Prospective survey of fecal, urinary tract, and environmental colonization by Providencia stuartii in two geriatric wards

The 2017 Garrod Lecture: Genes, guts and globalization

The widespread use of antibacterial drugs over the last 70 years has brought immense benefits to human health at the price of increasing drug inefficacy. Antibacterial agents have a strong selective effect in both favouring resistant strains and allowing particular species and families of bacteria to prosper, especially in the healthcare setting. Whilst important Gram-positive bacterial pathogens such as Staphylococcus aureus and Streptococcus pneumoniae caused concern over the last 20 years because of the spread of antibiotic-resistant strains, Enterobacteriaceae have become the biggest challenge. They have very efficient mechanisms for genetic exchange, as illustrated by the emergence and rapid spread of CTX-M β-lactamases and the carbapenemases. The unique epidemiology of Enterobacteriaceae, with substantial numbers colonizing the mammalian gut and subsequent release into and spread in the environment, presents a significant threat to human health because of the high levels of exposure for the whole community. The use of antimicrobials in agriculture combined with global movements of people, animals and food, arising from worldwide industrialization, generates a diversity and level of resistance not seen previously. Control will require globally coordinated interventions similar to those needed to ameliorate climate change.

Antibiotic Resistance in Long-Term Care Facilities

Long-term care facilities are comprised of a heterogeneous group of institutions caring for residential patients over prolonged periods of time. Included as long-term care facilities in this review are private and Veterans' Affairs (VA) nursing homes, rehabilitation centers, institutions for the developmentally disabled, and hospital wards for both long-term and intermediate care. Patients in long-term care facilities incur bacterial infections at a prevalence of 10% to 16%. These infections usually are caused by common bacterial pathogens that invade the compromised host residing within a complex physical environment. The high prevalence of institutional infections leads, in turn, to the need for multiple courses of antimicrobials or for hospitalization. This process selects strains more resistant to antibiotics, which are then available for repeated dispersal in the long-term care facility.

Proteeae Groin Skin Carriage in Ambulatory Geriatric Outpatients

Aerobic gram-negative bacillus (AGNB) groin skin carriage was prospectively studied in ambulatory geriatric outpatients: 42 from three nursing homes and 44 from private homes. Initially, 12 (28.6%) Proteeae carriers were in the former group and 3 (6.8%) were in the latter (P =0.01). At one year, 6 of 7 surviving nursing home carriers remained Proteeae carriers while none from private homes remained carriers (P =0.007). The annual prevalence of Proteeae carriage was 14 (33.3%) in nursing homes and 4 (9.1%) in private homes (P =0.008); of non-Proteeae AGNB carriage, the annual prevalence was 2 (4.8%) and 4 (11.4%), respectively. Nursing home subjects had similar initial health characteristics; however, by one year, 5 of 12 carriers in contrast to 3 of 30 noncarriers were dead of chronic disease (P =0.03). These nursing homes included persons with chronic diseases that apparently facilitated Proteeae carriage. Urethral catheters, skin ulcers, and recent antibiotics were not factors.

Selective medium for primary isolation of members of the tribe Proteeae

A selective Proteeae medium (SPM) for isolation and preliminary detection of species of genera Proteus, Morganella, and Providencia was evaluated. The SPM contains tryptose phosphate agar with phenolphthalein monophosphate (as substrate for phosphatase activity), bile salts and polymyxin B (as inhibitors). The selectivity of the SPM was tested by the ecometric method of quality assurance of culture media. Fourteen reference cultures of enterobacteria and fifty-four strains of Proteeae were tested for their absolute growth index (AGI). Ninety-five percent of tested Proteeae strains display an AGI above 2.5. The detected phosphatase activity proved to be able to discriminate colonies of members of the tribe Proteeae. The ability of SPM for primary isolation of members of Proteeae was tested on food and clinical material and 94 strains were isolated. In addition, the SPM was employed in routine practice of clinical microbiology. From 1016 clinical samples (stool, urine, vaginal and urethral swabs), 57 strains of Proteeae were detected by the SPM in contrast to 35 strains by the routine procedure. The difference amounts to nearly 40%.

Measuring antibiotic use in a long-term care facility

BACKGROUND

In the long-term care facility setting, there is little information about correlation of antibiotic use with care delivered or with the occurrence of fever or use of Foley catheters. The objectives of this study were to compare various measures of quantitating antibiotic use and to correlate these measures with febrile morbidity and Foley catheter use in a hospital-based, long-term care facility.

METHODS

This was a prospective study in which the number of residents with fever (rectal temperature of 100.5 degrees F or greater) or a Foley catheter was documented daily. Antibiotic use was measured in several ways; incidence (courses per 100 resident care days), proportion of resident care days that were antibiotic days, the number of antibiotic courses per month, and the number of residents treated per month.

