DNA Gyrase and Topoisomerase IV Mutations and their effect on Quinolones Resistant Proteus mirabilis among UTIs Patients

Multidrug Resistance Profiles and Resistance Mechanisms to β-Lactams and Fluoroquinolones in Bacterial Isolates from Hospital Wastewater in Bangladesh

Multidrug resistance (MDR) is one of the deadliest public health concerns of the 21st century, rendering many powerful antibiotics ineffective. The current study provides important insights into the prevalence and mechanisms of antibiotic resistance in hospital wastewater isolates. In this study, we determined the MDR profile of 68 bacterial isolates collected from five different hospitals in Dhaka, Bangladesh. Of them, 48 bacterial isolates were identified as Enterobacteriaceae. Additionally, we investigated the prevalence and distribution of five beta-lactam resistance genes, as well as quinolone resistance mechanisms among the isolates. The results of this study showed that 87% of the wastewater isolates were resistant to at least three different antibiotic classes, as revealed using the disc diffusion method. Resistance to β-lactams was the most common, with 88.24% of the isolates being resistant, closely followed by macrolides (80.88% resistant). Polymyxin was found to be the most effective against wastewater isolates, with 29.41% resistant isolates. The most common β-lactam resistance genes found in wastewater isolates were blaTEM (76.09%), blaCTX-M1 (71.74%), and blaNDM (67.39%). Two missense mutations in the quinolone resistance-determining region (QRDR) of gyrA (S83L and D87N) and one in both parC (S80I) and parE (S458A) were identified in all isolates, and one in parE (I529L), which had not previously been identified in Bangladesh. These findings suggest that hospital wastewater acts as an important reservoir of antibiotic-resistant bacteria wherein resistance mechanisms to β-lactams and fluoroquinolones are obvious. Our data also emphasize the need for establishing a nationwide surveillance system for antibiotic resistance monitoring to ensure that hospitals sanitize their wastewater before disposal, and regulation to ensure hospital wastewater is kept away from community settings.

Antibiotic Resistance in Proteus mirabilis: Mechanism, Status, and Public Health Significance

Proteus mirabilis is a specific opportunistic pathogen of many infections including urinary tract infections (UTIs). Risk factors are linked with the acquisition of multidrug-resistant (MDR) to 3 or more classes of antimicrobials) strains. The resistance in extended-spectrum alpha-lactamase is rare, but the rising resistance in extended-spectrum beta-lactamase (ESBL) producing strains is a matter of concern. β-lactamases and antibiotic modifying enzymes mainly constitute the ESBLs resistance mechanism by hydrolyzing the antibiotics. Mutation or Porin loss could lead to the reduced permeability of antibiotics, enhanced efflux pump activity hindering the antibiotic access to the target site, antibiotic failure to bind at the target site because of the target modification, and lipopolysaccharide mutation causing the resistance against polymyxin antibiotics. This review aimed to explore various antimicrobial resistance mechanisms in Proteus mirabilis and their impact on public health status.

Evaluation of biological activities of quinone-4-oxoquinoline derivatives against pathogens of clinical importance

BACKGROUND

Microbial resistance has become a worldwide public health problem, and may lead to morbidity and mortality in affected patients.

OBJECTIVE

Therefore, this work aimed to evaluate the antibacterial activity of quinone-4-oxoquinoline derivatives.

METHOD

These derivatives were evaluated against Gram-positive and Gram-negative bacteria by their antibacterial activity, anti-biofilm, and hemolytic activities and by in silico assays.

RESULTS

The quinone-4-oxoquinoline derivatives presented broad-spectrum antibacterial activities, and in some cases were more active than commercially available reference drugs. These compounds also inhibited bacterial adhesion and the assays revealed seven non-hemolytic derivatives. The derivatives seem to cause damage to the bacterial cell membrane and those containing the carboxyl group at the C-3 position of the 4-quinolonic nucleus were more active than those containing a carboxyethyl group.

CONCLUSION

The isoquinoline-5,8-dione nucleus also favored antimicrobial activity. The study showed that the target of the derivatives must be a non-conventional hydrophobic allosteric binding pocket on the DNA gyrase enzyme.

Impact of target site mutations and plasmid associated resistance genes acquisition on resistance of Acinetobacter baumannii to fluoroquinolones

Among bacterial species implicated in hospital-acquired infections are the emerging Pan-Drug Resistant (PDR) and Extensively Drug-Resistant (XDR) Acinetobacter (A.) baumannii strains as they are difficult to eradicate. From 1600 clinical specimens, only 100 A. baumannii isolates could be recovered. A high prevalence of ≥ 78% resistant isolates was recorded for the recovered isolates against a total of 19 tested antimicrobial agents. These isolates could be divided into 12 profiles according to the number of antimicrobial agents to which they were resistant. The isolates were assorted as XDR (68; 68%), Multi-Drug Resistant (MDR: 30; 30%), and PDR (2; 2%). Genotypically, the isolates showed three major clusters with similarities ranging from 10.5 to 97.8% as revealed by ERIC-PCR technique. As a resistance mechanism to fluoroquinolones (FQs), target site mutation analyses in gyrA and parC genes amplified from twelve selected A. baumannii isolates and subjected to sequencing showed 12 profiles. The selected isolates included two CIP-susceptible ones, these showed the wild-type profile of being have no mutations. For the ten selected CIP-resistant isolates, 9 of them (9/10; 90%) had 1 gyrA/1 parC mutations (Ser 81 → Leu mutation for gyrA gene and Ser 84 → Leu mutation for parC gene). The remaining CIP-resistant isolate (1/10; 10%) had 0 gyrA/1 parC mutation (Ser 84 → Leu mutation for parC gene). Detection of plasmid-associated resistance genes revealed that the 86 ciprofloxacin-resistant isolates carry qnrA (66.27%; 57/86), qnrS (70.93%; 61/86), aac (6')-Ib-cr (52.32%; 45/86), oqxA (73.25%; 63/86) and oqxB (39.53%; 34/86), while qepA and qnrB were undetected in these isolates. Different isolates were selected from profiles 1, 2, and 3 and qnrS, acc(6,)-ib-cr, oqxA, and oqxB genes harbored by these isolates were amplified and sequenced. The BLAST results revealed that the oqxA and oqxB sequences were not identified previously in A. baumannii but they were identified in Klebsiella aerogenes strain NCTC9793 and Klebsiella pneumoniae, respectively. On the other hand, the sequence of qnrS, and acc(6,)-ib-cr showed homology to those of A. baumannii. MDR, XDR, and PDR A. baumannii isolates are becoming prevalent in certain hospitals. Chromosomal mutations in the sequences of GyrA and ParC encoding genes and acquisition of PAFQR encoding genes (up to five genes per isolate) are demonstrated to be resistance mechanisms exhibited by fluoroquinolones resistant A. baumannii isolates. It is advisable to monitor the antimicrobial resistance profiles of pathogens causing nosocomial infections and properly apply and update antibiotic stewardship in hospitals and outpatients to control infectious diseases and prevent development of the microbial resistance to antimicrobial agents.