Aminoglycoside cross-resistance patterns of gentamicin-resistant bacteria

Antimicrobial resistance profile of Escherichia coli isolated from poultry litter

Antimicrobial resistance is a threat to animal and human health. As a commensal and zoonotic bacterium, Escherichia coli has the potential to be a pathogenic source of antimicrobial resistance. The purpose of this study aimed to investigate the antimicrobial resistance profile of E. coli isolated from litter collected from pens in a broiler chicken experiment. E. coli was isolated from litter samples (n = 68 isolates) of 16 pens housing broilers to d 53 of age. Resistance to 10 antimicrobials was observed by disc diffusion. The presence of 23 antimicrobial and heavy metal resistance genes, O serogroups, and avian pathogenic E. coli (APEC-like) minimal predictor genes were identified through PCR. E. coli isolates presented the greatest resistance to cephalothin (54.4%), tetracycline (27.9%), streptomycin (29.4%), ampicillin (20.6%), colistin (13.2%), sulphonamides (8.8%), and imipenem (1.5%). Multidrug resistance to at least 3 antimicrobials was observed in 22.1% of isolates. The identified O-types of the E. coli isolates were O15, O75, O78, and O91. There was a greater likelihood that the genes groEL, aph(3)IA, silP, sull, aadA, qacEdelta1, iroN, ompTp, and hlyF were present in isolates that exhibited ampicillin resistance (P ≤ 0.05). There was a greater likelihood that the groEL gene was present in isolates resistant to ampicillin, colistin, tetracycline, sulphonamides, or cephalothin (P ≤ 0.05). Further characterizing E. coli antimicrobial resistance is essential and aids in developing effective solutions, thereby furthering the One Health objective.

The perspective of antibiotic therapeutic challenges of brucellosis in the Middle East and North African (MENA) countries: Current situation and therapeutic management

Brucellosis is among the most prevalent zoonotic infections in Middle Eastern and North African (MENA) countries, critically impacting human and animal health. A comprehensive review of studies on antibiotic susceptibility and therapeutic regimes for brucellosis in ruminants and humans in the MENA region was conducted to evaluate the current therapeutic management in this region. Different scientific databases were searched for peer-reviewed original English articles published from January 1989 to February 2021. Reports from research organizations and health authorities have been taken into consideration. Brucella melitensis and Brucella abortus have been reported from the majority of MENA countries, suggesting a massive prevalence particularly of B. melitensis across these countries. Several sporadic cases of brucellosis relapse, therapeutic failure, and antibiotic resistance of animal and human isolates have been reported from the MENA region. However, several studies proved that brucellae are still in-vitro susceptible to the majority of antibiotic compounds and combinations in current recommended WHO treatment regimens, e.g. levofloxacin, tetracyclines, doxycycline, streptomycin, ciprofloxacin, chloramphenicol, gentamicin, tigecycline, and trimethoprim/sulfamethoxazole. The current review presents an overview on resistance development of brucellae and highlights the current knowledge on effective antibiotics regimens for treating human brucellosis. This article is protected by copyright. All rights reserved.

Antibiotic prescribing and resistance: knowledge level of medical students of clinical years of University Sultan Zainal Abidin, Malaysia

The innovation of penicillin by Dr Alexander Fleming in 1928 and its use in clinical practice saved many lives, especially during the Second World War. Tuberculosis still carries a significant public health threat and has re-emerged over the past two decades, even in modern countries where tuberculosis was thought to be eliminated. The World Health Organization defines antimicrobial resistance as the resistance of a microorganism to an antimicrobial drug that was initially effective for treatment of infections caused by the microbe. Therefore, the findings of the current study will provide data to enable the design of a new educational program to better equip our students in confronting antimicrobial resistance. This study was a cross-sectional, questionnaire-based survey, which was undertaken in the Faculty of Medicine, Universiti Sultan Zainal Abidin, Kuala Terengganu, Malaysia. The study participants were students of the Bachelor of Medicine and Bachelor of Surgery program (MBBS) of Year III, IV, and V. A total of 142 out of 164 (86%) medical students returned the questionnaire. Specifically, the year-wise breakdown of responses was 29% (41), 39% (55), and 32% (45) for Year III, IV, and V, respectively. Among the study respondents, 28% (40) were male, and the remaining 72% (102) were female. In all, 67% of the participants felt more confident in "making an accurate diagnosis of infection/sepsis." The majority (88%) of the study participants stated that they would like more training on antibiotic selection. This research has found that there is a gap between theoretical input and clinical practice; the students are demanding more educational intervention to face the threat of antimicrobial resistance.

