Aminoglycoside resistance in members of the Staphylococcus sciuri group

This study investigated the prevalence of aminoglycoside resistance and genes encoding aminoglycoside-modifying enzymes in members of the Staphylococcus sciuri group. A total of 304 S. sciuri group member isolates (284 S. sciuri, 12 S. lentus, and 8 S. vitulinus) from humans (n = 34), animals (n = 133), and environmental sources (n = 137; out-hospital and hospital environment, food) were examined for their susceptibility to amikacin, gentamicin, isepamicin, kanamycin, neomycin, netilmicin, sisomicin, streptomycin, and tobramycin. The overall prevalence of resistance to aminoglycosides was low at 12.1%. Resistance to single aminoglycosides ranged from 0% to 7.2%. The aac(6')-Ie/aph(2"), ant(4')-Ia, and aph(3')-IIIa genes, either alone or in combination, were found in 16 out of 19 isolates showing resistance to nonstreptomycin aminoglycosides. Among the 22 isolates that showed resistance to streptomycin, the genes str and ant(6)-Ia were identified in 18 and 4 isolates, respectively.     

Identification and characterization of clinical isolates of members of the Staphylococcus sciuri group

A total of 28 staphylococcal isolates from human clinical specimens belonging to the Staphylococcus sciuri group were identified and characterized. The API Staph and ID32 STAPH correctly identified S. sciuri and S. lentus but not S. vitulinus strains. Identification to the subspecies level was possible only by a PCR-based method.     

Resistance to macrolides, lincosamides, streptogramins, and linezolid among members of the Staphylococcus sciuri group

This study aimed to characterize the resistance profiles of the Staphylococcus sciuri group members to macrolides, lincosamides, streptogramins (MLS antibiotics), and linezolid upon analysis of large series of isolates that included 162 S. sciuri isolates, nine S. lentus, and one S. vitulinus. The evaluation of their susceptibility by disk diffusion and agar dilution methods, along with PCR detection of the resistance genes erm(A), erm(B), erm(C), mef(A), lnu(A), and lnu(B), were performed. Resistance to macrolides was detected in 10 (5.8%) tested strains, with three and six isolates exhibiting constitutive and inducible MLS(B) resistance phenotypes, respectively. Resistance mediated by active efflux was detected in one strain. The presence of genes conferring resistance, namely erm(B) or erm(C), was detected in two strains. All tested strains were susceptible to pristinamycin and linezolid. Of 172 tested strains, 70.9% were resistant and 26.2% had intermediary resistance to lincomycin, whereas 1.7% were resistant and 50% had intermediary resistance to clindamycin. The lnu(A) gene was detected in two strains only. The great majority of the tested S. sciuri strains (153 out of 162; 94.4%) presumably exhibited LS(A) phenotype because they did not carry lnu genes nor displayed constitutive MLSB resistance, but still showed intermediate resistance or resistance to lincomycin (MICs of 4, 8, 16, and 32 microg/ml). The results obtained indicate that S. sciuri may be naturally resistant to lincomycin. Expression of a novel type of inducible resistance to lincosamides, induced by erythromycin in erythromycinsusceptible strains, was observed in the S. sciuri group isolates.     

Isolation of Corynebacterium group D2 from two dogs with urinary tract infections.

Corynebacterium group D2 was isolated from two dogs with urinary tract infections. The isolates were resistant in vitro to all tested antibacterial drugs except vancomycin. One dog was successfully treated with this antibiotic, while the other died before treatment could be initiated.     

Frequency of isolation of Staphylococcus lugdunensis in consecutive urine cultures and relationship to urinary tract infection

Recent reports associate Staphylococcus lugdunensis with severe infection in humans. The frequency of this microorganism in urine cultures is unknown. Five hundred isolates of coagulase-negative staphylococci (CoNS) were recovered from 4,652 consecutive urine specimens submitted for culture to the Mayo Clinic Microbiology Laboratory. Thirty-one (6%) of 500 isolates of CoNS were identified as S. lugdunensis. In no case was S. lugdunensis isolated in pure culture; 29 (94%) of 31 S. lugdunensis isolates were part of mixed nonpathogenic flora. Medical records were reviewed for 30 of the 31 patients from whom these 31 isolates were isolated. Twenty-one (70%) of the 30 evaluable patients were not treated with antibiotics; the remaining 9 (30%) of 30 patients were treated with antibiotics that may be effective against S. lugdunensis. S. lugdunensis may be an unrecognized yet infrequent cause of urinary tract infection.     

