Coagulase-negative Staphylococci Strains Research Articles

ANTIBIOTIC RESISTANCE, MECA GENE DETECTION, AND BIOFILM FORMATION ABILITY AMONG COAGULASE-NEGATIVE STAPHYLOCOCCI IN CANCER PATIENTS

Objective: The objective of the study was to identify coagulase-negative staphylococci (CoNS) from various clinical samples and to determine the antibiotic resistance of the isolates by means of automation (VITEK-2), as well as to detect biofilm formation using Congo red agar method and to detect mecA gene by automated identification method (VITEK-2). Methods: All the clinical samples (blood, urine, sputum, BAL, throat swab, wound swab, aspirated fluid, pleural fluid, and pus) received in the microbiology laboratory were processed by aseptic techniques. Clinical samples were inoculated on appropriate media (blood agar, MacConkey agar, and chocolate agar [HIMEDIA]). After inoculation, the culture plates were incubated at 37°C aerobically for 18–24 h for growth. Positive cultures were picked up and further bacterial species identification was done using automated techniques (MALDI- TOF). Results: Among 28 isolates, the most recurrent strains of CoNS are Staphylococcus epidermidis, Staphylococcus hominis, Staphylococcus lugdunensis, and Staphylococcus haemolyticus. The assessment of antibacterial drugs sensitivity shows that all the isolates were more sensitive to daptomycin (S. epidermidis 100%, S. hominis 100%, S. lugdunensis 100%, and S. haemolyticus 42.85%) followed by linezolid (S. epidermidis [69.23%], S. hominis [100%], S. lugdunensis [100%], and S. haemolyticus [57.14%]) and vancomycin (S. epidermidis [100%], S. hominis [40%], S. lugdunensis [100%], S. haemolyticus [42.85%]). The analysis revealed the presence of the mecA gene (67.85%) and biofilm production (85.71%), respectively. Conclusion: Our data indicate that the hospital environment can be colonized by biofilm forming CoNS and transmission of these strains can cause an increased risk of serious nosocomial infections.

High prevalence of multi-drug resistant and different SCCmec types among coagulase-negative Staphylococci spp. collected from clinical samples and skin of healthcare workers in Kerman, Southeast Iran

Coagulase-Negative Staphylococci (CoNS) are an important reservoir of resistance genes. Due to the important role of CoNS in the transmission of antibiotic resistance genes, increasing knowledge about the mechanisms of antibiotic resistance in this bacterium has an important role in controlling infection and preventing the spread of resistance genes in hospital settings. The aim of this study was to determine drug resistance profiles and antibiotic resistance mechanisms in CoNS strains isolated from clinical samples and the skins of healthcare workers in Kerman, Iran. Out of 114 CoNS isolates, 77% (n=88), 17% (n=19), 5% (n=6), and 1% (n=1) were S. epidermidis, S. haemolyticus, S. hominis, and S. saprophyticus, respectively. Two percent (n=2) of isolates were resistant to vancomycin and 14% (n=16) had reduced susceptibility to vancomycin. Also, various resistance genes including mecA, erm, tet, and aminoglycosides modified enzyme (AMEs) genes were detected. In total, SCCmec types IV(37%), III(24%), II(7%), I(5%), and I + III (5%) were detected in isolates. Our findings show that healthcare workers are likely to play an important role in the spread of resistant strains in hospital settings. Therefore, we need further monitoring of healthcare workers to prevent the spread and transmission of resistant CoNS isolates in hospital settings.

Study of aerobic and anaerobic bacterial profile of nosocomial infections and their antibiotic resistance in a referral center, Southwest Iran: A three year cross-sectional study.