Effects of gentamicin on the proteomes of aerobic and oxygen-limited Escherichia coli

The key role of the bacterial ribosome makes it an important target for antibacterial agents. Indeed, a large number of clinically useful antibiotics target this complex translational ribonucleoprotein machinery. Unfortunately, the development of resistant bacterial strains has compromised the effectiveness of most classes of antibacterial agent, including the classes that target the ribosome. Combinations of two or more drugs can be used to help overcome resistance, and in certain circumstances their action may be synergistic. In this study we have used proteomic techniques to establish the effects of gentamicin on the proteomes of aerobic and oxygen-limited Escherichia coli. Ribosomal proteins L1, L9, L10, and S2 were found to be up-regulated in both conditions, and we postulate that these are candidate drug targets for the development of synergistic combinations with gentamicin.

The novel antimicrobial peptide PXL150 in the local treatment of skin and soft tissue infections

Dramatic increase in bacterial resistance towards conventional antibiotics emphasises the importance to identify novel, more potent antimicrobial therapies. Antimicrobial peptides (AMPs) have emerged as a promising new group to be evaluated in therapeutic intervention of infectious diseases. Here we describe a novel AMP, PXL150, which demonstrates in vitro a broad spectrum microbicidal action against both Gram-positive and Gram-negative bacteria, including resistant strains. The potent microbicidal activity and broad antibacterial spectrum of PXL150 were not associated with any hemolytic activity. Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) failed to develop resistance towards PXL150 during continued selection pressure. PXL150 caused a rapid depolarisation of cytoplasmic membrane of S. aureus, and dissipating membrane potential is likely one mechanism for PXL150 to kill its target bacteria. Studies in human cell lines indicated that PXL150 has anti-inflammatory properties, which might be of additional benefit. PXL150 demonstrated pronounced anti-infectious effect in an in vivo model of full thickness wounds infected with MRSA in rats and in an ex vivo model of pig skin infected with S. aureus. Subcutaneous or topical application of the peptide in rats did not lead to any adverse reactions. In conclusion, PXL150 may constitute a new therapeutic alternative for local treatment of infections, and further studies are warranted to evaluate the applicability of this AMP in clinical settings.

Antibiotic production improvement in the rare actinomycete Planobispora rosea by selection of mutants resistant to the Aminoglycosides Streptomycin and Gentamycin and to Rifamycin

During a strain improvement program, spontaneous mutants with single or combined resistance to streptomycin (Str(r)), gentamycin (Gen(r)) or rifamycin (Rif(r)) were selected from the industrial strain of Planobispora rosea, which is the producer of thiazolylpeptide GE2270. Among the mutants resistant to each single antibiotic, higher producers occurred more frequently (60%) among Gen(r) than in Rif(r) (10%) and Str(r) (24%) populations. Two Gen(r) mutants showed up to 1.5-fold improvement in GE2270 production while single resistant mutants Str(r) and Rif(r) produced slightly more than the parental strains. The combination of Str(r) and Rif(r) in the same strain improved GE2270 yield up to 1.7-fold. Finally, a higher GE2270 producing strain (1.8-fold improvement with respect to the parental strain) was selected among those mutants with triple resistance to streptomycin, rifamycin and gentamycin. A hierarchical increase in aerial mycelium and spore formation was observed which paralleled GE2270 production improvement.

An overview of nosocomial infections, including the role of the microbiology laboratory

An estimated 2 million patients develop nosocomial infections in the United States annually. The increasing number of antimicrobial agent-resistant pathogens and high-risk patients in hospitals are challenges to progress in preventing and controlling these infections. While Escherichia coli and Staphylococcus aureus remain the most common pathogens isolated overall from nosocomial infections, coagulase-negative staphylococci (CoNS), organisms previously considered contaminants in most cultures, are now the predominant pathogens in bloodstream infections. The growing number of antimicrobial agent-resistant organisms is troublesome, particularly vancomycin-resistant CoNS and Enterococcus spp. and Pseudomonas aeruginosa resistant to imipenem. The active involvement and cooperation of the microbiology laboratory are important to the infection control program, particularly in surveillance and the use of laboratory services for epidemiologic purposes. Surveillance is used to identify possible infection problems, monitor infection trends, and assess the quality of care in the hospital. It requires high-quality laboratory data that are timely and easily accessible.

