatory coordination (aligned with the Maldives’ AMR Action Plan) are urgently needed to protect public health.

Background. Extended-spectrum β-lactamase (ESBL)-producing bacteria pose a global challenge because of resistance developing against a wide range of antimicrobial agents, complicating available treatment options. Thus, identifying the prevalent bacterial species producing ESBL enzymes and understanding how they are susceptible to antibiotics is necessary to inform effective treatment guidelines.

Objective. We sought to characterize ESBL-producing bacteria isolated from pregnant women’s urine at Itojo Hospital, Ntungamo district, Southwestern Uganda.

Methods. We conducted a cross-sectional study where we collected and analysed 340 urine samples from 340 pregnant women. We did antimicrobial susceptibility testing using the Kirby–Bauer disc diffusion method. Isolates were screened for ESBL production and confirmed using the combination disc test. Genotypic characterization was confirmed using multiplex PCR to detect blaTEM, blaCTX-M and blaSHV genes.

Results. The prevalence of ESBL-producing bacteria was 29.7% (101/340). Escherichia coli 36/101 (35.6%) and Klebsiella species 33/101 (32.7%) were predominant ESBL producers. Genotypic analysis revealed blaTEM 50/101 (49.5%) and blaCTX-M 31/101 (30.7%) as the most prevalent genes, while blaSHV was less common, 8/101 (7.9%)

Conclusion. The high prevalence of ESBL-producing bacteria and their resistance to commonly used antibiotics highlighted the need for targeted antibiotic therapy, antimicrobial stewardship and regular molecular surveillance.

Background. The increasing prevalence of tigecycline and carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a serious challenge, especially in resource-limited settings. Its ability to exchange resistance genes with other bacteria accelerates the spread of multidrug resistance. While carbapenems and tetracyclines have been used effectively against K. pneumoniae, resistance to these agents is now rising globally, narrowing available treatment options.

Objective. The study aimed to determine the phenotypic and genotypic prevalence of carbapenem and tetracycline resistance in K. pneumoniae isolates along with the transferability pattern of carbapenem and tetracycline resistance genes in these isolates.

Methodology. Clinical isolates from pus and respiratory samples were identified using biochemical tests and MALDI-TOF MS. Antimicrobial susceptibility test was performed by the Kirby–Bauer disc diffusion method, and MICs were determined by the broth microdilution test method. PCR was performed to detect carbapenemase (bla NDM, bla OXA-48 and bla KPC) and tetracycline resistance genes [tet(A), tet(B), tet(K), tet(M) and tet(S)], followed by Sanger sequencing for validation. Conjugation assays assessed gene transferability.

Results. Out of 152 CRKP isolates, 20.4% (31 out of 152) were found to be resistant to tigecycline. All tigecycline-resistant isolates exhibited complete resistance (31 out of 31; 100%) to ceftazidime, ciprofloxacin and omadacycline. Additionally, resistance to amikacin and cefoperazone-sulbactam was observed in 87.1% (27 out of 31) and 77.4% (24 out of 31) of the isolates. Resistance to minocycline and colistin was detected in 51.6% (16 out of 31) and 29.0% (9 out of 31) of the isolates, respectively.

PCR analysis revealed that 51.6% (16 out of 31) of the isolates carried the bla OXA-48 gene, and 29.0% (9 out of 31) carried the bla NDM gene. None of the isolates harboured the bla KPC gene. With respect to tetracycline resistance determinants, the tet(A) gene was detected in 12.9% (4 out of 31) of the isolates, and the tet(B) gene in 3.2% (1 out of 31), while tet(K), tet(M), tet(S) and bla KPC were not detected in any isolate.

Conjugation assays demonstrated that plasmids carrying bla NDM and bla OXA-48 were transferable to a recipient strain, indicating their potential for horizontal gene transfer. In contrast, plasmids harbouring tet(A) and tet(B) genes were not transferable under the experimental conditions.

Conclusion. Tigecycline-resistant K. pneumoniae isolates showed high multidrug resistance, with transferable bla NDM and bla OXA-48 genes. In contrast, chromosome and plasmid-borne tetracycline resistance genes tet(A) and tet(B) were non-transferable, indicating limited horizontal spread.