The survival rate, p , of a measured inoculum of Staph. aureus in a standard volume of denbrinated blood, is a reliable quantitative measure of the bactericidal power of blood. The number of viable organisms in the inoculum and in the blood-bacterium mixture may be estimated with the necessary accuracy by counts of colonies developing from measured volumes of the fluids let fall on to the surface of solid media. Fildes' agar was the most suitable medium for this surface-viable count, and was selected on the basis of four criteria; of the media tested it yielded the highest counts, and the counts conformed most closely to a Poisson series; and on it the mean colony size was maximum, and the coefficient of variation of colony size was minimum. On this medium, the close conformity of the separate count values to a Poisson series enabled the standard error of the survival rate to be determined from a simplification of the general expression for the standard error of a ratio. The number of colonies growing from a sample of a blood-bacterium mixture may be reduced, not by killing of the individual cocci, but as a result of their aggregation either by agglutinins in the blood, or in the cytoplasm of leucocytes that are phagocytic but not bactericidal. It appears that these mechanisms are unlikely to operate in blood-bacterium mixture containing relatively few organisms; in such mixtures the survival rate is a reflexion of the killing power only. The immunological significance of p has not been investigated, but the range of values for healthy human adults differs significantly from that for sufferers from chronic staphylococcal infection. Moreover, by the technique employed differences may be detected between individual values of p that cannot reasonably be attributed to technical or sampling errors.

The Estimation of the Bactericidal Power of the Blood. With a Note by J. O. IRWIN.

Acinetobacter baumannii is a Gram-negative ESKAPE microorganism that poses a threat to public health by causing severe and invasive (mostly nosocomial) infections linked with high mortality rates. During the last years, this pathogen displayed multidrug resistance (MDR), mainly due to extensive antibiotic abuse and poor stewardship. MDR isolates are associated with medical history of long hospitalization stays, presence of catheters, and mechanical ventilation, while immunocompromised and severely ill hosts predispose to invasive infections. Next-generation sequencing techniques have revolutionized diagnosis of severe A. baumannii infections, contributing to timely diagnosis and personalized therapeutic regimens according to the identification of the respective resistance genes. The aim of this review is to describe in detail all current knowledge on the genetic background of A. baumannii resistance mechanisms in humans as regards beta-lactams (penicillins, cephalosporins, carbapenems, monobactams, and beta-lactamase inhibitors), aminoglycosides, tetracyclines, fluoroquinolones, macrolides, lincosamides, streptogramin antibiotics, polymyxins, and others (amphenicols, oxazolidinones, rifamycins, fosfomycin, diaminopyrimidines, sulfonamides, glycopeptide, and lipopeptide antibiotics). Mechanisms of antimicrobial resistance refer mainly to regulation of antibiotic transportation through bacterial membranes, alteration of the antibiotic target site, and enzymatic modifications resulting in antibiotic neutralization. Virulence factors that may affect antibiotic susceptibility profiles and confer drug resistance are also being discussed. Reports from cases of A. baumannii coinfection with SARS-CoV-2 during the COVID-19 pandemic in terms of resistance profiles and MDR genes have been investigated.

Acinetobacter baumannii Antibiotic Resistance Mechanisms.

The role of food-producing environments in the emergence and spread of antimicrobial resistance (AMR) in EU plant-based food production, terrestrial animals (poultry, cattle and pigs) and aquaculture was assessed. Among the various sources and transmission routes identified, fertilisers of faecal origin, irrigation and surface water for plant-based food and water for aquaculture were considered of major importance. For terrestrial animal production, potential sources consist of feed, humans, water, air/dust, soil, wildlife, rodents, arthropods and equipment. Among those, evidence was found for introduction with feed and humans, for the other sources, the importance could not be assessed. Several ARB of highest priority for public health, such as carbapenem or extended-spectrum cephalosporin and/or fluoroquinolone-resistant Enterobacterales (including Salmonella enterica), fluoroquinolone-resistant Campylobacter spp., methicillin-resistant Staphylococcus aureus and glycopeptide-resistant Enterococcus faecium and E. faecalis were identified. Among highest priority ARGs bla CTX -M, bla VIM, bla NDM, bla OXA -48-like, bla OXA -23, mcr, armA, vanA, cfr and optrA were reported. These highest priority bacteria and genes were identified in different sources, at primary and post-harvest level, particularly faeces/manure, soil and water. For all sectors, reducing the occurrence of faecal microbial contamination of fertilisers, water, feed and the production environment and minimising persistence/recycling of ARB within animal production facilities is a priority. Proper implementation of good hygiene practices, biosecurity and food safety management systems is very important. Potential AMR-specific interventions are in the early stages of development. Many data gaps relating to sources and relevance of transmission routes, diversity of ARB and ARGs, effectiveness of mitigation measures were identified. Representative epidemiological and attribution studies on AMR and its effective control in food production environments at EU level, linked to One Health and environmental initiatives, are urgently required.

