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PubMed2002

Presence of mec genes and overproduction of beta-lactamase in the expression of low-level methicillin resistance among staphylococci.

Detection of methicillin-resistant staphylococci is critical for the management of infected patients in the hospital. A total of 55 nonreplicated clinical isolates of staphylococci (31 Staphylococcus aureus and 24 coagulase-negative staphylococci; CNS) collected during a one-year period and expressing low-level resistance to methicillin (oxacillin MIC of 2-4 mg/l for S. aureus and 0.5-4 mg/l for CNS) were studied. mec determinants and overproduction of beta-lactamase were investigated and pulsed-field gel electrophoresis (PFGE) was applied as a typing method. Twenty-four S. aureus isolates and 19 CNS carried the mecA gene. The presence of mecR1/mecI and blaR1/blaI genes correlated with the expression of low-level methicillin resistance in CNS. Four mecA-negative isolates (2 S. aureus and 2 CNS) overproduced beta-lactamase. PFGE revealed the presence of 2 major clonal types in mecA-positive S. aureus isolates, and 3 in CNS. Low-level methicillin resistance of staphylococci is correlated with the presence of the mecA gene and overproduction of beta-lactamase.

Bacterial Proteins↗
PubMed1967

Bacterial interference induced in embryonated eggs by staphylococci.

Studies of experimental infections in embryonated eggs demonstrated that prior allantoic infection with avirulent staphylococci afforded significant protection against subsequent challenge with virulent strains. All strains of coagulase-positive and coagulase-negative staphylococci tested that were relatively avirulent for embryonated eggs were capable of producing interference. The interference induced afforded protection not only against challenge with virulent staphylococci, but also against Diplococcus pneumoniae, Salmonella typhimurium, Escherichia coli, Proteus mirabilis, and one strain of influenza virus (A(2)J 305). Prior allantoic infection with avirulent staphylococci also protected against intravenous as well as allantoic infection with challenge strains.Interference required infection with viable bacteria. The onset of interference appeared within a few minutes after injection of the interfering strain, but was not maximal until 24 hours had elapsed between injection of the interfering and challenge strains. The protection afforded by the production of interference could not be overcome by increased inoculum size of the challenge strain and extended even to challenge with 10(9) bacteria. Studies of in vitro and in vivo growth of challenge strains in allantoic fluid demonstrated that some interfering strains inhibited growth of the challenge strains. Other strains produced interference without producing prolonged inhibition of the growth of challenge strains. Similarly, interference could not be attributed to attenuated virulence of the challenge organisms. All interfering strains studied produced enhanced bactericidal activity of whole blood from the affected embryos, but whether this affected leukocyte activity, opsonization, or other host defense mechanisms has yet to be determined.

Animals↗
PubMed2006

Prevalence of macrolide resistance genes among staphylococci in Cyprus.

The aims of the present study were to evaluate the frequency of macrolide-resistant staphylococci in Cyprus and to examine the phenotypic and genotypic characteristics of these isolates. Antimicrobial susceptibility testing was performed by broth microdilution method and the macrolide resistance determinants were detected by PCR. The relatedness among the isolates was examined by pulsed-field gel electrophoresis. Ninety-six (67.61%) of the 142 Staphylococcus aureus and 19 (59.4%) of the 32 coagulase-negative staphylococci were resistant to erythromycin. Among the 115 erythromycin-resistant staphylococci, 70 expressed the MLSB-inducible phenotype, 38 the MLSB-constitutive, and 7 the MS. The predominant genes associated with macrolide resistance were the ermA for S. aureus and the ermC for coagulase-negative staphylococci, detected in 90.62% and 47.37% of the isolates respectively. Dissemination of one clone carrying the ermA gene accounted for macrolide resistance in the majority of S. aureus isolates.

Anti-Bacterial Agents↗
PubMed1997

Methicillin-resistant staphylococci in clean surgery. Is there a role for prophylaxis?