Evaluation of phenotypic and molecular methods for detection of oxacillin resistance in members of the Staphylococcus sciuri group

In this paper we report on an experimental evaluation of phenotypic and molecular methods as means for the detection of oxacillin resistance in members of the Staphylococcus sciuri group. A total of 109 S. sciuri group member isolates (92 S. sciuri isolates, 9 S. lentus isolates, and 8 S. vitulinus isolates) were tested by the disk diffusion method, the agar dilution method, the oxacillin salt-agar screening method, slide latex agglutination for PBP 2a, and PCR assay for mecA as the reference method. The mecA gene was detected in 29 S. sciuri isolates, and the true-positive and true-negative results of the other tests were defined on the basis of the presence or the absence of the mecA gene. For the different methods evaluated, the sensitivities and specificities were as follows: for the disk diffusion test with a 1-microg oxacillin disk, 100% and 55.9%, respectively; for the disk diffusion test with a 30-mug cefoxitin disk, 93.5% and 100%, respectively; for the agar dilution method, 100% and 50%, respectively; for the oxacillin salt-agar screen test (with 6 microg of oxacillin per ml and 4% NaCl) 100% and 100%, respectively; and for the slide latex agglutination test for PBP 2a, 100% and 100%, respectively. The disk diffusion test with various beta-lactam antibiotics was performed to evaluate their use for the prediction of oxacillin resistance. The results indicate that meropenem, cefazolin, cefamandole, cefuroxime, cefotetan, cefoperazone, cefotaxime, ceftriaxone, moxalactam, cefaclor, and cefprozil may be used as surrogate markers of oxacillin resistance, although further studies of their use for the detection of oxacillin resistance are required.     

Isolation and molecular characterization of Staphylococcus sciuri in the hospital environment

Staphylococcus sciuri is a principally animal-associated bacterial species, but its clinical relevance for humans is increasing. Our study aimed to provide the first insight into the prevalence of this bacterium in a hospital environment. A 3-month surveillance was conducted in a hospital located in Belgrade, Serbia, and 1,028 samples taken from hands of medical personnel, medical devices, and various hospital surfaces were screened for S. sciuri presence. In total, 108 isolates were obtained, which resulted in a relatively high rate of colonization (10.5%). These isolates, along with 7 S. sciuri strains previously isolated in the same hospital (n = 115), were phenotypically and genotypically characterized. Antimicrobial susceptibility testing revealed that 73% of the strains were resistant to one or more antibiotics, with 4.3% strains displaying multiresistance. Examination of 16S-23S ribosomal DNA intergenic spacer length polymorphism identified the strains at the subspecies level, and 74 (64.3%) strains of S. sciuri subsp. sciuri, 37 (32.2%) strains of S. sciuri subsp. rodentium, and 4 (3.5%) strains of S. sciuri subsp. carnaticus were established. Pulsed-field gel electrophoresis (PFGE) analysis showed 21 distinct pulsotypes, including 17 main types and 4 subtypes. One dominant cluster with 62 strains was found, while 19 (90.5%) of the PFGE types and subtypes identified had 5 or fewer strains. The predominance of small PFGE clusters suggests that the ubiquitous presence of S. sciuri in the outside environment presents the continuous source for colonization of the hospital environment. The presence of one dominant PFGE cluster of strains indicates that some S. sciuri strains may be capable for adaptation to hospital environment conditions and continuous existence in this environment.     

Staphylococcus saprophyticus as a cause of urinary tract infections.

Our objectives in this study were to elucidate various aspects of the epidemiology of Staphylococcus saprophyticus. This organism was isolated from the midstream urine specimens of 7.5% of 145 college women with frequency and urgency of urination and dysuria, but from only 0.07% of 14,835 urine specimens from adult inpatients at the Victoria General Hospital. It was found to be part of the urethral flora of only 2% of healthy women. Other staphylococci which formed part of the urethral flora of 100 healthy women included S. epidermidis (59 women), S. hominis (15 women), S. haemolyticus (13 women), S. warneri (9 women), and S. aureus (6 women). Finally, we determined that resistance to the 5-micrograms novobiocin disk has a 93% positive predictive accuracy as a presumptive test for S. saprophyticus.     

Quantitative and bacteriological studies of urine specimens from canine and feline urinary tract infections.

The most prevalent microorganisms isolated from urine specimens of dogs (385) and cats (132) with clinical signs of urinary tract infections were Escherichia coli, Proteus spp., and Staphylococcus aureus. The results of quantitative urine-culturing methods showed 48.6% of the canine and 12.1% of the feline specimens had more than 10(5) organisms per ml of urine. The bacteria isolated appear to have a greater resistance to antibacterial agents than previously reported.     

False-positive Chlamydiazyme results during urine sediment analysis due to bacterial urinary tract infections.

