The origin of coagulase-negative staphylococci isolated from blood cultures

The source of coagulase-negative staphylococci (CNS) isolated from blood cultures and thought to be contaminants was investigated over a two month period. Isolates recovered from swabs taken from patients, doctors and laboratory staff were compared with the blood culture patient isolate in an attempt to identify the source of contamination. Six hundred and ninety-six blood culture sets were received of which 28 were contaminated with CNS. Nineteen of these blood cultures had sufficient data to be included in this study. Six were matched to isolates from the patient's skin and none to the medical or laboratory staff. Major differences in the antibiograms were seen between the patients, medical and laboratory staff. Organisms from patients and medical staff were more likely to have multiple antibiotic resistances. It appears that the most important source of CNS contamination of blood cultures processed in a semi-automated manner is the patient's own skin flora.

Incidence of "chance" smear positivity among MB leprosy patients after MDT

Multidrug therapy (MDT) was introduced in 1982. Nine hundred eighty multibacillary (MB) leprosy patients had successfully completed the MDT administered for a minimum of two years or till skin smear negativity, whichever was later, as recommended by the World Health Organisation (WHO). During surveillance, 2.24% of them revealed presence of acid-fast bacilli (AFB) in the skin smear. They did not have any clinical evidence suggestive of relapse. Subsequent followup (without antileprosy chemotherapy) for periods ranging from one to eight years was uneventful. We have called this as "chance smear positivity" where a few bacilli, yet to be cleared by the immune system, were picked up by routine skin smear examination.

Cutaneous colonization with staphylococci influences the disease activity of Sézary syndrome: a potential role for bacterial superantigens

It has previously been shown that circulating Sézary cells respond in vitro to superantigenic staphylococcal exotoxins in a manner that is restricted by their V beta usage. This study was conducted to examine whether cutaneous colonization with Staphylococcus aureus influences the activity of the skin lesions of Sézary syndrome, and whether S. aureus isolated from patients with Sézary syndrome stimulates circulating Sézary cells in vitro. Two patients with Sézary syndrome, whose skin was colonized with S. aureus, were treated with antibacterial agents, and the relation between the severity of the skin disease and the degree of S. aureus colonization was assessed. In addition, the patients' peripheral blood mononuclear cells were cultured in the presence of mitomycin C-treated S. aureus or superantigenic staphylococcal toxins. The antibacterial treatment improved the skin disease, and eliminated S. aureus in both patients. In one patient, 98% of the peripheral blood mononuclear cells bore V alpha 2V beta 17 of the T-cell receptor, indicative of the presence of an extremely high percentage of circulating Sézary cells. The peripheral blood lymphocytes from this patient responded well in vitro to superantigenic staphylococcal enterotoxin (SE), but not to SEA or toxic shock syndrome toxin-1, or to mitomycin-treated S. aureus isolated from the same patient. Cutaneous colonization by S. aureus influences the disease activity of CTCL, possibly by activation of Sézary cells by bacterial superantigenic exoproteins.

[An analysis of the information system controlling the status of the normal skin microflora and in pathology]

The skin microflora of healthy adults and patients with acute respiratory diseases has been studied. As revealed in this study, the optimum conditions for functioning the information system are observed in summer. After the action of unfavorable factors the activity of the system deteriorates due to the appearance of disturbances in the paths of the transmission of information. In response, the content of general information in the system increases, while the volume of useful information, necessary for the realization of the effector function, decreases. To stabilize its activity, the system spends its information reserves. These changes in the activity of the system, controlling the permanence of microflora and immunity, are slightly pronounced in winter and reach their maximum manifestation at the peak of acute respiratory disease.

Risk factors for surgical infection

In the last century remarkable advances have been made in surgery, associated with the lowest recorded rates of infection or sepsis. Many surgical practices are time honoured but have little scientific basis to prevent postoperative infection whereas some local and systemic factors are well recognized and can be modified to lower infection risks. Surgical skill is not easily measurable but shorter operations in experienced hands leaving the minimum of tissue damage, haematoma or dead space have the lowest infection rates in general surgery: < 2% in clean and < 10% in contaminated operations. Adequate surgical scrub, appropriate suture materials and antibiotic prophylaxis, perioperative correction of dehydration and poor nutrition are examples of effective therapy which can be conformed to by all surgeons. Other factors, such as the use of wound guards, drains and surgical dressings are less easy to estimate for effectiveness or be sure that they could be changed or left out of surgical ritual.

