Transferable drug resistance (R-factor) among the enterobacteriaceae in urinary tract infections: a study at an urban hospital in Bangladesh

Prevalence and patterns of drug resistance were studied among Enterobacteriaceae, isolated from the cases of urinary tract infection (UTI) attending at an outpatient department of an urban hospital in Dhaka. Out of 90 Enterobacteriaceae isolated, 95.5% were resistant to the different antimicrobials tested. The most common resistance pattern observed was against ampicillin (A), trimethoprim (Tm), sulphamethoxazole (S), tetracycline (T) and chloramphenicol (C) in all four genera of Enterobacteriaceae. Transferable drug resistance (R(+)-factor) was detected in 68.5% Escherichia coli (E. coli), 60% Klebsiella, 66.6% Proteus and 50% Citrobacter strains. By using a resistance transfer factor (RTF) mobilizing strain, resistance factors were transferred from 3 (11.3%) out of 26 non-autotransferable strains. The study revealed that transferable drug resistance is common in organisms isolated from UTI in Bangladesh.

[3 new cases of Enterobacter taylorae infection]

BACKGROUND

Enterobacter taylorae is a recently identified microorganism pertaining to the enterobacterian family. To date few infections by this organism have been reported with their clinical significance being unknown. Three patients with Enterobacter taylorae infection are described with the possible pathogenic capacity of this microorganism in concurrence with opportune epidemiologic features being commented upon in addition to the different sources of infection.

METHODS

Biochemical identification of the microorganisms was performed by the automatized MicroScan system (Baxter). The sensitivity to the different antimicrobians was determined by automatized reading (Baxter) of the seried microdilution to the last point.

RESULTS

The two first patients presented infection of an open wound with E. taylorae being isolated from the culture of the exudate of the wound and from a culture of the drainage point, respectively. The third patient developed nosocomial bacteremia following prolonged hospital stay with growth of E. taylorae being found in two different blood culture series. Different biotypes of the E. taylorae species were isolated in the three patients. Specific treatment was administered to the three patients according to the antibiogram with improvement in the clinical manifestations being observed.

CONCLUSIONS

The three clinical cases herewith described suggest that E. taylorae is a potentially pathogenic microorganism which, in determined circumstances (empiric antibiotic treatment, open wounds, diagnostic or therapeutic instruments) may produce clinical pictures similar to those described for other Enterobacter species.

Successful treatment of early infective endocarditis and mediastinitis in a heart transplant recipient

We report a case of bacterial endocarditis in a heart transplant recipient that was diagnosed 6 weeks after operation when a transesophageal echocardiogram revealed vegetations on both sides of the atrial septum. The patient also had postoperative mediastinitis and pericarditis. He underwent two mediastinal explorations, pericardiectomy, and 22 weeks of antibiotics and is free of infection 1 year after transplantation. We presume that the source of infection was contamination of the donor heart by the donor's right lung, which was harvested en bloc with the heart.

Five cases of high-level aminoglycoside resistant enterococcal septicaemia in Singapore

Five clinical cases of enterococcal septicaemia were studied retrospectively including determination of high-level aminoglycoside resistance (HLAR) to gentamicin, streptomycin and kanamycin. This is the first study of its kind in Singapore. The clinical features and risk factors for this illness were analysed and found to be very similar to enterococcal bacteremia in general. It is important to carry out tests to detect HLAR so that unnecessary aminoglycoside toxicity can be prevented or to decide on the appropriate aminoglycoside to combine with a cell wall-active agent in severe enterococcal sepsis.

Clinical significance and spread of fluoroquinolone resistant uropathogens in hospitalised urological patients

The minimum inhibitory concentrations (MIC) of ciprofloxacin were determined for 441 uropathogens from patients with complicated and/or hospital acquired urinary tract infections (UTI). None of the Enterobacteriaceae was resistant (MIC > or = 4 mg/l), but 21.7% of enterococci, 28.3% of Pseudomonas spp. and 38.5% of staphylococci were. Subtyping of the strains revealed that with staphylococci there was no clonal spread of resistant strains. In the case of enterococci and Pseudomonas spp., however, cross infections played a major role (46% and 40% respectively). In a retrospective analysis of 370 UTI episodes caused by Pseudomonas aeruginosa (74), enterococci (185) or staphylococci (111) there was no difference between sensitive and resistant strains with respect to clinical aspects and rates of elimination by appropriate anti-bacterial therapy. The rates of spontaneous disappearance without antibacterial therapy ranged from 28% in the case of P. aeruginosa up to 63% in the case of coagulase-negative staphylococci. This implies that especially in UTI caused by gram-positive cocci an indication for antibacterial therapy should be weighted thoroughly and fluoroquinolones should only be used in accordance with sensitivity testing.