The incidence of infection in clean surgery (i.e. surgery with no major contamination of the operative site) should be less than 2%, although the incidence of postoperative infections can be higher in patients with various risk factors (namely insertion of foreign bodies, a compromised immune status or prolonged duration of surgery). Although antibiotic prophylaxis has been shown to reduce the incidence of postoperative infections in clean surgery, there is still no consensus regarding its use in this area. However, for clean surgical procedures that involve implantation of foreign material, grafts or prosthetic devices, prophylaxis is well accepted and justifiable, since this practice is indicated when the benefits exceed the expected risks. Staphylococcus aureus and coagulase-negative staphylococci are responsible for 70 to 90% of wound infections in this type of surgery. First and second generation cephalosporins are considered the drugs of choice for surgical prophylaxis. Cefazolin and other cephalosporins have good tissue penetration but poor coverage against methicillin-resistant staphylococci. The frequency with which methicillin-resistant staphylococci have been recovered in nosocomial infections has increased steadily during recent years. This provides a rationale for the use of alternative antibiotics, such as the glycopeptides (vancomycin and teicoplanin), for prophylaxis in clean surgery in hospitals where the prevalence of methicillin-resistant staphylococci is high. The effectiveness and tolerability of teicoplanin as prophylaxis for orthopaedic surgery involving joint replacement were analysed in 4 randomised controlled trials. Two compared teicoplanin with cefamandole, while the others compared teicoplanin with either cefuroxime or cefazolin. The overall early wound infection rates (within 3 months) in these studies were 1.1% for teicoplanin and 1.7% for the comparator cephalosporin. The overall late infection rate was 0.2% for both treatment groups. Adverse events were attributed to the drug in 1% of patients in both treatment groups. Therefore, on the basis of these trials, single dose teicoplanin is as efficacious and as well tolerated as multiple dose cephalosporin regimens for prophylaxis in prosthetic joint surgery.

Anti-Bacterial Agents↗
PubMed2000

Methicillin-resistant coagulase-negative staphylococci isolated from healthy horses in Japan.

OBJECTIVE: To determine patterns of methicillin-resistant staphylococci isolated from apparently healthy horses. SAMPLE POPULATION: 44 horses from 8 riding clubs in Japan. PROCEDURE: Methicill in-resistant staphylococci were isolated from the skin or nares, using a selective medium containing a beta-(symboric) lactam antibiotic, ceftizoxime. Clonality of isolates was determined by use of pulsed-field gel electrophoresis. Detection of mecA, mecl, and mecR1 genes was accomplished by use of polymerase chain reactions. RESULT: Of the 44 horses, 13 (29.5%) yielded 15 isolates of methicillin-resistant staphylococci. The 15 isolates were identified as 6 species (Staphylococcus epidermidis, S lentus, S saprophyticus, S xylosus, S sciuri, and S haemolyticus). However, methicillin-resistant S aureus was seldom isolated. Each isolate contained the mecA gene and had a high resistance to beta-lactam antibiotics. Some isolates also were resistant to other antibiotics such as erythromycin and kanamycin. CONCLUSIONS AND CLINICAL RELEVANCE: Methicillin-resistant coagulase-negative staphylococci that were highly resistant to various antibiotics were isolated from apparently healthy horses in Japan. These organisms must be considered a potential threat to horses and veterinarians who care for them.

Animals↗
PubMed2006

Detection of biofilm formation among the clinical isolates of Staphylococci: an evaluation of three different screening methods.

PURPOSE: The purpose of this study was to evaluate three methods for detection of biofilm formation in staphylococci. METHODS: For detection of biofilm formation, 152 clinical isolates of Staphylococcus spp. were screened by tissue culture plate (TCP), Tube method (TM) and Congo red agar (CRA) method. RESULTS: Of the 152 Staphylococcus spp. 88(57.8%) displayed a biofilm-positive phenotype under the optimized conditions in the TCP method and strains were further classified as high 22 (14.47 %) and moderate 60 (39.4 %) while in 70 (46.0 %) isolates weak or no biofilm was detected. Though TM correlated well with the TCP test for 18 (11.8 %) strongly biofilm producing strains, weak producers were difficult to discriminate from biofilm negative isolates. Screening on CRA does not correlate well with either of the two methods for detecting biofilm formation in staphylococci. CONCLUSION: The TCP method was found to be most sensitive, accurate and reproducible screening method for detection of biofilm formation by staphylococci and has the advantage of being a quantitative model to study the adherence of staphylococci on biomedical devices.