BackgroundThe drug resistance is expected to be the most important challenge in infection control in Iran, where there is no local report or standard drug resistance monitoring system. Therefore, this study aimed to investigate the aerobic and anaerobic bacterial profile of nosocomial infections and their antibiotic resistance in Ahvaz, southwest Iran.MethodologyThe gram-positive and gram-negative bacteria were identified on the basis of conventional culture and biochemical tests. The antibiotic resistance of the bacterial isolates against antibiotics was determined by the disk diffusion method.ResultsAmong total 1156 collected positive samples, E. coli and coagulase-negative staphylococci (CoNS) were the most frequent pathogenic gram negative bacteria (GNB) and gram positive bacteria (GPB) respectively. Drug susceptibility testing revealed that among GNB, P. aeruginosa was 100% resistant to amikacin, cefepime, ciprofloxacin and tetracycline. In the case of E. coli, the resistance rate was (98%) for trimethoprim sulfamethoxazole and cefepime. For GPB, S. aureus showed the highest resistance rates to amikacin (100%) and clindamycin (100%). In addition, CoNS strains showed a high level of resistance to doxycycline (100%), erythromycin (100%) and cefoxitin (97%). In Bacteroeides fragilis isolates, the highest resistance rate belonged to clindamycin (72%), and Clostridium perfringens strains showed high level of resistance to penicillin (46%).ConclusionThe results highlighted that there are distinct factors leading to antimicrobial resistance in Ahvaz, southwest Iran. The primary contributors to the resistance development, include poor surveillance of drug-resistant infections, poor quality of available antibiotics, clinical misuse, and the ease of access to antibiotics. Moreover, similar factors such as self-medication and the lack of regulation on medication imports play a role in antibiotic resistance in the region.

Incidence of Tetracycline and Erythromycin Resistance in Meat-Associated Bacteria: Impact of Different Livestock Management Strategies.

The extensive use of antibiotics as growth promoters, or their continued abusive misuse to cure or prevent the onset of bacterial infections as occurs in the intensive farming, may have played a pivotal role in the spread of reservoirs of antibiotic resistance (AR) among food-associated bacteria including pathogens representing risks to human health. The present study compares the incidence of tetracycline and erythromycin resistances in lactic acid bacteria (LAB) and coagulase negative staphylococci (CNS) from fermented products manufacturing using meat from intensive animal husbandry (industrialized manufacturing Italian salami) and from extensive farms (artisanal sausages facilities pork and llama Argentinean sausages). A higher incidence of tetracycline resistance (TET-R) compared to erythromycin resistance (ERY-R) was observed among the 205 isolates. Unlike CNS strains, the LAB showed a significant correlation between the TET-R and the ERY-R phenotypes. Genotypic assessment shows a high correlation with tetK and tetM for the TET-R strains and with ermB and ermC for the ERY-R strains. Multiple correspondence analyses have highlighted the association between AR phenotypes and CNS species isolated from Italian salami, while the susceptible phenotypes were associated with the LAB species from Argentinean sausages. Since antibiotic resistance in meat-associated bacteria is a very complex phenomenon, the assessment of bacterial resistance in different environmental contexts with diverse farming practices and food production technologies will help in monitoring the factors influencing AR emergence and spread in animal production.

Analysis of bacterial infection and drug sensitivity in patients with chronic suppurative otitis media

Objective:To explore the distribution of pathogenic bacteria and drug sensitivity among patients with chronic suppurative otitis media. Methods:Patients with chronic suppurative otitis media who were hospitalized in the Department of Otolaryngology, People's Hospital, Peking University for surgery from January 1, 2019 to May 1, 2021 were enrolled as the subjects, then take the deep secretions of the external auditory canal for bacterial culture. Finally, the distribution and drug sensitivity of the pathogenic bacteria are analyzed. Results:A total of 126 patients were enrolled, of which 53 were culture-positive, and 57 strains of bacteria were isolated, including 47 strains of Gram-positive cocci, 10 strains of Gram-negative bacilli. Among Gram-positive cocci, 24 methicillin-sensitive staphylococcus aureus（MSSA） strains, 7 methicillin-resistant staphylococcus aureus（MRSA） strains, 14 coagulase-negative staphylococcus strains, 1 strain enterococcus faecium, and 1 strain otitis Zurich. 4 strains（4/10） of pseudomonas aeruginosa among Gram-negative bacilli. Among them, MSSA has a high resistance rate to levofloxacin, moxifloxacin, clindamycin, and gentamicin, and high sensitivity to oxacillin, vancomycin, linezolid, and rifampin. MRSA is highly resistant to common antibiotics except vancomycin, rifampicin, and linezolid. The Gram-negative bacilli have higher resistance rates to levofloxacin, aztreonam, ciprofloxacin, ceftazidime, and piperacillin/tazobactam, and to meropenem, imipenem, amika star, cefepoxime, cefoperazone/sulbactam, and tobramycin are more sensitive. The results of univariable and multivariable analysis showed that age and bacterial infection were independent factors related to dry ears, and the duration of the disease history was a non-independent factor. Conclusion:The main pathogenic bacteria infections in patients with chronic suppurative otitis media are MSSA, MRSA, and pseudomonas aeruginosa. Whether it is combined with bacterial infection and age are independent factors related to whether patients with chronic suppurative otitis media could have dry ears. Therefore, patients with chronic suppurative otitis media should be treated with specific antibiotics or surgical interventions as soon as possible in combination with drug sensitivity results to avoid prolonging disease course or causing serious infectious complications.