Our study examined whether urinary tract infections (UTIs) would cause false-positive results when urine sediment was tested with the Chlamydiazyme (CZ) system. Thirty-six infected urine samples and fifteen controls were studied. All controls were negative. Forty-seven percent of Escherichia coli UTIs (n = 30) and 100% of Klebsiella pneumoniae UTIs (n = 4) were positive on CZ testing of urine sediment. Nine E. coli UTIs positive by CZ were negative by direct fluorescent-antibody staining. When suspensions of the pure cultures were analyzed, 47% of E. coli and 100% of K. pneumoniae samples were CZ positive. False-positive results were not related to organism biotype or urine characteristics, including pH, specific gravity, and leukocyte count. We conclude that the presence of a UTI and also bacterial contamination must be ruled out prior to urine sediment testing.     

Survey of genes encoding staphylococcal enterotoxins, toxic shock syndrome toxin 1, and exfoliative toxins in members of the Staphylococcus sciuri group

Genes encoding staphylococcal enterotoxins (sea to see, seg, and seh), toxic shock syndrome toxin 1 (tst), and exfoliative toxins (eta and etb) were not detected in a large panel of 48 Staphylococcus sciuri group isolates tested. This strongly suggests that production of the staphylococcal exotoxins by these bacteria is highly unlikely.     

Classification of Staphylococcus albus strains isolated from the urinary tract

Strains of Gram-positive, catalase-positive, coagulase-negative cocci isolated from urine specimens were classified by the system of Baird-Parker (1963). Urinary infections attributed to instrumentation or pathological abnormalities of the urinary tract were caused almost entirely by various Staphylococcus subgroups. These showed a wide range of antibiotic sensitivities, unrelated to subgroups and not obviously related to previous chemotherapy. Attacks of cystitis occurring in otherwise healthy women were usually caused by Micrococcus subgroup 3 strains.     

Molecular characterization of Staphylococcus sciuri strains isolated from humans

We previously characterized over 100 Staphylococcus sciuri isolates, mainly of animal origin, and found that they all carried a genetic element (S. sciuri mecA) closely related to the mecA gene of methicillin-resistant Staphylococcus aureus (MRSA) strains. We also found a few isolates that carried a second copy of the gene, identical to MRSA mecA. In this work, we analyzed a collection of 28 S. sciuri strains isolated from both healthy and hospitalized individuals. This was a relatively heterogeneous group, as inferred from the different sources, places, and dates of isolation and as confirmed by pulsed-field gel electrophoresis analysis. All strains carried the S. sciuri mecA copy, sustaining our previous proposal that this element belongs to the genetic background of S. sciuri. Moreover, 46% of the strains also carried the MRSA mecA copy. Only these strains showed significant levels of resistance to beta-lactams. Strikingly, the majority of the strains carrying the additional MRSA mecA copy were obtained from healthy individuals in an antibiotic-free environment. Most of the 28 strains were resistant to penicillin, intermediately resistant to clindamycin, and susceptible to tetracycline, erythromycin, and gentamicin. Resistance to these last three antibiotics was found in some strains only. The findings reported in this work confirmed the role of S. sciuri in the evolution of the mechanism of resistance to methicillin in staphylococci and suggested that this species (like the pathogenic staphylococci) may accumulate resistance markers for several classes of antibiotics.     

Association between urine pH and common uropathogens in children with urinary tract infections

Background/PurposeUrinary tract infections (UTIs) are one of the most common pediatric infections. Our objective in this study is to investigate the association between urine pH and uropathogens in pediatric patients.MethodsThe source population comprised 26 066 paired urinalysis (UA) and urine culture (UC) samples obtained from pediatric patients. We classified the paired UA–UC samples into UTI positive (N = 6348) and UTI negative (N = 19 718) according to the colony forming units corresponding to the sampling source. We included UTI positive patients with infection caused by a single species of pathogen (N = 5201) and frequency matched them with UTI negative patients (N = 4729) by age, sex, sampling source, and visit type.ResultsThis study included 5201 pediatric patients with UTIs and found that urine with Proteus mirabilis or Pseudomonas aeruginosa demonstrated the least acidic pH (mean pH = 6.72 and 6.62, respectively), whereas urine with Escherichia coli or Klebsiella pneumoniae exhibited the most acidic pH (pH = 6.21 and 6.18). After stratifying the UTI samples by their pH range (<6, 6–6.9, 7–7.9, and ≥8). The prevalence of P. mirabilis increased significantly across increasing pH categories.ConclusionThis research is the first epidemiological study that linked urine pH to specific uropathogens in a pediatric population. Both urine pH and age are associated with certain causative uropathogens. Urine that grew P. mirabilis or P. aeruginosa had the least acidic pH. Additional studies should validate the role of urine pH in predicting uropathogens and UTI.     

