Antimicrobial Resistance Of Coagulase-negative Staphylococci Research Articles

SG-APSIC1101: Virulence factors and antimicrobial resistance in coagulase-negative staphylococci isolated from blood of neonates

Objectives: To determine virulence genes and sensitivity to antibacterial drugs of Staphylococcus epidermidis isolated from blood cultures of newborns. Methods: A study of сoagulase-negative Staphylococcus (CoNS) from newborns with sepsis was conducted in the regional perinatal center in Karaganda, Kazakhstan. Blood-culture identification was performed using MALDI-TOF MS. Virulence factors were determined on primers (sdrG, sdrG, atl, lip, nuc, ebh, hlb, sspA, sspB, and gehD) with PCR (Bio-Rad CFX 96). Susceptibility to antibiotics determination was carried out using the disc-diffusion method. Testing with cefoxitin was used to detect methicillin resistance in staphylococci. Results: Overall, 18 Staphylococcus epidermidis isolates from blood cultures of newborns with sepsis were investigated from January to December 2021. The frequency of detection of virulence genes was distributed as follows: atl (94.5%), sspB (94.5%), sspA (89%), gehD (89%), ebh (89%), hlb (72%), sdrG (39%), sdrF (28%), nuc (28%), and lip (13%). Also, 10 isolates (55%) were resistant to cefoxitin (MRSE). Furthermore, 72% of S. epidermidis isolates showed resistance to azithromycin and 33% were resistant to clindamycin and gentamicin. Also, 39% of strains were resistant to fluorchinolones. All isolates were susceptible to vancomycin, linezolid, and fusidic acid. Conclusions:S. epidermidis strains isolated from blood cultures had high rates of exoenzymes sspB, sspA, gehD, autolysin (atl), β-hemolysin (hlb), and cell-wall–associated fibronectin-binding protein (ebh). Among 18 neonatal sepsis pathogens, 10 (55%) were MRSE, so it is necessary to pay attention to antibiotic therapy adjustment.

Molecular characterisation of antimicrobial resistance in coagulase negative staphylococci isolated from bovine subclinical mastitis

Coagulase negative staphylococci (CNS) are emerging as the most prevalent causative agent of bovine mastitis. They are resistant to many commonly used antibiotics due to the presence of antimicrobial resistance (AMR) genes. A study was conducted to evaluate the AMR profiling of CNS isolated from bovine subclinical mastitis.Coagulase negative staphylococci were isolated from 49 (44.95 per cent) of the subclinical mastitis samples. Disc diffusion assay revealed that highest resistance was shown against gentamicin (42.85 per cent) followed by methicillin (32.6 per cent), ceftriaxone – tazobactam (24.48 per cent), enrofloxacin (20.4 per cent), tetracycline (16.32 per cent) and least resistance to cotrimoxazole (4 per cent). Genotypic characterisation of AMR genes such as mecA, aacA-aphD and norA by PCR was done for determining resistance to methicillin, gentamicin and fluroquinolone resistance. The CNS carried aacA-aphD, norA and mecA in 44.89 per cent, 32.65 per cent and 14.28 per cent, respectively. Comparison of phenotypic and genotypic characterisation of AMR in CNS was carried out by McNemar test and it was found that there was significant difference between the presence of mecA gene and methicillin resistance. There was no significant difference noticed forcharacterisation of phenotypic and genotypic AMR of CNS for gentamicin and fluroquinolone resistance.

Pathogenicity and Antimicrobial Resistance in Coagulase-Negative Staphylococci

The coagulase-negative staphylococci (CoNS) group was considered saprophytic or rarely pathogenic for many years. Since the first case of septicemia caused by CoNS, there has been a progressive increase in the prevalence of healthcare-associated infections caused by CoNS. The CoNS group has emerged as one of the main causes of nosocomial infections related to vascular catheters and prostheses, especially among immunocompromised patients. This gradual increase in infections is due to the change in the relationship between patients and procedures since CoNS are closely related to devices implanted in the human body. CoNS are successful in colonizing the host because they have several virulence mechanisms, such as biofilm formation and production of enzymes and toxins, in addition to several mechanisms of resistance to antimicrobials. Despite their great clinical relevance, few studies have focused on CoNS’s pathogenicity and resistance to antimicrobials, which reveals the current need to better understand the factors by which this group became pathogenic to humans and other animals. This review aims to synthesize the aspects related to the pathogenicity and antimicrobial resistance in CoNS.