A More Positive Culture by Resin-containing Media Usage after Suspicious Arthroscopic Infections in Patients Receiving Antimicrobial Therapy.

Although infections following arthroscopic surgery of cruciate ligament and meniscus are uncommon, they have potentially serious consequences for the graft and articular cartilage. This study aimed to investigate the efficacy of correct sampling and appropriate media, especially resin-containing media, for the detection of infections in patients receiving antibiotics under suspicion of joint infection after arthroscopic anterior cruciate ligament (ACL) and meniscal surgery. In such cases, proper sampling and the use of suitable culture media that cause the neutralization of antibiotics are very effective in isolating microorganisms from the patient samples and positive cultures. In total, 10 patients who had received antibiotics with suspected knee infection after arthroscopic ACL and meniscal surgery were identified after referral to surgeons during a period of 10 months and investigated in this study. The sample collection, culture on various media (i.e., resin-containing culture media), microbiological tests, and antibiotic susceptibility tests were performed in this study. The amplification of the mecA gene using PCR assay was accomplished for methicillin-resistant staphylococcus strains. This study was conducted on 10 patients who underwent arthroscopic procedures and had received antibiotics. Overall, joint fluid and tissue culture were positive in 60% of the patients. The resin-containing media revealed a trend toward increased detection of bacteria. Coagulase-negative staphylococcus strains were the most frequently isolated bacteria in arthroscopic ACL surgery infections. Out of five methicillin-resistant staphylococcus strains, four strains were found that were resistant to cefoxitin and positive-mecA designated as methicillin-resistant strains. Except for one case, the rest of the staphylococcal strains were resistant to methicillin but susceptible to vancomycin. Despite uncommon and low percentage of infections after arthroscopic ACL and meniscal surgery, the results of our study showed that correct sampling, appropriate cultures, especially aerobic and anaerobic resin-containing media, and microbiological testing remained useful and valuable for diagnosing bacterial infections.

Assessment of the Bacterial Pollution and Detection of Antibiotic Resistance Genes in Benin: Case of the Hydrographic Channel Complex Cotonou-Nokoué Lake.

The study aims to document the level of contamination of the aquatic ecosystem of the Cotonou-Lake Nokoué canal hydrographic complex by multidrug-resistant bacteria and their resistance genes. For this purpose, water samples were taken from several points of the complex and from the sediments at the depth of the lake. Samples of several species of freshly caught fish products from the lake were also collected. Bacteriological analyses were carried out according to the AFNOR standard (NF U: 47–100). The identification of the different bacterial species isolated was then carried out using the API 20E gallery and specific biochemical tests. The antibiogram of the strains was performed according to the recommendations of the EUCAST. Molecular characterization of the identified strains was carried out by searching for resistance and virulence genes. The results obtained revealed the presence of several bacterial species in water samples and in sediment and intestine samples of fishery products with a predominance of Gram-negative bacilli. The resistance profile of Gram-negative bacilli showed a total resistance to metronidazole (100%). 23% of the strains were also resistant to ciprofloxacin, 41% to amoxicillin, and 60% to aztreonam. Of the Gram-positive cocci identified, 66% was resistant to vancomycin, 7.5% to ciprofloxacin, 71% to erythromycin, and 22% to tetracycline. Regarding the genes sought, blaTEM (46%), blaSHV (24%), and blaCTX-M-15 (31%) were present in the genome of Gram-negative bacilli as resistance genes and fimH (41%) as virulence gene. As for Gram-positive cocci, the van B gene was completely absent. The van A was present at 6.25% in Staphylococcus aureus and mecA at 21.88 and 33.33%, respectively, in Staphylococcus aureus and coagulase-negative staphylococci strains. The high resistance of isolated bacterial strains is a matter of concern and calls for a rational use of antibiotics in order to avoid the transmission of antibiotic resistance from the environment to humans.

Pharmacokinetic/Pharmacodynamic Analysis of Tedizolid Phosphate Compared to Linezolid for the Treatment of Infections Caused by Gram-Positive Bacteria.