RESULTS

Between January and December 1989, 111 (71%) of 156 residents were prescribed 263 antibiotic courses. Incidence of antibiotic use was 0.61 courses per 100 resident care days. On average only about 5% of resident care days per month were associated with antibiotic use, whereas an average of 18 residents per month received antibiotic therapy. Trimethoprim/sulfa and ciprofloxacin together accounted for 55% of the courses prescribed. No significant correlations were found between any antibiotic use measure and febrile days or Foley catheter days each month.

CONCLUSIONS

In the long-term care facility setting, monitoring the number of residents treated with antibiotics per month is a more practical and useful measure of use than measurement of resident care days on antibiotics per month.

Antibiotic resistance in long-term care facilities

Long-term care facilities are comprised of a heterogeneous group of institutions caring for residential patients over prolonged periods of time. Included as long-term care facilities in this review are private and Veterans' Affairs (VA) nursing homes, rehabilitation centers, institutions for the developmentally disabled, and hospital wards for both long-term and intermediate care. Patients in long-term care facilities incur bacterial infections at a prevalence of 10% to 16%. These infections usually are caused by common bacterial pathogens that invade the compromised host residing within a complex physical environment. The high prevalence of institutional infections leads, in turn, to the need for multiple courses of antimicrobials or for hospitalization. This process selects strains more resistant to antibiotics, which are then available for repeated dispersal in the long-term care facility.

Proteeae species bacteriuria accompanying Proteeae species groin skin carriage in geriatric outpatients

There have been numerous reports of Proteeae species urinary tract infections among elderly individuals. To explore a possible urinary carrier source of Proteeae species in this population, the frequency of aerobic gram-negative bacillus (AGNB) bacteriuria at the greater than or equal to 10(2)/ml level was determined in 67 ambulatory elderly outpatients classified as to Proteeae group (Morganella, Proteus, Providencia) groin carriage by a set of two skin cultures obtained at least 1 week apart. None had urethral catheters, symptomatic infections, skin ulcers, or recent antibiotic therapy. We found AGNB bacteriuria in 12 of 15 carriers (80%) and in 21 of 52 noncarriers (40%) (P = 0.009). Proteeae species bacteriuria occurred in eight carriers (53.3%) and six noncarriers (11.5%) (P = 0.001). At the 10(2) to 10(4)/ml level, Proteeae species were isolated in urine specimens from seven carriers (46.7%) and four noncarriers (7.7%) (P = 0.001). There was concordance of species of skin and urine Proteeae isolates in six carriers. By contrast, non-Proteeae AGNB bacteriuria at any level was present in four Proteeae species carriers (26%) and 15 noncarriers (28.8%) (P greater than 0.05). There was a 36.7% frequency of Proteeae species bacteriuria in nursing home residents, in contrast to 8.1% among those living in private homes; this parallels the greater frequency of Proteeae species groin carriage among nursing home residents in the study population. Low-level urinary colonization with Proteeae species accompanying Proteeae species groin skin colonization in elderly individuals is a hitherto unrecognized finding. This may account for the greater frequency of Proteeae species urinary infections in this population.

Proteeae groin skin carriage in ambulatory geriatric outpatients

Aerobic gram-negative bacillus (AGNB) groin skin carriage was prospectively studied in ambulatory geriatric outpatients: 42 from three nursing homes and 44 from private homes. Initially, 12 (28.6%) Proteeae carriers were in the former group and 3 (6.8%) were in the latter (P = 0.01). At one year, 6 of 7 surviving nursing home carriers remained Proteeae carriers while none from private homes remained carriers (P = 0.007). The annual prevalence of Proteeae carriage was 14 (33.3%) in nursing homes and 4 (9.1%) in private homes (P = 0.008); of non-Proteeae AGNB carriage, the annuyal prevalence was 2 (4.8%) and 4 (11.4%), respectively. Nursing home subjects had similar initial health characteristics; however, by one year, 5 of 12 carriers in contrast to 3 of 30 noncarriers were dead of chronic disease (P = 0.03). These nursing homes included persons with chronic diseases that apparently facilitated Proteeae carriage. Urethral catheters, skin ulcers, and recent antibiotics were not factors.

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.

Selective and differential medium for the primary isolation of members of the Proteeae

A new differential and selective medium for the isolation of members of the Proteeae, PIM (Proteeae isolation medium) agar, was developed and evaluated. The medium relies on the ability of all members of the Proteeae (with the exception of a very few Morganella morganii strains) to produce a dark brown pigment in medium containing DL-tryptophan. An additional differential property, tyrosine degradation, was also demonstrated by the medium. Members of the Proteeae appeared as dark brown colonies with a halo of clearing of fine tyrosine crystals when cultured on PIM agar. Occasional strains of Citrobacter sp. and Pseudomonas aeruginosa may degrade tyrosine, but none has the ability to produce dark brown pigmentation on PIM agar. Quantitative recovery studies showed that the addition of 5 mg of clindamycin per liter suppressed gram-positive bacteria without inhibiting any strains of the Proteeae. The addition of 100 mg of colistin per liter made the medium highly selective for strains of the Proteeae, but approximately 10% of the strains were not isolated, thus making this formulation unsuitable for general surveys of the occurrence of members of the Proteeae. PIM agar should aid the investigation of episodes of cross infection caused by members of the Proteeae and the isolation of the new species of the Proteeae recently described.