Classification of leprosy cases under field conditions in Bangladesh. I. Usefulness of skin-smear examinations

In 2 non-governmental organization projects in Bangladesh 244 new leprosy patients were classified in the field according to clinical criteria. Skin smears were taken at 4 standardized sites and at the most active peripheral lesion, where a biopsy was also taken. Comparison of the clinical field classification with the results of the skin smears and biopsies gives a sensitivity of 92.1% for the clinical criteria, but a specificity of only 41.3%. The skin-smear results, on the other hand, have a sensitivity of 88.4% and a specificity of 98.1%. Thus, skin smears may contribute considerably to the operational classification of leprosy patients under field conditions. Quality control of the peripheral laboratory is essential. Appropriate site selection for the smear taking will also contribute to increased performance. Analysis of the skin-smear results suggests that the policy of taking smears at standardized sites should be abandoned in favour of the earlobes and active peripheral lesions.

Classification of leprosy cases under field conditions in Bangladesh. II. Reliability of clinical criteria

In 2 non-governmental organization projects 244 new leprosy patients in Bangladesh were classified in the field according to clinical criteria i.e. number of skin lesions and number of enlarged nerves. Comparison of these classification results with the results of skin smears and biopsies yielded a sensitivity (for detection of a MB case) of 92.1%, but the 'unconfirmed MB rate' amounted to 52.6%. In order to improve the reliability of the operational classification, several additional clinical criteria were investigated. It was found that neither the presence of anaesthesia in the skin lesions nor the presence of grade 2 disabilities or peripheral anaesthesia or voluntary muscle testing (VMT) impairment contributed to an improved classification. Counting the number of body areas showing signs of leprosy, which had proven very useful in other programmes, did not result in a more reliable classification in the 2 projects in Bangladesh. The presence of clinical signs of lepromatous leprosy, more specifically nodules or diffuse infiltration, could be a useful addition to the classification criteria. If the sensitivity must remain higher than 90%, the lowest 'unconfirmed MB rate' obtainable in Bangladesh, using clinical criteria only, is 46.4%, for a sensitivity of 91.0%. However, the inclusion of skin-smear results in the classification criteria could improve the sensitivity to 96.6% and lower the 'unconfirmed MB rate' to 40.3%. A reduction in MB overclassification will result in more efficient and more cost-effective leprosy control programmes.

No detection of Borrelia burgdorferi-specific DNA in erythema migrans lesions after minocycline treatment

BACKGROUND AND DESIGN

Early treatment of erythema migrans is important to prevent late complications. Minocycline possesses several attributes, making it potentially useful in the treatment of borrelial infections. In our study, minocycline was administered to 14 patients with erythema migrans. Punch biopsy specimens were obtained from the (affected) skin of all patients before and after therapy. The formalin-fixed, paraffin-embedded specimens were analyzed by polymerase chain reaction for the presence of Borrelia burgdorferi-specific DNA.

RESULTS

Polymerase chain reaction assay succeeded in amplifying B burgdorferi-specific DNA from the first biopsy specimen, obtained from the border of erythema migrans before initiating treatment, in eight (57%) of 14 patients. At the end of minocycline therapy, however, polymerase chain reaction analysis disclosed no B burgdorferi-specific DNA in any of the 14 patients. The good clinical response of our patients with erythema migrans substantiates our molecular findings.

CONCLUSIONS

The presented polymerase chain reaction data, together with the clinical outcome, indicate that minocycline may be useful for treatment of early Lyme borreliosis.

Can ultrasound probes and coupling gel be a source of nosocomial infection in patients undergoing sonography? An in vivo and in vitro study

OBJECTIVE

At our institution, ultrasound probes are wiped with a clean, dry, soft, absorbent paper towel after each procedure as a basic standard of probe disinfection. However, it was unclear if this provided a sufficient level of decontamination. This study was designed to determine if the ultrasound probe and coupling gel can act as a vector of nosocomial infection and to describe a cost-effective method of probe handling that allows optimal control of infection.