Isolation and antimicrobial resistance of coagulase-negative staphylococci recovered from healthy tortoises in Minas Gerais, Brazil

ABSTRACT: In the last few decades, there has been a global increase in the adoption of reptiles as companion animals, mainly turtles and tortoises. Considering the popularity of reptiles as pets in Brazil, and a notable lack of data about potentially pathogenic staphylococci in these animals, this study isolated and evaluate the antimicrobial susceptibility of staphylococcal species from healthy tortoises (Chelonoidis carbonaria) in Brazil. During a 12-month period (February 2019 to February 2020), cloacal swabs from 66 healthy tortoises were collected at the Wild Animals Screening Center in Belo Horizonte, Minas Gerais, Brazil. The swabs were plated onto mannitol salt agar for staphylococci isolation, and species identification was performed using MALDI-TOF MS. Antimicrobial susceptibility was investigated using the disk diffusion method, and the presence of the mecA gene was investigated by PCR to detect methicillin resistance. Of the tested animals, 72.7% were positive for staphylococcal isolation. All isolates were coagulase-negative staphylococci (CoNS), and Staphylococcus sciuri (81.3%), and S. xylosus (12.5%) were the most frequently isolated species. The majority of the isolates (56%) were resistant to at least one antimicrobial agent. A high frequency of resistance was observed for penicillin (35.5%) and tetracycline (29.1 %). All strains were susceptible to cefoxitin, chloramphenicol, ciprofloxacin, erythromycin, and gentamicin. All isolates were negative for the mecA gene. The present work suggests that healthy tortoises are mainly colonized by CoNS, especially S. sciuri. Half of the isolates were resistant to at least one antimicrobial, raising questions regarding the possible role of these animals as reservoirs of antimicrobial resistance genes.

Frequency, Distribution, and Antimicrobial Resistance of Coagulase-Negative Staphylococci Isolated from Clinical Samples in Dogs and Cats.

This study aimed to investigate the frequency, distribution, and antimicrobial resistance of coagulase-negative staphylococci (CoNS) obtained from clinical samples from dogs and cats and to classify any methicillin-resistant CoNS (MRCoNS). The samples were collected in 2017-2018, and species identification and antimicrobial susceptibility testing were routinely performed using the Vitek2 system. Among 1,056 staphylococci, 185 CoNS (17.5%) were obtained and included 18 species from dogs (n = 116) and 14 species from cats (n = 69). The predominant species were Staphylococcus chromogenes (31.4%), Staphylococcus hominis ssp. hominis (16.2%), Staphylococcus warneri (10.8%), and Staphylococcus epidermidis (8.1%). The primary isolation sites were the skin and urinary tract. High levels of resistance to β-lactams (65.4%), tetracycline (44.3%), clindamycin (36.8%), and erythromycin (30.8%) were observed. Twenty-five MRCoNS (13.4%), mainly Staphylococcus haemolyticus (n = 8), S. epidermidis (n = 6), and S. hominis ssp. hominis (n = 5), were identified. SCCmec type V (n = 8) was the most common type, followed by SCCmec type IV (n = 6) and SCCmec type III (n = 2), whereas nontypable SCCmec were classified into nine MRCoNS. Some CoNS have been recorded in humans, and these might be transferred to and cause subsequent infections in humans. Moreover, the diversity of SCCmec types and resistant strains suggested that they may serve as a reservoir of resistance genes among staphylococci.

Antimicrobial resistance in coagulase-negative staphylococci isolated from subclinical mastitis in Ettawa Crossbred goat (PE) in Yogyakarta, Indonesia