Plantar cellulitis

An unusual case of acute cellulitis of the foot in a child is reported. The child failed to respond to standard treatment even after removal of an occult foreign body. Wound cultures revealed Klebsiella oxytoca and Citrobacter freundii. This is the first documented report on Klebsiella oxytoca in cellulitis. The cellulitis resolved after being treated with the appropriate antibiotics.

Citrobacter meningitis in adults

Citrobacter meningitis is an uncommon infection of neonates and young children. It is rarely seen in adults. We describe a 46-year-old man with a mixed bacterial meningitis caused by C. diversus and Klebsiella oxytoca and a 64-year-old woman with C. freundii meningitis. Review of the English-language literature revealed only 2 adult patients with C. diversus meningitis and another 2, with C. freundii meningitis. The ages of these 6 aforementioned patients ranged from 31 to 84 years. Multiple facial fractures, neurosurgical procedures, alcoholism and diabetes mellitus were predisposing conditions. Among the 5 patients whose outcome was known, antibiotic therapy was successful in 4 but failed in 1. This study emphasizes that almost any of the gram-negative bacilli can cause serious infection of the central nervous system in adults in the proper setting.

beta-Lactam resistance amongst Enterobacter species

Following the introduction of extended-spectrum cephalosporins into clinical use, the prevalence of species belonging to the genus Enterobacter has increased because of their natural resistance to earlier cephalosporins and their ability to develop resistance rapidly to the newer drugs. beta-Lactam resistance in this genus is due, for the most part, to the presence of a Bush group 1 chromosomal cephalosporinase. This enzyme is normally inducible and resistance to older cephalosporins, cephamycins and aminopenicillins results from either the extreme lability of the drugs to the enzyme or from their inducer activities. Resistance to newer penicillins, cephalosporins and monobactams is attributable to the selection of mutants which express large amounts of the enzyme. Such mutants arise as the result of a spontaneous mutation in one of the regulatory genes responsible for suppressing enzyme expression. Since the enzyme has very high affinity for the newer cephalosporins, this, coupled with the slow penetration of the drugs into the cell, provides a very efficient mechanism of resistance. Recent surveys in the USA and elsewhere have shown that the increased prevalence of multi-beta-lactam-resistant strains of enterobacter is due to the increased use of the newer cephalosporins. Attempts to prevent these problems include the more judicious use of newer beta-lactam antibiotics and the development of enhanced-potency cephalosporins which are able to avoid resistance because they have lower enzyme affinity and permeate more rapidly into the cell.

Enterobacter agglomerans--associated cotton fever

Cotton fever is usually a benign febrile, leukocytic syndrome of unknown etiology seen in intravenous narcotic abusers. Cotton and cotton plants are heavily colonized with Enterobacter agglomerans. We report a case of cotton fever associated with E agglomerans in which the organism was first isolated from the patient's blood and secondarily from cotton that he had used to filter heroin. Enterobacter agglomerans is with most probability the causal agent of cotton fever. Patients presenting with the classic history should have blood cultures performed and should be started on a regimen of empiric antibiotic therapy.

Infections associated with the genus Edwardsiella: the role of Edwardsiella tarda in human disease

The role of the genus Edwardsiella in human illness is reviewed. Of the three recognized species, only Edwardsiella tarda has been demonstrated to be pathogenic for humans. Chief infections associated with this species include bacterial gastroenteritis, wound infections such as cellulitis or gas gangrene associated with trauma to mucosal surfaces, and systemic disease such as septicemia, meningitis, cholecystitis, and osteomyelitis. Risk factors that are associated with E. tarda infections include exposure to aquatic environments or exotic animals (e.g., reptiles or amphibia), preexisting liver disease, conditions leading to iron overload, and dietary habits (e.g., raw fish ingestion). Although studies indicate that this bacterium is susceptible to most commonly prescribed antibiotics, fatal gastrointestinal and extraintestinal infections have been described.

Spontaneous bacterial peritonitis in an adult patient with nephrotic syndrome

Most cases of spontaneous bacterial peritonitis (SBP) in association with nephrotic syndrome are children. The complication of SBP in adults with nephrotic syndrome is extremely rare. Herein, we report a 25-year-old man with nephrotic syndrome and chronic renal failure who suffered from SBP. Citrobacter freundii was isolated from ascites. Irreversible deterioration of renal function followed the development of SBP, though the peritonitis was cured with antibiotic treatment. This case suggests that SBP is a rare, but serious complication of adult nephrotic syndrome with ascites.