Role played by the environment in the emergence and spread of antimicrobial resistance (AMR) through the food chain

We aimed to isolate Acinetobacter baumannii (A. baumannii) from wound infections, determine their resistance and virulence profile, and assess the impact of Silver nanoparticles (AgNPs) on the bacterial growth, virulence and biofilm-related gene expression. AgNPs were synthesized and characterized using TEM, XRD and FTIR spectroscopy. A. baumannii (n = 200) were isolated and identified. Resistance pattern was determined and virulence genes (afa/draBC, cnf1, cnf2, csgA, cvaC, fimH, fyuA, ibeA, iutA, kpsMT II, PAI, papC, PapG II, III, sfa/focDE and traT) were screened using PCR. Biofilm formation was evaluated using Microtiter plate method. Then, the antimicrobial activity of AgNPs was evaluated by the well-diffusion method, growth kinetics and MIC determination. Inhibition of biofilm formation and the ability to disperse biofilms in exposure to AgNPs were evaluated. The effect of AgNPs on the expression of virulence and biofilm-related genes (bap, OmpA, abaI, csuA/B, A1S_2091, A1S_1510, A1S_0690, A1S_0114) were estimated using QRT-PCR. In vitro infection model for analyzing the antibacterial activity of AgNPs was done using a co-culture infection model of A. baumannii with human fibroblast skin cell line HFF-1 or Vero cell lines. A. baumannii had high level of resistance to antibiotics. Most of the isolates harbored the fimH, afa/draBC, cnf1, csgA and cnf2, and the majority of A. baumannii produced strong biofilms. AgNPs inhibited the growth of A. baumannii efficiently with MIC ranging from 4 to 25 µg/ml. A. baumannii showed a reduced growth rate in the presence of AgNPs. The inhibitory activity and the anti-biofilm activity of AgNPs were more pronounced against the weak biofilm producers. Moreover, AgNPs decreased the expression of kpsMII , afa/draBC,bap, OmpA, and csuA/B genes. The in vitro infection model revealed a significant antibacterial activity of AgNPs against extracellular and intracellular A. baumannii. AgNPs highly interrupted bacterial multiplication and biofilm formation. AgNPs downregulated the transcription level of important virulence and biofilm-related genes. Our findings provide an additional step towards understanding the mechanisms by which sliver nanoparticles interfere with the microbial spread and persistence.

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Antibiofilm and antivirulence potential of silver nanoparticles against multidrug-resistant Acinetobacter baumannii.

Effect of ozonation-based disinfection methods on the removal of antibiotic resistant bacteria and resistance genes (ARB/ARGs) in water and wastewater treatment: a systematic review.