Abstract. Suwito W, Nugroho WS, Wahyuni AETH, Sumiarto B. 2021. Antimicrobial resistance in coagulase-negative staphylococci isolated from subclinical mastitis in Ettawa Crossbred goat (PE) in Yogyakarta, Indonesia. Biodiversitas 22: 3418-3422. Subclinical mastitis (SCM) in Ettawa Crossbred Goat (PE) is most frequently caused by staphylococci with a significant reduction in milk yield. The aim of this study is to determine antimicrobial resistance patterns of coagulase-negative staphylococci (CoNS) from PE goat SCM. A total of 36 CoNS isolates originating from PE goat SCM were collected in semisolid tube use in this study. All CoNS isolates were further examined for antimicrobial susceptibility testing by the Kirby-Bauer disc diffusion method. Antibiotic susceptibility of CoNS isolated samples according to Clinical Laboratory Standards Institute (CLSI). The CoNS isolates showed the highest resistance rate against sulfamethoxazole (65%), ampicillin (55.56%), penicillin (45%), cefoxitin (33.33%), erythromycin (25%), oxytetracycline (20%), tetracycline (15%), gentamicin and neomycin (11.11%), while oxacillin was sensitive. The highest of multiple antimicrobials resistance observed 15% in ampicillin, penicillin and tetracycline, then 5-10% in ampicillin, penicillin, erythromycin, tetracycline and oxytetracycline. The majority of CoNS in this study were resistant to sulfamethoxazole and then, followed by ampicillin, penicillin, cefoxitin, erythromycin, oxytetracycline, tetracycline, gentamicin and neomycin. In addition, most isolates were penicillin-resistant and multidrug-resistant (MDR).

Presence and antimicrobial resistance of coagulase-negative staphylococci isolated from animals in a Veterinary Teaching Hospital in Cyprus

Coagulase-negative staphylococci (CoNS) are a group of commensal microorganisms residing on the skin and mucous membranes of both humans and animals. Until recently, they have been regarded as non-pathogenic to livestock and companion animals, but since then, their clinical importance in veterinary medicine has increased with the discovery of their potential pathogenic roles in animals causing skin and soft tissue infections together with spontaneous abortions and mastitis. Scientific data concerning the presence of CoNS in North Cyprus are very limited. Therefore, the purpose of the study reported herein was to investigate the presence and antimicrobial resistance patterns of CoNS species isolated from various animals presented at the Veterinary Teaching Hospital in North Cyprus between July 2018 and 2019. Staphylococci were isolated from 37.0% (87/235) of the samples submitted, within which 60.9% (53/87) and 39.1% (34/87) were identified as coagulase-positive staphylococci (CoPS) and coagulase-negative staphylococci (CoNS), respectively. Among the CoNS, S. chromogenes was the most predominantly isolated species (14/34, 41.2%), followed by S. capitis (5/34, 14.7%) and S. simulans (4/34, 11.8%). Of these 34 CoNS, 24 (70.6%) and 10 (29.4%) were identified as MRCoNS and MSCoNS, respectively. The CoNS isolates showed relatively high levels of resistance towards amoxicillin/clavulanic acid (19/34, 55.9%), tetracycline (14/34, 41.2%) and penicillin (13/34, 38.2%). In conclusion, the presence of CoNS, especially MRCoNS, and the detection of multiple drug resistant (MDR) species with a high prevalence were regarded as being important since they might limit and have negative effects on the therapeutic treatment options of staphylococcal infections in animals, and might have both public and veterinary concerns.

Antimicrobial resistance in coagulase-negative staphylococci from Nigerian traditional fermented foods

BackgroundCoagulase-negative staphylococci have become increasingly recognized as the etiological agent of some infections. A significant characteristic of coagulase-negative staphylococci especially strains isolated from animals and clinical samples is their resistance to routinely used antibiotics although, resistant strains isolated from fermented foods have not been fully reported.MethodsA total of two hundred and fifty-five CoNS isolates were subjected to antimicrobial susceptibility test using the disc diffusion technique. The minimum inhibitory concentration of the isolates to the tested antibiotics was determined using the microbroth dilution method. Methicillin resistant strains were confirmed by detection of methicillin resistant genes (mecA) and also employing cefoxitin screening test.ResultsThe isolates were confirmed to be methicillin resistant by the detection of mecA genes and the cefoxitin screening test. The isolates demonstrated appreciable resistance to ampicillin (86.7%), sulfomethoxazole–trimethoprim (74.9%), amoxicillin–clavulanic acid (52.5%) and oxacillin (35.7%). Methicillin resistance was exhibited by 13 out of the 255 isolates although no mecA gene was detected. It was also observed that the methicillin resistant isolates were prevalent in these traditional foods; iru, kindirmo, nono and wara.ConclusionThis study has ameliorated the incidence of multiple antibiotic resistant coagulase-negative staphylococci in Nigerian fermented foods and if not tackled adequately might lead to horizontal transfer of antibiotic resistance from food to man.