Tedizolid and linezolid have antibacterial activity against the most important acute bacterial skin and skin-structure infection (ABSSSIs) pathogens. The objective of this work was to apply PK/PD analysis to evaluate the probability of attaining the pharmacodynamic target of these antimicrobials based on the susceptibility patterns of different clinical isolates causing ABSSSI. Pharmacokinetic and microbiological data were obtained from the literature. PK/PD breakpoints, the probability of target attainment (PTA) and the cumulative fraction of response (CFR) were calculated by Monte Carlo simulation. PTA and CFR are indicative of treatment success. PK/PD breakpoints of tedizolid and linezolid were 0.5 and 1 mg/L, respectively. Probability of treatment success of tedizolid was very high (>90%) for most staphylococci strains, including MRSA and coagulase-negative staphylococci (CoNS). Only for methicillin- and linezolid-resistant S. aureus (MLRSA) and linezolid resistant (LR) CoNS strains was the CFR of tedizolid very low. Except for LR, daptomycin-non-susceptible (DNS), and vancomycin-resistant (VRE) E. faecium isolates, tedizolid also provided a high probability of treatment success for enterococci. The probability of treatment success of both antimicrobials for streptococci was always higher than 90%. In conclusion, for empiric treatment, PK/PD analysis has shown that tedizolid would be adequate for most staphylococci, enterococci, and streptococci, even those LR whose linezolid resistance is mediated by the cfr gene.

Coagulase-negative staphylococci in ewe udder surface and raw milk samples

Coagulase-negative staphylococci (CNS) are among the major causes of subclinical mastitis in dairy ewe flocks. This has a financially significant impact on the ewe dairy sector and consumer health. The determination of the bacterial count, particularly CNS, is critical in terms of the quantity and quality of ovine milk. Thus, the purpose of this study was to quantify the CNS count in the udder surface and raw milk samples of the ewe, in addition to identifying CNS strains (n=8) collected from udder surface and individual raw milk samples by 16S rRNA gene sequencing. A total of 164 samples of udder surface and raw milk originated from four sheep farms were tested. The obtained values were compared between the different farms. Furthermore, values during 2018 and 2019 in the case of Farm I were compared. Significantly higher (p<0.05) average count was observed in udder surface samples taken from Farm I (2.8±1.0 lg CFU/cm2) than that of Farm III samples (2.3±0.6 lg CFU/cm2). In the case of individual raw milk, the higher value was observed in samples derived from Farm III (3.5±0.9 lg CFU/mL), while the obtained value was significantly lower (p<0.05) in samples originated from Farm IV (1.8±0.4 lg CFU/mL). In the bulk tank milk samples, the highest mean value was 5.3±0.4 CFU/mL, and there was no significant (p>0.05) variation between farms. Coagulase-negative staphylococci counts were decreased to a certain extent in both sample types tested during 2019 except for individual raw milk derived from the Tsigai breed. The correlation between the mean CNS counts of udder surface and individual raw milk was very weak (r=0.048). Staphylococcus simulans, Staphylococcus auricularis, and Staphylococcus equorum were identified by molecular sequencing and Staphylococcus simulans were the most frequently identified CNS species. A higher CNS count of bulk tank milk than individual raw milk indicates possible contamination during milking and storage. Therefore, further studies are required to investigate the other sources of bulk tank milk contamination to improve the hygienic quality of milk.

Antimicrobial Susceptibility Patterns and Resistance Trends of Staphylococcus aureus and Coagulase-Negative Staphylococci Strains Isolated from Ocular Infections.

Ocular bacterial infections represent a serious problem that affecting people of all age and genders. These infections can lead to visual impairment and blindness if not properly treated. The current study evaluates the antimicrobial resistance profiles and the resistance trend of both Staphylococcus aureus (S. aureus) and coagulase-negative staphylococci (CoNS), the main pathogens involved in eye infections. A total of 322 isolates of S. aureus and CoNS, were collected from patients with bacterial conjunctivitis and keratitis at the “Luigi Vanvitelli” University Hospital of Campania in Naples, Italy, between 2017 and 2020. The isolated bacteria showed a high percentage of resistance to methicillin and other antibiotics commonly used for the treatment of ocular infections. Trends in antibiotic resistance were not encouraging, recording—especially among CoNS strains—an increase of more than 20% in resistance to methicillin and aminoglycosides during the study period. Instead, the resistance rates to tetracycline had a significant decrease in CoNS isolates while no changes in their susceptibility to fluoroquinolones and macrolides were observed. However, all isolates showed no resistance to trimethoprim/sulfamethoxazole and chloramphenicol. In this scenario, preventive identification of the infection causative agents and the evaluation of the antimicrobial susceptibility patterns are essential to set up an ocular infection effective drug treatment and also prevent antibiotic resistance.