SUBJECTS AND METHODS

In the first part of the study, the ultrasound probe was exposed to the disrupted skin of patients recruited from our inpatient population, using our routine scanning technique to look for subcutaneous collections. Twenty-seven patients were scanned: 17 with surgical wounds, seven with surgical drains, four with enteric stomas, three with biopsy sites, and three with ulcers or excoriation. Fifteen patients had a discharge associated with their disrupted skin, and seven patients had culture-proved skin infections. Each probe was wiped with a clean, dry paper towel after scanning, then immersed in a brain-heart infusion (BHI) broth, and the solution was cultured. In the second part of the study, the ultrasound probe was exposed to a large inoculum of bacteria. Sixty-one probes were used to scan fields of confluent growth of bacteria on agar plates. Twenty-six probes were cleaned by wiping with a dry, clean paper towel, and 25 probes were cleaned by wiping with a dry, clean paper towel followed by immersion in Hibidil (0.05% chlorhexidine weight/volume). Ten probes functioned as controls and were not cleaned after exposure to the bacteria. Each probe was then immersed in BHI broth, and the solution was cultured. In the third part of the study, the coupling gel was evaluated as a culture medium for bacterial growth. Twenty-five agar plates were inoculated with a confluent growth of bacteria. Half of the surface of each agar plate was covered with coupling gel, and the remaining surface was left unexposed. The resulting bacterial growth on each side of the plates was compared.

RESULTS

One of the 27 probes exposed to patients with disrupted skin grew Staphylococcus epidermidis (skin flora). For probes exposed to a large inoculum of bacteria, we found no statistically significant difference in the number of probes that showed bacterial growth on culture between probes cleaned by wiping with a towel and those cleaned with Hibidil. Furthermore, the resulting bacterial growth in both sets of probes was scant and was not considered clinically significant. All 10 control probes showed clinically significant growth in all cases. As for evaluation of the coupling gel as a culture medium, the gel permitted bacterial growth and did not show any evidence of bacteriocidal or bacteriostatic properties.

CONCLUSION

Ultrasound probes that are wiped with a paper towel until they are visibly clean do not contribute to nosocomial infections. Additional antiseptic solutions such as Hibidil are not necessary. We suggest that probes be simply wiped with a clean, dry, nonsterile paper towel between procedures, including probes used on contaminated scanning fields, open wounds, and cutaneous infections. After the final procedure of the day, probes should be cleaned with a liquid cleaning solution such as Hibidil to remove all traces of coupling gel, which could support the overnight growth of bacteria. This would decontaminate the probes and prevent the overnight growth of bacteria. This method would be both a cost-effective and time-efficient protocol for controlling infection.

Use of tissue culture and animal models to identify virulence-associated traits of Haemophilus ducreyi

To identify virulence-associated properties of Haemophilus ducreyi, 34 strains of this sexually transmitted pathogen were evaluated for in vitro phenotypic characteristics of potential relevance to chancroid pathogenesis and for their ability to produce lesions in the temperature-dependent animal model for chancroid. Of the 34 strains tested, all but three produced a cytopathic effect on human foreskin fibroblasts (HFF) and all but six strains formed large microcolonies on HFF monolayers. A subset of 12 selected strains underwent more extensive analyses and, when evaluated for both their cytadherence kinetics and growth in the presence of HFF monolayers, it was found that several of these strains had a very limited ability to attach to HFF cells. When the same 12 strains were tested in the temperature-dependent rabbit model, only the seven strains which were positive in all of these in vitro-based tests readily produced lesions. In contrast, the five strains that were noted to be deficient in one or more of the phenotypic characteristics scored in the in vitro systems did not produce lesions. This association between the traits measured in vitro and the ability to produce dermal lesions was significant (P = 0.0012). These results suggest that in vitro behavior may be used to predict the virulence potential of H. ducreyi strains. Moreover, the phenotypic characteristics described in this study are appropriate focal points for efforts to determine the molecular basis of the virulence of this pathogen.

[Antibacterial effects of antiseptics in vitro and in an experiment in vivo]

The effect of topical antiseptics routinely used in the Department of plastic and aesthetic surgery was tested against bacteria commonly infecting burns and major skin defects. In vivo, the effect on Staphylococcus aureus and Pseudomonas aeruginosa was examined, in vitro also on Proteus mirabilis. A very good effect on tested microorganisms was observed with 0.1% Persteril, Peruvian balsam and Dermazin crm. (Lek, Ljubljana). Gentian violet in a 0.5% concentration and 3% boric acid were not effective on Pseudomonas aeruginosa, 0.05% permanganate and 2% Jodonal were moreover not effective against S. aureus.