Nosocomial coagulase-negative staphylococci in Belgrade: between Scylla and Charybdis.

Coagulase-negative staphylococci (CoNS) are increasingly resistant nosocomial pathogens. We aimed to analyze the prevalence of CoNS isolates in clinical settings, the evolution of antimicrobial resistance of CoNS, and antibiotic consumption in a hospital. This retrospective cohort study was carried out at a tertiary healthcare facility over 17 months. Identification of isolated cultures and antibiotic susceptibility testing were performed using the Vitek2 system. Of 1,217 isolates, 209 were obtained from 193 patients who had symptoms of nosocomial infections. Data were analyzed by descriptive statistics. Antibiotic consumption in the hospital is expressed in defined daily doses/100 patient days. Sixty-one percent of patients were admitted to the internal medicine ward, while others were admitted to the surgical ward. Forty-four percent of Gram-positive isolates were from wound swabs, and 26% were from blood. The predominant Gram-positive bacteria were CoNS. Antibiotic resistance of CoNS was highest against beta-lactam antibiotics, macrolides, and tetracyclines. Tigecycline, linezolid, and vancomycin produced the highest activities against CoNS in in vitro conditions, and consumption of linezolid and tigecycline increased in the same period. There are just a few remaining therapeutic options for the treatment of CoNS according to our results; vancomycin, linezolid, and tigecycline might be considered as first-choice antibiotics, but such a hypothesis should be supported with a pharmacoeconomic analysis. Unfortunately, novel antimicrobial agents are still unavailable and/or too expensive in developing countries. However, inappropriate use of those antibiotics may lead to the rapid development of resistant strains in the near future.

Antimicrobial susceptibility and body site distribution of community isolates of coagulase-negative staphylococci.

The primary aim of this study was to determine antimicrobial resistance in coagulase-negative staphylococci (CoNS) from healthy adults in the community. Healthy adults (n = 114) were swabbed on six body sites; both armpits, both knee pits and both sides of the groin. Species determination was performed using Matrix Assisted Laser Desorption Ionization - Time of Flight (MALDI-TOF) and susceptibility testing for 11 relevant antimicrobials was performed by the disc diffusion method and minimal inhibitory concentration gradient test. In total, 693 CoNS isolates were identified. Susceptibility testing was done on 386 isolates; one CoNS from each species found on each participant from the different body sites. The prevalence of antimicrobial resistance in the CoNS isolates were; erythromycin (24.6%), fusidic acid (19.9%), tetracycline (11.4%), clindamycin (7.8%), gentamicin (6.2%) and cefoxitin (4.1%). Multidrug resistance was observed in 5.2% of the isolates. Staphylococcus epidermidis and S. hominis were the first and second most prevalent species on all three body sites. We conclude that CoNS isolates from healthy adults in the community have a much lower prevalence of antimicrobial resistance than reported in nosocomial CoNS isolates. Still, we believe that levels of resistance in community CoNS should be monitored as the consumption of antimicrobials in primary care in Norway is increasing.

Phenotypical and Genotypical Antimicrobial Resistance of Coagulase-negative staphylococci Isolated from Cow Mastitis.

The objectives of this study were to determine the prevalence and antimicrobial resistance of coagulase-negative staphylococci (CNS) isolated from dairy cows with subclinical mastitis. Antimicrobial resistance in staphylococci were evaluated by breakpoint values specific to the species (EU-CAST). The presence of resistance-encoding genes was detected by multiplex PCR. A total of 191 CNS isolates were obtained. The CNS isolates were typically resistant to penicillin (67.4%), tetracyc-line (18.9%), and erythromycin (13.7%). CNS isolates (78.0%) were resistant to at least one antimicrobial compound, and 22.0% were multiresistant. The multiresistant isolates were predominantly Staphylococcus chromogenes (28.6%), Staphylococcus warneri (19%) and Staphylococcus haemolyticus (14.3%). According to MIC pattern data, multiresistant isolates showed the highest resistance (p<0.05) rates to penicillin (85.7%), tetracycline (66.7%), and erythromycin (48.2%), but all of them were sensitive to daptomycin, oxacillin, qiunupristin/dalfopristin, and vancomycin. S. chromogenes (9.5%), S. haemolyticus (4.8%), and S. capitis ss capitis (2.4%) strains were resistant to methicillin; their resistance to oxacillin and penicillin was more than 8 mg/l. A high rate of resistance to penicillin was linked to a blaZ gene found in 66.6% of the isolated multiresistant CNS strains. Resistance to tetracycline via the tetK (38.1%) gene and penicillin via the mecA (23.8%) gene were detected less frequently. Gene msrAB was responsible for macrolides and lincosamides resistance and detected in 28.6% of the CNS isolates. Antimicrobial resistance genes were identified more frequently in S. epidermidis, S. chromogenes, and S. warneri.