Prostatitis--an increasing clinical problem for diagnosis and management

Prostatitis remains a challenging condition. The clinical features are often nonspecific while the aetiology and pathogenesis can be diverse and includes inflammatory, obstructive, and/or chemical causes and may also be related to calculi. Four categories are recognized: acute bacterial prostatitis, chronic bacterial prostatitis, non-bacterial prostatitis and prostatodynia. The diagnosis of prostatitis was advanced substantially by the introduction of sequential sampling of urine aliquots following prostatic massage. Bacterial prostatitis is largely associated with the Enterobacteriaceae although Pseudomonas spp., enterococci and Staphylococcus aureus may also be isolated. In chronic bacterial prostatitis a variety of streptococci and anaerobic bacteria may be isolated. Treatment is difficult largely owing to the limited range of agents able to achieve therapeutic concentrations within prostatic fluid, which has a pH lower than that of plasma. Trimethroprim, co-trimoxazole and the tetracyclines have been widely used. The quinolones have recently been shown to diffuse readily into the prostate; ofloxacin and temafloxacin have produced the highest concentrations in prostatic fluid. Antibiotic treatment requires prolonged high dosage and careful monitoring to ensure that bacterial eradication has occurred. Other forms of management have included the judicious use of anti-inflammatory agents and analgesics. In some patients zinc sulphate has proved to be of symptomatic benefit.

Catheter-related Rahnella aquatilis bacteremia in a pediatric bone marrow transplant recipient

Rahnella aquatilis, a rarely encountered member of the family Enterobacteriaceae, was twice isolated from the blood of a pediatric bone marrow transplant recipient. This is the first report of a pediatric case of R. aquatilis bacteremia, and it was probably related to inappropriate handling of a Hickman catheter.

Emergence of resistance to imipenem in Enterobacter isolates masquerading as Klebsiella pneumoniae during therapy with imipenem/cilastatin

Clinical isolates identified as Klebsiella pneumoniae by the Vitek, Enterotube II, and API 20E systems were recovered from a patient undergoing therapy with imipenem/cilastatin. These isolates were resistant to multiple beta-lactam agents, and some were even resistant to imipenem. Analysis revealed a Bush group 1 beta-lactamase, and imipenem resistance corresponded to the loss of outer-membrane proteins in strains expressing high levels of this beta-lactamase. Further characterization efforts yielded abnormal but positive results of tests for ornithine decarboxylase production and motility, and chromosomal homology to an Enterobacter cloacae ampR, ampC probe was detected. These results suggested that the organisms were actually of an Enterobacter species, perhaps Enterobacter aerogenes. Cefoxitin resistance may be a useful marker for preventing this misidentification in the future; misidentification of such organisms poses a hazard, as it may lead to inappropriate beta-lactam therapy for infections caused by organisms that have the potential for resistance due to inducible group 1 cephalosporinases.

The use of imipenem-cilastatin in neonatal meningitis caused by Citrobacter diversus

Citrobacter diversus is a cause of severe meningitis in neonates and infants. It is unique in its propensity to produce brain abscesses that play an important role in the poor prognosis associated with this condition. The recommended therapeutic regimen of third-generation cephalosporines, aminoglycosides and trimethoprim-sulfamethoxazole is usually disappointing. We describe the use of imipenemcilastatin in successfully treating Citrobacter diversus meningitis complicated by brain abscesses.

Antibiotic therapy for enterobacter meningitis: a retrospective review of 13 episodes and review of the literature

Enterobacter meningitis is an uncommon form of meningitis whose treatment poses a therapeutic dilemma because of the development of resistance to the third-generation cephalosporins while the patient receives therapy. In recent years, we have been using trimethoprim-sulfamethoxazole (TMP-SMZ) as treatment for this infection. In this report, we reviewed 13 episodes of enterobacter meningitis that were treated with various antibiotic regimens and 33 episodes from the literature. We found that the development of resistance to beta-lactam agents may be much higher than that seen in bacteremias (approximately 30%), that the case-fatality rate is lower among our patients than among those described previously, and that all patients who received TMP-SMZ were cured, compared with about 70% of those receiving beta-lactam agents. TMP-SMZ appears to be an acceptable alternative to the cephalosporins for the treatment of enterobacter meningitis.

The post-antibiotic effect of antimicrobial combinations in a neutropenic murine thigh infection model

