Species differences in susceptibilities of Proteeae spp. to six cephalosporins and three aminoglycosides

Activities of oral antibiotics on Providencia strains isolated from institutionalized elderly patients with urinary tract infections

More than 250 Providencia strains isolated from the urine of institutionalized elderly patients were tested against cefaclor, cefuroxime, cefetamet, cefpodoxime, ciprofloxacin, and amoxicillin-clavulanic acid. Our results confirm the strong activities of expanded-spectrum oral cephalosporins against Providencia isolates, f1p4ell as the marked differences in susceptibilities among accurately identified Providencia species.

A species-specific DNA probe for Providencia stuartii identification

A DNA probe is described that can be used for identification of Providencia stuartii by means of filter hybridization assays. The probe, which is a fragment of the P. stuartii phoN gene coding for an acid phosphatase, appeared to be able to recognize only P. stuartii strains in slot-blot hybridization experiments performed with total DNA extracted from 545 strains of 64 different Gram-negative bacterial species, including all the major representatives of the family Enterobacteriaceae. Owing to the problems that may be often encountered for correct identification of P. stuartii at the species level when using commercial identification systems, this probe may result useful for fast and reliable identification of P. stuartii strains for taxonomical, epidemiological and diagnostic studies.

Modified MacConkey medium which allows simple and reliable identification of Providencia stuartii

This work describes a modified MacConkey medium (MCP medium) enabling the simple identification of Providencia stuartii, an emerging nosocomial pathogen. A total of 813 strains, belonging to the families Enterobacteriaceae and Pseudomonadaceae, were tested on MCP medium; all P. stuartii strains were phosphatase positive, as were 97.5% of Morganella morganii strains, in contrast with all other tested organisms. A simple discriminating test, such as the ornithine or citrate test, allowed identification of strains of these species. We have also compared the reliabilities of P. stuartii identification by commercial kits (API 20E system) by using a standard MacConkey or MCP medium. Sixteen and three-tenths percent of P. stuartii strains were misidentified by using the former procedure, while with the latter all strains were correctly identified. Finally, the MCP medium was used over a 6-month period in our routine clinical laboratory. Of a total of 1,278 seeded urine samples from elderly patients, we isolated 103 P. stuartii strains which were all correctly identified by coupling MCP medium and the API 20E system. Seventeen and one-half percent of these strains were misidentified when the API 20E system was used in combination with standard MacConkey medium.

Use of a novel phosphatase test for simplified identification of species of the tribe Proteeae

Phosphatase activity of 334 isolates of the tribe Proteeae carefully identified to species level has been evaluated by using both a number of conventional tests and three versions of the novel methyl green-phenolphthalein (MGP) method (G. Satta. R. Pompei, G. Grazi, and G. Cornaglia, J. Clin. Microbiol. 26:2637-2641, 1988). We found that the different species of Proteeae show different and easily distinguishable. behaviors by the MGP method, while all of them behave in a uniform way in the conventional tests. On studying the mechanism underlying these different behaviors, we found that the phosphatase activity of Morganella morganii and Providencia stuartii is higher than that of all other members of the family Enterobacteriaceae. Furthermore, we found that all P. stuartii strains display the property (shared by virtually none of the other species of Enterobacteriaceae) of excreting significant amounts of phosphatase. This extracellular activity is reliably detected by the MGP method but not by conventional tests. Finally, by exploiting the peculiar phosphatase activity of this tribe, as revealed by the MGP method, we devised a simple scheme for routine identification of the species of Proteeae and evaluated its reliability by comparing it with three commonly used commercial kits. The new scheme proved much simpler, but also more reliable, since identifications obtained by this method were in almost complete accord (99%) with those of the reference identification schemes, while in the commercial systems examined the percentage of errors ranged from 13 to 14 in the identification of Providencia species.

Commercial identification systems often fail to identify Providencia stuartii

We tested 145 clinical isolates in an attempt to evaluate some of the most widely used commercial identification systems in Europe in terms of their ability to identify Providencia strains. Two manual miniaturized systems (API 20E and Enterotube II) and three mechanized-automated systems (Cobas-Bact, Sceptor System, and Titertek-Enterobac-Rapid Automated System) were evaluated. Providencia alcalifaciens and Providencia rettgeri strains were correctly identified by all systems in all cases, and in most cases identification was achieved without the aid of supplementary tube tests. By contrast, Providencia stuartii was identified without the aid of supplementary tube tests for only 42.5% (API 20E), 37.5% (Enterotube), 68.7% (Sceptor), and 71.2% (Cobas-Bact) of the isolates. The overall misidentification rates were 16.3, 11.3, 11.3, and 10%, respectively. The Titertek-Enterobac-Rapid Automated System failed to identify only 1 of 80 strains (1.3%) and required supplementary tests in 2 other cases (2.5%). Since four of the multitest systems examined often failed to correctly identify P. stuartii, we conclude that supplementary conventional tube tests should always be used to distinguish this species from the other taxa of the Proteeae tribe.