Mechanism of aminoglycoside resistance among beta-lactam-resistant Escherichia coli in the United States

We examined aminoglycoside (AG) resistance in ampicillin-resistant Escherichia coli obtained from nine hospitals participating in the National Nosocomial Infections Study. The isolates were tested to 25 antimicrobials using broth microdilution methods. If the organism was intermediate or resistant to gentamicin, tobramycin, netilmicin, or amikacin, we determined the class of aminoglycoside-modifying enzyme (AME) using the phosphocellulose paper binding assay. Of 423 E. coli, 21 (5%) were intermediate or resistant to one or more of the AGs. All but two of these E. coli isolates had at least one AME. Twelve isolates had phosphotransferase (APH) enzymes; seven had adenyltransferase (ANT) enzymes (all ANT[2"]); and four had acetyltransferase (AAC) enzymes. The seven ANT[2"]-producing isolates were more likely to be acquired in the community than in the hospital (4/7 ANT[2"]-producing E. coli versus one of 14 of the other AG-resistant E. coli, p = 0.03, Fisher's exact test). These findings suggest that for E. coli resistant to both ampicillin and an AG, APH enzymes are the predominant AME class. Additionally, isolates with certain AMEs may be acquired both in the community and in the hospital.

Regrowth of aminoglycoside-resistant variants and its possible implication for determination of MICs

Regrowth of aminoglycoside-resistant variants was seen when large inocula of two strains of Escherichia coli were incubated with gentamicin in concentrations well above their MICs (0.5 micrograms/ml). The extent of the selection of resistant variants was proportional to the concentration of gentamicin during incubation; after incubation with gentamicin (greater than or equal to 2 micrograms/ml for 24 h), all bacteria were resistant to at least 8 micrograms/ml. Bacteria resistant to these concentrations always formed small colonies, whereas variants resistant to lower concentrations (1 to 2 micrograms/ml) could form both small and normal colonies. The regrowth of resistant variants could be monitored by luciferase assay of intracellular ATP in cultures incubated with gentamicin (less than or equal to 2 micrograms/ml). In cultures incubated with higher concentrations, regrowth did occur, although this did not result in viability (CFU per milliliter) or ATP levels above those of the initial inocula. The implications of this regrowth for MIC determinations in broth and the possible clinical revelance of the resistant variants are discussed.

Characteristics of Pseudomonas aeruginosa in relation to laboratory-induced resistance to gentamicin

Pseudomonas aeruginosa strain C2 was habituated to gentamicin by serial passage in broth containing increasing concentrations of the antibiotic and up to 250 microgram/ml. The resistant progenies differed from the parent strain in antibiotic susceptibility to two other aminoglycosides, colonial morphology, lytic phage patterns, phage adsorption, and agglutination with the seven Fisher's antisera. All the progenies failed to grow at 42 degrees C and oxidised glucose in O/F tubes after incubation at 37 degrees C for three days but were catalase- and oxidase-positive. Reversion to the original properties of the parent strain was demonstrated in all cases after 10 serial subcultures in antibiotic-free broth.

Specific and non-specific resistance to aminoglycosides in Escherichia coli

The turbidimetric responses of a strain of Escherichia coli K12 to gentamicin and tobramycin were investigated. Both agents showed antibacterial activity below the conventionally measured minimum inhibitory concentration, but exposure to such subinhibitory concentrations of either agent generated a bacterial population which was able to grow in previously inhibitory concentrations at a rate equivalent to that of the parent culture. The increase in resistance was non-specific in that both aminoglycosides were equally affected, and was unstable on multiple passage in drug-free broth. The response to tobramycin was unaffected by the presence of an R factor conferring gentamicin resistance, but exposure of the R factor bearing strain to gentamicin caused a concomitant increase in the resistance to tobramycin, apparently by a non-specific adaptive mechanism similar to that observed with the parent strain. It is suggested that prior treatment of a gentamicin-resistant organism with gentamicin (as may occur during blind therapy) may adversely affect the subsequent response to other aminoglycosides.