Agar↗
PubMed1976

[Origin of the staphylococci in slaughtered poultry].

Studied were 382 coagulase-positive and 290 coagullase-negative Staphylococcus strains isolated from birds during their post-slaughter handling, from the vats for water cooling as well as from the women working on the slaughter-house conveyor. Studied were the phage behaviour, fibrinolysine production, the crystal-violet test and the type of hemolysines. It was established that the coagulase positive staphylococci were lysed slightly by the human and the bovine set of phages. The main sources of staphylococci of both human and bovine origin appeared to be the nasal cavity and the hands of workers. Evisceration proved to contribute to the tenfold higher count of staphylococci in the slaughtered birds. Most of the investigated strains of Staphilococcus aureus and Staphylococcus epidermidis differed from the human and the bovine type and were probably staphylococci of avian origin.

Abattoirs↗
PubMed1999

Methicillin resistance among staphylococci isolated from dogs.

OBJECTIVE: To determine whether methicillin-resistant staphylococci from dogs expressed the mecA gene and to determine what proportion of canine staphylococcal isolates positive for the mecA gene were resistant to oxacillin and other antibiotics. SAMPLE POPULATION: 25 methicillin-resistant (10 coagulase-positive and 15 coagulase-negative) and 15 methicillin-susceptible (8 coagulase-positive and 7 coagulase-negative) staphylococci isolated from dogs. PROCEDURE: All strains were tested for methicillin resistance by use of oxacillin agar screening and identified by use of standard techniques. Minimum inhibitory concentrations of 16 antibiotics were determined for all 40 isolates. A polymerase chain reaction method targeting a 533-basepair fragment of the mecA gene was used to detect mecA gene expression. RESULTS: 23 of the 25 methicillin-resistant isolates and none of the methicillin-susceptible isolates possessed the mecA gene. For 10 of 16 antibiotics, the proportion of mecA-positive isolates that were resistant or of intermediate susceptibility was significantly higher than the proportion of mecA-negative isolates that were resistant or of intermediate susceptibility. Only 1 methicillin-resistant coagulase-positive isolate was identified as Staphylococcus intermedius; the other 9 were identified as S. aureus. CONCLUSIONS AND CLINICAL RELEVANCE: Results confirm that staphylococci isolated from dogs may have methicillin resistance mediated by the mecA gene. Isolates positive for the mecA gene were more likely to be resistant to various antibiotics than were isolates negative for the mecA gene. Results suggest that in dogs, infections caused by staphylococci that have the mecA gene may be difficult to treat because of resistance to antibiotics.

Ampicillin Resistance↗
PubMed1999

Study of coagulase positive and negative Staphylococci in clinical samples.

A total of 983 patients samples (pus, urine, sputum, throat swabs, blood culture, CSF, vaginal swabs, ear swabs) were studied for a period of one year. The incidence of coagulase positive Staphylococci was highest in pus and the incidence of coagulase negative Staphylococci was highest in conjunctival swabs. Antibiotic Sensitivity pattern of routinely used antibiotics was studied. Coagulase positive Staphylococci was found to be most sensitive to Ciprofloxacin followed by Norfloxacin and Gentamycin. Coagulase negative Staphylococci showed maximum sensitivity to Ciprofloxacin followed by Norfloxacin and Chloramphenicol.

Animals↗
PubMed2000

Staphylococci: frequency of isolation and antibiotic susceptibility patterns in Jimma Hospital, south-west Ethiopia.