Occurrence and pathogenic role of Morganella-Proteus-Providencia group bacteria in human feces

A total of 2,693 fecal specimens, with 1,422 from healthy persons and 1,271 from patients suffering from enteric diseases, was investigated to isolate species of the Morganella-Proteus-Providencia group and to evaluate the role of these bacteria in intestinal disorders. Most strains were isolated from two media, i.e., blood agar and tryptophan agar. Two of the species were more frequently found in diarrheal cases than in healthy controls. These species were Morganella morganii and Proteus mirabilis. Two new species of Enterobacteriaceae, i.e., Proteus penneri and Providencia rustigianii, were found in 33 and 5 people, respectively. However, these two species were not found more frequently in the diarrheal cases.

Variable phenotypes of Providencia stuartii due to plasmid-encoded traits

Weekly urine specimens from 51 long-term catheterized patients yielded 699 isolates of Providencia stuartii. Urease-positive strains represented 23.7% (166) of the isolates, sucrose-positive strains represented 24.5% (171), and lactose-utilizing strains represented 0.7% (5). Urease and sucrose traits were transferred by conjugation to Escherichia coli via an 82-kilobase plasmid; lactose fermentation was transferred by a 150-kilobase plasmid.

Infections and infection risk in residents of long-term care facilities: a review of the literature, 1970-1984

We reviewed the English-language peer-reviewed journals and the Centers for Disease Control's Morbidity and Mortality Weekly Reports between 1970 and 1984 presenting information about infections and infection risk in residents of long-term care facilities. More than 50 articles met review criteria. Approximately one third of the articles were reports of outbreaks, primarily of respiratory and gastrointestinal infections. Seven articles reported rates for several infection sites, but most rates were not directly comparable to one another because numerators and/or denominators were different. Many of the studies have been done in Veterans Administration hospitals with largely male populations, which may limit their applicability to freestanding long-term care facilities with largely female clients. This review establishes the need for high-quality observational studies of infections in long-term care facilities. Such studies are needed before intervention studies can be done to measure the effect of manipulation of risk factors on infection outcome.

Characterization of endemic Providencia stuartii isolates from patients with urinary devices

Providencia stuartii has emerged as a significant nosocomial urinary tract pathogen. An increase in the number of Providencia isolates from urine cultures prompted an investigation into the possibility of an outbreak due to this organism. A high proportion of patients studied had urinary devices. Four wards were screened at two time periods to ascertain the prevalence of Providencia stuartii in urine cultures. Biotype, serotype, antibiogram and plasmid content were determined for each Providencia isolate. Of 129 patients initially sampled 22.5% were found to harbor Providencia stuartii. Biotyping, serotyping and antibiograms indicated an epidemic strain was not present. Similar results were obtained when the wards were screened a second time, with 25.4% of urine cultures found to contain Providencia stuartii. By plasmid analysis the isolates could be grouped into one of ten profiles. A correlation could be made between urease activity and the presence of a large plasmid. No association however could be made between a particular plasmid profile and antibiogram. The data indicate that an epidemic strain of Providencia stuartii was not present. The source(s) of the endemic Providencia stuartii strains remain unknown.

Genitourinary infections in the patient at risk: extrinsic risk factors

The indwelling urinary catheter is an essential part of modern medical care. It is widely used to relieve temporarily anatomic or physiologic urinary obstruction, to facilitate surgical repair of the urethra and surrounding structures, to provide a dry environment for comatose or incontinent patients, and to permit accurate measurement of urinary output in severely ill patients. Unfortunately, when poorly managed, the indwelling catheter may present a hazard to the very patients it is designed to protect. It is the leading cause of nosocomial induced urinary tract infections and the most common prediposing factor in fatal gram-negative sepsis in hospitals. Catheters drain the bladder, but they obstruct the urethra, producing other major problems such as urethral strictures and epididymitis. Advances in catheter care since the introduction of closed drainage are reviewed. The best means of prevention is the avoidance of use when unnecessary and prompt removal when the need no longer exists. This practice is of particular importance in long-term care institutions. Alternate methods include intermittent catheterization in the paraplegic patient, condom drainage in the nonobstructed patient, and direct drainage of the bladder through the skin. Most recent studies have attempted to improve care of the indwelling catheter by either prevention of periurethral infection (the most common route of acquisition) or sterilization of the drainage bag to prevent ascending infection and cross infection. Thus far, these methods have been unsatisfactory. A new approach to designing drainage systems is clearly needed. Finally, all studies failed to demonstrate the ability of systemic antimicrobial therapy to eradicate catheter-associated infections other than temporarily. Instead, excessive use of antibiotics has led to the emergence of resistant strains that may be spread to other patients through contaminated urine.