Species Identification and Antimicrobial Resistance of Coagulase‐Negative Staphylococci Isolated from the Meat of Sea Fish

Seventy-eight isolates of staphylococci obtained from the meat of Theragra chalcogramma, Scomber scombrus, and Clupea harengus were identified and tested in this study. 16S rDNA sequence specific for the genus Staphylococcus was detected in all isolates with the help of PCR method. All of 78 isolates were coagulase-negative, and DNAse activity was only confirmed in 4 of them. The following species of staphylococci were identified using MALDI-TOF mass spectrometry: S. warneri (52%), S. epidermidis (33%), S. haemolyticus (6.4%), S. pasteuri (3.8%), S. sciuri (1.2%), S. capitis (1.2%), and S. hominis (1.2%). Antimicrobial resistance to 7 antibiotics was determined in each isolate with the help of agar dilution method. In general, resistance against ampicillin was observed in majority of isolates (87%). On the contrary, the best sensitivity of CoNS was determined to gentamicin (96%). Only 1 S. warneri strain showed resistance to cefoxitin. Furthermore, 83% of staphylococcal isolates were simultaneously resistant to 2 or more antibiotics. This study confirmed the need of monitoring antimicrobial resistance in coagulase-negative staphylococci not only in the meat of slaughter animals but also in retail marine fish. The results showed that MALDI-TOF mass spectrometry is useful, accurate, and rapid method for species identification of food pathogens including Staphylococcus spp.

Identification and antibiotic susceptibility pattern of coagulase-negative staphylococci in various clinical specimens.

Antibiotic resistance is a global problem and is more prevalent in developing countries. Coagulase-negative staphylococci (CoNS) are recognized as important pathogen for nosocomial infections. This study was carried out to identify CoNS in various clinical specimens and to determine its antimicrobial susceptibility pattern. A total of 2989 specimens of blood, pus and wound swab were collected from wards, casualty, ICU and OPD, out of these, staphylococci were isolated in 1000 specimens, of which 381 were identified as CoNS. Culture, gram stain, catalase, coagulase test and antimicrobial susceptibility pattern were done according to clinical manual of microbiology. A total of fourteen antibiotics were used in this study. Susceptibility testing was done by Kirby Bauer disc diffusion technique. Antimicrobial resistance of CoNS were Oxacillin (70.3%), Amoxicillin (74.8%), Amoxicillin+clavulanate (32.8%), Ciprofloxacin (35.2%), Ofloxacin (33.6%), Ceftriaxone (30.4%), Erythromycin (58.3%), Clindamycin (16.3%), Daptomycin (42.5%), Kanamycin (52.2%), Fusidic acid (41.7%), Doxycycline (24.7%), Vancomycin (2.6%) and Linezolid (0.8%). Maximum Oxacillin resistance was between 80 to 90 percent in a group of patients having age of 45 to 65 years and those suffering from cancer or admitted in ICU. The study concluded that CoNS showed significant level of resistance against most of the widely used therapeutic agents.