Antibiotic Resistance Profile and Resistance Determination of Bacteria Isolated from Water in Southern Benin

Background: The environment plays an important role in the dissemination of multidrug resistant bacteria, especially through the aquatic ecosystem, including hospital effluents, rivers, but also spring water and drinking water. This study aims to determine selected antimicrobial resistance genes in some aquatic matrices in southern Benin.
 Methods: Collected water samples were filtered through a membrane 0.22 µm thick. After filtration, the membrane was deposited on Muëller Hinton agar. Then the colonies resulting from this subculture were subjected to a microbiological examination by the conventional method. The antibiotic sensitivity test was carried out by the Kirby Bauer method according to the recommendations of the French Society of Microbiology. Resistance genes were looked for by PCR.
 Results: Of the 222 water samples collected, 265 bacterial strains were isolated, the majority of which were strains of Coagulase Negative Staphylococcus (CNS) with 37.74% (n = 100), followed by strains of Klebsiella pneumoniae (21.89%; n = 58), Escherichia coli (10.57%; n = 28). All isolated gram-negative bacilli strains are multidrug resistant with resistance of all strains to amoxicillin, ampicillin and amoxicillin + clavulanic acid. Of the 15 resistance genes searched in the genome of Gram-negative bacilli strains, 8 were detected, namely the TEM, SHV, CTX-M15, VIM, NDM, SUL1, SUL2 and AADA genes. Resistance of CNS strains to amoxicillin, oxacillin and cefoxitin was observed. The meca gene was detected in all CNS strains. The vanA and VanB genes were only detected in strains isolated from drinking water in sachets collected from producers and street sellers.
 Conclusion: These results show the dissemination of resistance genes in Benin and once again confirms the urgency of a global fight against antimicrobial resistance.

Antibacterial and Anti-Biofilm Activity of Omega-3 Polyunsaturated Fatty Acids against Periprosthetic Joint Infections-Isolated Multi-Drug Resistant Strains.

Background: Implantable medical devices, such as prosthetics, catheters, and several other devices, have revolutionized medicine, but they increase the infection risk. In previous decades, commercially available antibiotics lost their activity against coagulase-negative Staphylococci (CoNS) and several other microorganisms. Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are the two major omega-3 polyunsaturated fatty acids (ω-3 PUFAs) with antimicrobial properties. Materials and Methods: In this study, we tested the EPA and the DHA for its antibacterial and anti-biofilm activity in vitro against Staphylococcus epidermidis, Staphylococcus aureus, and different CoNS as reference strains and isolated from patients undergoing orthopedic treatment for implant infections. The tests were carried out with the strains in planktonic and biofilm form. Cytotoxicity assay was carried out with EPA and DHA using human gingival fibroblasts HGF-1. Results: The highest concentration of EPA and DHA promoted the complete killing of S. epidermidis 1457 and S. aureus ATCC 25923 in planktonic form. The fatty acids showed low activity against P. aeruginosa. EPA and DHA completely killed or significantly reduced the count of planktonic bacteria of the patient isolated strains. When incubated with media enriched with EPA and DHA, the biofilm formation was significantly reduced on S. epidermidis 1457 and not present on S. aureus ATCC 25923. The reduction or complete killing were also observed with the clinical isolates. The pre-formed biofilms showed reduction of the cell counting after treatment with EPA and DHA. Conclusion: In this study, the ω-3 PUFAs EPA and DHA showed antimicrobial and anti-biofilm activity in vitro against S. aureus, S. epidermidis, and P. aeruginosa, as well as against multi-drug resistant S. aureus and CoNS strains isolated from patients undergoing periprosthetic joint infections (PJI) treatment. Higher concentrations of the fatty acids showed killing activity on planktonic cells and inhibitory activity of biofilm formation. Although both substances showed antimicrobial activity, EPA showed better results in comparison with DHA. In addition, when applied on human gingival fibroblasts in vitro, EPA and DHA showed a possible protective effect on cells cultured in medium enriched with ethanol. Further studies are required to confirm the antimicrobial activity of EPA and DHA against multi-drug resistant strains and pan-drug resistant strains.

First Case of Staphylococci Carrying Linezolid Resistance Genes from Laryngological Infections in Poland.