A total of 493 clinical and environmental specimens were collected from May 1997 to August 1998 from Jimma Hospital wards to determine the frequency of isolation and antimicrobial susceptibility patterns of staphylococci isolates. The specimens were obtained from pus and discharge (32%), blood (22%), urine (18%), nasal swabs (15%), and environmental samples (12%). Of the total 61 S. aureus isolates, 34 (55.7), 15 (24.6%), 8 (13.1%), and 4 (6.6%) were identified from pus and discharge, nasal swabs, blood, and environmental samples, respectively. Coagulase-negative staphylococci (CNS) were also isolated from nasal swabs (48.3%), pus and discharge (29.2%) and environmental samples (13.5%). Multiple antimicrobial resistance was commonly revealed by the S. aureus isolates (84%). Fifty eight (95%), 57 (93%), 43 (72%), and 30 (49%) of the S. aureus isolates were resistant to penicillin, ampicillin, tetracycline, and streptomycin, respectively. Methicillin resistance was also observed in 25 (43%) of the isolates. Similarly, coagulase-negative staphylococci isolates were multi-antimicrobial resistant (96%). The antimicrobial resistance profile of the CNS isolates observed was against penicillin (88%), ampicillin (87%), tetracycline (75%), and chloramphenicol (66%). By contrast, the S. aureus and CNS isolates appeared to be sensitive to gentamicin, kanamycin, and clindamycin. Options available to treat infections caused by multiple resistant staphylococci are limited especially in developing countries. Therefore, the ever growing emergence of antimicrobial resistance requires enhanced surveillance, prudent use of existing antimicrobial drugs, increased emphasis on infection control, and hygienic practices.

Cross Infection↗
PubMed1999

The prevalence of aminoglycoside resistance and corresponding resistance genes in clinical isolates of staphylococci from 19 European hospitals.

Aminoglycosides still play an important role in antistaphylococcal therapies, although emerging resistance amongst staphylococci is widespread. To further our understanding of the prevalence of aminoglycoside resistance in Europe, we tested 699 and 249 consecutive unrelated clinical isolates of Staphylococcus aureus and coagulase-negative staphylococci (CNS), respectively, from the SENTRY Antimicrobial Surveillance Program, for susceptibility to gentamicin, tobramycin, kanamycin and streptomycin, and examined the relationship between susceptibility to these antimicrobials and susceptibility to methicillin. Three hundred and sixty-three staphylococcal isolates demonstrated resistance to at least one of the aminoglycosides tested; all of these isolates were screened for the presence of aac(6')-Ie + aph(2"), ant(4')-Ia and aph(3')-IIIa, the genes encoding the most clinically relevant aminoglycoside-modifying enzymes. S. aureus isolates derived from hospital-acquired pneumonia tended to be more resistant to aminoglycosides and methicillin than isolates from blood or wound infections. In S. aureus, resistance to aminoglycosides was closely associated with methicillin resistance. Susceptibility of S. aureus to gentamicin has decreased by 9% from previous European studies to a current level of 77%, while susceptibility of CNS, currently at 67%, has increased by 21%. Geographical variation occurred, correlating with methicillin resistance, although intra-country variation was considerable. aac(6')-Ie + aph(2"), ant(4')-Ia and aph(3')-IIIa were found throughout Europe in 68%, 48% and 14% respectively of staphylococci resistant to at least one aminoglycoside. aph(3')-IIIa was considerably more common in methicillin-susceptible S. aureus and CNS isolates; the reverse was true for the other two resistance genes. The prevalence of ant(4')-Ia and aph(3')-IIIa genes in aminoglycoside-resistant staphylococci was significantly greater than that reported in previous European studies.

Acetyltransferases↗
PubMed2000

[Susceptibility to selected coagulase-negative chemotherapeutic agents of methicillin resistant staphylococci isolated from clinical materials in 1997-1998].

