Enhanced resolution of random amplified polymorphic DNA genotyping of Pseudomonas aeruginosa

High Rates of Extensively Drug-Resistant Pseudomonas aeruginosa in Children with Cystic Fibrosis

Pseudomonas aeruginosa has a high adaptive capacity, favoring the selection of antibiotic-resistant strains, which are currently considered a global health problem. The purpose of this work was to investigate the rate and distribution of extensively drug-resistant (XDR) P. aeruginosa in pediatric patients with cystic fibrosis (CF) with recurrent infections and to distinguish the current efficacy of antibiotics commonly used in eradication therapy at a Mexican institute focused on children. A total of 118 P. aeruginosa isolates from 25 children with CF (2015-2019) underwent molecular identification, antimicrobial sensitivity tests, and Random Amplified Polymorphic DNA genotyping (RAPD-PCR). The bacterial isolates were grouped in 84 RAPD profiles, revealing a cross-infection between two sisters, whose resistance profile remained unchanged for more than 2 years. Furthermore, 77.1% (91/118) and 51.7% (61/118) of isolates showed in vitro susceptibility to ceftazidime and amikacin, respectively, antibiotics often used in eradication therapy at our institution. As well, 42.4% (50/118) were categorized as multi-drug resistant (MDR) and 12.7% (15/118) were XDR. Of these resistant isolates, 84.6% (55/65) were identified from patients with recurrent infections. The high frequency of XDR strains in children with CF should be considered a caution mark, as such resistance patterns are more commonly found in adult patients. Additionally, amikacin may soon prove ineffective. Careful use of available antibiotics is crucial before therapeutic possibilities are reduced and "antibiotic resistance crisis" worsens.

Antibiotic resistance and genotyping of gram-negative bacteria causing hospital-acquired infection in patients referred to Children's Medical Center

Background and aim

Hospital-acquired infection (HAI) is a major problem worldwide. Understanding patterns of bacterial etiology and antibiotic susceptibility is vital to combating HAI. Besides, typing of isolates is important to establish the intra-hospital surveillance of resistant clones. In this study, we aimed to evaluate antibiotic resistance and genotyping of a number of gram-negative bacteria (GNB) causing HAI in patients who were referred to Children’s Medical Center.

Methods

During the 6-month period, antimicrobial susceptibility profiles of GNB isolates recovered from patients in Children’s Medical Center were determined. Typing of common GNB was performed by random amplified polymorphic DNA (RAPD) analysis and the results were analyzed by Gelcompar II software.

Results

In total, 142 (1.1%) gram-negative bacterial strains were isolated, among which 59.2% were from males. The most organisms were isolated from blood (63%) followed by wounds (13.7%). The greatest proportion of strains came from intensive care units (51%). Low sensitivity of Acinetobacter baumannii to common antibiotics and high resistance of Enterobacter spp. To cefotaxime (100%) were reported. The most efficient antibiotics for Escherichia coli strains were amikacin (84%) and gentamycin (81%). However, just 12.5% of Serratia marcescens strains were resistant to trimethoprim-sulfamethoxazole. The analysis of RAPD-typing revealed the presence of one clone in A. baumannii and E. coli and two clones in Klebsiella pneumoniae, whereas the trend varied completely in Pseudomonas aeruginosa strains and Enterobacter spp.

Conclusion

The results of this study showed a possibility of an outbreak in the Children’s Medical Center. Since there is a possibility of transmission of an infection from one patient to another, high attention should be paid to the basic methods of preventing infection.

Biofilm formation, antibiotic susceptibility and RAPD genotypes in Pseudomonas aeruginosa clinical strains isolated from single centre intensive care unit patients

The aim of this study was to analyse genotypes, antimicrobial susceptibility patterns and serotypes in Pseudomonas aeruginosa clinical strains, including the clonal dissemination of particular strains throughout various intensive care units in one medical centre. Using random amplified polymorphic DNA (RAPD-PCR) and P. aeruginosa antisera, 22 different genotypes and 8 serotypes were defined among 103 isolates from 48 patients. No direct association between P. aeruginosa strain genotypes and serotypes was observed. RAPD typing in strains with the same serotype revealed different genotypes and, on the contrary, most strains with a different serotype displayed the same amplification pattern. The resulting banding patterns showed a high degree of genetic heterogeneity among all isolates from the patients examined, suggesting a non-clonal relationship between isolates from these patients. A higher degree of antibiotic resistance and stronger biofilm production in common genotypes compared to rare ones and genetic homogeneity of the most resistant strains indicated the role of antibiotic pressure in acquiring resistant and more virulent strains in our hospital. In conclusion, genetic characterisation of P. aeruginosa strains using RAPD method was shown to be more accurate in epidemiological analyses than phenotyping.

Antimicrobial effects of drugs against multidrug-resistant Pseudomonas aeruginosa

We evaluated the effects of antimicrobial drugs on four strains of Pseudomonas aeruginosa that are resistant to eight widely used antipseudomonal drugs (piperacillin, piperacillin-tazobactam, imipenem, meropenem, ceftazidime, aztreonam, amikacin, ciprofloxacin) and colistin. In the killing test, colistin (2 microg/ml) was the most effective, followed by aztreonam (48 microg/ml), piperacillin-tazobactam (192-4 microg/ml), piperacillin (192 microg/ml), and a three drug combination of azetreonam (16 microg/ml), ceftazidime (16 microg/ml), and amikacin (4 microg/ml). Six hours after drug addition, colistin (2 microg/ml), aztreonam (48 microg/ml), piperacillin-tazobactam (192-4 microg/ml), piperacillin (192 microg/ml), and the above three drug combination had bacteriostatic effects on all four strains. Colistin, three time breakpoint of aztreonam, piperacillin, or piperacillin-tazobactam, and the three drug combination of aztreonam, ceftazidime, and amikacin were effective in vitro.