Linezolid is currently used to treat infections caused by multidrug-resistant Gram-positive cocci. Both linezolid-resistant S. aureus (LRSA) and coagulase-negative staphylococci (CoNS) strains have been collected worldwide. Two isolates carrying linezolid resistance genes were recovered from laryngological patients and characterized by determining their antimicrobial resistance patterns and using molecular methods such as spa typing, MLST, SCCmec typing, detection of virulence genes and ica operon expression, and analysis of antimicrobial resistance determinants. Both isolates were multidrug resistant, including resistance to methicillin. The S. aureus strain was identified as ST-398/t4474/SCCmec IVe, harboring adhesin, hemolysin genes, and the ica operon. The S. haemolyticus strain was identified as ST-42/mecA-positive and harbored hemolysin genes. Linezolid resistance in S. aureus strain was associated with the mutations in the ribosomal proteins L3 and L4, and in S. haemolyticus, resistance was associated with the presence of cfr gene. Moreover, S. aureus strain harbored optrA and poxtA genes. We identified the first case of staphylococci carrying linezolid resistance genes from patients with chronic sinusitis in Poland. Since both S. aureus and CoNS are the most common etiological factors in laryngological infections, monitoring of such infections combined with surveillance and infection prevention programs is important to decrease the number of linezolid-resistant staphylococcal strains.

Biofilm-Formation Ability and the Presence of Adhesion Genes in Coagulase-Negative Staphylococci Isolates from Chicken Broilers.

Simple SummaryBacteria of the genus Staphylococcus are universally present on the mucous membranes and skin of warm-blooded animals. They are divided into two groups on the basis of their ability to clot blood plasma: the coagulase-positive (CoPS) and coagulase-negative staphylococci (CoNS). Some species can cause opportunistic infections in poultry. Identification and characterization of strains of the genus Staphylococcus isolated from farm animals are crucial in epidemiological research and for developing effective methods to treat infections and food poisoning induced by these bacteria. The main virulence factor of coagulase-negative staphylococci is considered to be their ability to form complex biofilm structures on the surfaces of damaged tissues. Biofilms increase the invasive properties of CoNS and their ability to cause infection. The purpose of this study was to determine the biofilm-forming potential of coagulase-negative Staphylococcus strains isolated from poultry. The frequency of selected genes potentially playing a role in the biofilm formation process was also determined. The results of the study indicate that the majority (79.3%) of CoNS isolated from broiler chickens in this study were capable of producing a biofilm.The aim of the study was to analyze the biofilm-production capacity of 87 coagulase-negative Staphylococcus strains (CoNS) isolated from broiler chickens and to determine the occurrence of biofilm-associated genes. The biofilm production capacity of staphylococci was assessed using the microtiter plate method (MTP), and the frequency of genes was determined by PCR. The ability to form a biofilm in vitro was shown in 79.3% of examined strains. Strong biofilm capacity was demonstrated in 26.4% of strains, moderate capacity in 25.3%, weak capacity in 27.6%, and a complete lack of biofilm production capacity in 20.7% of strains. The icaAB gene responsible for the production of extracellular polysaccharide adhesins was detected in 6.9% of strains. The other four genes, i.e., bap (encoding biofilm-associated protein), atlE (encoding cell surface protein exhibiting vitronectin-binding activity), fbe (encoding fibrinogen-binding protein), and eno (encoding laminin-binding protein) were detected in 5.7%, 19.5%, 8%, and 70.1% of strains, respectively. Demonstration of genes that play a role in bacterial biofilm formation may serve as a genetic basis to distinguish between symbiotic and potentially invasive coagulase-negative staphylococcal strains.

Virulence Factors in Coagulase-Negative Staphylococci.

Coagulase-negative staphylococci (CoNS) have emerged as major pathogens in healthcare-associated facilities, being S. epidermidis, S. haemolyticus and, more recently, S. lugdunensis, the most clinically relevant species. Despite being less virulent than the well-studied pathogen S. aureus, the number of CoNS strains sequenced is constantly increasing and, with that, the number of virulence factors identified in those strains. In this regard, biofilm formation is considered the most important. Besides virulence factors, the presence of several antibiotic-resistance genes identified in CoNS is worrisome and makes treatment very challenging. In this review, we analyzed the different aspects involved in CoNS virulence and their impact on health and food.

Nasal colonization and antibiotic resistance patterns of Staphylococcus species isolated from healthy horses in Tripoli, Libya.