The post-antibiotic effect (PAE) may allow for more widely spaced dosing of antibiotics than is currently employed without loss of efficacy. Antimicrobial combinations are widely used in clinical medicine. However, dosing schedules are usually based on pharmacological profiles of the drugs used alone. Previously we have demonstrated significant prolongation of the PAE induced by antimicrobial combinations in vitro as compared to PAEs induced by the agents alone. We examined this issue further in vivo in a neutropenic mouse thigh infection model, by exposing Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae to several antimicrobials, either singly or in combination. The PAE in vivo was defined as the difference in time needed for the organisms in the treated animals to grow 1 log10 as compared with controls after serum drug concentrations had fallen below the MIC. Drug concentrations exceeded the MIC for 1.2-3.2 h, but bactericidal activity occurred mainly during the first hour. When the agents were used singly a negative PAE was produced by ceftazidime against P. aeruginosa, a PAE of approximately 0 h by imipenem against E. coli and K. pneumoniae, a PAE of 2-4 h by cefazolin against S. aureus, gentamicin against E. coli and K. pneumoniae, and imipenem and tobramycin against P. aeruginosa, and a PAE of 6-7 h by gentamicin against S. aureus and rifampicin against P. aeruginosa. The beta-lactam/aminoglycoside combinations when used against S. aureus and P. aeruginosa prolonged the PAE by 1.0-3.3 h, compared with the longer of the individual drug PAEs, but no prolongation was observed against E. coli and K. pneumoniae. Ceftazidime reduced the PAE when used with tobramycin against P. aeruginosa. The long PAE of rifampicin against P. aeruginosa was 'carried over' to the combination, thus prolonging the growth suppression achieved by imipenem and tobramycin alone or in combination by 5.5-8.0 h. This effect on the PAE was additive only, and synergy was not observed. In conclusion, a potentially significant prolongation of the PAE by combination of drugs was observed in vivo, but only if both (or all) agents induced a PAE when used alone. The impact of this observation needs to be examined further in studies involving multiple and different dosing regimens in an infection model.

In vitro activity of azithromycin against bacterial enteric pathogens

The in vitro activity of azithromycin against enteric bacterial pathogens was determined by agar dilution. Azithromycin was highly active against Campylobacter spp. (MIC for 90% of strains tested [MIC90] = 0.125 micrograms/ml) and against enterotoxigenic, enterohemorrhagic, enteroinvasive, and enteropathogenic Escherichia coli (MIC90 = 2 micrograms/ml), Shigella spp. (MIC90 = 1 micrograms/ml), and Salmonella spp. (MIC90 = 4 micrograms/ml), including Salmonella typhi (MIC90 = 1 microgram/ml). On the basis of the in vitro activity of the drug against these organisms, clinical studies of azithromycin in enteric diseases should be considered; the high intracellular concentrations achieved by azithromycin may be particularly relevant for organisms like S. typhi, Campylobacter spp., and Shigella spp. which typically invade cells as part of their infectious process.

Bacterial agents in neonatal septicaemia in Calabar, Nigeria (a review of 100 cases)

This study of bacterial isolates in 100 cases of proven neonatal septicaemia has shown Staphylococcus aureus and coliform bacterials the dominant gram positive and gram negative organisms respectively. Most gram negative bacteria and Staphylococcus aureus were sensitive to gentamycin, while streptococci were sensitive to ampicillin. On the basis of this antimicrobial sensitivity pattern, we recommend the use of gentamycin and ampicillin as initial antibiotics in neonatal septicaemia.

Enterobacter taylorae, a new opportunistic pathogen: report of four cases

Severe nosocomial infections due to Enterobacter taylorae (formerly known as CDC Enteric Group 19) are described in four patients. Unlike most members of the Enterobacter genus, the isolates were not susceptible to penicillins or cephalosporins. Restriction endonuclease analysis of E. taylorae DNA obtained from three patients identified two distinct strains. One strain was found in two patients, suggesting a common source which we were not able to identify. We postulate that in patients harboring E. taylorae, the combination of cephalosporin therapy and instrumentation enables this organism to become an opportunistic pathogen.

Increased resistance to quinolone in Catalonia, Spain

From 1989 to 1991, the level of resistance to ciprofloxacin in our hospital increased from 0.47% to 6.7% in opportunistic Enterobacteriaceae, from 9.9% to 16% in Pseudomonas aeruginosa and from 8.27% to 31.8% in Campylobacter jejuni-coli. We also observed an increase in quinolone consumption from 1.1 in 1989 to 1.5 defined daily doses per 1000 inhabitants per day in 1991.

Clinical and bacteriological study of nosocomial infections due to Enterobacter aerogenes resistant to imipenem

Enterobacter aerogenes strains resistant to imipenem were isolated in 10 patients, 7 of whom had received imipenem-cilastatin. The strains were differentiated by biotype, antibiotype, and plasmid content. All of the strains overproduced a chromosomal cephalosporinase and lost a major outer membrane protein with a size of about 40 kDa. In 5 of the 10 patients, E. aerogenes strains resistant to extended-spectrum cephalosporin were isolated during the same stay. In three patients, the similarity between the imipenem-susceptible and -resistant strains suggests the occurrence of mutation and reversion in vivo. The combination imipenem-cilastatin has been critically important for use with multiresistant strains of Enterobacter spp., but its use increases the risk of selection of imipenem-resistant strains.