Detection of herpes simplex and varicella-zoster infection from cutaneous lesions in different clinical stages with the polymerase chain reaction

BACKGROUND

The polymerase chain reaction (PCR) can be used to diagnose a variety of infectious processes.

OBJECTIVE

We sought to determine whether Tzanck smear debris, vesicle fluid swabs, crusts, or fixed tissue specimens are the best source for template herpes simplex virus (HSV) or varicella-zoster virus (VZV) DNA for the PCR.

METHODS

Patients with both clinical and histologic evidence of HSV (n = 6) or VZV (n = 16) infection were examined. Stained Tzanck smears, vesicle fluid swabs, dried crusts, and skin biopsy specimens were obtained at the same time from each patient. DNA was extracted from the different clinical specimens and then examined for HSV or VZV DNA with PCR. Fifteen control subjects did not have clinical or histologic evidence of herpesvirus infection.

RESULTS

In cases of suspected VZV infection, PCR detected VZV DNA sequences from all 15 Tzanck smears, all 15 vesicle swabs, one of one crust, and 14 of 16 fixed tissue specimens. HSV DNA sequences were detected from all six Tzanck smears, all four vesicle fluid swabs, two of two crusts, and five of six fixed tissue specimens.

CONCLUSION

PCR can detect VZV and HSV DNA sequences from a variety of sources including formalin-fixed tissue specimens. Although viral DNA was detected slightly more frequently from Tzanck smear debris, crusts, and vesicle fluid swabs compared with fixed tissue specimens, each was an excellent source of target DNA for the PCR to confirm the diagnosis of herpesvirus infection.

Phylogenetic characterization of the epibiotic bacteria associated with the hydrothermal vent polychaete Alvinella pompejana

Alvinella pompejana is a polychaetous annelid that inhabits active deep-sea hydrothermal vent sites along the East Pacific Rise, where it colonizes the walls of actively venting high-temperature chimneys. An abundant, morphologically diverse epibiotic microflora is associated with the worm's dorsal integument, with a highly integrated filamentous morphotype clearly dominating the microbial biomass. It has been suggested that this bacterial population participates in either the nutrition of the worm or in detoxification of the worm's immediate environment. The primary goal of this study was to phylogenetically characterize selected epibionts through the analysis of 16S rRNA gene sequences. Nucleic acids were extracted from bacteria collected from the dorsal surface of A. pompejana. 16S rRNA genes were amplified with universal bacterial primers by the PCR. These genes were subsequently cloned, and the resulting clone library was screened by restriction fragment length polymorphism analysis to identify distinct clone types. The restriction fragment length polymorphism analysis identified 32 different clone families in the library. Four of these families were clearly dominant, representing more than 65% of the library. Representatives from the four most abundant clone families were chosen for complete 16S rRNA gene sequencing and phylogenetic analysis. These gene sequences were analyzed by a variety of phylogenetic inference methods and found to be related to the newly established epsilon subdivision of the division Proteobacteria. Secondary structural model comparisons and comparisons of established signature base positions in the 16S rRNA confirmed the placement of the Alvinella clones in the epsilon subdivision of the Proteobacteria.

Microbiological evaluation of dressing procedures for crocodile carcases in Queensland

Microbiological testing of crocodiles during the dressing procedure has shown that sanitising the skin before skinning reduces the bacterial count on the skin and that dipping crocodile meat in 1.3% acetic acid solution effectively reduces bacterial levels. The total bacterial count on the processed mean sample was comparable with that obtained in the beef, pork and lamb industries. Salmonellae were isolated from 14 of the 72 carcases. Most (65%) of these isolates were in Salmonella subspecies III, formerly classified as Arizona.

Population sizes and frequency of Malassezia pachydermatis at skin and mucosal sites on healthy dogs

Skin and mucosal carriage of Malassezia pachydermatis was studied in 20 healthy pet dogs of various breeds and in 20 kennelled beagles. Using swabs, anal carriage was detected in 10 pet dogs and 11 beagles and the nose, mouth, prepuce and vulva were shown to be infrequently colonised. M pachydermatis was isolated from the external ear canal of 11 beagles and two pet dogs; both the population sizes and frequency of isolation were significantly (P < 0.05) greater in the beagles. The yeast was infrequently isolated from the axilla and groin in low numbers using contact plates and detergent scrub samples but was often cultured from the lower lip and the dorsal interdigital spaces; isolation frequencies and population sizes in the two groups of dogs were not significantly different. These results demonstrate that the anus, external ear canal and lip and interdigital skin of healthy dogs are frequently colonised by M pachydermatis.