Elevated interleukin-8 levels in the urine of patients with urinary tract infections.

Pyuria is one of the main features of urinary tract infections (UTI). Nevertheless, the mechanism of polymorphonuclear leukocyte (PMN) recruitment into the urine remains to be investigated. We examined whether interleukin-8 (IL-8), a potent neutrophil chemoattractant and activator, was involved in pyuria seen in UTI. Of 113 patients, 112 had elevated levels of IL-8 in their urine (1,078.0 +/- 181.5 pg/ml), regardless of whether they had an upper or lower UTI; this was in contrast to undetectable levels (less than 16 pg/ml) in the urine of all of the 20 normal individuals and 74 control patients without UTI. A concomitant study revealed increases in urine IL-6, but not IL-1 beta, and tumor necrosis factor alpha levels in patients with UTI. In addition to gram-negative bacteria, a wide spectrum of microorganisms was capable of inducing IL-8 production in urine. Local production of IL-8 in the urinary tract was suggested by a urine IL-8 level that was higher than the paired serum IL-8 level. The urine IL-8 level correlated with the number of PMN in the urine, and an average of half of the chemotactic activity in urine from patients with UTI could be abrogated by anti-IL-8 antibody treatment in vitro. Furthermore, urine IL-8 purified from patients was bioactive and showed multiple forms on immunoblotting analysis. This is the first documentation of IL-8 in the urine of patients with UTI, and these results imply that IL-8 is involved in inducing PMN migration into the urinary tract.     

Salmonella infections of the urinary tract

Infection of the urinary tract is a relatively rare manifestation of salmonellosis, most often seen in elderly and debilitated patients. The literature is reviewed briefly with a focus on the mechanisms whereby the urinary tract may be involved in salmonellosis, i.e. ascending or haematogenous invasion of the urinary tract. Predisposing factors, clinical course, and recommendations for follow-up of patients are commented on. Ten cases of urinary tract infections caused by various Salmonellae illustrate the nosology.     

Isolation and comparison of Escherichia coli strains from canine and human patients with urinary tract infections.

We analyzed Escherichia coli strains isolated from dogs with urinary tract infections (UTIs) in an attempt to determine if any of these strains were similar to E. coli isolated from humans with UTIs. Using genotypic and phenotypic traits, we identified four canine and six human E. coli UTI isolates that all appeared to be closely related or identical. All isolates shared similar DNA sequences for pyelonephritis-associated pili (pap), alpha-hemolysin (hly), and insertion sequence 5 (IS5), on the basis of Southern blot analysis. Similar outer membrane protein, pilin, and plasmid profiles were obtained for each of the isolates, although minor heterogeneity was observed. All of these isolates expressed a neuraminidase-sensitive binding phenotype in contrast to the majority of human isolates, which are known to express an adhesin that recognizes terminal digalactoside residues. Taken together, these results suggest that similar E. coli uropathogens may be capable of infecting both dogs and humans. To determine if the intestinal tracts of dogs were a reservoir for uropathogenic E. coli, eight paired rectal and urine pap+ E. coli strains were cultured from dogs with UTIs. By using the same genotypic and phenotypic criteria described above as a basis for strain identity, seven of eight urine-rectal pairs showed intrapair identity. However, each urine-rectal pair displayed a unique overall profile and could be distinguished from the other pairs. We conclude that the uropathogen colonizing the bladders of dog can also be the predominant strain colonizing the intestinal tracts.     

Identification of coagulase-negative Staphylococci isolated from urinary tract infections

Coagulase-negative Staphylococci isolated from urinary tract infections were identified using the API Staph-Ident System. Organisms were excluded if there was no sign of pyuria or if normal urethral flora was present in significant amounts. While Staphylococcus saprophyticus and Staphylococcus epidermidis accounted for 81% of the isolates from females, 87% of isolates from males were S. epidermidis, Staphylococcus warneri, or Staphylococcus haemolyticus. The females fell into two main age groups, those with infections due to S. saprophyticus (mean age 25 years) and those due to other Staphylococci (mean age 40-49 years). All males were in a single age group (mean age 70-74 years) irrespective of the infecting agent. In males, S. warneri was associated with cellular changes in the bladder. No similar association was apparent with the other organisms. The results suggest that, apart from S. saprophyticus, three species of Staphylococcus (S. epidermidis, S. haemolyticus, S. warneri) account for most urinary tract infections, irrespective of the sex of the patient.