Acinetobacter baumannii (A. baumannii) is a miscellaneous bacterium with ability of extensive antibiotic resistance. A. baumannii strains have also been isolated from animal origins. The objective of our atudy was characterization of A. baumannii antibiotic resistance and virulence traits from turkey and chicken raw meat. Of 576 turkey and 424 chicken specimens during 2017-2019, 200 (120 from turkey and 80 from chicken) isolates were identified as A. baumannii. Virulence factors and antibiotic resistance patterns of A. baumannii were determined using polymerase chain reaction (PCR) technique and Kirby-Bauer test. All the isolates were resistant to tetracycline and cefoxitin and 81 % and 56 % of them produced ESBLs and carbapenemases. Also 74 % of them (34 % from chicken and 40 % from turkey) were multidrug-resistant (MDR) A. baumannii. Colistin and fosfomycin non-susceptibility was detected among 12 % and 10 % of them, respectively. The existence of tetA, dfrA, tetB, blaoxa-51-like, blaoxa-23-like, sul1, blaoxa-24-like, blaoxa-58-like, fosA3 and mcr-1 genes accounted for 80 %, 71 %, 70.5 %, 66 %, 62 %, 43 %, 34 %, 22 %, 11 % and 13 % of them, repectively. Additionally, predominant virulence factors included the fimH, afa/draBC, sfa/foc DE, cnfI and cnf2 genes. The rate of antibiotic resistance genes and virulence factors was not significantly different between turkey and chicken (p > 0.05). High rate of antibiotic non-susceptibility even against last-line resorts in poultry products is a concern and suggest that animals play a potential role as reservoirs of transmission of MDR A. baumannii.

Drug resistance and virulence traits of Acinetobacter baumannii from Turkey and chicken raw meat

Background and aim Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most recognized "superbugs" and a common cause of community-associated and nosocomial infections; furthermore, when chicken meat is considered a good growth medium for S. aureus to make a plausible vehicle to propagate MRSA, then this study was conducted to evaluate the efficiency of ozonated water (0.5 ppm) in the elimination or reduction of MRSA contaminating fresh and frozen chicken meat sold in local markets in the Wasit Province. Materials and methods A total of 72 samples of fresh and frozen chicken meat were randomly collected from dissimilar native markets: Fresh chicken meat (n=32) and frozen chicken meat (n=40). Isolation and identification of MRSA isolates were conducted using standard bacteriological, biochemical, RapID™ Staph Plus System (Remel, R8311009), and latex agglutination tests such as Dry SPOT Staphytect Plus (Oxoid, DR0100M) and PBP2' Test Kit (Oxoid, DR0900A). The generation of ozone (O3) was carried out using O3 generator (A2Z/AQUA-6, USA), and its concentration (ppm) in water was determined using CHE-Mets®-Kit, USA. Results A total of 39 (54.2%) of 72 fresh and frozen chicken meat were positive for S. aureus; of those 39 positive samples, 13 (33.3%) were identified as MRSA. The antibiotic sensitivity test results revealed that all MRSA isolates had multiple resistance to at least four antimicrobial agents for which these isolates had 12 antibiotic resistance patterns. Results of O3 treatment in MRSA isolate contaminating 13 of both fresh and frozen chicken meat samples showed that, after treatment with ozonated water (0.5 ppm/4°C), the overall negative samples were 23.1% and 69.2% for 30 and 45 min, respectively. The decrease in the percentage of positive samples was very significant from a public health perspective. Furthermore, the antimicrobial efficacy of ozonated water (0.5 ppm) on the reduction of the MRSA count (log10 colony-forming units [CFU]/ml) was assessed in four positive samples of fresh and frozen chicken meat, and the results revealed that, after treatments, the overall reduction was 2-4 log10 (CFU/ml) after 45 min. This reduction is highly significant from a public health perspective. Conclusion From the data obtained from this study, it can be concluded that fresh and frozen chicken meat sold in the different markets of Wasit Province was highly contaminated by S. aureus during the study period with a total prevalence of 54.2%; among those, 33.3% were recognized as MRSA. Under the conditions described in the present study, O3 at the concentration of 0.5 ppm is highly effective in reducing the number of MRSA-positive samples and the number decreased with increased exposure time to ozonated water at the same concentration. These findings indicated that O3 treatment might constitute the basis for an alternative method to reduce meat contamination with foodborne pathogens such as MRSA.

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Antibacterial effect of ozonated water against methicillin-resistant Staphylococcus aureus contaminating chicken meat in Wasit Province, Iraq.