Possible receptor for exfoliative toxins produced by Staphylococcus hyicus and Staphylococcus aureus

Exfoliative toxin produced by Staphylococcus hyicus bound to the GM4-like glycolipid extracted from the skin of 1-day-old chickens but did not bind to glycolipid from adult chickens or suckling mice. Exfoliative toxin produced by Staphylococcus aureus bound to the GM4-like glycolipid extracted from the skin of suckling mice but not to glycolipid from 1-day-old or adult chickens. S. hyicus and S. aureus exfoliative toxins lost their toxicity by preincubation with GM4-like glycolipid from 1-day-old chickens and suckling mice, respectively.

Change of central venous catheter dressings twice a week is superior to once a week in patients with haematological malignancies

Thirty-two consecutive patients with haematological disorders, in need of a permanent central venous catheter (CVC) were randomly allocated to have their CVC bandages (Tegaderm) changed once (OAW, n = 20) or twice (TAW, n = 19) a week. The two randomization arms were balanced in respect of age, sex, and underlying disease. The exit site of the CVC was inspected daily through the transparent bandage and erythema was noted. If severe erythema occurred, daily wet gauze dressings were applied. Samples for bacterial cultures were taken from the exit site of the CVC at every change of bandages. There was no difference in complications leading to removal of the CVC between the two groups (7/20 OAW vs. 7/19 TAW) or in CVC survival-time (P = 0.4). However, the OAW group had more positive CVC tip cultures (OAW 11/14 vs. TAW 2/9; P < 0.05) and a tendency to: (i) more extra dressings (P = 0.08); (ii) more cultures from the exit skin site showing high numbers of colony forming units (P = 0.07); (iii) shorter time to first exit site infection (P = 0.09); and (iv) more Gram-positive septicaemias (P = 0.08). Both clinical and bacteriological data in this study indicate that changing transparent polyurethane CVC bandages twice a week is superior to once a week.

In vitro modulation of keratinocyte-derived interleukin-1 alpha (IL-1 alpha) and peripheral blood mononuclear cell-derived IL-1 beta release in response to cutaneous commensal microorganisms

The ability of a range of skin commensal microorganisms to modulate interleukin-1 (IL-1) release by cultured human keratinocytes and peripheral blood mononuclear cells (PBMCs) was investigated by a combination of enzyme-linked immunosorbent assays and bioassays. Three fractions (formaldehyde-treated whole cells, culture supernatants, and cellular fractions) were prepared from Propionibacterium acnes, Propionibacterium granulosum, Staphylococcus epidermidis, Staphylococcus capitis, Staphylococcus hominis, and Malassezia furfur serovar B. The levels of immunochemical IL-1 alpha released by cultured keratinocytes during coincubations with these microbial fractions ranged from 0 to 136 pg/ml and were maximal after 72 h. No microbial fraction consistently upregulated immunochemical IL-1 alpha release by freshly isolated keratinocytes from two donors and a transformed cell line, all of which produced the cytokine constitutively to various extents. Bioassays revealed that most of the IL-1 released was biologically inactive. In contrast, whole cells of formaldehyde-treated P. granulosum and S. epidermidis significantly stimulated release of IL-1 beta by PBMCs from three donors compared with the negative control (culture medium). Release was maximal at 24 h. Coincubation with intact cells of the yeast M. furfur significantly decreased levels of IL-1 beta below the values for the negative control by PBMCs from all three donors. There was good correlation between bioassay data and immunoassay data for IL-1 beta, and the depressive effect of M. furfur cells on cytokine production by all three cultures of PBMCs was mirrored in the levels of bioactive cytokine. This reduction in IL-1 beta release by PBMCs by M. furfur may provide an explanation why dermatoses thought to be caused by this yeast are essentially noninflammatory or only mildly inflammatory.