Comparative in vitro activities of 13 antimicrobial agents against Morganella-Proteus-Providencia group bacteria from urinary tract infections

We examined 741 urinary tract isolates of the Morganella-Proteus-Providencia group, including the recently defined species Proteus penneri, for susceptibilities to aminoglycosides, semisynthetic penicillins, and cephalosporins. The data emphasize the importance of identification to the species level on the basis of marked species differences in patterns of susceptibility.

Speciation, serotyping, antimicrobial sensitivity and plasmid content of Proteeae from the environment of calf-rearing units in South West England

A survey was undertaken of the occurrence, serotype, antimicrobial sensitivity and plasmid content of members of the tribe Proteeae in the environment of two calf-rearing units in the county of Avon in South West England. Examples of the following species were found: Proteus mirabilis, Prot. vulgaris, Prot. vulgaris Biogroup 2, Morganella morganii, Providencia stuartii, Prov. alcalifaciens and Prov. rettgeri. A wide range of serotypes was found, many having been previously reported from nosocomial isolates. A total of 15% of isolates carried plasmids; six pairs of isolates were identified which had identical serotypes but different patterns of plasmid carriage. The antimicrobial sensitivity of the isolates was generally similar to isolates of Proteeae from humans. Although no truly aminoglycoside-resistant isolates were found, some isolates of Prov. stuartii and Prov. rettgeri had MIC's higher than the other isolates to gentamicin and netilmicin, suggesting the presence of low levels of the enzyme AAC 2'. The study demonstrates that there is a considerable diversity of species and types of Proteeae associated with calves and their environment. It seems likely that a potential cause of colonization of the human gut by Proteeae is the consumption of meat.

Susceptibilities of 45 clinical isolates of Proteus penneri

Patterns of susceptibility of 45 Proteus penneri clinical isolates to 14 antimicrobial agents were evaluated by a macrobroth dilution method. All strains were highly susceptible to ceftizoxime, ceftazidime, moxalactam, cefoxitin, gentamicin, tobramycin, netilmicin, and, with few exceptions, to amikacin, piperacillin, and cefoperazone. Most strains were susceptible to cefotaxime and ceftriaxone. All strains were resistant to cefazolin and cefsulodin.

Moxalactam (latamoxef). A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Moxalactam (latamoxef) is a new synthetic oxa-beta-lactam antibiotic administered intravenously or intramuscularly. It has a broad spectrum of activity against Gram-positive and Gram-negative aerobic and anaerobic bacteria, is particularly active against Enterobacteriaceae and is resistant to hydrolysis by beta-lactamases. Moxalactam has moderate activity against Pseudomonas aeruginosa, but on the basis of present evidence can not be recommended as sole antibiotic treatment of known or suspected pseudomonal infections. Like the related compounds, the cephalosporins, moxalactam is effective in the treatment of complicated urinary tract infections and lower respiratory tract infections caused by Gram-negative bacilli. As moxalactam is also active against Bacteroides fragilis it has considerable potential in the treatment of intra-abdominal infections in patients with normal immunological mechanisms, as well as in immunocompromised patients, when used alone or in combination with other antibiotics. Likewise, its ready penetration into the diseased central nervous system, its high level of activity against Gram-negative bacilli, and the lack of necessity to monitor drug plasma concentrations, indicate its potential value in the treatment of neonatal Gram-negative bacillary meningitis. Further clinical experience is needed before it can be determined whether moxalactam alone can be used in the treatment of conditions for which the aminoglycosides are drugs of choice, but if established as equally effective, moxalactam has the advantage of being devoid of nephrotoxicity. Bleeding is a potentially serious problem, however, particularly in the elderly, malnourished and in the presence of renal impairment.

Comparative in vitro activity of semisynthetic penicillins against Proteeae

The in vitro susceptibilities of 181 isolates of precisely identified Proteeae species to five semisynthetic penicillins were determined with low and high inocula. Significant differences in susceptibility patterns among various Proteeae species to the penicillins examined were demonstrated. Providencia stuartii was clearly distinguished from Providencia alcalifaciens by its greater resistance to the antibiotics tested.