Detection of methicillin or multidrug resistant Staphylococcus aureus (MRSA) in locally produced raw milk and soft cheese in Baghdad markets

Campylobacter is a public cause of globally identified human gastrointestinal disease. Nonetheless, in Iraq many sides of the epidemiology of campylobacteriosis and its impact on public health remain poorly understood. Hence, this study was taken to offer reference information on the prevalence rate, sensitivity to antibiotics and biotyping of Campylobacter in poultry products sold in the Wasit markets. A total of 85 samples were collected including chicken (n = 45) and turkey (n =40) meat were surveyed for isolation and identification. Thermotolerant Campylobacter was detected in 54 samples by which Campylobacter jejuni (C. jejuni) was recognized as a main species accounting for 37(68.5%),while Campylobacter coli (C. coli) had 17 (31.5%) of the positive samples. Highest resistance was perceived to oxacillin and tetracycline as (94.4% and 85.2%), respectively. While lowest rate of resistance, 29.6% was detected against gentamicin. Campylobacter coli isolates showed higher resistance rate than C. jejuni isolates towards the selected antibiotics. In addition, multiple drug resistance (MDR) to at least three antibiotics was detected in the vast majority (90.7%) of the experienced isolates. Forty- three (79.6%) of the isolates had multiple antibiotic resistance index (MAR-index) 0.4 and above. Results of biotyping showed that biotype I was the predominant biotype in the two species as 70.2 and 76.5 proportions in C. jejuni and C. coli, respectively. Our results proposed that the presence of Campylobacter in poultry with greater resistance to erythromycin and/ or ciprofloxacin triggers the public health alarm and accentuates the education of consumers on the quality and safety of such foods.

https://www.foodandnutritionjournal.org/pdf/vol7no3/Nutrition_Vol_7_No3_p_905-917.pdf

Prevalence Rate, Antibiotic Resistance and Biotyping of Thermotolerant Campylobacter Isolated from Poultry Products Vended in Wasit Markets

Irrational and inappropriate prescribing of antibiotics is a major problem that can lead to the development of antimicrobial resistance (AMR). In Zambia, there is insufficient information on the prescribing patterns of antibiotics according to the World Health Organization (WHO) AWaRe classification. Therefore, this study assessed the prescribing patterns of antibiotics using the AWaRe classification during the COVID-19 pandemic at the University Teaching Hospital in Lusaka, Zambia. A cross-sectional study was conducted using 384 patient medical files at the University Teaching Hospital in Lusaka, Zambia, from August 2022 to September 2022. All antibiotics were classified according to the WHO “AWaRe” tool and assessed for appropriateness using the 2020 Zambian Standard Treatment Guidelines. Of the 384 patient medical files reviewed, antibiotics were prescribed 443 times. The most prescribed antibiotics were ceftriaxone (26.6%), metronidazole (22.6%), amoxicillin (10.4%), amoxicillin/clavulanic acid (5.6%), and azithromycin (5%). The prescribing of 42.1% of “Watch” group antibiotics was greater than the recommended threshold by the WHO. Most antibiotics were prescribed for respiratory infections (26.3%) and gastrointestinal tract infections (16.4%). The most prescribed antibiotic was ceftriaxone, a Watch antibiotic. This is a worrisome observation and calls for strengthened antimicrobial stewardship and implementation of the AWaRe framework in prescribing antibiotics.

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Prescribing Patterns of Antibiotics According to the WHO AWaRe Classification during the COVID-19 Pandemic at a Teaching Hospital in Lusaka, Zambia: Implications for Strengthening of Antimicrobial Stewardship Programmes

Manal Hadi Ghaffoori Kanaan

Papers

Drug resistance and virulence traits of Acinetobacter baumannii from Turkey and chicken raw meat

Antibacterial effect of ozonated water against methicillin-resistant Staphylococcus aureus contaminating chicken meat in Wasit Province, Iraq.

Detection of methicillin or multidrug resistant Staphylococcus aureus (MRSA) in locally produced raw milk and soft cheese in Baghdad markets

Prevalence Rate, Antibiotic Resistance and Biotyping of Thermotolerant Campylobacter Isolated from Poultry Products Vended in Wasit Markets

Prescribing Patterns of Antibiotics According to the WHO AWaRe Classification during the COVID-19 Pandemic at a Teaching Hospital in Lusaka, Zambia: Implications for Strengthening of Antimicrobial Stewardship Programmes