Genetic characterization of antimicrobial resistance in coagulase-negative staphylococci from bovine mastitis milk

Coagulase-negative staphylococci (CNS; n=417) were isolated from bovine milk and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Nineteen different species were identified, and Staphylococcus xylosus, Staphylococcus chromogenes, Staphylococcus haemolyticus, and Staphylococcus sciuri were the most prevalent species. Resistance to oxacillin (47.0% of the isolates), fusidic acid (33.8%), tiamulin (31.9%), penicillin (23.3%), tetracycline (15.8%), streptomycin (9.6%), erythromycin (7.0%), sulfonamides (5%), trimethoprim (4.3%), clindamycin (3.4%), kanamycin (2.4%), and gentamicin (2.4%) was detected. Resistance to oxacillin was attributed to the mecA gene in 9.7% of the oxacillin-resistant isolates. The remaining oxacillin-resistant CNS did not contain the mecC gene or mecA1 promoter mutations. The mecA gene was detected in Staphylococcus fleurettii, Staphylococcus epidermidis, Staph. haemolyticus, and Staph. xylosus. Resistance to tetracycline was attributed to the presence of tet(K) and tet(L), penicillin resistance to blaZ, streptomycin resistance to str and ant(6)-Ia, and erythromycin resistance to erm(C), erm(B), and msr. Resistance to tiamulin and fusidic acid could not be attributed to an acquired resistance gene. In total, 15.1% of the CNS isolates were multidrug resistant (i.e., resistant to 2 or more antimicrobials). The remaining CNS isolates were susceptible to antimicrobials commonly used in mastitis treatment. Methicillin-resistant CNS isolates were diverse, as determined by mecA gene sequence analysis, staphylococcal cassette chromosome mec typing, and pulsed-field gel electrophoresis. Arginine catabolic mobile element types 1 and 3 were detected in both methicillin-resistant and methicillin-susceptible Staph. epidermidis and were associated with sequence types ST59 and ST111. Because this study revealed the presence of multidrug-resistant CNS in a heterogeneous CNS population, we recommend antibiogram analysis of CNS in persistent infections before treatment with antimicrobials.

Multidrug-resistant coagulase-negative Staphylococci in food animals

To study the antimicrobial resistance of coagulase-negative staphylococci (CoNS) in animals. In the present study, a total of 87 CoNS recovered from food animals were characterized by antimicrobial susceptibility testing, resistance gene identification and conjugation. Of the seven species studied, Staphylococcus lentus, Staphylococcus sciuri, Staphylococcus xylosus and Staphylococcus haemolyticus accounted for over 96% of the isolates. In addition to β-lactam resistance (100%), high percentages of CoNS were resistant to tetracycline (67·8%), erythromycin (36·7%), clindamycin (27·5%) and quinopristin/dalfopristin (14·9%). Importantly, 47 (54%) isolates were resistant to at least three antimicrobial classes, including six CoNS resistant to six antimicrobial classes. The common genes for the above-mentioned resistance phenotypes were mec(A), tet(M), erm(A) and vga(A)(LC) , which were identified from 68·7%, 61%, 56·2% and 69·2% of the isolates, respectively. tet(M) was conjugatively transferable from 10 tetracycline-resistant CoNS to a Enterococcus strain, underlining the potential of antimicrobial resistance transfer from Staphylococcus to the commensal bacteria in human. Multidrug resistance and resistance to non-β-lactam antimicrobials are common in CoNS in animals. The data improve our understanding on the extent to which CoNS contribute to the dissemination of antimicrobial resistance in the food production environment.

Changes of Antimicrobial Resistance among Coagulase-Negative Staphylococci Isolated in 8 Consecutive Years in the First Bethune Hospital

This study was to investigate the antimicrobial resistance of coagulase-negative Staphylococci isolated in 8 consecutive years in the First Bethune Hospital. Disk diffusion test was used to study the antimicrobial resistance. The data were analyzed by WHONET 5 software according to Clinical and Laboratory Standards Institute (CLSI). Most of 2484 strains of coagulase-negative Staphylococci were collected from blood 925 (37.2%), secretions 652 (26.2%) and urine 323 (13.0%) during the past 8 years. The rates of methicillin-resistant coagulase-negative Staphylococci (MRCNS) were between 79.4% and 81.5% during the past 8 years, respectively. In recent 8 years, the antimicrobial resistance of coagulase-negative Staphylococci had increased. Monitoring the antimicrobial resistance to coagulase-negatives Staphylococci should be strengthened. The change of the antimicrobial resistance should be investigated in order to direct rational drug usage in the clinic and prevent bacterial strain of drug resistance from being transmitted.