The study was aimed at assessment of the sensitivity of methicillin-resistant coagulase-negative staphylococci isolated from clinical material in 1997/1998 to selected chemotherapeutic agents. The investigated material comprised 96 methicillin-resistant coagulase-negative staphylococci from hospital and ambulatory infections isolated during the period from April 1997 to May 1998. Species affiliation was determined by classical identification methods and commercial diagnostic tests for identification of staphylococci. Methicillin resistance was determined by agar disk-diffusion method and screening. Sensitivity to chemotherapeutics was determined by agar disk-diffusion method and agar dilution methods. All the investigated strains were sensitive to nitrofurantoin, furazolidone and vancomycin. To teicoplanin--the second glycopeptide antibiotic--84% strains were sensitive, whereas the percentages of resistant and moderately sensitive strains amounted to 5.2% and 10.4%, respectively. 85% and 82% of coagulase-negative staphylococcal strains were sensitive to fusidic acid and mupirocin. Considerable differences were noted with respect to sensitivity to aminoglycoside group antibiotics. About 35% of strains were sensitive to gentamicin, and 90% sensitive to netilmicin. Ca. 40% of coagulase-negative staphylococci were resistant both to cotrimoxazole and trimethoprim, which, in view of 98% resistance to the second component of cotrimoxazole, may be associated with the activity of only one of the components of the drug--trimethoprim.

Coagulase↗
PubMed1975

[Characteristics of staphylococci isolated from slaughtered birds].

Studied were some biologic properties of 76 strains of staphylococci isolated from slaughtered chickens. It was established that coagulase-positive staphylococci posses the basic properties of Staphylococcus aureus--they ferment mannite and glucose, can produce phosphatase, desoxyribonuclease, and hemolysines. By some of their properties -- type of hemolysines, coagulation of sheep and bovine plasta, production of fibrolysines, type of colonies as established by means of the crystal-violet test -- staphylococcus cultures isolated from slaughtered poultry differ from isolated from human beings, cattle and sheep. Besides, the studied strains of Staphylococcus aureus are lysed to a very low percent by the phages of the bovine set and the phages for typing the staphylococci, isolated from humans. It may be assumed that the staphylococci occasionally found in birds can form a special group that require further studies.

Animals↗
PubMed2001

In vitro activity of levofloxacin against coagulase-positive and -negative staphylococci.

The in vitro activity of levofloxacin compared with that of ciprofloxacin, ofloxacin and norfloxacin were examined by conventional in vitro tests against 150 clinical isolates of staphylococci, subdivided according to species and susceptibility to methicillin. Although the minimum inhibitory concentrations (MICs) of all quinolones were highest in methicillin-resistant Staphylococcus aureus strains, the activity of levofloxacin was almost complete in methicillin-resistant S. epidermidis and methicillin-resistant S. haemolyticus when compared with ciprofloxacin and ofloxacin, which showed more than 30% resistance. Methicillin-susceptible S. aureus and S. epidermidis strains were susceptible to all quinolones with few differences between the antibiotics tested. The minimal bactericidal activity of levofloxacin was within the double dilution range of MIC values for all strains tested, demonstrating its potent role against staphylococci. In time-kill studies, levofloxacin exerted bactericidal activity within 3 h against all staphylococci. These in vitro results suggest that levofloxacin is a potent fluoroquinolone against coagulase-negative staphylococci and that it is both methicillin-susceptible and resistant. Further studies are necessary to determine the role of this drug in the treatment of infections sustained by these microorganisms.

Anti-Infective Agents↗
PubMed2001

Coagulase-negative staphylococci. Pathogens have major role in nosocomial infections.