Effect of type of defeathering system on Salmonella cross-contamination during commercial processing

The cross-contamination effects of three commercial defeathering systems were compared using turkeys from a single Salmonella-positive flock (< or = 15% cloacal-positive). Single or "common" flocks were used to control flock-to-flock variability. Thirty birds were mechanically defeathered in each system as the first flock of the day and compared with 30 hand-defeathered (control) birds. Three trials, each using a different common flock, were completed. In Trial 1, the incidence of Salmonella-positive birds decreased following mechanical defeathering at all three processors. The incidence of Salmonella-positive carcasses in test flocks increased following steam-spray (approximately 100%) and kosher (approximately 50%) defeathering in Trials 2 and 3, whereas no increase in Salmonella-positive carcasses resulted from conventional defeathering. The decrease in the number of Salmonella-positive birds as a result of defeathering observed in Trial 1, as compared to increases observed in Trials 2 and 3, may be related to the selection of feather-contaminated (Trial 1) vs intestinal-colonized (Trials 2 and 3) turkeys. Surface temperature of the carcasses and length of time required to defeather were monitored within each system. It is hypothesized that the increases in the number of Salmonella-positive birds following steam-spray and kosher defeathering in Trials 2 and 3 were a result of skin surface changes occurring during the defeathering process, which allowed increased adherence or entrapment of Salmonella spp. on or within remaining skin layers.

The role of defeathering in the contamination of turkey skin by Salmonella species and Listeria monocytogenes

This study was undertaken to determine whether the incidence of either Salmonella spp. or Listeria monocytogenes on turkeys at three commercial processors could be related to the type of defeathering system: 1) conventional, 58 C common bath scald; 2) kosher, 7 C common bath scald; or 3) steam-spray, 62 C nonimmersion scald. Flocks were sampled before defeathering, after defeathering, and after chill at each facility. The incidence of Salmonella-positive turkeys significantly increased subsequent to conventional defeathering (10 positive out of 14) as compared with before defeathering (3/14). The number of Salmonella-positive carcasses following kosher (0/14) and steam-spray (2/14) defeathering were similar to the number of Salmonella-positive carcasses found prior to defeathering (1/14 and 3/14, respectively). The incidence of Salmonella-positive carcasses following chill was slightly lower, but not significantly different than the number of Salmonella-positive carcasses found immediately following defeathering at all processors (8/14, 0/14, 1/14 for conventional, kosher, and steam-spray processors, respectively). Although L. monocytogenes was detected on turkeys sampled before chilling (2/10, kosher) and after chilling (8/14, kosher; 1/14, conventional), no L. monocytogenes was detected on turkeys at any of the processors prior to the evisceration process. Flocks with high aerobic plate counts prior to processing were more likely to contain Salmonella-positive birds throughout processing. Aerobic plate counts of all flocks were similar after chill whether or not Salmonella spp. and L. monocytogenes were detected.

Detection of Lyme disease spirochetes in the skin of naturally infected wild sika deer (Cervus nippon yesoensis) by PCR

We demonstrated the presence of Borrelia burgdorferi sensu lato DNA in the skin tissues of naturally infected wild sika deer, using PCR. The risk of transmission of B. burgdorferi sensu lato is recognized in sika deer.

Borrelia burgdorferi mutant lacking Osp: biological and immunological characterization

All Borrelia burgdorferi sensu lato isolates characterized to date have one or a combination of several major outer surface proteins (Osps). Mutants of B. burgdorferi lacking Osps were selected with polyclonal or monoclonal antibodies at a frequency of 10(-6) to 10(-5). One mutant that lacked OspA, -B, -C, and -D was further characterized. It was distinguished from the OspA+B+ cells by its (i) autoaggregation and slower growth rate, (ii) decreased plating efficiency on solid medium, (iii) serum and complement sensitivity, and (iv) diminished capacity to adhere to human umbilical vein endothelial cells. The Osp-less mutant was unable to evoke a detectable immune response after intradermal live cell immunization even though mutant survived in mouse skin for the same duration as wild-type cells. Polyclonal mouse serum raised against Osp-less cells inhibited growth of the mutant but not of wild-type cells, an indication that other antigens are present on the surface of the Osp-less mutant. Two types of monoclonal antibodies (MAbs) with growth-inhibiting properties for mutant cells were identified. The first type bound to a 13-kDa surface protein of B. burgdorferi sensu stricto and of B. afzelii. The MIC of the Fab fragment of one MAb of this type was 0.2 micrograms/ml. The second type of MAb to the Osp-less mutant did not bind to B. burgdorferi components by Western blotting (immunoblotting) but did not bind to unfixed, viable cells in immunofluorescence and growth inhibition assays. These studies revealed possible functions Osp proteins in borrelias, specifically serum resistance, and indicated that in the absence of Osp proteins, other antigens are expressed or become accessible at the cell surface.