Antimicrobial resistance and genotypic characterization of coagulase-negative staphylococci over the dry period

Coagulase-negative staphylococci (CNS) have become the most frequently isolated organisms from bovine intramammary infections in recent years. While antimicrobial resistance (AR) is not considered a major problem among mastitis pathogens, concerns over emerging AR in general are increasing worldwide. Little information exists about the association between AR and one of the most common mastitis control measures, antibiotic dry cow therapy. The primary objective of the current study was to determine the prevalence of AR in CNS isolated before and after antimicrobial dry cow therapy. An additional objective was to genotypically characterize selected CNS isolates using pulsed-field gel electrophoresis (PFGE), to assess diversity and persistence of organisms over the dry period. Resistance against 10 antimicrobials was determined using a broth microdilution method and compared between CNS isolates collected at dry-off and at calving and from cows treated or not treated with intramammary antimicrobial products at dry-off (752 cows in total). Results suggested that increasing age of a cow and dry cow treatment when combined with high milk somatic cell count at dry-off and positive clinical mastitis history, were associated with increased AR to most beta-lactam antimicrobials and sulfadimethoxine. PFGE results suggested considerable diversity among the tested isolates as well as some clusters within cows and herds. PFGE would be useful in distinguishing between potentially persisting infections and cures and reinfections with different CNS strains.

Antimicrobial resistance of coagulase-negative staphylococci from bovine subclinical mastitis with particular reference to macrolide–lincosamide resistance phenotypes and genotypes

The aim of this study was to analyse coagulase-negative staphylococci (CoNS) for their resistance to antimicrobial agents approved for the control of pathogens involved in bovine mastitis, with particular reference to macrolide and/or lincosamide (ML) resistance and the resistance genes involved. A total of 298 CoNS collected between 2003 and 2005 in Germany from cases of subclinical mastitis in dairy cows were identified to the species level and investigated for their MICs by broth microdilution. ML-resistant isolates were subjected to plasmid profiling and electrotransformation experiments. The ML resistance genes were detected using PCR and hybridization. Selected PCR products were cloned and sequenced. The CoNS isolates used in this study showed a low level of resistance to all antimicrobial agents tested (0-7.4%) except ampicillin (18.1%). In the erythromycin-resistant and/or pirlimycin-resistant isolates, the ML resistance genes erm(B), erm(C), msr(A), mph(C) and lnu(A) were present, either alone or in different combinations. Isolates carrying erm methylase genes or the exporter gene msr(A) showed higher MICs than those harbouring only the genes mph(C) or lnu(A) coding for inactivating enzymes. Most of the ML resistance genes were found on plasmids. This is the first report of pirlimycin MICs for CoNS collected from cases of bovine subclinical mastitis in Germany. After 3-5 years of veterinary therapeutic use, pirlimycin resistance was rarely detected among CoNS. The finding that five different resistance genes--present in various combinations--were responsible for ML resistance underlines the heterogeneous character of this resistance trait.

Antimicrobial resistance of coagulase-negative staphylococci from a Kuwait hospital.

This study investigated the incidence of antimicrobial resistance in clinically significant coagulase-negative staphylococci at the Mubarak Al Kabeer Hospital, Kuwait. A total of 104 isolates of coagulase-negative staphylococci consisting of S. epidermidis (67), S. haemolyticus (16), S. saprophyticus (6), S. simulans (2), S. hominis (4), S. albus (2), S. sciuri (3), S. warneri (2), S. capitis (1), and S. xylosus (1) were isolated from clinical specimens over a 6-7 month period and tested for resistance to 22 antibacterial agents and the ability to produce slime. They were all susceptible to vancomycin and mupirocin but intermediate resistance to teicoplanin was detected in seven isolates: 83 and 47.7% were resistant to penicillin G and methicillin, respectively, 57% were resistant to gentamicin, 49.5% to erythromycin, 50.4% to tetracycline, and 52.3% to trimethoprim. Resistance to heavy metals and the nucleic-acid binding compound was also detected. More than half of S. epidermidis, S. saprophyticus, S. simulans, S. hominis, and all of S. haemolyticus were multiply resistant to three or more groups of antibiotics and there was a significant association between slime production and resistance to multiple antimicrobial agents in S. epidermidis. The results revealed a high level of resistance to commonly used agents.