Coagulase-negative staphylococci live naturally on the skin and mucous membranes of humans and are therefore often found in clinical specimens. Distinguishing clinically significant, pathogenic strains from contaminant strains is one of the major challenges facing clinical microbiology laboratories. S epidermidis and other novobiocin-susceptible coagulase-negative staphylococci have emerged as a major cause of nosocomial infections, particularly of nosocomial bacteremia in immunocompromised patients. S epidermidis also is common in injecting drug users, who are particularly susceptible to right-sided endocarditis, and--most important--in patients with such indwelling foreign bodies as intravenous catheters. Depending on the kind of device and its insertion site, different infection syndromes generate a variety of clinical presentations. In these patients, the host defense mechanisms often seem unable to handle the infection and, in particular, to eliminate the staphylococci from the infected device because of a biofilm on the foreign body surface. S saprophyticus, the most commonly isolated bacterium of the novobiocin-resistant coagulase-negative staphylococci, is a common pathogen of the urogenital tract; it generally infects immunocompetent patients, particularly young, sexually active men and women.

Coagulase↗
PubMed2001

Staphylococci in orthopaedic surgical wounds.

From 50 infected surgical wounds of orthopaedic patients, 43 (86%) staphylococcal strains were isolated. 34 of all these staphylococci belonged to Staphylococcus aureus species (i.e. 68 % of all isolates from surgical wounds; 79% of staphylococcal isolates); 9 were coagulase-negative staphylococci (i.e. 21% of all isolates from surgical wounds; 18% of staphylococcal isolates). Among microorganisms isolated from the wounds we also found 2 (4%) of the Enterobacteriaceae family; 2 (4%) of the Pseudomonas genus; 3 (6%) of the Streptococcus genus. Thus, orthopaedic surgical wounds were infected by staphylococci (mainly S. aureus) more frequently than by other micro-organisms. All the staphylococcal strains were screened for methicillin resistance by agar disk diffusion testing and for the presence of mecA gene responsible for methicillin resistance by PCR. 32% of the S. aureus and 33% of the S. epidermidis strains resulted methicillin resistant and mecA-positive. The data confirm the diffusion of methicillin resistant S. aureus in surgical site infections and shows that the so-called "new pathogens", i.e. S. epidermidis and other coagulase-negative staphylococci, also exhibit a frequent and hazardous methicillin-resisting ability.

Humans↗
PubMed2002

[Antibiotic resistance of staphylococci isolated from outpatients].

The aim of the study was to determine susceptibility of 587 strains of S. aureus and 85 strains of coagulase-negative staphylococci isolated from outpatients in Poznań to co-trimoxazole, amoxycillin/clavulanic acid, erythromycin, gentamycin, doxycycline, ampicillin, oxacillin, cephradine, clindamycin and neomycin. Also methicillin-resistant strains were determined as well as strains ability to produce beta-lactamases. Susceptibility testing and examination of methicillin-resistant strains were performed by the disc diffusion techniques according to recommendation of NCCLS. Methicillin-resistant strains were additionally examined to their sensitivity to vankomycin and teicoplanin. beta-lactamase production was detected using nitrocefin impregnated discs and iodometric method. Amoxacillin/clavulanic acid, gentamycin, co-trimoxazole, cephradin, oxacillin and clindamycin occurred to be very active against both, S. aureus and coagulase-negative staphylococci. 84.7% to 100% of examined strains were sensitive to these drugs. Doxycyclin, erythromycin and ampicillin were less effective. Nine strains (1.5%) of 587 strains of S. aureus as well as 7 strains (8.7%) of coagulase-negative staphylococci were methicillin-resistant. All of methicillin-resistant strains were sensitive to vancomycin and teicoplanin. More than 75% of S. aureus and close to 50% of coagulase-negative staphylococci were able to produce beta-lactamases.

Drug Resistance↗
PubMed1978

Phage typing of coagulase-negative staphylococci.

218 bovine and 116 human strains of coagulase-negative staphylococci and 46 bovine Staphylococcus aureus strains were typed with the Verhoef-phage set for human staphylococci and the Holmberg-set for bovine staphylococci. 22.5% of the bovine strains were lysed by the bovine phages and only 3.2% by the human phages. None of the bovine Staph. aureus strains could be typed. 21% of the human strains tested were lysed by the human phages and only 5.2% by the bovine phages. These results clearly demonstrate the need of separate phage sets for the typing of bovine and human coagulase-negative staphylococci.

Animals↗