ABSTRACTThe present study investigated the colonization rates and antimicrobial susceptibility of Staphylococcus species isolated from the nostrils of healthy horses. A nonselective laboratory approach was applied, followed by confirmation using a Phoenix automated microbiological system. Among the 92 horses included in the study, 48.9% (45/92) carried Staphylococcus species of mostly the coagulase-negative staphylococci (CoNS) type yielding 70 Staphylococcus strains. Of these strains, 37.1% (26/70; 24 CoNS and 2 coagulase-positive staphylococci; CoPS) were identified as methicillin-resistant staphylococci (MRS) expressing significant resistance to important antimicrobial classes represented mainly by subspecies of CoNS. This is the first study reporting a high prevalence of various Staphylococcus species, particularly strains of CoNS expressing multidrug resistance patterns of public health concern, colonizing healthy horses in Libya.

A Three-Year Analysis of Ocular Infections in a Tertiary Care University Hospital in Turkey

Ocular infections may result in severe vision and eye loss. Especially in keratitis and endophthalmitis, it is essential to identify the causative microorganism and treat it with appropriate antimicrobials. This study aims to investigate microorganisms isolated from various samples in ocular infections and their sensitivity to antibiotics. The samples, e.g., abscess, swab, were inoculated to suitable media and at appropriate ambient conditions at 35 - 37°C for 24 - 48 hours. Sterile liquid samples were cultivated in a blood culture bottle. The isolated microorganisms were identified by classical biochemical methods and by using an automatic identification system when necessary. Antibiotic susceptibility tests were performed by the disc diffusion method and interpreted according to CLSI criteria. From a total of 167 ocular samples from 69 patients, 78 (46.7%) microorganisms were isolated. Thirteen (19%) infections were found to be polymicrobial. Three bacteria were isolated from one of them and two bacteria from 12 of them. Twenty-one (30%) of the patients were newborns, and two were children. The average age of adult patients was 55.45 ± 19.7 years. Gram-positive bacteria (n = 46, 59%) were found to be more common than Gram-negative (n = 27, 35%) among all bacteria isolated over three years. Gram-positive bacteria included Staphylococcus aureus (n = 17, 22%), coagulase-negative staphylococci (CNS) (n = 13, 17%), and streptococci (n = 10, 13%). Pseudomonas aeruginosa (n = 8, 10%) was the most common bacterium of the Gram-negative bacteria. Besides, two anaerobic bacteria (2.6%), two fungi (2.6%), and one (1.3%) Nocardia spp. were isolated. It was determined that 35% of S. aureus strains and 46% of CNS strains were resistant to methicillin. Various and rare microorganisms can be isolated from ocular infections. However, it is still seen that Gram-positive bacteria are more common than Gram-negative. Multi-resistant Gram-negative rods and high rates of methicillin-resistance in staphylococci can affect treatment regimens.

Microarray-based detection of resistance genes in coagulase-negative staphylococci isolated from cattle and buffalo with mastitis in Egypt.

The present study aimed to provide a detailed characterization of coagulase-negative staphylococci (CoNS) isolated from cows and buffaloes with mastitis. The study included seventy-five CoNS isolates (60 came from cattle and 15 from buffaloes) originating from 68 individual quarters of 67 dairy cows (53 cattle and 14 buffaloes). The animals belonged to five different small holding dairy herds (n = 140 cows) that show clinical or subclinical mastitis. CoNS isolates were phenotypically characterized using MALDI-TOF-MS and were further genotypically characterized by microarray-based assays. Furthermore, the antimicrobial susceptibility of CoNS strains which carried the mecA gene was examined by broth microdilution. The occurrence of CoNS in the respective five herds was 10.5%, 14.7%, 14.8%, 12.8%, and 9.9%, with an average of 12.4%. Six different CoNS species were identified: S. sciuri (n = 37; 30 from cattle and 7 from buffaloes), S. chromogenes (n = 14; 8 from cattle and 6 from buffaloes), S. haemolyticus (n = 10; nine from cattle and one buffalo), S. xylosus (n = 10; nine from cattle and one buffalo), S. hyicus (n = 2), S. warneri (n = 1), and unidentified CoNS (n = 1). Twenty percent (20%) of CoNS isolates (17.3% of cattle origin) carried at least one antimicrobial resistance gene, while 4% of the isolate including two isolates of S. haemolyticus and one S. warneri of cattle origin carried the mecA gene and were phenotypically identified as methicillin-resistant strains. The genes detected were blaZ (16%), followed by tet(K) (8%), aacA-aphD (4%), aphA3 (2.6%), msr(A) (2.6%), [far1 (2.6%),and fusC (2.6%)], sat (2.6%), and cat (1.3%) conferring resistance to penicillin, tetracycline, gentamicin, neomycin/kanamycin, erythromycin, fusidic acid, streptothricin, and chloramphenicol, respectively. The majority of investigated CoNS strains displayed considerably low prevalence of resistance genes, while resistance to more than three antibiotics was found in S. haemolyticus and S. warneri. Implementing effective preventive measures is, therefore, important for limiting the transmission of CoNS, rather than using antibiotics to control mastitis in bovines.

Features of the microbial landscape of patients' wounds at different periods of existence

Aim: to analyze the results of a microbiological diagnostics of wound swabs in patients with wounds of different duration. Material and methods. The results of bacteriological swabs of 405 wound samples from acute wounds (AW, up to 3 weeks, n=176) and chronic wounds (CW, more than 3 weeks, n=229) were analyzed. Results. Differences were found between the groups in the frequency of obtaining negative swabs (in AW – 24.7% [18.6; 30.9] cases), detection of monocultures (in AW – 50.9% [45.3; 56.5] cases) and microbial associations (in CW – 42.0% [35.4; 48.6]). Gram(+) bacteria – 73.1% and 62.1% (Staphylococcus spp., E. faecalis, Streptococcus gr. viridans) were dominant in wounds; Gram(-) bacteria (23.8% in AW and 33.6% in CW), represented by Enterobacterales, Pseudomonas and Acinetobacter, in CW were characterized by a wider species diversity. Only Gram(+) bacteria were found in AW up to 1 day of the existence; a change in the qualitative composition of microflora was manifested starting from the 10th day of the existence of wounds in the form of the appearance of Enterobacterales, Pseudomonas and Acinetobacter. The prevalence of methicillin-resistant S. aureus and coagulase-negative staphylococci strains was 52% and 54% for AW, 42% and 72% for CW, respectively. E. faecalis showed a high level of resistance to aminoglycosides and fluoroquinolones in all the wounds (>50% of isolates). Gram(+) bacteria were completely susceptible to vancomycin, teicoplanin, linezolid, and tigecycline. The sensitivity of A. baumannii and P. aeruginosa to carbapenems in all cases was high – 69% and 74%, to colistin – 100%. The sensitivity to aminoglycosides – amikacin, tobramycin in P. aeruginosa was 76% and 78%, in A. baumannii – 48% and 59%, respectively. K. pneumoniae showed complete sensitivity to carbapenems. Other Enterobacteriaceae were less resistant than K. pneumoniae. Conclusion. The results of a microbiological diagnostics of wound swabs made it possible to determine the qualitative structure of microflora and its differences depending on the duration of wound existence. The data obtained are the basis for further research, allowing to establish priority pathogens that disrupt the process of wound healing and are the cause of the formation of chronic wounds.

Resistance to antimicrobials and vancomycin treatment in neonatal sepsis in a hospital in Brazil

Objective: To describe the antimicrobial resistance profile of strains isolated from neonates with septicemia undergoing vancomycin treatment, to determine the agreement of treatment with guideline and blood cultures, to assess the presence of acute kidney injury (AKI) and the clinical outcome in a hospital in Brazil. Methods: A total of 51 newborns treated with vancomycin were studied in the period from January to December 2017. Treatment assessment was verified by the compliance with the Rational Use and Insurance Policy of Antibiotics in Neonatology and blood culture. The presence of AKI was based on the results of serum creatinine. The data were monitored by the computerized system of the laboratory. Results: The main isolated strain was Staphylococcus (coagulase negative) (82.9%), 93.5% with resistance to oxacillin for early infections and 100% for late infections. The same strain showed 54.8% resistance to gentamicin for cases of early sepsis and 66.6% for late sepsis. There were no cases of resistance to vancomycin. The treatments agreed with the reference protocol in 46.3% and with the results of blood cultures in 56%. Only two cases of AKI are observed. Conclusions: The oxacillin-resistant coagulase-negative staphylococcus strains were the main causes of neonatal sepsis. The use of gentamicin for sensitive strains may reduce the use of vancomycin. The results suggest the need for better standardization of the treatment to reduce the risk of toxicity and rational use of therapeutic resources.